We have studied four hearts in which enlargement of the ventricular membranous septum was associated with histological abnormalities of the atrioventricular conduction tissues. Two of the cases showed unusually formed penetrating and non-branching main atrioventricular bundles. These two cases plus one other also showed right-sided penetrating and main atrioventricular bundles. In addition thes...

Four hearts are described in which the right atrioventricular valve, draining a morphologically right atrium, straddled and overrode a septum between a right-sided chamber of left ventricular morphology and a left-sided chamber of right ventricular morphology. The degree of override varied between the straddling valve and was committed by 20-45% to the morphologically right ventricle. The ventr...

A patient with recurrent bouts of atrial fibrillation and wide-complex regular tachycardia underwent electrophysiologic studies. Premature atrial stimulation or atrial pacing during sinus rhythm resulted in gradual lengthening of the PR and AH intervals, narrowing of the HV interval and progressive preexcitation with a left bundle branch block and left-axis contour. Induction of tachycardia was...

SUMMARY Considerable controversy exists regarding the site(s) of origin of so-called junctional rhythms. However, experimental and clinical evidence indicates that a more precise identification of the origin of these rhythms is now possible. Microelectrode recordings from the atrioventricular (A-V) junction have clearly demonstrated that all three zones of the A-V node (upper nodal [AN], mid-no...

We describe a technique for interruption/modification of atrioventricular conduction using a direct current shock delivered from a defibrillator to the atrioventricular junctional tissue by means of a conventional electrode wire. The method was used in three patients with refractory supraventricular tachycardia. After the procedure two patients received an atrioventricular sequential pacemaker....

OBJECTIVE The molecular mechanisms that regulate the formation of the conduction system are poorly understood. We studied the developmental expression pattern and functional aspects of the T-box transcription factor Tbx3, a novel marker for the murine central conduction system (CCS). METHODS The patterns of expression of Tbx3, and of Cx40, Cx43, and Nppa, which are markers for atrial and vent...

Electrophysiological studies were carried out in 7 subjects with angiographically proven ventricular inversion in order to determine if this technique could be used in the study of arrhythmias in such subjects. Three subjects with normal PR intervals on the electrocardiogram had normal low right atrium to His (LRA-H) and His to ventricle (HV) intervals at rest. With atrial pacing, I of these 3 ...

OBJECTIVE In the heart, there are multiple supraventricular pacemakers involved in normal pacemaking as well as arrhythmias and the objective was to determine the distribution of HCN4 (major isoform underlying the pacemaker current, I(f)) in the atria. METHODS In the atria of the rat, the localisation of HCN4 and connexins was determined using immunohistochemistry, and electrical activity was...

observed that the sinus wave reached the AV node with a Introduction Atrioventricular septal defect (AVSD) can be associated with supraventricular arrhythmias and atrial fibrillation (AF). The position of the conduction system differs from the normal heart: the atrioventricular (AV) node is more posterior and inferior compared with the normal position in the triangle of Koch, in close relation ...

A34-year-old man presented for evaluation of palpitations. Eight years earlier, he had undergone orthotopic heart transplantation for nonischemic cardiomyopathy. During the electrophysiology study, atrial tachycardia (cycle length, 220 ms) originating in the recipient atrium was present at baseline. Atrioatrial conduction from the recipient atrium to donor atrium was present with 2:1 conduction...