The vasovagal syncope is one of the more common and potentially serious causes of fainting. The condition develops when an inappropriate reflex in the nervous system leads to opening (dilation) of the blood vessels along with slowing of the heart rate (bradycardia).
With slowing of the heart rate and dilation of the blood vessels in the legs, the blood pressure is lowered. Because blood is directed to the legs, less blood (and therefore less oxygen) goes to the brain. Fainting (syncope) is the outcome, which can be troublesome as well as dangerous.
Pacemakers can be used in persons with serious slowing of the heart rate (bradycardia) to maintain a normal heart rate.
The first randomized controlled study of pacemakers in the prevention of vasovagal syncope has now been published in the current issue of the Journal of the American College of Cardiology (1999;33:16-20). This eagerly anticipated trial was performed by multiple medical centers throughout the United States and Canada in a collaborative effort called The North American Vasovagal Pacemaker Study.
The study, which was originally designed to evaluate 284 patients, was terminated early (the study had met prearranged termination criteria) because of the vastly significant success of pacemaker trials in the first 54 patients!
All of the 54 patients had previously suffered more than 6 episodes of fainting and had abnormal findings on tilt-table testing (see the Syncope Forum for more information).
Half of the patients (27) received pacemakers and half (27) did not.
The type of pacemaker used in the study sequentially stimulates the
upper and lower chambers of the heart (dual chamber pacing).
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The outcome measured in the study was the first recurrence of fainting. Recurrent fainting occurred in 19 of 27 no-pacemaker patients and 6 of 27 pacemaker patients. 4 of the no-pacemaker patients with recurrent fainting had been injured and bruised as a result. It was noted that mild lightheadedness episodes (presyncope) persisted in the study patients, whether or not they had received pacemakers.
The North American Vasovagal Pacemaker Study shows clearly that patients with severe symptoms from vasovagal syncope can significantly reduce (85% reduction in the study) their chances for recurrent episodes by receiving a heart pacemaker. The authors went so far as to recommend consideration of pacemaker placement for those patients with frequent vasovagal syncope who also have slowing of the heart rate during tilt-table testing.
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