Editorial

Role of regional myocardial dysfunction by gated myocardial perfusion SPECT in the prognostic evaluation of patients with coronary artery disease

Gated myocardial perfusion SPECT (GSPECT) is a major clinical tool, widely used for performing myocardial perfusion imaging procedures. In this review, we have presented the fundamentals of GSPECT and the ways in which the functional measurements it provides have contributed to the emergence of myocardial perfusion SPECT in its important role as a major tool of modern cardiac imaging. GSPECT imaging has shown unique capability to provide accurate, reproducible and operator-independent quantitative data regarding myocardial perfusion, global and regional systolic and diastolic function, stress-induced regional wall-motion abnormalities, ancillary markers of severe and extensive disease, left ventricular geometry and mass, as well as the presence and extent of myocardial scar and viability. Adding functional data to perfusion provides an effective means of increasing both diagnostic accuracy and reader’s confidence in the interpretation of the results of perfusion scans. Assessment of global and regional LV function has improved the prognostic power of myocardial perfusion SPECT and has been shown in a large registry to add to the perfusion assessment in predicting benefit from revascularization.

Cedars-Sinai’s approach to the automation of gated perfusion single photon emission computed tomography (SPECT) imaging is based on the identification of key procedural steps (processing, quantitation, reporting), each of which is then implemented, in completely automated fashion, by use of mathematic algorithms and logical rules combined into expert systems. Our current suite of software applications has been designed to be platform– and operating system–independent, and every algorithm is based on the same 3-dimensional sampling scheme for the myocardium. The widespread acceptance of quantitative software by the nuclear cardiology community (QGS alone is used at over 20,000 locations) has provided the opportunity for extensive validation of quantitative measurements of myocardial perfusion and function, in our opinion, helping to make nuclear cardiology the most accurate and reproducible modality available for the assessment of the human heart.

The aim of this study was to assess the prognostic value of quantitative gated technetium 99m tetrofosmin single photon emission computed tomography (SPECT) imaging in patients with left bundle branch block (LBBB).

We followed up 101 consecutive patients with LBBB using Tc-99m tetrofosmin gated SPECT imaging. The mean follow-up was 1.24 years (maximum, 2.48 years). Hard endpoints were all-cause death and acute myocardial infarction. Event-free survival curves were obtained. Optimal cutoff points for left ventricular (LV) volumes and LV ejection fraction (EF) to predict outcome were determined by receiver operating characteristic curve analysis. Of the patients, 94 had an abnormal study. Fifteen hard events occurred (thirteen deaths). Perfusion abnormalities were similar for patients with or without events. For LV function parameters, the survival curves were maximally separated when we used cutoff values of 160 mL or greater for end-diastolic volume (P = .019 and hazard ratio [HR] of 1.04 for hard events, P = .024 and HR of 1.04 for all-cause death), 100 mL or greater for end-systolic volume (P = .043 and HR of 1.04 for hard events, P = .062 and HR of 1.04 for all-cause death), and lower than 35% for LVEF (P = .013 and HR of 0.81 for hard events, P = .047 and HR of 0.81 for all-cause death).

By use of quantitative gated SPECT imaging, LBBB patients with an end-diastolic volume of 160 mL or greater, end-systolic volume of 100 mL or greater, or LVEF lower than 35% are at increased risk for subsequent cardiac events.