Braith R W, Clapp L, Brown T, Brown C, Schofield R, Mills R M, Hill J A
Center for Exercise Science, College of Health and Human Performance, College of Medicine (Division of Cardiology), University of Florida, Gainesville, FL 32611, USA.
J Cardiopulm Rehabil. 2000 Nov-Dec;20(6):377-82. doi: 10.1097/00008483-200011000-00007.
Chronotropic incompetence is one cause of diminished exercise capacity in heart transplant recipients. If reinnervation occurs, it often is late after transplantation and is not always accompanied by functional improvements in peak heart rate and appropriate tachycardia during exercise. To determine the efficacy of rate-responsive pacing on peak heart rate and exercise capacity, the authors studied eight male heart transplant recipients (age 57 +/- 12 years; 23 +/- 9 months after transplantation) that had either atrial or dual-chambered pacemakers.
All subjects completed two maximal graded exercise tests (GXT) using the Naughton treadmill protocol. During the first GXT, pacemakers were programmed for bradycardia support only and without rate responsiveness (unpaced). After a 14-day regimen of beta blockade with metoprolol to nullify the influence of circulating catecholamines on heart rate, subjects performed the second GXT with pacemakers programmed to respond optimally in the rate-responsive mode (paced).
Peak heart rate (149 versus 129 bpm), peak oxygen uptake (18.9 versus 15.4 mL/kg/min), treadmill time to exhaustion (14.6 versus 12.4 min), and minute ventilation (76.7 versus 66.2 L/min) were significantly increased (P < or = 0.05) during the paced versus unpaced GXT.
The results of this study demonstrate that chronotropic support of the transplanted heart using a rate-responsive pacemaker, with activity-based sensors programmed for maximal sensitivity, improves both peak heart rate and exercise capacity in heart transplant recipients significantly more than circulating catecholamines alone.
变时性功能不全是心脏移植受者运动能力下降的一个原因。如果发生再神经支配，通常在移植后较晚出现，且并不总是伴随着运动时峰值心率和适当心动过速的功能改善。为了确定频率应答性起搏对峰值心率和运动能力的疗效，作者研究了8名植入心房或双腔起搏器的男性心脏移植受者（年龄57±12岁；移植后23±9个月）。
所有受试者使用诺顿跑步机方案完成两次最大分级运动试验（GXT）。在第一次GXT期间，起搏器仅设定为支持心动过缓且无频率应答功能（非起搏状态）。在使用美托洛尔进行为期14天的β受体阻滞剂治疗以消除循环儿茶酚胺对心率的影响后，受试者进行第二次GXT，此时起搏器设定为在频率应答模式下最佳应答（起搏状态）。
与非起搏状态的GXT相比，起搏状态的GXT期间，峰值心率（149对129次/分钟）、峰值摄氧量（18.9对15.4毫升/千克/分钟）、跑步机运动至力竭时间（14.6对12.4分钟）和分钟通气量（76.7对66.2升/分钟）均显著增加（P≤0.05）。
本研究结果表明，使用频率应答性起搏器对移植心脏进行变时性支持，将基于活动的传感器编程为最大灵敏度，比单独的循环儿茶酚胺能更显著地提高心脏移植受者的峰值心率和运动能力。
