Introduction
Radiofrequency (RF) lesion metrics are influenced by underlying parameters like RF power, duration, and contact force (CF), and utilization of lesion metric indices (ablation index AI) ...is a proposed strategy to predict lesion quality. The aim of this study was to analyze the influence of underlying parameters on lesion metrics of high‐power short‐duration (HPSD) and standard RF applications using an in silico and ex vivo model.
Methods and Results
An in silico simulation study was designed to simulate HPSD and standard ablations, in which ablation parameters could systematically be varied. For each simulated ablation process (n = 5732), the corresponding AI value was calculated. HPSD and standard RF settings were then applied in a porcine ex vivo model (
n = 120 lesions). The resulting lesion metrics were compared and analyzed regarding underlying parameters. RF applications of 50 W/13 seconds, 60 W/10 seconds, 70 W/7 seconds, and 80 W/6 seconds resulted in lesion volumes not significantly different from standard RF applications (30 W/30 seconds,
P > 0.05). HPSD lesion diameters were significantly larger and lesion depths were significantly smaller (
P < 0.01) when compared with standard settings. Prolonging RF duration from 5 to 10 seconds resulted in a +27.5% increase, whereas a prolongation of RF duration from 35 to 40 seconds resulted in a +4.8% increase of AI value only. An increase of CF from 1 to 10 g resulted in a +73.0%, an increase of CF from 20 to 30 g resulted in a +10.1% increase of AI value.
Conclusion
HPSD RF applications resulted in similar lesion volumes but significantly different lesion geometries when compared with standard setting RF applications.
The Ligament of Marshall (LOM) is a remnant of the embryonic sinus venosus and the left cardinal vein, containing a combination of fat, fibrous tissue, blood vessels, muscle bundles, nerve fibers, ...and ganglia. Various muscular connections exist between the LOM and the left atrium (LA) and the coronary sinus (CS). The LOM is richly innervated by autonomic nerves, with ganglion cells distributed around it. The unique characteristics of the LOM are responsible for generating focal electrical activities and enable it to serve as a substrate for micro- and macro-reentrant circuits. This, in turn, leads to the initiation and perpetuation of atrial fibrillation (AF) and atrial tachycardia (AT). Endocardial ablation in this region does not consistently succeed due to anatomical constraints within the left lateral LA, including the presence of a thicker and longer mitral isthmus (MI), anatomical variations between the MI and epicardial structures such as the CS and vein of Marshall (VOM) and circumflex artery, and the presence of fibrofatty tissue insulating the LOM. Furthermore, epicardial ablation is challenging for inexperienced institutions because of its invasive nature. Ethanol infusion into the VOM (EI-VOM) represents an effective and safe approach that can be employed in conjunction with radiofrequency ablation to eliminate this arrhythmogenic structure.The Ligament of Marshall (LOM) is a remnant of the embryonic sinus venosus and the left cardinal vein, containing a combination of fat, fibrous tissue, blood vessels, muscle bundles, nerve fibers, and ganglia. Various muscular connections exist between the LOM and the left atrium (LA) and the coronary sinus (CS). The LOM is richly innervated by autonomic nerves, with ganglion cells distributed around it. The unique characteristics of the LOM are responsible for generating focal electrical activities and enable it to serve as a substrate for micro- and macro-reentrant circuits. This, in turn, leads to the initiation and perpetuation of atrial fibrillation (AF) and atrial tachycardia (AT). Endocardial ablation in this region does not consistently succeed due to anatomical constraints within the left lateral LA, including the presence of a thicker and longer mitral isthmus (MI), anatomical variations between the MI and epicardial structures such as the CS and vein of Marshall (VOM) and circumflex artery, and the presence of fibrofatty tissue insulating the LOM. Furthermore, epicardial ablation is challenging for inexperienced institutions because of its invasive nature. Ethanol infusion into the VOM (EI-VOM) represents an effective and safe approach that can be employed in conjunction with radiofrequency ablation to eliminate this arrhythmogenic structure.
Background: For lesion size prediction, each input parameter, including ablation energy (AE), and output parameter, such as impedance, is individually used. We hypothesize that using both parameters ...simultaneously may be more optimal.Methods and Results: Radiofrequency applications at a range of power (30–50 W), contact force (10 g and 20 g), duration (10–60 s), and catheter orientation with normal saline (NS)- or half-normal saline (HNS)-irrigation were performed in excised porcine hearts. The correlations, with lesion size of AE, absolute impedance drop (∆Imp-drop), relative impedance drop (%Imp-drop), and AE*%Imp-drop were examined. Lesion size was analyzed in 283 of 288 lesions (NS-irrigation, n=142; HNS-irrigation, n=141) without steam pops. AE*%Imp-drop consistently showed the strongest correlations with lesion maximum depth (NS-irrigation, ρ=0.91; HNS-irrigation, ρ=0.94), surface area (NS-irrigation, ρ=0.87; HNS-irrigation, ρ=0.86), and volume (NS-irrigation, ρ=0.94; HNS-irrigation, ρ=0.94) compared with the other parameters. Moreover, compared with AE alone, AE*%Imp-drop significantly improved the strength of correlation with lesion maximum depth (AE vs. AE*%Imp-drop, ρ=0.83 vs. 0.91, P<0.01), surface area (ρ=0.73 vs. 0.87, P<0.01), and volume (ρ=0.84 vs. 0.94, P<0.01) with NS-irrigation. This tendency was also observed with HNS-irrigation. Parallel catheter orientation showed a better correlation with lesion depth and volume using ∆Imp-drop, %Imp-drop, and AE*%Imp-drop than perpendicular orientation.Conclusions: The combination of input and output parameters is more optimal than each single parameter for lesion prediction.
Atrial tachycardias (ATs) are often seen in the context of atrial fibrillation (AF) ablation.
To evaluate the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density ...3-dimensional mapping.
A total of 199 ATs were mapped in 140 patients (112 male, mean age: 61.8 years); 133 (66.8%) were macroreentrant and 66 (33.2%) were scar-related reentry circuits. MB-dependent ATs were suggested by activation mapping analysis and confirmed with entrainment along the circuit.
The MB network participated in 60 (30.2%) reentrant ATs: 31 perimitral ATs (PMATs) and 29 localized reentry circuits. Of 60 MB-related ATs, 49 (81.6%) terminated with radiofrequency (RF) ablation: 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-coronary sinus (CS) junction, while 9 (15%) terminated after 2.5-5 cc of ethanol infusion inside the vein of Marshall (VOM). Of the 31 PMATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction, and 7 (22.6%) with ethanol infusion. Of the 29 localized reentry circuits using the MB, 27 (93.1%) terminated at the MB-LA junction, none at the MB-CS junction, and 2 (6.9%) after ethanol infusion. Recurrences were mostly observed after RF ablation (18 of 37 patients, 49%) compared to ethanol infusion (1 of 9 patients, 11%) (P = .06).
MB reentrant ATs accounted for up to 30.2% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or ethanol infusion inside the VOM is required to treat these arrhythmias.
Gaps in the roof line have been ascribed to epicardial conduction using the septopulmonary bundle.
We sought to evaluate the frequency of septopulmonary bundle bypass during roof line ablation, to ...describe anatomical conditions favoring this epicardial gap, and to propose an alternative strategy when present.
One hundred consecutive patients underwent atrial fibrillation ablation. A de novo roof line was created between the superior pulmonary veins. In cases of residual gaps, a floor line was created between the inferior pulmonary veins. Microtomography imaging and histological analyses of 5 human donor hearts were performed: a specific focus was made on the dome and the posterior wall.
Residual gaps were more frequent in roof lines than floor lines (33% vs 15%; P = .049). Electrogram morphologies, activation sequences, and pacing maneuvers indicated an epicardial bypass of the roof line in all cases. Conduction block was obtained in 67 roof lines and 28 floor lines, resulting in a 95% success rate of linear block, without "box" isolation. Between the superior pulmonary veins, the atrial myocardium was thicker and consistently displayed adipose tissue separating the septopulmonary bundle from the septoatrial bundle.
Epicardial conduction across the roof line is common and requires careful electrogram analysis to detect. In such cases, a floor line can be an effective alternative strategy, with clear validation criteria. Myocardial thickness and fat interposition may explain difficulties in achieving lesion transmurality during roof line ablation.
Apixaban Thromboembolism Prevention in AF Ablation
Introduction
Stroke can be a life‐threatening complication of atrial fibrillation (AF) catheter ablation. Uninterrupted warfarin treatment ...contributes to minimizing the risk of stroke complications.
Methods and Results
This was a prospective, open‐label, randomized, multicenter study assessing the safety and efficacy of apixaban for the prevention of cerebral thromboembolism complicating AF catheter ablation. Two hundred patients with drug‐resistant AF were equally assigned to take either apixaban (5 mg or 2.5 mg twice daily) or warfarin (target international normalized ratio, 2‐3) for at least 1 month before AF ablation. Neither drug regimen was interrupted throughout the operative period. Diffusion‐weighted magnetic resonance imaging was performed for all patients to detect silent cerebral infarction (SCI) after the ablation. Primary outcomes were defined as the occurrence of stroke, transient ischemic attack, SCI, or major bleeding that required intervention. The secondary outcome was minor bleeding. The groups did not statistically differ in patients’ backgrounds or procedural parameters. During AF ablation, the apixaban group required administration of more heparin to maintain an activated clotting time > 300 seconds than the warfarin group (apixaban, 14,000 ± 4,000 units; warfarin, 9,000 ± 3,000 units). Three primary outcome events occurred in each group (apixaban, 2 SCI and 1 major bleed; warfarin, 3 SCI, P = 1.00), and 3 and 4 secondary outcome events occurred in the apixaban and warfarin groups (P = 0.70), respectively.
Conclusion
Apixaban has similar safety and effectiveness to warfarin for the prevention of cerebral thromboembolism during the periprocedural period of AF ablation.
The ligament of Marshall is an epicardial structure characterized by its composition of fat, fibrous tissue, blood vessels, muscle bundles, nerve fibers, and ganglia. Its intricate network forms ...muscular connections with the coronary sinus and left atrium, alongside adjacent autonomic nerves and ganglion cells. This complexity plays a pivotal role in initiating focal electrical activities and sustaining micro- and macro-reentrant circuits, thereby contributing to the onset of atrial fibrillation and atrial tachycardia. However, endocardial ablation in this area may encounter challenges due to anatomical variations and insulation by fibrofatty tissue. Combining ethanol infusion into the vein of Marshall with radiofrequency ablation presents a promising strategy for effectively and safely eliminating this arrhythmogenic structure and terminating associated tachycardias.
Anatomic macroreentrant atrial tachycardias (MATs) are conventionally reported to depend on the cavotricuspid isthmus, the mitral isthmus, or the left atrial roof, and are commonly seen following ...catheter ablation for atrial fibrillation.
To define the precise circuits of anatomic MAT with ultrahigh-resolution mapping.
In 57 patients (mean age, 62 years; 10 female) who developed ≥1 anatomic MAT, we analyzed 88 MAT circuits including 16 peritricuspid, 42 perimitral, and 30 roof-dependent circuits, using high-density mapping and entrainment.
Of 16 peritricuspid atrial tachycardias (ATs), 8 (50.0%) showed a circuit not limited to the tricuspid annulus. However, cavotricuspid isthmus ablation terminated the tachycardia in all patients. Similarly, 26 of 42 perimitral ATs (61.9%) showed a circuit not limited to the mitral annulus, and a low-voltage zone <0.1 mV around the mitral annulus was associated with nontypical perimitral ATs (P < .0001). The practical isthmus was not in the mitral isthmus in 13 of these 26 perimitral ATs (50%). Finally, 22 of 30 roof-dependent ATs (73.3%) had a circuit not rotating around both pairs of pulmonary veins. Brief assessment of the activation direction on the posterior wall in relation to that on the septal, anterior, and lateral wall helped deduce the circuit of roof-dependent AT in 27 of 30 (90.0%). Practical isthmus was not in the roof in 8 of 22 (36.4%). Practical isthmuses mapped with the system were significantly shorter than the usual anatomic isthmuses (16.1 ± 8.2 mm vs 33.7 ± 10.4 mm) (P < .0001).
High-density mapping successfully identified the precise circuits and the practical isthmus of anatomic MATs in patients with prior atrial fibrillation ablation.
The QDOT MICRO catheter allows temperature- and flow-controlled (TFC) ablation and very-high-power short-duration (vHPSD) ablation.
The purpose of this study was to compare lesion characteristics ...between TFC/vHPSD ablation and standard power-controlled (PC) ablation.
Lesion characteristics in the right atrium, left atrium, and right ventricle (RV) of 6 sheep were compared between vHPSD (90 W/4 seconds, TC mode with 60°C target using QDOT) and standard radiofrequency settings (PC mode, 30 W/30 seconds with ThermoCool SmartTouch SF). Lesions in the left ventricle (LV) were compared, targeting 50 W for 60-second applications.
Forty-six focal atrial lesions, 50 RV focal lesions, and 12 linear lesions were created by vHPSD ablation and PC ablation in each group of 6 animals. vHPSD ablation produced significantly larger focal atrial lesions in length (8.3 6.4-9.7 mm vs 6.3 5.2-7.4 mm; P = .0002), width (6.0 5.3-6.9 mm vs 4.6 3.8-5.4 mm; P <.0001), and surface area (39.4 25.4-52.4 mm
vs 23.6 16.0-31.1 mm
; P = .0001), with superior transmurality (89.1% vs 69.6%; P = .04) compared to PC ablation. vHPSD ablation produced significantly larger RV lesions in length (7.7 7.0-8.7 mm vs 6.0 4.8-6.9 mm; P <.0001), width (6.4 5.4-7.5 mm vs 4.3 3.6-5.2 mm; P <.0001), and area (39.4 29.1-50.1 mm
vs 19.9 14.7-25.2 mm
; P <.0001) but similar volume (P = .97) with shallower lesions (2.7 2.2-3.4 mm vs 3.8 3.0-4.4 mm; P <.0001). Atrial linear lesions were more homogeneous (P = .02), with fewer gaps in each line (P = .003) with vHPSD ablation. LV focal lesions (15 TFC mode; 21 PC mode) were similar in volume and depth, but lesion size showed less deviation (P <.05) in TFC than PC mode. Fewer steam pops were observed in TFC mode (0% vs 28.6%; P = .03). Hemorrhagic rings around the lesion core were generally smaller with TFC/vHPSD ablation (P <.05).
TFC/vHPSD ablation produces larger, shallower, more homogeneous, and less hemorrhagic lesions. vHPSD Ablation produces more transmural and contiguous linear lesions compared to PC ablation. LV lesions are more homogeneous with fewer steam pops in TFC ablation.
Purpose
Clinical implication of local impedance (LI) for radiofrequency (RF) ablation has not been fully established. This study aimed to investigate this point using IntellaNav MiFi OI
TM
catheter.
...Methods
LI and generator impedance drops (ΔLI and ΔGI) were evaluated in excised porcine hearts (
N
= 16) during RF applications at a range of powers (30 and 50 W), contact forces (5–40 g), and durations (10–180 s) using perpendicular or parallel catheter orientation. Additionally, temporal LI changes were assessed.
Results
Of the 240 lesions without steam pops (92.3%), ΔLI showed better correlations with lesion surface area (
ρ
= 0.55 vs 0.36,
P
= 0.004), maximum depth (
ρ
= 0.53 vs 0.14,
P
< 0.001), and lesion volume (
ρ
= 0.64 vs 0.23,
P
< 0.001) than ΔGI. Furthermore, %LI-drop (ΔLI/initial LI) demonstrated stronger correlations with lesion surface area (
ρ
= 0.60 vs 0.55,
P
< 0.001), maximum depth (
ρ
= 0.57 vs 0.53,
P
< 0.001), and volume (
ρ
= 0.69 vs 0.64,
P
< 0.001) than ΔLI. Parallel catheter orientation improved correlation of ΔLI with lesion surface area (
ρ
= 0.63 vs 0.40,
P
= 0.015) and depth (
ρ
= 0.68 vs 0.45,
P
= 0.008) and created a larger surface lesion (36.329.2–42.7 mm
2
vs 28.821.6–34.2 mm
2
,
P
< 0.001) than the perpendicular. LI of the lesions significantly differed between baseline, immediately after RF, and 5 min after (
P
< 0.01). LI reaching plateau, larger initial LI, ΔLI, and %LI-drop, and larger RF power and longer duration were observed in pop lesions (
P
< 0.05).
Conclusions
%LI-drop demonstrated a better correlation with lesion size than ΔLI. LI may be used as an additional parameter to predict lesion size and steam pops. Temporal variation and catheter orientation should be considered to interpret LI.
