Ultrafiltration in moderate heart failure. Exercise oxygen uptake as a predictor of the clinical benefits

Ultrafiltration (UF) can improve the exercise performance of patients with moderate congestive heart failure (CHF). Our aim was to define the starting levels of performance below which UF is beneficial.

We studied 26 patients in 2 to 3 NYHA class, whose clinical condition was stable, left ventricle ejection fraction (echocardiography) was < 35% and peak exercise oxygen uptake (VO2) was > or = 14 mL/min/kg. They underwent a single extracorporeal UF (about 600 mL of ultrafiltrate per hour). Before that, we evaluated pulmonary function (PFT), functional capacity (cardiopulmonary exercise test [CPX]), cardiac index, left ventricle ejection fraction, ventricular filling pressures, and plasma norepinephrine at rest. The PFTs and CPXs were repeated 3 months after UF.

Sixteen patients had a rise of peak exercise VO2 > 1 mL/min/kg at the 3-month evaluation (group A, ultrafiltrate = 2,040 +/- 241 mL) and 10 did not (group B, ultrafiltrate = 1,870 +/- 169 mL). Forced expiratory volume (1 s), maximal voluntary ventilation, and vital capacity were lower in group A than in group B and improved after UF only in group A. Before UF, VO2 at peak exercise and at anaerobic threshold (15.5 +/- 0.4 mL/min/kg and 11.0 +/- 0.5, respectively) was also lower in group A than in group B (21.2 +/- 0.7 mL/min/kg and 14.8 +/- 0.9, p < 0.01). Patients whose pre-UF peak exercise VO2 was > 18.5 mL/min/kg (group B) had no increase in this variable. No significant group differences were detected regarding norepinephrine, left ventricular ejection fraction, and hemodyanmic parameters at rest.

In patients with moderate CHF undergoing UF, exercise capacity improvement is inversely related to the pre-UF level of physical performance and pulmonary function; VO2 at peak exercise seems useful for identification of patients not benefiting from the procedure.