Incremental prognostic value of cardiac single-photon emission computed tomography after nitrate administration in patients with ischemic left ventricular dysfunction

Abstract

BackgroundWe evaluated the incremental prognostic value of viability assessment by nitrate single-photon emission computed tomography (SPECT) in patients with ischemic left ventricular (LV) dysfunction. Methods and ResultsOne hundred and sixty-four patients with previous myocardial infarction and LV dysfunction (ejection fraction 29% ± 15%) underwent two Tc-99m sestamibi SPECT studies, under control conditions and after sublingual nitrate administration, for evaluation of myocardial viability. In each patient, viability was defined as the presence of ≥2 severely dysfunctional segments with preserved tracer uptake (≥55% of peak activity). Cardiac death, myocardial infarction, and late (>2 months) revascularization were considered events. Follow-up was 98% complete at a mean period of 30 ± 24 months. At baseline SPECT, 119 (73%) patients had evidence of viable myocardium, while 45 (27%) did not. Of these latter patients, 18 (40%) had evidence of viability after nitrate administration. Cardiac events occurred in 58 (35%) patients. Cumulative probability of event-free survival was similar in patients with and without viability at baseline SPECT (log rank 0.3, P = NS), while it was lower in patients with viability at nitrate SPECT compared to those without (log rank 6.3, P < .01). The addition of nitrate SPECT data significantly improved the prognostic power of the model including clinical, functional, angiographic, and baseline SPECT data (P < .01). ConclusionsIn patients with previous myocardial infarction and LV dysfunction, nitrate SPECT imaging provides incremental prognostic information over those obtained from clinical, functional, angiographic variables, and baseline SPECT data.