Gated SPECT MPI and CT venography fusion: A new approach for appropriate CRT-pacemaker lead placement?

Excerpt

Cardiac resynchronization therapy (CRT) is a disease-modifying therapy and has been shown to improve left ventricular ejection fraction (LVEF), reduce heart failure (HF) related hospitalization and decrease all-cause mortality in selected HF patients.1,2 CRT is currently recommended as a class IA indication in symptomatic HF patients with LVEF is ≤ 35%, sinus rhythm and a QRS duration ≥ 150 ms.3 However, one-quarter to one-half of the subjects who receive a CRT are “non-responders” and do not benefit from CRT device implantation.4,5 Suboptimal pacemaker lead positioning is one of the multifactorial factors associated with non-response to CRT.6 In general, pacing the posterolateral LV results in the best haemodynamic response.7 However, scar in the paced region seems to be associated with poor response to CRT.8 Speckle-tracking echocardiography and late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) have shown that LV CRT-pacemaker lead placement in viable segments with the latest mechanical activation is associated with acute haemodynamic response and better outcome. 9-12 Shetty et al. showed that it is feasible to acquire, overlay, and accurately register CMR-derived anatomical, scar, and dyssynchrony data to guide CRT device implantation.11 Unlike CMR, gated SPECT myocardial perfusing imaging (MPI) is widely available at relatively low costs. Therefore, gated SPECT MPI has been evaluated for optimal LV CRT-pacemaker lead positioning.13,14 Recently, Zhang et al. demonstrated in 79 patients that CRT response improved when LV CRT-pacemaker lead position was based on gated SPECT MPI [response was defined as a reduction of ≥ 15% in LV end-systolic volume (LVESV)].15 After excluding 11 patients with LV CRT-pacemaker pacemaker lead placement in apical of scarred segments, 75.6% of the patients with LV CRT-pacemaker lead position based on gated SPECT MPI (n = 41) responded to CRT while only 51.9% of patients where LV CRT-pacemaker lead position was not based on gated SPECT MPI (n = 27) showed CRT response (P = 0.043). Furthermore pacing in the recommended LV segments, identified using gated SPECT MPI, was associated with long-term prognosis. Over a median follow-up of 49 months, 4 patients died (9.8%) in the recommended group, 7 (25.9%) in the non-recommended group, and 5 (45.5%) in patients where the LV CRT-pacemaker lead was positioned in the apex or scar. There were 9 (22.0%) composite events (all-cause mortality or HF hospitalization) in the recommended group, 14 (51.9%) in the non-recommended group, and 7 (63.6%) in the apex or scar group. …