Assessment of poststress left ventricular ejection fraction by gated SPECT: comparison with equilibrium radionuclide angiocardiography.

PURPOSE: We compared left ventricular (LV) ejection fraction obtained by gated SPECT with that obtained by equilibrium radionuclide angiocardiography in a large cohort of patients. METHODS: Within 1 week, 514 subjects with suspected or known coronary artery disease underwent same-day stress-rest (99m)Tc-sestamibi gated SPECT and radionuclide angiocardiography. For both studies, data were acquired 30 min after completion of exercise and after 3 h rest. RESULTS: In the overall study population, a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.82, p<0.0001) and after stress (r=0.83, p<0.0001). In Bland-Altman analysis, the mean differences in ejection fraction (radionuclide angiocardiography minus gated SPECT) were -0.6% at rest and 1.7% after stress. In subjects with normal perfusion (n=362), a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.72, p<0.0001) and after stress (r=0.70, p<0.0001) and the mean differences in ejection fraction were -0.9% at rest and 1.4% after stress. Also in patients with abnormal perfusion (n=152), a good correlation between the two techniques was observed both at rest (r=0.89, p<0.0001) and after stress (r=0.90, p<0.0001) and the mean differences in ejection fraction were 0.1% at rest and 2.5% after stress. CONCLUSION: In a large study population, a good agreement was observed in the evaluation of LV ejection fraction between gated SPECT and radionuclide angiocardiography. However, in patients with perfusion abnormalities, a slight underestimation in poststress LV ejection fraction was observed using gated SPECT as compared to equilibrium radionuclide angiocardiography.

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 > or = 2 severely dysfunctional segments with preserved tracer uptake (> or = 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). 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.

Stress cardiac single-photon emission computed tomographic imaging late after coronary artery bypass surgery for risk stratification and estimation of time to cardiac events.

OBJECTIVE: We assessed predictors and temporal characteristics of cardiac risk in patients undergoing stress single-photon emission computed tomography after coronary artery bypass grafting. METHODS: Stress cardiac tomography was performed in 362 patients 5 years after coronary artery bypass grafting. Cardiac death and myocardial infarction were considered as events. Cox proportional hazards analysis was used to identify predictors of events and parametric survival analysis to predict time to events. RESULTS: During a median follow-up of 27 months, 22 cardiac events occurred (6.1% cumulative event rate). At multivariable Cox analysis, ischemia at cardiac tomography (hazards ratio 3.7, 95% confidence interval 1.5-9.1; P = .004), and diabetes (hazards ratio 3.6, 95% confidence interval 1.5-8.5; P = .006) resulted in independent predictors of events. Event-free survival was 96% in patients with normal cardiac tomography, 86% in those with abnormal tomography without ischemia, and 70% in those with (log-rank 10.6, P for trend = .008). The parametric survival model revealed that the cardiac risk was greater for all time intervals and accelerated more over time in patients with ischemia than in those without (chi(2) 21.4, P < .0001). Patients without diabetes and normal cardiac tomography remained below a defined risk level (5%) for the entire follow-up period. CONCLUSION: Stress cardiac tomography performed 5 years after coronary artery bypass grafting is useful to characterize the risk of cardiac events and its temporal variation. Parametric survival model estimates the predicted time to risk and the level of risk at specific time intervals after coronary artery bypass grafting.

Single-photon emission computed tomography after nitrate administration predicts cardiac events in patients with previous myocardial infarction and left ventricular dysfunction.

BACKGROUND: We determined the impact of viability assessment by nitrate single-photon emission computed tomography (SPECT) on cardiac events during long-term follow-up in patients with previous myocardial infarction, impaired left ventricular (LV) function, and no evidence of inducible ischemia. METHODS AND RESULTS: Sestamibi SPECT after nitrate was performed in 93 medically treated patients with previous myocardial infarction and LV dysfunction (ejection fraction < 40%). Viability was defined as > or = 2 dysfunctional segments with preserved tracer uptake (> or = 55% of peak activity). Cardiac events were cardiac death, myocardial infarction and late revascularization. Sixty-five (70%) patients had evidence of viability at SPECT, whereas 28 (30%) did not. During 43 +/- 24 months of follow-up, cardiac events occurred in 32 (49%) of the 65 patients with viability and in 5 (18%) of the 28 patients without (P < .001). At Cox analysis, only the extent of viability predicted cardiac events (hazards ratio 1.6, 95% CI 1.3-2.0, global chi-square 14.3, P < .0001). Cumulative probability of event-free survival was 22% in patients with viability and 81% in those without (P < .001). CONCLUSIONS: The presence of viable myocardium at nitrate SPECT imaging predicts major cardiac events at long-term follow-up and the risk increases with the extent of viability.

Estimation of coronary flow reserve by sestamibi imaging in type 2 diabetic patients with normal coronary arteries.

BACKGROUND: We assessed coronary flow reserve (CFR) by sestamibi imaging in patients with type 2 diabetes without coronary artery disease and normal coronary vessels. METHODS AND RESULTS: Dipyridamole/rest technetium 99m sestamibi imaging was performed in 33 patients with type 2 diabetes without a history of coronary artery disease and normal coronary vessels at angiography and in 12 control subjects. Myocardial blood flow (MBF) was estimated by measuring first-transit counts in the pulmonary artery and myocardial counts from tomographic images. Estimated CFR was expressed as the ratio of stress MBF to rest MBF. Rest MBF and CFR were corrected for rate-pressure product and expressed as normalized MBF and normalized CFR. At rest, estimated MBF and normalized MBF were not different in control subjects versus patients (0.98 +/- 0.4 counts x pixel(-1) x s(-1) vs 1.42 +/- 0.9 counts x pixel(-1) x s(-1) and 1.14 +/- 0.5 counts x pixel(-1) x s(-1) vs 1.61 +/- 0.9 counts x pixel(-1) x s(-1), respectively). Conversely, stress MBF was higher in control subjects than in patients (2.34 +/- 0.8 counts x pixel(-1) x s(-1) vs 1.55 +/- 0.8 counts.pixel(-1) x s(-1), P < .01). Thus estimated CFR was higher in control subjects than in patients (2.40 +/- 0.3 vs 1.36 +/- 0.8, P < .0001). After correction for the rate-pressure product, normalized CFR was still higher in control subjects than in patients (2.10 +/- 0.5 vs 1.28 +/- 0.8, P < .001). CONCLUSIONS: Sestamibi imaging may detect impaired coronary vascular function in response to dipyridamole in type 2 diabetic patients without a history of coronary artery disease and with normal coronary arteries.