Cardiac resynchronization therapy (CRT) reduces mortality and morbidity in selected heart failure (HF) patients, but up to one-third of patients are non-responders. Sum absolute QRST integral (SAI QRST) recently showed association with mechanical response on CRT. However, it is unknown whether SAI QRST is associated with all-cause mortality and HF hospitalizations in CRT patients. The study population included 496 patients undergoing CRT (mean age 69±10 years, 84% male, 65% left bundle branch block (LBBB), left ventricular ejection fraction 23±6%, 63% ischemic cardiomyopathy). Pre-implant digital 12-lead ECG was transformed into orthogonal XYZ ECG. SAI QRST was measured as an arithmetic sum of areas under the QRST curve on XYZ leads, and was dichotomized based on the median value (302mV*ms). All-cause mortality served as the primary endpoint. A composite of 2-year all-cause mortality, heart transplant, and HF hospitalization was a secondary endpoint. Cox regression models were adjusted for known predictors of CRT response. Patients with pre-implant low mean SAI QRST had an increased risk of both the primary (HR 1.8; 95%CI 1.01–3.2) and secondary (HR 1.6, 95% CI 1.1–2.2) endpoints following multivariable adjustment. SAI QRST was associated with secondary outcome in subgroups of patients with LBBB (HR 2.1 [95%CI 1.5-3.0]) and with non-LBBB (HR 1.7, [95%CI 1.0-2.6]). In patients undergoing CRT, pre-implant SAI QRST<302mV*ms was associated with an increased risk of all-cause mortality and HF hospitalization. After validation in another prospective cohort, SAI QRST may help to refine selection of CRT recipients.

Background In patients with cardiac resynchronization therapy (CRT), atrial fibrillation (AF) is associated with an unfavorable outcome and may cause loss of biventricular pacing (BivP). An effective delivery of BivP of more than 98% of all ventricular beats has been shown to be a major determinant of CRT-success. Methods At a Swedish tertiary referral center, data was retrospectively obtained from patient registers, medical records and preoperative electrocardiograms. Data regarding AF and BivP during the first year of follow-up was assessed from CRT-device interrogations. No intra-cardiac electrograms were studied. Kaplan-Meier curves and Cox-regression analyses adjusted for age, etiology of heart failure, left ventricular ejection fraction, left bundle branch block and NYHA class were performed to assess the impact of AF and BivP on the risk of death or heart transplantation (HTx) at 10-years of follow-up. Results Preoperative AF-history was found in 54% of the 379 included patients and was associated with, but did not independently predict death or HTx. The one-year incidence of new device-detected AF was 22% but not associated with poorer prognosis. At one-year, AF-history and BivP≤98%, was associated with a higher risk of death or HTx compared to patients without AF (HR 1.9, 95%CI 1.2–3.0, p = 0.005) whereas AF and BivP> 98% was not (HR 1.4, 95%CI 0.9–2.3, p = 0.14). Conclusions In CRT-recipients, AF-history is common and associated with poor outcome. AF-history does not independently predict mortality and is probably only a marker of a more severe underlying disease. BivP≤98% during first-year of CRT-treatment independently predicts poor outcome thus further supporting the use of 98% threshold of BivP, which should be attained to maximize the benefits of CRT.