Heart disease: a low-sodium diet plan that reduces the cardiac workload

Heart disease in dogs and cats is managed with a combination of medications (pimobendan, ACE inhibitors, diuretics), lifestyle modifications (exercise restriction, weight management), and dietary modifications. The dietary modification is the cornerstone of the long-term management, and the dietary modification is the focus of this article. The dog or cat with heart disease is the patient that retains sodium and water, and the retention increases the blood volume and the cardiac workload. The low-sodium diet reduces the sodium and the water retention, and the reduced retention reduces the cardiac workload. The dog or cat on the low-sodium diet has fewer episodes of congestive heart failure, has a longer time between the medication adjustments, and has a longer survival. In this article I will walk through why sodium matters in heart disease, the sodium targets for the different stages, the prescription diets, the home-cooked alternative, the treats, and the monitoring that catches the problems.

Why sodium matters in heart disease

The heart's primary function is to pump blood through the body, delivering oxygen and nutrients to the tissues and removing waste products. The blood volume is one of the primary determinants of the cardiac workload — the more blood, the more work the heart has to do. The blood volume is regulated by the kidneys, which control the sodium and water balance. The kidneys retain sodium when the body is sodium-depleted, and the kidneys excrete sodium when the body is sodium-replete.

In heart disease, the cardiac output is reduced, and the reduced output is perceived by the kidneys as low blood pressure. The kidneys respond to the perceived low blood pressure by retaining sodium and water, and the retention increases the blood volume. The increased blood volume is initially helpful (it increases the cardiac output by increasing the preload), but the increased blood volume is eventually harmful (it increases the cardiac workload, it increases the blood pressure, and it leads to fluid accumulation in the lungs and the abdomen — the congestive heart failure).

The low-sodium diet reduces the dietary sodium intake, and the reduced intake reduces the sodium and water retention. The reduced retention reduces the blood volume, the reduced blood volume reduces the cardiac workload, and the reduced workload slows the progression of the heart disease. The dog or cat on the low-sodium diet has fewer episodes of congestive heart failure, has fewer medication adjustments, and has a longer survival.

The sodium targets for the different stages

The sodium targets vary by the stage of the heart disease, and the targets are matched to the severity of the disease.

Early heart disease (IRIS Stage B1 for dogs, asymptomatic HCM for cats). The sodium target: 50-80 mg per 100 kcal of food, or roughly 0.1-0.2% sodium on a dry matter basis. This is a moderate reduction from the standard maintenance food (which is typically 0.3-0.5% sodium on a dry matter basis), and the reduction is enough to slow the progression without being so restrictive that the pet refuses to eat.

Moderate heart disease (IRIS Stage B2 for dogs, mild HCM with clinical signs for cats). The sodium target: 40-60 mg per 100 kcal of food, or roughly 0.08-0.15% sodium on a dry matter basis. This is a more significant reduction, and the reduction is matched to the increased sodium retention in the moderate disease.

Advanced heart disease (IRIS Stage C for dogs, congestive heart failure for cats). The sodium target: 30-50 mg per 100 kcal of food, or roughly 0.05-0.1% sodium on a dry matter basis. This is a strict reduction, and the reduction is matched to the severe sodium retention in the advanced disease.

The sodium targets are guidelines, not absolutes. The actual sodium restriction is matched to the individual dog or cat, with the vet adjusting the target based on the response to the medication, the blood pressure, the degree of the fluid retention, and the overall clinical picture.

The prescription cardiac diets

The prescription cardiac diets are formulated by the major veterinary diet manufacturers, and the diets meet the sodium targets for the different stages. The most common prescription cardiac diets:

• Hill's Prescription Diet h/d (Heart Diet). The original cardiac diet, formulated for the early and moderate heart disease. The sodium is reduced to 0.08% on a dry matter basis, and the protein is moderately restricted. The diet is available in dry and wet formulations.

• Royal Canin Cardiac. The cardiac diet for the early and moderate heart disease. The sodium is reduced to 0.1% on a dry matter basis, and the protein is moderately restricted. The diet contains the specific fatty acids and the antioxidants that support the cardiac function.

• Purina Pro Plan Veterinary Diets CardioCare. The cardiac diet for the early and moderate heart disease. The sodium is reduced to 0.07% on a dry matter basis, and the protein is moderately restricted. The diet contains the specific fatty acids and the antioxidants that support the cardiac function.

The prescription cardiac diets should be fed as the primary diet, and the prescription cardiac diets should be the only diet during the heart disease management. The mixing of the prescription diet with the maintenance food undermines the sodium restriction, and the mixing is not recommended.

The home-cooked alternative

The home-cooked cardiac diet can be formulated by a board-certified veterinary nutritionist, and the home-cooked diet can meet the sodium targets. The advantage of the home-cooked diet: the owner controls the ingredients, the ingredients are fresh, and the palatability is often better than the prescription diet. The disadvantage: the home-cooked diet requires the recipe to be formulated, the recipe to be followed precisely, and the supplements to be added. The home-cooked diet without the supplements is nutritionally incomplete.

The home-cooked cardiac diet recipe is typically: a lean protein source (chicken breast, turkey breast, or white fish), a low-sodium carbohydrate (white rice or sweet potato), a low-sodium vegetable (green beans, carrots, or zucchini), and a supplement mix (calcium, vitamins, minerals, omega-3, taurine for cats). The recipe is formulated by the nutritionist based on the specific dog or cat, and the recipe is updated as the disease progresses.

The home-cooked diet is not a substitute for the prescription diet in the advanced heart disease. The prescription diet is formulated for the specific stage of the disease, and the home-cooked diet may not meet the specific sodium target for the advanced disease. The home-cooked diet is best for the early and moderate disease, and the home-cooked diet should be transitioned to the prescription diet for the advanced disease.

The treats

The treats that are appropriate for the heart disease patient: small pieces of the prescription diet kibble, small pieces of fresh apple or banana, small pieces of cooked carrot, freeze-dried single-ingredient treats that are low in sodium. The treats that are not appropriate: most commercial dog and cat treats (which are high in sodium), cheese (very high in sodium), jerky (very high in sodium), deli meats (very high in sodium), most human foods (which contain added salt).

The owner who is giving the heart disease patient a commercial treat is the owner who is undermining the sodium restriction. The owner who is giving the heart disease patient a "small piece" of cheese is the owner who is adding 50-100 mg of sodium to the daily intake, which is a significant portion of the daily sodium budget. The fix: the treats are on the approved list, and the treats are measured and counted.

The monitoring

The monitoring: weight (the heart disease patient should be weighed weekly, with the weight changes tracked), body condition score (the heart disease patient should be at a lean to moderate BCS), respiratory rate at rest (the heart disease patient should have a respiratory rate below 30 breaths per minute at rest, with the rate logged daily), and blood pressure (the heart disease patient should have the blood pressure checked at every recheck, with the systolic below 160 mmHg).

The weight change is the most important monitoring. The heart disease patient that gains weight rapidly (more than 1 kg in a week) is the heart disease patient that is accumulating fluid, and the fluid accumulation is the sign that the heart failure is decompensating. The owner who notices the rapid weight gain and contacts the vet is the owner who can prevent the emergency.

The one-page summary

Heart disease is managed with medications, lifestyle modifications, and dietary modifications. The dietary modification is the cornerstone of the long-term management. The sodium targets: 50-80 mg/100 kcal for early, 40-60 mg/100 kcal for moderate, 30-50 mg/100 kcal for advanced. The prescription cardiac diets: Hill's h/d, Royal Canin Cardiac, Purina CardioCare. The home-cooked alternative: formulated by a veterinary nutritionist. The treats: on the approved list, measured and counted. The monitoring: weight, BCS, respiratory rate, blood pressure. The owner who runs the protocol is the owner whose pet has fewer episodes of congestive heart failure and a longer survival. The protocol is the work. The protocol is what makes the difference.