Feasibility of a Cardiac Magnetic Resonance Protocol for "off-on" Cardiac Resynchronization Therapy Evaluation.

Background: Cardiac resynchronization therapy (CRT) is a standard treatment for patients with heart failure and electrical dyssynchrony. Cardiac magnetic resonance (CMR) is the gold standard for assessing left ventricular (LV) function. However, the feasibility of using CMR with active CRT is still uncertain.

Purpose: To assess the feasibility of a CRT "off-on" protocol during CMR and measure the acute effects of CRT interruption on LV function.

Methods: Patients underwent CMR before (pre-CRT) and 6 months after (post-CRT) an MR-conditional CRT defibrillator implantation. The post-CRT scan included two complete sets of cine images, one with inactive (post-CRT) and one with active CRT (post-CRT), maintaining a continuous connection between device and programmer.

Results: Out of 29 enrolled patients, 8 (28%) had complete and analyzable post-CRT data. Unsuccessful procedures were attributed to connection problems between the CRT device and the programmer (n = 10), poor image quality (n = 7), and lack of patient cooperation (n = 4). LV ejection fraction significantly increased between pre-CRT scan (28.1%) and both post-CRT (37.9%; p = 0.046) and post-CRT CMR (35.0%; p = 0.037), with a nonstatistically significant trend toward decreased LV volumes. No adverse events or significant changes in device electrical parameters (including battery level) were detected during the post-CMR scan period.

Conclusion: A CRT "off-on" protocol during CMR studies can be safely executed in patients with an MR-conditional CRT defibrillator. However, technical improvements are needed to facilitate high-quality scans during active CRT. Favorable changes in LV function induced by CRT remodeling were not acutely reversed with the interruption of electrical therapy.