Walter D. Berkowitz

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.

Patterns of Atrioventricular Conduction in the Human Heart

Atrial, His bundle (H), and ventricular electrograms were recorded by an electrode catheter in unanesthetized man. Conduction time through the atrioventricular (A-V) conduction system was subdivided into A-V nodal (A-H interval) and ventricular specialized conduction system (H-V interval). The right atrium was driven at a constant rate and the pattern of A-V conduction of premature atrial test impulses was determined as they occurred progressively earlier in the cardiac cycle. In the type 1 response, conduction delay and block were limited to the A-V node only. The type 2 response was characterized by progressive conduction delay in both the A-V node and ventricular specialized conduction system with block occurring in several instances in the latter. In the type 3 response there was also a progressive delay in A-V nodal conduction time, and a sudden marked delay in conduction in the ventricular specialized conduction system. Conduction block occurred distal to the His bundle depolarization. The relevance of conduction delay and block in the different regions of the A-V conduction system to the full recovery time and the relative, functional, and effective refractory periods of A-V conduction are indicated.

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.

Study of atrioventricular conduction in man using electrode catheter recordings of His bundle activity.

The technique of recording electrograms of the His bundle, using a tripolar electrode catheter positioned across the tricuspid valve, was applied in a physiological study of atrioventricular conduction in man. Increasing the heart rate to 160 beats/min by right atrial pacing produced progressive prolongation of the P-H interval while the H-Q interval remained constant. At any given paced heart rate, digitalis caused a prolongation of the P-H interval. Isoproterenol and atropine markedly shortened the P-H interval at any given heart rate. Neither drug had any significant effect on the H-Q interval. Coupled premature atrial stimulation produced prolongation of the P-H interval alone when the resultant ventricular depolarization was normal, and prolongation of both the P-H and H-Q intervals when the resultant ventricular depolarization was aberrant.

Recording of Specialized Conducting Fibers (A-V Nodal, His Bundle, and Right Bundle Branch) in Man Using an Electrode Catheter Technic

Extracellular action potentials of the A-V node (N), His bundle (H), and right bundle branch (RB) were recorded in subjects with an electrode cardiac catheter which was fluoroscopically positioned across the tricuspid valve. The N potential is a slow diphasic wave occurring between the atrial electrogram (P) and the H potential. It is characterized by slurring or notching on the upstroke. The H potential, as previously described, is a biphasic or triphasic wave of 15 to 20-msec duration. The RB potential is a fast biphasic wave of 10 to 20-msec duration occurring between the H potential and the Q wave. During single atrial pacing and premature atrial stimulation, the A-V conduction delay could be localized to the N-H interval. Evidence suggests that during aberrant ventricular conduction of the right bundle-branch block type the impulse was blocked proximally in the right bundle. During concealed conduction the nonconducted impulse was completely blocked within the A-V node or the N-H interval.

The Effects of Propranolol on Cardiac Conduction

The effects of propranolol, 0.1 mg/kg given intravenously, on atrioventricular (A-V) conduction and intraventricular (IV) conduction were studied in eight patients. Atrial pacing was used to control the heart rate. His bundle electrograms were recorded, and the interval from the pacing impulse to the His bundle electrogram (P-H interval) was used as a measure of A-V conduction and the interval from the His bundle electrogram to the S wave (H-S interval) was used as a measure of intraventricular conduction. Propranolol significantly prolonged the P-H interval in every patient at all paced heart rates, and it had no effect on the H-S interval. In two patients propranolol prolonged the effective refractory period of the atrioventricular conducting tissue.In four dogs during His bundle pacing, propranolol (4 mg/kg iv) had no effect on intraventricular conduction as measured from the His bundle pacing spike to S wave (H-S interval). In two dogs with prolonged H-S intervals secondary to toxic doses of digitalis and procainamide, propranolol had no effect on IV conduction. It is concluded that propranolol prolongs A-V conduction and has no effect on IV conduction when administered to patients in clinically effective dosages. Propranolols effects on cardiac conduction can be explained on the basis of its capacity to produce beta-adrenergic blockade.

A Study of Atrioventricular Conduction in Man Using Premature Atrial Stimulation and His Bundle Recordings

In 20 subjects the effects of controlled premature atrial stimulation on atrioventricular conduction was studied using an electrode catheter technic for recording electrical activity of specialized conducting fibers. The least common type of response observed was that in which A-V conduction delay was limited only to the A-V nodal region (type A). This type of response was obtained whenever the conduction delay in the A-V nodal region increased in direct proportion to the prematurity of a propagated atrial impulse. It was characterized by a progressive prolongation in the P-H interval with ultimate failure of conduction occurring proximal to the His bundle. In type B response, conduction delay occurred in both the A-V nodal and His-Purkinje systems. The recording of a characteristic A-V nodal potential permitted the localization of A-V nodal delay to the N-H interval.

The use of His bundle recordings in the analysis of unilateral and bilateral bundle branch block.

Abstract His bundle electrograms were recorded in 26 patients with bundle branch block. The interval from the His bundle electrogram to the onset of ventricular activation (H-V) was used as an approximation of conduction time in the left bundle branch in patients with right bundle branch block and of conduction time in the right bundle branch in patients with left bundle branch block. The H-V intervals of patients with right bundle branch block were within the range of those noted in patients with “normal” ventricular activation. The average H-V interval of patients with left bundle branch block was 22 msec. longer than that of patients with right bundle branch block and there was no overlap of individual values. Two patients with alternating LBBB had shorter H-V values during “normal” ventricular activation. Normalization of a bundle branch block pattern by premature atrial stimulation resulted in a shortening of the H-V interval. Two of six patients with right bundle branch block and left axis deviation had prolonged H-V intervals suggesting disease of either the most proximal portion of the left bundle branch or of the posterior-inferior division. The longest H-V values were observed in two patients with prolonged P-R intervals and left bundle branch block suggesting delayed conduction in the right bundle branch. Type I second degree A-V block induced by atrial pacing resulted in blocked impulse transmission proximal to the H potential. In Type II second degree A-V block the cardiac impulse was blocked distal to the H potential presumably in the contralateral bundle branch. Concealed conduction with blocked impulse transmission in the distal portion of the right bundle branch was observed.

A Study of Atrioventricular Conduction in Atrial Fibrillation and Flutter in Man Using His Bundle Recordings

Seven patients with atrial fibrillation and six patients with atrial flutter were studied using the technic of His bundle recordings. All 13 patients received digitalis. In atrial fibrillation each QRS complex (except for premature ventricular beats) was preceded by a single His bundle deflection. Complete block distal to the His bundle was not observed. Thus, the zone of concealment could be localized to the region proximal to the His bundle. The clinical findings were confirmed in three animal experiments. In atrial flutter the nonconducted P waves were also blocked proximal to the His bundle. In atrial fibrillation aberrant ventricular beats were distinguished from premature ventricular beats by the presence of a preceding His deflection in the former and its absence in the latter.

The effect of diphenylhydantoin on atrioventricular and intraventricular conduction in man

Abstract The effects of DPH on atrioventricular and intraventricular conduction were studied in 13 patients using an electrode catheter technique for recording His bundle activity. DPH was found to enhance A-V conduction (i.e., shorten the P-H interval) over various paced heart rates. DPH did not prolong I-V conduction as measured by the H-Q interval.