Quantitative Methods for the Recognition of Atrioventricular Junctional Rhythms in Atrial Fibrillation

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Abstract
This paper describes a method of analyzing electrocardiograms that detects and identifies nonfibrillatory atrial, A-V junctional, and ventricular pacemakers in atrial fibrillation, measures the ventricular beat intervals produced by the detected pacemaker, and estimates the block between pacemaker and ventricle. The identification and measurements are made with a known degree of assurance which may be increased or diminished since it depends entirely upon the number of heart beats analyzed. By applying the method to 61 recordings of 31 patients, we detected 18 instances of A-V junctional tachycardia and escape rhythm of which only three had been identified by ordinary electrocardiographic interpretation. The procedure consists of recording the electrocardiogram on magnetic tape, reducing the contained information to certain displays, and testing statistically the hypotheses suggested by them. The displays employed are: (1) A plot of the duration or the reciprocal of the duration of successive electrocardiographic R-R intervals against elapsed time (tachogram); (2) a plot of the number of R-R intervals in the recording within each duration class against the duration of the class (interval histogram); (3) a plot of the number of beat-to-beat interval sequences formed by intervals with equal durations, successively diminishing durations, and durations representing multiples of a common time segment against the duration of the identifying interval of each sequence (sequence histogram); and (4) a graphic presentation of the averaged electrocardiographic presystolic potential. The paper also presents evidence that A-V junctional escape rhythm in atrial fibrillation is due to pathological A-V block and should be considered to be the result of digitalis excess when this drug is exhibited.