RESUMO
AIMS: To develop and validate a readily-available tool for the evaluation of the fitness of cardiac patients. BACKGROUND: Physical fitness is an important factor in the tertiary prevention for cardiac patients. METHODS: In this cross-sectional study, 154 cardiac patients: 119 men and 35 women, mean age 63.1±11.2 years, entering the cardiac-rehabilitation program at the Sheba Medical Center, gave informed consent and completed a 24-hour recall physical activity questionnaire. Information on BMI, medication use and on their performance on a symptom-free limited treadmill test, i.e. measured estimated VO2 (ml/kg/min) and resting heart rate (bpm), were obtained from the medical chart. RESULTS: A linear-regression equation for predicting the measured estimated VO2 includes the overall physical activity index calculated from the physical activity questionnaire, sex, age, BMI, type of coronary heart disease (acute myocardial infarction, coronary artery bypass graft, percutaneous coronary intervention), duration of illness, resting heart rate, use of beta-blockers and level of education. The correlation coefficient between measured VO2 values and calculated values is r=0.6. Upon categorizing patients to high and low physical fitness according to the VO2 median value, the validity of the equation was found to be good: sensitivity=61.2%, specificity=65.2%, positive predictive value=68.4%, negative predictive value=57.7%. CONCLUSIONS: The prediction equation for assessing VO2 in cardiac patients is a simple, inexpensive tool, which may be used for monitoring changes in the patients' physical fitness. It may assist the physician in following a cardiac patient's response to physical activity recommendations and improving fitness when the ergometric stress-test availability is low.