The tilt table test, also known as the head-up tilt test, is a diagnostic tool used to investigate the cause of fainting, or syncope, and unexplained dizziness. This procedure monitors the body’s cardiovascular response to a rapid change in posture, mimicking the stress of standing up from a lying position. By observing the changes in heart rate and blood pressure, healthcare providers can determine if the body’s autonomic nervous system is regulating blood flow to the brain correctly.
Purpose of the Tilt Table Test
The tilt table test is generally recommended when standard tests have not identified the cause of recurrent, unexplained syncope or near-fainting episodes. It helps determine if symptoms are related to abnormal regulation of blood pressure or heart rate that occurs with upright posture.
This procedure is particularly useful for diagnosing neurally mediated syncope, often called vasovagal syncope or the common faint, which involves a sudden drop in heart rate, blood pressure, or both. It also aids in identifying orthostatic hypotension, a condition where blood pressure falls significantly upon standing, and Postural Orthostatic Tachycardia Syndrome (POTS), characterized by an abnormal increase in heart rate when moving to an upright position. The test helps distinguish these physiological causes from other conditions, such as psychogenic pseudo-syncope.
Preparing for the Procedure
Patients must follow specific preparatory instructions. A common requirement is fasting for a period, typically between four and twelve hours before the test, to prevent aspiration if a fainting episode occurs. Patients should wear comfortable, two-piece clothing for ease of attaching monitoring equipment.
Patients are often instructed to discontinue certain medications (such as beta-blockers or calcium channel blockers) that affect heart rate or blood pressure before the test. This temporary cessation ensures the body’s natural cardiovascular response is not masked by the drugs. Patients will also be asked to sign a consent form, acknowledging they understand the procedure and its potential for briefly reproducing their symptoms.
The Tilt Table Procedure
The tilt table test is performed in a quiet room with continuous supervision by medical personnel. The patient begins by lying flat on a motorized table that has a footrest and safety straps placed across the chest and legs to prevent injury if the patient faints.
Monitoring equipment is attached, including ECG leads on the chest to track heart rhythm and a continuous blood pressure cuff on an arm or finger. After lying flat for 10 to 15 minutes to collect baseline data, the table is rapidly tilted upward. The angle of the tilt is usually between 60 and 80 degrees, simulating the act of standing up.
The patient remains in this head-up position for 20 to 45 minutes while heart rate and blood pressure are continuously recorded. If the initial passive tilt does not provoke symptoms, a second phase may be initiated using pharmacological agents. Medications such as sublingual nitroglycerin or intravenous isoproterenol are administered to increase the sensitivity of the test.
After the medication is given, the table is tilted upright again, and the patient is monitored for up to an additional 15 minutes. The test is immediately stopped and the table is returned to a flat position if the patient faints or if a significant drop in blood pressure or heart rate is observed. This ensures a quick resolution of symptoms.
Interpreting Test Outcomes
A result is considered “Negative” if the patient remains symptom-free with no significant drop in blood pressure or heart rate. A negative test suggests that the fainting episodes are likely not related to a simple reflex syncope.
A “Positive” result occurs if the test successfully reproduces the patient’s typical symptoms, such as lightheadedness or syncope, accompanied by specific changes in heart rate and blood pressure. Positive vasovagal responses are categorized based on the predominant hemodynamic change observed during the event.
The cardioinhibitory response involves a significant drop in heart rate (sometimes pausing the heartbeat), while the vasodepressor response is characterized by a significant drop in blood pressure with little change in heart rate. Many patients exhibit a mixed response, involving a decrease in both heart rate and blood pressure at the time of symptoms. Identifying the specific pattern helps guide appropriate follow-up treatment, which may include lifestyle adjustments, increased fluid intake, medication therapy, or evaluation for a pacemaker.