Assessing risk through "inspired" care

This retrospective subanalysis of the Adenosine Sestamibi SPECT Post-Infarction Evaluation (INSPIRE) trial shows that early adenosine sestamibi stress testing is not only safe early after myocardial infarction (MI), but can also be very useful to identify patients at very low risk for events in the first year after discharge. The rationale is that this group can be discharged early with effective medical therapy without catheterization or other procedures and their condition monitored subsequently in the office.

This report should be considered in the context of the “pendulum” swinging back towards conservative therapy. In last year’s Occluded Artery Trial (OAT), patients with at least moderate-sized MI and persistently occluded arteries were randomized to opening the vessel or not, and events were not reduced; in fact, a small increase in MI suggests that the patients were stable, and altering that condition with revascularization of the occluded infarct vessel may make them prone to future events.¹ Some of the patients in the current INSPIRE low-risk investigation would have been eligible for OAT, though most would not, since their infarcts would have been too small.

A second, more recent trial investigated invasive versus conservative strategies in a contemporary cohort of patients not after MI but with stable angina.² The Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial showed no advantage of intervention and was widely covered in the lay press, much to the confusion of many of our patients. None of the INSPIRE patients would have been enrolled in COURAGE.

It is critical to be mindful of the clinical context in which we are assessing our patients: the INSPIRE trial considered patients hospitalized for acute MI, and as two thirds of eligible patients received thrombolytic agents, presumably in noninterventional (or non-US or both) hospitals. For MI patients treated at such hospitals, the INSPIRE results are compelling and when combined with the usual clinical criteria for low-risk status—young age, absence of heart failure or recurrent ischemia, preserved renal function, etc—suggest that patients with small, uncomplicated MIs will do well on medication alone and need not be transferred or referred soon after discharge for mandatory angiography.

Are the INSPIRE results enough to keep low-risk patients away from the catheterization laboratory when they present to hospitals with coronary intervention available? Early discharge without intervention is no less possible in this context, but we should not feel guilty about catheterizing patients immediately or soon thereafter and skipping the nuclear stress test, as an equally good measure of risk stratification is likely to be seen after arteriography and is probably firmly established as the practice pattern based on the updated American College of Cardiology/American Heart Association guidelines. Immediate revascularization of totally occluded arteries (indicated by ST elevation on presentation) and early revascularization of subtotally occluded or unstable plaque (ie, non-ST elevation) still constitutes the best practice.³