Acute coronary syndrome (ACS) is among the most common diseases practitioners encounter in the inpatient setting. This syndrome comprises a spectrum of obstructive coronary artery disease that most commonly arises from plaque rupture and/or erosion, leaving the vulnerable lipid-rich core exposed to the circulation, resulting in activation of platelets and the coagulation cascade leading to acute thrombotic occlusions.
Each stage of this syndrome can be treated differently based on clinical presentation, but often, a catheter-based interventional approach is preferred. For years, the primary treatment of ACS revolved around maximizing medical therapy with the use of antiplatelet and anticoagulation therapy, anti-anginal medications, and aggressive lipid lowering and risk factor modification. In 1958, the advent of thrombolytics shifted the paradigm in the approach and treatment of ACS. First used by Fletcher and colleagues and later validated by trials such as ISIS, GUSTO, and GISSI, intravenous administration of thrombolytics could successful treat acute thrombotic occlusions, mainly in regards to STEMI. However, even with the improvement in survival, size of infarct, and overall morbidity, thrombolytic therapy continued to demonstrate issues of major bleeding, including intracranial hemorrhage, as well as issues with reinfarction. The most effective thrombolytic regimens achieve angiographic infarct-artery patency in only 50% of patients within 90 minutes. Bleeding requiring transfusion occurs in 5% of patients and stroke in 1.8% with these regimens. The management of ACS showed gradual improvement; however, outcomes were still poor due to these issues - this all changed in 1977, when Andreas Gruentzig, developed a novel approach to treat ACS with the use of balloon angioplasty, forever changing the landscape of cardiology and would later be known as the father of interventional cardiology.
The establishment of catheter-based interventions first occurred in the late 1970s. The idea behind catheter directed interventions for acute coronary syndrome flourished due to its ability to use the circulation as a "vascular freeway" to approach occlusive coronary disease without the use of open-heart surgery. The ability to gain percutaneous vascular access and intervene on an occluded vessel with a catheter completely revolutionized cardiovascular medicine. A cardiac catheter, first characterized by Werner Forssmann in 1929, was described as a plastic tube that allowed delivery of substances (medications or contrast) for imaging and monitoring of intracardiac pressures. Catheters continued to evolve from purely diagnostic tools for pressure measurements, to therapeutic tools as described by Gruentzig's breakthrough in the late 1970s.
Throughout the 1970s and 1980s, balloon angioplasty remained controversial and primarily indicated for stable ischemic lesions. ACS patients continued to rely on the use of intravenous thrombolytic therapy and coronary artery bypass grafting (CABG) surgery for treatment. Then in the late 1990's Stone, Grines, in collaboration with the other PAMI (primary angioplasty in myocardial infarction) investigators demonstrated the safety and efficacy of using balloon angioplasty for the primary treatment of acute coronary syndrome. PAMI demonstrated that patients that presented with ACS treated with percutaneous balloon angioplasty compared to tissue plasminogen activator (t-PA) demonstrated reduced rates of in-hospital mortality (2% vs 7%, P = 0.03), as well as recurrent ischemia (11% vs 29%, P < 0.001) and stroke (0% vs 4%, P = 0.02), and demonstrated shorter hospital stays (7.6 vs 8.4 d, P = 0.04).
Again in the late 1990s two more landmark trials, BENESTENT, and STRESS were published demonstrating the use of a metal scaffold, termed a stent, was efficacious and safe for implantation in the coronary arteries and exhibited a lower rate of major cardiovascular adverse events when compared to balloon angioplasty . These stents, however, were bulky, prone to restenosis, and need for repeat revascularization. Additionally, the procedure itself correlated with many vascular complications limiting its utility and widespread adoption. These issues were addressed and in the early 2000s with the development of a new stent design with the ability to elute antiproliferative agents (i.e., sirolimus, paclitaxel, etc.). This discovery once again revolutionized the field of cardiology and how both stable ischemic heart disease and acute coronary syndrome could be treated. As time has progressed, the catheter and catheter delivery system designs have undergone a variety of changes allowing for more capabilities like delivery of equipment, such as stents and balloons, over a wire or monorail system, as well as improved deliverability to target vessels with fewer rates of major adverse cardiovascular events.
Acute coronary syndrome is consistently a leading global cause of morbidity and mortality. In the United States, the estimated annual incidence of ACS is approximately 550000 new events and greater than 200000 recurrent cases. ACS primarily occurs in adults and varies by gender with men being affected on average more often and early with an average age of 65 years vs. 72 years for women. Per the National Cardiovascular Data Registry (NCDR), over 600000 percutaneous coronary interventions (PCI) are performed in the United States yearly. In 2014 the registry reported 667424 procedures performed in 1612 hospitals across the United States. Additionally, NCBR reports in 2014 approximately 64% of procedures were for the acute coronary syndrome.
Acute coronary syndrome comprises a spectrum of obstructive coronary artery disease that most commonly arises from plaque rupture and/or erosion, leaving the vulnerable lipid-rich core exposed to the circulation, resulting in activation of platelets and the coagulation cascade leading to acute thrombotic occlusion. There are three major subtypes of ACS which are: Unstable Angina, non-ST elevation myocardial infarction (NSTEMI), and ST elevation myocardial infarction (STEMI). Each of these subtypes represents a different stage in the spectrum of the disease. Plaque erosion with subendocardial ischemia represents the majority of cases of unstable angina and NSTEMI, while plaque rupture and complete thrombotic occlusion, of an epicardial coronary, with associated transmural infarction, is characteristic of STEMI.
History and physical exam remain the cornerstone for initial diagnosis and management of acute coronary syndrome. Patients will often present in the field to first responders with limited access to medical records. Rapid recognition of this syndrome is vital to good patient outcomes.
Common symptoms of Acute Coronary Syndrome are:
Common signs of Acute Coronary Syndrome are:
Physical exam finding for ACS can vary depending on the patient presentation on the extent and severity of the disease. In general, a complete physical exam is recommended for all patient presenting with ACS requiring catheter-based interventions, with particular attention paid towards the cardiovascular, respiratory, neurologic, and vascular systems. Due to the need for vascular access, need for various anticoagulants and antiplatelet medications, and use of percutaneous equipment, the risk for bleeding and mechanical complications of myocardial infarction must be ruled out before proceeding to the catheterization laboratory.
Allergies must undergo assessment before any catheter-based intervention to treat and sedate the patient throughout the procedure. Patients often will report adverse reactions to many of the medications used for moderate conscious sedation (i.e., fentanyl) as well as to medications administered post procedure (i.e., statins, angiotensin-converting enzyme inhibitors, etc.). Additionally, many patients report adverse reactions, allergies, or anaphylaxis to the iodinated contrast used for angiography. Thus, a thorough and detailed history and physical is mandatory prior to any cardiac catheter-based procedure.
To understand what pre-procedure evaluations are needed, one must understand what a cardiac catheterization procedure entails and what complications can arise from the procedure itself as well as a patient with an acute coronary syndrome. The procedure itself entails gaining vascular access and cannulation of the coronary arterial tree. Large doses of anticoagulant medications as well as antiplatelet medications will be administered, significantly increasing the bleeding risk of the procedure. Additionally, iodinated contrast is used for imaging in angiographic procedures, most of which, are consider nephrotoxic. Other patients can present with a large anterior myocardial infarction or right ventricular infarction can often present in cardiogenic shock or advanced atrioventricular heart block. A thorough peri-procedural evaluation is vital before sending a patient for cardiac catheterization.
12 Lead Electrocardiogram (ECG):
Types of Coronary Wires:
Types of Coronary Catheters:
Adjunctive Catheter Therapy:
Multiple other adjunctive catheter therapies exist, however, are beyond the scope of this document, and are not discussed in detail. Some examples of these therapies are listed below:
Mechanical Support Devices:
Mechanical support catheters and therapies exist; however, these are beyond the scope of this document and not discussed in detail. These are, but not limited to, intra-aortic balloon pump counterpulsation therapy, ventricular support devices, tandem heart support devices, and extracorporeal membrane oxygenation.
Pathologies that can be mistaken for acute coronary syndrome:
Six-month mortality rates recorded in the Global Registry of Acute Coronary Events (GRACE) for patients with STEMI were estimated close to 17%, 13% for patients with NSTEMI ACS, and 8% for those with unstable angina. These numbers have continued to decline as percutaneous coronary intervention continues to evolve and operator experience increases. Additionally, the broad adoption of transradial PCI has continued the trend in the decrease in mortality in both NSTEMI and STEMI. This adoption has support from the results of the MATRIX, STEMI-RADIAL, and numerous other studies in the past decade.
Complications that arise from coronary intervention can vary from minor to major depending on their hemodynamic significance. The most common complication of coronary intervention is access site bleeding. Due to a large amount of anticoagulation given and the occasional need for large bore access, access site complications (hematoma, pseudoaneurysms, dissection, etc.) can arise and most commonly result with transfemoral access. Additional complications seen are contrast-induced nephropathy, vessel dissection or perforation, acute cerebrovascular accident or other embolic phenomena, myocardial infarction, need for emergent cardiothoracic surgery, and rarely death. The rates of complications vary by center and operator volume, however, for the most part, the risk of the procedure is generally low (between 1 to 2%), and the benefit of the procedure far outweigh the risk.
Post-acute coronary syndrome patients are strongly encouraged to participate in cardiac rehabilitation. Patients should undergo functional testing before starting a supervised exercise program. Patients are often seen as an outpatient 4 to 6 weeks post ACS for further assessment and risk stratification, primarily with functional assessment with an exercise stress test, before resuming normal activity without restrictions. Additionally, on occasions, patients are further assessed with vasodilator myocardial perfusion imaging, prior to initial hospital discharge to evaluate the need for complete revascularization if diffuse disease was present on target vessel revascularization.
Cardiothoracic surgery consultation should be consulted any time PCI is performed as part of the "Heart Team Approach" to coronary intervention.
The procedure itself is described to a patient as follows: "A cardiac catheterization is a minimally invasive procedure in which we will be assessing the blood vessels of your heart with the use of contrast dye and fluoroscopy. The first step of the procedure entails gaining vascular access, most commonly through the radial artery in the wrist, and sometimes through the femoral artery in the groin. Once arterial access is obtained, we will use a small catheter (approximately 2 to 3mm in diameter) and wire (approximately 0.014- 0.035 mm in diameter) to gain access to the arteries of the heart. Once the arteries are accessed, we will take multiple pictures to look for significant blockages. If blockages are present, we will proceed with fixing these lesions with stents and balloons. The procedure does care risks of bleeding and infection at the entry site, pain, discomfort, vascular complications, stroke, heart attack, and possible death. The risk is generally low (between 1 to 2%), and the benefits of the procedure far outweigh the risk."
The approach to acute coronary syndrome often is complex as each patient can present within different aspects of the spectrum of the disease. The consists of a multidisciplinary approach often termed as a "Heart Team Approach." This approach usually involves the use of a discussion between multiple health care providers in their approach to coronary artery disease. By use of both a surgical and percutaneous viewpoint, the approach to acute coronary syndromes can be in a systematic and safe way. [Level 1]
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