Dear Doctor Column, August 30, 2004

Fainting Not Usually Cause of Concern

Question:

I'm a 67-year-old man who is slightly overweight. Recently, after a large meal, I sat down in the den to watch TV. I started to get up to get the remote and passed out. My wife says I was out cold for several minutes. She called 911, and the paramedics took me to the emergency room. The doctor told me I had a vaso attack and not to worry about it. What is a vaso attack? Should I be concerned?

Answer:

Your doctor was probably referring to a vasovagal attack that sometimes results in fainting and generally is no cause for concern. Vaso refers to blood vessels, or the vascular system, and vagal to a nerve that controls many involuntary functions such as heart rate, sweating, and blood vessel dilation. A vasovagal attack involves overstimulation of the vagus nerve, which results in dilation of blood vessels and a sudden fall in blood pressure. When the brain doesn't get enough blood or oxygen, you lose consciousness, or faint. After several minutes of lying flat, blood flow to the brain returns to normal and you regain consciousness.

Just getting up too quickly from a lying or sitting position can cause some people to feel dizzy or faint. Normally, when you stand up, your sympathetic nervous system releases adrenalin, which speeds your heart rate and increases blood pressure to preserve blood and oxygen flow to the brain. Occasionally, especially in older people and people on some heart or blood pressure medicines, these responses are slower than normal allowing blood to pool in the legs, which causes a sudden drop in blood pressure and fainting.

A vasovagal attack can be brought on by eating a large meal, by emotional stress or anxiety, or by sudden pain. All these factors stimulate the vagus nerve, which slows the heart rate and dilates blood vessels, allowing blood to pool in the legs. In addition to fainting, vagal nerve stimulation often causes pallor, a cold sweat, and nausea.

While episodes of fainting that result in only a minute or two of unconsciousness are generally not cause for concern, your wife was correct in calling 911 as some "fainting spells" can signal a serious problem, such as a potentially fatal irregularity of heart rhythm, a stroke, or a heart attack. In fact, about 25% of adults who faint unexpectedly will eventually be diagnosed with a heart condition.

Fainting preceded by palpitations, chest pain, shortness of breath, mental confusion, blurred or double vision, trouble talking, or loss of function of an arm or leg always requires immediate medical attention to determine the underlying cause. In fact, all unexplained episodes of fainting require medical evaluation.

In approximately 30% of people who faint, a cause is never determined. Some other common causes for fainting include straining during urination, a bowel movement, vigorous coughing, dehydration, blood loss, standing too long, and hot, crowded surroundings.

Although most faints are not a cause for excessive concern, they can be a warning of serious disease, especially if they recur. A careful physical exam and detailed medical history, and possibly heart testing will help your doctor determine the likely cause of the event and check to be sure there are no underlying medical problems.