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Significance of chronic bifascicular block without apparent organic heart disease
Insights
Patients with primary conduction disease (PCD) and chronic bifascicular block have fewer symptoms and lower mortality rates compared to those with organic heart disease (OHD). PCD patients experienced less severe cardiac events and had better long-term outcomes.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Chronic bifascicular block is a conduction abnormality that can be associated with underlying organic heart disease (OHD) or be primary conduction disease (PCD).
- Differentiating between PCD and OHD in patients with bifascicular block is crucial for prognosis and management.
Purpose of the Study:
- To compare the clinical characteristics, electrophysiologic findings, and long-term outcomes of patients with primary conduction disease (PCD) versus those with organic heart disease (OHD) presenting with chronic bifascicular block.
Main Methods:
- Retrospective analysis of 452 patients with chronic bifascicular block, identifying 86 with PCD (no clinically apparent OHD).
- Comparison of clinical variables, including symptoms and electrocardiographic findings, between PCD and OHD groups.
- Prospective follow-up for up to 2998 days to assess the incidence of atrioventricular (AV) block and cardiovascular mortality.
Main Results:
- PCD patients had significantly fewer symptoms (angina, dyspnea, congestive heart failure) and lower incidence of left bundle branch block and premature ventricular contractions compared to OHD patients.
- Mean AH and HV intervals were shorter in PCD patients, with a lower incidence of HV prolongation (21% vs. 41%).
- While overall AV block incidence was similar, spontaneous AV block was significantly lower in PCD patients (1% vs. 5%). Annual cardiovascular and sudden death mortality were significantly lower in the PCD group over 5-year follow-up.
Conclusions:
- Patients with primary conduction disease (PCD) and chronic bifascicular block exhibit a lower incidence of electrophysiologic abnormalities and reduced risk of spontaneous atrioventricular block.
- PCD is associated with significantly lower cardiovascular and sudden death mortality compared to OHD in this patient cohort.
- Clinical diagnosis of PCD may underestimate underlying OHD, as a small but definite risk of cardiovascular mortality persists.
Abstract:
Eighty-six of 452 patients (19%) with chronic bifascicular block were found to have no clinically apparent associated organic heart disease (OHD) and were defined as having primary conduction disease (PCD). Comparison of patients with PCD and OHD revealed a significantly lower incidence of the following clinical variables in the PCD patients (p less than 0.001): exertional angina, dyspnea, congestive heart failure, cardiomegaly, functional class I (all by study design), left bundle branch block and premature ventricular contractions. Both mean AH and HV intervals were significantly shorter in patients with PCD (p less than 0.01). The incidence of HV prolongation was 21% in PCD and 41% in OHD patients (p less than 0.001). All patients were prospectively followed for 21-2998 days with a mean +/- SEM of 1209 +/- 66 days for PCD and 1172 +/- 36 days for OHD. Atrioventricular (AV) block developed in three patients from the PCD group and 26 from the OHD group (NS), with spontaneous block occurring in one (1%) PCD patient and 19 (5%) OHD patients (p less than 0.05). Annual mortality due to sudden death as well as total cardiovascular mortality (including sudden death) for the 5-year follow-up was significantly lower in patients with PCD. Patients with PCD have significantly lower incidence of electrophysiologic abnormalities and subsequent spontaneous AV block as well as cardiovascular and sudden death mortality. The diagnosis of PCD based on clinical criteria probably underestimates the presence of underlying OHD, as suggested by a small but definite risk of cardiovascular mortality.