A Novel Device System for a Patient with Intermittent AV Block and at Risk for Sudden Cardiac Death

Introduction

Sarcoidosis is described as a chronic multisystem inflammatory condition of uncertain etiology, characterized by the formation of epithelioid lesions throughout the body, primarily in the lungs and thoracic cavity. The overall prevalence in the U.S. is 10–40 cases/100,000, with a lifetime risk of 0.85% (Caucasians) and 2.4% (African-Americans).¹ Sarcoidosis generally affects patients in their mid-twenties to mid-forties. Cardiac sarcoidosis has been known to give rise to heart failure, arrhythmias and sudden cardiac death (SCD).^2,3

Case Description

Our patient is a 34-year-old African-American male, with a past medical history of well-controlled hypertension and sarcoidosis. He presented to the hospital with complaints of dizziness and syncope, and was found to be in intermittent complete heart block. His underlying rhythm, while not in complete heart block, was first-degree AV block with bifascicular block. Also noted were episodes of non-sustained VT. The patient was transferred to the Cardiac Intensive Care Unit and a cardiac MRI was obtained. The MRI demonstrated transmural involvement of the sarcoidosis high in the interventricular septum (Figure 1). At this point, it was felt that ICD implant was warranted.⁴

Discussion

Due to the patient’s young age and diagnosis, the BIOTRONIK Ilesto DX and a Linox^smart S DX lead were chosen. We felt the combination of this lead and device offered the best outcome for this patient. The Ilesto ICD offers defibrillation therapy for this patient’s risk of sudden cardiac death and provides AV sequential pacing for his intermittent complete heart block. A DX system and Linox^smart S DX lead (a single-coil ventricular lead with an atrial dipole) limits the amount of hardware. In addition, this ICD is one of the smallest available. 

The patient tolerated the implant procedure well. DFT testing was deferred. R-waves were 18.8 mV; the pacing threshold was 0.4V at 0.4 ms, and the pacing lead impedance was 751 ohms. Atrial sensing was 7–9 mV through the PSA and 21 mV through the device. (Figure 2) The device was programmed to VDD 45–140 bpm. The AV delay was set to 180 ms with an AV optimization algorithm called I-Opt turned on, which should reduce unnecessary chronic RV pacing. Tachycardia detection and therapies were programmed as follows: VT-1: OFF; VT-2: 350 ms with anti-tachycardia pacing (ATP) and high-voltage therapies programmed; VF: 270 ms with ATP and high-voltage therapies programmed. The SVT discriminator was also programmed ON for detection and redetection, as was BIOTRONIK Home Monitoring^®.

Approximately three weeks post implant, a Home Monitoring^® transmission was initiated by an automatic alert. The patient had experienced an episode of SVT in the VT-2 zone for which therapy was appropriately withheld. (Figure 3)

Of note, this transmission also indicated that P-waves were >8.0 mV, R-waves >20.0 mV, there was no evidence of atrial fibrillation, and the percentage of RV pacing was less than 1%.

Implications

In this case, we have a patient with sarcoidosis and a diagnosis of intermittent AV block who is at risk for sudden cardiac death. This patient was in need of AV sequential pacing and an ICD; however, the safety and efficacy of dual-chamber ICD systems have been questioned. For example, citing data from the NCDR database, Dewland et al wrote that ICD patients who have atrial leads implanted are at increased risk of peri-procedural death and serious complications.⁵ Peterson et al found that long-term outcomes are no worse for single-chamber ICDs but that complications are less than in dual-chamber systems in primary prevention patients.⁶ Currently there is only one ICD system that can provide both AV sequential pacing and high-voltage (as well as ATP) therapy utilizing only a single lead: the BIOTRONIK DX system.

Summary

The DX system utilizing a single-coil ICD lead with atrial dipole is capable of atrial sensing and AV synchronous pacing. In addition, atrial diagnostics and SVT discrimination are available. The DX ICD circuitry is specifically designed for improved atrial sensing when using the Linox^smart S DX lead, and the device offers a full complement of high-voltage and ATP therapies. In addition, the system includes wireless remote monitoring. The device automatically connects to the Home Monitoring^® site and transmits diagnostics and device status.

Disclosure: Dr. Moore has no conflicts of interest to report regarding the content herein.  

References

1. Sarcoidosis. Patient.co.uk. Published October 26, 2012. Available online at https://www.patient.co.uk/doctor/sarcoidosis#. Accessed December 2, 2013. 
2. Bagwan IN, Hooper LV, Sheppard MN. Cardiac sarcoidosis and sudden death. The heart may look normal or mimic other cardiomyopathies. Virchows Arch. 2011;458:671-678. 
3. Kusano BK, Kusano KF, Nakamura K, et al. Relationship between arrhythmogenesis and disease activity in cardiac sarcoidosis. Heart Rhythm. 2007;4:1292-1299. 
4. Epstein AE, DiMarco JP, Ellenbogen KA, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Anti-arrhythmia Devices): Developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Circulation. 2008;117:e350-e408.
5. Dewland TA, Pellegrini CN, Wang Y, et al. 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.
6. Peterson PN, Varosy PD, Heidenreich PA, et al. Association of single- vs.  dual-chamber ICDs with mortality, readmissions, and complications among patients receiving an ICD for primary prevention. JAMA. 2013;309:2025-2034.