Cardiac asthma is a term used to describe asthma-like symptoms that can occur with left-sided heart failure, a condition in which a lower chamber of the heart (called the left ventricle) is unable to pump blood efficiently. When this occurs, it can cause respiratory symptoms such as shortness of breath and wheezing that can easily be mistaken for asthma.
Because the causes of asthma and heart failure are different, a correct diagnosis is vital: If cardiac asthma were to be treated with certain asthma medications, the heart failure may get worse.
Cardiac Asthma Symptoms
The respiratory symptoms of left ventricular failure can mimic those of asthma, particularly in the earlier stages of the disease. They may include:
- Wheezing
- Chest tightness
- Cough
- Shortness of breath
For some people, the respiratory symptoms of heart failure may be the first or most prominent symptoms. But, more often than not, they will occur alongside other symptoms, some of which may be missed or attributed to other causes, among them:
- Chronic fatigue
- Persistent weakness
- Shortness of breath when lying flat or exercising
- Unexpected weight gain with fluid retention
- Lack of appetite or nausea
- Edema (tissue swelling, mainly of the lower extremities)
- Difficulty concentrating
- Rapid or irregular heartbeat
- Increased need to urinate at night (nocturia)
Symptoms like these, particularly ones that are persistent or worsening, can indicate something other than asthma is involved. Cardiac asthma is especially common in the elderly, nearly a third of whom will present with wheezing when first diagnosed.
Causes
Left-sided heart failure occurs when decreased cardiac output causes fluid to accumulate in the body. The backup of fluid into the lungs (called pulmonary edema) can manifest with breathing problems as the airways and tiny air sacs of the lungs begin to fill with fluid.
Asthma attacks tend to develop and end abruptly, and the majority of people fully recover with no lasting effects. The chronic, progressive nature of heart failure is such that symptoms like shortness of breath, cough, and fatigue may improve for a short time, but will almost invariably persist until the appropriate treatment is received.
While these effects may seem similar to those that occur with asthma, they are instead owed to inflammation and narrowing of the airways.
Certain risk factors also differentiate the two diseases. Broadly speaking, heart failure will usually occur with other chronic health conditions, such as:
- High blood pressureDiabetesObesitySmokingCoronary artery diseaseA previous heart attack or heart injuryHeart rhythm disordersHeart valve problems
Asthma, on the other hand, can affect even the most healthy of individuals.
Diagnosis
Because the symptoms of cardiac asthma mimic those of true asthma, misdiagnosis is possible. A review of risk factors, medical history, and non-respiratory symptoms can suggest other possibilities.
Even if the initial symptoms point to a possible diagnosis of asthma, an evaluation of lung sounds using a stethoscope can often differentiate asthma from other conditions like heart failure.
These sounds are not characteristic of asthma. Even during an attack, asthma chest sounds are usually limited to wheezing (a high-pitched whistling noise) during exhalation.
With left-sided heart failure, popping sounds (called rales or crackles) can often be heard when air tries to pass through fluid-filled airways. There may also be a so-called “third-heart sound” in which the two normal heartbeats are accompanied by a vibrating noise as the ventricle fills with blood.
Lab Tests and Procedures
Based on initial findings, your healthcare provider will order tests to investigate further. If asthma is suspected, you would generally be referred to a pulmonologist or pulmonology lab for evaluation with in-office spirometry and other pulmonary function tests (PFTs).
If heart failure is suspected, a number of common lab tests, imaging studies, and procedures can be performed to confirm the diagnosis. You may get these initially or only after pulmonary tests have been conducted and reviewed:
- B-type natriuretic peptide (BNP), a blood test that detects a hormone released with increased ventricular pressure
- Echocardiogram, a non-invasive ultrasound test that can visualize how well your heart is pumping
- Electrocardiogram (ECG), used to measure the electrical impulses during heartbeats to detect irregularities
- Stress testing, in which your ECG and respiratory function are evaluated while exercising on a treadmill or stationary bike
- Cardiac magnetic resonance imaging (MRI), a detailed imaging study of the heart using powerful magnetic and radio waves
- Computed tomography (CT) angiography, a 3-D imaging study using a series of X-rays to map the structure of the heart
- Chest X-ray, generally less useful in diagnosis but that may help identify other anatomic abnormalities to exclude other causes of heart dysfunction
It is important to seek a full and proper diagnosis of your condition whether heart failure or asthma is suspected.
A 2017 study in the journal JAMA reported that no less than 33% of adults previously diagnosed with asthma were, in fact, misdiagnosed. Of the 213 participants in the study, 12 were found to have a serious cardiorespiratory illness.
A diagnosis of asthma is complicated. If you’re being treated for asthma based on symptoms and non-specific PFTs (like pulse oximetry), advocate for yourself and ask your healthcare provider about additional testing options.
Treatment
The treatment of left-sided heart failure depends largely on the severity of the disease and the degree of cardiovascular impairment. Cardiac asthma symptoms may also be treated, but never in isolation.
The treatment of heart failure typically involves medications to improve cardiac output, reduce blood pressure, and alleviate structural stress in the affected ventricle. This alone can help relieve cardiac asthma symptoms in many people, particularly those with less severe disease.
Drugs commonly used to treat heart failure include:
- Angiotensin-converting enzyme (ACE) inhibitors, high blood pressure medications commonly used if the heart failure is systolic (occurring when the heart is contracting)
- Angiotensin II receptor blockers (ARBs), used when ACE inhibitors can’t be tolerated
- Beta-blockers, which reduce blood pressure by slowing the heart rhythm
- Digoxin, used to strengthen heart contractions in people with systolic heart failure
- Diuretics (“water pills”), which reduce blood pressure by promoting urination
- Nitrates, a class of drugs that decreases the left ventricle filling pressure and modestly improves cardiac output
Cardiac asthma symptoms may be directly treated but generally in those with advanced heart failure. There is no evidence that short-acting beta-agonists (a.k.a. “rescue inhalers”) relieve acute symptoms in people with cardiac asthma, so they are generally not useful.
In more advanced cases, fluid aspiration (extraction with a needle) may be needed to relieve pressure on the heart. Intravenous nitrates (delivered via injection into a vein) may also be recommended along with oxygen therapy.
People with cardiac asthma who are inappropriately treated with asthma medications run the risk of “masking” the symptoms of heart failure. Moreover, the use of long-acting bronchodilators, often prescribed to people with persistent asthma, may increase the cardiovascular risk in older people.
People approaching end-stage heart failure may need morphine. The drug works by relaxing airways and blood vessels and can significantly relieve breathing impairment.
A Word From Verywell
Cardiac asthma is a misleading term and one that highlights the confusion that can arise when diagnosing asthma-like symptoms. As a symptom of heart disease, cardiac asthma is not treated on its own. It requires the care of a cardiologist able to diagnose, treat, and manage left-sided heart failure. With appropriate care, the respiratory symptoms of heart failure can ease along with the other symptoms.
