Seventeen patients enrolled the study (8 cases were in group 1, 9 cases in group 2). All patients had preserved AV conduction and had at least 1 HF hospitalization within 3 months before CRT/D implantation. Entresto (sacubitril/valsartan), β-blockers, and loop diuretics were prescribed to all patients.
Among the 17 patients, nine (52.9%) were male. All patients had cardiomyopathy (8 non-ischemic and 9 ischemic), and 6 patients had paroxysmal atrial fibrillation. Hypertension was present in 8 patients. Frequent ventricular premature contraction (VPC) (> 1,000 per 24 hours ) were found in 5 patients. The mean age was 69.1 ± 6.4 years, and the baseline characteristics of the patients were provided in Table 1. At baseline, the two groups were matched for age, gender, hypertension, diabetes mellitus, ICM, paroxysmal atrial fibrillation as illustrated in Table 1 (all P >0.05).
The echocardiographic indices, including LVEF, LVEDD, and NYHA classification, NT-proBNP were shown in Table 2. Baseline parameters were similar between the two groups (all P >0.05). The baseline LVEF and the baseline QRSd (Figure 1a) were 33.9 ± 3.9% and 168.2 ± 18.9 ms, respectively. At baseline, the two groups were matched for QRSd (158.0 ±13.0, vs. 176.7 ±19.7, P >0.05).
CRTDs were implanted in 15 patients (Figure 2a, 2b), and CRTPs were implanted in the remaining 2 patients (Table 3), one in each group. The operation duration was 135 ± 26 min. The duration of X-ray fluoroscopy was 25.2 ± 7.1 min.
In group 1, LBBA lead, RV lead and CS lead were successfully achieved in all 8 patients. In group 2, CS lead and RV lead was successfully implanted in all 9 patients. Compared with group 2, the operation duration was significantly prolonged and the duration of X-ray fluoroscopy tended to be longer in group 1 (Table 3).
Both groups did not show difference in CS pacing lead, RV defibrillator lead parameters, such as R-wave amplitude, threshold, and impedance and so on (Table 3). Both the LBBAP and CS capture thresholds remained stable during procedure (1.3 ± 0.6 V at 0.4 ms vs. 1.6 ± 0.7 V at 0.4 ms).
During the procedure, temporary RBBB and acute perforation of the ventricular septum were documented in 1 patient respectively in group 1. The lead was successfully repositioned and no pericardial effusion or cerebral ischemia was observed. In group 2, no complications were documented.
ECG characteristics and pacing parameters
Individual electrocardiographic responses to RV, CS, and LBBAP at the time of implantation were shown in Table 3. Among the 17 patients, the baseline QRSd was 168.1 ± 18.9 ms (Figure 1a).
In group 1, after unipolar LBBAP, 8 patients demonstrated a right bundle branch block (RBBB) pattern with a paced QRSd of 123.0 ± 5.7 ms (P = 0.001 vs. baseline) (Figure 1b). LBB potential could be recorded in 5 patients from the LBB lead (62.5%). The LVAT for all LBBAP patients was 72.5 ± 9.4 ms, and the R wave amplitude, pacing impedance, and unipolar pacing capture threshold were 9.9 ± 7.2 V, 678 ± 102 Ω, and 0.84 ± 0.17 V/0.4 ms, respectively.
In group 1, intra-operative BVP resulted in significant reduction of the QRSd from 158.0 ± 13.0 ms at baseline to 132.0 ± 4.5 ms (P=0.019) (Figure 1c). Compared with BVP, unipolar LBBAP resulted in further reduction of the QRSd to 123.0 ± 5.7 ms (P=0.006 vs. baseline and P=0.021 vs. BVP).
Post-operative LOT-aCRT resulted in a further reduction of the QRSd (121.0 ± 3.8 ms), but no statistical significance (P > 0.05).
In group 2, intra-operative BVP resulted in significant reduction of the QRSd from 176.7 ± 19.7 ms at baseline to 143.3 ± 8.2 ms (P = 0.011). However, compared with LOT-aCRT in group 1, BVP in group 2 has no any advantage in reducing QRSd (P > 0.05, Table 2).
As the aCRT algorithm provides mostly LV only pacing (Which means LBBAP in group1, CS pacing in group2) in patients with preserved AV conduction, the percentage of LV only pacing in the aCRT arm was high; 75.5% in the group 1 and 73.8% in group 2.
The mean follow-up time was 300 ± 185 days. At baseline, the two groups were matched for follow-up time (296 ± 201, 305 ± 190 days, P > 0.05). Among all 17 patients, CS lead parameters were stable during follow-up. In group 1, the LBBAP capture threshold, R-wave amplitude, and lead impedance were 0.74 ± 0.25 V, 13.36 ± 5.23 mV, and 533.73 ± 32.31 Ω during the 3-month follow-up (all P > 0.05, respectively, between the time of device implantation and the follow-up visit). In group 2, the RV lead parameters were also stable during follow-up. No patients showed signs of dislodgement, loss of capture, infections, embolism, or stroke associated with the implantation. The ventricular pacing rate was 95%. There were 8 VT/VF episodes treated with antitachycardia pacing that had an electrogram available for adjudication (3 episodes in group 1, 5 episodes in group 2). However, the rate of VT/VF therapy was not statistically different (P = 0.175) between two groups.
Transthoracic echocardiogram (Figure 2) evaluation data at baseline and at the 1-month and 3-month follow-ups were available in all 17 patients receiving successful aCRT. As shown in Table 3, the symptoms and the median NYHA classification score improved significantly, with the latter decreasing from 3.36 ± 0.50 to 2.45 ± 0.52 (P = 0.016). LVEF (33.9 ± 3.9% vs. 45.4 ± 8.7%, P = 0.002) and NT-proBNP (2937 ± 1646 vs. 1832 ±1541, P = 0.014) were brought a corresponding improvement at the follow-up visit significantly. LVEDD (65.1 ± 9.1 mm vs. 58.7 ± 10.2 mm, P = 0.319) was improved at the 3-month follow-up visit, but not significantly.
As compared to the base line, patients in group 1 showed significant improvement in LVEF and NT-proBNP levels, while patients in group 2 showed non-significant changes in these parameters (Table 3).