Relationship Between Diastolic Mitral Regurgitation and PQ Intervals or Cardiac Function in Patients Implanted with DDD Pacemakers

Diastolic mitral regurgitation (MR) is known to be induced by prolonging atrioventricular (AV) delay in patients implanted with a DDD pacemaker. We studied the relationship between diastolic MR and PQ intervals on cardiac function in 50 patients (71.3 ± 11.3 years old: mean ± SD), who had been implanted with DDD pacemakers. In 19 patients, prior to pacemaker implantation, pulmonary capillary wedge pressure (PCWP) was measured using a Swan-Ganz catheter during AV sequential pacing with an AV delay of 0.165 seconds. Transmitrai blood flow was measured with pulsed Doppler echocardiography, while prolonging AV delay stepwise by 0.025 seconds from 0.065 seconds for about 5 minutes each. In nine patients, AV delay could not be prolonged enough due to occurrence of intrinsic AV conduction. In the other 41 patients, diastolic MR was induced by prolonging AV delay. The critical PQ intervals that induced diastolic MR ranged from 0.14 to 0.26 (0.23 ± 0.03) seconds. Four of five patients whose critical PQ intervals were 0.20 seconds or shorter had heart failure, while 36 patients whose critical PQ intervals were >0.20 seconds were free from signs and symptoms of heart failure. Their PCWPs were 2–27 (7.5 ± 5.1) mmHg. There was a significant negative correlation between the critical PQ intervals for the appearance of diastolic MR and PCWP during AV sequential pacing, which was performed prior to pacemaker implantation (r = -0.85, P < 0.001). It is suggested that the appearance of diastolic MR is determined mainly by PQ intervals and cardiac function. Measurement of the critical PQ intervals that induce diastolic MR may be useful in assessing cardiac function in patients implanted with DDD pacemakers.