Fatigue is a nonspecific symptom which can occur in multiple disorders.
In heart disease, fatigue is often due to low cardiac output and may occur in heart failure, severe aortic stenosis and mitral stenosis. Severe pulmonary hypertension may also manifest as undue fatigue.

Syncope is transient loss of consciousness with loss of postural tone so that the person falls down. A less severe symptom is called near-syncope. Syncope is due to transient global cerebral hypoperfusion. There are several cardiac and noncardiac causes for syncope. But the commonest is neurocardiogenic syncope which is self-limited. Syncope can occur at rest as in arrhythmic syncope or with exertion in severe aortic stenosis. A much simpler cause is severe anemia. Syncope may be preceded by warning symptoms like blurred vision, sweating or yawning.

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