Takefumi Ozawa

His-bundle electrogram in the convalescent stage ofinferior myocardial infarction complicated with complete A-V block

Twelve patients with inferior wall myocardial infarction complicated with complete atrioventricular block during the acute stage were studied. The His-bundle electrogram was studied in the convalescent stage at an average of 6 months after the acute attack. The age of the patients was 62 +/- 16 years. The width of the QRS complex was within the normal range and the PR interval was less than 200 msec. AH time was 74 +/- 18 msec (mean +/- SD). No split H activity was observed. HV time however, was significantly prolonged in the 12 patients; 54 +/- 12 msec vs. 42 +/- 9 msec in the control group (p less than 0.02). Five patients had HV time equal to or more than 60 msec. Intra-His block was suggested to exist in a high frequency in the patients who had previous complete AV block during the acute stage of myocardial infarction of the inferior wall.

A possible autonomic modulation of sinus node recovery time in overdrive suppression test

The effect of blood pressure fall on sinus node recovery time (SNRT) was studied in 17 patients during the overdrive suppression test. Their maximal SNRT was less than 150% of the mean P-P interval of the control state (=SCL) and CSNRT (=SNRT-SCL) was less than 550msec. Blood pressure was found to fall in about a half of the patients at a high pacing rate. Concomitantly, SNRT was found to shorten in those who showed such a fall in blood pressure. The subjects were then divided into two groups; one with a shorter SNRT at 150bpm than at 90bpm of pacing rate and the other without such shortening. The changes in SNRT and CSNRT were both significant in the first group (p less than 0.02 and p less than 0.001, respectively). The fall in blood pressure at 150 bpm was significant in the group with shortened SNRT and CSNRT and it was larger than in the other group: 23 +/- 14mmHg vs. 1 +/- 5mmHg (p less than 0.001). This result suggests a possible modulation of SNRT by a fall of blood pressure via baroreflex.

Ventricular arrhythmia with postural dependency

Ventricular arrhythmias associated with recumbency were noted in a 17-year-old man with mild idiopathic myocarditis. These arrhythmias were refractory to several anti-arrhythmic drugs. Frequent ventricular arrhythmias were reproducibly recorded in the supine position and in a 15 degree tilt from the horizontal, while they were completely abolished in positions tilted more than 30 degrees from the horizontal, at which time sinus rate increased to more than 70 beats/min. The ventricular arrhythmias were suppressed during treadmill exercise and markedly aggravated when the underlying sinus rate was decreased during sleep or lying flat in bed. The arrhythmias were entirely abolished by atropine 1 mg. Furthermore, they were suppressed during atrial pacing at the rates of 80 and 90 bpm. Ventricular tachycardia could not be induced by programmed right ventricular stimulation. The appearance of postural arrhythmias in this patient correlated with relative bradycardia suggesting that they may be related to enhanced vagal nerve activity.