On confirmation of low cardiac output unrelated to hypovolemia, attempts should be made to identify the cause. Significant
arrhythmias usually can be ruled out on auscultation, but if an arrhythmia is heard or suspected, ECG and/or Holter (24-hour
ambulatory ECG) may be required to guide therapy. Even inappropriate sinus tachycardia (those unrelated to hypovolemia or
pain) can be deleterious and may need to be managed with judicious beta-blockade (very low dose titrated to effect) or digoxin.
An echocardiogram may be useful to determine the presence and severity of pulmonary hypertension or pericardial effusion as
well as progressive pump failure (especially when compared to previous echo studies).
Pericardial effusion causing tamponade may require pericardio- centesis (very uncommon when due to heart failure). If moderate
to severe pulmonary hypertension is documented and suspected of contributing to reduced cardiac output, the cause for the
pulmonary hyper- tension should be investigated (ruling out heartworm disease, hyperadreno- corticism, pulmonary thrombo-
embolism) but chronic valvular disease (CVD) is one of the most common underlying causes for pulmonary hypertension. Regardless
of the cause of pulmonary hypertension, dogs with severe pulmonary hypertension may benefit from the addition of sildenafil
(1-3 mg/kg BID). Additional therapies for pulmonary hypertension should be guided by the underlying cause. Progressive pump
failure and pulmonary hypertension may be palliated by increasing the dosing frequency of pimobendan from BID to TID (0.25-0.3
Overzealous afterload reduction can be considered by exclusion of other causes of low cardiac output. Significant pulmonary
edema (enough to lead to anorexia or inappetence) also will result in signs of respiratory distress. Clinically significant
ascites (abdominal distention) secondary to heart failure confirms a diagnosis of elevated right-heart pressures and leads
to passive gastrointestinal congestion, which can lead to absorption and motility problems. In addition, significant ascites
can lead to respiratory distress and discomfort which can indirectly lead to anorexia and/or inappetence.
Some heart-failure medications, such as digoxin, may alter taste in some dogs or have adverse central effects on appetite.
Typically, this is noticed on initiation of the medication and in the case of digoxin may even occur when blood levels are
within the therapeutic range. Other therapies, particularly anti-arrhythmics, may cause increases in serum liver enzymes which
can contribute to loss of appetite.
The bodies of animals with heart failure are under stress, suffer from chronic reductions in cardiac output passive GI congestion
and, in combination these factors, may lead to GI stasis and ulceration, both of which can contribute to loss of appetite.
Dietary indiscretion frequently is a consequence and potentially a cause of anorexia and inappetence. Many dogs with advanced
heart failure are fed a variety of food because owners want to "treat them special" and most of these dogs develop some degree
of inappetence. Part of acquired inappetence may be related to food avoidance in dogs that resent receiving medications in
food and thus become more and more "picky." It is difficult to treat this problem. A variety of approaches can be used, such
as separating the feeding and pill administration, and the person who feeds should never administer medication. Novel food
presentations such as homemade diets can be tried.
Behavioral causes should be considered only after ruling out other more obvious causes of loss of appetite. Common non-cardiac
causes that may lead to, or contribute to, loss of appetite include severe periodontal disease leading to pain when eating.
Even in dogs with advanced heart failure, tooth extractions (with appropriate precautions and owner consent) may be necessary
to improve quality of life. In milder to moderate forms of periodontal disease, an antibiotic course may be beneficial.
Some dogs in heart failure have no obvious cardiovascular or non-cardio- vascular cause for inappetence. In these animals,
low-dose corticosteroids and other appetite stimulants in combination with basic GI supportive care such as famotidine sucralfate.
When possible, multiple therapeutic changes should not be done concurrently, but rather one or two changes made at a time
and response should be evaluated to guide additional alterations.
Cough, dyspnea and tachypnea
Progressive, incessant life-limiting cough with or without tachypnea or dyspnea is a common complaint in advanced canine heart
failure, particularly in dogs with chronic valvular disease. Other common non-cardiogenic causes for cough are concurrent
collapsing trachea and chronic obstructive pulmonary disease (COPD). The most common causes of cardiovascular-related cough
in dogs with heart failure include pulmonary edema and left atrial enlargement causing left mainstem bronchus compression.