Study Patients
From July 09, 2017 through August 27, 2018, we prospectively enrolled consecutive patients with persistent AF who were admitted to the cardiology ward at the Chaim Sheba Medical Center (Tel Hashomer, Israel) for elective electric cardioversion. Our study inclusion criteria were: 1) age ≥ 18 years old, 2) symptomatic persistent AF/AFL (atrial fibrillation or atrial flutter), 3) baseline QTc>300 msec, 4) no contraindication for ECV, and 5) no contraindication for anticoagulation. Study exclusion criteria included: 1) recent initiation of medication that is well known to prolong QTc, 2) recent increase in dose of potentially prolonging medication (other than the medication desired for the CV), 3) pregnancy, 4) patients with congenital long QT syndrome, 5) baseline QTc>500 msec, and 6) history of Torsade de pointes. Out of 136 consecutive patients, 100 patients agreed to participate in the study. All enrolled patients were connected to a 7-day 3-lead Holter prior to CV (in order to monitor QTc during AF)(Figure 1).
All patients underwent transesophageal echocardiography (TEE) if effective anticoagulation status was not confirmed or upon physician discretion. In addition, all underwent transthoracic echocardiography (TTE) within three months prior to the study enrollment, or on the day of CV. Of note, after connecting patients to Holter, ten patients (10%) were withdrawn from the study due to left atrial appendage thrombus or severe swirling in TEE (4 patients), Holter malfunction (3), failure to cardiovert to sinus rhythm (2) and a patient who spontaneously converted to sinus rhythm following TEE, who was mistakenly discharged without further Holter monitoring. All remaining 90 patients were successfully CV to sinus rhythm and were monitored according to the study protocol using the Holter for 7 days.
The protocol was approved by the institutional review board of our center. All patients provided written informed consent. The primary hypothesis was that signifcant QTc prolongation can occur following ECV during 7 days of prolonged ECG monitoring, and that the use of Holter would be superior to the conventional protocol in detecting potentially clinically significant QTc prolongation.