Cardio-Renal Symposium Reveals How the Heart and Kidneys Interact In Dogs and Cats with Cardiac Disease, Renal Disease, and Systemic Hypertension

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Affected patients’ outcomes are optimized through appropriate diet and drug therapy, including ACE inhibitors, and early intervention

Veterinarians attending Vétoquinol’s Cardio-renal Symposium at the CVC in Kansas City on August 29 heard three leading veterinary internists summarize published research and clinical studies that support:

  • The numerous benefits of using angiotensin-converting enzyme inhibitors (ACEI) in dogs and cats with cardiac disease, renal disease, and hypertension;
  • The crucial reasons to monitor for proteinuria and systemic hypertension in veterinary patients with renal disease; and
  • The fundamental need to restrict dietary phosphorus in dogs and cats with chronic kidney disease.

The keynote speakers were

  • Clarke Atkins, DVM, DACVIM, professor of medicine and cardiology, College of Veterinary Medicine, North Carolina State University
  • Gregory F. Grauer, DVM, MS, DACVIM, professor and Jarvis chair of small animal internal medicine, College of Veterinary Medicine, Kansas State University
  • Larry G. Adams, DVM, PhD, DACVIM, professor of small animal internal medicine, School of Veterinary Medicine, Purdue University

In patients with heart disease and reduced cardiac output, the renin-angiotensin-aldosterone system (RAAS) is activated, which ultimately leads to additional cardiovascular and renal damage. Thus, blunting the effects of the renin-angiotensin-aldosterone system with medications such as an ACEI is beneficial for the heart, kidneys, and general vasculature, says Dr. Clarke Atkins. Yet, when ACEIs were introduced for veterinary patients with heart disease, concern arose that these drugs might contribute to renal disease. However, numerous studies in dogs, cats, and people have dispelled that myth.

“ACE inhibitors are not only not nephrotoxic, but they actually benefit renal function,” said Dr. Atkins. “ACE inhibitors are the cornerstone in the chronic treatment of heart failure. I believe they are indicated in all systolic heart failure, they appear to be safe, they are renal-sparing, particularly with glomerular disease, they play a role as an antihypertensive, they improve duration and quality of life, and they also have benefits prior to the onset of heart failure.” Dr. Atkins wants veterinarians to feel comfortable using ACEIs in patients with phase II cardiac disease and beyond, and recognize that ACEIs are probably indicated from the time proteinuria is identified in patients with renal disease, and finally, that ACEIs are indicated from the time a patient is identified to have systemic hypertension.

Dr. Greg Grauer agrees. “Most of us don’t feel that you can harm patients with renal disease with ACE inhibitors,” says Dr. Grauer. He summarized data that show as more nephrons are lost in association with intraglomerular hypertension, and as glomerulosclerosis, an irreversible lesion, develops, nephrons are replaced with fibrous scar tissue, resulting in a vicious cycle. As more nephrons are lost, “the RAAS brings more vasopressor agents to bear and more tissue remodeling to bear, and at the level of the kidney that’s associated with increased fibrous scar tissue production.” Dr. Grauer is conducting a two-year clinical study at KSU CVM in cats that have stage 2 or 3 chronic kidney disease to compare the effects of Rubenal, a Vétoquinol renal care product that contains medicinal rhubarb to help protect healthy renal tissue by minimizing the effects of cytokine expression, vs. benazepril. He says that data regarding the efficacy of Rubenal should be available at the ACVIM Forum in spring 2011.

Dr. Grauer summarized studies that reveal that proteinuria and systemic hypertension, which result from activation of the RAAS, are things that DVMs should be concerned about and testing, monitoring, and eventually treating for.

Dr. Grauer left his colleagues in the audience with an important question: Are proteinuria and hypertension simply markers of more severe chronic kidney disease that is more likely to be rapidly progressive, or do one or both mediate progressive renal injury? “If they do mediate progressive renal injury, then treatments designed to attenuate them, to lower or normalize blood pressure or to reduce proteinuria, are likely to be renoprotective and improve survival,” adds Dr. Grauer.

Dr. Larry Adams reviewed well-known studies that show feeding a renal diet—one that is protein- and phosphorus-restricted—vs. a maintenance diet delays the onset of clinical signs of uremia and improves survival in dogs and cats with chronic kidney disease. “Phosphorus restriction is probably fundamental to any renal diet and is critical,” says Dr. Adams. Dr. Adams emphasized the importance of treating renal secondary hyperparathyroidism, an often-overlooked aspect of treating chronic kidney disease.

Veterinarians overlook this condition because these patients’ serum phosphorous concentration is often within the reference range. However, Dr. Adams says that veterinarians must aim for a serum phosphorous concentration that remains in the low normal range—less than 5 mg/dl in patients with stage 2 and 3 kidney disease, and no higher than 6 in patients with stage 4 chronic kidney disease.

In order to achieve that, Dr. Adams says veterinarians should start by feeding a renal diet, then add an intestinal phosphate binder if the phosphorous concentration is normal but not within that target low-normal range. In a study published in 2008 from the University of Georgia, Epakitin, a chitosan-based nutritional supplement from Vétoquinol that binds phosphate in the intestine, was shown to significantly reduce serum phosphorous and parathyroid hormone concentrations in cats with stage 2 chronic kidney disease within 56 days without raising calcium levels.

Intestinal phosphate binders that can be mixed directly in the food, are effective, and palatable, such as Epakitin, will be of greatest benefit and most economical in patients with chronic kidney disease, says Dr. Adams.

About Vétoquinol
Vétoquinol USA, based in Fort Worth, Texas, is owned by Vétoquinol, an independent veterinary pharmaceutical company serving both the companion and production animal markets. This family-owned group, dedicated exclusively to animal health, is the 9th largest animal health care company in the world. More than 80 percent of its revenues are generated outside France.

Vétoquinol's business includes research and development, production and marketing of medicinal and non-medicinal products. Vétoquinol has positioned itself in the curative sector and has developed expertise in three therapeutic fields: anti-infectives, pain and anti-inflammatory, and cardiology/nephrology.

The Group currently distributes its products in more than 100 countries throughout Europe, North American and Asia/Pacific, with subsidiaries in 23 countries and a network of 140 distribution partners. The company has more than 1,550 employees worldwide.
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Autumn Blankenship

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