Copyright © 1998 by the European Society of Cardiology.
Impairment of exercise capacity and peak oxygen consumption in patients with mild left ventricular dysfunction and coronary artery disease
a Department of Cardiology/Thoraxcenter, University Hospital Groningen
b Department of Human Movement Sciences, University of Groningen
Northern Center for Healthcare Research, Groningen, The Netherlands
accepted May 20, 1998
Aims
Most studies in chronic heart failure have only included patients with marked left ventricular systolic dysfunction (i.e. ejection fraction 
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 VO2was impaired in patients with mild left ventricular dysfunction.
Methods
Peak VO2and 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 VO2values, a ‘decreased’ exercise capacity was defined as predicted peak VO2–1xSD (0·81 of predicted peak VO2), and a severely decreased exercise capacity as predicted peak VO2–2xSD (0·62 of predicted peak VO2).
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 VO2was lower in patients with mild left ventricular dysfunction (23·6±5·7 vs 27·1±4·6ml.min–1.kg–1in controls,P<0·05). In 75% of the study population patients (n=42) age-adjusted peak VO2was decreased (NYHAI/II: n=29/13) and in 18% of them severely decreased (n=10; NYHAI/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 VO2.
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.The European Society of Cardiology
Key Words: Heart failure • coronary disease • exercise capacity • peak VO2 • anaerobic threshold
f1 Correspondence: Dr D. J. van Veldhuisen, Department of Cardiology/Thoraxcenter, University Hospital Groningen, P.O. Box 30001, 9700 RB Groningen, The Netherlands.
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