Cardiac function test in patients with cardiovascular diseases. I. Comparison of 3 minute and 10 minute treadmill exercise tests

Abstract

For the evaluation of cardiac function in patients with cardiovascular diseases, classification of functional capacity by New York Heart Association (NYHA) based on subjective symptoms is available. However, the evaluation of cardiac function should be carried out as objectively as possible. Miyake from this Department used Master's 2-steps to give a load for 3 and 10 minutes and reported that a long term loading is not always necessary for the evaluation of cardiac function and loading for a prolonged period could be dangerous. In order to examine the problem of the duration of loading more objectively, the author used a thredmill, instead of Master's 2-steps to give a load for 3 and 10 minutes to the same patient with cardiovascular disease. Along with 12 healthy normal subjects, 9 patients with hypertension, 19 patients with valvular heart diseases, and 25 patients with coronary heart diseases under treatment on ambulant basis or during hospitalization were studied. According to the NYHA classification of functional capacity, 13 were classified as I, 22 as II, 18 as III and 12 as normal, giving the total of 65 cases. Loading was given on a treadmill with a grade of 5° and 30 meters per minute for 3 and 10 minutes. Continuous recording was carried out Evaluation of Cardiac Function, with 2-channel electrocardiograph. Expired air was obtaind into Douglas-bag before, during and after exercise for analysis with Scholander's microgas-analyzer to calculate relative metabolic rate (RMR), physical fitness index (PFI), oxygen debt and oxygen pulse. Arterial blood gas was analyzed using capillary blood and lactic acid in the venous blood was also analyzed. As the signs for stopping exercise, marked dyspnea, palpitation or chest pain were chosen and exercise was immediately stopped upon appearance of these symptoms. The criterion for discontinuation of exercise was set at ST depression or elevation of 2.0 mm more than the pre-loading level, and upon frequent occurrence of premature beats or appearance of paroxysmal tachycardia. Repro-ducibility of these loadings was also studied.