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Background: Landmark reports have suggested that patients with QRS widening immediately after cardiac resynchronization therapy (CRT) experienced less frequently reverse left ventricular remodeling during follow-up., Objective: We sought to investigate the relationship between postoperative QRS widening relative to baseline and mortality in a prospective cohort of heart failure patients receiving CRT., Methods: A 12-lead electrocardiogram was recorded for 237 heart failure patients (New York Heart Association class II to IV, left ventricular ejection fraction ≤35%, and QRS width ≥120 ms) before and immediately after CRT device implantation. The relationships between QRS widening, all-cause and cardiovascular mortality, and echocardiographic response to CRT were studied., Results: During a median follow-up of 24 months, 39 patients died. Fifty patients (21%) experienced QRS widening after CRT [QRS(+) group]. During follow-up, all-cause mortality was higher in QRS(+) patients than in QRS(-) patients (36-month survival free from death 81% ± 7% vs 64% ± 16%; log rank, P = .029). After adjustment for important prognostic confounders, QRS(+) patients remained associated with an excess overall mortality (adjusted hazard ratio [HR] 2.67; 95% confidence interval 1.07-6.65; P = .035) and cardiovascular mortality (adjusted hazard ratio 3.63; 95% confidence interval 1.13-11.65; P = .03). QRS(+) patients were less frequent responders to CRT than were QRS(-) patients (20 [47%] vs 136 [83%]; P < .0001)., Conclusion: Postoperative QRS widening relative to baseline after CRT is associated with a considerable increased mortality risk during follow-up. Whether QRS narrowing should be achieved to optimize CRT placement, and thereby increase the rate of CRT responders and improve outcome, deserves further research., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

The aim of this study was to analyze the onset mechanisms of atrial tachyarrhythmias using a dedicated diagnostic system in 83 recipients of DDDR pacemakers implanted for standard clinical indications. The pulse generator was programmed in DDD mode, at 60 beats/min, and the diagnostic instrument was programmed to document atrial tachyarrhythmic episodes at rates >200 beats/min. Onset mechanism was defined as the combination of ambient rhythm and trigger. Various underlying rates and rhythms patterns, including tachycardia, increasing frequency of premature atrial complex (PAC), underlying heart rate increase, restart, and no specific underlying rhythm, and various triggers, including single, multiple, or short runs of PACs, sudden rate decrease, and sudden onset of atrial tachyarrhythmia were included in the combined classification. Atrial tachyarrhythmic episodes were documented on one follow-up interrogation in 48 of the 83 patients. The pacing indications consisted of high degree atrioventricular block in 19 patients, bradycardia-tachycardia syndrome in 22, and isolated sinus node dysfunction in 6 patients. The onset mechanisms of 318 episodes were recorded and analyzed. A variety of triggers were observed in 33 of the 48 patients, and 39 patients had various ambient rhythms. Among 20 documented onset mechanisms, the most common were increasing frequency of PAC + short runs (17%), no specific ambient rhythm + sudden onset (24%), and increasing frequency of PAC + sudden onset (12%). There were wide intra- and interpatient variations in onset mechanisms, suggesting that state-of-the-art pacemakers should represent versatile diagnostic tools and offer flexible pacing methods to refine the management of atrial tachyarrhythmias. (PACE 2003; 26:1336–1341). [ABSTRACT FROM AUTHOR]