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    • Treatment administered thereafter involved approaches Becaus

    2019-04-15

    Treatment administered thereafter involved 2 approaches. Because the patient had LV dyssynchrony with LBBB, we planned to implant a biventricular pacing device. A CRT-D was chosen despite the absence of syncope and non-sustained ventricular tachycardia. The choice of the device was based on the presence of ventricular tachycardia in conjunction with a low EF in this case and previous reports suggesting the arrhythmogenic nature of biventricular pacing [1]. Before implantation, we performed catheter ablation to treat the patient\'s AF, which had the potential to prevent the establishment of a sufficient biventricular pacing rate and could lead to the generation of inappropriate shocks. We also believed that ablation therapy could boost the cardiac performance by recovering sinus rhythm. At the time of the operation, the left atrial dimension was 46mm. The outcome of AF ablation was positive. The patient successfully recovered sinus rhythm; his AT level increased to 12.0mlkg−1min−1; and his BNP level decreased from 259 to 119pg/ml. We then performed CRT-D implantation. The CRT-D used was a Lumax 540 HF-T, and the shock lead was a Linox S65, which is a true bipolar lead (BIOTRONIK, Berlin, Germany). The CRT-D was programmed as follows: the pacing mode was set at dual-chamber (DDD); basic rate, 60bpm; AV delay, 150ms; VV delay, 0ms; the upper tracking rate, 130ms; the right ventricular (RV) sensitivity, 0.4mV; LV sensitivity, 1.6mV. The RV amplitude was set at 7.9mV, and LV amplitude, at 28mV. The RV pacing threshold was maintained at 0.4V, and LV pacing threshold, at 0.8V. Biventricular pacing yielded a narrow QRS complex at a duration of 100ms. No arrhythmias or major issues were detected at monthly device checks and during remote home monitoring for more than 2 months after device implantation. However, we noticed a spike on the T wave in the 12-lead electrocardiogram 3 months after CRT-D hypoxia inducible factor (Fig. 1). Device checks revealed T-wave oversensing and a pacing spike on T wave caused by the LV-triggered pace algorithm (Fig. 2). LV pacing was performed at the same time as the T wave was sensed because extracellular route algorithm misjudged the T wave as a PVC originating from the right ventricle. At that time, the RV amplitude was set at 9.0mV. After this algorithm was discontinued, the spike on the T wave did not occur again. However, T-wave oversensing continued to be observed. The CRT-D device allows for changing the T-wave sensing threshold and filter settings to eliminate oversensing. After changing the sensing threshold, we confirmed the ventricular sensing threshold and set the ventricular sensing parameter to 2.0mV. Thereafter, PVCs thought to represent T-wave oversensing were not observed, as was also confirmed via remote home monitoring. Moreover, this alteration in the sensing threshold did not affect the detection of ventricular fibrillation. We did not change the “RVs” mode of the LV-triggered algorithm because the patient maintained sinus rhythm and had few PVCs (confirmed via remote home monitoring). During the follow-up period, the CRT-D parameters, e.g., P wave, RV and LV amplitudes, and thresholds, remained unchanged. After the sensing threshold was changed, the biventricular pacing rate was maintained more than 99% of the time. His cardiac function improved: the CTR was 44%; the LVDd/LVDs was 61/46mm; and the EF was 47% at about 4 months after device implantation.
    Discussion It is obvious that CRT improves the prognosis of patients with a low EF and LV dyssynchrony. Therefore, retaining a biventricular pacing rate is important in these patients [2–6]. However, patients with AF do not benefit from CRT to the same extent as those in sinus rhythm [7–11]. This is mainly due to a low biventricular pacing rate in AF cases. Methods employed to maintain a high percentage of biventricular pacing rate include the pharmaceutical rate-control approach of administering betablockers or even performing AV nodal ablation. Several CRT device algorithms have been developed to maintain the biventricular pacing rate. The LV-triggered pace algorithm, which is used in BIOTRONIK devices, is one of them.