Cardiac causes of fainting are generally life threatening. Electrical problems of the heart impairs its pumping ability. This produces a decrease in blood flow. The heart rate may be either too fast or too slow to pump blood well. This condition usually causes fainting without any warning symptoms.
Cardiac obstruction can cause fainting during physical exertion.
A variety of diseases cause obstruction, including heart attacks, diseased heart valves, pulmonary embolism, cardiomyopathy, pulmonary hypertension, cardiac tamponade, and aortic dissection. Seizures are another cause of unconsciousness, but are different from fainting, in that there is not a decrease in blood flow to the brain. Unconsciousness results from disordered electrical discharges within the brain. Other rare causes include glossopharyngeal neuralgia and migraine. Rarely, people may pretend to faint to minimize stress or for some recognized gain.