Upgrading to cardiac resynchronization therapy: who truly reaps the benefits?

Right ventricular (RV) pacing can induce intraventricular desynchrony which, in nearly 30% of patients, results in left ventricular (LV) dysfunction and worsening heart failure (HF) within a few years after implantation. Cardiac resynchronization therapy (CRT) can reverse harmful effects of RV pacing, improving LV ejection fraction (LVEF) and reducing morbimortality. However, 20% to 40% of patients receiving CRT are classified as non-responders. Several clinical trials have reported some patients’ characteristics that increase the chance of response to CRT.

Finding variables that may predict the response to CRT within a year of CRT upgrade in a district Hospital.

Single-center, observational and retrospective study of patients with RV pacing systems and HF with reduced LVEF who underwent revision to CRT between January 2015 to June 2024. CRT response was defined as an increasement of ≥5% in LVEF and improvement of New York Heart Association (NYHA) functional class in ≥1 category. LVEF was measured pre-revision and 6-12 months post-upgrade.

We included 55 patients, 78% male, mean age 76±7.9 years. 64% had a double chamber PM and 20% an ICD. Mean % of RV pacing was 78±33%. The average time from initial device implantation to CRT revision was 8±2.6 years. All CRT procedures (CRT-D 76% and CRT-P 24%) were successful. The mean age at CRT upgrade was 73±7 years. HF etiology was ischemic in 30 (54%) patients. 27 (49%) had atrial fibrillation. All the patients were in NYHA II-III, with mean LVEF 29.1±6.7%. A successful response to CRT was achieved in 35 (64%) patients, with a mean ΔLVEF 10.7±8.9%. An improvement in NYHA functional class was seen in all patients with LVEF recovery, with 27 (49%) patients in NYHA I and 24 (44%) in NYHA II at 6-12 months.

Compared to those with ischemic cardiopathy, patients with non-ischemic cardiomyopathy had a significantly higher rate of response to CRT at 6-12 months (ΔLVEF: 14±9.9 vs 7.9±5.8, p=0.019). The same was verified for patients with age <70 years at time of revision, which had a significantly higher improvement of LVEF compared with older ones (ΔLVEF: 12.5±9.8 vs. 10±7.1, p=0.002). Moreover, patients with RV pacing ≥40% had a significantly higher rate of response to CRT at 6-12 months (ΔLVEF: 11.9±6.6 vs. 10±4.4, p=0.022).

In our population, gender, sinus rhythm, years between initial implant and revision or type of device were not predictors of CRT response during 6-12 months follow-up.

Device upgrade to CRT in patients with HF with reduced LVEF showed a significant rate of responders, with the greatest improvement observed in patients with a non-ischaemic etiology of HF, age <70 years at time of revision and higher percentage of RV pacing at baseline. These findings, derived from a district hospital setting, highlight the significant potential for CRT in real-world clinical environments, reinforcing the value of this programs in regional centers.