Case Study: Remote Monitoring in the Management of a Complex Patient with a Single-Lead Dual-Chamber ICD

Introduction

The wealth of clinical data available today to help clinicians make better decisions for patients is astounding for anyone who has been in practice for even a few years, let alone the more than 25 that I have been in practice. However, despite the investments of time, effort, and money, evidence-based practice for patients with multiple comorbidities remains largely empiric. These patients are routinely excluded from studies due to the infinite number of confounding variables their participation would introduce. Here we discuss one such patient, and the value that device-based monitoring brings to their individualized plan of care.

Discussion

In early March 2013, a 50-year-old male patient arrived in the ER complaining of gastric pain, nausea/vomiting, body aches, fever, and chills, all of recent onset. While being evaluated, he suffered a cardiac arrest (sustained ventricular tachycardia [VT]), which was successfully resuscitated. The patient was admitted to the ICU and found to be in renal failure, and also had concomitant acute hypoxic hepatitis (liver shock). He began dialysis, stabilized, and eventually underwent a cardiac catheterization that demonstrated no coronary disease. An echocardiogram revealed an ejection fraction of 30-35% and non-ischemic cardiomyopathy. The patient’s medical history also included well-controlled hypertension but was negative for atrial arrhythmia. His underlying rhythm was sinus with a narrow QRS and without evidence of a conduction block.

The patient was later implanted with the BIOTRONIK Lumax 740 VR-T DX, a single-lead ICD that provides atrial sensing and diagnostics, heart failure (HF) diagnostics, synchronized ventricular pacing, antitachycardia pacing (ATP), and high-voltage therapies. The implant was unremarkable. The lead was positioned in the RV apex, leaving enough slack to position the atrial dipole in the mid-to-low right atrium. P-waves obtained via the ICD were 6-8 mV and R-waves 6-7 mV. DFTs were not obtained. Right ventricular pacing thresholds were <1.0 v at 0.4 ms. Right ventricular lead impedance was 500-550 ohms and the HV lead impedance was 75 ohms. The device was programmed to VDD 60/130 with an AV delay of 350 ms. VT1 zone was programmed to 16 cycles at 350 ms detection, with two attempts at ATP burst for the first two therapies and HV shocks thereafter (therapies 3-8). The SVT discrimination algorithm was programmed ON. The VT2 zone was off. VF zone was programmed to 8/12 cycles at 300 ms. No ATP was programmed for the VF zone, relying on high-voltage therapy only. The patient was discharged on amiodarone 200 mg QD.

Throughout most of follow-up, the patient course was unremarkable. We noted two discrete ventricular fibrillation (VF) episodes that self-terminated; these occurred approximately eight months post implant (late November 2013). There were no recorded atrial arrhythmia, but we did note some mode switch episodes. (The discrepancy is explained by different criteria we programmed for mode switch detection vs arrhythmia recordings.) In any event, the total atrial arrhythmia burden was 0% from March 2013 to December 2013, and all remote monitoring transmissions were routine.

On January 1, 2014, the automatic remote monitoring system (BIOTRONIK Home Monitoring^®) notified the clinic of an atrial arrhythmia lasting several minutes (Figure 1). We saw the patient in our clinic on January 9th, and by this time, a second atrial tachycardia had been recorded and transmitted by the remote monitoring system. Note: the patient’s HF was being followed by another physician.

Beginning in late January, the patient experienced several more atrial arrhythmias that were recorded and promptly reported via the remote monitoring system. A review of the transmitted IEGMs indicated these were most likely atrial fibrillation (AF) (Figure 2). In addition, a third self-terminating VF episode occurred. In late January, the patient had several sustained VT episodes (Figure 3) over a 15-20 minute period, all of which responded to ATP.

Implications

The incidence of atrial tachycardia in device patients is high. For example, Healy et al report that within three months of implant, more than 10% of device patients in their series of over 2500 patients had subclinical atrial tachycardia (primarily AF) as detected by device diagnostics (p = .001).¹ In our case study, the diagnosis of atrial tachycardia is important as the arrhythmia was not previously diagnosed. In addition, by monitoring for and reporting on the ventricular response to atrial tachycardia, we are in a position to take appropriate steps should we find the response uncontrolled, mitigating the likelihood of further deterioration in hemodynamics due to a tachycardia-induced cardiomyopathy.

Atrial diagnostics and monitoring in an ICD system typically require the use of a dual-chamber ICD system. Given the data from the recently published analysis of the NCDR database, which indicates that adverse events and in-hospital mortality were more frequent in dual-chamber than single-chamber ICD recipients,² it seems prudent to minimize the risk of complication in a patient with HF and several comorbidities, especially when there is no compromise in device functionality.

Conclusion

The Lumax 740 VR-T DX, when coupled with the BIOTRONIK Home Monitoring^® system, can be a powerful tool to help manage complex patients. In this case, the device reliably identified, correctly discriminated, and promptly transmitted data on both atrial and ventricular arrhythmias. The atrial IEGM was instrumental in confirming the device’s rhythm classifications. It appropriately provided ATP during the VT episode, as well as withheld therapies when faced with self-terminating VF. Utilizing the remote monitoring system, we were able to evaluate device performance, determine actionable events and interventions, and avoid needless in-clinic visits and rehospitalizations. This system also provides important information to the HF clinic, permitting them to manage the patient’s condition with equal efficiency.

Editor’s Note: This article underwent peer review by one or more members of EP Lab Digest’s editorial board.

Disclosures: Mr. McKenna reports employment with BIOTRONIK. Outside the submitted work, Dr. Kaufman reports consultancy with BIOTRONIK, Boston Scientific, and Medtronic; he reports his group is currently participating in BIOTRONIK-sponsored clinical studies and has also participated in clinical studies sponsored by Boston Scientific and Medtronic. Dr. Kaufman also reports attending educational programs by BIOTRONIK, Boston Scientific, and Medtronic and having travel/accommodations expenses covered or reimbursed. 

References

1. Healey JS, Connolly SJ, Gold MR, et al. Subclinical atrial fibrillation and the risk of stroke. N Engl J Med. 2012;366:120-129.
2. Dewland T, Pellegrini CN, Wang Y, Marcus GM, Keung E, Varosy PD. Dual-chamber implantable cardioverter-defibrillator selection is associated with increased complication rates and mortality among patients enrolled in the NCDR implantable cardioverter-defibrillator registry. J Am Coll Cardiol. 2011;58:1007-1013.