Muscle strength as a predictor of long-term survival in severe congestive heart failure

The objective of the study was to test the relationship between isolated muscle strength and outcome, and its significance in the context of other exercise variables.

122 consecutive patients (LVEF 21+/-7%) were enrolled in the study. Isokinetic strength testing of the knee extensor and flexor muscles were performed. A subset of 51 patients underwent additional upright bicycle testing with gas exchange analysis. The outcome up to 60 months was defined by event-free survival (group A, n=59) or death (group B, n=34). Patients who had been transplanted were excluded from further analysis. The peak strength of the quadriceps muscle was comparable in both groups (N.S.). In contrast, the index (value adjusted for weight) did reveal significant differences (P<0.04), similar to the peak torque of the knee flexor muscle (P<0.04), whose index was even more significant with regard to differences (P<0.01). Multivariate analysis including muscle strength variables, pVO2 and workload into one model show that the flexor strength index is the only independent variable (x2=9 P<0.003). A cut-off point of 68 Nm x 100/kg in the strength index of the flexor muscles was used to establish a significant difference between groups with regard to outcome (P<0.01). Thus, the isokinetic strength of the knee flexor muscles is related to outcome. Moreover, this parameter is superior to variables such as peakVO2 and workload.