Outcomes of Primary vs. Delayed Strategy of Implanting a Cardiac Monitor for Unexplained Syncope

Abstract

Objective: Implantable cardiac monitors (ILR) have an important role in diagnosing unexplained syncope. However, outcomes of primary vs. delayed ILR implantation after initial syncope evaluation have not been explored. Methods: A total of 1705 patients with unexplained syncope were prospectively enrolled in the SYSTEMA (Syncope Study of Unselected Population in Malmö) cohort. Patients who underwent cardiovascular autonomic testing (CAT) and ILR were grouped into those referred to CAT after ILR implantation (primary ILR) and those in whom ILR was indicated after CAT (post-CAT ILR). Results: One-hundred-and-fifteen patients (6.7%) received ILRs. ILR recipients were older (58 vs. 52 years; p = 0.002), had more syncope recurrences (6 vs. 4; p < 0.001), more traumatic falls (72% vs. 53%; p < 0.001), and less prodrome (40% vs. 55%; p = 0.005) than patients without ILRs. During follow-up ≥16 months after ILR, 67 (58%) had normal sinus rhythm, 10 (8.7%) had sinus arrest, 10 (8.7%) AV-block, 13 (11.3%) atrial fibrillation, 9 (7.8%) supraventricular tachycardia, 4 (3.5%) sinus tachycardia and 2 (1.7%) ventricular tachycardia with clinical symptom reproduction. There were 52 patients (45%) in the primary-ILR group and 63 (55%) in the post-CAT ILR group. Proportions of negative ILR monitoring (17/52 vs. 25/63; p = 0.56) and pacemaker implantations (7/52 vs. 15/63; p = 0.23) did not differ between groups. Baseline ECG conduction disorders predicted pacemaker implantation (n = 11/17; odds ratio:10.6; 95%CI: 3.15–35.3; p < 0.001). CAT was more often positive (73% vs. 40%; p < 0.001) in primary-ILR group. Conclusions: Primary ILR implantation was associated with more positive CAT compared with delayed ILR implantation, but negative monitoring and pacemaker implantations were not different between groups. ECG conduction disorders predicted subsequent pacemaker implantation.

Definitive aetiology of unexplained syncope after cardiovascular autonomic tests in a tertiary syncope unit

“…receiving an ILR rather than CAT as the first step in the investigation. 37 Regardless, an important aspect of negative CAT, including HUT is that these patients should receive an ILR, as emphasized by current ESC syncope guidelines, 1 and further corroborated by our observations. 37 However, even if an ILR is used, there is still a subset of unexplained syncope patients where the final syncope aetiology cannot be established, an obvious challenge for future research.…”

Recent Advances and Future Directions in Syncope Management: A Comprehensive Narrative Review

“…The 24-h Holter ECG is indicated in patients with very frequent syncope or presyncope (>1/week); otherwise, the diagnostic power is 1-2% [81]. For sporadic episodes, event recorders are more useful [82]. An external loop recorder can be used for recurrent syncope (>1/month), while an internal loop recorder is indicated for indeterminate syncope in high-risk patients, low-risk patients with a high probability of recurrence within 36 months (≥3 episodes in the previous 2 years), and to determine the contribution of bradycardia to TLOC (and thus to indicate PM implantation) in patients with reflex syncope [1,44].…”