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Seven patients had chronic, unexplained, nonparoxysmal sinus tachycardia. The clinical, electrocardiographic, and electrophysiologic characteristics of these cases are described. In each case electrocardiographic and electrophysiologic observations suggested that tachycardia was nonparoxysmal and due to increased automaticity of the sinus node (or of an automatic atrial focus located very near the sinus node). The mechanisms of increased sinus node automaticity in these patients were explored using drugs affecting the autonomic nervous system. In each patient these studies suggested a defect in either sympathetic or vagal nerve control of resting heart rate, with or without an abnormality of intrinsic heart rate. Data are also presented on baroreceptor reflex arc function in these patients.

This is the first systematic study of the effects of ventricular premature beats on sympathetic nerve activity in humans. Microneurographic techniques were used to record efferent sympathetic activity from the peroneal nerve, and an intracardiac electrode catheter was used to introduce ventricular premature beats after every 6 to 10 sinus heartbeats. Studies were performed in eight patients, aged 22 to 74 years (mean 57), undergoing cardiac electrophysiologic studies. Three patients did not have apparent heart disease and five had coronary artery disease. During sinus rhythm, 19 to 93% (mean 42%) of heartbeats were followed by a pulse-synchronous burst of sympathetic activity. Provoked ventricular premature beats had obvious effects on this activity. Premature beats with coupling intervals less than 80% of sinus cycle length were consistently followed by a burst of sympathetic activity, and this activity was greater in amplitude, duration and area (all p less than 0.05) than were burst of such activity during sinus rhythm. The magnitude of this burst of activity increased as the coupling interval of the ventricular premature beat decreased (p less than 0.0001). In contrast, postextrasystolic beats were followed by nearly complete neural silence. These effects were seen in all patients regardless of baseline burst incidence and the presence or absence of heart disease. Total nerve activity per 10 heartbeats was 6,520 +/- 770 U during ventricular extrastimulation and 5,720 +/- 440 U during normal sinus rhythm (difference not significant). It is concluded that single ventricular premature beats provoke fluxes of muscle sympathetic nerve activity in humans, comprising surges of sympathetic activity larger than those occurring during sinus rhythm, followed by neural silence.

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SUMMARY 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 i 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.THE CLINICAL SIGNIFICANCE of a prolonged HV interval in patients with chronic bifascicular block has been controversial. Scheinman et al.1' 2 and Narula et al.3 reported a higher incidence of atrioventricular (AV) block and a higher mortality in patients with bifascicular block and prolonged HV interval than in those with a normal HV interval. On the other hand, in an early analysis of our data, we reported no significant differences in the short-term follow-up regarding risk of AV block and mortality in 119 patients with bifascicular block, comparing patients with normal and prolonged HV intervals.4 McAnulty and co-workers confirmed our findings.'To resolve this controversy, we analyzed our experience in our series of patients with chronic bifascicular block. In this study, we examine and compare clinical, electrocardiographic and electrophysiologic variables in bifascicular block patients with normal and prolonged HV intervals. We also report prospective observations concerning life history of these patients to determine the prognostic significance of the HV interval.Our Circulation 64, No. 6, 1981No. 6, . 1265 believe that our data can be reconciled with previous data concerning the significance of the HV interval in patients with chronic bifascicular block. Materials and MethodsDefinitions are based on the recommendations of the Criteria Committee of the New York Heart Association.6 The criteria for electrocardiographic diagnosis of r...

SUMMARY This report details our experience with documented chronic second-degree atrioventricular (AV) nodal block (proximal to His [H] ) in 56 patients. Forty-six men (82%) and 10 women (18%), ages 18-87 years, were studied. Nineteen of the patients (34%) had no organic heart disease (including seven trained athletes) and 37 (66%) had organic heart disease. ECGs in all patients demonstrated episodes of type I seconddegree block; five patients also had periods of 2:1 block. Prospective follow-up of patients with no organic heart disease (157-2280 days, mean 1395 636 days) revealed one patient with clear indication for permanent pacing because of bradyarrhythmic symptoms (permanently placed on day 220 of follow-up). Two patients died nonsuddenly.In patients with organic heart disease (prospective follow-up of 60-2950 days, mean 1347 ± 825 days), pacemakers were implanted in 10 patients, primarily for treatment of congestive heart failure in eight and syncope in two. Sixteen patients died three suddenly, seven with congestive heart failure, two of an acute myocardial infarction and four of causes unrelated to cardiac disease.In summary, chronic second-degree AV nodal block has a relatively benign course in patients without organic heart disease. In patients with organic heart disease, prognosis is poor and related to the severity of underlying heart disease.SECOND-DEGREE atrioventricular (AV) nodal block is most often recognized in the acute clinical setting, complicating inferior wall myocardial infarction, digitalis intoxication, acute myocarditis or recovery after open heart surgery.' In such circumstances, second-degree AV nodal block is usually reversible with time, and usually plays no major role in determining clinical outcome.Chronic second-degree AV nodal block is also seen in a variety of circumstances.2-1 Although generally it is considered a benign conduction defect,12 13 few systematic data have been reported. In this report, we describe our experience in 56 consecutive patients with chronic second-degree AV nodal block and report clinical, electrocardiographic and electrophysiologic findings. We also report the follow-up data and summarize the clinical significance of chronic seconddegree AV nodal block. No. 5, 1981. crease in PR or AH intervals from the first conducted beat of a sequence to that of the last conducted beat before the dropped beat." Type II block was defined as an episode of second-degree block with no measurable increase in PR from the first to the last conducted beat of a sequence. Two-to-one (2:1) block was not classified by type. Patterns of left and right bundle branch block were diagnosed using standard electrocardiographic criteria.'5 The duration of the QRS complex was considered narrow when less than 0.12 second and was considered wide when at least 0.12 second. Patient SelectionFifty-six consecutive patients with chronic seconddegree AV nodal block were detected, studied and followed between January 1970 and March 1980. Approximately 50% of patients were detected within...