[Show abstract][Hide abstract] ABSTRACT: Right ventricular apical (RVA) pacing can induce left ventricular (LV) dyssynchrony and dysfunction. In this article, we describe the prevalence, clinical characteristics, and outcome in a subset of patients with unrecognized LV apical akinetic aneurysmatic area associated with permanent RVA pacing as potential causes of heart failure (HF) and/or ventricular tachyarrhythmias (VT).
We retrospectively studied 220 patients with permanent RVA pacing and no pre-existing structural heart disease in our follow-up clinic for high-degree atrioventricular block. Patients who presented with new-onset HF, chest pain, or VT following RVA pacing were evaluated by echocardiogram and cardiac catheterization. RVA pacing-induced LV apical akinetic aneurysmatic area was diagnosed in the absence of significant coronary artery disease by left ventriculogram. After a mean 8.8 ± 6.3 years, eight patients (3.6%) had LV apical akinetic aneurysmatic area. Of those with LV apical akinetic aneurysmatic area, four patients presented with or died of VT. There was no evidence of LV apical akinetic aneurysmatic area on echocardiogram or left ventriculogram in the remaining 212 patients. The four patients with LV apical akinetic aneurysmatic area and HF underwent cardiac resynchronization therapy: in all cases LV ejection fraction improved (from 33 ± 6 to 47 ± 10%, P = 0.03), and LV apical akinetic aneurysmatic area resolved in two.
Permanent RVA pacing for high-degree atrioventricular block is associated with LV apical akinetic aneurysmatic area. This condition was associated with a high incidence of VT and cardiovascular complication, but was possibly reversible with cardiac resynchronization therapy.
[Show abstract][Hide abstract] ABSTRACT: We report a case of successful transvenous, catheter-based, cavotricuspid isthmus ablation for treatment of atrial flutter using microwave energy. Microwave energy was delivered at 900–930 MHz using 21 W of power. Bidirectional cavotricuspid isthmus conduction block was achieved by microwave ablation without any patient discomfort or complication during the procedure. Our initial experience suggests that transcatheter microwave ablation is feasible for the cure of typical atrial flutter.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this research was to investigate the effect of using rate-adaptive pacing and atrioventricular interval (AVI) adaptation on exercise performance during cardiac resynchronization therapy (CRT).
The potential incremental benefits of using rate-adaptive pacing and AVI adaptation with CRT during exercise have not been studied.
We studied 20 patients with heart failure, chronotropic incompetence (<85% age-predicted heart rate [AP-HR] and <80% HR reserve), and implanted with CRT. All patients underwent a cardiopulmonary exercise treadmill test using DDD mode with fixed AVI (DDD-OFF), DDD mode with adaptive AVI on (DDD-ON), and DDDR mode with adaptive AVI on (DDDR-ON) to measure metabolic equivalents (METs) and peak oxygen consumption (VO2max).
During DDD-OFF mode, not all patients reached 85% AP-HR during exercise, and 55% of patients had <70% AP-HR. Compared to patients with >70% AP-HR, patients with <70% AP-HR had significantly lower baseline HR (66 +/- 3 beats/min vs. 80 +/- 5 beats/min, p = 0.015) and percentage HR reserve (27 +/- 5% vs. 48 +/- 6%, p = 0.006). In patients with <70% AP-HR, DDDR-ON mode increased peak exercise HR, exercise time, METs, and VO2max compared with DDD-OFF and DDD-ON modes (p < 0.05), without a significant difference between DDD-OFF and DDD-ON modes. In contrast, there were no significant differences in peak exercise HR, exercise time, METs, and VO2max among the three pacing modes in patients with >70% AP-HR. The percentage HR changes during exercise positively correlated with exercise time (r = 0.67, p < 0.001), METs (r = 0.56, p < 0.001), and VO2max (r = 0.55, p < 0.001).
In heart failure patients with severe chronotropic incompetence as defined by failure to achieve >70% AP-HR, appropriate use of rate-adaptive pacing with CRT provides incremental benefit on exercise capacity during exercise.
Preview · Article · Dec 2005 · Journal of the American College of Cardiology
[Show abstract][Hide abstract] ABSTRACT: Data on the phenotypical pattern and natural history of hypertrophic cardiomyopathy in Chinese patients are very limited. The purpose of this study was to describe the clinical characteristics of and long-term outcome in Chinese patients with hypertrophic cardiomyopathy.
We evaluated 118 Chinese patients (62 male) who were diagnosed with hypertrophic cardiomyopathy at Queen Mary Hospital from 1973 to 2002. Diagnosis was based on the demonstration of left ventricular hypertrophy (wall thickness > or =15 mm during diastole), either in a specific region or with diffuse distribution, using echocardiography or magnetic resonance imaging. Clinical predictors of major cardiovascular events related to hypertrophic cardiomyopathy (cardiovascular death, potentially fatal cardiac arrhythmia, and refractory heart failure requiring cardiac transplantation or percutaneous alcohol septal ablation) were evaluated with univariate and multivariate Cox proportional hazards regression models.
The mean (+/- SD) age at presentation was 54 +/- 18 years. During a mean follow-up of 5.8 +/- 4.3 years (range, 1 to 29 years) from presentation, major cardiovascular events related to hypertrophic cardiomyopathy occurred in 19 patients (16%), including 9 deaths. Annual cardiovascular mortality was 1.6%. Fifty-five patients (47%) had one or more cardiovascular complications related to hypertrophic cardiomyopathy, of which atrial fibrillation was the most common (35%, n = 41). The most common type of hypertrophic cardiomyopathy was the apical variant (41%, n = 49). In multivariate analysis, female sex was the only independent predictor of major cardiovascular events related to hypertrophic cardiomyopathy (hazard ratio = 5.86; 95% confidence interval: 1.77 to 7.21; P = 0.007).
Hypertrophic cardiomyopathy in Chinese patients is characterized by late onset of presentation, a high incidence of the apical form of the condition, and adverse clinical outcome in female patients, which suggest a different phenotypical pattern than in white patients.
No preview · Article · Feb 2004 · The American Journal of Medicine
[Show abstract][Hide abstract] ABSTRACT: We describe a case of atrial tachycardia originating from an epicardial site with a venous connection between the left superior pulmonary vein (LSPV) and superior vena cava (SVC). Initial endocardial mapping with multiple electrodes catheters demonstrated early endocardial activation at both the SVC and LSPV. However, radiofrequency applications at the SVC failed to terminate the atrial tachycardia. With three-dimensional electroanatomic mapping, the earliest endocardial activation was found to be in the left atrial appendage (LAA). However, radiofrequency energy applications at multiple sites in the LAA resulted in only transient termination of the tachycardia. A left atrial angiogram demonstrated a venous connection between the LSPV and SVC, overlying the LAA. An application of radiofrequency energy with a saline-irrigated ablation catheter delivered at the earliest activation site in the LAA terminated the tachycardia. The tachycardia did not recur during 18-month follow-up.(J Cardiovasc Electrophysiol, Vol. 14, pp. 540-543, May 2003)
[Show abstract][Hide abstract] ABSTRACT: RF ablation of ectopic foci in the pulmonary veins (PVs) is a promising treatment for patients with paroxysmal AF. The aim of this study was to evaluate the feasibility of using nonfluoroscopic magnetic electroanatomic mapping of PV during spontaneous or induced ectopy to facilitate focal ablation procedure. The study included 35 patients with drug refractory paroxysmal AF who underwent focal RF ablation of the PV. In 10 (29%) patients, mapping and RF ablation procedures were performed using the nonfluoroscopic magnetic electroanatomic mapping system to enable automatic capture of the location and the timing of the ectopy. As a control, 25 patients underwent conventional endocardial activation mapping technique. There were no significant differences in the clinical characteristics between the two groups. Overall procedural duration was similar between them (199 +/- 52 vs 221 +/- 82 minutes, P > 0.05). However, the mean fluoroscopy time (25 +/- 6 vs 52 +/- 12 minutes, P = 0.01) and the mean number of RF applications (5 +/- 3 vs 12 +/- 9, P = 0.02) were significantly less in patients who underwent electroanatomic mapping. There were no significant differences between the two groups in the acute (90 vs 84%) and long-term success rate (60 vs 56%) after a mean follow-up of 12 +/- 9 months. In conclusion, RF ablation of ectopic foci using nonfluoroscopic magnetic electroanatomic mapping of PVs during spontaneous or induced ectopy is useful even in patients with a limited number of ectopy, and is associated with a similar success rate, but less fluoroscopy time and RF application compared to the conventional approach.
No preview · Article · Jan 2002 · Pacing and Clinical Electrophysiology
[Show abstract][Hide abstract] ABSTRACT: 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.
Methods and Results: The effects of the implantable atrial defibrillator on the total duration of atrial fibrillation, number of atrial fibrillation recurrences, and left atrial size were evaluated prospectively in 16 patients with atrial fibrillation (13 men and 3 women; mean age 58 ± 11 years). Seven patients bad no cardiovascular disease, 5 patients had hypertension. 3 patients had coronary heart disease, and 1 patient bad congenital heart disease. Eight patients had paroxysmal atrial fibrillation for a mean duration of 80 ± 61 months, and eight patients had persistent atrial fibrillation for a mean duration of 68 ± 119 months. Except for one patient who received digoxin throughout the study, alt patients received the same Class I or III antiarrhythmic agent throughout the study. The implantable atrial defibrillator successfully converted 50 (93%) of 54 spontaneous episodes of atrial fibrillation in 12 patients. During the initial 3 months of clinical follow-up, the atrial defibrillator documented 261 ± 270 hours of atrial fibrillation compared with 126 ± 172 hours (P = 0.01) during the subsequent 3 months. The left atrial size decreased from 4.4 ± 0.7 cm at the time of atrial defibrillator implantation to 4.1 ± 0.6 cm (P = 0.02) 6 months later. The number of atrial fibrillation recurrences did not change. These findings were observed in the absence of changes in drug therapy. No complications were observed.
Conclusion: Restoration and maintenance of sinus rhythm in patients with atrial fibrillation by repeated cardioversion with an implantable atrial defibrillator was associated with a reduction in the total arrhythmia duration and a reduction in left atrial size. These results suggest that maintenance of sinus rhythm with the atrial defibrillator may reverse the remodeling process associated with atrial fibrillation.
Preview · Article · Aug 1999 · Journal of Cardiovascular Electrophysiology
[Show abstract][Hide abstract] ABSTRACT: Low energy biatrial shock is an effective means of restoring sinus rhythm in patients with atrial 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 195 V (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.
No preview · Article · Feb 1997 · Pacing and Clinical Electrophysiology