Digoxin did not reduce overall mortality, but it reduced the rate of hospitalization both overall and for worsening heart failure. These findings define more precisely the role of digoxin in the management of chronic heart failure.

Clinical and experimental observations in which bundle branch block patterns (BBBP) in ECG leads were normalized by distal His bundle (H) pacing are reported. The clinical material includes four patients with acute right BBBP secondary to anterior wall myocardial infarction and three patients with chronic left BBBP. Six of the seven patients had a prolonged H-V interval (60-85 msec) including three who showed evidence of an intra-H conduction delay (IHCD) with split H (H and H'). Distal H pacing from a right-sided electrode catheter normalized the BBBP with a stimulus-to-QRS (PI-V) interval 20-35 msec shorter than the H-V interval and almost identical to the H'-V interval in the three patients with documented IHCD. In 18 dogs ligation of the anterior septal artery resulted in IHCF with split H associated with right or left BBBP. Distal H pacing from catheter and/or plunge wire electrodes normalized the BBBP in 12 experiments (67%) with a PI-V interval identical to the H'-V interval. H pacing was selective and direct stimulation of myocardium was excluded by monitoring the high ventricular septal electrogram. The clinical and experimental observations are discussed as evidence that functional longitudinal dissociation is probably only operative in the pathologic H due to selectively greater depression of conduction in the transverse interconnections.

SUMMARY A 58-year-old man with hypertensive cardiovascular disease and atrial flutter underwent electrophysiologic studies, including multiple intra-atrial recordings and atrial stimulation. Although the surface ECG suggested the presence of atrial flutter, intra-atrial recordings demonstrated the presence of (1) sinus-like rhythm localized to an area of approximately 5 mm in and around the region of the sinus node, which was protected by entrance block; (2) flutter and/or fibrillation of the remaining parts of the right atrium; (3) fibrillation of the left atrium; and (4) transient degeneration of flutter into fibrillation at right atrial sites, with predominant flutter activity. Although a major part of the right atrium was in flutter and/or fibrillation, we could assess sinus node function by overdrive stimulation of the area of sinus node activity. Sinus node function studies revealed an underlying sick sinus syndrome.THE DIAGNOSIS of atrial arrhythmias is essentially based on the analysis of the configuration, timing, and rate of P waves on the surface ECG. However, recent studies in selected patients have demonstrated dissimilar atrial rhythms with direct intra-atrial recordings otherwise not discernible on the surface ECG."3 In this paper we report the electrophysiologic findings in a patient in whom the ECG revealed atrial flutter and intra-atrial recordings demonstrated the presence of sinus-like rhythm in and around the region of the sinus node, flutter and/or fibrillation of the remaining parts of the right atrium and fibrillation of the left atrium. We also assessed sinus node function, although a major part of the right and left atria were in flutter and/or fibrillation. Assessment of sinus node function revealed an underlying sick sinus syndrome.Case Report A 58-year-old man with hypertensive cardiovascular disease was admitted to the Medical Service of the Brooklyn Veteran's Administration Medical Center for uncontrolled hypertension, congestive heart failure and atrial flutter of recent onset. A 12-lead ECG suggested the presence of atrial flutter at a rate of 240 beats/min, with a ventricular response of 120 beats/min and poor R-wave progression from V1 to V3 ( fig. 1). Chest x-ray film showed cardiomegaly and pulmonary congestive changes. Echocardiogram revealed left atrial and left ventricular enlargement. The patient's hypertension and congestive heartfailure responded promptly to medical therapy. He was then referred to the cardiology service for elective electrical conversion of the atrial flutter after medical conversion with digitalis and quinidine had failed. Electrophysiologic StudiesThe patient underwent electrophysiologic studies to convert the atrial flutter by overdrive atrial stimulation. The procedure was explained to the patient, who gave signed consent. The electrophysiologic studies were performed after withholding digitalis and quinidine for 2 days. Serum digoxin level was 0.5 ng/ml on the day of the study. Two quadripolar #6FUSCI catheters with 10-mm interelectrode distance ...

Both sustained and nonsustained ventricular tachycardias were reproducibly induced in dogs 3 to 5 days after ligation of the left anterior descending coronary artery. Isochronal maps of ventricular activation were constructed from close bipolar electrograms recorded from the entire epicardial surface and selected intramural sites by a computerized multiplexing technique. The electrophysiologic data were correlated with the anatomic characteristics of the infarction. The induced tachycardias were due to reentrant activation in the surviving epicardial layer overlying the infarction. Cooling or cryoablation was applied to localized epicardial sites along the reentrant circuit to reversibly or permanently interrupt reentrant activation. The reentrant circuit could be consistently interrupted when cooling or cryoablation was applied to the distal part of the common reentrant wave front proximal to the site of earliest reactivation. Localized cooling of the site of earliest reactivation usually failed to interrupt reentry because the common reentrant wave front reactivated other sites close to the original reactivation site. Before interruption of reentry, cooling resulted in characteristic changes in conduction of the reentrant wave front. The study (1) fulfills Mines' criteria that circus movement reentry is the mechanism of the induced rhythms in this canine experimental model and (2) identifies the critical site along the reentrant circuit at which cryothermal ablation (or surgical interruption) of reentrant activation could be successfully accomplished.Circulation 68, No. 3, 644-656, 1983. WE HAVE SHOWN that ventricular arrhythmias induced by programmed stimulation in dogs 1 to 5 days after infarction are due to reentrant circuits located in the surviving, although electrophysiologically abnormal, thin epicardial layer overlying the infarction. 1 2 These electrophysiologic-anatomic correlative studies provide strong evidence for circus movement reentry. However, to establish the mechanism as reentrant, the reentrant circuit should be interrupted at one point to produce termination of reentrant activation.3 The present study was conducted to fulfill Mines' criteria for proving the presence of circulating excitation and to identify the critical site along the reentrant circuit at which interruption of reentrant activation could be successfully accomplished. For MethodsIn 18 mongrel dogs weighing 15 to 20 kg the left anterior descending coronary artery was ligated just distal to the anterior septal branch. Details of the surgical technique have been described.4 The dogs were reanesthetized with sodium pentobarbital (30 mg/kg iv) 3 to 5 days after coronary artery ligation and received supplemental doses as required. Each animal was ventilated with room air through an endotracheal tube with a Harvard positive pressure pump, and in each a jugular vein was cannulated for the administration of fluids. Electrocardiographic lead II and femoral blood pressure were continuously monitored on an Electronics for...

The AFFIRM Study enrolled 4060 predominantly elderly patients with atrial fibrillation to compare ventricular rate control with rhythm control. The patients in the AFFIRM Study were representative of patients at high risk for complications from atrial fibrillation, which indicates that the results of this large clinical trial will be relevant to patient care.