Temporal sequence of right and left atrial contractions during spontaneous sinus rhythm and paced left atrial rhythm.

The sequence of right and left atrial contractions was analysed in 8 patients during spontaneous sinus rhythm and paced left atrial rhythm. During sinus rhythm, the beginning or peak of the right atrial a wave invariably preceded the beginning or peak of the left atrial a wave by a median of 32 and 34 msec, respectively. During paced left atrial rhythm, the beginning or peak of the right atrial a wave regularly followed the beginning or peak of the left atrial a wave by a median of 96 and 92 msec, respectively. The inversion of the normal sequence of atrial contractions may be used to confirm the existence of a spontaneous left atrial rhythm which otherwise can only be suspected by questionable electrocardiographic criteria. The increased time interval between atrial contractions during paced left atrial rhythm supports the hypothesis of the existence of specialized conduction pathways in the atria. The electrocardiographic criteria for the differentiation of left atrial from coronary sinus and junc-tional rhythm were introduced by Mirowski, Neill, and Taussig (I963) and Mirowski (I966). Stimulation of the left atrium established that these criteria may be fallaciousgraphic analysis of atrial activity and intracardiac electrograms were not sufficient to determiine left atrial rhythm with certainty. Therefore, the existence of spontaneous left atrial rhythm remained debatable (James and Sherf, I971; Selman and Edelstein, I969). It can be assumed that during left atrial rhythm the left atrium contracts before the right, since during spontaneous sinus rhythm the inverse sequence appears. By analysing the sequence of right and left atrial contractions, the existence of a spontaneous left atrial pacemaker in a few cases could be strongly The purpose of this study was to analyse the sequence of atrial contraction during sinus rhythm and paced left atrial rhythm. If this sequence during paced left atrial rhythm should always be inverted Received 12 July 1972. as compared to that during sinus rhythm, then simultaneous atrial pressure measurements would be a valuable tool for identification of spontaneous left atrial rhythm. Subjects and methods Eight patients (Table I) with normal sinus rhythm were studied. During diagnostic right and left heart catheter-ization a 7 F Cournand catheter was introduced percu-taneously into the right femoral vein and positioned in the right atrium. An 8 F Brockenbrough catheter was introduced into the same vein and advanced into the left atrium, either by puncture of the atrial septum or via a patent …