Gated myocardial perfusion SPECT for evaluating left ventricular dyssynchrony in cardiac resynchronization therapy candidates: a systematic review

OBJECTIVES: Cardiac resynchronization therapy (CRT) is an intervention for heart failure patients with reduced ejection fraction who exhibit specific electrocardiographic indicators of electrical dyssynchrony. However, electrical dyssynchrony does not universally correspond to left ventricular mechanical dyssynchrony (LVMD). Gated single-photon emission computed tomography (SPECT) myocardial perfusion allows for the assessment of LVMD, yet its role in the CRT selection process remains debated. METHODS: We conducted a systematic literature review to critically evaluate the evidence for the prediction and prognostic utility of SPECT for LVMD in assessing LVMD among CRT candidates. The review adhered to PRISMA 2020 Statement criteria and included articles from PubMed, Embase, and Cochrane databases. The quality of evidence was appraised using the Grading of Recommendations, Assessment, Development, and Evaluation framework. RESULTS: From an initial pool of 1055 records, 33 met the inclusion criteria and provided original data on the predictive value of myocardial perfusion SPECT for LVMD. Most of them measured LVMD according to established recommendations, focusing on phase histogram bandwidth (HBW) and phase histogram standard deviation (PSD). Out of 2066 patients from 27 studies, 62% ( n = 1214) were qualified as CRT responders. Five studies reported SPECT-based cutoffs for predicting CRT response (HBW ranging 55°-152° and for PSD 20°-54°). Only five studies assessed the prognostic implications of baseline SPECT-measured LVMD, indicating that elevated baseline HBW and PSD values are associated with poorer outcomes. CONCLUSION: The objective and reproducible measurement of LVMD provided by SPECT underscores its potential as a valuable tool. Such assessment seems to be emerging as a promising adjunctive technique with potential to enhance CRT outcomes.