Dyspnea, especially with exertion, is one of the most
common symptoms of heart failure, and it frequently
appears early in the disease. In the early stages of heart
failure, dyspnea occurs with severe exertion, but as the
heart failure worsens the amount of exertion required
to produce dyspnea progressively decreases. According
to a study that assessed the features of heart failure,
the absence of dyspnea on exertion essentially ruled
out the presence of heart failure due to left ventricular
dysfunction.12 Dyspnea on exertion has a sensitivity of
84% to 100% in the diagnosis of heart failure, but the
specificity is much lower, ranging from 17% to 34%.12,13
Dyspnea presents in other forms, including orthopnea
and paroxysmal nocturnal dyspnea (PND).