Coronary artery calcification is frequently encountered during percutaneous coronary intervention (PCI). Calcified plaque poses numerous challenges to successful percutaneous coronary intervention. Stent delivery and optimal stent expansion become more difficult with a calcified plaque. Procedural complications and long-term adverse outcomes are worse and closely correlated with increasing severity of coronary artery calcification.
Risk factors associated with coronary artery calcification include advanced age, diabetes, kidney disease, and smoking, have been increasing in prevalence.
Severe coronary artery calcification is present in approximately 6% to 20% of all patients treated with PCI.
A calcified nodule (CN) is an eruptive accumulation of small nodular calcifications with a thick calcified plate and overlying thrombus that can correlate with an acute coronary syndrome. Calcified nodules are present in approximately 4% of lesions and are best visualized with optical coherence tomography (OCT) in vivo.
A comprehensive history can elucidate risk factors associated with increased coronary artery calcification (CAC). In patients with multiple risk factors for CAC undergoing coronary angiography, a high clinical suspicion should be present and intravascular imaging should be used as needed for further characterization.
Severe coronary artery calcification has been classically defined angiographically as the presence of radiopacities appreciated without cardiac motion before the injection of contrast, that involves both sides of an arterial wall, with calcification length of greater than or equal to 15 mm and extend at least partially into a target lesion. By intravascular ultrasound (IVUS) severe coronary artery calcification is defined by the presence of an arc of calcium greater than or equal to 270 degrees on at least one cross-sectional plane. By angiography alone, coronary artery calcium is significantly underappreciated and underrecognized. Intravascular imaging modalities including IVUS and OCT allow for improved detection and characterization of presence and severity of coronary artery calcification.
The treatment of calcified lesions during PCI is dependent on the severity of calcium. An OCT-based scoring system, known as the calcium-volume index or rule of 5's helps to stratify the likelihood a calcified plaque would correlate with stent under-expansion if not treated with a lesion preparation strategy. Calcified lesions involving an arc of calcium more than 50% of the vessel (greater than 180 degrees), with a thickness exceeding 0.5mm and over than 5 mm in length, are most strongly associated with stent under-expansion and should be treated with atherectomy when appropriate. Calcified lesions with a mild to moderate degree of calcification can be treated with cutting, scoring or sculpting balloons and often do not require atherectomy. Severely calcified lesions however are best managed with adjunctive atherectomy in advance of stent implantation. Not only does atherectomy improve the likelihood of successful stent delivery, but atherectomy modifies the plaque morphology of the lesion, facilitating adequate stent expansion by increasing the possibility of calcium fracture. Maximizing stent expansion can help to reduce the likelihood of in-stent restenosis.
The two primary atheroablative modalities for lesion preparation of severely calcified lesions before stent implantation include rotational atherectomy (RA) and orbital atherectomy (OA). Rotational atherectomy was developed by David Auth and has been in clinical use since 1988. RA uses differential cutting, is available in diameters ranging from 1.25 to 2.50 mm can rotate at speeds often ranging from 150000 to 200,000 rpm. The PREPARE-CALC trial demonstrated that target lesion revascularization, stent thrombosis, and target vessel failure were low and not significantly different between the traditional angioplasty and RA groups with contemporary drug-eluting stents.
Orbital atherectomy is a newer modality, that utilizes an eccentrically mounted, diamond-coated crown that orbits bi-directionally. Coronary orbital atherectomy is available with a single 1.25mm burr and can orbit at either low speed (80000 rpm) or high speed (120000 rpm). The ORBIT II trial compared orbital atherectomy with historical controls and found OA to be safe, feasible and associated with a low rate of adverse ischemic events. A real-world multicenter, all-comers registry of patients treated with orbital atherectomy confirmed these findings.
A new tool for lesion preparation of severely calcified coronary plaque is intravascular lithotripsy (IVL), which incorporates emitters that release sonic pressure waves to modify calcified plaque and fracture calcium. Excimer-laser coronary atherectomy (ELCA) can be used to facilitate the treatment of under-expanded stents due to stent implantation within the heavily calcified plaque. Following stent implantation in a calcified plaque, routine intravascular imaging can be used to confirm the achievement of adequate stent expansion.
Intravascular imaging modalities allow for characterization of plaque and can detect calcified plaque with increased sensitivity than with angiography alone. Intravascular imaging with IVUS or OCT at times has limitations in its ability to differentiate predominantly calcified plaque from lipid-rich plaque due to the often heterogeneous nature of the disease. Near-infrared spectroscopy (NIRS) is an intravascular imaging modality that can detect lipid-rich plaque (LRP), helping to distinguish LRP from calcified plaque. Calcium may deposit in different cardiovascular structures including within coronary arteries, myocardium, and pericardium.
The Evaluation of Treatment Strategies for Severe Calcific Coronary Arteries: Orbital Atherectomy vs. Conventional Angioplasty Technique Prior to Implantation of Drug-Eluting Stents: The ECLIPSE Trial (ECLIPSE) [ClinicalTrials.gov Identifier: NCT03108456] is an ongoing randomized clinical trial that will be the largest to date evaluating the treatment of severely calcified lesions with PCI. The ECLIPSE trial is comparing orbital atherectomy versus conventional angioplasty prior to stent implantation and plans to enroll an estimated 2000 patients.
Calcified coronary artery lesions are associated with worse outcomes both periprocedural and long-term when treated with percutaneous coronary interventions. At the time of PCI, calcified lesions have correlations with an increased likelihood of unsuccessful stent delivery as well as worse stent expansion compared with a non-calcified lesion. The stent under-expansion commonly associated with calcified lesions is directly associated with higher rates of restenosis.
Percutaneous coronary revascularization of coronary artery calcification correlates with increased procedural complications and worse long-term outcomes. Stent under-expansion is a common complication of PCI of a heavily calcified plaque without adequate lesion preparation.
Risk factors for calcified lesions include increasing age and diabetes, smoking, peripheral vascular disease, chronic kidney disease, and hemodialysis.
Recognition of calcified plaque is essential during PCI to optimize stent implantation. Calcified plaque is best assessed and characterized by intravascular imaging modalities. Stent under-expansion is a frequent complication of PCI in severely calcified plaque and correlates with high rates of in-stent restenosis. Severe coronary artery calcification frequently warrants lesion preparation to facilitate optimal stent expansion.
After PCI, management involving an interdisciplinary team that includes the vascular surgeon, the primary care provider, and nurse practitioner, as well as specialty trained nursing and pharmacy, should participate in optimizing patient care following the procedure to enhance patient outcomes. Communications between these professionals will improve the coordination of care. Specialty trained nurses in cardiology, intensive care, and rehabilitation may be involved.
In the aftermath, the primary care physician, nursing, and pharmacy can collaboratively educate the patient on limiting the risk factors for CAD include cessation of smoking, participating in regular exercise, eating a healthy diet, and maintaining optimal body weight. [Level V]
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