Evidence that AV nodal re-entrant tachycardia does not require participation of the entire AV node.

Electrophysiologic studies in a case of AV nodal re-entrant tachycardia showed that a programmed atrial premature depolarization induced during the tachycardia did not change the tachycardia cycle but caused a delay in the following atrial echo. Analysis of such a phenomenon suggests that the atrial premature depolarization was conducted to the upper part of the AV node but not to the site of the re-entry. Therefore, AV nodal re-entry can persist without the participation of the upper part of the AV node.

Indications for His bundle recordings.

While the extrapolation of data derived from His bundle studies performed over the past 10 years has lessened the need to apply the technique for diagnostic clinical purposes, His bundle recordings remain a useful clinical research tool for better understanding of cardiac electrophysiology. Some of the areas of continued research to which the technique will most certainly be applied are: (1) study of reentrant phenomena involving the atrial, junctional, and ventricular regions of the heart, (2) investigation of the mechanisms of action of new and old drugs on the heart, (3) evaluation of effectiveness of drug treatment in resistant cardiac arrhythmias, and (4) understanding of complex arrhythmias.

Congenital pulmonary artery branch stenosis: association with renal artery stenosis.

A patient had multiple bilateral stenoses of the pulmonary artery and its branches with systemic hypertension associated with mild stenoses of the renal arteries. Cardiac catheterization and angiocardiography are important in the evaluation of the degree of stenoses and pulmonary hypertension. This case suggests that in a child or young person with hypertension and a loud precordial murmur, lesions other than coarctation of the aorta may be present.

Multiple mechanisms of tachycardias in a patient with the Wolff-Parkinson-White syndrome.

In a patient with the Wolff-Parkinson-White Syndrome we observed atrial fibrillation and three distinct paroxysmal re-entrant tachycardias. Intracardiac electrograms obtained during the tachycardias showed the mechanisms to be A-V nodal, accessory pathway and sinus node re-entry. When P wave morphology, R-P relationship and QRS configuration are considered, it is illustrated how these four tachyarrhythmias may be successfully diagnosed on the surface electrocardiogram.

Effects of phenytoin on refractoriness and conduction in the human heart.

Using His bundle electrograms and the atrial (A2) and ventricular extrastimulus (V2) techniques, anterograde and retrograde refractory period studies were performed (in 9 and 12 patients, respectively) before and 10 min after intravenous infusion of phenytoin (DPH; mean plasma level, 17.3 micrograms/ml). DPH had no effect on the duration of the QRS complex or the H-V interval of the sinus beats; it had variable but insignificant effects on the sinus rates and the atrial, A-V nodal, and ventricular muscle refractoriness.

Modification and abolition of re-entry within the His-Purkinje system in man by diphenylhydantoin.

The phenomenon of macrore-entry (Re) within the His-Purkinje system (HPS) was consistently observed in 10 of 19 patients during retrograde refractory period studies. Effects of intravenous infusion of diphenylhydantoin (DPH) on Re were studied in these 10 patients 10 minutes after completion of infusion (mean plasma level equal to 17.0 microgram/ml).

The 1,2,3,4 phenomenon. Atrioventricular nodal gap in the dog.

This study confirms the facility with which the so-called 1,2,3,4 phenomenon can be reproduced in intact dog hearts. When a series of three atrial premature beats (A2, A3, A4) were delivered following a constant A1-A1 drive, we demonstrated a narrow zone of A1-A3 and A1-A4 intervals in which A4 conducted to the ventricles in the presence of A3 but not in its absence. We used His bundle and multiple atrial electrograms to produce the phenomenon in nine of 16 dogs.

Abnormal Q waves in Wolff-Parkinson-White syndrome. Incidence and clinical significance.

Between January 1970 and January 1975 the diagnosis of Wolff-Parkinson-White syndrome was entertained in 44 patients. Thirty-one (70%) of these patients had negative sigma-deflections (Q waves) on one or more electrocardiographic leads, thereby simulating a pattern of myocardial infarction (Mi). Fifteen patients (34%) were initially referred with an erroneous diagnosis of Mi based on the presence of Q waves.

Interventricular septal motion during preexcitation and normal conduction in Wolff-Parkinson-White syndrome: echocardiographic and electrophysiologic correlation.

Interventricular septal motion was studied by echocardiogram in 20 consecutive patients with documented Wolff-Parkinson-White (WPW) syndrome before and during electrophysiologic evaluation using His bundle recordings and pacing techniques. Characteristic abnormal interventricular septal motion was seen in 8 of 11 patients with type B WPW syndrome (groups I and II). All eight patients had electrocardiographic patterns consistent with an anomalous pathway located in the anterior right ventricular wall (group I).

Electrophysiologic effects of procainamide in subtherapeutic to therapeutic doses on human atrioventricular conduction system.

The effects of single intravenous infusions of 50 to 400 mg of procainamide on the functional properties of the atrioventricular (A-V) conduction system were studied in 36 patients and correlated with plasma concentrations. A 50 mg dose of procainamide resulted in a plasma concentration of less than 1.0 mug/ml and produced no electrophysiologic changes.

Electrophysiologic effects of tolamolol on atrioventricular conduction in man.

The electrophysiologic effects of tolamolol (UK-6558-01), a beta-adrenergic blocking agent, were studied in 13 patients by means of intracardiac electrograms and the extrastimulus method. Tolamolol (4 to 30 mg. intravenously) resulted in : (1) prolongation of sinus cycle length (SCL) in all patients (p less than 0.

Time dependent changes in the functional properties of the atrioventricular conduction system in man.

Time dependent changes in the electrophysiological properties of the atrioventricular conducting system (AVCS) were determined at two or more cycle lengths (CL) in 22 patients using bundle of His (H) electrograms, incremental atrial pacing and atrial extrastimulus method. The atrioventricular (A-H interval) and intraventricular (H-V interval) conduction times and refractory periods (RP) of the atrium, the A-V node (AVN) and His-Purkinje system (HPS) were measured during the control period, and repeat measurements were made after a 30 minute interval in eight patients (group A), after a 60 minute interval in nine (group B) and after 30 and 60 minute intervals in five (group C). No statistically significant changes from control values were seen after 30 and 60 minute intervals in any group in sinus rate, A-V nodal conduction time and the onset of A-V nodal Wenckebach block.

Echocardiographic manifestation of "false" mitral stenosis that was.

An unusual normal posterior direction of motion of the posterior mitral valve leaflet echo during diastole was detected in a patient whose clinical and hemodynamic data confirmed the presence of significant rheumatic mitral stenosis after other conditions causing echocardiographic pattern of "false" mitral stenosis were ruled out. The finding of normal direction of motion of the posterior mitral valve leaflet when associated with abnormal EF slope of the anterior mitral valve leaflet does not rule out the existence of significant mitral stenosis.

Induction of atrioventricular nodal reentrant tachycardia after atropine. Report of five cases.

After intravenous administration of 0.5 mg of atropine sustained atrioventricular (A-V) nodal reentrant tachycardia could be produced in five patients who had no prior historical or electrocardiographic evidence of supraventricular tachycardia. During the control period single atrial echo beats could be demonstrated in four of the five patients, but no instance of sustained tachycardia occurred.