Vigilance Is Needed for More Serious Causes of Syncope
FROM THE ANNUAL MEETING OF THE AMERICAN COLLEGE OF EMERGENCY PHYSICIANS
Patients with long QT syndrome have a genetic defect causing lengthening of ventricular repolarization, according to Dr. Lewis. Syncope occurs during episodes of polymorphic ventricular tachycardia that appear to be precipitated by stress and usually resolve spontaneously.
The ECG shows a prolonged rate-corrected QT interval (QTc). Patients’ lifetime risk of syncope and sudden death rises with this interval, from 5% at an interval of less than 440 milliseconds to 50% at an interval of greater than 500 milliseconds.
“First of all, when somebody comes in with a prolonged QTc, you want to rule out treatable causes,” he said. These include myocardial ischemia; electrolyte perturbations; certain psychiatric, cardiovascular, and antiemetic medications; and methadone.
Arrhythmogenic Right Ventricular Dysplasia
Another inherited condition, arrhythmogenic right ventricular dysplasia (ARVD) is the second most common cause of structural heart disease–related sudden cardiac death in adolescents.
The findings on an ECG can be subtle, according to Dr. Lewis. Patients have inverted T waves in the precordium, a QRS width greater than 110 milliseconds, and if ventricular tachycardia is captured, a left bundle branch block morphology. “But the tip-off is these little waves called epsilon waves,” which occur at the end of QRS complexes and look much like P waves.
ARVD is “very tough to diagnose [from the ECG]. I am sure people miss this stuff all the time,” he commented.
“From your standpoint, if a kid comes in and had a sudden syncopal event, there was no prodrome, this kid at least needs an echo,” he said. “So you might not pick it up on ECG, but you probably will pick it up on echo and see that there is something obviously wrong with his right ventricle.”
Pulmonary Embolism
Syncope in patients with pulmonary embolism occurs when right heart failure begins to cause left heart failure. They develop systemic hypotension and hypoperfusion, and lose consciousness, Dr. Lewis said.
“If someone comes in in the setting of a syncopal event and they have a pulmonary embolism, you should be concerned about it,” he noted. “There is very high association between syncope and having proximal pulmonary embolisms.”
Hence, such patients should be especially closely monitored because their condition can deteriorate rapidly, he cautioned.
Aortic Dissection
Approximately 13% of patients with aortic dissection experience syncope (Am. J. Med. 2002;113:468-71).
“It can indicate dangerous complications,” Dr. Lewis said. “If a patient ‘syncopizes’ from a dissection, you have to be concerned about two things: One, you want to make sure that they don’t have tamponade and two, that they don’t have a stroke.”
The former occurs if the dissection extends proximally and reaches the pericardium, decreasing stroke volume; the latter occurs when the dissection causes cerebral hypoperfusion.
“Syncope is also a frequent presenting sign in patients who have painless aortic dissections,” he said (Mayo Clin. Proc. 2004;79:1252-7). “Probably the scariest thing you could ever think of is having a patient with a painless aortic dissection. … It is going to be kind of tough to pick up on these patients, but always keep that in your differential when someone comes in with a syncopal event.”
Dr. Lewis had no significant financial relationships to disclose.
