Syncope, Part 3 - How syncope is treated
In this final article in our series on syncope, we will consider, in general terms, the treatments used for the major varieties of syncope: cardiac syncope and vasovagal syncope.
The treatment of cardiac syncope
As we have noted, two general types of heart problems can produce syncope obstructive lesions, and heart rhythm disturbances.
Obstructive lesions (such as valvular heart disease, obstructed blood vessels, or cardiac tumors) can intermittently block the flow of blood through the heart, causing loss of consciousness. The treatment of obstructive cardiac lesions is surgical if there is a mechanical obstruction to blood flow, that obstruction must be physically removed. The extent, chances of success, and risks of such surgery depend on the nature of the obstruction. But when an obstruction is impeding blood flow to the extent that syncope occurs, as a general rule surgery is imperative, whatever the risks involved.
Heart rhythm disturbances that produce syncope fall into two broad categories: bradycardia and tachycardia.
Bradycardia, cardiac arrhythmias that produce a slow heart rate, can cause syncope when the heart rate becomes so slow that insufficient blood is pumped to the brain, and consciousness can no longer be maintained. Fortunately, implanting a cardiac pacemaker can easily treat this problem.
Tachycardias are heart rhythm disturbances in which too many electrical impulses are produced by the heart, thus causing the heart to beat too rapidly. While there are many kinds of tachycardia, only two produce syncope with any regularity ventricular tachycardia (VT) and ventricular fibrillation (VF).
One treatment used for both VT and VF is antiarrhythmic drugs. These drugs, as a class, tend to be quite toxic, and their effectiveness in completely eliminating VT and VF is relatively poor. Therefore, antiarrhythmic drugs should be used only rarely as the primary treatment for patients whose VT or VF has produced syncope.
A second form of treatment is ablation. Ablation consists of carefully mapping the electrical system of the heart (either in the electrophysiology laboratory or in the operating room), locating the part of the electrical system that is causing the arrhythmia, and ablating the offending area (by freezing it, burning it, or surgically excising it). Unfortunately, most forms of VT are very difficult to localize to a specific culprit area. This means that ablation is only infrequently an option for VT (and never for VF).
The third and most effective treatment for both VT and VF is the insertion of an implantable defibrillator. In nearly 20 years of clinical use, the implantable defibrillator has proven itself to be extraordinarily effective in automatically stopping lethal tachycardias, and preventing sudden death. Because of the remarkable effectiveness of the implantable defibrillator (and the disturbing ineffectiveness of other methods of therapy), this device is, by far, the best choice for patients who have had VT or VF that has produced syncope.
The treatment of vasovagal syncope
As we noted in Part 2, vasovagal syncope is by far the most common cause of loss of consciousness.
There are three general modes of therapy for vasovagal syncope: education, drugs, and pacemakers. Of these, education is by far the most effective.
Education: What do you need to know? Individuals prone to this kind of syncope need to know five facts:
- Vasovagal syncope is produced by a reflex that causes sudden dilation of the blood vessels in the legs, causing the blood to pool there.
- Any condition that causes a bit of dehydration (i.e., a reduction in the overall blood volume) will make you more prone to have a syncopal episode.
- Most people will have a brief prodrome (i.e., a set of characteristic symptoms) that precedes the loss of consciousness. That is, there is usually a warning.
- If you lie down and elevate your legs when you experience the prodrome, you can prevent the syncopal episode.
- Patients will often have occasional periods of days or weeks in which they are particularly prone to vasovagal episodes.
How can these five facts be put to work? The best way to prevent vasovagal syncope is to avoid the situations that produce the syncope. If you understand these five facts, the following guidelines become immediately apparent.
First, avoid dehydration. Dehydration (and therefore syncope) most commonly occurs after exercise, after any kind of illness (such as a cold), and early in the morning after an overnight fast. Coffee, tea, and diuretic drugs can also produce dehydration. During these times, you should take pains to rehydrate yourself. Drink plenty of fluids, and avoid prolonged standing while you are dehydrated.
Pay close attention to any prodromal symptoms you may have. Syncope is usually preceded by at least a few seconds (and often several minutes) of symptoms that may consist of visual disturbances, buzzing in the ears, lightheadedness, sweating, nausea, or other symptoms. Individuals who have had syncopal episodes usually have an excellent idea of what prodromal symptoms to expect. It is important to recognize these symptoms, because if you do, syncope can be averted virtually 100% of the time by lying down and elevating your legs. If instead, you choose to fight the episode, youre likely to pass out in the frozen foods section, and the store manager will insist (for well-founded legal reasons) on shipping you to the E.R. in an ambulance where youll be subjected to a battery of unnecessary tests and probably an overnight stay in the hospital. Another advantage of aborting the actual syncope is that when you do, you also avoid the prolonged period of feeling sick (wasted, washed out, nauseated, and dizzy) that often follows a vasovagal episode.
People who are prone to vasovagal syncope often have periods of days or weeks in which syncope is particularly likely to occur. These sensitive periods often seem to occur for no identifiable reason, but they can follow a viral illness, or they can be related to the menstrual cycle, to allowing yourself to become fatigued or run down, or to an ongoing gastrointestinal, urinary, or gynecological problem. (Sometimes it is even worthwhile to run a GI series on patients with an unexplained flurry of syncopal episodes. On more than one occasion, DrRich has found occult peptic ulcer disease in such patients). If you have had one or two recent syncopal episodes, it pays to be particularly vigilant for prodromal symptoms that might herald another episode. It also pays during these times to make special efforts to remain well hydrated.
Drug therapy: In some patients, vasovagal syncope occurs with disturbing frequency even when all appropriate precautions are taken. For these patients, drug therapy is often attempted.
Several types of drugs have been used in patients with vasovagal syncope. These include beta blockers, serotonin uptake inhibitors (i.e., drugs in the Prozac category), florinef (a drug that prevents dehydration by retaining sodium), and midodrine (a drug that tends to limit the dilation of blood vessels). These drugs substantially reduce the episodes of syncope only 60 - 70% of the time, and finding the "right" drug treatment is a matter of trial and error. Patience is required on the part of both the doctor and patient.
What about pacemakers for vasovagal syncope? Several years ago there was much enthusiasm for using pacemakers to treat vasovagal syncope. The enthusiasm dropped off rapidly, however, after it was finally noted patients with vasovagal syncope who received pacemakers continued to pass out - they just did it with better heart rates. As it turns out, in the large majority of patients with this vasovagal syncope, it is the pooling of blood in the legs and not the slow heart rate that produces syncope.
In the last two or three years, reports from various investigators have again raised the enthusiasm for using pacemakers in highly selected patients with vasovagal syncope. While it still seems clear that the majority of patients do not respond favorably to pacemakers, there is, equally clearly, a small subset that do respond favorably.
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