Matthew A. Saval

New York Heart Association functional class predicts exercise parameters in the current era

BACKGROUND The New York Heart Association (NYHA) functional class is a subjective estimate of a patients functional ability based on symptoms that do not always correlate with the objective estimate of functional capacity, peak oxygen consumption (peak V(O2)). In addition, relationships between these 2 measurements have not been examined in the current medical era when patients are using beta-blockers, aldosterone antagonists, and cardiac resynchronization therapy (CRT). Using baseline data from the HF-ACTION (Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing) study, we examined this relationship. METHODS One thousand seven hundred fifty-eight patients underwent a symptom-limited metabolic stress test and stopped exercise due to dyspnea or fatigue. The relationship between NYHA functional class and peak V(O2) was examined. In addition, the effects of beta-blockers, aldosterone antagonists, and CRT therapy on these relationships were compared. RESULTS The NYHA II patients have a significantly higher peak Vo(2) (16.1 +/- 4.6 vs 13.0 +/- 4.2 mL/kg per minute), a lower ventilation (Ve)/V(CO2) slope (32.8 +/- 7.7 vs 36.8 +/- 10.4), and a longer duration of exercise (11.0 +/- 3.9 vs 8.0 +/- 3.4 minutes) than NYHA III/IV patients. Within each functional class, there was no difference in any of the exercise parameters between patients on or off of beta-blockers, aldosterone antagonists, or CRT therapy. Finally, with increasing age, a significant difference in peak Vo(2), Ve/V(CO2) slope, and exercise time was found. CONCLUSION For patients being treated with current medical therapy, there still is a difference in true functional capacity between NYHA functional class II and III/IV patients. However, within each NYHA functional class, the presence or absence or contemporary heart failure therapies does not alter exercise parameters.

Challenges with Percent Predicted Maximum VO2 in Patients with Heart Failure

Purpose This study aimed to describe the influence of different equations to predict maximal oxygen uptake (MV˙O2) on the percent predicted MV˙O2 (ppMV˙O2) and the resultant categorization of patients with heart failure with reduced ejection fraction into high or low risk. Methods In this retrospective cohort study, ppMV˙O2 was calculated using six different equations to predict MV˙O2 among 1168 patients with heart failure with reduced ejection fraction (33% women). Repeated-measures ANOVA was used to compare within-subject differences in mean ppMV˙O2 between the prediction equations. Cochrane’s Q test was used to compare the within-subject difference in the proportion of patients with ppMV˙O2 of <50% (high risk) and ≥75% (low risk) between the prediction equations. Results The ppMV˙O2 varied significantly (P < 0.001) between the MV˙O2 prediction equations, with mean (10th, 90th percentile) ppMV˙O2 ranging from 39% (25%, 54%) to 60% (39%, 83%) in men and 37% (24%, 49%) to 70% (47%, 94%) in women. Significant variation (P < 0.001) was also observed between prediction equations for the proportion of patients with ppMV˙O2 of <50% and ≥75% in men and women. Conclusions Statistically significant and clinically meaningful variations in the ppMV˙O2 are observed on the basis of the reference equation used to predict MV˙O2. Future writing committees should specify the preferred reference equation when identifying a ppMV˙O2 criterion in guideline statements.