What’s Up Doc column: ‘High output’ cardiac failure can have multiple causes

Dr. Jeff Hersh
Milford Daily News USA TODAY NETWORK
Cherokee County News Advocate

Columns share an author’s personal perspective.


Q: My doctor said I had heart failure even though my heart is pumping too much blood. How can this be?

A: It sounds like you were diagnosed with high output cardiac failure (HOCF, double-check this with your doctor), so that will be the focus of today’s column.

In a healthy patient, the heart pumps a sufficient supply of oxygen and glucose-carrying blood to meet the demands of the body’s cells. The resistance to blood flow (systemic vascular resistance, SVR), which primarily comes from the smaller arteries (the arterioles) that the blood passes through on its way to the cells, is a key factor determining the required volume of blood the heart must pump (cardiac output, CO); the lower the resistance the more “pooling” there is, so a larger CO is required.

Cardiac (heart) failure (CF) can be thought of as a condition where the supply of blood pumped by the heart cannot keep up with the body’s demands. CF is pretty common, affecting more than 6 million Americans. The vast majority of CF cases occur because of a decreased supply due to an issue with the heart pumping less than a normal CO. However, in uncommon cases (the prevalence of this condition is not precisely known), CF occurs because the demand is excessively high, and a normal or even a high CO is not sufficient to satisfy the demand; this is HOCF. 

Symptoms from CF (including HOCF) typically include shortness of breath with exertion (in more severe cases this may occur even with minimal exertion or at rest, and is typically worse when lying flat), fatigue, lower extremity swelling and/or other symptoms.

The evaluation of CF patients involves a complete history and physical exam, certain blood tests (typically including natriuretic peptide and others), an echocardiogram, and other tests to identify the underlying cause (especially in HOCF patients).

Treatment for CF usually includes medications to decrease total body fluid (diuretics), other medications and other supportive measures. Patients with HOCF will also benefit from treatment of the underlying cause of their condition whenever that is possible.

This description shows that patients with HOCF have normal or elevated overall CO but have decreased SVR. There are many possible causes of this condition:

Metabolic causes: In these cases, the body’s cells have abnormally high needs. Examples of this include hyperthyroidism (increased thyroid hormone levels cause the cells to be “hyperactive”); sepsis (where there is a systemic inflammation due to an infection); certain myeloproliferative disorders (blood cancers where the bone marrow produces too many, but abnormal, red blood cells, RBCs); thiamine deficiency (when severe this is called beriberi) since thiamine is needed for cells to efficiently use the “fuel” (oxygen and glucose) delivered to them; morbid obesity (the body’s demand is high because there are so many body cells requiring energy); decreased amount of fuel in the blood requiring extra blood to fill the demand (this can occur from chronic severe low RBCs, i.e. chronic anemia, certain severe lung conditions where the RBCs cannot be adequately loaded with oxygen, others); Paget’s disease (abnormal breakdown of bones); and other conditions.

Disorders where there is a “shortcut” (shunt) for arterial blood to flow directly to the veins: In these cases, some percentage of the blood the heart pumps bypasses the body’s cells and just goes back to the heart. This can occur due to congenital disorders (the patient is born with a condition that causes shunts) or can be acquired (for example, a shunt may develop from certain liver conditions, or even from the intentional creation of a shunt to allow the patient to have hemodialysis for kidney failure, others), or other conditions.

Anyone having symptoms of CF should see their health care provider for evaluation and treatment. If HOCF is diagnosed, further testing for an underlying treatable condition is indicated. Correction of a causative underlying condition can significantly improve the patient’s quality and quantity of life and is indicated whenever possible.
