Continuing Education Activity

This activity reviews the indications and contraindications of intra-aortic balloon pump in patients with cardiogenic shock secondary to various cardiac conditions, including myocardial infarction and subsequent mechanical complications. It covers the structure of the IABP device and its hemodynamic effects, the complications related to IABP use, and, most importantly, how an interprofessional team approach in caring for patients with cardiogenic shock requiring IABP support can help improve the clinical outcomes.

Objectives:

• Review the anatomic and physiologic effects of the intra-aortic balloon pump.
• Review the indications for the intra-aortic balloon pump procedure.
• Review the technique of intraaortic balloon pump placement.
• Outline strategies for interprofessional communication to help make timely decisions about escalation or deescalation of care consistent with the patient's goals of care and the long-term prognosis with an intra-aortic balloon pump.

Introduction

Patients with the clinical and biochemical signs and symptoms of hypoperfusion secondary to cardiac failure or cardiac arrest carry high short-term mortality.[1] Various mechanical circulatory devices have been developed to mitigate the adverse outcomes of cardiogenic shock until treating the underlying cause. To date, four types of mechanical circulatory support devices exist that include Intra-aortic balloon pump (IABP), non-IABP ventricular circulatory assist devices, extracorporeal membrane oxygenation devices, and non-percutaneous ventricular assist devices. Intra-aortic balloon pump is the simplest, cost-effective, easy to implant and explant in the coronary catheterization laboratory by an interventional cardiologist and can effectively be managed in an intensive care unit by an intensivist.[2] Although IABP has a modest hemodynamic beneficial effect compared with novel, advanced mechanical circulatory support devices, it has a better safety profile, relative simplicity to use, and the beneficial cardiovascular physiological impact. These features make IABP a frequently used circulatory support device in patients requiring hemodynamic support either in cardiogenic shock or at risk of hemodynamic decompensation during a high-risk coronary intervention. However, currently available evidence related to the use of IABP is in constant flux. Therefore, it is important to review the safety and efficacy of IABP in various clinical conditions and appraise the health care providers of current evidence-based literature related to IABP. This article reviews the physiological and hemodynamic effects of IABP on the cardiovascular system as well as the safety and efficacy of its use in various cardiovascular clinical conditions.

Anatomy and Physiology

Anatomic, Physiologic, and Hemodynamic Effects of IABP

The IABP assists the heart indirectly by decreasing the afterload and augments diastolic aortic pressure with subsequent enhancement in diastolic blood flow resulting in better perfusion of the peripheral organ as well as a possible improvement in the coronary blood flow. The intra-aortic balloon inflates during diastole synchronously with aortic valve closure and the appearance of a dicrotic notch resulting in the displacement of blood from the thoracic aorta into the peripheral circulation that is followed by rapid deflation before the onset of systole phase of the cardiac cycle. Theoretically, this results in improved diastolic pressure and reduced systolic aortic pressure by reducing the afterload, which subsequently results in decreased left ventricle wall stress reducing the myocardial oxygen demand. These hemodynamic changes improve the cardiac output by increasing stroke volume, particularly in patients with reduced left ventricular function.

Stefanadis et al. demonstrated a 30% increase in aortic distensibility with IABP, thereby reducing the aortic stiffness constant, resulting in a 24% increase in cardiac index and a 31% reduction in myocardial oxygen demand.[3] In patients with systolic heart failure, IABP improves ventriculoarterial coupling ratio and consequently enhances stroke volume by reducing peripheral arterial elasticity without affecting the left ventricular end-systolic elastance. In these patients with low output, a reduction of end-systolic pressures, end-diastolic pressure, and volume of the left ventricle with IABP result in a leftward shift of pressure-volume loop with a reduced pressure-volume loop area suggesting a decrease myocardial oxygen demand.[4] 

IABP use may also help patients with acute right ventricular failure by reducing the right ventricular afterload by decreasing pulmonary artery pressure and left ventricular end-systolic and end-diastolic pressures and, as a result, improves the cardiac output.[5][6]

Various studies performed in the past studying effect of IABP on coronary blood flow provided contradictory results.[7][8] Zehetgruber et al. observed enhanced coronary blood flow in patients supported by counterpulsation likely secondary to increased diastolic aortic pressure as a result of IABP, and the effect was more pronounced in patients with compromised hemodynamic status as compared to those with the stable hemodynamic condition.[9] It is important to note that IABP use in patients with coronary artery stenosis did not result in any significant increase in arterial blood flow in post-stenotic coronary artery territory unless reperfused via thrombolysis or percutaneous coronary intervention.[10] This observation partially explains the mortality benefit observed in earlier studies in patients with cardiogenic shock secondary to acute myocardial infarction (AMI) when IABP was used concomitant with PCI or thrombolysis. A possible mechanism contributing to augmented coronary blood flow with IABP use is the result of an increased diastolic aortic pressure with pulsatile balloon inflation during the diastolic phase and, also, endothelial-derived nitric oxide release from vascular stretch results in diastolic arteriolar vasodilation. However, the vasodilatory effect observed secondary to NO release was more pronounced in the small arterioles as compared to larger arterioles.[11] To summarize, patients with ischemic myocardium derive a greater benefit from counterpulsation by systolic unloading and thereby reducing the oxygen demand rather than a significant improvement in coronary blood flow.

Pfluecke et al. demonstrated a positive hemodynamic effect of intra-aortic balloon pump on cerebral blood flow in patients with acute heart failure exacerbation. They studied the impact of IABP on middle cerebral artery transcranial Doppler flow (TCD) velocity change and velocity time integral changes in 2 groups of patients; patients with acute heart failure with a left ventricular ejection fraction of less than 30% (group 1) and the other group of patients with a left ventricular ejection fraction of more than 30% (group 2), and compared the effect on blood flow velocity with the baseline measurements taken without an IABP. Although both groups of patients showed an increased cerebral blood flow with IABP, a significantly higher increase in middle cerebral artery blood flow was observed in patients with a left ventricular ejection fraction of less than 30% as compared with patients with an ejection fraction of more than 30% [the velocity time integral changes (VTI change) of 20.9% +- 3.9% in LVEF <30% VS 10.5% +- 2.2% in LVEF >30%, P <0.05]. However, researchers noted a minimal increase in the mean arterial pressure in both groups with IABP augmentation.[12] Yang F et al. studied the impact of IABP on cerebral blood flow in postcardiotomy (coronary artery bypass graft, CABG) cardiogenic shock patients requiring extracorporeal membrane oxygenation (ECMO) support. They observed an enhancement in mean cerebral blood flow in those patients who had a baseline cardiac function with a pulsatile pressure of more than 10 mm Hg (261.68 +/- 82.45 ml/min in IABP plus ECMO vs. 244.43 +/- 45.85 ml/min in ECMO alone group, P=0.00). However, in postcardiotomy cardiogenic shock patients with cardiac stunning and a pulsatile pressure less than 10 mm Hg, the addition of IABP on ECMO support resulted in a reduced mean cerebral blood flow as compared to patients on ECMO alone (239.47 +/- 95.60 ml/min in IABP plus ECMO vs. 257.68 +/- 97.21 ml/min in ECMO, P=0.00). It appears that the pulsatile blood flow augmented by IABP in a patient having some baseline cardiac contractility helps improve the velocity of blood flow in the cerebral artery as seen in the above studies; however, more robust studies are needed to identify the clinical benefit of improved cerebral blood flow in patients with cardiogenic shock.[13]

Indications

Indication for placement include:

• Acute congestive heart failure exacerbation with hypotension
• As prophylaxis or adjunct treatment in high risk percutaneous coronary intervention
• Myocardial infarction with decreased left ventricular function leading to hypotension
• Myocardial infarction with mechanical complications causing cardiogenic shock, i.e., acute mitral regurgitation due to papillary muscle rupture or ventricular septal rupture
• Low cardiac output state after coronary artery bypass grafting surgery
• As a bridge to definitive treatment in patients with any of the following conditions; intractable angina or myocardial ischemia, refractory heart failure, or intractable ventricular arrhythmias

Contraindications

Contraindications to intra-aortic balloon pump include:

• Uncontrolled sepsis
• Uncontrolled bleeding diathesis
• Moderate to severe aortic regurgitation
• An aortic aneurysm or aortic dissection
• Severe peripheral artery disease unless pretreated with stenting

Equipment

To insert the intra-aortic balloon, pump the equipment required includes but not limited to:

• Intra-aortic balloon pump kit: That includes an intra-aortic balloon pump system with an IABP catheter, arterial dilator, a guidewire, angiographic needle.
• Surgical mask with sterile gloves and gowns
• Sterile drapes
• 1% lidocaine solution
• Sterile prep solution that includes povidone-iodine or hexachlorophene on chlorhexidine with alcohol
• 25-gauge needle
• 5 cc syringe
• Scalpel handle with a blade
• Sterile saline and lubricant
• Sterile transparent tape and dressing
• Tissue clamp
• 2-0 silk suture
• Safety razor
• 0.035 J guidewire
• Fluoroscopy device

Prior to the insertion of IABP, informed consent is necessary with a clear explanation of the risks and benefits of IABP insertion.

Personnel

The provision of care of patients who require an intra-aortic balloon pump is in the ICU setting under continuous cardiac monitoring and arterial line care and management. Healthcare providers must be accredited in IABP insertion and management and identify the earlier signs of malfunctioning or the complications related to the device and manage them as per recommended protocols. An interprofessional team is required to provide best-integrated care, and the team may include an interventional cardiologist, intensivist, accredited intensive care or coronary care unit nurse, and or cardiothoracic surgery team, depending on whether the patient has a primary cardiac surgical illness.

Preparation

Before insertion of IABP, informed consent is necessary, with a clear explanation of the risks and benefits of IABP device insertion, with concise instructions about post-procedure care. These instructions include not to flex the leg if femoral artery access of that leg was the entry point for IABP insertion and inability to walk till the device is in place in case of femoral artery access used for device insertion.

Before the procedure, the patient requires a thorough evaluation for any bleeding diathesis, infection, and presence of severe peripheral arterial disease.

The patient is positioned supine, and adherence to the sterile technique should be practiced to insert the device.

Technique or Treatment

After the implementation of sterile techniques to prepare the femoral catheterization site and application of local anesthesia, the angiographic needle is inserted into the common femoral artery below the inguinal ligament at an angle of 45 degrees or less. The fluoroscopic device can be used to ensure the location of an angiographic needle into the common femoral artery as the arterial puncture above the inguinal ligament is strongly associated with retroperitoneal hemorrhage, and arterial puncture at or below the femoral artery bifurcation is associated with acute limb ischemia. After ensuring adequate placement of the radiographic needle, the J-tip of 0.035" guidewire gets inserted and advanced through the angiographic needle into the femoral artery. The angiographic needle is removed over the guidewire while keeping the guidewire in place. A small incision with the help of the blade is made in the skin at the site of insertion of the guidewire to facilitate insertion of the sheath introducer. With the help of an introducer dilator to be inserted over the guidewire and advanced it in a rotary fashion into the femoral artery, the sheath tract can further be prepared to facilitate the insertion of the introducer sheath into the artery. The introducer sheath gets placed over the guidewire, and then 0.035 guidewire is removed while leaving the introducer sheath in the arterial lumen. It is followed by the insertion of a J-tube of the 0.018" guidewire (IABP guide wire) through the introducer sheath and advanced into the thoracic aorta.

The IABP catheter is prepared for insertion. Balloon preparation is by establishing a vacuum with the help of a syringe by applying aspiration, and the central catheter lumen is flushed with sterile saline to ensure patency. The IABP catheter is inserted and advanced over the 0.018" guidewire to the proper positioning of the balloon in the aorta. The location of the intra-aortic balloon with its tip lying distal to the left subclavian artery and the proximal portion ending above the origin of renal arteries is considered as the ‘safe zone,’ and the confirmation of position can be by chest x-ray or fluoroscopy. Following guidewire removal, and the central lumen of the catheter is flushed and connected to the transducer to measure intra-aortic pressure. The IABP catheter gets connected to the extender catheter, which then connects to the IABP console.[14]

Complications

The Benchmark Registry reports an incidence of 2.6% for major complications (major complications include severe limb ischemia, severe bleeding, balloon leak, or death due to IABP insertion or failure) with 21.2% in-hospital mortality, and only 0.05 % of in-hospital mortality was directly attributable to IABP.[15]

Complications of the IABP in 5495 patients with acute myocardial infarction reported in the Benchmark registry are:[16]

All Complications 8.1%

• Major complication 2.7%
• Minor complication 5.4%

Bleeding Complication

• Any access site bleeding 4.3%
• Severe access site bleeding 1.4%
• Transfusion 1.4%

Vascular Complications and Limb Ischemia

• Any limb ischemia 2.3%
• Visceral ischemia 0.1%
• Major limb ischemia (loss of pulse, loss of sensation, or abnormal temperature or pallor limb necessitating intervention, arterial repair or amputation) 0.5%
• Amputation 0.1%
• Vascular surgery 0.7%
• Deep venous thrombosis 0.1%
• Superficial vein thrombosis 0.1%

Infection 0.1%

Stroke 0.1%

IABP Related Mortality 0.05%

Others

• IABP leak 0.8%
• Poor inflation 0.6%
• Difficult insertion of IABP 0.1%
• Poor augmentation 1.1%

Independent risk factors for major complications identified in the Benchmark Registry were female gender, peripheral vascular disease, body surface area less than 1.65 m, and age greater than or equal to 75 years. However, additional risk factors leading to ischemic vascular complications are the duration of IABP support, catheter size, diabetes, and cardiac index less than 2.2 L/min/m. Diabetes and hypertension are known risk factors of developing peripheral arterial disease and may indirectly predispose to risk of vascular complication due to a higher prevalence of PAD in this group of patients.[17][18][19][20]

In the IABP SHOCK II Trial, researchers observed no significantly higher risk of complication in the IABP group as compared with the control group.

Various complication observed in IABP vs control group are as follows:

• Major bleeding risk (3.3 % in IABP group vs 4.4 % in control group, p value = 0.51)
• Peripheral ischemia complications (3.3 % in IABP group vs 4.4 % in control group, p value = 0.51)
• Sepsis (3.3 % in IABP group vs 4.4 % in control group, p value = 0.51)
• Stroke (0.7% in IABP vs 1.7% in control, P = 0.28)

Clinical Significance

Intra-Aortic Balloon Pump in Acute Myocardial Infarction

American College of Cardiology/American Heart Association (ACC/AHA) 2013 guidelines of ST-elevation myocardial infarction provides class IIa (level of evidence: B) recommendation to use IABP in patients with acute myocardial infarction complicated by cardiogenic shock as a temporary stabilizing measure in those not able to quickly achieve hemodynamic stability with pharmacologic treatment. However, alternative mechanical assist devices may be used (class IIb- the level of evidence C) in these patient groups with refractory cardiogenic shock.[21] 2108 European Society of Cardiology and the European Association of Cardiothoracic Surgery guidelines on myocardial revascularization do not recommend routine use of IABP in patients with cardiogenic shock due to ACS. However, short-term mechanical circulatory (MCS) support may be considered in patients with refractory cardiogenic shock complicating acute coronary syndrome, but the patient's age, comorbidities, neurological function, and the prospects for long-term survival and quality of life should be taken into consideration while making the decision about short-term MCS.[22] Class IIa recommendation of ESC/EACTS 2014 guidelines recommends IABP insertion should be considered in patients with hemodynamic instability or cardiogenic shock due to mechanical complications and should be followed immediately by repair of the defect. And Class IIb recommendation for short-term mechanical circulatory support in ACS patients with cardiogenic shock may be considered.[23]

Cardiogenic shock (CS) is the leading cause of in-hospital mortality in patients hospitalized with the acute coronary syndrome (ACS). Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK) Trial Registry reports predominant left ventricular failure (78.5%) as the most common cause of CS in ACS; however, 12 % of patients suffered CS secondary to mechanical complications, i.e., ventricular septal defect, mitral regurgitation, or cardiac tamponade.[24] SHOCK Trial and SHOCK Registry revealed that early revascularization with percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) has a significant survival benefit in patients with acute coronary syndrome complicated by CS.[24][25] SHOCK Registry reported a better in-hospital mortality outcome in the patient treated with thrombolysis and IABP vs. thrombolysis alone, i.e., 46.5% vs. 62.9%, P < .005. However, the revascularization rate was significantly variable between the two groups, i.e., only 20% in the thrombolytic group as compared to 68% (p-value < 0.001) in thrombolytic with IABP group, and most likely, this difference in revascularization has significantly influenced the difference in the in-hospital mortality between the two groups.[26] In this registry, those patients with post-MI-CS with left ventricular failure in those institutions with no access to PTCA/CABG had a better outcome in terms of lower in-hospital mortality if these patients received initial treatment with early thrombolytic therapy supported by IABP followed by transfer to the PCI/CABG equipped facility to receive early revascularization.

National Registry of myocardial infarction 2 also endorsed the findings of the SHOCK registry, suggesting that implementation of IABP as an adjunct to thrombolytic therapy has a mortality benefit in post-MI cardiogenic shock patients (mortality of 49% in thrombolysis plus IABP versus 65% in the control group without IABP); however, researchers observed no mortality benefit in patients treated with primary angioplasty.[27] The mortality rate for patients treated with primary PTCA was lowest, i.e., 42%; but a slightly higher death rate of 47% was observed when combining primary PTCA with IABP. It is important to be careful in interpreting the information from this registry data because of a lack of randomization of the patient and selection bias, and other confounding factors, which pose a serious risk of bias.

To further delineate the role of IABP in patients with post-MI-CS, the subsequent clinical trial of Thrombolysis and Counterpulsation to Improve Cardiogenic Shock Survival (TACTICS), however, showed no overall mortality benefit at six months for patients treated with thrombolysis supported with IABP as compared with unsupported thrombolysis.[28] But it is important to notice a trend of better 6-month mortality outcome in CS patients with Killip class III and IV treated with combination therapy of fibrinolysis with IABP support as compared to fibrinolytic alone treatment (39% vs. 80%, p-value = 0.05).

In October 2012, IABP-SHOCK II Randomized open-label trial compared IABP therapy with no IABP therapy in patients with cardiogenic shock complicating AMI who underwent early revascularization therapy in addition to standard medical treatment, and it showed no difference in the 30-day mortality.[29] In this trial, 300 patients in the IABP group and 298 patients in the control group completed the study, and at 30 days, 39.7% of patients died in the IABP group vs. 41.3% patients in the control group (i.e., without IABP), relative risk (RR) with IABP was 0.96; 95% confidence interval, 0.79 to 1.17; P=0.69. Moreover, IABP did not demonstrate any positive effect in terms of time to achieve hemodynamic stability, length of intensive care unit stay, peripheral tissue/organ perfusion as measured by serum lactic acid levels, the dose of catecholamine required to maintained adequate organ perfusion.

In 2013, Thiele H et al. reported an analysis of 12 months to follow up results of IABP-SHOCK II Randomized open-label trial to assess for any mortality benefit at an extended period after AMI.[30] Out of 600 patients who participated in the trial, 595 patients completed 12 months follow-up, and 155 out of 299 patients (52%) in the IABP group died compared to 152 out of 296 (51%) in the control group. There was no difference in the primary endpoint of mortality at 30 days, 6, and 12 months. Moreover, no difference in the secondary endpoints, i.e., the incidence of bleeding, infection, re-infarction, revascularization, and stroke, were observed between the intervention and control groups who received early revascularization therapy. Before the IABP-SHOCK II clinical trial, in 2009, a meta-analysis by Sjauw KD et al. challenged the recommendations of ESC related to IABP use in post-AMI-CS based on lack of sufficient evidence showing a benefit of IABP in cardiogenic shock.[31] Later on, the results of the IABP-SHOCK II trial showing no clear mortality benefit lead to downgrading the recommendations of IABP use in post-AMI-CS.

A significant decline in the use of IABP has been reported in a study by Tomassini et al. (years 2003 till 2013) and Patel et al. (years 1998 till 2008) that may be attributable to a higher success rate of percutaneous coronary intervention (PCI) procedure and advancement in the guideline-directed treatment strategies.[32][33] Nevertheless, 2013 ACC/AHA guidelines recommend (class IIa) the use of IABP in patients with ST-elevation myocardial infarction complicated by cardiogenic shock not stabilized with appropriate pharmacological treatment.[21]

Recently published long-term 6-year follow-up of IABP-SHOCK II Trial revealed no beneficial effect on all-cause mortality. Unfortunately, a higher mortality rate of 2 out of 3 patients with cardiogenic shock is observed despite receiving treatment with revascularization therapy. Moreover, no difference in recurrent MI or repeat revascularization, stroke, or re-hospitalization due to cardiac etiology, quality of life among survival (assessed by EuroQol 5D Questionnaire and New York Heart Association class) was observed.[34] The currently available evidence suggests no short-term or long-term clinical benefit of IABP in patients with post-AMI cardiogenic shock without mechanical defects and endorses the recommendations of European Society of Cardiology to avoid the routine use of the IABP.

To elucidate whether IABP has a beneficial role when used as an adjunct to extracorporeal membrane oxygenation (ECMO) in patients with cardiogenic shock complicated by respiratory distress, Cheng et al. in 2015, conducted a systemic review with a meta-analysis of 16 observational studies with 1517 patients. This analysis did not demonstrate any dramatic improvement in survival to hospital discharge in patients with cardiogenic shock secondary to AMI, or postcardiotomy cardiogenic shock, or in those with cardiac arrest, who were treated with IABP as an adjunct to extracorporeal membrane oxygenation (ECMO) compared to those treated with ECMO alone.[35] Later on, in 2018, Yongnan Li et al. performed a meta-analysis including 29 retrospective observational studies (4576 patients) showed reduced in-hospital mortality in patient groups who received treatment with ECMO combined with IABP as compared to those treated with ECMO alone [risk ratio (RR) 0.90; 95% confidence interval 0.85-0.95; p < 0.0001].[36] This study reported a pooled in-hospital mortality of 1339/2291 (58.4% deaths) in patients treated with VA-ECMO plus IABP vs. 1441/2285 (63.1% deaths) in a group of patients treated with VA-ECMO alone. The meta-analysis reporting these outcomes included the observational studies, that carry the potential risk of selection bias and other biases inherent with observational studies. Moreover, differences in inter-center practice protocols, a wide variation in indications to initiate ECMO treatment in different studies included in the analysis, and having no clear details regarding demographics of the patients refrain from generalizing the results of this analysis to patients with cardiogenic shock due to various etiologies. Further prospective studies are needed to elucidate any beneficial impact of IABP use in patients with severe refractory cardiogenic shock requiring ECMO as currently available evidence is of low quality and offers conflicting results.

Comparison of IABP Therapy with New Advanced Percutaneous Mechanic Circulatory Device (pMCS) in Cardiogenic Shock

In 2008, Seyfarth M et al. studied 25 patients with post-AMI CS and reported that earlier implantation of an advanced percutaneous mechanical circulatory device (PMCs) in post-AMI CS patients is feasible and safe and provides superior hemodynamic support (cardiac index) compared with the standard IABP support with medical treatment (delta cardiac index in left-side heart pump systems patients 0.49 +/- 0.46 l/min/m vs. delta CI in IABP = 0.11 +/- 0.31 l/min/ m; p = 0.02).[37] However, no difference in mortality was observed between the two groups (30-day mortality was 46% in both groups).

To determine whether the new advance percutaneous mechanical circulatory device (pMCS) has a better clinical outcome compared to IABP in patients with severe cardiogenic shock secondary to acute myocardial infarction requiring mechanical ventilation, Dagmar M. Ouweneel et al. in 2016, performed a multicenter, randomized, prospective, clinical trial (IMPRESS trial).[38] This clinical trial demonstrated no difference in mortality between two group at 30 days (mortality of 46% in  left-side heart pump systems vs 50% in IABP, a hazard ratio with  left-side heart pump systems of 0.96, 95% confidence interval: 0.42 to 2.18; p = 0.92) and 6 months (both groups had 50% mortality, hazard ratio: 1.04; 95% confidence interval: 0.47 to 2.32; p = 0.923). This trial included 48 patients with severe CS complicating MI, and 100% of the patients in both groups required mechanical ventilation. It is noteworthy to report that 92% of the patients in this study had post-cardiac arrest resuscitation performed, resulting in the return of spontaneous circulation (ROSC) but continued to have the shock. This study is unique in that it examined a very sick population with CS post-MI, all requiring mechanical ventilation and catecholamine support. 79% of patients in the pMCS treatment group received therapeutic hypothermia compared to 71% of patients in the IABP group. Although no survival benefit was observed in both treatment groups, a higher bleeding complication rate of 33% was observed in patients treated with pMCS device as compared to 8% in the IABP treatment group, p-value =0.06. Similarly, registries comparing left-side heart pump systems with IABP in post-resuscitation shock patients described no difference in survival rate between left-side heart pump systems treated and IABP treated patients, i.e., 23.0% vs. 29.5%, respectively, p =0.61; however, a higher bleeding complication rate of 26% was observed in the left-side heart pump systems treatment group as compared to 9% in IABP treated patients, p=0.06.[39]

Thiele H et al. in 2017 Performed a meta-analysis of 4 randomized clinical trials aimed to investigate the efficacy and safety of percutaneous mechanical circulatory support devices in comparison to IABP in patients with cardiogenic shock.[40] Although active MCS demonstrated beneficial effects on mean arterial pressure, peripheral perfusion as measured by serum lactate, and pulmonary capillary wedge pressure but no significant difference in 30-day mortality was observed. All clinical trials, however, reported a significantly higher incidence of bleeding from vascular access sites and limb ischemia in the active MCS group.

Role of IABP in High-Risk PCI

The application of IABP during the high-risk PCI in both stable and unstable patients was initially advocated based upon the low-quality evidence derived from the observational studies conducted by Mishra et al. and Briguori et al.[41][42] However, subsequent randomized clinical trials did not demonstrate any difference in the in-hospital mortality, major adverse cardiac and cerebrovascular events between the patients undergoing high-risk PCI with or without the support of IABP.

The randomized controlled clinical trial of Balloon Pump-Assisted Coronary Intervention Study (BCIS-1) evaluated the elective use of IABP during high risk percutaneous coronary intervention in patients with severe coronary artery disease (Jeopardy score equal or more than 8/12, when maximum possible score is 12) having compromised left ventricular function (ejection fraction under 30%).[43][44] There was no difference demonstrated in the primary outcome of major cardiac and cerebrovascular events at hospital discharge (capped at 28 days) between the two groups (15.2 and 16.0 percent respectively; odds ratio 0.94, 95% CI 0.51-1.76). However, rescue IABP support was necessary for 12 % of those patients who underwent PCI without elective IAPB insertion, which highlights its importance as a standby strategy when performing high-risk PCI. A trend of lower all-cause mortality was observed in IABP supported PCI group as compared to PCI alone group at six months [4.6% and 7.4%, respectively, p = 0.32; OR, 0.61; 95% CI, 0.24-1.62], but it was not statistically significant. Later on, at a median follow-up of 51 months (interquartile range of 41-58), a statistically significant lower long-term all-cause mortality was observed in IABP supported PCI group (n= 42) as compared to those receiving PCI without IABP (n=58). All-cause mortality was 28 versus 39 percent, hazard ratio of 0.66; confidence interval 0.44-0.98, p = 0.039), and a 34% lower relative risk reduction in all-cause mortality was observed in IABP supported PCI group compared with unsupported PCI group.

It merits noting that the major procedural complications rate was lower in IABP supported group vs non-IABP –PCI group (1.3% vs 10.7%, P < .001; OR, 0.11 [95% CI, 0.01-0.49]). Bleeding complications including major or minor bleed occurred in 19.2% and 11.3% (P = .06; OR, 1.86 [95% CI, 0.93-3.79]) and access-site complications occurred in 3.3% and 0% (P = .06) of the elective IABP and no planned IABP groups, respectively.

Later on, a meta-analysis of 11 studies comparing the outcome of prophylactic IABP implementation during high-risk PCI with patients undergoing PCI without IABP suggested no benefit in terms of major adverse cardiovascular events and in-hospital mortality.[45] Furthermore, no difference was observed between the two groups in terms of access site vascular complications and stroke risk. However, this analysis carries a potential risk of bias due to the inclusion of observational studies in addition to a randomized clinical trial in the meta-analysis.

The new mechanical circulatory support devices (MCS) are known to provide better hemodynamic support than IABP in patients with compromised left ventricular function. To further evaluate the clinical outcomes of MCS implementation during high-risk PCI, Dangas et al. conducted PROTECT II clinical trial and compared the clinical outcomes of intra-aortic balloon pump with a left-side heart pump system in patients undergoing non-emergent high risk percutaneous coronary intervention.[46] This trial randomized patients undergoing high-risk PCI either to an IABP (n= 211) or left ventricular assist device left-side heart pump systems (n= 216). The major adverse events (MAE) and major adverse cardiac and cerebrovascular events (MACCE = death, stroke, myocardial infarction, and repeat revascularization) assessed at 90 days were significantly lower in the left-side heart pump systems group compared with the IABP group (MAE, 37% vs. 49%, p = 0.014 respectively; MACCE, 22% vs. 31%, p= 0.034 respectively). Multivariate analysis further supported these findings. No difference in mortality and sizeable myocardial infarction was observed between the two groups at 3 months follow-up interval. The improved 90 days of survival in the left-side heart pump systems group was attributed to better hemodynamic support offered by left-side heart pump systems compared to IABP during the high-risk PCI.

Based on the evidence available, IABP use is not routinely recommended in hemodynamically stable patients with severe left ventricular dysfunction and extensive coronary artery disease undergoing high-risk PCI unless the patient is hemodynamically unstable or deemed to be at high risk of becoming unstable during the PCI. Also, if feasible, the hemodynamic support with a left-side heart pump system provides a better clinical outcome than IABP in high-risk patients undergoing PCI as suggested by PROTECT II clinical trial.

Intra-Aortic Balloon Pump in Chronic Systolic Heart Failure Patients with Cardiogenic Shock

Patients with chronic heart failure with accompanying reduced ejection fraction awaiting definitive therapy, i.e., heart transplantation or percutaneous left ventricular assist device (LVAD), may benefit from IABP counterpulsation as a bridge therapy.

The Acute Decompensated Heart Failure Syndrome (ATTEND) Registry demonstrated a very low utility of IABP (2.5 %) in patients with acutely decompensated heart failure (ADHF) without acute coronary syndrome.[47] Very limited evidence is available to comment on the impact of the implementation of IABP in patients with acute on chronic heart failure. However, patients with hemodynamic instability, defined as hypotension, decreased pulse pressure, third heart sound, cool extremities, and reduced left ventricular function, may benefit from IABP as a short-term bridging therapy waiting for recovery or destination therapy. More studies are needed to identify the target patients who may benefit from IABP therapy, and specific clinical criteria are necessary to guide physicians in deciding to initiate IABP support; rather, it is entirely based on the clinical judgment of heart failure specialist physician.

Sintek et al. retrospectively studied patients with chronic systolic heart failure complicated by cardiogenic shock requiring IABP as a bridge therapy to left ventricular assist devices (LVAD) and identified baseline right and left ventricular cardiac power indexes as the clinical predictors to achieve hemodynamic stability with IABP.[48] More than half of the patients achieved hemodynamic stabilization with IABP, but the patients who decompensated after IABP were able to achieve similar hemodynamic improvements, however, at the expense of increased vasopressor and inotropic support. Most importantly, the clinical decompensation after IABP indicated a worse outcome even after the implantation of LVAD in terms of a threefold higher length of intensive care stay and a five-fold increase in mechanical ventilation time (p-value < 0.01). Therefore, it is important to identify those patients who may not benefit from IABP implementation and require an early LVAD implantation. Further studies are needed to devise stringent clinical criteria to specify patients who may benefit from either IABP or early LVAD use to stabilize them hemodynamically. 

Having relatively less complication rate and ease of IABP use with a better mortality outcome observed in patients with heart failure with cardiogenic shock encourage frequent use of IABP during earlier resuscitation period as a bridge to definitive therapy, especially when increasing dose of inotropic support is warranted. However, the clinical criteria specifying the target patient population who will benefit the most and criteria to help wean off the IABP is needed.

Use of IABP in Medical Refractory Ventricular Arrhythmias

The ventricular arrhythmias are more frequent in patients with ischemic cardiomyopathy with reduced left ventricular ejection fraction. Limited available evidence[49] supports the use of IABP in patients with reduced left ventricular ejection fraction having medical refractory ventricular arrhythmias leading to hemodynamic instability. And it helps provide the time to institute a definitive treatment, including arrhythmia focus ablation, a permanent ventricular assist device, or cardiac transplantation. The efficacy of IABP is dependent on the timing of balloon inflation and deflation relative to the cardiac cycle; therefore, controlling the timing of interbeat IABP inflation during both regular rhythm and arrhythmias by application of Real-time dicrotic notch detection algorithm ensures the efficacy of IABP in either condition.[50][51][50] 

Use of IABP in Mechanical Complications of Myocardial Infarction

IABP is commonly used as a bridge therapy to lend time for definitive surgical treatment for patients with hemodynamic instability secondary to acute mitral valve regurgitation or interventricular septum perforation due to acute myocardial infarction.[52] Moreover, patients with severe critical aortic stenosis awaiting surgery may benefit from IABP to maintain hemodynamic stability.

Use of IABP During Cardiac Surgery

Between years 2005-2014, use of MCS devices is observed in approximately 50% of cardiac surgery patients complicated by postoperative cardiogenic shock; however, a linear decrease in the use of MCS devices, predominantly due to decreased utilization of IABP despite an increase in other MCS devices use is observed during the same period. (DOI: 10.1016/S0735-1097(18)31225-7)

Patients with difficulty to wean from cardiopulmonary bypass support after coronary artery bypass graft surgery benefit from IABP to assist early weaning from the artificial cardiopulmonary support.

A meta-analysis, including 23 studies (7 randomized control trials and 16 observation studies) with a total of 9212 patients, performed by Deppe et al. showed an absolute risk reduction in mortality of 4.4% (Odds ratio 0.43; 95% confidence interval 0.25–0.73; p = 0.0025) when IABP is used preoperatively in high-risk patients prior to coronary artery bypass graft surgery.[53] Also, a decrease in risk of myocardial infarction, cerebrovascular event, renal failure, length of ICU stay, and length of hospital stay was observed when preoperative IABP was used. Similar mortality benefit with preoperative IABP use was observed in a retrospective single-center study on a patient with severely reduced left ventricular function undergoing off-pump coronary artery bypass grafting.

In 2013 a randomized controlled trial (RCT) by Ranucci et al. demonstrated no mortality or morbidity benefit of preoperative IABP use in hemodynamically stable coronary artery disease patients with reduced left ventricular ejection fraction of less than 35% undergoing coronary artery bypass surgery.[54] Furthermore, a recent single-center randomized control trial (published in 2018) conducted by Rocha et al. evaluated the outcome of perioperative intra-aortic balloon pump use in high-risk cardiac surgery patients and demonstrated no mortality benefit in the IABP group.[55] A meta-analysis of 11 randomized controlled trials by Rocha et al. that included the results of the recent clinical trial by Rocha et al. endorse the findings mentioned above of lack of survival benefit with the utilization of perioperative IABP in high-risk surgery patients. 

Although the available literature to date suggested in favor of perioperative IABP utilization in terms of mortality and morbidity; however, emerging high-quality evidence in the form of RCTs and the meta-analysis that includes only RCTs is contradicting the mortality and morbidity benefit of perioperative IABP use. 

Enhancing Healthcare Team Outcomes

Although IABP has a less significant impact on the hemodynamic improvement, its physiological effect of offloading the left ventricle during active ischemic heart disease, especially in hypotensive patients with reduced cardiac output, results in decreased myocardial oxygen demand, and thus, indirectly assist compromised left ventricle to enhance the cardiac output. New short-term mechanical circulatory support devices demonstrate significantly improved hemodynamic support as compared with IABP. However, studies observed no mortality benefit, and a higher rate of bleeding and incidence of an ischemic limb is noted with these new MCS devices compared with IABP. Although the use of IABP is declining over time; nevertheless, IABP is still the most widely used cardiac assist device encompassing a wide array of indications ranging from prophylactic use during high-risk percutaneous or surgical intervention to the cardiogenic shock needing hemodynamic stabilization. Despite its widespread use in various clinical conditions, except for the guidelines available for the utility of IABP in ST-segment elevation MI, there are no specific guidelines by the American College of Cardiology/American Heart Association available to guide initiation of IABP in various other clinical conditions. Further studies are warranted to devise stringent criteria and protocol to assist physicians in decision-making related to the timing of initiation and weaning of IABP and to identify the patient group with cardiogenic shock who will benefit the most from IABP therapy.

Cardiogenic shock is a time-sensitive clinical condition that carries a high early mortality rate despite the implementation of advanced treatment strategies, including the early use of percutaneous coronary intervention, medical therapy, hemodynamic support with medications, and mechanical support devices.[56] Early diagnosis and application of interprofessional collaboration in the management of cardiogenic shock are vital to improving clinical outcomes in terms of mortality. Jacob et al. proposed an interprofessional cardiogenic shock team model to ensure prompt diagnosis of cardiogenic shock and the underlying etiology. This approach can enhance the survival outcomes through timely utilization of medical therapies adjunct to supportive therapies and, if possible, earlier revascularization. Implementation of a plan for escalation of hemodynamic support with IABP or the newer advanced mechanical support devices such as left-side heart pump systems in those patients with severe hemodynamic collapse deemed to require a mechanical support device that can ensure high cardiac output.II[57] 

Patients with cardiogenic shock requiring hemodynamic support are critically ill and necessitate intensive care by an interprofessional team that includes the emergency department, critical care intensivist, interventional cardiologist, advanced heart failure specialist, cardiothoracic surgeon depending upon the underlying clinical condition causing cardiogenic shock. These causes can include mitral valve regurgitation due to papillary muscle rupture or ventricular septum defect as a result of myocardial infarction necessitating surgical repair, telemetry units, 24-hour intensive care nurse certified to manage IABP, 24-hour certified nursing assistant to perform frequent monitoring of vitals and peripheral pulses, and the 24-hour pharmacist to assist in the selection of the appropriate dose of the medications and identify and manage the drug interactions. The decision to initiate an IABP support is usually at the discretion of the interventional cardiologist and the advanced heart failure specialist after taking into consideration the short term and long term prognosis, goals of the care, age, and other comorbidities of the patient that may have an impact on the clinical outcomes.

Although the SHOCK II study fails to demonstrate short-term and long-term mortality benefits with IABP therapy adjunctive to PCI in ST-elevation MI complicated by CS as compared to a medical therapy group, it may be secondary to extensive damage to the heart muscle tissue not able to sustain the cardiac function for an increased period of time despite IABP support. In such patients, IABP may be an option as temporizing hemodynamic support to bridge to the durable mechanical assistance device or heart transplantation. Therefore, early consultation with an interprofessional cardiogenic shock team, including an interventional cardiologist and advanced heart failure specialist, before or at the time of IABP insertion may prove beneficial to devise a plan of care about urgent revascularization. Such a plan can ensure the adequacy of the hemodynamic support and contemplate a long-term plan of care to improve survival outcomes. The interventional cardiologist's role is the decision-making about the initiation of mechanical support devices and placement of the IABP and or other percutaneous mechanical support devices and revascularization for acute myocardial infarction. Advanced heart failure cardiologist evaluation is essential to assess for the requirement of durable ventricular assist devices or heart transplantation, and, if needed, can coordinate for listing the patient for durable VAD and heart transplantation. Additionally, heart failure specialists can provide further recommendations about treatment options for patients with decompensated heart failure complicated by cardiogenic shock. Further, the cardiothoracic surgery team should be promptly involved in patient care if mechanical complications of myocardial infarction, i.e., severe mitral regurgitation due to papillary muscle rupture or ventricle septal rupture, is diagnosed and require urgent surgical repair. Furthermore, the role of intensivist is imperative in care as patients with cardiogenic shock secondary to myocardial infarction usually experience multi-organ failure, and require intensive care interventions to prevent and treat multi-organ dysfunction and manage the critically ill patients requiring mechanical ventilator support, and prevent and treat malnutrition, delirium, pressure ulcers, and thromboembolism.[58] The intensive care unit physician plays the role of a coordinating physician and serves the responsibilities of diagnosis, triage, activation of subspecialties and additional team members, and medical management of the cardiogenic shock patients with multi-organ failure. Moreover, an intensivist has a vital role in ensuring the adequate functioning of the IABP and continuous monitoring for early identification of the device-related complication and its management. Intensivist and interventional cardiologists must be cognizant of the patient's goals of care consistently throughout the care. In conditions of refractory cardiogenic shock with an inappropriate response to medical therapy, revascularization, inotropes/vasopressors and IABP support, and further escalation of care to heart transplantation or permanent ventricular assist device is not a goal or deemed futile, and an interprofessional team approach can assist in the transition of care to end of life care/comfort care. In such a condition, consultation of the palliative care/hospice care team to provide comfort care is warranted.

Nursing, Allied Health, and Interprofessional Team Interventions

Patients with cardiogenic shock dependent on IABP support require certified/accredited intensive care unit nurses to monitor the hemodynamics of the patient. Therefore and to ensure adequate augmentation with IABP. Vitals should be observed frequently over the day, and any adverse change in hemodynamics should be reported to the intensivist immediately. Patients with IABP catheter inserted in the femoral artery need bedrest with as minimal as possible movement of the lower extremity to avoid displacement of the intra-aortic balloon from its recommended position. Bending of leg and movement of the patient can lead to migration of balloon proximal to the origin of the subclavian artery and can result in vascular complications including compromise of blood supply to the left upper extremity and stroke. Migration of the balloon below the origin of the renal artery can result in renal injury.

Patients with IABP in place are at risk of developing bacteremia and sepsis. Therefore, sepsis workup should be initiated promptly if the patient developed fever, leukocytosis, or other signs of infection, and, if clinically warranted, empiric antibiotic therapy should commence.

Another significant complication of IABP is the thrombosis or thromboembolic phenomena. To reduce the risk of thrombosis, the patients requiring IABP are usually anticoagulated unless there is a pre-existing contraindication to anticoagulation. These patients should be monitored closely for bleeding complications, and hemoglobin/hematocrit should be monitored closely.

Daily chest X-ray should be obtained to confirm the position of the IABP catheter tip. The carina may be the best landmark to confirm the positioning of the IABP catheter tip, and the IAPB catheter tip 2 cm above the carina results in adequate positioning of the IABP in 95.3% of the patients (1.5 to 3.5 cm distal to the origin of the Left subclavian artery).[59]

Daily monitoring of hemoglobin/hematocrit, platelet count, serum creatinine is advised.

Adequate anticoagulation management requires collaborative efforts of ICU pharmacist, nurses, and the physician to monitor for activated clotting times and an early sign of the bleeding complication. [Level 5]

Nursing, Allied Health, and Interprofessional Team Monitoring

The interprofessional team should closely monitor vital signs to ensure adequate augmentation with IABP. In patients with hypotension/hemodynamic instability despite being on IABP, urgent troubleshooting should be considered that includes evaluation of adequate timing of balloon inflation and deflation to assess the positioning of the intra-aortic balloon by fluoroscopy and imaging studies checking for kinking of tubings and functioning of gas supply apparatus. If no problem is detected, then alternate possibilities may be considered that include dehydration, sepsis, or overt hemodynamic collapse due to severe myocardial depression.

If the patient develops a fever, a broad differential diagnosis should be considered that includes but is not limited to sepsis, thrombosis, or thromboembolic phenomena related to IABP catheter/balloon, pressure ulcers, pneumonia/atelectasis, or drug reaction.

Monitor for hemorrhagic complications.

Frequent neurological exams to monitor for cerebrovascular complications (stroke) and to monitor for delirium are needed.

Helium gas leaks secondary to balloon rupture or malfunction can lead to acute embolic stroke. In case of a suspicion of gas leak from the balloon, the patient should be placed in a Trendelenburg position, and IABP should be switched off with termination of gas supply.

Frequent monitoring of peripheral arterial pulses is imperative to promptly identify the vascular complications secondary to IABP and manage them accordingly.