Safety and efficacy of trans-right-ventricular echocardiography guided percutaneous intramyocardial septal radiofrequency ablation for interventricular septal reduction: an ovine model with 1-year outcomes / 中华超声影像学杂志

ABSTRACT

Objective:To investigate the safety and efficacy of echocardiography-guided trans-right-ventricular percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) in a healthy sheep model, and to observe the pathological changes of myocardium in ablation area one year later.Methods:Twelve sheep were divided into PIMSRA group ( n=6) and sham group ( n=6). In PIMSRA group, a radiofrequency (RF) electrode was inserted to the interventricular septum (IVS) with maximum power of 80 Watts for 5 minutes. In the sham group, RF electrode tip was positioned in IVS segment but without the RF power delivery. Electrocardiogram (ECG), echocardiography, myocardial contrast echocardiography(MCE) were performed to assess the efficacy of PIMSRA at postoperative immediately, 2-week, 1-month, 2-month, 3-month, 6-month and 12-month during the follow-up. The following parameters were recorded, including the thickness of ablation area, the systolic wall thickening rate and amplitude of movement of the ablated region, left ventricular outflow tract pressure gradient (LVOT PG), and left ventricular ejection fraction (LVEF), mitral valve early diastolic peak velocity(E), late diastolic peak velocity(A) and the E/A ratio, peak velocity of early diastolic mitral annular motion(E′), peak velocity of late diastolic mitral annular motion(A′), and the E′/A′ ratio.For both groups, the myocardial biomarkers of troponin I, myoglobin and isoenzymes of creatine kinase were tested before the ablation and 3 h after the ablation, and again after 2 weeks. Tissue pathology examinations were performed at the end of study. Results:None of the animals in both groups was observed to have pericardial tamponade during perioperative period.Immediately after the procedure, septal hypokinesis was seen in all PIMSRA group animals, the systolic wall thickening rate and amplitude of movement of the ablated region were significantly decreased ( P<0.001), which was sustained until 12 months.In Sham group, there were no significant differences in the wall thickening rate and amplitude of movement of the operated region(all P>0.05).The thickness of the ablation area in the PIMSRA group was significantly increased immediately after the procedure( P<0.001), decreased to baseline level at 1-week ( P=0.931), and significantly increased at 3-month ( P<0.001).In the Sham group, the IVS thickness was significantly increased immediately after the procedure( P=0.005), decreased to baseline level at 1-week ( P=0.027), then has no further significant changes.There were no significant differences in LVEF, E/A, E′/A′ between PIMSRA and Sham group(all P>0.05).MCE showed the thickness of the ablation area was significantly decreased in the PIMSRA group 12 months after the operation.In both groups, troponin I increased significantly 3 h after the operation(all P<0.005), which decreased to baseline level 2 weeks later(all P>0.05). ECG showed that all the sheep had normal sinus rhythm. Pathological examinations revealed the tissue in the ablation area was fibrotic, having clear boundary with the surrounding normal tissue and no carbonization was observed 1 year later. Conclusions:Echocardiography-guided trans-right-ventricular PIMSRA produced precisely ablated myocardial tissues, reduced the IVS thickness significantly, preserved the global left ventricular function. All the sheep had normal sinus rhythm and without pericardial tamponade in 1 year follow-ups. Echocardiography-guided trans-right-ventricular PIMSRA is a safe and effective minimally invasive treatment for septal reduction therapy.