33. A Difficult Case of Diaphragmatic Stimulation

Published on 26/02/2015 by admin

Last modified 26/02/2015

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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 VO₂ 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.

Outcome

The following morning, the patient reported symptoms consistent with diaphragmatic stimulation. On interrogation, the best left ventricular capture threshold was 3.75 V (proximal ring to right ventricular coil) and both pacing electrodes elicited phrenic nerve capture at voltages down to 3.25 V. It was impossible to identify a pacing configuration with a left ventricular threshold lower than that of the phrenic nerve capture threshold. The lead appeared to be well positioned on chest radiograph.

Second Intervention

A second intervention was therefore performed to rectify the situation. Other potential coronary sinus branches could not be identified. The anterior branch was of small caliber and too far septal and the proximal posterior branch (middle cardiac vein) was deemed unsuitable. A new 1056K left ventricular lead was implanted in the same venous branch. Phrenic nerve capture occurred from both electrodes, but only on deep inspiration. The problem was far less pronounced in a very proximal position. The lead was not wedged into place in the hope that its spiral design would ensure stability.

Outcome

The following day, good functioning of the CRT system was confirmed by interrogation. Nevertheless, the patient presented 1 month later with a dislodged left ventricular lead positioned deeply and anteriorly in the main coronary sinus. Epicardial implantation was considered and discussed, but declined by the patient.

Five years later, she remained with NYHA class III symptoms and had four heart failure–related hospitalizations within 8 months. Her left ventricular systolic function remained stable (LVEF 20%; left ventricular end-diastolic dimension 70 mm). Meanwhile, she developed new-onset complete atrioventricular block and became dependent on right ventricular pacing.

Two months previously, she presented with recurrent presyncope. Intermittent ventricular oversensing (Figure 33-2

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