Atrioventricular conduction defects in patients presenting with syncope and normal PR interval

Electrophysiological abnormalities in the transplanted human heart

Fourteen relatively long term survivors of cardiac transplantation underwent systematic electrophysiological evaluation and ambulatory electrocardiographic monitoring. Six patients had prolonged conduction intervals during sinus rhythm. Sinus node function could be assessed in all donor atria and in 10 recipient atria. Sinus node recovery times were prolonged in four of the donor atria and in six recipient atria. In the donor atria abnormalities of sinus node automaticity were invariably associated with abnormalities of sinoatrial conduction. Four patients showed functional duality of atrioventricular nodal conduction during programmed extrastimulation, but no patient developed re-entrant arrhythmia. During ambulatory electrocardiographic monitoring no pronounced tachyarrhythmias were recorded. Three patients showed abnormalities of sinus node impulse formation. All three patients had abnormal sinus node recovery times during their electrophysiological study. Long term survivors of cardiac transplantation have a high incidence of electrophysiological abnormalities. Abnormalities of donor sinus node function are probably of clinical significance. The clinical significance of abnormalities detected within the atrioventricular conduction system of the denervated heart remains to be elucidated.

Should this patient be paced? An indication for His bundle study: syncope, a normal P-R interval and a narrow QRS

This report describes a patient who presented with transient central nervous system symptoms of unknown etiology with an electro-cardiogram exhibiting a narrow QRS complex and normal. P-R interval. The decision to implant a permanent VII pacemaker was made on the basis of a His bundle study that revealed significant prolongation of the HV interval. The successful clinical outcome re-emphasizes the clinical usefulness of electrophysiological investigation in patients with syncope of undetermined etiology.

Disappearing His deflection. Electrophysiological evidence for conduction defect within the His bundle

A change in the voltage and character of the His bundle deflection following premature atrial stimuli was observed and analysed in 5 of 95 patients having intracardiac conduction studies because of AV conduction disturbances. Of these 5 patients, 3 had spontaneous block within the His bundle, 2 of them showing block in other segments of the conduction system. With increasing prematurity of programmed atrial stimuli, there was a progressive decrease in the voltage of the His deflection, followed by a split His deflection, and finally disappearance of the His deflection. The voltage of the His deflection was also reduced in sinus beats following spontaneous His bundle premature beats. Similarly, during atrial stimulation at increasing rates, the His deflection decreased in voltage, split, and finally disappeared, but when Wenckebach periods appeared the His deflection reappeared in the first paced beat after the dropped beat. The preceding H-H interval was the only electrophysiological variable consistently related to the changes in the His deflection. These changes in His deflection can be explained electrophysiologically as the result of a conduction disturbance within the His bundle. The clinical significance of the phenomenon is discussed. The occurrence of this phenomenon during a conduction study makes it difficult or even impossible to localise the AV block precisely.

An unusual form of the bradycardia-tachycardia syndrome: paroxysmal A-V block and ventricular tachycardia

An unusual case of alternating bradycardia-tachycardia, paroxysmal Mobitz II A-V block and ventricular tachycardia is described. The patient presented with a normal resting (control) electrocardiogram and intracardiac conduction times (A-H and H-V intervals). The clinical evaluation, electrophysiology, and importance of defining the cause of serious rhythm disturbances prior to therapy are discussed.

Chronic right bundle branch block and left posterior hemiblock. Clinical, electrophysiologic and prognostic observations

Twenty-one patients with long-term right bundle branch block and left posterior himiblock were studied electrophysiologically and then followed up prospectively. The group consisted of 19 men and 2 woman aged 61 +/- 2.7 years (mean +/- standard error of the mean). The majority of patients had either hypertensive cardiovascular disease (48 percent) or primary conduction disease (33 percent). Initial electrophysiologic studies revealed A-H intervals of 58 to 152 msec (mean 98 +/- 7.7) and H-V intervals of 40 to 80 msec (mean 52 +/- 2.1). Six patients (29 percent) had prolonged H-V intervals. The follow-up period ranged from 91 to 1,231 days (mean 671 +/-68). Three of 21 patients (14 percent) needed a permanent pacemaker after development of the following symptomatic conduction disease: sinoatrial block on day 3 of follow-up; second degree atrioventricular (A-V) block, site undetermined, on day 118; and second degree A-V block proximal to the His bundle on day 398. One patient died suddenly (on day 571), and two others died of noncardiac causes. In conclusion, combined right bundle branch block and left posterior hemiblock was associated with less trifascicular disease than reported previously. The clinical course of most of the patients was benign and the incidence of sudden death was relatively small. Symptomatic conduction disease occurred but could be definitely related to trifascicular disease in only one patient. These short-term data suggest that prophylactic pacemaker insertion is not routinely indicated in patients with chronic right bundle branch block and left posterior hemiblock.

[Clinical value of His bundle electrography (author's transl)]

Methodical problems, indication and clinical implication of His bundle electrography are discussed. In 200 successive patients undergoing His bundle electrography and atrial stimulation the indication was as follows: Intraventricular conduction defects in 24%, A-V block in 21%, sick sinus syndrome in 20%, preexcitation in 17%, and complex arrhythmias in the remaining cases. In 38% of the patients did the HBE prove to be of help by providing information not available after analysis of the surface ECG. In 22% this technique contributed essentially to the management of these patients. In spite of dificiencies of our knowledge of the basic mechanisms, specific therapy, and prognosis of various arrhythmias His bundle electrography is clinically useful in selected patients. Therefore, this method has become a routinely used clinical tool.