Heart failure generates two major obstacles for the body: (1) the tissues and organs dont get enough oxygen (poor cardiac output), and (2) fluid builds up in the lungs and tissues. Each of these obstacles may generate characteristic symptoms.
Symptoms of poor cardiac output can include:
Symptoms of fluid buildup (congestion) can include:
As you can see, since many heart failure symptoms are nonspecific and overlap with those of other conditions, they are occasionally misattributed to other causes (aging, poor physical fitness) by doctors or patients.