Immuno-Electrophysiological Mechanisms of Functional Electrical Connections Between Recipient and Donor Heart in Patients With Orthotopic Heart Transplantation Presenting With Atrial Arrhythmias.

[Figure: see text].

His-Optimized Cardiac Resynchronization Therapy to Maximize Electrical Resynchronization: A Feasibility Study.

Background Cardiac resynchronization therapy (CRT) is an established therapy for patients with cardiomyopathy, left bundle branch block, and heart failure. His bundle pacing (HBP) may also improve clinical outcomes by narrowing QRS duration. The QRS narrowing by HBP may not always be optimal. The aim of the study was to determine if CRT could be optimized by sequential HBP followed by left ventricular (LV) pacing (His-Optimized CRT [HOT-CRT]) to maximize electrical resynchronization. Methods We attempted permanent HBP in 27 patients (left bundle branch block 17, intraventricular conduction defect 5, and right ventricular pacing 5) referred for CRT in addition to LV lead. HBP was followed by LV pacing at a delay equal to His-ventricular interval. QRS duration at baseline, during HBP, biventricular pacing, and HOT-CRT was measured. Echocardiographic parameters and New York Heart Association functional class were assessed at baseline and during follow-up. Results HOT-CRT was successful in 25 of 27 patients (age 72±15 years, men 23, ischemic 21). QRS duration at baseline was 183±27 ms and significantly narrowed to 162±17 ms with biventricular pacing ( P=0.003), to 151±24 ms during HBP ( P<0.0001), and further to 120±16 ms during HOT-CRT ( P<0.0001). During a mean follow-up of 14±10 months, LV ejection fraction improved from 24±7% to 38±10% ( P<0.0001), and New York Heart Association functional class changed from 3.3 to 2.04. Twenty-one of 25 patients (84%) were clinical responders while 23 of 25 (92%) showed echocardiographic response. Conclusions In this feasibility cohort, HOT-CRT resulted in improved electrical resynchronization. HOT-CRT may improve clinical and echocardiographic outcomes in advanced heart failure patients requiring CRT.

Paradoxical atrial undersensing by a dual chamber pacemaker during atrial fibrillation.

This report describes paradoxical atrial undersensing by a dual chamber pacemaker in a patient with paroxysmal atrial fibrillation. Atrial undersensing was present only when the device was programmed to a high sensitivity but sensing normalized when a lower sensitivity was programmed. This unusual response should be differentiated from the recently documented lock-in behavior of pacemakers delivering managed ventricular pacing.

Atrial gradient as a potential predictor of atrial fibrillation.

OBJECTIVES: We tested the utility and comparability of the atrial gradient and atrial ERP as early markers of electrical remodeling and a propensity to atrial fibrillation (AF). BACKGROUND: Pacing at physiologic rates from the left atrium alters the atrial gradient and is associated with atrial tachyarrhythmias. At these physiologic rates, there is no change in the atrial effective refractory period (ERP). METHODS: Sixty-one chronically instrumented mongrel dogs in complete heart block were paced from the left or right atrium at 400 to 900 bpm for 46 +/- 3 days. Dogs were monitored weekly and electrophysiologic studies conducted to determine changes in the atrial gradient, ERP, and rhythm. RESULTS: Rapid atrial pacing was associated with concordant decreases in atrial gradient, ERP, and occurrence of AF. Incidence of AF increased with increasing pacing rate. Although there ultimately was an equal incidence of AF with left atrial and right atrial pacing, the onset of AF occurred earlier with left atrial pacing. As expected, ERP decreased in both atria. Animals with long control ERP did not fibrillate. CONCLUSIONS: Rapid pacing induces changes in atrial gradient, which can be used as a noninvasive marker of electrical remodeling. AF is accompanied by decreases in atrial gradient and ERP, and the incidence is highest in dogs with short control ERP.