Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 204

The first step is to determine if the patient requires coronary angiography (Figure 3.2). The second step is to determine if the patient requires revascularization. The third step is to determine whether CABG or PCI is appropriate. The need for coronary angiography does not imply a need for revascularization once CAD is found. In fact, medical therapy is frequently appropriate in a patient with significant, even multivessel CAD (with no left main disease). Coronary angiography serves as a risk stratification tool that helps determine whether medical therapy alone is appropriate. Based on ISCHEMIA trial, coronary CTA may replace coronary angiography and may be used to exclude left main disease and proceed with conservative management even in patients with multivessel disease.

In order to benefit from revascularization, one of the following 2 features excluded from ISCHEMIA trial must be present: (1) severe refractory angina, or (2) severe left main disease, regardless of angina.^19,20 Extensive 3-vessel CAD or 2-vessel CAD with proximal LAD may also benefit from CABG, but less strongly. Refractory angina is defined as frequent angina (multiple times weekly) that persists despite the use of at least two antianginal medications (or less in case of intolerance or a baseline low BP and heart rate).

Old retrospective analyses suggested that revascularization in the setting of extensive ischemia involving ≥10% of the LV was associated with a reduction of mortality; this suggested a role for ischemia assessment in guiding revascularization.⁶¹ However, the large randomized trial ISCHEMIA disproved this hypothesis. Analyses from both ISCHEMIA and COURAGE suggest that the anatomic burden of disease is a far superior predictor of death and cardiac outcomes than ischemia, even though neither one predicts a benefit from revascularization. ^62,63 Ruling out left main disease via CTA or angiography appears more important than functional ischemia evaluation.

In chronic stable CAD, revascularization of single or even multivessel CAD mainly has a symptomatic value, particularly in patients with refractory angina, with no effect on survival or MI prevention.

While a significant stenosis has a higher individual risk of plaque rupture and MI (~3% per year) than a non-significant plaque (<0.5%) (COURAGE, ISCHEMIA, FAME trials),^19,64–66 non-significant plaques are much more common throughout the coronary vasculature than significant plaques; therefore, MI or ACS often occurs over a lesion that is <50% stenotic: these lesions were responsible for 2/3 of ACS events upon long-term follow-up in PROSPECT trial and coronary CT studies. ^32,33,67 In FAME-2 trial, patients with insignificant FFR had a very low risk of MI from individual plaques, but the summation MI risk was still ~2% at 8 months and 8% at 5 years.^28,66 While stenting reduces the risk of spontaneous events arising from a significant plaque, the benefit is negated by periprocedural myocardial infarction (~2.5%), stent thrombosis and severe restenosis, which explains why stenting stable CAD does not reduce the overall MI risk.⁶⁶ Moreover, a larger number of events continues to arise from non-significant plaques.