CORRESPONDENCE: LETTER TO THE EDITOR
Reply
John J. Mahmarian, MD* and
Craig M. Pratt, MD
* Methodist DeBakey Heart Center, Cardiology, 6550 Fannin Street, Suite 677, Houston, Texas 77030 (Email: jmahmarian{at}tmh.tmc.edu).
We appreciate the opportunity to re-emphasize the clinical messages from the (INSPIRE) trial (1,2). Patients at very high clinical risk and those who had percutaneous coronary intervention (PCI) for acute ST-segment elevation myocardial infarction (MI) were excluded from INSPIRE because PCI is the preferred approach in these settings. The INSPIRE cohort still represents  75% of acute myocardial infarction (AMI) patients today who do not receive acute PCI but who still are at substantial risk for subsequent events. In fact, 64% of our low Thrombolysis In Myocardial Infarction (TIMI) risk-score patients had intermediate- or high-risk scintigraphic characteristics resulting in a high 1-year event rate of 15%.
The purpose of imaging is not only to stratify risk but also to determine in whom risk can be reduced. The low- and intermediate-risk groups in INSPIRE (which represented two-thirds of all enrolled patients) would have unlikely benefited from coronary revascularization owing to their low initial risk or lack of inducible ischemia, respectively. The INSPIRE results complement the findings from the OAT (Occluded Artery Trial) (3), which showed no advantage (and potential harm) from PCI and stenting of occluded arteries post-AMI in patients who lacked significant ischemia. Adenosine single-photon emission computed tomography (SPECT) is a practical initial imaging method to identify such patients and thereby avoid unnecessary and costly invasive procedures.
With regard to the randomized cohort, the comparable reduction in scintigraphic ischemia among the 2 strategies led to similar 1-year event rates. The crossover rates are similar to those reported in other acute coronary syndrome trials and were comparable between the two strategies. Although INSPIRE was underpowered to categorically assess differences in event rates between strategies, it provides event rate estimates for designing an adequately powered outcome trial. The main INSPIRE trial results give strong support for the premise that the presence and extent of scintigraphic ischemia predict risk and are surrogate markers for cardiac events.
Medical therapy is appropriate in all post-AMI patients, but it is usually not maximized. In INSPIRE, most patients in both randomized strategies received antiplatelet agents, beta-blockers, and statins. However, INSPIRE was unique in mandating maximally tolerated doses of all classes of anti-ischemic medications to patients in the medical-therapy limb. The objective was to minimize scintigraphic ischemia—a goal achieved in the majority of patients.
Both INSPIRE (1,2) and other recently published trials (3,4) provide new evidence that a conservative approach of early risk stratification through noninvasive imaging is not only reasonable but appropriate in the majority of patients post-AMI so as to identify those most likely to benefit from coronary revascularization. Finally, INSPIRE also shows that in patients with ischemia and preserved left ventricular function, intensive medical therapy is an excellent initial treatment option.
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References
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- Mahmarian JJ, Shaw LJ, Filipchuk NG, et al. AdenosINe Sestamibi SPECT Post-InfaRction Evaluation (INSPIRE) investigators A multinational study to establish the value of early adenosine technetium-99m sestamibi myocardial perfusion imaging in identifying a low-risk group for early hospital discharge following acute myocardial infarction J Am Coll Cardiol 2006;48:2448-2457.[Abstract/Free Full Text]
- Mahmarian JJ, Dakik HA, Filipchuk NG, et al. An initial strategy of intensive medical therapy is comparable to that of coronary revascularization for suppression of scintigraphic ischemia in high-risk but stable survivors of acute myocardial infarction J Am Coll Cardiol 2006;48:2458-2467.[Abstract/Free Full Text]
- Hochman JS, Lamas GA, Buller CE, et al. Occluded Artery Trial investigators Coronary intervention for persistent occlusion after myocardial infarction N Engl J Med 2006;355:2395-2407.[Abstract/Free Full Text]
- de Winter RJ, Windhausen F, Cornel JH, et al. Invasive versus Conservative Treatment in Unstable Coronary Syndromes (ICTUS) investigators Early invasive versus selectively invasive management for acute coronary syndromes N Engl J Med 2005;353:1095-1104.[Abstract/Free Full Text]
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