Cardiac asthma is actually not the asthma but it is a medical symptom known as “paroxysmal dyspnea” or “paroxysmal nocturnal dyspnea (PND)”. PND is caused due to increased amount of fluid entering the lungs during sleep and filling the small, air-filled sacs called alveoli in the lungs which absorbs oxygen from the air.

During the day time when the person is upright, this fluid is present in the legs of the person. In the night time, when recumbent for an extended period, the fluid is reabsorbed thus increasing the blood volume and increased blood pressure and causing pulmonary hypertension in people with underlying left ventricular dysfunction. The state of pulmonary hypertension leads to the accumulation of fluid in the lungs i.e. pulmonary edema.

 In cardiac asthma, the pumping efficacy of the heart is considerably decreased causing back pressure from left part of the heart and towards the lungs. It therefore causes a sudden imbalance and disproportion between the work load and work capacity in the left side of the heart.

Cardiac asthma is somewhat similar to lung asthma. The patients suffering from these asthma experience shortening of breath, wheezing and coughing due to heart failure or improper opening of the heart valves.