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HF-ACTION substudy: More severe resting perfusion abnormalities linked with lower event rates
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The degree and severity of resting myocardial perfusion defects was inversely related to the incidence of all-cause mortality and CV hospitalization in patients with NYHA Class II to IV HF symptoms.
Researchers for the nuclear substudy of the HF-ACTION trial included 240 patients with left ventricular dysfunction. Sum rest scores were obtained from 238 of these patients using gated single-photon emission CT. The primary substudy endpoint was a combination of all-cause mortality and CV hospitalization.
According to a Cox proportional hazards model based on 113 events occurring in 238 patients, the extent and severity of baseline perfusion abnormalities was a predictor of the combined endpoint (HR=0.98; 95% CI, 0.97-1.00). The researchers also reported, however, that a higher baseline sum rest score was associated with a lower risk for an event. The researchers explained the relationship by noting that the outcomes were driven by a small group of patients with ischemic cardiomyopathy.
Patients with high sum rest scores at baseline who had ischemia were more likely to experience the primary endpoint than those without ischemic cardiomyopathy who had similar sum rest scores (P=.008 for interaction). Perfusion abnormalities detected with gated SPECT imaging were also able to separate ischemic vs. nonischemic etiology of HF for sum rest score (29 vs. 6; P<.0001) and dyssynchrony (57 vs. 29; P<.0001), as well as for peak heart rate (117 vs. 127; P=.003) and heart rate reserve (47 vs. 54; P=.05).
“We believe that there is an inverse relationship between the degree and severity of resting perfusion abnormalities and mortality and CV hospitalization,” Salvador Borges-Neto, MD, a nuclear medicine specialist at Duke University Medical Center in Durham, N.C., said in his presentation. “We also believe that this finding is related to ischemic events leading to CV hospitalization (which were the driven outcomes in the study) in patients with less severe resting perfusion abnormalities. Those patients would very likely benefit from stress testing to disclose underlying ischemia.” – by Eric Raible
For more information:
- Borges-Neto S. LBCT II. Presented at: Heart Failure Society of America 13th Annual Scientific Meeting; Sept. 13-16, 2009; Boston.
The unusual finding here was that there was a higher event rate with a lower score, and these people probably represent those with a degree of hibernating myocardium that is still at risk. We cannot, however, disentangle that any further from the data at hand. If we could do a stress test, which was not done as part of the substudy, we would probably find a lot of inducible ischemia, but we just do not have that data, as Dr. Borges-Neto pointed out.
Among patients with nonischemic cardiomyopathy, the extent of scarring or fibrosis is associated with death and hospitalization events, confirming prior data from cardiac MRI studies. Among patients with ischemic cardiomyopathy etiology, the sum rest score alone is really an incomplete descriptor of the state of the myocardium. Both the extent of the infarct and the extent of inducible ischemia are really needed to assess risk.
– James E. Udelson, MD
Director of Nuclear Cardiology, Tufts-New England Medical Center