Insights into complex interrelationships between heart and kidneys

Research is yielding new understanding of the interactions between the heart and the kidneys—particularly the cardiorenal syndrome, in which failure of either organ can lead to failure of the other. Recent insights into the complex interrelationships between the heart and kidneys are presented in a special symposium section of the July issue of The American Journal of Medical Sciences (AJMS), official journal of the Southern Society for Clinical Investigation. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, and pharmacy.

"In healthy individuals an interdependence exists between the heart and kidneys which contributes to their coordinated physiologic behavior," writes Dr. Karl T. Weber of University of Tennessee Health Science Center, Memphis. "This interplay becomes particularly evident when the heart or kidneys or both fail."

Focus on Unique Interplay between Two Vital Organ Systems
The symposium includes six state-of-the art lectures on the theme of integrative cardiorenal pathophysiology, presented earlier this year at the SSCI's annual scientific session in New Orleans. "There is a clear association between chronic kidney disease and cardiovascular morbidity and mortality, including an increased risk of accelerated atherosclerosis, acute myocardial infarction, and stroke," Dr. Weber writes in a symposium preface.

Dr. Barry M. Wall, also of University of Tennessee, calls for adding tests of kidney function—including albuminuria, the level of the protein albumin in the urine—to routine evaluation of heart disease risk factors. The inexpensive tests provide valuable information on patient risks, especially in the light of recent studies showing that treatment to lower the urine albumin level can improve patient outcomes.

Dr. L. Lee Hamm and Kathleen S. Hering-Smith of Tulane University School of Medicine, New Orleans, present an update on the kidney's pivotal role in causing high blood pressure. A growing body of research suggests that retention of sodium by the kidneys is an important contributor to hypertension, especially in people who have "salt sensitivity."

Special Importance in Heart Failure
"The important interplay between the heart and kidneys is nowhere more evident than in heart failure," according to Dr. Weber. Dr. Daniel Villarreal and colleagues of SUNY Upstate Medical Center, Syracuse, N.Y., review the evolving concept of the "cardiorenal syndrome," in which heart failure causes kidney failure—or vice versa. Collaborative studies of new treatments addressing the function of both organs will be needed to improve outcomes for patients with cardiorenal syndrome.

Heart failure can lead to excessive fluid buildup, but the kidneys may become resistant to the diuretics used to eliminate the fluid. Dr. Michael F. Flessner and colleagues of University of Mississippi Medical Center, Jackson, Miss., discuss a new approach—the use of dialysis (ultrafiltration) to remove excess fluid. Research efforts are underway to clarify the best approach to management of this complex problem.

Low sodium level (hyponatremia) is a common and serious problem in patients with heart failure, further increasing the risk of poor outcomes. Drs. Heather Haley and David W. Ploth of Medical University of South Carolina, Charleston, review the complex processes leading to abnormal sodium metabolism in heart failure. They also update the research evidence on treatment options for this problem.

Finally, Dr. Weber and colleagues reviews the abnormalities of potassium, magnesium, and calcium metabolism that can occur in heart failure and other conditions. Along with deficiencies of important minerals like zinc and selenium, these abnormalities can cause further damage to the heart. In this situation, follow-up should include not only electrolyte measurements, but also electrocardiograms to detect the harmful effects on the heart.

The symposium presentations highlight the many and complex interrelationships between the heart and kidneys, and the need for more research to apply important scientific advances to care of patients with heart failure, kidney disease, or both. The symposium "is especially aimed at drawing adequate attention to this important topic and its relevance to the practice of medicine," Dr. Weber writes.