Elsevier

American Heart Journal

Volume 148, Issue 2, August 2004, Pages 326-332
American Heart Journal

Clinical investigation
Detection of asymptomatic arrhythmias in unexplained syncope

https://doi.org/10.1016/j.ahj.2004.01.024Get rights and content

Abstract

Background

Although electrocardiographic monitoring during syncope is the most unambiguous method of diagnosing or excluding an arrhythmia, it requires recurrence of syncope with potential morbidity. We hypothesized that long-term monitoring of patients with syncope would yield significant asymptomatic abnormalities that might preclude waiting for recurrence of actual syncope.

Methods

Sixty patients (age, 67±16 years; 27 men) with recurrent unexplained syncope, aged ≥30 years, with a left ventricular ejection fraction ≥35% and negative results on conventional monitoring were enrolled in a prospective study involving long-term automatic arrhythmia detection monitoring with an implantable loop recorder. Pre-specified significant asymptomatic arrhythmias were a pause >5 seconds, 3° atrioventricular block >10 seconds, heart rate (HR) <30 beats/min for >10 seconds while awake, wide complex tachycardia >10 beats, and narrow complex tachycardia >180 beats/min for >30 beats. Borderline asymptomatic arrhythmias included 3- to 5-second pauses, HR <30 beats/min for <10 seconds while awake, HR <30 beats/min for >10 seconds while asleep, and nonsustained wide complex tachycardia or narrow complex tachycardia.

Results

Recurrent symptoms developed in 30 patients during the 1-year follow-up period (47%), with arrhythmias detected in 14 patients (23%). Pre-specified significant asymptomatic arrhythmias developed in 9 patients (15%), with bradycardia in 7 patients who underwent pacemaker implantation. Twenty patients (33%) had borderline asymptomatic arrhythmias. Five of these patients (25%) went on to have more pronounced diagnostic arrhythmias of the same mechanism during further follow-up, including pauses of 6 to 17 seconds duration in 3 patients.

Conclusion

Long-term monitoring of patients with unexplained syncope with automatic arrhythmia detection demonstrated that significant asymptomatic arrhythmias were seen more frequently than anticipated, leading to a change in patient treatment. Automatic arrhythmia detection provides incremental diagnostic usefulness in long-term monitoring of patients with syncope.

Section snippets

Patients

Patients referred to the Arrhythmia Service at the University of Western Ontario for investigation of syncope with a left ventricular ejection fraction >35% were approached to participate in a prospective trial assessing the benefit of automatic detection loop recorders in patients with unexplained syncope and preserved left ventricular function. Consecutive patients were approached to participate in the trial when they had recurrent unexplained syncope or a single episode of syncope associated

Results

Sixty patients with unexplained syncope were enrolled in the trial (Table I). All patients underwent echocardiography and 24 hours of ECG monitoring before enrollment to confirm eligibility. The outcome of patients during the 1-year monitoring period is summarized in Figure 1. Symptoms recurred in 30 patients (50%) during the 1-year follow-up period. Eleven of these patients experienced borderline asymptomatic arrhythmias before their symptomatic episode (see below). Sinus node disease with

Discussion

Prolonged monitoring of patients with unexplained syncope with an autodetect implantable loop demonstrated frequent asymptomatic arrhythmias. These “subthreshold” arrhythmias did not result in symptoms that came to clinical attention, but were sufficiently marked that they could not be ignored in the context of unexplained syncope. Pre-specified asymptomatic arrhythmias developed in 15% of patients, leading to treatment decisions that resulted in resolution of syncope. We chose marked

References (35)

  • Sivakumaran S, Krahn AD, Klein GJ, et al. A prospective randomized comparison of loop recorders versus Holter monitors...
  • E.B. Bass et al.

    The duration of Holter monitoring in patients with syncopeis 24 hours enough?

    Arch Intern Med

    (1990)
  • W.N. Kapoor

    Evaluation and management of the patient with syncope

    JAMA

    (1992)
  • W.N. Kapoor

    Diagnostic evaluation of syncope

    Am J Med

    (1991)
  • W.N. Kapoor

    Evaluation and outcome of patients with syncope

    Medicine (Baltimore)

    (1990)
  • G. Gregoratos et al.

    ACC/AHA Guidelines for Implantation of Cardiac Pacemakers and Antiarrhythmia Devicesexecutive summary—a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Pacemaker Implantation)

    Circulation

    (1998)
  • H.G. Li et al.

    The value of electrophysiologic testing in patients resuscitated from documented ventricular fibrillation

    J Cardiovasc Electrophysiol

    (1994)
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    Supported by a grant from the Heart and Stroke Foundation of Ontario (NA3397). Dr Krahn is a research scholar of the Heart and Stroke Foundation of Canada.

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