Kanda A, Watanabe I, Kojima T, Kondo K, Kunimoto S, Takahashi Y, Kasamaki Y, Ogura T, Kajita J, Saito S
Second Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
Jpn Heart J. 1995 Jul;36(4):439-50. doi: 10.1536/ihj.36.439.
We evaluated the relationship between changes in the atrioventricular (AV) intervals and right atrial monophasic action potential duration at 90% repolarization (RA-MAPD90) in humans. In 4 patients, RA-MAPD90 was measured during AV reciprocating tachycardia (AVRT, n = 2) or AV node reentrant tachycardia (AVNRT, n = 2) and atrial or ventricular pacing at similar cycle lengths. In 10 patients, RA-MAPD90 was measured during continuous atrioventricular sequential pacing at AV intervals of 0, 50, 100, 150, 200, 250, 300, 350 msec for 90 sec at a cycle length of 333-400 msec. In patients with AVRT, the RA-MAPD90 during tachycardia was shorter than RA-MAPD90 during RA or RV pacing. In patients with AVNRT, RA-MAPD90 during tachycardia was similar or longer than RA-MAPD90 during RA or RV pacing. As the AV interval was increased from 0 msec to 150 msec, the peak right atrial pressure decreased from 8-12 mmHg to 2-3 mmHg. RA-MAPD90 decreased to its minimal value at an AV interval of 150 msec. The maximal difference in the RA-MAPD90 obtained by changing the AV interval was 22.5 +/- 3.0 msec. We conclude that 1) a very short AV or VA interval causes an increase in RA-MAPD90 which correlates with an increase in RA pressure, and 2) RA-MAPD90 during supraventricular tachycardia is different from RA-MAPD90 during atrial or ventricular pacing. Thus, a contraction-excitation feedback mechanism may exist in the human atrium.
