Shortness of breath: A common symptom with many possible causes

Heart and lung issues are often to blame for breathlessness. But an accurate diagnosis may require advanced testing.

Like your heartbeat, the regular inhale and exhale of your breathing is something you usually don't notice — until something doesn't feel quite right. Shortness of breath can result from a range of problems, including an allergic reaction, an anxiety attack, or anemia. But most often, the underlying cause is a heart or lung condition.

"Because these two organ systems are so intertwined, one always affects the other," says Dr. Aaron B. Waxman, who directs the Pulmonary Vascular Disease Program at Harvard-affiliated Brigham and Women's Hospital. In fact, about 60% of people with heart disease also have a lung disease. As a result, it's not always easy to distinguish cardiac and pulmonary issues, he says.