Case report on investigational modular cardiac rhythm management system: wireless communication between leadless pacemaker and subcutaneous defibrillator in cardiac sarcoidosis with limited vascular access.

Background: Cardiac sarcoidosis (CS) is a granulomatous inflammatory disorder that can result in high-grade conduction disease and ventricular arrhythmias, often necessitating permanent pacing and defibrillator support. The transvenous system is particularly challenging in CS with immunosuppression, limited vascular access, and a history of chemotherapy. Traditional transvenous systems may be poorly suited for this immunocompromised population. Case summary: A 52-year-old woman with a history of breast cancer treated with neoadjuvant chemotherapy and biopsy-confirmed systemic sarcoidosis who presented with shortness of breath and was found to have cardiac involvement based on cardiac magnetic resonance imaging and cardiac positron emission tomography findings, leading to immunosuppressive therapy. She developed non-sustained ventricular tachycardia, followed by high-grade and complete heart block, qualifying her for pacing and defibrillator therapy based on current consensus recommendations. Due to limited vascular access (left-sided mastectomy and right-sided port for chemotherapy), cardiac inflammation, and ongoing immunosuppression, an investigational modular cardiac rhythm management (mCRM) system was used, comprising a leadless pacemaker and a subcutaneous implantable cardioverter defibrillator (S-ICD). The patient remained free of new arrhythmias during follow-up and after starting systemic chemotherapy for sigmoid adenocarcinoma. Discussion: The mCRM system manages both bradyarrhythmia and ventricular tachyarrhythmia without the need for intravascular leads. The S-ICD continuously monitors for ventricular arrhythmias and wirelessly commands the leadless pacemaker to deliver anti-tachycardia pacing when indicated, potentially avoiding shocks. By eliminating transvenous components, the mCRM system offers a reasonable approach in CS with immunosuppression and limited vascular access.