Myocardial perfusion single photon emission computed tomography for the assessment of mechanical dyssynchrony.

Purpose Of Review: Assessment of left ventricular dyssynchrony is important in the selection of patients for cardiac resynchronization therapy (CRT). In this review, the role of nuclear imaging [particularly gated myocardial perfusion single photon emission computed tomography (GMPS)] for assessment of cardiac dyssynchrony is discussed. In addition, the role of positron emission tomography for evaluation of effects of CRT is addressed.

Recent Findings: Phase analysis of GMPS yields accurate information on left ventricular dyssynchrony, correlating well with left ventricular dyssynchrony as derived from tissue Doppler echocardiography. Preliminary studies have also demonstrated that left ventricular dyssynchrony derived from GMPS can predict response to CRT (for histogram bandwidth and phase standard deviation sensitivity/specificity was 70 and 74%, respectively). Moreover, GMPS provides information on the location and extent of viable and scar tissue, which is also important for response to CRT. Furthermore, positron emission tomography studies have enabled quantification of cardiac perfusion (glucose and oxidative) metabolism and efficiency before and after CRT.

Summary: GMPS can provide important information for patients who are considered for CRT. This technique permits assessment of left ventricular dyssynchrony and viability/scar tissue, which are important for response to CRT. Positron emission tomography imaging may have a role in evaluation of physiologic effects after CRT, including myocardial perfusion, metabolism and efficiency.