A tilt table test is a diagnostic tool used to investigate the cause of unexplained fainting, near-fainting, or chronic dizziness (syncope or presyncope). This procedure helps physicians determine if a person’s symptoms are related to how the body regulates blood pressure and heart rate when upright. By simulating the stress of standing in a controlled environment, the test allows for continuous monitoring of the body’s cardiovascular response.
Defining the Tilt Table Test and Its Purpose
The tilt table test measures the body’s response to positional change. When a person stands up, gravity pulls blood toward the lower extremities, triggering the autonomic nervous system to compensate by increasing heart rate and constricting blood vessels to maintain blood flow to the brain. The test identifies conditions where this automatic compensatory mechanism fails or overreacts, leading to symptoms.
The test is indicated for patients experiencing recurrent unexplained syncope, especially when initial evaluations have failed to provide a diagnosis. It specifically looks for forms of orthostatic intolerance.
A common condition diagnosed is vasovagal syncope, an exaggerated reflex causing a temporary drop in blood pressure and heart rate. The test is also useful in diagnosing other forms of autonomic nervous system dysfunction, or dysautonomia, including Postural Orthostatic Tachycardia Syndrome (POTS) and orthostatic hypotension.
Preparing for and Undergoing the Procedure
Preparation for the test typically involves specific instructions concerning food and medication intake. Patients are usually asked to fast for at least six to eight hours before the procedure. Physicians may also instruct the patient to temporarily stop certain medications, particularly those affecting blood pressure or heart rate.
The procedure begins with the patient lying flat on a specialized table that has a footrest and safety straps across the chest and legs. Monitoring devices are attached, including electrodes for a continuous electrocardiogram (ECG) to track heart rhythm and a cuff to measure blood pressure. An intravenous (IV) line may be placed in the arm, allowing for rapid administration of medications or fluids if necessary.
After a baseline period of lying flat, the table is slowly tilted to an upright angle, simulating a standing position. The patient remains in this upright tilt phase for a set duration, often 20 to 45 minutes, while the medical team closely monitors heart rate and blood pressure responses. If the patient does not experience symptoms or a significant change in vital signs during this initial phase, a medication such as sublingual nitroglycerin or an IV infusion of isoproterenol may be administered. These medications are used to chemically stress the cardiovascular system and increase the test’s sensitivity, and the patient is then tilted upright again for an additional 15 to 20 minutes.
Understanding the Test Results
The interpretation of the tilt table test relies on correlating the patient’s symptoms with simultaneous changes in heart rate and blood pressure. A “positive” result occurs when the test successfully reproduces the patient’s typical symptoms, such as fainting or dizziness, coupled with a significant drop in blood pressure or an abnormal change in heart rate. Conversely, a “negative” result means the patient remained symptom-free with stable vital signs.
Positive responses are generally classified into types based on the primary physiological change observed at the time of syncope. A cardioinhibitory response involves a significant drop in heart rate, sometimes causing a pause in the heartbeat, while a vasodepressor response is characterized by a dramatic fall in blood pressure. A mixed response shows a combination of both a heart rate and blood pressure drop.
A positive result showing an excessive increase in heart rate without a major drop in blood pressure may confirm a diagnosis of Postural Orthostatic Tachycardia Syndrome (POTS). Identifying the specific type of abnormal response is crucial because it directly informs the subsequent treatment plan. The results help the physician guide treatment, which may include lifestyle modifications, such as increasing salt and fluid intake, or the prescription of specific medications to manage blood pressure or heart rate.