Shortness of breath, medically known as dyspnea, is one of the most common symptoms that brings people to seek medical attention. This uncomfortable sensation of not being able to breathe adequately can be both frightening and confusing, especially when trying to determine its underlying cause.
While shortness of breath can stem from various conditions, two of the most significant categories involve cardiac (heart-related) and pulmonary (lung-related) causes.
Understanding the differences between these two origins can help you recognize when to seek immediate medical care and provide valuable information to healthcare providers.
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How Can You Tell if Shortness of Breath is from the Heart or the Lungs?
Shortness of breath can result from heart or lung problems, and distinguishing between the two often depends on the presence of accompanying symptoms and the results of diagnostic tests. If the cause is heart-related (such as heart failure), you may notice swelling in the legs, fatigue, rapid weight gain, or shortness of breath that worsens when lying down or during nighttime.
Lung-related causes (such as asthma, COPD, or pneumonia) often involve symptoms like coughing, wheezing, or chest tightness. Doctors may perform a physical exam, chest X-ray, EKG, echocardiogram, or pulmonary function tests to determine the origin. Oxygen levels and blood tests can also provide clues. In some cases, both the heart and lungs contribute to the symptoms, so a thorough evaluation is essential.
Understanding the Mechanics of Breathing
To distinguish between heart and lung-related shortness of breath, it’s essential to understand how these two organ systems work together. The respiratory system brings oxygen into the lungs and removes carbon dioxide from the body.
Meanwhile, the cardiovascular system pumps blood to transport oxygen from the lungs to tissues throughout the body and carries carbon dioxide back to the lungs for elimination.
Note: When either system fails to function properly, the result can be dyspnea. However, the specific characteristics, timing, and accompanying symptoms often differ depending on whether the problem originates in the heart or lungs.
Heart-Related Shortness of Breath
Heart-related shortness of breath typically develops due to the heart’s inability to pump blood effectively, leading to fluid buildup in the lungs or reduced oxygen delivery to tissues. This condition, known as heart failure, can manifest in several distinct patterns.
- Orthopnea is perhaps the most characteristic sign of cardiac dyspnea. This refers to shortness of breath that occurs when lying flat and improves when sitting up or sleeping with multiple pillows. The reason for this pattern is that when lying flat, blood from the lower extremities returns to the heart more readily, overwhelming an already compromised cardiac system and causing fluid to back up into the lungs.
- Paroxysmal nocturnal dyspnea is another hallmark of heart-related breathing problems. This involves sudden episodes of severe shortness of breath that wake patients from sleep, typically occurring 2-4 hours after going to bed. Patients often describe having to sit up or stand by an open window to catch their breath.
- Exertional dyspnea related to heart problems tends to be progressive and predictable. Patients may notice they can no longer climb stairs or walk distances they previously managed easily. The shortness of breath typically correlates with the level of physical activity and improves with rest.
Associated Symptoms
Heart-related dyspnea often comes with other cardiovascular symptoms. These may include chest pain or pressure, especially during exertion, irregular heartbeat or palpitations, swelling in the legs, ankles, or feet (edema), and fatigue that seems disproportionate to activity level.
Patients might also experience a persistent cough, particularly when lying down, which may produce pink or blood-tinged sputum. This occurs because fluid accumulation in the lungs can cause irritation and inflammation of the airways.
Common Cardiac Causes
Several heart conditions can lead to dyspnea. Congestive heart failure occurs when the heart muscle becomes weakened or stiffened, reducing its ability to pump blood effectively. Coronary artery disease can cause shortness of breath during exertion when the heart muscle doesn’t receive an adequate oxygen supply.
Heart valve problems, such as mitral or aortic valve stenosis or regurgitation, can also lead to breathing difficulties as the heart works harder to compensate for inefficient blood flow.
Arrhythmias or irregular heart rhythms can cause sudden episodes of shortness of breath, particularly if they significantly affect the heart’s pumping efficiency. Cardiomyopathy, a disease of the heart muscle itself, can progressively worsen, leading to increasing dyspnea over time.
Lung-Related Shortness of Breath
Pulmonary dyspnea typically results from problems with air movement in and out of the lungs or with gas exchange within the lungs. The patterns and characteristics often differ significantly from those caused by cardiac issues.
Inspiratory dyspnea is more common with lung problems, where patients have particular difficulty breathing in. This contrasts with cardiac dyspnea, which often affects both inspiration and expiration. The breathing may sound wheezy, crackling, or labored, with visible use of accessory muscles in the neck and chest.
Lung-related shortness of breath may worsen with specific triggers such as allergens, cold air, exercise, or exposure to irritants like smoke or strong odors. Unlike cardiac dyspnea, position changes may not significantly improve breathing, although some patients with chronic obstructive pulmonary disease (COPD) find relief by leaning forward.
Associated Symptoms
Pulmonary dyspnea often accompanies other respiratory symptoms. A persistent cough is common, which may be dry or productive of sputum. The color and consistency of sputum can provide clues about the underlying condition – yellow or green sputum may indicate infection, while clear sputum might suggest asthma or allergic reactions.
Wheezing is a high-pitched whistling sound during breathing that’s particularly common with asthma and COPD. Chest tightness is another frequent complaint, often described as feeling like a band around the chest or having difficulty expanding the lungs fully.
Patients may also experience pleuritic chest pain, which is sharp and worsens with deep breathing or coughing. This type of pain is distinctly different from the pressure-like chest pain associated with heart problems.
Common Pulmonary Causes
Asthma is characterized by airway inflammation and constriction, leading to wheezing, coughing, and shortness of breath, often triggered by specific allergens or irritants. Chronic obstructive pulmonary disease (COPD), including emphysema and chronic bronchitis, typically develops gradually and is often related to smoking history.
Pneumonia can cause acute shortness of breath along with fever, chills, and a productive cough. Pulmonary embolism, a blood clot in the lung arteries, can cause sudden, severe shortness of breath along with chest pain and sometimes coughing up blood.
Interstitial lung disease involves scarring of the lung tissue, leading to progressive shortness of breath and a dry cough. Pleural effusion, fluid accumulation around the lungs, can cause breathing difficulties that worsen when lying on the affected side.
Key Distinguishing Features
Several important differences can help distinguish between cardiac and pulmonary causes of shortness of breath:
- Timing and Position: Heart-related dyspnea typically worsens when lying flat and improves when sitting up, while lung-related dyspnea may not show significant positional changes. Heart problems often cause nighttime awakening with breathing difficulties, while lung issues may be more constant throughout the day.
- Associated Symptoms: Cardiac dyspnea often accompanies leg swelling, whereas pulmonary dyspnea is more commonly associated with cough and sputum production. Heart-related shortness of breath may be accompanied by chest pressure, while lung problems may cause sharp, stabbing chest pain.
- Response to Treatment: Heart-related dyspnea often improves with diuretics (water pills) and heart medications, while lung-related dyspnea responds better to bronchodilators and respiratory treatments.
- Progression: Cardiac dyspnea often follows a pattern of worsening with activity and improving with rest, while pulmonary dyspnea may be more variable depending on triggers and environmental factors.
When to Seek Medical Attention
Regardless of the suspected cause, certain symptoms require immediate medical evaluation. These include the sudden onset of severe shortness of breath, chest pain accompanying breathing difficulties, shortness of breath with fever, bluish discoloration of lips or fingernails, inability to speak in full sentences due to breathlessness, and shortness of breath that doesn’t improve with rest.
Note: Progressive worsening of breathing difficulties over days or weeks also warrants medical evaluation, as does new onset of orthopnea or paroxysmal nocturnal dyspnea.
Diagnostic Approaches
Healthcare providers use various tools to distinguish between cardiac and pulmonary causes of dyspnea. These may include chest X-rays to visualize the heart and lungs, echocardiograms to assess heart function, pulmonary function tests to evaluate lung capacity and airflow, blood tests including BNP (brain natriuretic peptide) levels, which can indicate heart failure, and arterial blood gas analysis to assess oxygen and carbon dioxide levels.
FAQs About Shortness of Breath
How to Differentiate Between Cardiac and Respiratory Breathlessness?
Cardiac breathlessness often worsens when lying down or during physical activity and may be accompanied by leg swelling, fatigue, or chest discomfort. It’s commonly caused by conditions like heart failure or arrhythmias. Respiratory breathlessness, on the other hand, typically involves symptoms such as coughing, wheezing, or chest tightness and is associated with lung conditions like asthma, COPD, or pneumonia.
Note: Diagnostic tools, such as chest X-rays, EKGs, echocardiograms, and pulmonary function tests, help healthcare providers determine the exact cause.
What Does Cardiac Shortness of Breath Feel Like?
Cardiac shortness of breath often feels like a heavy, suffocating sensation that worsens with exertion or when lying flat. You may wake up at night gasping for air or feel breathless after climbing stairs or walking short distances. This type of breathlessness can also be accompanied by fatigue, rapid heartbeat, swelling in the legs, or chest pain.
Note: These symptoms are commonly associated with heart failure, valve disease, or coronary artery disease and should be evaluated by a healthcare provider promptly.
What Are the Most Common Causes of Shortness of Breath?
Shortness of breath can stem from a wide range of conditions. Common cardiac causes include heart failure, coronary artery disease, and arrhythmias. Respiratory causes include asthma, chronic obstructive pulmonary disease (COPD), pneumonia, and pulmonary embolism.
Other potential triggers include anemia, obesity, anxiety, or deconditioning. Environmental factors, such as high altitude or poor air quality, may also contribute. Identifying the cause typically requires a thorough medical history, physical examination, and various diagnostic tests, including chest X-rays, EKGs, blood work, and lung function tests.
How Do I Know What’s Causing My Shortness of Breath?
To determine the cause of shortness of breath, consider when and how it occurs. Is it triggered by activity, lying down, or exposure to allergens? Associated symptoms, such as chest pain, swelling, wheezing, or cough, can provide additional clues.
A medical evaluation is essential and may include a physical examination, imaging tests (such as a chest X-ray), an EKG, an echocardiogram, blood tests, or pulmonary function tests. These results help your doctor pinpoint whether the cause is cardiac, respiratory, or something else entirely.
Can Shortness of Breath Be Prevented?
In many cases, yes—shortness of breath can be prevented or minimized by addressing underlying conditions. For heart-related causes, managing blood pressure, cholesterol, and weight is key. For respiratory causes, avoiding smoking, reducing exposure to pollutants, and treating chronic lung diseases are crucial.
Staying physically active and maintaining a healthy weight also helps support heart and lung function. Regular check-ups and early treatment of symptoms can prevent mild breathlessness from becoming a more serious health concern.
Final Thoughts
While shortness of breath can be concerning, understanding the differences between heart and lung-related causes can help you communicate more effectively with healthcare providers and recognize when immediate medical attention is needed. Cardiac dyspnea often involves positional changes, nighttime symptoms, and associated swelling, while pulmonary dyspnea frequently includes cough, wheezing, and response to specific triggers.
Please note that these are general guidelines, and individual presentations may vary significantly. Some patients may have both heart and lung problems contributing to their symptoms. The most important step is to seek appropriate medical evaluation for persistent or concerning shortness of breath, as early diagnosis and treatment can significantly improve outcomes for both cardiac and pulmonary conditions.
Never attempt to self-diagnose or delay seeking medical care for significant breathing difficulties. Healthcare providers have the training and tools necessary to accurately determine the cause of dyspnea and develop appropriate treatment plans tailored to your specific condition.
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Hashmi MF, Modi P, Basit H, et al. Dyspnea. [Updated 2023 Feb 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025.