PubMed Health⌕ Search

Biomedical subjects

Hung-Fat Tse

Publications and source records attributed to Hung-Fat Tse.

67 records · Page 4Linked to original sources
PubMed2003

Effect of coronary sinus electrode on the optimal atrial defibrillation pathway for an atrioventricular defibrillator.

INTRODUCTION: Previous studies have demonstrated significant failure in converting atrial fibrillation (AF) using a conventional ventricular pathway. The aim of this study was to assess the benefit of incorporating a coronary sinus (CS) lead into the atrial defibrillation pathway in atrial defibrillation threshold (ADFT) reduction in patients with persistent AF. METHODS AND RESULTS: This study was a prospective, randomized assessment of shock configuration on ADFT in 18 patients undergoing elective internal cardioversion for persistent AF (mean AF duration: 8 +/- 9 months). The lead system included a dual-coil defibrillation lead (Endotak DSP, Guidant) with a distal right ventricular (RV) electrode and a proximal superior vena cava (SVC) electrode, a CS lead (Perimeter, Guidant), and a left pectoral cutaneous electrode (Can). In each patient, dual step-up ADFTs were determined for each of three vectors: (1) RV --> SVC+Can; (2) CS --> SVC+Can; and (3) RV --> CS+SVC+Can (group 1, n = 8) or RV+CS --> SVC+Can (group 2, n = 10), using R wave-synchronized biphasic shocks. Successful defibrillation was achieved in all patients without any ventricular proarrhythmia. ADFT of CS --> SVC+Can (11.8 +/- 5.6 J) was significantly lower than ADFT of RV --> SVC+Can (16.5 +/- 7.8 J, P = 0.021). ADFT of CS --> SVC+Can was similar to RV --> CS+SVC+Can (group 1: 12.0 +/- 6.5 J vs 17.4 +/- 4.8 J, P = 0.16), but it was significantly higher than RV+CS --> SVC+Can (group 2: 9.0 +/- 3.9 J vs 11.6 +/- 5.0 J, P = 0.049). CONCLUSION: Patients with persistent AF of substantial duration can be reliably cardioverted using a conventional implantable cardioverter defibrillator (ICD) lead set; however, the incorporation of a CS lead to the conventional ICD lead configuration significantly lowered ADFT. The optimal shock vector that incorporates a CS lead for atrial defibrillation requires future studies.

Aged↗
PubMed2003

Atrial tachycardia arising from an epicardial site with venous connection between the left superior pulmonary vein and superior vena cava.

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.

Abnormalities, Multiple↗
PubMed2003

Regression of left ventricular hypertrophy after treatment of hypertension: comparison of directed M-echocardiography with magnetic resonance imaging in quantification of serial mass changes.

BACKGROUND: This study sought to validate the reliability of serial echocardiographic measurements in detecting left ventricular (LV) hypertrophy regression by using magnetic resonance imaging (MRI) as a reference standard. METHODS AND RESULTS: We studied a small population (n = 20) of patients enrolled in the Prospective Randomized Enalapril Study Evaluating Regression of Ventricular Enlargement (PRESERVE) trial for evaluating LV hypertrophy regression. LV mass was measured by both echocardiography and MRI at baseline and after 1 year. As compared with baseline, systolic and diastolic blood pressures were significantly decreased after 1 year (all P <.05). Echocardiographic technique showed an overestimation of LV mass by 27.6 g at baseline (P =.005) and by 37.1 g after 1 year (P <.001), and there were wide 95% limits of agreement (+/-36.0 g at baseline; and +/-27.6 g after 1 year) when compared with MRI measurement. Significant changes of LV mass from baseline of -20 +/- 22 g (P<.01) and -29 +/- 19 g (P <.01) were detected by using echocardiography and MRI after 1 year, respectively (P =.02), and there were similarly wide limits of agreement for change in LV mass (+/-24.2 g). CONCLUSIONS: Despite the use of careful methodology, echocardiographic measurement of LV mass at a single time point or for serial studies resulted in significant variation in LV mass estimates from measurement using MRI.

Aged↗
PubMed2002

Electrophysiologic actions of dl-sotalol in patients with persistent atrial fibrillation.

OBJECTIVES: We sought to determine the electrophysiologic actions of sotalol in the remodeled atrium of humans. BACKGROUND: In experimental studies, sotalol has limited class III action in the electrically remodeled atrium and did not prevent atrial fibrillation (AF) induction. METHODS: We determined the effective refractory periods (ERPs) at three pacing cycle lengths (400, 500, and 600 ms) in the high right atrium (HRA) and distal coronary sinus (DCS) before and after intravenous infusion of dl-sotalol in 10 patients with persistent AF who underwent internal cardioversion. The same protocols were performed in 10 control subjects in sinus rhythm. RESULTS: In the HRA and DCS, the atrial ERPs at different drive cycle lengths were significantly shorter in patients with AF than in control subjects (p < 0.05). In patients with AF, the atrial ERP's adaptation to rate was nearly normal in the HRA, but was poor in the DCS. In both groups, dl-sotalol significantly increased the atrial ERPs at both the HRA and DCS, as compared with baseline (p < 0.05). However, the prolongation of atrial ERPs was significantly less at a drive cycle length of 600 ms in patients with AF versus control subjects (p < 0.05). After infusion of dl-sotalol, the atrial ERP's adaptation to rate at both the HRA and DCS was poor in patients with AF, and AF was still easily inducible in the majority of them, but not in control subjects. CONCLUSIONS: The results of the present study demonstrate that the electrophysiologic actions of dl-sotalol are significantly attenuated in the chronically remodeled human atrium, and these changes might represent a probable explanation for the low efficacy of dl-sotalol to prevent early AF recurrence after electrical cardioversion.

Aged↗
PubMed2002

New Bayesian discriminator for detection of atrial tachyarrhythmias.

BACKGROUND: Accurate, rapid detection of atrial tachyarrhythmias has important implications in the use of implantable devices for treatment of cardiac arrhythmia. Currently available detection algorithms for atrial tachyarrhythmias, which use the single-index method, have limited sensitivity and specificity. METHODS AND RESULTS: In this study, we evaluated the performance of a new Bayesian discriminator algorithm in the detection of atrial fibrillation (AF), atrial flutter (AFL), and sinus rhythm (SR). Bipolar recording of 364 rhythms (AF=156, AFL=88, SR=120) at the high right atrium were collected from 20 patients who underwent electrophysiological procedures. After initial signal processing, a column vector of 5 features for each rhythm were established, based on the regularity, rate, energy distribution, percent time of quiet interval, and baseline reaching of the rectified autocorrelation coefficient functions. Rhythm identification was obtained by use of Bayes decision rule and assumption of Gaussian distribution. For the new Bayesian discriminator, the overall sensitivity for detection of SR, AF, and AFL was 97%, 97%, and 94%, respectively; and the overall specificity for detection of SR, AF, and AFL was 98%, 98%, and 99%, respectively. The overall accuracy of detection of SR, AF, and AFL was 98%, 97% and 98%, respectively. Furthermore, sensitivity, specificity, and accuracy of this algorithm were not affected by a range of white Gaussian noises with different intensities. CONCLUSIONS: This new Bayesian discriminator algorithm, based on Bayes decision of multiple features of atrial electrograms, allows rapid on-line and accurate (98%) detection of AF with robust anti-noise performance.

Adolescent↗
PubMed2002

Nonfluoroscopic magnetic electroanatomic mapping to facilitate focal pulmonary veins ablation for paroxysmal atrial fibrillation.

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.

Adult↗
PubMed2002

Automatic mode switching of implantable pacemakers: I. Principles of instrumentation, clinical, and hemodynamic considerations.

Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff," "running average," "sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia.

Algorithms↗
PubMed2002

Automatic mode switching of implantable pacemakers: II. Clinical performance of current algorithms and their programming.

While the hemodynamic and clinical significance of automatic mode switching (AMS) in patients with pacemakers has been demonstrated, the clinical behavior of AMS algorithms differ widely according to the manufacturers and pacemaker models. In general, a "rate-cutoff" detection method of atrial tachyarrhythmias provides a rapid AMS onset and resynchronization to sinus rhythm at the termination of atrial tachyarrhythmias, but may cause intermittent oscillations between the atrial tracking and AMS mode. This can be minimized with a "counter" of total number of high rate events before the AMS occurs. The use of a "running average" algorithm results in more stable rate control during AMS by reducing the incidence of oscillations, but at the expense of delayed AMS onset and resynchronization to sinus rhythm. Algorithms may be combined to fine tune the AMS response and to avoid rapid fluctuation in pacing rate. Appropriate programming of atrial sensitivity, and the avoidance of ventriculoatrial cross-talk are essential for optimal AMS performance.

Algorithms↗
PubMed2002

Bleeding and thromboembolic risks of internal cardioversion for persistent atrial fibrillation.

Although internal cardioversion is an effective method for converting AF the thromboembolic risk and bleeding complication of this procedure remains unclear. Retrospective analysis of the thromboembolic events and bleeding complications was performed in 114 consecutive patients (mean age 63 +/- 10 years, 91 men) who underwent internal cardioversion for persistent AF (mean AF duration 31 +/- 42 months). All patients received therapeutic warfarin for 3 weeks prior to the procedure, which was then replaced by periprocedural heparin therapy during internal cardioversion. The mean INR value before the internal cardioversion was 1.3 +/- 0.2. A total of 992 R wave synchronized shocks were delivered (mean 8.7 shocks/patients) without ventricular proarrhythmia. Successful internal cardioversion of AF was achieved in 100 (88%) patients. Two (2%) patients developed major bleeding complications with pericardial effusion after the procedure. Both of them subsided with conservative treatment. Minor bleeding with wound hematoma occurred in 8 (7%) of 114 after the procedure. Overall, there was no significant difference in the risk of procedure related complication between the use of heparin infusion and subcutaneous LMWH injection (6/78 [13%] vs 3/36 [8%], P = 0.9). No thromboembolic event was observed after 4 weeks of follow-up. In conclusion, the risk of thromboembolism after discontinuation of anticoagulation before the procedure is low in patients with persistent AF underwent internal cardioversion. However, the use of periprocedural heparin therapy was associated with an increase risk of procedure related bleeding complications.

Anticoagulants↗
PubMed2002

Effect of coexisting cardiovascular disease on the long-term efficacy and safety of the implantable atrial defibrillator.

The long-term efficacy and safety of implantable atrial defibrillator (IAD) therapy in patients with AF and cardiovascular disease is unclear. The aim of this study was to evaluate the efficacy and safety of IAD therapy in patients with and without coexisting cardiovascular disease. In 115 patients implanted with an IAD, 85 patients had cardiovascular disease: 41 (48%) patients had 1 cardiovascular abnormality, 29 (35%) patients had 2, 13 (15%) patients had 3, and 2 (2%) patients had 4 different cardiovascular abnormalities. The device was programmed into a rhythm monitoring mode for the first 3-month postimplant period. All defibrillation therapy was performed under physician supervision to monitor safety and efficacy. After this initial monitoring period, patients were allowed to activate their device away from the hospital or clinic. A total of 357 spontaneous AF episodes occurred in 83 (72%) patients during observed operation and the mean shock efficacy was 93.5+/-20.3% (lower 95% confidence interval [CI] 89.8%). As of the lastfollow-up, 58 (55%) patients had transition to receive nonphysician observed therapy. Forty-two (72%) patients had experienced 332 episodes of AF for which theyhad received device therapy away from the hospital/clinic (mean shock efficacy 90.5+/-39.7%). The presence of hypertension, valvular heart disease, and ischemic heart disease did not affect the shock efficacy of the IAD during physician observed and nonobserved therapy (P > 0.05). However, the presence of congestive heart failure was associated with a lower clinical efficacy during observed and nonobserved therapy (P < 0.05). Overall, 5,262 shocks have been delivered with the IAD without any episode of proarrhythmia. The observed proarrhythmic risk was 0%, with an estimated maximum proarrhythmic risk of 0.06% per shock (95% upper CI). A stand-alone IAD appears to be safe in the presence of cardiovascular disease. The lower clinical efficacy for AF associated with congestive heart failure might be related to a higher rate of early reinitiation of AF after defibrillation.

Adult↗
PubMed2002

Acute results of transvenous cryoablation of supraventricular tachycardia (atrial fibrillation, atrial flutter, Wolff-Parkinson-White syndrome, atrioventricular nodal reentry tachycardia).

INTRODUCTION: Radiofrequency (RF) catheter ablation currently is used for treatment of cardiac arrhythmias. Although the success rate is high for almost all supraventricular tachycardias (SVT), this technique has some drawbacks, especially when pulmonary veins (PV) are targeted for treatment of atrial fibrillation (AF). Additionally, new techniques for isolation of the PVs have the drawback that they can be used only for PV isolation and not for routine treatment of other SVTs. The aim of this study was to report on the safety and efficacy of a new cryoablation system for treatment of all SVTs. METHODS AND RESULTS: Forty-nine patients with SVT (38 men; age 48 years, range 23-76) were enrolled in the study. Five patients were withdrawn from the study before they underwent cryoablation. The remaining 44 patients were treated with cryoablation (22 AF, 15 atrial flutter, 3 accessory pathway, 2 AV nodal reentrant tachycardia, 1 AV junction ablation for permanent AF, 1 atrial tachycardia). Cryoablation was performed with the CryoCor cryoablation system, which uses a precooling system and N2O as a refrigerant. The number of freezes applied varied according to the index arrhythmia treated. Successful isolation of PVs was performed in 20 of (96%) 21 AF patients and 53 of 55 veins. The overall acute success was 98% (43/44). Fifty-three PVs were isolated (2.5/patient). The success rate was 100% (23/23) for right-sided procedures. The average and nadir temperatures reached in right-sided and left-sided procedures were -77 degrees C and -80 degrees C and -75 degrees C and -78 degrees C, respectively. No acute PV stenosis was seen. CONCLUSION: This novel cryoablation system appears to be safe and can successfully treat different types of SVTs, including AF. Isolation of PVs is possible without producing stenosis. Despite the high blood flow in the right atrial isthmus and PVs, bidirectional conduction block can be achieved.

Adult↗