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

Background. We 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 Results. One 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 5 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). Conclusions. In 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.