Therapeutic Research

Abstract

The patient was a 72 year old with complete atrioventricular block implanted with a DDD pacemaker. At the time of the implantation, the atrial wave amplitude was 3.6–4.0 mV and threshold 0.375 V / 0.4 msec, and the ventricular wave amplitude was negative and threshold 0.375 V / 0.4 msec. Approximately 3 years after the implantation, the ventricular threshold increased（3.0 V / 0.4 msec）. No antiarrhythmic drugs, etc. that could increase the threshold were orally administered. No change in the lead position was observed on the chest x –ray compared to that at implantation and no elevation of the inflammatory markers could be confirmed by blood tests. Echocardiography revealed left ventricular hypokinesis, aortic regurgitation and moderate mitral regurgitation（EF＝48–53％）.Coronary angiography was performed, but there was no significant stenosis. The tilt test （isoproterenol load） also was negative. The results of the electrophysiology study revealed a local threshold increase near the high septal lead. After administering 12 mg of methylprednisolone, the ventricular threshold decreased（4.0 V / 1.5 msec ⇒1.75 V / 1.5 msec）. We experienced a case in which the ventricular threshold sharply increased during the chronic phase several years after the implantation. There was no problem with the pacemaker and local inflammation of the ventricle occurred, however, the deterministic cause of the ventricular threshold rise remained unknown.