Tilt Table Testing
Some people are prone to fainting. They may have a history of fainting going on their whole lives but rarely have any serious consequences from it. These fainting spells often occur when they are upset or nervous about something. These swoons also frequently occur when they undergo medical procedures, have a blood test drawn, or simply at the site of blood and needles. These nervous faints have been portrayed to great dramatic effect in the old movies of the 1930s and 1940s. Such people will often appear to have perfectly normal hearts by most tests. However, their otherwise normal heart is prone to an abnormal neural reflex.
When somebody gets excited or nervous, it is normal for their body to produce adrenaline which then makes the heart beat forcefully. In people prone to nervous fainting, this forceful heart beat is sensed by an abnormal nerve ending in their heart. This nerve then elicits a reflex whereby the brain suddenly makes the heart beat very slowly. At the same time, all the blood vessels in the body dilate. As a result of the slow heart beat and the dilated blood vessels, the blood pressure falls dramatically. Their brain no longer receives enough blood flow and the person loses consciousness. As the person falls down, more blood from the body returns to the heart, thus interrupting the reflex. Consciousness is soon regained.
Some people will get warning symptoms such as feeling warm, sweaty and nauseous before these faints. If they recognize these symptoms, they can often abort the fainting by sitting or lying down.
So what does all this have to do with tilt table tests?
Physiologists used to do experiments that involved putting a person on a table and gradually tilting it upright to study the effect of body position on their physiology. They noted that some people fainted during this procedure. Further study revealed that it was the aforementioned reflex that was responsible.
The tilt table test is now used to determine if this reflex is indeed the cause for a person fainting if there are no other evident causes.
How it works
Preparation for the test requires not eating for a minimum of six hours.
The patient then lays down on a tilt table which includes a foot board. The patient is secured to the table so they won't fall off of it if they faint while tilted upright. The table is then tilted to an angle of 80 degrees for 45 minutes. Pulse, blood pressure and heart rhythm are closely monitored. Sometimes, an intravenous medicine is infused as well. A nurse and physician are both in attendance.
If the patient faints, the table is rapidly returned to the horizontal position and with this, the patient regains consciousness. The patient can return to normal activities after the test unless advised otherwise by their physician.
If the test is positive (i.e., the patient fainted or came close to fainting), the patient is diagnosed as having "vasovagal" or "neurocardiogenic" fainting. Specific medications are available to treat this condition.
Some patients who suffer from the chronic fatigue syndrome also have positive tilt table tests. The same medications used to treat vasovagal fainting may also help these chronic fatigue patients to feel better.
Preparing for the test
Preparation for the test requires not eating for a minimum of six hours prior to your appointment.
Abnormal responses
There are five abnormal response patterns to head-upright tilt table testing:
- The classic neurocardiogenic response is characterized by a sudden drop in blood pressure followed by a decrease in heart rate. Patients have few medical complaints between syncopal episodes.
- The dysautonomic response is a gradual decrease in blood pressure to a hypotensive level, leading to loss of consciousness. Often, these patients have other signs of autonomic dysfunction, such as abnormal sweating, constipation and thermal intolerance.
- The postural orthostatic tachycardia syndrome was recently identified. This seems to be a mild form of autonomic dysfunction in which an excessive increase in heart rate cannot compensate for low peripheral vascular resistance. Patients have an increase in heart rate of 30 beats per minute or a maximum heart rate of 120 beats per minute in the first 10 minutes of upright posture. They often report near syncope, palpitations and extreme fatigue, which may be mistakenly attributed to chronic fatigue syndrome.
- Cerebral syncope has been reported by several medical centers as a relatively rare finding in patients undergoing concomitant tilt table testing and transcranial Doppler ultrasonography, which measures the degree of cerebral vasoconstriction or vasodilation. Patients pass out owing to cerebral vasoconstriction alone with no hypotension or bradycardia.
- The psychogenic or psychosomatic response occurs with no observable change in heart rate or blood pressure or findings on transcranial Doppler ultrasonography or electroencephalography. Patients are often found to have psychiatric disorders, ranging from conversion reactions to major depression.
For more information on tilt table testing, please call the Cardiopulmonary Department at 270.251.4120.