심방 조율에 따른 심근대사의 변화

Abstract

Background：In aerometabolic process, the human heart mainly utilizes free fatty acid as fuel. During anaerobic process, lactate production by the myocardium is increased and accumulates in the myocardium. Thus it decreases the contractility of myocardium. Therefore in patients with ischemic heart disease, lactate production must be increased by the myocardium during myocardial ischemia. During paroxysmal supraventricular tachycardia, patients frequently experience chest pain and ST segment depression suggesting acute myocardial ischemia. However it occurs on a physiologic basis independent of ischemia. The purpose of this study was to assess whether tachycardia induced by atrial pacing produces myocardial ischemia in patients without evidence of ischemic heart disease. Methods：Between May 28, 1996 and August 13, 1996, at the University of Keimyung, Dong- San Medical center, 15 patients(male 9, female 6, mean age of 38 years) with palpitation underwent electrophysiologic testing and had radiofrequency catheter ablation. There were no evidence of ischemic heart disease. Right atrial pacing was done with lengths of 500msec, 400msec and 350msec in each 5 patients. A 12 lead electrocardiogram, left ventricular end-diastolic pressure, blood from femoral artery and coronary sinus for lactate determinations and blood gas analysis were obtained simultaneously. They were obtained at baseline, at 1, 5, 10 and 15 minute of atrial pacing and at 1, 5, 10 minute after cessation of pacing. Results：Significant changes were not observed in PO2, PCO2, concentration of HCO3 -, pH and O2 saturation. In all patients, mean percent lactate extraction was above 10% and not significantly changed during atrial pacing. However ST segment depression was significantly progressive during atrial pacing and according to decrease the cycle length(p<0.05), also left ventricular end-diastolic pressure was significantly decreased during atrial pacing(p<0.05). Conclusion：Therefore tachycardia induced by atrial pacing for 15 minutes did not produce myocardial ischemia in patients without evidence of ischemic heart disease. Depression of ST segmentduring supraventricular tachycardia or atrial pacing, in patient without underlying heart disease is necessary to investigate what makes this phenomenon. KEY WORDS：Atrial pacing·Ischemia·Lactate·ST depression·LVEDP.

정상환경에서 심장의 에너지원은 주로 지방산의 산화에 의해 얻어진다. 그러나 혐기성 상황에 이르면 탄수화물이나 젖산, pyruvic acid 등을 에너지원으로 사 용하고 혐기성 상태가 지속되면 탄수화물 대사가 증가되어 수분내에 젖산의 형성이 촉진된다. 그리고 젖산은 심근내에 축적되게 되고 수축력 감소를 초래한다. 따라서 허혈성 심질환이 있는 환자에서는 심근허혈동 안 심전도에서 ST 분절의 하강이 나타나게되고 심근에서 혐기성 대사에 의한 젖산의 산생이 증가된다1-3). 한편으로 상심실성 빈맥의 발작이 있는 환자들의 심전도에서도 흔히 심근허혈을 시사하는 ST 분절의 하강이 관찰되고, 환자들은 흉통을 호소한다. 그러나 상심실성 빈맥동안의 ST 분절 하강은 심근허혈과 무관하게 발생된다는 보고도있어 저자는 허혈성 심질환의 증거가 없는 환자를 대상으로 심방조율로 심박수를 조절하여 빈맥을 유발시켰고, 심장에서 젖산 대사의 변화와 좌심실 말기 확장기압 그리고 12유도 심전도를 측정함으로써 빈맥이 심근허혈 상태를 유발할 수 있는지, 또 심근 수축력에는 어떠한 영향을 주는지 알아보고자 하였다.