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Complete heart block. Studies of atrial and ventricular pacemaker site and function
British Heart Journal
|November 1, 1975
Summary
Idiopathic chronic complete heart block patients show varied pacemaker function. Ventricular pacemaker assessment is key to predicting syncope risk and guiding pacing decisions, identifying a low-risk group potentially manageable without pacemakers.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Idiopathic chronic complete heart block presents a challenge in managing pacemaker dependency and syncope risk.
- Understanding the intrinsic cardiac conduction system's response to pharmacological stimuli is crucial for risk stratification.
Purpose of the Study:
- To evaluate atrial and ventricular pacemaker function in patients with complete heart block using isoprenaline.
- To compare pacemaker responses in heart block patients with normal controls to identify risk factors for syncope.
- To determine if pacemaker function assessment can differentiate patients requiring pacing from those who may be managed conservatively.
Main Methods:
- Studied 20 patients with idiopathic chronic complete heart block and 16 normal controls.
- Assessed atrial and ventricular pacemaker rate response to intravenous isoprenaline (5 μg/70 kg).
- Performed His bundle electrograms in 10 patients to characterize the block level.
Main Results:
- Reduced ventricular pacemaker response to isoprenaline was observed in 14 patients, strongly correlating with frequent syncopal attacks (11/14) and Adams-Stokes syncope (8/14).
- A low-risk asymptomatic group (5 patients) exhibited normal atrial and ventricular responses to isoprenaline, suggesting potential for conservative management.
- Bundle-branch block patterns were associated with reduced ventricular (9/9) and atrial (7/9) responses, indicating widespread conduction system disease.
Conclusions:
- Ventricular pacemaker function assessment is critical for evaluating syncope liability in complete heart block.
- Patients with Adams-Stokes syncope require pacing, while asymptomatic or mildly symptomatic individuals may benefit from comprehensive pacemaker function and site assessment.
- A subset of complete heart block patients may be identified as low-risk and potentially managed without a pacemaker after thorough evaluation.