PT  - JOURNAL ARTICLE
AU  - G A Cooke
AU  - P Marshall
AU  - J K Al-Timman
AU  - D J Wright
AU  - R Riley
AU  - R Hainsworth
AU  - L B Tan
TI  - Physiological cardiac reserve: development of a non-invasive method and first estimates in man
AID  - 10.1136/hrt.79.3.289
DP  - 1998 Mar 01
TA  - Heart
PG  - 289--294
VI  - 79
IP  - 3
4099  - http://heart.bmj.com/content/79/3/289.short
4100  - http://heart.bmj.com/content/79/3/289.full
SO  - Heart1998 Mar 01; 79
AB  - Objective To investigate whether physiological cardiac reserve can be measured in man without invasive procedures and whether it is a major determinant of exercise capacity.Design Development of method of measurement and an observational study.Setting A regional cardiothoracic centre.Subjects 70 subjects with a wide range of cardiac function, from heart failure patients to athletes.Methods Subjects underwent treadmill, symptom limited cardiopulmonary exercise tests to measure aerobic exercise capacity (represented by V˙o 2max) and cardiac reserve. Cardiac output was measured non-invasively using the CO 2 rebreathing technique.Results Cardiac power output (CPOmax) at peak exercise was found to be significantly related to aerobic capacity: CPOmax(W) = 0.35 + 1.5V˙o 2max (l/min),r = 0.87, p < 0.001. It also correlated well with exercise duration (r = 0.62, p < 0.001), suggesting that cardiac reserve is a major determinant of exercise capacity. In the study, cardiac reserve ranged from 0.27 to 5.65 W, indicating a 20-fold difference between the most impaired cardiac function and that of the fittest subject.Conclusions A non-invasive method of estimating physiological cardiac reserve was developed. The reserve was found to be a major determinant of exercise capacity in a population of normal subjects and patients with heart disease. This method may thus be used to provide a clearer definition of the extent of cardiac impairment in patients with heart failure.