Significance of the HV interval in 517 patients with chronic bifascicular block

In January 1975, we reported results of a prospective follow-up study (mean 538±42 days) of 119 patients with chronic bifascicular block (BFB), and concluded that BFB patients with normal and prolonged HV (NHV and PHV) had a similar incidence of atrioventricular (AV) block and mortality. In this report, we update these findings in 517 patients with a follow-up of 21 days to 9.8 years (mean 3.4±0.2 years). Three hundred nineteen patients (61%) had NHV and 198 (39%) had PHV (>55 msec). The NHV and PHV groups were similar in regard to age (NHV vs PHV, 61±1 vs 62±1 years) and sex (80% male, 20% female vs 82% male and 18% female). The following were more common (p<0.05) in patients with PHV (percent of patients with finding in NHV vs PHV groups): angina (18% vs 27%), congestive failure (27% vs 42%), cardiomegaly (48% vs 66%), New York Heart Association functional class II-IV (34% vs 56%), premature ventricular complexes (20% vs 29%), and organic heart disease (OHD) (75% vs 85%). Spontaneous trifascicular block (TFB) developed in two patients (0.6%) with NHV and nine patients (4.5%) with PHV (p<0.05). Cumulative 7-year incidence of TFB was 3% with NHV and 12% with PHV (p<0.01). Seven-year cumulative cardiovascular mortality was 32% in NHV patients and 57% in PHV patients (p<0.005). In conclusion, PHV in patients with chronic BFB was associated with a greater incidence and severity of OHD, and higher total and sudden death mortalities. The risk of spontaneous TFB was small in patients with either NHV or PHV, although it was significantly higher in the latter.