SYNCOPE
A discussion with Dr. Andreas K. Pavlides, M.D.
Syncope is the transient loss of consciousness with the inability to maintain postural tone that resolves spontaneously. Because syncope can have numerous causes, both cardiac and non-cardiac, it poses a diagnostic challenge. Cardiologists need to evaluate possible cardiac causes in a syncopal workup, the initial part of which is the patient's history.
"We like to get a detailed account of the event from the patients or from possible witnesses," said Dr. Andreas K. Pavlides of the clinical cardiology staff at Associated Cardiovascular Consultants (ACC). "It's important to determine if there were any preceding symptoms prior to the event."
Patient's history
In general, patients experience only a few seconds of preceding symptoms in cases of syncope resulting from true cardiac causes, while preceding symptoms in syncope resulting from other causes, such as a vasodepressor event, may last a few minutes, Dr. Pavlides explained.
"We also like to know if the patient was performing any activities prior to the event."
Exertional syncope suggests cardiac outflow obstruction, which can be seen with aortic stenosis. Syncope with exertion can also be seen with Hypertrophic Obstructive Cardiomyopathy.
"If the preceding symptoms are chest pain or shortness of breath, the possible cause could be myocardial ischemia or pulmonary embolism," Dr. Pavlides said. "Palpitations suggest a possible arrhythmia. If the patient experienced an unpleasant physical or emotional event prior to the syncopal episode, this usually represents a vasodepressor event or 'fainting spell'."
The workup also includes a detailed history of the patient's medications, particularly those that can cause hypotension, such as nitrates, diuretics or anti-hypertensives and those that can cause bradyrhythmias, such as beta blockers or digoxin.
Physical exam
During the patient's physical exam, the cardiologist checks for orthostatic hypotension. Although happening on rare occasions, syncope may occur during a transient ischemic attack so the carotids are listened to for bruits. If no bruits are evident, the exam may also include testing the carotid arteries for hypersensitivity in a monitored setting. Dr. Pavlides explained that this test involves gently pressing on the carotids one at a time while on an ECG and blood pressure monitoring to see if a significant pause or drop in blood pressure occurs.
The cardiologist also listens for irregular heart rhythm and for significant murmurs.
"Harsh systolic murmurs radiating to the neck could be consistent with aortic stenosis," Dr. Pavlides said. "A systolic murmur that gets louder with Valsalva (straining) and fainter with squatting could suggest HOCM (hypertrophic obstructive cardiomyopathy).
Diagnostic testing
Various diagnostic tests may be indicated for patients with syncope. These include ECG, Holter monitor, 2-D echocardiography and tilt-table testing.
"The ECG is basic, but it provides a lot of information such as past myocardial infarction, conduction abnormalities, premature beats or arrhythmias or left ventricular hypertrophy," Dr. Pavlides said.
For syncopal patients who have experienced occasional arrhythmias, a 24-hour Holter monitor may be ordered. "It monitors every heartbeat and records arrhythmias or conduction problems such as marked bradycardia and heart block. Patients are given a diary in which to record symptoms. We then try to correlate the symptoms to the arrhythmias."
2-D echo is used to evaluate left ventricular function and screen for significant valvular disease, pericardial effusion and pericardial masses, such as atrial myxomas.
In rare cases, Dr. Pavlides explained, syncope can result if a left atrial myxoma obstructs the mitral valve. This usually occurs when the patient leans or bends over, thus repositioning the tumor.
"In some cases, patients are referred to our electrophysiologists for further testing, including tilt-table testing, which looks for inappropriate heart rate or blood pressure decrease associated with symptoms in response to positional changes." Electrophysiologists may also use an implantable loop recorder that can look for arrhythmias over a longer period and, unlike hand-held event monitors, will work even if the patient loses consciousness.
"If a patient has recurrent syncope with a high index of suspicion of cardiac cause, we will order an electrophysiological study to attempt to induce arrhythmia or look for abnormal conductions."
Treatment
"In younger patients with no evidence of cardiac disease, syncope generally carries a favorable prognosis," Dr. Pavlides said. "In our older patients, treatment can be as simple as medication or may require an invasive procedure such as valve replacement or an implantable defibrillator."
Citing examples of the range of treatment, Dr. Pavlides said patients with significant bradycardia or carotid hypersensitivity may require a pacemaker while those with ventricular tachycardia (VT) may require a defibrillator, plus or minus anti-arrhythmic medications.
"For patients with severe aortic stenosis with syncope, the mortality after two to three years is 50 percent, so aortic valve replacement would be indicated. Patients with HOCM can initially be treated with beta blockers, but they may go on to require invasive procedures, including myomectomy."
In all cases of syncope in which a cardiac cause is suspected, the various tests should be used to pinpoint that cause, Dr. Pavlides concluded.
In summary
- Syncope can have various causes, presenting a diagnostic challenge.
- The type and duration of symptoms preceding syncope are important indicators of whether the event has a cardiac cause.
- Treatment may be as simple as medication or may require an invasive procedure.
A take home message about.... Syncope
- A detailed patient history is an important component of a syncopal workup.
- Various kinds of diagnostic testing may be necessary to find the cause of a syncopal event.
- If a cardiac cause for syncope is found, there are numerous treatment options.