Should patients with stable ischemic heart disease undergo revascularization?
Stress testing
Noninvasive stress testing has played a role in helping to guide revascularization decisions in stable ischemic heart disease. In particular, revascularization in the setting of greater than 10% ischemia on perfusion imaging has been associated with a lower risk of cardiac death than in those who were revascularized with an ischemic burden less than 10%.9
A substudy of COURAGE found that percutaneous coronary intervention reduced ischemia to a greater degree than medical therapy alone on serial nuclear stress tests in patients with stable ischemic heart disease.10 In this substudy, when both groups were combined, the investigators also found that there were fewer adverse events in those who had an overall reduction of ischemia regardless of treatment strategy.
ISCHEMIA: Revascularize those with ischemia?
While COURAGE, BARI 2D, and FAME 2 suggested that early revascularization for low-risk patients with coronary artery disease does not confer a benefit over medical treatment alone with regard to hard clinical end points, it remains unclear whether an early revascularization strategy is advantageous in patients with stable ischemic heart disease who have at least a moderate amount of ischemia on noninvasive stress testing.
The ongoing ISCHEMIA (International Study of Comparative Effectiveness With Medical and Invasive Approaches) trial will help to answer that question. In this study, 8,000 patients with stable angina and at least moderate ischemia on noninvasive stress testing are being randomized before coronary angiography either to guideline-directed medical therapy plus revascularization (percutaneous or surgical) or to medical therapy alone.11 The ISCHEMIA study population reflects current practice more closely than the previous studies discussed above in its inclusion of fractional flow reserve and later-generation drug-eluting stents.
The results of ISCHEMIA will be an important piece of the puzzle to answer whether patients with stable ischemic heart disease benefit from revascularization in terms of cardiovascular mortality or myocardial infarction (the primary end point of the study).
Studies in additional subsets
It is important to recognize that there are additional subsets of patients with stable ischemic heart disease (those with multivessel disease, left main coronary disease, or low ejection fractions, for example) who have been studied to help determine when and how to perform revascularization. In addition, there are guidelines12 for both interventional cardiologists and cardiac surgeons that help delineate which patients should undergo revascularization. While a complete review is beyond the scope of this discussion, three trials are worth mentioning:
The Coronary Artery Surgery Study (CASS)13 revealed that revascularization in left main coronary artery disease is associated with lower mortality rates than medical therapy alone. This study, along with others, eventually led to recommendations for revascularization to be performed in all patients with significant left main coronary disease, regardless of symptoms or stress test findings.14,15
The Surgical Treatment for Ischemic Heart Failure (STICH) trial16 found that patients with a low ejection fraction (< 35%) and ischemic heart disease had no difference in all-cause mortality rates when treated with CABG plus medical therapy compared with medical therapy alone (although the study’s design has been heavily criticized).
The Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) study17 found that CABG was associated with fewer adverse events in three-vessel coronary artery disease or complex left main coronary artery disease compared with percutaneous coronary intervention. The study used early-generation paclitaxel drug-eluting stents that are no longer used in contemporary practice. This study established the SYNTAX score, which is often used to help make revascularization decisions. A low SYNTAX score of 0 to 22 (meaning less-severe coronary artery disease) was associated with equivalent outcomes for both percutaneous coronary intervention and CABG. Thus, even if there is multivessel disease or left main disease, if the SYNTAX score is low, then percutaneous coronary intervention is an acceptable method for revascularization with similar results as for CABG.
A TEAM APPROACH
Due to the complexity of stable ischemic heart disease and the subtleties of managing these patients, a multidisciplinary “heart team” approach may be the best way to navigate treating stable ischemic heart disease via revascularization or with medical therapy alone. The heart team approach could take advantage of the particular expertise that the primary care physician, cardiologist, interventional cardiologist, and cardiac surgeon provide.
The upcoming results of studies such as the ISCHEMIA trial will help to provide additional guidance for these teams in long-term management of patients with stable ischemic heart disease.
