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A counterpulsation device (Symphony) that works synchronously with the native heart to provide partial circulatory support was developed to treat patients with advanced heart failure. Symphony is implanted in a 'pacemaker pocket' without entry into the chest, and requires timing with ECG for device filling and ejection. Surface leads are limited to short-term use due to signal distortion and lead management. Transvenous leads are a clinical standard for pacemakers and internal defibrillators, but increase the complexity of the implant procedure. In this study, the feasibility of using subcutaneous leads for synchronized timing of Symphony was investigated. ECG waveforms were simultaneously measured and recorded using epicardial (control) and subcutaneous (test) leads in a bovine model for 7-days (n = 6) and 14-days (n = 2) during daily activity and treadmill exercise. Landmark features and R-wave triggering detection rates for each lead configuration were calculated and compared. Lead placement, migration, durability, and infection were quantified using fluoroscopy and histopathological examination. There were 2,849 data epochs (30-s each) recorded at rest (133,627 analyzed beats) and 35 data epochs (20 min each) recorded during treadmill exercise (37,154 analyzed beats). The subcutaneous leads provided an accurate and reliable triggering signal during routine daily activity and treadmill exercise (99.1 ± 0.4% positive predictive value, 96.8 ± 1.5% sensitivity). The subcutaneous leads were also easily placed with minimal lead migration (0.5 ± 0.1 cm), damage (no fractures or failures), or infection. These findings demonstrate the feasibility of using subcutaneous leads for synchronized timing of mechanical circulatory support while offering the advantage of less invasive surgery and associated risk factors.

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Counterpulsation devices (CPD) require an accurate, reliable electrocardiogram (ECG) waveform for triggering inflation and deflation. Surface electrodes are for short-term use and transvenous/epicardial leads require invasive implant procedure. A subcutaneous ECG lead configuration was developed as an alternative approach for long-term use with timing mechanical circulatory support (MCS) devices. In this study, efficacy testing was completed by simultaneously recording ECG waveforms from clinical-grade epicardial (control) and subcutaneous (test) leads in chronic ischemic heart failure (IHF) calves implanted with CPD for up to 30 days. Sensitivity and specificity of CPD triggering by R-wave detection was quantified for each lead configuration. The subcutaneous leads provided 98.9% positive predictive value and 98.9% sensitivity compared to the epicardial ECG leads. Lead migration (n=1) and fracture (n=1) were observed in only two of forty implanted leads, without adversely impacting triggering efficacy due to lead redundancy. These findings demonstrate the efficacy of subcutaneous ECG leads for long-term CPD timing and potential use as an alternative method for MCS device timing.