A Difficult Case of Diaphragmatic Stimulation

History

A 70-year-old woman with nonischemic cardiomyopathy, with New York Heart Association (NYHA) class III symptoms, a left ventricular ejection fraction (LVEF) of 22%, left ventricular end-diastolic dimension of 72 mm, QRS duration of 170 ms, and a left bundle branch block pattern ( Figure 33-1 ) was referred for possible cardiac resynchronization therapy defibrillator (CRT-D) implantation.

Comorbidities included hypertension, type 2 diabetes, dyslipidemia, obesity, and paroxysmal atrial fibrillation well controlled with amiodarone. Workup revealed moderate diffuse coronary artery disease (<40% narrowing), a 6-Minute Walk Test distance of 342 m, and a peak V o ₂ of 13.2 mL/kg/min.

Current Medications

Medical therapy was optimized with carvedilol 6.25 mg twice daily, fosinopril 20 mg daily, furosemide 60 mg daily, spironolactone 25 mg daily, amiodarone 200 mg daily, acetylsalicylic acid 80 mg daily, and dose-adjusted warfarin for a target INR 2.0–3.0.

First Intervention

Implantation of the CRT-D device was uneventful. However, the angiogram was of poor quality because of obesity and thus provided little guidance. It was not repeated given the patient’s underlying renal dysfunction (i.e., glomerular filtration rate ≤40 mL/min). Three coronary sinus branches were blindly identified. The anterior and posterior branches had septal courses. The bipolar left ventricular lead (1056K, St. Jude Medical, St. Paul, Minn.) was positioned in a long, large-caliber midlateral branch after confirming the absence of phrenic nerve capture despite high-output (10 V) pacing. Left ventricular pacing thresholds were 3.4 V for the distal electrode and 2.2 V for the proximal ring, both with the right ventricular coil as anode.