Characteristics and Prognostic Relevance of Ventricular Arrhythmia in Patients with Myocarditis.

Myocarditis is characterized by various clinical manifestations, with ventricular arrhythmia (VA) as a frequent symptom at initial presentation. Here, we investigated characteristics and prognostic relevance of VA in patients with myocarditis. The study population consisted of 76 patients with myocarditis, verified by biopsy and/or cardiac magnetic resonance (CMR) imaging, including 38 consecutive patients with VA (45 ± 3 years, 68% male) vs. 38 patients without VA (NVA) (38 ± 2 years, 84% male) serving as a control group. VA was monomorphic ventricular tachycardia in 55% of patients, premature ventricular complexes in 50% and ventricular fibrillation in 29%. The left ventricular ejection fraction at baseline was 47 ± 2% vs. 40 ± 3% in VA vs. NVA patients (p = 0.069). CMR showed late gadolinium enhancement more often in VA patients (94% vs. 69%; p = 0.016), incorporating 17.6 ± 1.8% vs. 8.2 ± 1.3% of myocardial mass (p < 0.001). Radiofrequency catheter ablation for VA was initially performed in nine (24%) patients, of whom five remained free from any recurrence over 24 ± 3 months. Taken together, in patients with myocarditis, reduced left ventricular ejection fraction does not predict VA occurrence but CMR shows late gadolinium enhancement more frequently and to a larger extent in VA than in NVA patients, potentially guiding catheter ablation as a reasonable treatment of VA in this population.

The impact of ultra-high-density mapping on long-term outcome after catheter ablation of ventricular tachycardia.

Ultra-high-density (UHD) mapping can improve scar area detection and fast activation mapping in patients undergoing catheter ablation of ventricular tachycardia (VT). The aim of the present study was to compare the outcome after VT ablation guided by UHD and conventional point-by-point 3D-mapping. The acute and long-term ablation outcome of 61 consecutive patients with UHD mapping (64-electrode mini-basket catheter) was compared to 61 consecutive patients with conventional point-by-point 3D-mapping using a 3.5 mm tip catheter. Patients, whose ablation was guided by UHD mapping had an improved 24-months outcome in comparison to patients with conventional mapping (cumulative incidence estimate of the combination of recurrence or disease-related death of 52.4% (95% confidence interval (CI) [36.9-65.7]; recurrence: n = 25; disease-related death: n = 4) versus 69.6% (95% CI [55.9-79.8]); recurrence: n = 31; disease-related death n = 11). In a cause-specific Cox proportional hazards model, UHD mapping (hazard ratio (HR) 0.623; 95% CI [0.390-0.995]; P = 0.048) and left ventricular ejection fraction > 30% (HR 0.485; 95% CI [0.290-0.813]; P = 0.006) were independently associated with lower rates of recurrence or disease-related death. Other procedural parameters were similar in both groups. In conclusion, UHD mapping during VT ablation was associated with fewer VT recurrences or disease-related deaths during long-term follow-up in comparison to conventional point-by-point mapping. Complication rates and other procedural parameters were similar in both groups.

Specific electrogram characteristics impact substrate ablation target area in patients with scar-related ventricular tachycardia-insights from automated ultrahigh-density mapping.

INTRODUCTION: Substrate-based catheter ablation approaches to ventricular tachycardia (VT) focus on low-voltage areas and abnormal electrograms. However, specific electrogram characteristics in sinus rhythm are not clearly defined and can be subject to variable interpretation. We analyzed the potential ablation target size using automatic abnormal electrogram detection and studied findings during substrate mapping in the VT isthmus area. METHODS AND RESULTS: Electrogram characteristics in 61 patients undergoing scar-related VT ablation using ultrahigh-density 3D-mapping with a 64-electrode mini-basket catheter were analyzed retrospectively. Forty-four complete substrate maps with a mean number of 10319 ± 889 points were acquired. Fractionated potentials detected by automated annotation and manual review were present in 43 ± 21% of the entire low-voltage area (<1.0 mV), highly fractionated potentials in 7 ± 8%, late potentials in 13 ± 15%, fractionated late potentials in 7 ± 9% and isolated late potentials in 2 ± 4%, respectively. Highly fractionated potentials (>10 ± 1 fractionations) were found in all isthmus areas of identified VT during substrate mapping, while isolated late potentials were distant from the critical isthmus area in 29%. CONCLUSION: The ablation target area varies enormously in size, depending on the definition of abnormal electrograms. Clear linking of abnormal electrograms with critical VT isthmus areas during substrate mapping remains difficult due to a lack of specificity rather than sensitivity. However, highly fractionated, low-voltage electrograms were found to be present in all critical VT isthmus sites.

Outcome of catheter ablation of non-reentrant ventricular arrhythmias in patients with and without structural heart disease.

BACKGROUND: Catheter ablation of non-reentrant, commonly termed "idiopathic" ventricular arrhythmias (VA) is highly effective in patients without structural heart disease (SHD). Meanwhile, the outcome of catheter ablation of these arrhythmias in patients with SHD remains unclear. This study sought to characterize the outcome of patients with and without SHD undergoing catheter ablation of non-reentrant VA. METHODS: In this single-centre study the acute and long-term outcome of 266 consecutive patients undergoing catheter ablation of non-reentrant VA was investigated. In 41.0% of patients a SHD was present (n = 109, 80.7% male, age 59.1 ± 14.7 years), 59.0% had no SHD (n = 157; 44.0% male, age 49.9 ± 16.5 years). RESULTS: Acute procedural success (absence of spontaneous or provoked VA at the end of procedure and within 48 h after the procedure) was achieved in 89.9% of patients with SHD vs. 94.3% without SHD (p = 0.238). During a mean follow-up of 34.7 ± 15.1 months a repeat catheter ablation was performed in 19.6% of patients with SHD vs. 13.0% without SHD (p = 0.179). Patients with dilated cardiomyopathy (DCM) were the most likely to require a repeat ablation procedure (32.0% of patients with DCM vs. 13.0% without SHD; p = 0.022). Periprocedural complications occurred in 5.5% of patients with SHD vs. 5.7% without SHD (p > 0.999). All complications were managed without sequelae. CONCLUSIONS: The outcome of catheter ablation of non-reentrant VA in patients with SHD appears good and is comparable to patients without SHD. A slightly higher rate of repeat ablations was observed in patients with DCM.

Local impedance guides catheter ablation in patients with ventricular tachycardia.

AIMS: Catheter contact and local tissue characteristics are relevant information for successful radiofrequency current (RFC)-ablation. Local impedance (LI) has been shown to reflect tissue characteristics and lesion formation during RFC-ablation. Using a novel ablation catheter incorporating three mini-electrodes, we investigated LI in relation to generator impedance (GI) in patients with ventricular tachycardia (VT) and its applicability as an indicator of effective RFC-ablation. METHODS AND RESULTS: Baseline impedance, Δimpedance during ablation and drop rate (Δimpedance/time) were analyzed for 625 RFC-applications in 28 patients with recurrent VT undergoing RFC-ablation. LI was lower in scarred (87.0 Ω [79.0-95.0]) compared to healthy myocardium (97.5 Ω ([82.75-111.50]; P = .03) while GI did not differ between scarred and healthy myocardium. ΔLI was higher (18 Ω [9.4-26.0]) for VT-terminating as compared to non-terminating RFC-ablation (ΔLI 13 Ω [8.85-18.0]; P = .03), but did not differ for ΔGI between terminating vs nonterminating RFC-ablation. Correspondingly, LI drop rate was higher for RFC-ablation terminating the VT compared with RFC-ablation not terminating the VT (0.63 Ω/s [0.52-0.76] vs 0.32 Ω [0.20-0.58]; P = .008) while there was no difference for GI drop rate. ΔLI was higher in patients with nonischemic cardiomyopathy vs patients with ischemic cardiomyopathy (16 Ω [11.0-20.0] vs 11.0 Ω [7.85-17.00]; P = .003). CONCLUSION: Our findings suggest that LI is a sensitive parameter to guide RFC-ablation in patients with VT. LI indicates differences in tissue characteristics and generally is higher in patients with nonischemic cardiomyopathy. Hence, the etiology of the underlying cardiomyopathy needs to be considered when adopting LI for monitoring catheter ablation of VT.

High-Density Mapping and Ablation of Primary Nonfocal Left Atrial Tachycardia: Characterizing a Distinct Arrhythmogenic Substrate.

OBJECTIVES: This study sought to characterize primary left atrial tachycardia (LAT) mechanisms, electrical properties and substrate using high-density mapping. BACKGROUND: Nonfocal LAT can be found in patients without prior substrate modifying interventions. METHODS: Of 223 catheter ablation procedures for LAT 15 patients (60% male, age 74 ± 6 years) had nonfocal AT and no history of LA ablation or cardiac surgery. RESULTS: AT (mean cycle length 244 ± 32 ms) were identified as macro-re-entry (12 of 15) or localized re-entry (3 of 15). High-density electroanatomical mapping (EAM, performed in 13 patients) revealed a high proportion of low voltage areas (LVA, <0.45 mV, 41 ± 22%). Anterior LVA regions were predominantly related to the macro-re-entry and directly perpetuating the re-entrant circuit in 8 patients by formation of a conductive channel (width: 14 ± 7 mm, length: 11 ± 3 mm) between the inferior pole of the scar and the mitral valve (MV) annulus with electrophysiological features of diseased tissue. A tailored anterior ablation line successfully terminated AT in 9 patients (6 dominant circuit MV dependent, 3 dominant circuit scar dependent AT), while a lateral isthmus line was performed in 2 patients. Localized re-entries were successfully targeted by local ablation. Acute successful ablation could be achieved in 14 of 15 patients leading to a freedom from any arrhythmias in 9 of 15 patients (60%) after follow-up of 343 ± 203 days. CONCLUSIONS: Patients with nonfocal left atrial tachycardia without previous iatrogenic interventions show evidence for advanced atrial myopathy. High-density mapping revealed involvement of the anterior LA and allows for an individualized ablation approach beyond strategies usually applied in consecutive AT.

Contact force facilitates the achievement of an unexcitable ablation line during pulmonary vein isolation.

AIMS: Contact force (CF) catheters provide catheter-tissue contact information to improve outcome of pulmonary vein isolation (PVI) in paroxysmal atrial fibrillation (PAF). We evaluated different target-CF values for achievement of the additional endpoint of an unexcitable ablation line. METHODS: A total of 106 patients undergoing PVI were randomized into three groups (G) (G1: target-CF 15 g, G2: target-CF 10 g, G3: CF concealed from operator). The PVI encircling line was divided into predefined sections. Excitable tissue along the PVI-line identified by high output pacing (10 V, 2 ms) was targeted for further ablation. RESULTS: Mean average CF was 17.4 ± 4.7 g (G1) vs. 12.3 ± 6.0 g (G2) vs. 11.1 ± 6.5 g (G 3) (p < 0.001). Primary unexcitable ablation lines were found in 38.6, 19.4 and 5.7% (G1, G2, G3 respectively; G1 vs. G2 p < 0.05, G1 vs. G3 p < 0.001, G2 vs. G3 ns). Additional radiofrequency (RF)-energy to achieve unexcitability was lowest in G1 (3.6 ± 3.1 kJ vs. 8.6 ± 7.2 kJ (G2) and 10.4 ± 6.7 (G3), p ≤ 0.001, G2 vs. G3 ns) with accordingly lowest additional RF applications in G1 (3.0 ± 2.6 vs. 7.0 ± 5.4 in G2 and 8.4 ± 4.0 in G3; G1 vs. G2 and G3, p < 0.001, G 2 vs. G 3 ns). Sections along ablation lines with low initial CF were most likely to reveal excitability. Single procedure success was 81.9 vs. 73.5 vs. 71.4% (G 1, 2 and 3, p = 0.6) during 437 ± 254 day follow-up. CONCLUSION: Higher tip-to-tissue CF during PVI facilitates the achievement of an unexcitable ablation line, requiring less additional RF-energy.