Tan L B
Department of Cardiovascular Studies, University of Leeds, Killingbeck Hospital, UK.
Postgrad Med J. 1991;67 Suppl 1:S10-20.
The assessment of cardiac function and dysfunction has often concentrated on particular but piecemeal aspects of ventricular performance. This leads to diverse and often opposite claims on how to define, evaluate and treat heart failure. This review adopts a more integrative approach of appraising the heart, putting it in the context of its role in the circulation. The emphasis is to find a variable which would evaluate the overall function of the heart. Several objective criteria on how to select such a variable were proposed. It was argued that of all currently available variables, cardiac power output fulfils these requirements best. It has long been recognised that cardiac performance assessed at basal resting states do not reflect how much reserve the cardiac pump possesses. Having a variable which represents overall cardiac function implies that cardiac pumping capability and reserve can now be quantified. Cardiac reserve has been found to be a major determinant of exercise capacity in heart failure, and pumping capability a major determinant of prognosis in patients with severe heart failure. Therapeutic attempts at improving the exercise capacity of heart failure patients should be gauged against their ability to improve cardiac reserve. Inotropic agents that augment myocardial performance but compromise cardiac reserve do not improve exercise capacity. An ideal inotrope is one that is synergistic with the sympathetic system and enhances cardiac performance only during exercise.
对心脏功能及功能障碍的评估往往集中于心室功能的特定但不完整的方面。这导致在如何定义、评估和治疗心力衰竭方面存在多样且常常相互矛盾的观点。本综述采用一种更综合的方法来评估心脏，将其置于其在循环中的作用背景下。重点是找到一个能够评估心脏整体功能的变量。提出了关于如何选择这样一个变量的几个客观标准。有人认为，在所有目前可用的变量中，心脏功率输出最符合这些要求。长期以来人们认识到，在基础静息状态下评估的心脏功能并不能反映心脏泵血的储备能力。有一个代表心脏整体功能的变量意味着现在可以对心脏泵血能力和储备进行量化。已发现心脏储备是心力衰竭患者运动能力主要决定因素，而泵血能力是重度心力衰竭患者预后的主要决定因素。改善心力衰竭患者运动能力的治疗尝试应根据其改善心脏储备的能力来衡量。增强心肌功能但损害心脏储备的强心剂并不能提高运动能力。理想的强心剂是一种与交感神经系统协同作用且仅在运动期间增强心脏功能的药物。
