AEROBIC CAPACITY AND FUNCTIONAL CLASSIFICATION OF PATIENTS WITH SEVERE LEFT-VENTRICULAR DYSFUNCTION

Classes I/II and III of the classification systems of the New York Hea rt Association (NYHA), Canadian Cardiovascular Society (CCS) and Ameri can Medical Association (AMA) were compared with each other and with t he Weber classification (O-2 uptake, VO2/kg during treadmill walking) in 35 male patients with severe left ventricular dysfunction. Measured end points were ventilatory threshold (VT) and peak exercise. Also in vestigated was whether the CCS and AMA scales, due to their more strin gent differentiation, are more precise than the NYHA system in determi ning a limited physical capacity and whether there are other different iating factors useful in classification which may be derived from card iopulmonary exercise testing. At the VT, the mean VO2/kg did not diffe r significantly in any classification system between classes I/II and III (12.8 +/- 2.5 vs. 11.1 +/- 2.3 ml/kg/min) and corresponded to Webe r class B. At peak exercise, the mean VO2/kg only differed significant ly within the NYHA classification; classes I/II (16.3 +/- 3.1 ml/kg/mi n) corresponded to Weber class B, and class III (13 +/- 3 ml/kg/min) t o Weber class C. The individual values displayed a large scatter. Fact ors differing in classes I/II and III of all three systems at peak exe rcise were the ventilatory equivalent of O-2 and CO2 as well as end-ti dal partial pressure for O-2 and CO2. At VT these factors showed a sep arating character only in the AMA classification. It is not possible t o determine objective functional impairment by use of the NYHA, CCS an d AMA systems because they are not analogous to the Weber system. Neve rtheless, these classification systems can be used for clinical assess ment and follow-up.