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Ischemia-guided revascularization using myocardial perfusion along with SPECT imaging substantially lowers the risk of major adverse events in patients with multivessel coronary disease. The improvement, outlined in a registry study in the July 17, 2012, issue of the Journal of the American College of Cardiology, stems largely from a reduction in repeat revascularization.

An ischemia-guided approach to intervention was supported by the FAME (Flow Reserve versus Angiography for Multivessel Evaluation) trial, which appeared in the New England Journal of Medicine in January 2009. The study found that using fractional flow reserve (FFR) instead of angiography to guide PCI decreased adverse events at 1 year. It was previously unknown, however, whether using perfusion imaging plus SPECT (single-photon emission computed tomography) to inform revascularization offered similar benefits.

In the current study, a group led by Seung-Jung Park, MD, PhD, of Asan Medical Center (Seoul, South Korea), retrospectively reviewed data from the Asan Multivessel Registry on 5,340 patients, 48.4% of whom underwent PCI with DES and 51.6% of whom received CABG. Within the entire cohort, 42.3% of patients received myocardial perfusion imaging plus SPECT, with ischemia-guided revascularization performed in 17.3% (12.4% of PCI patients and 21.8% of CABG patients). Follow-up was maintained for approximately 5 years.

There were no differences with regard to procedural success between the ischemia-guided and conventional groups (P = 0.40), irrespective of whether patients underwent PCI or CABG.

Compared with a conventional approach, ischemia-guided revascularization yielded a significant decrease in the overall rate of major adverse cardiac and cerebrovascular events (MACCE; death, MI, stroke, or repeat revascularization), due specifically to a reduction in repeat revascularization. Guidance continued to have an effect on outcomes after adjustment for baseline clinical and angiographic factors (table 1).

Table 1. Effect of Ischemia-Guided vs. Standard Revascularization

^a Death, MI, stroke, or repeat revascularization.

In addition, subgroup analyses demonstrated that ischemia guidance reduced the risk of MACCE for PCI patients (17.4% vs. 22.8%; adjusted HR 0.59; 0.43-0.81; P = 0.001) but not for CABG patients (16.0% vs. 18.5%; adjusted HR 0.87; 95% CI 0.67-1.14; P = 0.31).

Unanswered Questions

According to the paper, the gains seen with myocardial perfusion imaging and subsequent ischemia-guided revascularization are consistent with the impact of FFR in the FAME trial. The current study, though, offers longer follow-up than the 1-year data provided by FAME, and the authors “found that the curves for MACCE in the ischemia-guided and non-ischemia-guided groups progressively diverged through 5 years.”

Earlier studies have indicated differences between the 2 imaging technologies, the investigators note. Namely, perfusion imaging has lower sensitivity than FFR for detecting ischemic myocardium in patients with multivessel disease, but perfusion imaging plus SPECT might be able to identify clinically significant lesions, they say. “Moreover, [myocardial perfusion imaging] has technical advantages, including its noninvasiveness and universal applicability to all lesion subsets, including chronic total occlusion, calcified lesions, and severely tortuous lesions, in which FFR assessment is practically difficult,” the study authors write.

In an accompanying editorial, William S. Weintraub, MD, of the Christiana Care Health System (Newark, DE), comments that the observational nature of the study by Park et al limits its interpretation. For example, there could be patients who did not undergo perfusion imaging but whose revascularization still focused on ischemic areas.

As such, the best comparison might be in patients who underwent perfusion imaging with revascularization that did and did not match the ischemic area, he suggests. Among these subsets, ischemia guidance reverses the main findings by showing a nonsignificant 25% reduction in repeat revascularization (P = 0.13) and a statistically significant 25% reduction in death, MI, or stroke (P = 0.046).

“Because revascularization in [stable ischemic heart disease] can reduce inducible ischemia and relieve angina, selecting patients for revascularization on the basis of the presence of ischemia would seem to be appropriate,” Dr. Weintraub writes. “However, it is not well-established which patients benefit by relieving ischemia with revascularization leading to decreased mortality or nonfatal events.” He added that the ongoing ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches) trial will soon provide further insight into these issues.

Study Details

Median follow-up duration was 60 months in the ischemia-guided group and 53 months in the conventional group (P < 0.001). Ischemia-guided patients tended to be younger; this difference reached significance in the CABG patients (64.0 years vs. 63 years, P = 0.006) but not in the PCI patients. There were trends toward higher BMI in ischemia-guided patients in both PCI and CABG groups.

2. Weintraub WS. Should Ischemia Guide Revascularization? J Am Coll Cardiol. 2012;60:191-192.

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