Kao A C, Van Trigt P, Shaeffer-McCall G S, Shaw J P, Kuzil B B, Page R D, Higginbotham M B
Department of Medicine, Duke University Medical Center, Durham, NC 27710.
Circulation. 1994 Jun;89(6):2605-15. doi: 10.1161/01.cir.89.6.2605.
Functional capacity and quality of life are subjectively improved after cardiac transplantation. However, the objective improvement in exercise tolerance after transplantation has been disappointing. The extent to which allograft diastolic dysfunction contributes to this exercise intolerance has not been defined.
Thirty cardiac transplant recipients between 3 and 16 months after transplantation and 30 age-matched normal control subjects underwent maximal symptom-limited graded upright bicycle exercise testing with simultaneous radionuclide angiography, invasive hemodynamic monitoring, and breath-by-breath gas analysis. Mean blood pressure was higher in the transplant group at supine rest (112.1 versus 97.7 mm Hg), normalized with upright posture, and became lower than normal at peak exercise (121.1 versus 133.2 mm Hg). Systolic function as measured by ejection fraction was normal in both groups. However, the cardiac transplant recipients had significantly lower exercise tolerance, achieving a mean maximal work rate of 390 kilopond-meters per minute (kpm/min), compared with 825 kpm/min in the normal subjects. Peak oxygen consumption was 12.3 mL.min-1.kg-1 in the transplant group, 46% lower than the normal group's value of 22.9 mL.min-1.kg-1. The transplant patients had a resting tachycardia (94 beats per minute) and a 79% reduction in exercise heart rate reserve compared with normal. Despite this chronotropic incompetence, stroke index response to exercise was consistently lower after transplantation, accounting for a 41% reduction in cardiac index at maximal exercise. The lower stroke index was accompanied by a 32% lower end-diastolic volume index at rest and a 14% lower end-diastolic volume index at peak exercise. Despite the smaller ventricular volumes after transplantation, pulmonary capillary wedge pressure was 35% higher than normal at supine rest and 50% higher at maximal exercise. Right atrial and mean pulmonary arterial pressures were similarly elevated. The ratio of pulmonary capillary wedge pressure to end-diastolic volume index was significantly higher during the postural change and exercise, suggesting allograft diastolic dysfunction. Arteriovenous oxygen difference was similar between groups at rest and with submaximal exercise but was 24% lower at maximal exercise in the transplant group, suggesting an abnormality in peripheral oxygen uptake or utilization.
Exercise tolerance is severely limited during the first 16 months after cardiac transplantation despite preservation of allograft left ventricular systolic function. This intolerance is due to an inadequate cardiac index response from a combination of chronotropic incompetence and diastolic dysfunction limiting the appropriate compensatory use of the Starling mechanism. In addition, there is a peripheral abnormality in oxygen transport or utilization that may partially reflect the effects of deconditioning.
心脏移植后，患者的功能能力和生活质量在主观上有所改善。然而，移植后运动耐量的客观改善情况却不尽人意。同种异体移植心脏舒张功能障碍对这种运动不耐受的影响程度尚未明确。
30名心脏移植受者（移植后3至16个月）和30名年龄匹配的正常对照者接受了症状限制的最大负荷直立自行车运动试验，同时进行放射性核素血管造影、有创血流动力学监测和逐次呼吸气体分析。移植组仰卧位休息时平均血压较高（112.1对97.7毫米汞柱），直立姿势时血压恢复正常，且在运动峰值时低于正常水平（121.1对133.2毫米汞柱）。两组通过射血分数测量的收缩功能均正常。然而，心脏移植受者的运动耐量明显较低，平均最大工作率为每分钟390千克力米（kpm/min），而正常受试者为825 kpm/min。移植组的峰值耗氧量为12.３毫升·分钟-1·千克-1，比正常组的22.9毫升·分钟-1·千克-1低46%。移植患者静息时心动过速（每分钟94次），与正常相比，运动心率储备降低79%。尽管存在变时性功能不全，但移植后每搏量指数对运动的反应始终较低，导致最大运动时心脏指数降低41%。较低的每搏量指数伴随着静息时舒张末期容积指数降低32%，运动峰值时舒张末期容积指数降低14%。尽管移植后心室容积较小，但仰卧位休息时肺毛细血管楔压比正常高35%，最大运动时高50%。右心房和平均肺动脉压也同样升高。在体位改变和运动期间，肺毛细血管楔压与舒张末期容积指数的比值明显更高，提示同种异体移植心脏舒张功能障碍。两组在休息和次最大运动时动静脉氧分压差相似，但移植组在最大运动时低24%，提示外周氧摄取或利用存在异常。
心脏移植后的前16个月内，尽管同种异体移植心脏左心室收缩功能得以保留，但运动耐量仍受到严重限制。这种不耐受是由于变时性功能不全和舒张功能障碍共同导致心脏指数反应不足，限制了对Starling机制的适当代偿性利用。此外，外周氧运输或利用存在异常，这可能部分反映了失适应的影响。
