Cardiology Department, Westmead Hospital (P.C.Q., M.A.B., V.T.T., J.L., A.T., S.P.T.), University of Sydney, Australia.
Sydney Medical School (P.C.Q., A.T., S.P.T.), University of Sydney, Australia.
Circ Arrhythm Electrophysiol. 2020 May;13(5):e008251. doi: 10.1161/CIRCEP.119.008251. Epub 2020 Apr 16.
Radiofrequency ablation depth can be inadequate to reach intramural or epicardial substrate, and energy delivery in the pericardium is limited by penetration through epicardial fat and coronary anatomy. We hypothesized that open irrigated microwave catheter ablation can create deep myocardial lesions endocardially and epicardially though fat while acutely sparing nearby the coronary arteries.
In-house designed and constructed irrigated microwave catheters were tested in in vitro phantom models and in 15 sheep. Endocardial ablations were performed at 140 to 180 W for 4 minutes; epicardial ablations via subxiphoid access were performed at 90 to 100 W for 4 minutes at sites near coronary arteries.
Epicardial ablations at 90 to 100 W produced mean lesion depth of 10±4 mm, width 18±10 mm, and length 29±8 mm through median epicardial fat thickness of 1.2 mm. Endocardial ablations at 180 W reached depths of 10.7±3.3 mm, width of 16.6±5 mm, and length of 20±5 mm. Acute coronary occlusion or spasm was not observed at a median separation distance of 2.7 mm (IQR, 1.2-3.4 mm). Saline electrodes recorded unipolar and bipolar electrograms; microwave ablation caused reductions in voltage and changes in electrogram morphology with loss of pace-capture. In vitro models demonstrated the heat sink effect of coronary flow, as well as preferential microwave coupling to myocardium and blood as opposed to lung and epicardial fat phantoms.
Irrigated microwave catheter ablation may be an effective ablation modality for deep ventricular lesion creation with capacity for fat penetration and sparing of nearby coronary arteries because of cooling endoluminal flow. Clinical translation could improve the treatment of ventricular tachycardia arising from mid myocardial or epicardial substrates.
射频消融的深度可能不足以到达心壁内或心外膜下的基质，而心外膜脂肪和冠状动脉解剖结构限制了能量在心包内的传递。我们假设开放式灌流微波导管消融可以在心内膜和心外膜上通过脂肪层产生深部心肌损伤，同时急性地保护附近的冠状动脉。
我们设计并制作了内部的灌流微波导管，在体外模型和 15 只绵羊中进行了测试。心内膜消融在 140 至 180 W 下进行 4 分钟；经剑突下途径进行心外膜消融，在靠近冠状动脉的部位，在 90 至 100 W 下进行 4 分钟。
在 90 至 100 W 的心外膜消融产生了 10±4 mm 的平均损伤深度、18±10 mm 的宽度和 29±8 mm 的长度，通过 1.2 mm 的中值心外膜脂肪厚度。在 180 W 下心内膜消融达到了 10.7±3.3 mm 的深度、16.6±5 mm 的宽度和 20±5 mm 的长度。在 2.7 mm 的中位数分离距离（IQR，1.2-3.4 mm）处未观察到急性冠状动脉闭塞或痉挛。盐水电极记录了单极和双极电图；微波消融导致电压降低，并改变了电图形态，失去了起搏捕获。体外模型证明了冠状动脉血流的热沉效应，以及微波与心肌和血液的优先耦合，而不是与肺和心外膜脂肪的耦合。
灌流微波导管消融可能是一种有效的消融方式，可以在心内膜和心外膜上产生深部心室损伤，穿透脂肪层，并保护附近的冠状动脉，因为它可以冷却管腔内的血流。临床转化可以改善治疗源于中层心肌或心外膜基质的室性心动过速。
