Tilt Table Test
What is a Tilt Table Test?
A Tilt Table Test or TTT is widely used in making the diagnosis of Neurally Mediated Syncope or NMS.
What is NMS?
NMS is a condition that can occur in a wide range of people, many of whom do not have any other associated cardiovascular problems. These patients give a history of repeatedly having syncope (passing out spells) over the course of several years. Some of these spells may be preceded by a hot sensation or nausea but many come on without any warning. The patient may fall to the ground and recover consciousness quickly and without any further problems.
To understand this phenomenon, we must first examine how the nervous system of the body functions. During our daily activities, our heart rate (HR) and blood pressure (BP) constantly rise and fall to meet the needs of the body. The HR and BP are lower at rest, while the HR picks up and BP is elevated during emotional stress and exercise. The control of the HR and BP are under the domain of the sympathetic and parasympathetic nervous system. The former increases the HR and BP while the latter reduces them. To simplify this concept, let us imagine that the body is an automobile. Pressing the accelerator pedal would make the car work harder and go faster. In contrast, pressing the brake pedal would slow the car down. Thus, the sympathetic nervous system behaves like an accelerator for the body while the parasympathetic system functions like a braking system.
Normally, the sympathetic and parasympathetic nervous system work together in a very efficient and cooperative manner. From time to time, this system breaks down in people with NMS. The system causes the HR and BP to drop suddenly and severely during times of stress, causing the flow of blood to the brain to slow down. This causes a patient to pass out. Once the patient passes out, the system restores the HR and BP to a normal level, which restores blood flow to the brain and the person wakes up.
How is Tilt Test performed?
The patient is hooked to an EKG machine and a BP monitor. The HR and BP are constantly monitored during the procedure. An intravenous (IV) line is placed in the arm. Large patches are also applied to the patient's chest.
These patches are connected to an external pacemaker and turned on if the patient's HR slows down and does not pick right up (in the majority of cases the slow HR is transient and the external pacemaker is only a precautionary measure).
If nothing happens, the table is returned to the flat position and an intravenous infusion of isoproternol is started. This medicine increases the HR and BP. This effect is similar to that produced by our own natural adrenaline release. As you may have gathered, the test is now simulating what happens when the sympathetic nervous system is stimulated and the "accelerator" is pressed. The tilt table is then raised back up to 80 degrees and the IV medication continued.
A stop clock in the room is used to keep track of time. If an abnormal result is not seen, the table is lowered and then raised back up after increasing the dose of the IV medicine. In patients with NMS, the increase in HR and BP is usually sufficient to cause a break down of the parasympathetic nervous system. When this happens, the HR, BP or both drop suddenly and dramatically as the patient gets dizzy and passes out. Thus, TTT succeeds in simulating a real life situation and establishes the cause of recurrent black out spells. With the above changes, the test is considered positive. The IV medicine is immediately stopped and the patient returned to the flat or supine position. Within a few seconds, the patient regains consciousness and both the HR and BP return to normal. The patient is observed for 10 to 20 minutes and then disconnected from the equipment.
How to prepare for tilt test?
Check with your physician to see if any of your medications need to be held. You should not eat or drink after midnight to reduce the risk of nausea and vomiting during the test. Try and wear a blouse or shirt to expedite preparation for the test.
Is the test safe?
The test is fairly safe, although it can be dramatic for the patient if the test is positive and causes a black out spell. Not a pleasant circumstance, however, the patient needs to recognize that this denotes a positive response and opens the door to the addition of extremely effective medications that may dramatically reduce or totally eliminate the patient's recurrent black out spells. In rare cases, the test may produce persistent abnormal heart rhythm and patients with coronary artery disease may occasionally experience lingering chest discomfort.
What info is provided by the tilt test?
The tilt test helps to confirm the diagnosis of NMS. This is extremely important because there is effective treatment for the condition which can either totally eradicate or dramatically reduce the frequency and intensity of symptoms (dizziness and black out spells). Recent research studies have also shown a correlation between chronic fatigue syndrome (CFS) and NMS. Treatment aimed at NMS has been shown to be beneficial in many patients with CFS (if they have a positive tilt test).
Heart Rhythm Specialists of South Florida gives special thanks to the Heartsite, whose Web site provided the research for the educational material provided above.