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    • One day after implantation diaphragmatic stimulation was

    2019-05-09

    One day after implantation, diaphragmatic stimulation was observed when the patient was in the seated position, and it could not be resolved by reprogramming the device. We decided to replace the LV lead; however, there were no other vein branches suitable for CRT in the lateral region of the LV (Fig. 2A and B). We tried to insert the lead into an upper branch of the posterolateral vein, but we could not obtain a suitable pacing threshold. We replaced the LV lead more proximally in the same posterolateral vein, and confirmed that cyclooxygenase inhibitors stimulation was not observed on fluoroscopy during pacing at outputs of up to 10V. A postoperative 12-lead ECG showed a QRS duration of 128ms during biventricular pacing (Fig. 1B). The operation was performed under general anesthesia. A thoracoscopic procedure was carried out with a 3-port technique: 1 camera port (11.5mm) was placed in the eighth intercostal space at the mid-axillary line, and 2 working ports (5mm each) were placed in the fifth intercostal space at the anterior and posterior axillary lines. The left phrenic nerve was carefully detached from pericardial adipose tissue (Fig. 3A), and electrical insulation was accomplished with a 4×5cm2 Gore-Tex patch inserted between the phrenic nerve and the pericardium (Fig. 3B). The operative time was 112min and total blood loss was 3mL. No intraoperative or postoperative complications were observed. Following the procedure, the LV pacing threshold was 1.8V at 0.4ms and the impedance was 674Ω. The R-wave sensing threshold was 30.0mV. Diaphragm stimulation was not observed in any position during pacing at outputs of up to 10V.
    Discussion The present case report describes a patient who underwent successful thoracoscopic LV lead insulation to eliminate phrenic nerve stimulation during CRT. An echocardiography conducted at 2 years after implantation showed significant reverse remodeling (LV ejection fraction=48.9%, LV end-diastolic diameter=50mm, LV end-systolic diameter=35mm, and LV end-systolic volume=55.8mL). CRT has been demonstrated to improve systolic function in heart failure patients with conduction system disorders [1,2]. The stimulation site within the LV might play an important role in the outcome of CRT [3,4]. Transvenous LV lead implantation depends on the coronary venous anatomy. Coronary sinus angiography revealed that there were no other branches suitable for CRT (Fig. 2B). Lead insertion in the anterior or mid-cardiac vein may not result in optimal LV synchronization [5–7]. Furthermore, repeated implantation procedures are associated with an increased risk of device infection. Therefore, we decided not to perform LV lead replacement using a coronary vein-based lead system [8]. An epicardial LV lead implanted surgically was an option for the elimination of phrenic nerve simulation [9,10]. The surgical LV lead implantation could be performed using a thoracoscopic approach. Even though the epicardial side of the surgically implanted epicardial lead was insulated, in rare instances, this might cause phrenic nerve stimulation [11]. In most cases, a suitable site away from the phrenic nerve can be found. However, in CRT, the suitable area was limited to the mid-lateral region of the LV, and CRT with an epicardial lead implanted at the mid-lateral region of the LV can potentially result in a recurrence of phrenic nerve twitching [11]. Furthermore, the surgically implanted LV lead has to be connected with a subcutaneous CRT-D generator. In our case, a 12-lead ECG during biventricular pacing showed a narrow QRS width, and except for the phrenic nerve stimulation, the implanted lead position was appropriate for LV synchronization. We considered that the thoracoscopic placement of Gore-Tex insulation on the transvenous lead was a less invasive option than surgical LV lead implantation. Injury to the phrenic nerve and phrenic nerve paralysis are considerable potential complications of phrenic nerve electrical insulation. Furthermore, thoracoscopic phrenic nerve insulation requires general anesthesia, the risks of which should also be considered. We believe that replacement of the LV lead using a transvenous approach is the method of choice for the avoidance of phrenic nerve stimulation. However, when acceptable results cannot be obtained using the transvenous approach, as in our case, thoracoscopic phrenic nerve insulation represents a potential option for the management of uncontrollable phrenic nerve stimulation during CRT [12].