The potential role of gated myocardial perfusion SPECT imaging in patient selection for cardiac resynchronization therapy

Excerpt

Cardiac resynchronization therapy (CRT) is currently recommended in patients with wide QRS complex (≥120 ms), heart failure symptoms, and depressed left ventricular (LV) function (ejection fraction ≤ 35%) despite optimal medical therapy.1 Several randomized clinical trials provided evidence that in these patients CRT can improve symptoms, LV function, heart failure hospitalizations, and overall mortality.2-4 However, this beneficial effect is not homogenous among CRT recipients and previous studies have observed that a substantial group of patients who received CRT according to these selection criteria do not respond favorably to CRT.4-7 More importantly, there is no consensus on the definition of response to CRT, and both symptomatic improvement (in New York Heart Association functional class) and echocardiographic improvement (LV reverse remodeling, decrease in LV end-systolic volume, and increase in LV ejection fraction) have been used; when comparing these two definitions of CRT response, it appears that symptomatic improvement occurs more often than echocardiographic improvement,8 but that up to 30% of patients may not show significant improvement in symptoms and/or LV performance.4-7 …