Intermittent wide QRS during biventricular pacing? what is the mechanism?

Document Type

Conference Proceeding

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Publication Title

J Interv Card Electrophysiol


Background: QRS narrowing signifies electrical resynchronization after implanting a cardiac resynchronization therapy (CRT) device and 12 lead ECG isan important tool to assess appropriate biventricularpacing and to optimize programming. Objective: To highlight issues of LV pacing inhibition due to atrial activity sensing, importance of coronary sinus lead position and post implant ECG. Methods: N/A. Results: A 75-year-old male with hypertension, paroxysmal atrial fibrillation, AV block s/p dual chamber pacemaker (2 years) was evaluated for decompensated heart failure and acute renal dysfunction. His echocardiogram showed dilated left ventricle with EF of 12% compared to 58% prior to pacemaker implant. He underwent pacemaker upgrade to a biventricular ICD (Boston Scientific) due to suspected pacing induced cardiomyopathy. A quadripolar lead was implanted with difficulty in a high posterolateral venous branch (1E). ECG post implant showed intermittent widepaced QRS complexes which resembled RV only paced complexes (1B). Device interrogation revealed LV pacinginhibition due to left atrial sensing (1C) which resolved by lowering the sensitivity to 1.5 mV in the LV channel (1D). LV inhibition was also rectified by programming LVahead of RV during biventricular pacing. LV inhibition can also be corrected by turning off the LV sensing capability in Boston Scientific devices. Conclusion: This case highlights theimportance of ECG post CRT implant, nuances of coronary sinus lead implant close to atrioventricular groove and knowledge of manufacturer specific device sensing capabilities with possible ways to rectify LV pacinginhibition non-invasively.





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