Prognosis Value of Cardiac Power Determination in Patients with Chronic Heart Failure

Abstract

Work Objetive 

To evaluate the predictive value of a new variable obtained through the cardiopulmonary exercise test, the maximum cardiac power (CP_mx) during peak exercise. 

Research Design and Methods

A group of heart failure were prospectively evaluated through the assessment of VO_2mx, CP_mx (oxygen pulse x mean arterial tension) and cardiac reserve (CR) (CP_mx-CP_basal). The value were compared according to the presence of events (heart failure, hospitalization or death). The incremental value through ROC curve and the association of their cut-point with events (long-rank test and Cox regression) were evaluated. Combined end point: admission for worsening HF and/or death. 

Results

Sample of 157 patients, 83.4% men, aged 59 ± 10 years, functional class III/IV: 23.3%. Severe LV systolic dysfunction 56.7%, events 22.9%, average follow-up: 9 months. Patients with events showed lower values of VO2_mx (11.8 vs 14.9 ml/kg/min, p<0.001), CP_mx (831 vs 1079 watts, p=0.003) and CR (465 vs. 676 watts, p=0.002); ROC areas: VO_2mx: 0.73; CP_mx 0.68; CR 0.68, p=0.34 between areas). Risk of events: for VO_2mx < 14 ml/kg/min HR 3.93 (95% CI 1.89-8.20) p<0.001; CP_mx <780 HR 2.78 (CI 1.42-5.43), p=0.003 and CR<350 HR 2.75 (95% CI 1.42-5.35) p=0.003. The incidence of events was of 8.5% in patients with normal VO₂ and CP, 30.3% with only one altered index: HR 3.1 (95% CI 1.16-8.25) p=0.024, and 45.2% with both indexes HR 5 (95% CI 1.81-13.75) p=0.002.

Conclusions

CP_mx is another variable to determine in the cardiopulmonary exercise test which could give incremental predictive value, added to other classical parameters.