Characteristics of myocardial tissue staining and lesion creation with an infusion-needle ablation catheter for the treatment of ventricular tachycardia in humans.

BACKGROUND: Intramural substrate causing ventricular tachycardia can be targeted by radiofrequency (RF) infusion-needle catheter ablation. OBJECTIVE: The purpose of the study was to assess fluid distribution within the myocardium after needle-ablation catheter infusion and its evidence to RF lesion creation. METHODS: In 25 patients (21 (84%) male; 67 ± 9 years; 8 (32%) with ischemic cardiomyopathy) intramural ablation of ventricular tachycardia was performed with a needle catheter. Fluoroscopic images of myocardial staining patterns produced by pre-RF saline/contrast infusion were analyzed. Lesion creation was defined as tissue inexcitability to high-output needle pacing. RESULTS: Data from 155 sites were eligible for analysis. Tissue staining was evident in 111 (72%) and absent in 44 (28%). The stain shapes were variable, with average dimensions of 20 ± 10 × 8 ± 4 mm with an area of 68 ± 58 mm2. Round/oval-shaped stains were most common (62 [56%]), while multisegmented (36 [32%]) and long flat (13 [12%]) configurations were less frequent. Evidence of staining was associated with evidence of lesion creation (92/111 (83%) vs 17/44 (39%); P ≤ .0001). Contrast staining around the needle was present in 50%, usually had blurred margins, and was associated with lesion creation. When staining extended well beyond the needle, the margins were often sharp, suggesting dissection through tissue planes, and lesion creation tended to be less effective. CONCLUSION: With infusion-needle ablation, preablation injection of contrast can help confirm an intramural position and predict lesion creation. Tissue diffusion patterns vary markedly, and studies to assess its relation to tissue architecture and ablation lesion geometry warrants further investigation. The findings also have implications for the injection of therapeutic agents into the regions of scar.

Infusion Needle Radiofrequency Ablation for Treatment of Refractory Ventricular Arrhythmias.

BACKGROUND: Catheter ablation is effective for eliminating most drug-refractory ventricular arrhythmias (VA). However, a major reason for procedural failure is arrhythmia originating deep within the myocardium where it is inaccessible to conventional endocardial or epicardial approaches. Affected patients have limited therapeutic options. OBJECTIVES: The objective of this study was to assess the safety and outcome of a novel radiofrequency ablation catheter that used an extendable/retractable 27-g needle capable of targeting deep arrhythmia (intramural) substrate. METHODS: Patients who failed at least one prior catheter ablation procedure for sustained ventricular tachycardia (VT) or nonsustained VA with associated left ventricular dysfunction were enrolled at 3 centers. The target was sustained monomorphic VT in 26 patients, including 8 with recent VT storm or VT requiring intravenous medication, and 5 with incessant VA associated with ventricular dysfunction. RESULTS: Needle ablation was performed in 31 patients (median of 2 failed prior ablation procedures; 71% nonischemic heart disease). After a median of 15 needle lesions/patient, ablation abolished at least 1 inducible VT in 19 of 26 VT patients (73%), and suppressed ambient arrhythmia in 4 of 5 nonsustained arrhythmia patients. At the 6-month follow-up, 48% of patients were free of recurrent arrhythmia and another 19% were improved. Procedure-related complications included a single pericardial effusion treated with percutaneous drainage and a left ventricular pacing lead dislodgement with no deaths. CONCLUSIONS: In patients with recurrent ventricular arrhythmias refractory to medications and conventional catheter ablation, intramural needle radiofrequency ablation offers significant arrhythmia control with an acceptable procedural risk.

Irrigated Needle Ablation Creates Larger and More Transmural Ventricular Lesions Compared With Standard Unipolar Ablation in an Ovine Model.

BACKGROUND: Ventricular tachycardia recurrence can occur after ventricular tachycardia ablation because of incomplete and nontransmural ventricular lesion formation. We sought to compare the lesions made by a novel irrigated needle catheter to conventional radiofrequency lesions. METHODS AND RESULTS: Thirteen female sheep (4.6±0.7 years, 54±8 kg) were studied. In 7 sheep, 60-s radiofrequency applications were performed using an irrigated needle catheter. In 6 sheep, conventional lesions were made using a 4-mm irrigated catheter. 1.5T in vivo and high-density magnetic resonance imaging (9.4T) were performed on explanted hearts from animals receiving needle radiofrequency. Conventional lesion volume was calculated as (1/6)×π×(A×B(2)+C×D(2)/2). Needle lesion volume was measured as Σ(π×r(2))/2 with a slice thickness of 1 mm. The dimensions of all lesions were also measured on gross pathology. Additional histological analysis of the needle lesions was performed. One hundred twenty endocardial left ventricular ablation lesions (conventional, n=60; needle, n=60) were created. At necropsy, more lesions were found using needle versus conventional radiofrequency (90% versus 75%; P<0.05). Comparing needle versus conventional radiofrequency: lesion volume was larger (1030±362 versus 488±384 mm(3); P<0.001), lesion depth was increased (9.9±2.7 versus 5±2.4 mm; P<0.001), and more transmural lesions were created (62.5% versus 17%; P<0.01). Pericardial contrast injection was observed in 4 apical attempts using needle radiofrequency, however, with no adverse effects. Steam pops occurred in 3 attempts using conventional radiofrequency. CONCLUSIONS: Irrigated needle ablation is associated with more frequent, larger, deeper, and more often transmural lesions compared with conventional irrigated ablation. This technology might be of value to treat intramural or epicardial ventricular tachycardia substrates resistant to conventional ablation.