RELATION OF THE 9-MINUTE SELF-POWERED TREADMILL TEST TO MAXIMAL EXERCISE CAPACITY AND SKELETAL-MUSCLE FUNCTION IN PATIENTS WITH CONGESTIVE-HEART-FAILURE

The 9-minute self-powered treadmill test has been employed to evaluate submaximal exercise capacity in heart failure patients, but its relat ion to maximal exercise capacity and to indexes of skeletal muscle fun ction has not been well defined. Two protocols were utilized. The firs t evaluated the relation of the peak oxygen uptake (VO2) achieved on t he self-powered treadmill to that during a symptom-limited treadmill p rotocol, and examined the reproducibility of this test. Thirteen patie nts (aged 62 +/- 2 years, in New York Heart Association class I to III [2.3 +/- 0.1], ejection fraction 23 +/- 2% [means +/- SEM]) and 10 ag e-matched sedentary controls were studied. The second protocol, which involved 18 patients (aged 65 +/- 2 years, in New York Heart Associati on class I to IV [2.4 +/- 0.1], ejection fraction 23 +/- 2%) and 10 ag e-matched controls evaluated the relation of performance on the self-p owered treadmill to maximal systemic exercise capacity on a cycle ergo meter and to indexes of skeletal muscle function. In the first protoco l, the test was found to be highly reproducible. The proportion of sel f-powered treadmill to maximal treadmill peak VO2 did not differ signi ficantly between patients and controls (95 +/- 5% vs 87 +/- 6%). In th e second protocol, patients achieved a lower peak VO2 (15.6 +/- 1.1 vs 25.6 +/- 0.9 ml/kg/min, p <0.001), walked a shorter distance on the s elf-powered treadmill (367 +/- 32 vs 667 +/- 28 m, p <0.001), and exhi bited less knee extensor work capacity (1,075 +/- 116 vs 1,390 +/- 110 ft-lbs, p <0.05). The self-powered treadmill distance correlated stro ngly with peak VO2 in patients (r = 0.79, p <0.001) and with total kne e extensor work in both patients and controls (r = 0.62 and 0.80, resp ectively, both p <0.01), but exhibited poor correlation with muscle st rength and endurance. These results indicate that the self-powered tre admill test is a reproducible and convenient test that appears to be m ore of a measure of maximal than submaximal exercise tolerance in pati ents with congestive heart failure. Although it correlates relatively well with symptom status, it is poorly related to indexes of left vent ricular function and muscle performance.