Shortness of breath can be caused by lung problems, heart problems, or other medical conditions including anemia. Most everyone has felt winded or short of breath when participating in very strenuous physical activity, extreme weather conditions, or very high altitude. However, when shortness of breath is prolonged, persistent, or occurs in unexpected situations, it may be due to a medical condition that needs evaluation. And, if breathlessness is sudden and severe in intensity, even if it’s of short duration, medical evaluation may be necessary. The most common cardiac cause of shortness of breath is heart failure, especially if it is accompanied by swelling of the legs. In addition to breathlessness with exertion, a person with heart failure may have difficulty in breathing when lying down. Heart valve problems like mitral regurgitation, aortic regurgitation, or aortic stenosis can also cause shortness of breath. One can feel short of breath during an arrhythmia when the heart is beating quickly. A buildup of fluid around the heart can cause shortness of breath as can pericardial constriction. Significant blockages in the coronary arteries (coronary artery disease) can cause chest pain or discomfort. While a heart attack most commonly causes chest pain, a person having a heart attack might experience significant shortness of breath, with or without chest pain. Since shortness of breath can be a sign of heart disease, patients with breathlessness are usually evaluated by cardiologists. In addition to a careful history and a thorough physical exam by a cardiologist, certain cardiac tests might be helpful to determine cardiac causes of shortness of breath. These tests include an EKG, echocardiogram, stress test (including stress echo or myocardial perfusion imaging), or a chest x-ray.