A study of heart block in man using His bundle recordings

The technique of recording His bundle electrograms in man by a tripolar electrode catheter was applied in a study of patients with first, second, and third-degree heart block. In all patients with first-degree heart block (congenital, acquired, or induced by atrial pacing), the delay in A-V conduction occurred proximal to the His bundle as evidenced by a prolonged P-H interval. The enhancement of A-V conduction (shortening the P-H interval) due to isoproterenol was qualitatively similar in the three forms of first-degree block. In cases of Wenckebach phenomenon the P-H interval progressively increased until a dropped beat occurred. The nonconducted P wave was not followed by a His deflection, indicating block proximal to the His bundle. Cases of 2:1 and 3:1 block occurring proximal to the His bundle were also studied. The usefulness of His-bundle recordings in the diagnosis of cases of complete and incomplete bilateral bundle-branch block is also demonstrated.

Catheter technique for recording His bundle activity in man

A technique for the routine recording of His bundle (H) activity in man using a bipolar or multipolar catheter is described. The recording catheter is inserted percutaneously, via the Seldinger method, into the right femoral vein and advanced fluoroscopically into the right atrium. Placement of the pre-formed curve at the catheter tip across the tricuspid valve in nine patients resulted in stable recordings of His bundle activity in successive cardiac cycles. Right atrial pacing resulted in progressive lengthening of the P-H interval with increasing frequency but the H to S-wave interval remained constant at all rates. Similar lengthening of the P-H interval was produced during atrial pacing when pressure was applied to the carotid sinus. The use of this recording technique in man will facilitate diagnostic interpretation of the electrocardiogram and can be used in various investigations of atrioventricular and intraventricular conduction in man.

Variations of aberrant ventricular conduction in man: evidence of isolated and combined block within the specialized conduction system. An electrocardiographic and vectorcardiographic study

Aberrant ventricular conduction (AbC) was produced in 52 subjects, including 14 normal volunteers, by the introduction of atrial premature beats through a transvenous catheter electrode. Simultaneous standard electrocardiograms and vectorcardiogams permitted detailed analysis of configuration. Multiple patterns of AbC were produced in 29 of 52 subjects. The general categories and their frequency were as follows: right bundle-branch block without significant axis shift from control, 31; right bundle-branch block with left axis deviation, 27; left axis deviation, 14; inferior axis deviation, six; right bundle-branch block with inferior axis deviation, seven; and complete left bundle-branch block, six. These patterns were believed to depend on the location of isolated or combined functional block in the major pathways of the specialized conduction system, which include the right bundle branch, common left bundle branch, anterior division of the left bundle branch, and posterior division of the left bundle branch. The present study has documented the general varieties of AbC, their relevance to clinical cardiology, and the varieties most likely to cause diagnostic difficulty.

Controlled heart rate by atrial pacing in angina pectoris. A determinant of electrocardiographic S-T depression

This study was undertaken with a consideration of the physiological relationship between myocardial oxygen consumption and heart rate. Atrial pacing was performed in 63 resting subjects, 36 of whom had been referred for evaluation of angina pectoris. Pacing at critical controlled heart rates evoked angina pectoris in six patients of this group with chest pain and, consistently and more frequently, produced significant S-T segmental depression in 28 patients as a manifestation of myocardial ischemia. The functional test employing controlled heart rates has several advantages over other stress tests. The use of the sole stress of controlled atrial tachycardia is a new technique which has provided relatively safe, reproducible results in the objective evaluation and investigation of myocardial ischemia.

Atrial fibrillation produced by atrial stimulation

Twenty-six episodes of atrial fibrillation and flutter-fibrillation, each lasting less than 23 sec, were recorded in three normal subjects during atrial pacing studies. The cause of these atrial arrhythmias was determined to be the result of stimulation within the atrial vulnerable period.