Diagnostic Use of Rapid Volume Infusion
Abstract & Commentary
By Michael H. Crawford, MD, Editor
Source: Fujimoto N, et al. Hemodynamic responses to rapid saline loading: The impact of age, sex, and heart failure. Circulation 2013;127:55-62.
Volume infusion during right heart catheterization has been recommended to distinguish patients with pulmonary hypertension (PH) from those with heart failure with preserved ejection fraction (HFpEF). However, few data exist on the normal response to volume loading, especially in older individuals who are expected to have stiffer ventricles. This is especially so for older women. Thus, these investigators studied 60 healthy subjects and 11 HFpEF patients before and during warm saline infusion at 100-200 mL/min. The normal patients were about evenly divided into four groups by sex and age ≥ 50 years or < 50 years. The normal patients were given about 1 liter and the HFpEF patients got about 0.5 liter for safety reasons, but both groups got the same volume indexed to total blood volume (0.20-0.22). In the normal subjects, a second infusion was performed 6-8 minutes after the first one. In the normals, pulmonary capillary wedge pressure (PCWP) increased from an average of 10 mmHg to 16 mmHg after the first liter of saline and to 20 after the second liter. PCWP values > 15 were observed in 62% of the normals after one liter and 93% after the second liter. Older women showed a 25% steeper increase in PCWP with volume loading than younger women or men (P < 0.05). Mean pulmonary artery pressure (MPAP) increased by about 80% in all four groups and there was a modest increase in systemic blood pressure. MPAP indexed to cardiac output increased more in women compared to men. HFpEF patients showed a steeper rise in PCWP from a higher baseline and all pressure measurements were higher than the controls after the first infusion. The authors concluded that LV filling pressures rise significantly with volume loading in healthy controls and HFpEF patients. The largest increases in PCWP were observed in HFpEF patients and older women.
This study makes two important points. First, most healthy controls exceeded the upper limit of PCWP of 15 mmHg with rapid volume expansion. Since well-compensated patients with HFpEF often have a resting PCWP < 15, the rise to > 15 with volume loading was thought to define HFpEF. Clearly this criterion is flawed. This study did show that HFpEF patients had larger rises in PCWP than healthy controls. Thus, there may be an opportunity to redefine the hemodynamics of HFpEF patients, but I doubt that there will be one reliable hemodynamic measure to diagnose HFpEF.
Second, women > 50 years of age exhibited a more rapid rise in PCWP than men or younger women. This finding may explain why HFpEF is more common in elderly women. However, many HFpEF patients also have systemic hypertension and diabetes, so it may not be as simple as a sex-related trait.
There are limitations to this study. The number of HFpEF patients was small. The saline infusion rates varied between subjects and women in general got less volume expansion. Also, blood volume was estimated, not measured, in the HFpEF patients. More studies need to be done in larger numbers of HFpEF patients and multiple clinical parameters should be considered. There may be a combination of factors or an algorithm that can be developed to aide in the diagnosis of HFpEF.