Recording of diastolic slope with catheters during junctional rhythm in humans.

Abstract

Junctional diastolic slopes were recorded in 11 of 15 patients (73.3%) with junctional rhythm that occurred spontaneously, after intravenous administration of atropine (1 mg), or during carotid sinus massage. The diastolic slopes were recorded through a unipolar lead consisting of a terminal of an electrode catheter placed in the His bundle area paired with an indifferent terminal on the superior vena cava. The slope of these diastolic deflections averaged -0.18 ± 0.06 mV/sec (mean -+ SD). Overdrive atrial and ventricular stimulations were followed by slowing of the junctional rate and decrease in the diastolic slope. Strong negative correlations (r values from -.71 to -.95) were found between the junctional cycle lengths and the diastolic slopes after atrial or ventricular pacing. Carotid sinus massage decreased the junctional rate and the junctional diastolic slope, whereas atropine increased the junctional rate and the junctional diastolic slope. Since prolongation of junctional cycle lengths after atrial pacing did not depend on frequency of impulse penetration into the His bundle, we postulate that the junctional pacemaker responsible for the junctional rhythm in some of our patients was in the N region of the AV node. Application of this recording method should help in the identification and characterization of automatic junctional pacemakers. Circulation 69, No. 3, 485-491, 1984.DIFFERENTIATION between automatic and reentrant arrhythmias is frequently done in the electrophysiologic laboratory by evaluating the response of the rhythm to electrical stimulation. For example, overdrive suppression is considered a hallmark of an automatic rhythm caused by phase 4 depolarization. On the other hand, differentiation between triggered rhythm, a form of automatic rhythm, and reentrant rhythm cannot be made with certainty because both rhythms can be initiated and terminated by electrical stimuli. Phase 4 depolarization, a marker of automatic activity, can be extracellularly recorded from the junctional area in dogs with junctional rhythm.' In this article we describe application of this technique in patients with junctional rhythm. MethodsFifteen men with junctional rhythm were used for the study (table 1). Junctional rhythm in these patients was characterized as a rhythm with a P wave occurring within or immediately after the QRS complex and with a QRS configuration and HV interval identical to those during sinus rhythm or atrial pacing. The patients' ages averaged 66.7 + 10.9 years (mean + SD). Twelve patients had an underlying clinical diagnosis of sick sinus syndrome, two had junctional rhythm after treatment with digitalis and propranolol, and one had escape junctional rhythm associated with myocardial infarction of the inferior wall (table 1). Seven of the patients had a stable junctional rhythm during the study, five had a junctional rhythm after intravenous administration of 1 mg of atropine, and three had reproducible junctional rhythm during carotid sinus massage.Electrophysiologic studies were p...