Response to "renal dysfunction in heart failure is due to congestion but not low output".

Abstract

To the Editor: Worsening renal function in patients with heart failure involves complicated pathophysiologic processes. The article by Guglin et al1 reports that reduced kidney function in patients with heart failure is due to renal congestion rather than decreased cardiac function. The authors correlated renal function with a variety of hemodynamic measurements and calculated the renal perfusion pressure as the difference between the mean arterial pressure and central venous pressure. Recently, a group of patients with heart failure were observed to have increased intra-abdominal pressure (IAP).2 These same investigators3 demonstrated that prompt reduction of IAP by paracentesis improved kidney function. In the current study, no IAP measurements were available, therefore certain physiologic parameters may not accurately reflect the calculated renal perfusion and renal vein pressures. Increased IAP influences intrathoracic and central venous pressure measurements and thereby alters venous return, cardiac output, and other cardiovascular parameters, including renal perfusion and renal vein pressures. Most of the effects of increased IAP have come from the study of surgical patients with abdominal compartment syndrome.4 In that setting, renal dysfunction has been recognized as the “canary for abdominal hypertension.”5 Increased IAP can significantly decrease renal arterial blood flow and increase renal venous pressure, thereby exerting exaggerated effects on renal function because of separate changes in glomerular and interstitial/proximal tubular pressures, all of which results in a decreased filtration gradient. The dual effect of decreasing renal perfusion pressure and increasing proximal tubular pressure subjects the kidney to a double jeopardy and predisposes it to a decreasing glomerular filtration rate and the development of progressive renal insufficiency. Therefore, in patients with heart failure and renal dysfunction, IAP measurements are necessary to better evaluate the hemodynamic findings. Awareness of the effects of IAP on the renal filtration gradient, renal function, and urine production will allow for a more accurate appreciation of both the renal perfusion and renal vein pressures.