This paper reports a patient with Wolff-Parkinson-White syndrome who presented with a tachycardia showing an unusual QRS morphology closely resembling that of a ventricular tachycardia. On reversal to a normal rhythm the electrocardiogram showed changes of a type A preexcitation, with subsequent conversion to a type B pattern. This phenomenon was observed on two separate occasions. Such convers...

Using His bundle recordings and ventricular stimulation retrograde conduction was studied in 57 cases of complete AV block. VA conduction was observed in 13 patients. Of the 13, 12 had AV block distal to H, and during cardiac pacing 5 of them showed a retrograde His bundle potential. In all cases the AV node-His pathway was implicated in the transmission of the retrograde impulse. There was no ...

Atrioventricular conduction was studied in three patients, each representing a different grade of bilateral bundle-branch block. His bundle activity was recorded by a catheter technic. Two of the three patients had experienced Adams-Stokes attacks. The first patient had right bundle-branch block with left axis deviation at the time of catheterization. Increases in the atrial driving rate result...

An unusual patient is described in whom electrophysiological studies strongly suggest the occurrence of Mahaim conduction. The patient whose electrocardiogram previously showed a left anterior hemiblock pattern then developed advanced atrioventricular (AV) block (AH block). Beats conducted through the atrioventricular node always had a short HV interval (20 ms) and QRS complexes of left anterio...

Radiofrequency ablation is the interventional therapy of choice for the definitive cure of patients with tachycardias facilitated by accessory pathways. Ablation of an accessory pathway at sites close to the His bundle is inevitably associated with an increased risk of causing complete atrioventricular block. Here we describe the case of a patient with pre-excitation syndrome and episodes of su...

His bundle electrograms were performed in 4 patients illustrating the varied aspects of the preexcitation syndrome. In 3 cases of Wolff-Parkinson-White syndrome the QRS complexes were found to be formed by fusion between the normal and premature activation processes. In one of these cases a re-entry tachycardia was shown, with antegrade conduction occurring through the His bundle and retrograde...

Two patients who had an endocardial cushion type of ventricular septal defect underwent electrophysiologic studies for detection of specialized conduction tissue during operative repair. In one patient, with an inferior leftward frontal plane QRS axis on the ECG, we recorded an intraventricular His bundle electrogram anterior and superior to the ventricular septal defect. In the other patient, ...

The His bundle electrogram was recorded in I9 cases with P mitrale simultaneously with standard lead II, and compared with 30 cases with normal P waves. Internodal conduction time (P1A) interval did not differ in P mitralefrom the controlgroup, confirming that prolonged atrial activation in P mitrale represents a specific 'left atrial block'. The importance of this observation is discussed with...

Two patients who had an endocardial cushion type of ventricular septal defect underwent electrophysiologic studies for detection of specialized conduction tissue during operative repair. In one patient, with an inferior leftward frontal plane QRS axis on the ECG, we recorded an intraventricular His bundle electrogram anterior and superior to the ventricular septal defect. In the other patient, ...