Peter M. Kistler

The impact of CT image integration into an electroanatomic mapping system on clinical outcomes of catheter ablation of atrial fibrillation.

Background: A detailed appreciation of left atrial/pulmonary vein (LA/PV) anatomy may be important in improving the safety and success of catheter ablation (CA) for atrial fibrillation (AF).

Myocardial Fibrosis Predicts Appropriate Device Therapy in Patients With Implantable Cardioverter-Defibrillators for Primary Prevention of Sudden Cardiac Death

OBJECTIVES The purpose of this study was to evaluate the association between regional myocardial fibrosis and ventricular arrhythmias in patients with cardiomyopathy. BACKGROUND Patients with heart failure are at risk of sudden cardiac death (SCD). Current guidelines recommend implantable cardioverter-defibrillator (ICD) devices for a subgroup based on impaired left ventricular function. A significant proportion of devices never discharge, hence a more accurate method for targeting those at risk is desirable. METHODS We prospectively enrolled 103 patients meeting criteria for ICD implantation for primary prevention of SCD. Cardiac magnetic resonance imaging was performed before device implantation. Regional fibrosis was identified with late gadolinium enhancement (LGE). RESULTS Median follow-up was 573 days (interquartile range: 379 to 863 days). The LGE identified regional fibrosis in 31 of 61 (51%) patients with nonischemic cardiomyopathy (NICM) and in all 42 patients with ischemic cardiomyopathy (ICM). There was a 29% (9 of 31) discharge rate in the NICM group with LGE compared with a 14% (6 of 42) discharge rate in the ICM group (p = NS). There were no ICD discharges in the NICM group without LGE, which was significantly lower than the rate observed in both the ICM patients (p = 0.04) and the NICM patients with LGE (p < 0.01). Left ventricular ejection fraction was similar in patients with and without device therapy (24 ± 12% vs. 26 ± 8%, p = NS) and those with or without LGE (25 ± 9% vs. 26 ± 9%, p = NS). CONCLUSIONS Patients with advanced cardiomyopathy and myocardial fibrosis demonstrated by LGE on cardiac magnetic resonance imaging have a high likelihood of appropriate ICD therapy. Correspondingly, absence of LGE may indicate a lower risk for malignant ventricular arrhythmias.

Electrophysiological and Electroanatomic Characterization of the Atria in Sinus Node Disease Evidence of Diffuse Atrial Remodeling

Background—The normal sinus pacemaker complex is an extensive structure within the right atrium. We hypothesized that patients with sinus node disease (SND) would have evidence of diffuse atrial abnormalities. Methods and Results—Sixteen patients with symptomatic SND and 16 age-matched controls were studied. The following were evaluated: effective refractory periods (ERPs) from the high and low lateral right atrium (RA), high septal RA, and distal coronary sinus (CS); conduction time along the CS and lateral RA; P-wave duration; and conduction at the crista terminalis. Electroanatomic mapping was performed to define the sinus node complex and determine regional conduction velocity, double potentials, fractionated electrograms, regional voltage, and areas of electrical silence. Patients with SND demonstrated significant increase in atrial ERP at all right atrial sites, increased atrial conduction time along the lateral RA and CS, prolongation of the P-wave duration, and greater number and duration of double potentials along the crista terminalis. Electroanatomic mapping demonstrated the sinus node complex in SND to be more often unicentric, localized to the low crista terminalis at the site of the largest residual voltage amplitude. There was significant regional conduction slowing with double potentials and fractionation associated with areas of low voltage and electrical silence (or scar). Conclusions—SND is associated with diffuse atrial remodeling characterized by structural change, conduction abnormalities, and increased right atrial refractoriness. There was a change in the nature of sinus pacemaker activity with loss of the normal multicentric pattern of activation, caudal shift of the pacemaker complex, and abnormal and circuitous conduction around lines of conduction block.

Validation of Three-Dimensional Cardiac Image Integration: Use of Integrated CT Image into Electroanatomic Mapping System to Perform Catheter Ablation of Atrial Fibrillation

Introduction: Accurate visualization of the complex left atrial (LA) anatomy and the location of an ablation catheter within the chamber is important in the success and safety of ablation for atrial fibrillation (AF). We describe the integration of CT into an electroanatomic mapping (EAM) system and its validation in patients undergoing catheter ablation for AF.

Electrophysiological and electrocardiographic characteristics of focal atrial tachycardia originating from the pulmonary veins: acute and long-term outcomes of radiofrequency ablation.

Background—The objective of this study was to describe the electrophysiological characteristics, anatomic distribution, and long-term outcome after focal ablation (RFA) of pulmonary vein (PV) atrial tachycardia (AT). Both atrial fibrillation (AF) and AT may be due to a rapidly firing focus in the PVs. Whether these represent two aspects of the same process is unknown. Methods and Results—Twenty-seven patients with 28 PV(16%) ATs of a consecutive series of 172 undergoing RFA for focal AT are reported. The mean age was 39±16 years, with symptoms for 9±14 years resistant to 1.7±0.8 medications. AT occurred spontaneously or with isoproterenol in all patients and was not inducible with PES in any. The distribution of PV ATs was right superior PV, 11; left superior PV, 11; left inferior PV, 5; and right inferior PV, 1; 26of 28 foci (93%) were ostial. RFA was successful in 28 of 28 PV ATs acutely. RFA was focal in 25 of 28, with PV isolation of a single target vein in 3. There were 4 recurrences at a mean of 3.3 months. Repeat RFA was performed in all 4 and successful in 3 of 4. All but one recurrence occurred from the same site. Long-term success was achieved in 26 of 27 (96%) patients at mean follow-up of 25±22 months. No patients have had subsequent development of AF or AT from a different site. Conclusions—PV AT has a distribution similar to PV AF, with a propensity to upper veins. However, the majority of foci are ostial, and only a small percentage occur from deep in the PV. Focal RFA is associated with high long-term success, with freedom from both AT from other sites and from AF. PV AT is a localized process and therefore may be different from PV AF.

Remodeling of Sinus Node Function in Patients With Congestive Heart Failure Reduction in Sinus Node Reserve

Background—Experimental and clinical studies have demonstrated diffuse atrial remodeling in congestive heart failure (CHF). We hypothesized that patients with CHF would demonstrate derangement of sinus node function. Methods and Results—Eighteen patients with symptomatic CHF (left ventricular ejection fraction, 26±5%) and 18 age-matched control subjects were studied. Under autonomic blockade, the following were evaluated: intrinsic sinus cycle length, corrected sinus node recovery time (CSNRT), sinoatrial conduction time, number and duration of fractionated electograms or double potentials along the crista terminalis, and location of the earliest sinus activity. Electroanatomic mapping was performed to evaluate the location and nature of the sinus node complex, to characterize sinoatrial propagation, and to evaluate conduction abnormalities and voltage amplitude along the crista terminalis. Patients with CHF demonstrated the following findings compared with age-matched control subjects: prolongation of the intrinsic sinus cycle length (P=0.005), prolongation of CSNRT (P<0.0001), caudal localization of sinus activity both during sinus rhythm (P=0.03) and after pacing (P=0.002), prolongation of sinoatrial conduction time (P=0.02), greater number (P<0.0001) and duration (P<0.0001) of fractionated electrograms or double potentials along the crista terminalis, loss of voltage amplitude along the crista terminalis (P=0.02), and abnormal and circuitous propagation of the sinus impulse. Conclusions—This study demonstrates that patients with CHF have significant sinus node remodeling characterized by anatomic and structural changes along the crista terminalis with a reduction in functional sinus node reserve. This finding may have implications for the development of clinical bradycardia in CHF and for the use of negatively chronotropic agents and pacing in this condition.

Pulmonary Vein Antral Isolation for Paroxysmal Atrial Fibrillation: Results from Long-Term Follow-Up

Long‐Term Follow‐Up After Atrial Fibrillation Ablation. Introduction: Pulmonary veins play an important role in triggering atrial fibrillation (AF). Pulmonary vein isolation (PVI) is an effective treatment for patients with paroxysmal AF. However, the late AF recurrence rate in long‐term follow‐up of circumferential PV antral isolation (PVAI) is not well documented. We sought to determine the time to recurrence of arrhythmia after PVAI, and long‐term rates of sinus rhythm after circumferential PVAI.

Focal atrial tachycardia arising from the mitral annulus: electrocardiographic and electrophysiologic characterization.

OBJECTIVES The study was done to characterize the electrocardiographic and electrophysiologic features of focal atrial tachycardia originating at the mitral annulus (MA). BACKGROUND Though the majority of left atrial tachycardias originate around the ostia of the pulmonary veins, only isolated reports have described focal tachycardia originating from the MA. METHODS Seven patients of a consecutive series of 172 patients undergoing radiofrequency ablation for focal atrial tachycardia are reported. Electrophysiologic study involved catheters positioned along the coronary sinus (CS), crista terminalis (CT), His bundle, and a mapping/ablation catheter. RESULTS All seven patients had tachycardia foci originating from the superior region of the MA in close proximity to the left fibrous trigone and mitral-aortic continuity. These foci demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P-wave morphology in the precordial leads typically showed a biphasic pattern, with an inverted component followed by an upright component. The P-wave was consistently of low amplitude in the limb leads. Earliest endocardial activity occurred at the His bundle region in all seven patients. In general, CS activation was proximal to distal, and mid-CT activation was earlier than high or low CT. Ablation was successful at the superior aspect of the MA in all patients. CONCLUSIONS The MA is an unusual but important site of origin for focal atrial tachycardia, with a propensity to be localized to the superior aspect. It can be suspected as a potential anatomic site of tachycardia origin from analysis of P-wave morphology and the atrial endocardial activation sequence map. Using mapping targeted to anatomic structures achieved a high success rate for ablation.

Maintenance of sinus rhythm with an ablation strategy in patients with atrial fibrillation is associated with a lower risk of stroke and death

Objective To investigate whether catheter ablation of atrial fibrillation (AF) reduces stroke rate or mortality. Methods An international multicentre registry was compiled from seven centres in the UK and Australia for consecutive patients undergoing catheter ablation of AF. Long-term outcomes were compared with (1) a cohort with AF treated medically in the Euro Heart Survey, and (2) a hypothetical cohort without AF, age and gender matched to the general population. Analysis of stroke and death was carried out after the first procedure (including peri-procedural events) regardless of success, on an intention-to-treat basis. Results 1273 patients, aged 58±11 years, 56% paroxysmal AF, CHADS2 score 0.7±0.9, underwent 1.8±0.9 procedures. Major complications occurred in 5.4% of procedures, including stroke/TIA in 0.7%. Freedom from AF following the last procedure was 85% (76% off antiarrhythmic drugs) for paroxysmal AF, and 72% (60% off antiarrhythmic drugs) for persistent AF. During 3.1 (1.0–9.6) years from the first procedure, freedom from AF predicted stroke-free survival on multivariate analysis (HR=0.30, CI 0.16 to 0.55, p<0.001). Rates of stroke and death were significantly lower in this cohort (both 0.5% per patient-year) compared with those treated medically in the Euro Heart Survey (2.8% and 5.3%, respectively; p<0.0001). Rates of stroke and death were no different from those of the general population (0.4% and 1.0%, respectively). Conclusion Restoration of sinus rhythm by catheter ablation of AF is associated with lower rates of stroke and death compared with patients treated medically.

Effect of Atrial Fibrillation on Atrial Thrombogenesis in Humans: Impact of Rate and Rhythm

OBJECTIVES We sought to assess the effect of atrial fibrillation (AF) on atrial thrombogenesis in humans by determining the impact of rate and rhythm. BACKGROUND Although AF is known to increase the risk of thromboembolic stroke from the left atrium (LA), the exact mechanisms remain poorly understood. METHODS We studied 55 patients with AF who underwent catheter ablation while in sinus rhythm; 20 patients were induced into AF, 20 patients were atrial paced at 150 beats/min, and 15 were control patients. Blood samples were taken from the LA, right atrium, and femoral vein at baseline and at 15 min in all 3 groups. Platelet activation (P-selectin) was measured by flow cytometry. Thrombin generation (thrombin-antithrombin [TAT] complex), endothelial dysfunction (asymmetric dimethylarginine [ADMA]), and platelet-derived inflammation (soluble CD40 ligand [sCD40L]) were measured using enzyme-linked immunosorbent assay. RESULTS Platelet activation increased significantly in both the AF (p < 0.001) and pacing (p < 0.05) groups, but decreased in control patients (p < 0.001). Thrombin generation increased specifically in the LA compared with the periphery in both the AF (p < 0.01) and pacing (p < 0.01) groups, but decreased in control patients (p < 0.001). With AF, ADMA (p < 0.01) and sCD40L (p < 0.001) levels increased significantly at all sites, but were unchanged with pacing (ADMA, p = 0.5; sCD40L, p = 0.8) or in control patients (ADMA, p = 0.6; sCD40L, p = 0.9). CONCLUSIONS Rapid atrial rates and AF in humans both result in increased platelet activation and thrombin generation. Prothrombotic activation occurs to a greater extent in the human LA compared with systemic circulation. AF additionally induces endothelial dysfunction and inflammation. These findings suggest that although rapid atrial rates increase the thrombogenic risk, AF may further potentiate this risk.