Syncope Dx Moving to Implantable Recorders
Prolonged ECG monitoring to find disease-related ECG abnormalities is the biggest attraction of ILRs. The alternatives, Holter monitors and external loop recorders, are not practical for monitoring that might take months or years, and an in-hospital electrophysiology study carries no guarantee that an induced arrhythmia replicates the cause of spontaneous syncope.
According to the ESC guidelines, although ILRs have a “high initial cost … if symptom-ECG correlation can be achieved in a substantial number of patients … the implanted device may be more cost effective than a strategy using conventional investigation.”
The guidelines cite two class I indications (which means there is evidence for or general agreement that the procedure is effective and useful) for ILRs in assessing syncope: in the early phase of evaluating patients with recurrent syncope of uncertain origin who lack high-risk criteria but have a high likelihood of a recurrent episode during the ILR's battery life, and in high-risk patients whose initial evaluation did not identify a cause of syncope. An additional, more equivocal use of ILRs is to assess the role of bradycardia in patients with known or suspected reflex syncope prior to starting cardiac pacing.
“Tilt table testing is becoming less frequent, and electrophysiology studies should be exceptional,” Dr. Andrew D. Krahn said at the American Heart Associations scientific sessions last November in Orlando. The first and best tool for evaluating the likely cause of syncope is a detailed patient history, he added.
In addition to history, assessment of unexplained syncope is largely guided by left ventricular function, Dr. Krahn said. In patients with a left ventricular ejection fraction of less than 30%, the prime option is to forgo further testing and consider placing an implantable cardioverter defibrillator. In patients with better left ventricular function, ILRs serve as the ultimate arbiter for hard-to-assess patients.
In patients with an ejection fraction of more than 45%, tilt table testing may be appropriate if a vasovagal cause is suspected, said Dr. Krahn, an electrophysiologist in the arrhythmia service at the London (Ont.) Health Sciences Centre, and a member of the ESC syncope guidelines task force.
If an arrhythmia cause is the primary suspect, external monitoring is a potential first choice, and external monitoring might also follow a failed tilt table test. But if external monitoring fails to make the diagnosis, then an ILR is the next step, he said.
Dr. Vardas has been a speaker for Medtronic and St. Jude, companies that market ILRs. Dr. Sutton has received research grants from, and has been a consultant to, Medtronic. Dr. Leclercq has been a consultant to Medtronic and St. Jude. Dr. Strickberger has been a consultant to St. Jude. Dr. Krahn has received research grants from, and has been a consultant to, Transoma, a third company that had marketed an ILR. (Transoma went out of business late last year.)
The new European guidelines 'attempt to bring the ILR into the forefront of investigation of syncope.'
Source DR. SUTTON
