Impairment of exercise capacity and peak oxygen consumption in patients with mild left ventricular dysfunction and coronary artery disease

Aims Most studies in chronic heart failure have only included patients with marked left ventricular systolic dysfunction (i.e. ejection fraction less than or equal to 0.35), and patients with mild left ventricular dysfunction are usually excluded. Further, exercise capacity strongly depends on age, but age-adjustment is usually not applied in these studies. Therefore, this study sought to establish whether (age-adjusted) peak Vo(2) was impaired in patients with mild left ventricular dysfunction. Methods Peak Vo(2) and ventilatory anaerobic threshold were measured in 56 male patients with mild left ventricular dysfunction (ejection fraction 0.35-0.55; study population) and in 17 male patients with a normal left ventricular function (ejection fraction >0.55; control population). All patients had an old (>4 weeks) myocardial infarction. By using age-adjusted peak Vo(2) values, a 'decreased' exercise capacity was defined as less than or equal to predicted peak Vo(2) - 1 x SD (0.81 of predicted peak Vo(2)), and a severely decreased exercise capacity as less than or equal to predicted peak Vo(2) - 2 x SD (0.62 of predicted peak Vo(2)). Results Patients in the study population (age 52 +/- 9 years; ejection fraction 0.46 +/- 0.06) were mostly asymptomatic (NYHA class I; n=40, 76%), while 16 patients (24%) had mild symptoms, i.e. NYHA class II. All 17 controls (age 57 +/- 8 years) were asymptomatic. Mean peak Vo(2) was lower in patients with mild left ventricular dysfunction (23.6 +/- 5.7 vs 27.1 +/- 4.6 ml.min(-1).kg(-1) in controls, P<0.05). In 75% of the study population patients (n=42) age-adjusted peak Vo(2) was decreased (NYHA I/II: n=29/ 13) and in 18% of them severely decreased (n=10; NYHA I/ II: n=6/4). In contrast, only three patients (18%) in the control population had a decreased and none a severely decreased age-adjusted peak Vo(2). Conclusion In patients with mild left ventricular dysfunction, who have either no or only mild symptoms of chronic heart failure, a substantial proportion has an impaired exercise capacity. By using age-adjustment, impairment of exercise capacity becomes more evident in younger patients. Patients with mild left ventricular dysfunction are probably under-diagnosed, and this finding has clinical and therapeutic implications.