Mechanism of Syncope in Patients With Heart Disease and Negative Electrophysiologic Test

Abstract

on behalf of the International Study on Syncope of Uncertain Etiology (ISSUE) Investigators* Background-In patients with syncope and structural heart disease, syncope is suspected to be attributable to a primary cardiac arrhythmia, but little is known of its mechanism when electrophysiologic study is unremarkable. Methods and Results-We applied an implantable loop recorder in 35 patients with overt heart disease at risk of ventricular arrhythmia, because these were patients with previous myocardial infarction or cardiomyopathy with depressed ejection fraction or nonsustained ventricular tachycardia in whom an electrophysiologic study was unremarkable. During a follow-up of 3 to 15 months, syncope recurred in 6 patients (17%) after a mean of 6Ϯ5 months; in 3 patients, the mechanism of syncope was bradycardia with long pauses (sudden-onset AV block in 2 cases and sinus arrest in 1 case); in 1 patient, there was stable sinus tachycardia; and in 2 patients, who had chronic atrial fibrillation, there was an increase in ventricular rate. A total of 23 episodes of presyncope were documented in 8 patients (23%): no rhythm variation or mild tachycardia in 12 cases, paroxysmal atrial fibrillation or atrial tachycardia in 10 cases, and sustained ventricular tachycardia in 1 case. No patient died during the study period nor suffered from injury attributable to syncopal relapse. Conclusions-The patients with unexplained syncope, structural heart disease, and negative electrophysiologic study had a favorable medium-term outcome with no case of death and a low recurrence rate of syncope without related injury.

Implantable Loop Recorder Allows an Etiologic Diagnosis in One-Third of Patients

“…Pezawas et al reported an even greater prevalence of recurrent symptoms (91%) but only 39.4% presented an arrhythmia during the event (mostly bradycardia), without episodes of ventricular tachycardia. 19 We obtained a final diagnosis in 28.2% of the present group, mainly secondary to bradycardia-related events, similar to that reported by ISSUE2 and Entem et al 7,13 One-third of the BBB cohort had a final diagnosis, with a greater rate in those patients without previous EPS, likely because some of the high-risk patients would have been previously diagnosed if the test had been performed. In 2 previous series of patients with syncope, BBB, and negative EPS, the rates of final diagnosis were 36.5% 6 and 45%, 8 mostly brady-…”

“…Groups were defined according to similar previous studies. [6][7][8] Follow-up data regarding the interpretation of clinical symptoms, recorded electrograms, final diagnosis, and treatment Alzheimer's disease, n=10; non-specific or unknown, n=13). One-third of the patients had SHD (for study purposes, those with BBB or conduction disease were included in the group of BBB for analysis): 132 patients had ischemic heart disease, 24 had dilated cardiomiopathy, 28 had hypertrophic cardiomiopathy, 28 had valvular disease, 9 had congenital disease and 9 had other diagnosis.…”

Differences in the yield of the implantable loop recorder between secondary and tertiary centers

“…Structural heart disease and bundle branch block were defined according to the definitions of previously published studies [8,9].…”

The implantable loop recorder: a critical review

“…90% of recurrent events showed prolonged asystolic pauses mainly attributable to paroxysmal AV block ( 2 / 3 of patients). In the last subset of 35 patients with mild structural heart disease (mean left ventricular ejection fraction 47 ± 17%) and negative EPS [19], syncope recurred in only 17% and presyncope in 37% over 3-15 months of follow-up, yielding a diagnosis in 40% of patients. Most recurrences were due to bradycardia with long pauses while sustained VT remain unlikely (1 case), stressing that patients with mild structural heart disease and negative EPS show favorable mid-term outcome.…”

“…Nierop et al [28] reported resolution of symptoms in 17% after ILR implantation. In the different substudies of the ISSUE trial, patients with a mean of ≥2 syncopal episodes during the last 2 years prior to randomisation experienced a decrease in syncope recurrence by a factor of 2 [18], 3 [17] and 5 [19], respectively,in the year following ILR implantation. Moreover, 2 / 3 of ILR-implanted patients included in the ISSUE 2 trial [26], with a median of 4 syncopal events during the last 2 years prior to implantation, did not experience recurrence over a median follow-up of 9 months, highlighting the potential placebo effect of ILR in patients suffering from syncope.…”