Correlation of ventricular arrhythmias with genotype in arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Although mutations of several genes are associated with arrhythmogenic right ventricular cardiomyopathy (ARVC), the exact correlation between genotype and ventricular arrhythmia features remains unclear. This study was aimed to examine the possible association of the 9 known genes of ARVC with clinical and electrophysiological characteristics. METHODS AND RESULTS: Ninety subjects diagnosed with ARVC who underwent electrophysiological study were recruited for screening the 9 known ARVC-causing genes. A total of 53 mutations were identified in 57 (63%) subjects. Mutation carriers had more frequent clinical ventricular tachycardia (VT; 89% versus 55%; P<0.001) and negative T waves in V1 to V3 (61% versus 33%; P=0.016). Subjects with plakophilin-2 (PKP2) mutations also had more frequent VT than those without mutations in PKP2. Comparison between subjects with multiple and single mutations showed that syncope occurred more often in the former group (58% versus 24%; P=0.018). VT was significantly more often induced in mutation carriers compared with noncarriers (75% versus 39%; P=0.001), as well as in PKP2 mutation carriers compared with subjects without PKP2 mutations (80% versus 48%; P=0.002). Induced VT with a rate ≥ 200 bpm was more often documented in mutation carriers (88% versus 54%; P=0.013), as well as in PKP2 mutation carriers (91% versus 67%; P=0.041). CONCLUSIONS: Pathogenic gene mutations were found in nearly two thirds of subjects diagnosed with ARVC. Mutation carriers, especially PKP2, had a higher proportion of a history of VT and more inducible fast VT.

Comparison of operator radiation exposure during coronary sinus catheter placement via the femoral or jugular vein approach.

AIMS: To evaluate and compare operator radiation exposure during the catheter placement in the coronary sinus via the femoral vein with a steerable catheter or the jugular vein with a fixed curve catheter. METHODS AND RESULTS: A total of 156 patients undergoing electrophysiological study or radiofrequency catheter ablation were prospectively assigned in a random fashion to either the femoral vein access (FVA) with a steerable curve deca-polar catheter (n= 80) or the jugular vein access (JVA) with a fixed curve deca-polar catheter (n = 76). All the catheterization procedures were performed by the same operator who had extensive experience in both accesses. Operator radiation exposure was measured with an electronic radiation dosimeter attached to the breast pocket of the operator on the outside of the lead apron and estimates of the ambient dose equivalent were derived. The operator radiation exposure was reduced significantly by using the FVA compared with the JVA (1.8 ± 1.3 vs. 8.6 ± 6.5 µSv; P < 0.001). The fluoroscopy time (62.7 ± 45.8 vs. 61.9 ± 46.5 s; P = NS) and dose-area product (3.2 ± 2.3 vs. 3.1 ± 2.1 Gy cm(2); P = NS) were not statistically different. CONCLUSION: Operator radiation exposure can be significantly reduced by using the FVA approach with a steerable curve catheter compared with the JVA approach with a fixed curve catheter, without increasing the fluoroscopy time and dose-area product.

Organized left atrial tachyarrhythmia during stepwise linear ablation for atrial fibrillation.

INTRODUCTION: This study attempted to delineate the mechanism of organized left atrial tachyarrhythmia (AT) during stepwise linear ablation for atrial fibrillation (AF) using noncontact mapping. METHODS AND RESULTS: Eighty patients in whom organized ATs developed or induced during stepwise linear ablation for AF were enrolled. Left atrial (LA) activation during ATs was mapped using noncontact mapping. Radiofrequency (RF) energy was delivered to the earliest activation site or narrowest part of the reentrant circuit of ATs. A total of 146 ATs were mapped. Four ATs were characterized as a focal mechanism (cycle length (CL): 225 +/- 49 ms). A macroreentrant mechanism was confirmed in the remaining 142 ATs. LA activation time accounted for 100% of CL (205 +/- 37 ms). All 142 ATs used the conduction gaps in the basic figure-7 lesion line. There were three types of circuits classified based on the gap location. Type I (n = 68) used gaps at the ridge between left atrial appendage (LAA) and left superior pulmonary vein (LSPV). Type II (n = 50) used gaps on the LA roof. Type III (n = 24) passed through gaps in the mitral isthmus. Ablation at these gaps eliminated 130 ATs. During the follow-up period of 16.2 +/- 6.7 months, 82.5% of the 80 patients were in sinus rhythm. CONCLUSION: The majority of left ATs developed during stepwise linear ablation for AF are macroreentrant through conduction gaps in the figure-7 lesion line, especially at the LAA-LSPV ridge. Noncontact activation mapping can identify these gaps accurately and quickly to target effective catheter ablation.

Clinical experience with a single catheter for mapping and ablation of pulmonary vein ostium.

INTRODUCTION: The aim of this single center study is to evaluate the safety and the efficacy of performing pulmonary vein isolation (PVI) using a single high-density mesh ablator (HDMA) catheter. METHODS: A total of 17 consecutive patients with paroxysmal (10 patients) or persistent atrial fibrillation (7 patients) and no heart disease were enrolled. A single transseptal puncture was performed and the HDMA was placed at each PV ostium identified with anatomic and electrophysiological mapping. Pulsed radiofrequency (RF) energy was delivered at the targeted temperature of 58 degrees C with maximum power of 80 watts. No other ablation system was utilized. The primary objective of the study was acute isolation of the targeted PV, and the secondary objective was clinical efficacy and safety of PVI with HDMA for atrial fibrillation (AF) prevention. Patients were followed at intervals of 1, 3, 6, and 12 months. RESULTS: PVI was attempted with HDMA in 67/67 PVs. [Correction made after online publication October 27, 2008: PVs changed from 6/67 to 67/67] Acute success rate were: 100% (16/16) for left superior PV, 100% (16/16) for left inferior PV, 100% (17/17) for right superior PV, 100% (1/1) for left common trunk and 47% (8/17) for right inferior PV. Total procedure time was 200 +/- 36 minutes (range 130-240 minutes) and total fluoroscopy time was 42 +/- 18 minutes (range 23-75 minutes). During a mean follow-up of 11 +/- 4 months, 64% of patients remained in sinus rhythm (8/10 paroxysmal AF and 3/7 for persistent AF). No complications occurred either acutely or at follow-up. CONCLUSIONS: PV isolation with HDMA is feasible and safe. The midterm efficacy in maintaining sinus rhythm is higher in paroxysmal than in persistent patients.

Accelerometer-derived time intervals during various pacing modes in patients with biventricular pacemakers: comparison with normals.

INTRODUCTION: Changes due to biventricular pacing have been documented by shortening of QRS duration and echocardiography. Compared to normal ventricular activation, the presence of left bundle branch block (LBBB) results in a significant change in cardiac cycle time intervals. Some of these have been used to quantify the underlying cardiac dyssynchrony, assess the effects of biventricular pacing, and guide programming of ventricular pacing devices. This study evaluates a simple noninvasive method using accelerometers attached to the skin to measure cardiac time intervals in biventricularly paced patients. METHODS: Ten patients with biventricular pacemakers previously implanted for congestive heart failure were paced in the AAI mode, then in atrioventricular (AV) sequential mode from the right and left ventricles followed by biventricular pacing. Simultaneous recordings were obtained by 2D, Doppler echocardiography as well as by accelerometers. Similar recordings were obtained from 10 gender, aged matched, normal controls during sinus rhythm. RESULTS: Compared to normals, heart failure patients paced in AAI mode had prolonged isovolumetric contraction time (IVCT), shorter ventricular ejection time (LVET), and prolonged isovolumetric relaxation (IVRT). With biventricular pacing the IVCT decreased, but the LVET and IVRT did not change significantly. There was excellent correlation between the echo and accelerometer-measured intervals. CONCLUSIONS: Shortening of the IVCT measured by an accelerometer is a consistent time interval change due to biventricular pacing that probably reflects more rapid acceleration of left ventricular ejection. The accelerometer may be useful to assess immediate efficacy of biventricular pacing during device implantation and optimize programmable time intervals such as AV and interventricular (VV) delays.

Stepwise linear approach to catheter ablation of atrial fibrillation.

BACKGROUND: This study attempted to convert atrial fibrillation (AF) to sinus rhythm using a stepwise linear catheter ablation approach. METHODS: One hundred and ninety-six patients (43 with persistent AF) were enrolled in the study. A multiple electrode array was used for anatomical navigation and activation mapping. Continuously incremental stimulation was used to induce AF if spontaneous AF was not present. Stepwise linear ablation was applied until AF was converted to sinus rhythm or atypical atrial flutter (AAFL) or atrial tachycardia (AT). The stepwise approach initially utilized a figure-7 lesion line between the right and left superior pulmonary vein on the roof of the left atrium and then extended along the ridge between the left appendage and the left pulmonary veins until the mitral valve annulus, as the primary lesions. If AF still persisted, high-frequency potentials in the inferior left atrium, coronary sinus, or right atrium were targeted. Noninducibility of AF was used as the end point. RESULTS: AF was converted to sinus rhythm in 81.6% of patients (90.8% of paroxysmal and 51.1% of persistent AF, P<.01). The remainders of patients were converted to AAFL or AT. AF was terminated after ablation in right atrium in 7 patients. During an 18.2+/-7.3 month follow-up, 88.3% of patients were free of atrial tachyarrhythmias without medication, 9.7% of patients had refractory AAFL/AT, and only 2.1% of patients had paroxysmal AF. CONCLUSION: Stepwise linear ablation is effective in converting AF to sinus rhythm and the figure-7 lesion line should be the basic lesion. Right atrium ablation is necessary in some patients.

Radiofrequency ablation of the ventricular tachycardia with arrhythmogenic right ventricular cardiomyopathy using non-contact mapping.

BACKGROUND: Intracardiac non-contact mapping provides a rapid and accurate isopotential mapping that facilitates catheter ablation of the ventricular tachyarrhythmias in arrhythmogenic right ventricular cardiomyopathy (ARVC). METHODS: Thirty-two consecutive patients (26 men and 6 women, mean 37.2 +/- 13.8 years) were treated with ablation. Fourteen patients had a history of syncope/pre-syncope. Two patients had an implantable cardiac defibrillator (ICD) previously implanted. RESULTS: There were 67 ventricular tachycardias (VTs) induced in the 32 patients. The average VT rate was 210 +/- 32.2 (130-310) bpm. There were 42 episodes of VT that had a heart rate > or =200 bpm and 24 of the 32 patients (75%) had > or =2 morphologies of VT. Regional ablation was applied by targeting the earliest VT activation sites under the guidance of non-contact mapping. Acute success was achieved in 84.4% (27/32) patients, and significant improvement was seen in 15.6% (5/32) patients as evidenced by a slower rate of VT. None of the patients experienced syncope/pre-syncope or sudden death during the 28.6 +/- 16 (9-72) month follow-up. There were no complications of the procedure. At the end of follow-up, 81.3% of the patients were free of VT without medication while the rest of the patients achieved a modified success. CONCLUSIONS: The rapid ventricular tachyarrhythmias in ARVC patients can be abolished or improved significantly by regional RF catheter ablation under the guidance of non-contact mapping. There was no sudden cardiac arrest or death in those patients without ICD implantation. Delayed efficacy may occur in some patients after ablation.

A novel mesh electrode catheter for mapping and radiofrequency delivery at the left atrium-pulmonary vein junction: a single-catheter approach to pulmonary vein antrum isolation.

BACKGROUND: Electrical isolation of pulmonary veins (PV) by radiofrequency (RF) ablation is often performed in patients with atrial fibrillation (AF). Current catheter technology usually requires the use of a multielectrode catheter for mapping in addition to the ablation catheter. PURPOSE: We evaluated the feasibility and safety of using a single, expandable electrode catheter (MESH) to map and to electrically isolate the PV. METHODS AND RESULTS: Nineteen closed-chest mongrel dogs, weighing 23-35 kg, were studied under general anesthesia. Intracardiac echocardiography (ICE) was used to guide transseptal puncture and to assess PV dimensions and contact of the MESH with PV ostia. ICE and angiography of RSPV were obtained before and after ablation, and prior to sacrifice at 7-99 days. An 11.5 Fr steerable MESH was advanced and deployed at the ostium of the RSPV. Recordings were obtained via the 36 electrodes comprising the MESH. For circumferential ablation, RF current was delivered at a target temperature of 62-65 degrees C (4 thermocouples) and maximum power of 70-100 W for 180 to 300 seconds. Each animal received 1-4 RF applications. Entrance conduction block was obtained in 13/19 treated RSPVs. Pathological examination confirmed circumferential and transmural lesions in 13 of 19 RSPV. LA mural thrombus was present in 3 animals. There was no significant PV stenosis. CONCLUSION: Based on this canine model, a new expandable MESH catheter may safely be used for mapping and for PV antrum isolation. This approach may decrease procedure time without compromising success rate in patients undergoing AF ablation.

Coronary sinus and fossa ovalis ablation: effect on interatrial conduction and atrial fibrillation.

BACKGROUND: Interatrial conduction occurs via discrete pathways along the coronary sinus musculature, fossa ovalis region, and Bachman's bundle. We assessed the feasibility of altering interatrial conduction by selectively ablating two of these conduction pathways using a novel mesh electrode ablation catheter. METHODS: Circular radiofrequency energy catheter ablation lesions were created in the proximal coronary sinus in four dogs and in both the fossa ovalis and the proximal coronary sinus regions in seven pigs. Interatrial conduction was assessed by analyzing intracardiac electrogram and noncontact isopotential mapping data. Inducibility of atrial fibrillation was assessed before and after ablation (in six pigs). RESULTS: Ablation lesions in the proximal coronary sinus eliminated interatrial conduction along the coronary sinus musculature in four dogs and five of seven pigs. Ablation lesions in the fossa ovalis region eliminated interatrial conduction via midseptal pathways in six of seven pigs. Atrial fibrillation, inducible in five of seven pigs at baseline, was rendered noninducible in all five. There was no adverse effect on AV nodal conduction. CONCLUSIONS: (1) Using a novel mesh electrode ablation catheter, we were able to ablate interatrial conduction pathways along the proximal coronary sinus and fossa ovalis regions. (2) This altered interatrial conduction and altered atrial fibrillation inducibility and maintenance. (3) Catheter ablation of interatrial conduction pathways may be useful in the therapy of atrial fibrillation.

Assessment of myocardial lesion size during in vitro radio frequency catheter ablation.

We report our experience with a system that utilizes changes in several biophysical characteristics of cardiac tissue to determine lesion formation and to estimate lesion size both on and off-line in vitro during radio frequency (RF) energy delivery. We analyzed the reactive and resistive components of tissue impedance and tracked the change of phase angle during RF ablation. We correlated the amount of tissue damage with these and other biophysical parameters and compared them with off-line analysis. We found that there are irreversible changes in the reactive and resistive components of impedance that occurred during tissue ablation. The irreversible changes of these components are greater in magnitude, and correlate better with the size of lesions than that of impedance alone that is currently used. Numerically, the best single on-line and off-line correlation for combined perpendicular and parallel electrode orientation was with phase angle. On-line and off-line capacitance and susceptance correlations were essentially similar suggesting that they may be useful as lesion size predictors, given these parameter's persistent change without temperature sensitivity. This study indicates that it is technically feasible to assess lesion formation using biophysical parameters.