Kathy Lai-Fun Lee

Pulmonary vein isolation using transvenous catheter cryoablation for treatment of atrial fibrillation without risk of pulmonary vein stenosis.

OBJECTIVES We sought to evaluate the efficacy and safety of pulmonary vein (PV) isolation using transvenous cryoablation for the treatment of atrial fibrillation (AF). BACKGROUND Although electrical isolation of PVs with radiofrequency energy for the treatment of AF is feasible, it is associated with a significant risk of PV stenosis. Cryoablation is a new alternative therapy allowing ablation of tissue while preserving its underlying architecture. METHODS In 52 patients with paroxysmal (n = 45) or persistent (n = 7) AF, PV isolation using the CryoCor cryoablation system (CyroCor Inc., San Diego, California) with a 10F deflectable transvenous catheter was performed as guided by ostial PV potentials. Cryoablation was applied twice at each targeted site (2.5 to 5 min/application). Computed tomography (CT) of the thorax was performed at baseline and at 3 and 12 months to evaluate for PV stenosis. RESULTS All targeted PVs were completely isolated in 49 (94%) of 52 of patients. Of 152 PVs targeted, 147 (97%) were successfully isolated (mean 3.0 PVs isolated per patient). After a mean period of 12.4 +/- 5.5 months of follow-up, 37 (71%) of 52 patients had no recurrence of AF or were clinically improved, including 29 patients (56%) who had no recurrence of AF with (n = 11) or without the use of anti-arrhythmic drugs. At 3 and 12 months, the CT scan showed no evidence of PV stenosis associated with cryoablation in any patients. CONCLUSIONS Transvenous catheter cryoablation is an effective method to create PV electrical isolation for the treatment of AF. A clinically satisfactory result can be achieved in 71% of patients with AF, without the risk of PV stenosis.

New‐Onset Heart Failure After Permanent Right Ventricular Apical Pacing in Patients with Acquired High‐Grade Atrioventricular Block and Normal Left Ventricular Function

Introduction: Emerging data have suggested that right ventricular (RV) apical pacing results in progressive left ventricular (LV) dysfunction and contributes to the development of heart failure (HF). This study aimed to investigate the prevalence and clinical predictors for the development of new‐onset HF after long‐term RV apical pacing in patients with acquired atrioventricular (AV) block who require permanent pacing.

Investigation of a novel algorithm for synchronized left-ventricular pacing and ambulatory optimization of cardiac resynchronization therapy: Results of the adaptive CRT trial

BACKGROUND In patients with sinus rhythm and normal atrioventricular conduction, pacing only the left ventricle with appropriate atrioventricular delays can result in superior left ventricular and right ventricular function compared with standard biventricular (BiV) pacing. OBJECTIVE To evaluate a novel adaptive cardiac resynchronization therapy ((aCRT) algorithm for CRT pacing that provides automatic ambulatory selection between synchronized left ventricular or BiV pacing with dynamic optimization of atrioventricular and interventricular delays. METHODS Patients (n = 522) indicated for a CRT-defibrillator were randomized to aCRT vs echo-optimized BiV pacing (Echo) in a 2:1 ratio and followed at 1-, 3-, and 6-month postrandomization. RESULTS The study met all 3 noninferiority primary objectives: (1) the percentage of aCRT patients who improved in their clinical composite score at 6 months was at least as high in the aCRT arm as in the Echo arm (73.6% vs 72.5%, with a noninferiority margin of 12%; P = .0007); (2) aCRT and echo-optimized settings resulted in similar cardiac performance, as demonstrated by a high concordance correlation coefficient between aortic velocity time integrals at aCRT and Echo settings at randomization (concordance correlation coefficient = 0.93; 95% confidence interval 0.91-0.94) and at 6-month postrandomization (concordance correlation coefficient = 0.90; 95% confidence interval 0.87-0.92); and (3) aCRT did not result in inappropriate device settings. There were no significant differences between the arms with respect to heart failure events or ventricular arrhythmia episodes. Secondary end points showed similar benefit, and right-ventricular pacing was reduced by 44% in the aCRT arm. CONCLUSIONS The aCRT algorithm is safe and at least as effective as BiV pacing with comprehensive echocardiographic optimization.

Reversal of left ventricular remodeling by synchronous biventricular pacing in heart failure

Synchronous biventricular pacing is a new nonpharmacological supplemental treatment of advanced heart failure associated with electromechanical conduction delay. However, the role of pacing on left ventricular remodeling is unknown. Eleven patients with New York Heart Association Class III to IV heart failure, a left ventricular ejection fraction < 35%, and a QRS duration ≥ 140 ms received a biventricular dual chamber pacemaker. Serial echocardiography, 6‐minute hall walk, and Minnesota Living with Heart Failure quality‐of‐life (QOL) questionnaire were performed before and after up to 3 months of pacing. At 3 months there was a significant increase in fractional shortening (P < 0.001), ejection fraction (P < 0.001), and cardiac output (P < 0.05). The left ventricular end‐diastolic volume (245 ± 70 vs 185 ± 37 mL, P < 0.05), end‐systolic volume (209 ± 69 vs 140± 44 mLP < 0.05), and mitral regurgitation were reduced (P < 0.05), and diastolic filling time was lengthened (P < 0.05). There were also improvements in heart failure symptoms, an increase in 6‐minute walk distance, and a decrease in QOL scores. Synchronous biventricular pacing for 3 months was associated with hemodynamic improvements, reversal of left ventricular remodeling, and increase in left ventricular systolic function, and a decrease in secondary mitral regurgitation.

Initial Clinical Experience with an Implantable Human Atrial Defibrillator

Low energy biatrial shock is an effective means of restoring sinus rhythm in patients with atril fibrillation (AF). Ventricular proarrhythmia is avoided provided that shocks are well synchronized to R waves that are not at closely coupled intervals or preceded by long‐short cycles. Based on these principles, an implantable atrial defibrillator has been developed and was implanted in three patients with drug refractory paroxysmal AF. The device detects AF via an actively fixed right atrial and a self‐retaining coronary sinus defibrillating leads, and delivers 3/3 ms biphasic shocks up to 300 V synchronized to the R wave. The mean implant threshold (ED50) was 195V (1.8 J), and minimum voltage at conversion during follow‐up assessments at 1, 3, and 6 months were 260 V, 2.5 J, 250 V, 2.3 J, and 300 V, 3.0 J respectively. Detection of AF was 100% specific and shocks were 100% synchronized, although only a proportion of synchronized R waves were considered suitable for shock delivery primarily because of closely coupled cycles. Three patients had 9 spontaneous AF episodes. 8/9 (89%) successfully defibrillated by shocks of 260–300 V. Sedation was not used in 4 out of 9 (45%) episodes. Backup ventricular pacing was initiated by the device in 6 out of(67%) episodes. One patient had more frequent AF after lead placement, which subsided after a change of medication. There was no ventricular proarrhythmia. It is concluded that an implantable atrial defibrillator is a viable therapy for selected patients with paroxysmal AF. The device is capable of accurate AF detection, R wave synchronization and ventricular support pacing after successful defibrillation of AF.

Clinical outcomes with synchronized left ventricular pacing: analysis of the adaptive CRT trial.

BACKGROUND Acute studies have suggested that left ventricular pacing (LVP) may have benefits over biventricular pacing (BVP). The adaptive cardiac resynchronization therapy (aCRT) algorithm provides LVP synchronized to produce fusion with the intrinsic activation when the intrinsic atrioventricular (AV) interval is normal. The randomized double-blind adaptive cardiac resynchronization therapy trial demonstrated noninferiority of the aCRT algorithm compared to echocardiography-optimized BVP (control). OBJECTIVE To examine whether synchronized LVP (sLVP) resulted in better clinical outcomes. METHODS First, stratification by percent sLVP (%sLVP) and multivariate Cox proportional hazards model was used to assess the relationship between %sLVP and clinical outcomes. Second, outcomes were compared between patients in the aCRT arm (n = 318) and control patients (n = 160) stratified by intrinsic AV interval at randomization. RESULTS In the aCRT arm, %sLVP ≥50% (n = 142) was independently associated with a decreased risk of death or heart failure hospitalization (hazard ratio 0.49; 95% confidence interval 0.28-0.85; P = .012) compared with %sLVP <50% (n = 172). A greater proportion of patients with %sLVP ≥50% improved in Packers clinical composite score at 6-month (82% vs. 68%; P = .002) and 12-month (80% vs. 62%; P = .0006) follow-ups compared to controls. In the subgroup with normal AV (n = 241), there was a lower risk of death or heart failure hospitalization (hazard ratio 0.52; 95% confidence interval 0.27-0.98; P = .044) with the aCRT algorithm. A greater proportion of patients in the aCRT arm improved in the clinical composite score at 6-month (81% vs. 69%; P = .041) and 12-month (77% vs. 66%; P = .076) follow-ups compared to controls. CONCLUSIONS Higher %sLVP was independently associated with superior clinical outcomes. In patients with normal AV conduction, the aCRT algorithm provided mostly sLVP and demonstrated better clinical outcomes compared to echocardiography-optimized BVP.

Effects of temporal application parameters on lesion dimensions during Transvenous catheter cryoablation

Background: Transvenous catheter cryoablation is a novel technique for treating cardiac arrhythmias. However, the relative importance of temporal application parameters on lesion dimension and clinical efficacy has not been studied.

EFFECT OF THE IMPLANTABLE ATRIAL DEFIBRILLATOR ON THE NATURAL HISTORY OF ATRIAL FIBRILLATION

Implantable Atrial Defibrillator. Introduction: The purpose of our study was to evaluate the effect of repeated cardioversion with an implantable atrial defibrillator on the clinical outcome of patients with atrial fibrillation.

Incessant Automatic Ventricular Tachycardia Complicating Acute Coxsackie B Myocarditis

A 13-year-old girl presented with incessant ventricular tachycardia complicating acute Coxsackie B3 myocarditis. Electrophysiologic assessment revealed that the tachycardia could not be terminated, overdrive suppressed or accelerated by programmed electrical stimulation, but was transiently slowed by intravenous adenosine triphosphate and had marked spontaneous and sympathoautonomic-mediated fluctuation in the tachycardia cycle length. These features were atypical of reentry and triggered automaticity and suggested that abnormal automaticity was the likely tachycardia mechanism. Intravenous amiodarone slowed the ventricular tachycardia, but the patient eventually succumbed from rapidly progressive left ventricular failure. Postmortem pathohistologic examination confirmed the diagnosis of acute myocarditis.

A novel algorithm for individualized cardiac resynchronization therapy: Rationale and design of the adaptive cardiac resynchronization therapy trial

BACKGROUND The magnitude of benefit of cardiac resynchronization therapy (CRT) varies significantly among its recipients; approximately 30% of CRT patients do not report clinical improvement. Optimization of CRT pacing parameters can further improve cardiac function, both acutely and chronically. Echocardiographic optimization is used in clinical practice, but it is time and resource consuming. In addition, optimal settings at rest may change later with activity or cardiac remodeling. The adaptive CRT (aCRT) algorithm was designed to provide automatic ambulatory adjustment of CRT pacing configuration (left ventricular or biventricular pacing) and device delays based on periodic measurement of electrical conduction intervals. METHODS The aCRT algorithm is currently undergoing evaluation in a prospective, randomized, double-blinded, worldwide clinical trial. The trial enrolled 522 patients, who satisfied standard clinical indications for a CRT device. Within 2 weeks after the implant, the patients were randomized to aCRT versus echo-optimized biventricular pacing (Echo) settings in 2:1 ratio and followed up at 1-, 3-, 6-, and 12-month postrandomization. The noninferiority primary trial objectives at 6-month postrandomization are to demonstrate that (a) the percentage of aCRT patients who improved in their clinical composite score is at least as high as the percentage of Echo patients; (b) cardiac performance as assessed by echocardiography is similar when using aCRT settings versus echo-optimized settings; and (c) aCRT does not result in inappropriate device settings. First and last patient enrollments occurred in November 2009 and December 2010, respectively. CONCLUSIONS The safety and efficacy of the aCRT algorithm will be evaluated in this ongoing clinical trial.