JACC: Can SPECT perfusion imaging predict sudden cardiac death?

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Among patients with coronary artery disease (CAD) and left ventricular ejection fraction (LVEF) greater than 35 percent, the extent of stress myocardial perfusion imaging (MPI) perfusion defects is associated with an increased risk of sudden cardiac death, according to a study published in the July 13 issue of the Journal of the American College of Cardiology. However, an accompanying editorial questions whether the study's design is equipped to make this conclusion.

Most victims of sudden cardiac death have an LVEF greater than 35 percent. Jonathan P. Piccini, MD, from the division of cardiology, department of medicine at Duke University Medical Center in Durham, N.C., and colleagues studied a population of 4,865 patients with CAD and LVEF greater than 35 percent who underwent gated SPECT MPI.

Researchers used Cox proportional hazard modeling to examine the relationship between patient characteristics and sudden cardiac death. The median age of the population was 63 years, and the median LVEF was 56 percent. The median follow up for all patients was 6.5 years. During follow up, there were 161 sudden cardiac deaths (3.3 percent).

The addition of perfusion data to the clinical history and LVEF was associated with increased discrimination for sudden cardiac death events. After multivariable adjustment, LVEF, the Charlson index, hypertension, smoking, antiarrhythmic drug therapy and the summed stress score were associated with sudden cardiac death, according to the authors.
SPECT perfusion imaging adds incremental prognostic information to the clinical history for the prediction of sudden cardiac death, concluded Piccini and colleagues. Further validation of these findings and prospective studies should address the role of SPECT perfusion imaging for the risk stratification of sudden cardiac death in patients with CAD and LVEF greater than 35 percent, the authors added.

“It is interesting to note that the summed difference score was not predictive of sudden cardiac death, suggesting that the presence of at least some scar tissue is required to place the patient within the high-risk group. This is supported by the observation within the paper that the summed stress score remains predictive of sudden cardiac death even when adjusted for revascularization,” noted Robert J. Myerburg, MD, professor of medicine and physiology in the cardiovascular division at the University of Miami Miller School of Medicine in Miami, in an accompanying editorial.

“The current study should be viewed primarily as hypothesis-generating, given its cross-sectional nature and susceptibility to unintended bias,” commented Myerburg.