Myocardial perfusion imaging using gated SPECT in heart failure patients undergoing cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) by biventricular pacing is indicated in patients with severe heart failure and left bundle branch block who remain symptomatic despite optimal medical therapy. The relationship between baseline resting perfusion pattern and hemodynamic response to CRT has not been fully investigated. We tested the usefulness of perfusion gated SPECT for baseline evaluation and follow-up of these patients. Methods: In 20 patients, we performed gated SPECT before CRT and at the 3-mo follow up. Left ventricular (LV) ejection fraction (EF), end-diastolic (ED) and end-systolic (ES) volume indexes (VI), and wall motion score index (WMSI) were measured and compared with clinical outcome. Results: One patient died before follow-up. The 19 remaining patients were classified into 1 of 2 groups according to the presence (group A) or absence (group B) of a significant severe perfusion defect at baseline before CRT. At the 3-mo follow-up, 6 of 10 group A and 8 of 9 group B patients had an improvement in New York Heart Association class. In both groups, quality of life, 6-min walking distance, and WMSI significantly improved. In group A, no significant change was registered in LVEF, LVEDVI, or LVESVI. In group B, LVEF increased from 23.1% 8% to 27.1% 11% (P 0.03) and LVEDVI and LVESVI decreased from 159 70 mL to 135 68 mL (P 0.02) and from 127 67 mL to 104 65 mL (P 0.01), respectively. Conclusion: Perfusion gated SPECT appears useful to characterize and follow up candidates for CRT. Despite clinical improvement, patients with severe resting perfusion defects do not show significant improvement in LVEF or reduction in LV volumes. Key Words: heart failure; pacing; perfusion scintigraphy