Electrocardiographic correlates of pacing induced cardiomyopathy and response to cardiac resynchronization therapy.
BACKGROUND: Chronic right ventricular (RV) pacing (RVP) causes pacing-induced cardiomyopathy (PICM) in only a small number of patients. We evaluated ECG correlates of (i) PICM and (ii) response to cardiac resynchronization therapy (CRT) upgrade. METHODS: We conducted a retrospective case-control study by including all CRT upgrades for PICM (LVEF <50%) at our center between 2014 and 2018. Controls were patients with ≥5 ECGs all demonstrating RVP over ≥2 years and all echocardiographic LVEF ≥50%. Root-summed-squared (3D) ECG was obtained from reconstructed vectorcardiographic X-Y-Z leads. Predictors of PICM and CRT response were assessed as area under ROC curve (AUC) for pre-CRT and Δ (post-CRT - pre-CRT) ECG intervals and QRS voltage-time-integrals (VTI). RESULTS: We included 104 patients with CRT upgrade for PICM (age 73.7 ± 10.5 years, female 29.1%, QRS duration 167.8 ± 25.2 ms, LVEF 28.8 ± 8.0%, ΔLVEF 13.8 ± 10.3%) and 178 controls without PICM (age 73.2 ± 14.9 years, female 52.8%, QRS duration 144.0 ± 20.9 ms, LVEF 56.7 ± 5.2%). PICM was best identified by VTIQRS-3D (AUC 0.851; VTIQRS-3D ≥ 80 μVs sensitivity 87.5%, specificity 63.5%), VTIQRS-Y (0.846), and QRS duration (0.775). CRT response (LVEF increase ≥10% at 3-12 months) occurred in 73/104 (70.2%) patients. Lack of CRT response was best predicted by longer pre-CRT QRS duration (AUC 0.640; QRS duration ≥180 ms sensitivity 45.2%, specificity 83.6%), and less ΔVTIQRS-3D (0.609) and ΔVTIQRS-X (0.608). CONCLUSION: In patients with chronic RVP, VTIQRS-3D ≥ 80 μVs can be used as a screening test for echocardiographic confirmation of PICM. RV-paced QRS duration >180 ms, on the other hand, identifies those who may not respond to CRT upgrade.