Percutaneous Coronary Intervention in ACS and ROSC

The treatment of choice for the management of ST-elevation myocardial infarction is coronary angioplasty with or without stent placement. The goal of health care providers in managing patients with this type of acute coronary syndrome (ACS) is to treat within the first hours of the onset of symptoms.¹ Percutaneous coronary intervention (PCI) can restore flow of blood into the myocardium in more than 90% of patients if performed by a skilled provider at a proficient PCI facility with a “door-to-balloon” time of less than 90 minutes.^2-4

Unstable angina and acute non-ST elevation myocardial infarction (NSTEMI) are medical emergency sub-types of acute coronary syndrome. The patients that develop hemodynamic instability, heart failure, persistent angina at rest despite intensive medical therapy, mitral regurgitation, formation of a new ventricular septal defect, or sustained ventricular arrhythmias are at extremely high risk. Either way, both of these types of patients should immediately undergo coronary arteriography and revascularization. Fibrinolysis should be avoided in NSTEMI or unstable angina.^5-7 The choice of revascularization procedure after angiography is dependent on the size and location of the blockage. PCI is most often performed on appropriate lesions, while coronary artery bypass grafting (CABG) is preferred in left main or equivalent disease, such as two or three vessel disease involving the left anterior descending artery with left ventricular dysfunction. On the other hand, 9% to 14% of patients with NSTEMI who undergo angiography have no significant coronary artery disease; these are thought to be caused by rapid clot lysis, vasospasm, myocarditis, and coronary microvascular disease.^8-11 These patients have a much better short-term prognosis than those with a culprit lesion.

Some issues relate to the performance of PCI and these include the development of bare metal stents (BMS), which have surpassed balloon angioplasty in the management of coronary artery disease because one of their ability to prevent restenosis by suppressing arterial recoil and contraction. However, 10% to 20% of patients may still experience restenosis after one year due to excessive growth of a neointima.^12-14 These have been reduced due to the emergence of drug eluting stents (DES), which have the ability to reduce revascularization rates by as much as 70%. For this reason, DES is preferred in the majority of PCI procedures.

In patients undergoing primary PCI, the radial artery approach is preferred over the femoral artery approach (if performed by a skilled operator) because bleeding is a common complication with STEMI.^15-16 Direct stenting is also preferred due to low-profile stent delivery (no need for pre-dilation), less radiation exposure and contrast, and shorter procedural times. In the patient with acute STEMI undergoing primary PCI, direct stenting decreases embolization of plaque constituents, lowers the incidence of no-reflow phenomenon and increases myocardial perfusion and salvage.^17-19 Because of the improvements in PCI, primary PCI with stenting performed in a timely manner is associated with better outcomes than fibrinolysis. However, in centers with no access to prompt PCI, fibrinolytic therapy is indicated.

PCI following return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest has shown positive results because half of these patients demonstrated acute coronary occlusion.²⁰ Most of the etiology of out-of-hospital cardiac arrest were due to ventricular fibrillation (VF) secondary to ST-elevation myocardial infarction (STEMI) or new left bundle branch block (LBBB). Therefore, angiography with revascularization of the infarct-related artery is recommended in this setting (Class I). The use of PCI in patients with ROSC of presumed ischemic cardiac etiology is reasonable even with an absence of clearly defined STEMI (Class 2B). More randomized controlled trials are needed to further validate these findings. Cardiac angiography and PCI, when integrated into a standardized post-cardiac arrest protocol, improves survival to hospital discharge.²¹ This is also due to the fact that successful PCI improves the cardiac ejection fraction.²⁰ Survival in post-cardiac arrest patients with STEMI is as high as 70% to almost 100%, depending on how fast a PCI is performed following a witnessed arrest due to VF.^22-23 Primary PCI has also shown to be applicable in NSTEMI because early revasculariztion in this setting has resulted in hemodynamic and electrical stability.

Lastly, it is common for patients to remain comatose after out-of-hospital cardiac arrest. After ROSC, a comatose state is not a contraindication to perform angiography and PCI in these patients. The goal of PCI in these patients is to keep neurological function intact to increase survival.

PCI can prevent the evolution of myocardial necrosis, prevent major adverse cardiac events (MACE), and treat the complications of ACS such as ventricular fibrillation, pulseless ventricular tachycardia, unstable tachycardias, symptomatic bradycardias, pulmonary edema, cardiogenic shock and mechanical complications of acute myocardial infarction. It is essential that hospitals be equipped with systems to provide prompt and effective PCI to increase survival to hospital discharge in post-cardiac arrest victims.

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