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EP Procedures - Tilt Table Study

Tilt Table Study

        The previous section describes the most common type of electrophysiology study. Another type of study that is used to test for a specific problem is called the tilt table study. While this test is performed using a completely different technique than a standard EP study, it still falls under the area covered by the electrophysiologist. The tilt table study is used to test patients that may have neurocardiogenic syncope. This is a complex condition that occurs when patient's have an abnormal response to stimulation of the nervous system. Whenever your body receives any form of stimulation, the brain tells your heart to respond with an increase in heart rate and blood pressure. When this happens, the body reacts to the elevated heart rate and blood pressure with an opposing response that prevents the pulse and BP from going to high. In patients with neurocardiogenic syncope, this opposing response may be so strong that the stimulation is completely suppressed. Instead of increasing, the heart rate and/or the blood pressure decrease, sometimes going so low that the patient passes out.

          This test is performed by placing the patient on a flat table and hooking them up to heart rate and blood pressure monitors. Once everything is ready, the table is raised up to a 70 degree angle. This elevation causes blood to flow down to the lower portion of the body. As this happens, the brain senses that there is less blood in the center regions of the body. To compensate for the decreased volume of blood, the brain sends a signal to the heart to increase the number of heart beats per minute. The blood vessels will also constrict a little causing an increase in blood pressure. The table is held at this angle for around 20 minutes. During this time, the patient is monitored closely for indications of a strong opposing reaction to the bodies stimulation. If, after 20 minutes, the patient's heart rate and blood pressure have not changed, a medicine called isuprel may be given. Isuprel is a medication that is used to increase stimulation of the heart. After the isuprel is given, the patient is monitored for another 10 to 20 minutes. If nothing has happened by that point, the results of the test are considered negative and the test is stopped. A tilt table study can be considered positive with just a decrease in heart rate, a decrease in blood pressure or both. It is possible that a patient who has a positive tilt table study may pass out completely. For this reason, all patients who have a tilt table study will be securely strapped on to the exam table before the test is started.

          The images below were taken from a tilt table study that turned out to be very positive. This series of rhythm strips should demonstrate why it is important to pay close attention during this type of procedure. Many times, nothing will happen. When something does happen, it can be sudden and extreme. In this procedure, there were immediate indications that the study would be positive. It was less than four minutes before a near code situation occurred. Fortunately, recovery was as quick as the onset of symptoms.

Prior to the start of the tilt table study, a rhythm strip was documented.
Normal sinus rhythm is seen with the blood pressure measuring at 143/74.

Another strip is documented when the table is raised.
Note that the heart rate does not change though the systolic blood pressure does drop to 102.
A little over 3 minutes later and there is some slowing in the heart rate. The systolic blood pressure is now 98.
17 seconds after the previous image a profound drop in heart rate is noted. The 2nd, 3rd and 5th beats are junctional.
Continued from the previous strip. The sinus node has shut down. The rhythm is now entirely junctional.
At this point, a blood pressure could not be detected. There is some indication of sinus node activity.
The table is immediately lowered to the supine position.
Continued from previous strip. Note that sinus activity is intermittent.
Sinus activity has returned.
Three minutes after the drop in heart rate and blood pressure, the patient is in
sinus rhythm with a systolic pressure in the low 90's.
The patient was kept supine for several minutes. Heart rate and blood pressure were maintained and the test was terminated. The patient was allowed to stand and was monitored for several minutes after getting up.

          The tilt table study is designed to determine if the patient has a condition referred to as neuro-cardiogenic syncope. NCS is caused by an imbalance in the x nervous system. The imbalance is specific to the interaction between the sympathetic and parasympathetic nervous systems. When a patient is stimulated, in this case by a change in the position of the body, the sympathetic nerve system triggers an increase in heart rate and/or blood pressure. When ever the sympathetic nervous system comes into play, there is a parasympathetic response. This response is designed to prevent the heart rate from jumping too high as it does in patients with Inappropriate Sinus Tachycardia.

         In patients with NCS, the parasympathetic response is overwhelming. Instead of experiencing an appropriate increase in heart rate and blood pressure, the exact opposite occurs. The heart rate and the blood pressure may drop precipitously as it did in this patient.  While many Tilt Table Studies have no dramatic events, you should always be ready for an event like this to happen.


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