Heated saline-enhanced radiofrequency ablation- New concept

Heated saline-enhanced radiofrequency ablation – New concept

We have heard of cooled saline tip radiofrequency catheter ablation for quite some time, which allows the formation of deeper lesions. Now here is intramural needle ablation using in-catheter, heated saline-enhanced radio frequency (SERF) energy. It uses convective heating to increase heat transfer and produce deeper controllable lesions at intramural targets. This is meant for ablation of ventricular tachycardia (VT) with intramural origins. So far ablations for VT have been mostly endocardial and sometimes epicardial.

The first-in-human trial had 32 subjects with refractory VT across 6 centers. These patients had drug-refractory monomorphic VT after implantable cardioverter defibrillator implantation and prior standard ablation. One or more VTs were induced and mapped during the procedure. SERF needle catheter was used to produce intramural lesions at targeted VT locations. Follow up period was 6 months in this study [1].

Median device therapies which included shock and antitachycardia pacing for VT was 45 in the 3-6 months prior to SERF ablation. Average number of ablations was 10 and average duration of ablation was 430 seconds. Acute procedural success was 97% for elimination of the clinical VT. At average follow up of 5 months ICD therapies were reduced by 89%. Complications noted were 2 periprocedural deaths due to embolic mesenteric infarct and cardiogenic shock, 2 mild strokes and a pericardial effusion treated with pericardiocentesis.

Authors concluded that intramural heated saline needle ablation showed complete acute and satisfactory mid-term control of difficult to treat VT which had recurred after drug therapy and one to five prior ablations. They suggested further study to define safety and longer term efficacy of SERF.

SERF needle electrode was inserted 6-8 mm into tissue and typically 5-20 mm large lesions were created. Excessive ablation with this system can cause heart muscle injury. Role of SERF comes from the observation that some or all of the arrhythmia substrate is intramural in the majority of scar related VTs [2]. Injection of heated saline markedly increases convective heat transfer during radiofrequency application. Lesion size increases as the duration of RF application increases and can even create transmural left ventricular lesions from an endocardial catheter [3].

Using intracardiac ultrasound to monitor catheter placement and limiting the number of lesions to those required for the targeted VT are desirable, to avoid undue myocardial damage by SERF ablation. Extensive SERF ablations have the potential risk of intramyocardial hemorrhage and cardiogenic shock [1].

References

1. Packer DL, Wilber DJ, Kapa S, Dyrda K, Nault I, Killu AM, Kanagasundram A, Richardson T, Stevenson W, Verma A, Curley M; SERF Investigators. Ablation of Refractory Ventricular Tachycardia Using Intramyocardial Needle Delivered Heated Saline-Enhanced Radiofrequency Energy: A First-in-Man Feasibility Trial. Circ Arrhythm Electrophysiol. 2022 Aug;15(8):e010347. doi: 10.1161/CIRCEP.121.010347. Epub 2022 Jul 1. PMID: 35776711; PMCID: PMC9388560.
2. Tung R, Raiman M, Liao H, Zhan X, Chung FP, Nagel R, Hu H, Jian J, Shatz DY, Besser SA, Aziz ZA, Beaser AD, Upadhyay GA, Nayak HM, Nishimura T, Xue Y, Wu S. Simultaneous Endocardial and Epicardial Delineation of 3D Reentrant Ventricular Tachycardia. J Am Coll Cardiol. 2020 Mar 3;75(8):884-897. doi: 10.1016/j.jacc.2019.12.044. PMID: 32130924.
3. Henz B, Okumura Y, Johnson S, Miller D, Curley M, Packer D. Deep ablation candidate of intra-scar circuit component: Effect of scar penetrating ablation with a novel, saline irrigated needle catheter. Heart Rhythm. 2008; 5:S364.