Quantitative assessment of cardiac mechanical dyssynchrony and prediction of response to cardiac resynchronization therapy in patients with nonischaemic dilated cardiomyopathy using gated myocardial perfusion SPECT.

OBJECTIVE: The aim of the study was to evaluate gated myocardial perfusion SPECT (GMPS) in the prediction of response to cardiac resynchronization therapy (CRT) in nonischaemic dilated cardiomyopathy patients. PATIENTS AND METHODS: Thirty-two patients (23 men, mean age 57.5±12.1 years) with severe heart failure, who were selected for CRT implantation, were prospectively included in this study. Patients with coronary heart disease and structural heart diseases were excluded. ⁹⁹mTc-MIBI GMPS and clinical evaluation were performed at baseline and 3 months after CRT implantation. In GMPS, first-harmonic fast Fourier transform was used to extract a phase array using commercially available software. Phase standard deviation (PSD) and phase histogram bandwidth (PHB) were used to quantify cardiac mechanical dyssynchrony (CMD). Left ventricular ejection fraction was evaluated.
RESULTS: At baseline evaluation the mean NYHA class was 3.3±0.5, left ventricular ejection fraction was 23.2±5.3% and mean QRS duration was 150.3±18.2 ms. PSD was 55.8±19.2° and PHB was 182.1±75.8°. At 3-month follow-up, 22 patients responded to CRT with improvement in NYHA class by more than 1 grade and in ejection fraction by more than 5%. Responders had significantly larger PSD (63.6±16.6 vs. 38.7±12.7°) and PHB (214.8±63.9 vs. 110.2±43.5°) compared with nonresponders. Receiver-operating characteristic curve analysis demonstrated 86% sensitivity and 80% specificity at a cutoff value of 43° for PSD and 86% sensitivity and 80% specificity at a cutoff value of 128° for PHB in the prediction of response to CRT.
CONCLUSION: Baseline PSD and PHB derived from GMPS are useful for prediction of response to CRT in nonischaemic dilated cardiomyopathy patients.