Implantable ECG Monitoring for Diagnosis of Atrial Flutter

Background

A 53-year-old male presented with syncope, palpitations, untreated hypertension and possible Wolff-Parkinson-White syndrome. There was no evidence of diabetes or other chronic illness. Although the EP study results were negative, the patient had experienced palpitations and syncope clinically. Since the patient worked as an operator of heavy machinery for construction, he expressed concern that he would no longer be able to run a bulldozer and retain his job. Therefore, the patient was referred for an implantable cardiac monitor implant for further analysis.

Implantable ECG Monitoring System

The patient was implanted with a wireless, high-definition implantable monitoring device, part of the Sleuth® Implantable ECG Monitoring System (Transoma Medical, Inc., St. Paul, MN). The Sleuth system includes the implanted device, a handheld Personal Diagnostic Manager (PDM), which holds up to 10.5 hours of data between automatic and regular downloads, and a Base Station that is placed in the patient’s home (Figure 1). From the Base Station, data are automatically forwarded to a 24/7 monitoring center for human analysis of all recorded data. Patient-triggered events associated with symptoms are captured when a patient pushes the “Activate” button on the wireless PDM. ECG data is also captured automatically when the heart rate exceeds physician-programmed settings (Figure 2). The heart rate settings for this patient were set to 165 bpm for tachycardia.

Analysis and Diagnosis

About two months post-implant, the patient experienced symptoms and pressed the PDM button to capture ECG data. Onset showed sinus tachycardia converting to atrial flutter (150–300 bpm), then converting to sinus rhythm. Prior ECG recordings suggested a trend of sinus bradycardia. The monitoring center contacted us by phone, then faxed and emailed the report according to our customized notification criteria. Events led to a diagnosis of 1:1 atrial flutter (AF) (Figure 3).

Treatment and Ongoing Monitoring

Two weeks later, the patient was admitted for a cavotricuspid isthmus (CTI) AF ablation procedure. This procedure uses radiofrequency ablation to burn the isthmus between the inferior vena cava and the tricuspid valve. The success rate from this particular procedure is high (approximately 95%). However, diagnoses of atrial flutter are far less common than that of atrial fibrillation, for which a different ablation procedure would be used. The timeline for this process started with the device implant on March 12, 2008. Atrial flutter was captured by the device on May 13, 2008, and the CTI ablation took place on June 2, 2008. Since undergoing ablation, the patient has returned to work and is feeling better. The device remains implanted to continue monitoring the patient’s status and the effectiveness of the CTI ablation procedure. The last follow-up appointment was on November 2, 2008, where the patient reported no further symptoms.

Discussion

In this instance, by not explanting the device after treatment, we will continue to receive data on therapeutic effectiveness. For any subsequent cardiac events, we will be able to receive reports according to our customized notification criteria. With the Sleuth Implantable ECG Monitoring System, notification can be customized for each individual patient (e.g., phone call for arrhythmias >150 bpm; email for sinus tachycardia >150 bpm) based on the urgency of response required. This is helpful in monitoring for specific event-related characteristics. The Sleuth system can be used to help diagnose, or rule out, arrhythmia causes for syndromes such as: • Syncope and near syncope. • Seizure-like episodes or convulsions. • Symptomatic atrial fibrillation. • Drug-refractory epilepsy. • Transient, recurring palpitations.