Results
MCOT was used to evaluate palpitations in 76 patients, syncope/presyncope in 17 patients, and to determine outcome of therapy in 29 patients. The baseline characteristics for each group are provided in Table 1 . Overall, the mean age was 58 ± 17 years and 57% were women. Structural heart disease was present in 33 patients (27%). Evaluation of Symptoms (Table 2)
Palpitations. Of 18 patients without a previous arrhythmia diagnosis, 14 (73%, +/+) reported symptoms during monitoring, all of whom had a diagnostic arrhythmia. Two of the 14 patients also had an autodetected asymptomatic arrhythmia (VT-NS and Brady). Recorded symptomatic arrhythmias included: PVCs (n = 7); ST (n = 3); Brady (n = 2); SVT (n = 1); and PACs (n = 1). One of four asymptomatic patients (-/+) had an autodetected VT-NS during monitoring.
Fifty-eight patients had previously been diagnosed with an arrhythmia using another monitoring system. Previously documented arrhythmias included: PAF (n = 26); PSVT (n = 17); AT (n = 4); VT-NS (n = 6); AFl (n = 2); inappropriate ST (n = 2); and PACs (n = 1). During the MCOT monitoring period, 34 (59%) patients experienced recurrent palpitations. In this symptomatic group of 34 patients, 27 patients (+/+) had a documented arrhythmia and seven patients (±) had no arrhythmia correlating to their palpitations. Of the patients with a symptomatic arrhythmia (+/+), two also had PSVT as an autodetected asymptomatic arrhythmia. Detected symptomatic arrhythmias included: PAF (n = 10); ST (n = 4); PVCs (n = 4); AT (n = 4); PSVT (n = 3); AFl (n = 2); PACs (n = 2); and VT-NS (n = 1). Interestingly, the documented arrhythmia was often different (nine of 27) from the previously detected symptomatic arrhythmia (Fig. 1). Furthermore, one patient had AF detected as the likely initiating arrhythmia for AFl (Fig. 2). Of the seven patients with symptoms but no documented arrhythmia (±), one had autodetected asymptomatic VT-NS. The remaining 24 (41%) patients in this group with a previously diagnosed arrhythmia were asymptomatic; however, 15 (-/+) had an autodetected arrhythmia during MCOT monitoring. Patients with autodetected arrhythmias included: AF (n = 7); VT-NS (n = 5); Brady (n = 3); AFl (n = 2); and PSVT (n = 1). Two of the 15 had at least two different autodetected asymptomatic arrhythmias.
Figure 1. (click image to zoom)
Symptomatic and asymptomatic arrhythmias in patients with palpitations and previously diagnosed arrhythmias. Note that many patients with a documented arrhythmia have a different arrhythmia on subsequent analysis.
Figure 2. (click image to zoom)
Tachycardia-induced tachycardia. Palpitations initially occurred during the onset of atrial fibrillation (A), which subsequently induced atrial flutter (B).
There were 36 episodes of AF/AFl, 22 episodes of bradycardia/pauses, six episodes of NSVT, and one episode of PSVT. The mean ventricular rate of the AF/AFl was 103 ± 27 bpm with a mean duration of 10.7 ± 14.1 hours. The PSVT lasted <1 minute at a rate of 175 bpm. Most of the asymptomatic arrhythmia episodes occurred between 10 PM and 6 AM: AF/AFl (n = 17, mean duration 7 ± 10.7 hours), Brady (n = 13), and PSVT. The second most frequent time to have an asymptomatic episode was 6 AM to 2 PM; AF/AFl (n = 12, mean duration 16.6 ± 18.4 hours), Brady (n = 7), and NSVT (n = 6). The least common interval to have an asymptomatic arrhythmia was 2 PM to 10 PM; AF/AFl (n = 7, mean duration 11.5 ± 13.6), and Brady (n = 2).
Syncope. Ten of 17 (59%) patients evaluated for presyncope/syncope had their typical symptoms during monitoring. Five of the symptomatic patients (+/+) had an arrhythmia documented: Brady (n = 2); AVB-2 (n = 1); VT-NS (n = 1); and PVCs (n = 1). In addition, three patients had autodetected asymptomatic arrhythmias (PAF in two and VT-NS in one). Of the remaining seven asymptomatic patients (-/+), three had autodetected arrhythmias (VT-NS in two patients and AF, AVB-2, and VT-NS in one patient). Mean time to patient-activated first event was 3.7 ± 4.2 days.
Previous Negative Evaluation. Fourteen of the patients being evaluated for palpitations (n = 6) and presyncope/syncope (n = 
had a previous negative arrhythmia workup ( Table 3 ). Electrophysiology study, Holter monitor, event monitor, or tilt table testing was performed in six, five, three, and one patient, respectively. MCOT was diagnostic in all six patients with palpitations: PVCs (n = 2); PSVT (n = 1); Brady (n = 1); PACs (n = 1); and ST (n = 1). Five of the eight patients with a previous negative evaluation being re-evaluated for presyncope/syncope had their symptoms during MCOT monitoring: SR in three and Brady in two. Both Brady patients had prolonged pauses (>4 seconds) that were directly related to their symptoms (Fig. 3).
Figure 3. (click image to zoom)
Presynope associated with a long pause after termination of atrial fibrillation.
Evaluation of Therapy
Twenty-nine patients were prescribed MCOT to evaluate therapy efficacy, 21 for medication titration, and eight following radiofrequency ablation. Ventricular rate control of AF (n = 10) and AT (n = 4) was monitored with MCOT in 14 patients using AV nodal blocking drugs. The AV nodal blocking medications utilized included: beta-blockers (n = 10); digoxin (n = 5); and calcium channel blockers (n = 5). Seven patients required further medication titration for adequate ventricular rate control, which was accomplished in the outpatient setting with continued MCOT monitoring. Two patients treated for rate control of AF developed symptomatic prolonged pauses (up to 6.5 seconds) that MCOT monitoring documented, the drug doses were promptly changed, and the patients had no adverse consequences. Both patients ultimately underwent permanent pacemaker implantation for tachycardia-bradycardia syndrome. One patient with a history of poorly controlled hypertension and bradycardia was monitored with MCOT for beta-blocker initiation. Adequate blood pressure control was obtained without a recurrence of bradycardia. Six patients were monitored with MCOT for attempted rhythm control using antiarrhythmic medications: four with AF; one with VT-NS; and one with PVCs. Antiarrhythmic medications used for rhythm control in these patients included amiodarone (n = 6), sotalol (n = 3), propafenone (n = 1), and mexiletine (n = 1).
Eight patients underwent MCOT monitoring following radiofrequency ablation for AF (n = 5), AFL (n = 1), PVCs (n = 1), and inappropriate ST (n = 1). Two patients experienced symptoms during MCOT monitoring. One patient experienced symptomatic PACs and the other had SR during their symptomatic episode. There was one occurrence of asymptomatic AF in a patient following radiofrequency ablation of AF. Printer- Friendly Email This
J Cardiovasc Electrophysiol.