Ablation of Refractory Ventricular Tachycardia Using Intramyocardial Needle Delivered Heated Saline-Enhanced Radiofrequency Energy: A First-in-Man Feasibility Trial

Abstract

Background: Ablation of ventricular tachycardia (VT) is limited by the inability to create penetrating lesions to reach intramyocardial origins. Intramural needle ablation using in-catheter, heated saline-enhanced radio frequency (SERF) energy uses convective heating to increase heat transfer and produce deeper, controllable lesions at intramural targets. This first-in-human trial was designed to evaluate the safety and efficacy of SERF needle ablation in patients with refractory VT.

Methods: Thirty-two subjects from 6 centers underwent needle electrode ablation. Each had recurrent drug-refractory monomorphic VT after implantable cardioverter defibrillator implantation and prior standard ablation. During the SERF study procedure, one or more VTs were induced and mapped. The SERF needle catheter was used to create intramural lesions at targeted VT site(s). Acute procedural success was defined as noninducibility of the clinical VT after the procedure. Patients underwent follow-up at 30 days, and 3 and 6 months, with implantable cardioverter defibrillator interrogation at follow-up to determine VT recurrence.

Results: These refractory VT patients (91% male, 66±10 years, ejection fraction 35±11%; 56% ischemic, and 44% nonischemic) had a median of 45 device therapies (shock/antitachycardia pacing) for VT in the 3 to 6 months pre-SERF ablation. The study catheter was used to deliver an average of 10±5 lesions per case, with an average of 430±295 seconds of radiofrequency time, 122±65 minute of catheter use time, and a procedural duration of 4.3±1.3 hours. Acute procedural success was 97% for eliminating the clinical VT. At average follow-up of 5 months (n=32), device therapies were reduced by 89%. Complications included 2 periprocedural deaths: an embolic mesenteric infarct and cardiogenic shock, 2 mild strokes, and a pericardial effusion treated with pericardiocentesis (n=1).

Conclusions: Intramural heated saline needle ablation showed complete acute and satisfactory mid-term control of difficult VTs failing 1 to 5 prior ablations and drug therapy. Further study is warranted to define safety and longer-term efficacy.

Registration: URL: https://www.

Clinicaltrials: gov; Unique Identifier: NCT03628534 and NCT02994446.

Keywords: catheter; heating; pericardial effusion; shock, cardiogenic; tachycardia, ventricular.

Figure 1.

SERF Needle Electrode and Ablation Generator System. The deflectable catheter (Panel A) contains a needle that can be extended to 4 or 8 mm depths. Panel B show the ablation system console with monitoring utilities. Panel C shows the range of programmable settings for heated needle energy delivery.

Figure 2.

Lesion Creation with Standard RF and SERF Heated Saline Ablations. Panel A shows RF catheter tip/tissue contact and a representative endocardial surface lesion using a standard catheter design. Panel B is a rendition showing the positioning of the SERF catheter along with the needle extension into the myocardium. Heated saline is injected through side holes into the tissue, markedly increasing convective heating (orange arrows) during RF application to the needle. Panel C shows a representative spectrum of needle ablation lesions with size and depth of extension to the mid and epicardial myocardium from a previous animal model. [31, 32] [29] [33] [–30]

Figure 3

A patient with recurrent VT due to nonischemic cardiomyopathy had 4 prior ablation procedures, with the last procedure using both endocardial and epicardial approaches. Panel A shows a pre-procedural CT registered with an electroanatomic endocardial activation map of VT. In the CT, green areas indicate thin regions of likely scar whose borders define a potential intramural channel (white rectangle). The activation map of VT (red earliest) shows an area of focal endocardial break out (earliest ventricular activation) overlying this channel. Within this region several areas of fractionated activity were present. The orange markers are ablation lesion sites. Following ablation, VT was no longer inducible. B. Endocardial voltage map suggested a large region of scar. Needle lesion sites are identified by the orange markers. Purple indicates electrogram amplitude > 1.5 mV.

Figure 3

A patient with recurrent VT due to nonischemic cardiomyopathy had 4 prior ablation procedures, with the last procedure using both endocardial and epicardial approaches. Panel A shows a pre-procedural CT registered with an electroanatomic endocardial activation map of VT. In the CT, green areas indicate thin regions of likely scar whose borders define a potential intramural channel (white rectangle). The activation map of VT (red earliest) shows an area of focal endocardial break out (earliest ventricular activation) overlying this channel. Within this region several areas of fractionated activity were present. The orange markers are ablation lesion sites. Following ablation, VT was no longer inducible. B. Endocardial voltage map suggested a large region of scar. Needle lesion sites are identified by the orange markers. Purple indicates electrogram amplitude > 1.5 mV.

Figure 4.

Mapping and Intracardiac Ultrasound Imaging from a patient with prior infero-posterior myocardial infarction and recurrent VT that had failed to be controlled by prior ablation procedures. Panel A shows the activation map of the targeted VT. Panel B shows the site of ablative lesions. Panel C shows a pre-ablation ICE image of the catheter tip/issue positioning and the inserted needle into the underlying myocardium. Panel D show the evolving ablation lesion indicated by the increasing contrast and intensity of the local tissue seen on ICE. Five needle ablation lesions were applied at the endocardial break out region and abolished this inducible VT, which remained absent during 6 month follow-up.

Figure 5.

Characteristics of Needle Ablation of VT. A shows the number of energy deliveries at each depth. B shows the number of deliveries at each ablation setting seen in Table 2. C shows an LV polar map indicating the anatomic distribution of energy deliveries in all patients.

Figure 5.

Characteristics of Needle Ablation of VT. A shows the number of energy deliveries at each depth. B shows the number of deliveries at each ablation setting seen in Table 2. C shows an LV polar map indicating the anatomic distribution of energy deliveries in all patients.

Figure 5.

Characteristics of Needle Ablation of VT. A shows the number of energy deliveries at each depth. B shows the number of deliveries at each ablation setting seen in Table 2. C shows an LV polar map indicating the anatomic distribution of energy deliveries in all patients.

Figure 6.

Pre- and Post-Procedure VT Occurrences, and ICD/ ATP Therapies Under Both Circumstances. The blue bars indicate the pre-ablation frequencies of ICD shocks and ATP, while the green bars show the recurrences of the clinical events after ablation. ICD/ATP therapies were totally eliminated in 50% of all patients; there was a more than 90% reduction in 61% and more than 75% reduction in 78% of all patients, respectively. The spread in the standard deviation described on page 11 reflects the observation that several patients had ongoing ATPs, although this was seen in only 3 patients.