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His bundle electrograms in patients with congestive cardiomyopathy
Insights
His bundle electrograms reveal previously undetected atrioventricular conduction abnormalities in patients with congestive cardiomyopathy. These findings expand understanding of the electrophysiologic characteristics of this condition.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Congestive cardiomyopathy (CCM) can affect cardiac conduction.
- Standard electrocardiography (ECG) may not fully reveal underlying conduction disturbances.
Purpose of the Study:
- To investigate atrioventricular (AV) conduction abnormalities in patients with CCM using His bundle electrograms.
- To correlate electrophysiologic findings with standard ECG and clinical presentation.
Main Methods:
- His bundle electrograms were recorded at rest and during atrial pacing in 16 CCM patients.
- Analysis included A-H intervals, H-V intervals, and intraventricular conduction times.
- Patients' medication, including digitalis, was noted.
Main Results:
- All patients showed progressive A-H interval prolongation with increased heart rate during pacing.
- Three patients on digitalis developed second-degree AV block (A-H block) at paced rates below 130/min.
- Conduction delays were identified proximal to, within, and distal to the His bundle, including left bundle branch block and isolated H-V prolongation.
Conclusions:
- His bundle electrography is crucial for detecting subtle AV conduction abnormalities in CCM.
- These abnormalities are more prevalent than suggested by standard ECG.
- Findings enhance the understanding of electrophysiologic derangements in congestive cardiomyopathy.
Abstract:
His bundle electrograms were obtained at rest and during atrial pacing in 16 patients with congestive cardiomyopathy. Increments in heart rate during atrial pacing were associated with progressive increases in the A-H interval in all patients. Three patients had abnormal conduction (prolonged P-H) proximal to the His bundle; atrial pacing resulted in second degree A-V block (A-H block) in these three patients at paced rates below 130/min; these three patients were on digitalis at the time of the study. Two patients ahd left bundle branch block associated with a prolonged H-V interval suggesting a conduction disturbance in the contralateral bundle system either at or distal to the branching portion of the His bundle. Two patients had H-V prolongation in the presence of a normal QRS duration which suggests delay in the bundle of His. Two patients with normal H-V intervals had marked prolongation of the total intraventricular conduction time (H-S prolongation). The His bundle electrogram uncovered abnormalities in atrioventricular conduction not apparent on the standard electrocardiogram and has allowed expansion of our knowledge regarding the electrophysiologic features of congestive cardiomyopathy.