PubMed Health⌕ Search

Biomedical subjects

Shih-Lin Chang

Publications and source records attributed to Shih-Lin Chang.

At least 19 recordsLinked to original sources
PubMed2006

The electrophysiologic characteristics of atrioventricular nodal reentry tachycardia with eccentric retrograde activation.

BACKGROUND: The occurrence of eccentric retrograde atrial activation has been demonstrated to be from 6 to 8% in patients with atrioventricular nodal reentrant tachycardia (AVNRT) by several previous reports. However, most of those reports were limited by the absence of coronary sinus venography to confirm if the retrograde activation was truly left sided. The purposes of this study were to 1) determine the incidence of left sided retrograde atrial activation in our center, 2) determine the specific electrophysiologic characteristics of eccentric and concentric atrial activation and 3) determine the outcome of radiofrequency catheter ablation for AVNRT with eccentric retrograde atrial activation. METHODS: From November 2001 to July 2004, 290 consecutive patients with AVNRT who underwent an electrophysiologic study and radiofrequency ablation were included. Group 1 consisted of AVNRT patients with eccentric retrograde atrial activation; group 2 consisted of AVNRT patients with concentric retrograde atrial activation. The electrophysiologic characteristics of the group 1 and group 2 patients were then compared. RESULTS: The incidence of AVNRT with eccentric retrograde activation confirmed by CS venography was 6.5%. There were more females and atypical AVNRT in patients with retrograde eccentric conduction. There was more VA block after ablation and tachycardia induction by right ventricular pacing/extrastimuli in eccentric rather than concentric retrograde atrial activation. A shorter antegrade fast functional refractory period of the AV node was demonstrated in the atypical eccentric group as compared to the atypical concentric group. CONCLUSION: This study demonstrated the different electrophysiologic characteristics between the AVNRT patients with eccentric and concentric retrograde atrial activation. Successful ablation sites were similar to the standard RA ablation sites in patients with retrograde eccentric conduction.

Adolescent↗
PubMed2006

Anatomic characteristics of the left atrial isthmus in patients with atrial fibrillation: lessons from computed tomographic images.

INTRODUCTION: Left atrial (LA) isthmus ablation was reported to improve the success rate of catheter ablation of paroxysmal atrial fibrillation (AF). LA isthmus ablation could also cure a subset of LA flutter. Therefore, understanding the anatomy of the LA isthmus is important for performing the ablation effectively. METHODS AND RESULTS: Group I included 45 patients (40 male, mean age = 50 +/- 13 years) with paroxysmal AF who underwent catheter ablation. Group II included 45 patients (37 male, mean age = 54 +/- 10 years) without a history of AF. They underwent a 16-slice multidetector computed tomography (MDCT) scan to delineate the LA structures before the ablation procedure. The average length of the LA isthmus was longer in group I than in group II (lateral isthmus: 3.30 +/- 0.68 vs 2.71 +/- 0.60 cm, P < 0.001; medial isthmus: 5.12 +/- 0.94 vs 4.45 +/- 0.63 cm, P < 0.001), and morphological patterns of lateral and medial isthmus were similar between groups. In addition, the average depth of lateral isthmus was similar between groups (0.62 +/- 0.32 vs 0.55 +/- 0.33 cm, P = 0.41), but the average depth of medial isthmus was larger in group I than in group II (0.60 +/- 0.32 vs 0.44 +/- 0.25 cm, P = 0.01). The medial isthmus had more ridges, as compared to the lateral isthmus (13% vs 0%, P = 0.026). Furthermore, the distances between esophagus and lateral isthmus were longer in group I than in group II (at the middle of isthmus and mitral annulus level: 21.0 +/- 4.8 vs 18.4 +/- 6.0 mm, P < 0.001; and 37.1 +/- 5.7 vs 29.6 +/- 8.1 mm, P < 0.001, respectively). CONCLUSION: The LA isthmus was longer in the AF patients. The morphology of the isthmus was variable. Compared with the lateral isthmus, the medial isthmus was longer and had more ridges. A peculiar configuration of the isthmus provided by CT images could influence the ablation strategy.

Anthropometry↗
PubMed2006

Morphological changes of the left atrial appendage after catheter ablation of atrial fibrillation.

INTRODUCTION: The left atrial appendage (LAA) has been proven to be the most important site of thrombus formation in patients with atrial fibrillation (AF). However, the information regarding the morphometric alteration of the LAA related to the outcome of AF ablation is still lacking. Thus, we evaluated the long-term changes of the LAA morphology in patients undergoing catheter ablation of AF using magnetic resonance angiography (MRA). METHODS AND RESULTS: Group 1 included 15 controls without any AF history. Group 2 included 40 patients with drug-refractory paroxysmal AF. They were divided into two subgroups: group 2a included 30 patients without AF recurrence after pulmonary vein (PV) ablation. Group 2b included 10 patients with late recurrence of AF. The LAA morphology before and after (20 +/- 11 months) ablation was evaluated by three-dimensional MRA. The group 2 patients had a larger baseline LAA size (including the LAA orifice, neck, and length) and less eccentric LAA orifice and neck. After the AF ablation, there was a significant reduction in the LAA size in the group 2a patients, and the morphology of the LAA neck became more eccentric during the follow-up period. In group 2b, the LAA size increased and no significant change in the eccentricity of the orifice and neck could be noted. CONCLUSIONS: The morphometric remodeling of the LAA in the AF patients could be reversed after a successful ablation of the AF. Progressive dilation of the LAA was noted in the patients with AF recurrence. These structural changes in the LAA may play a role in reducing the potential risk of cerebrovascular accidents.

Atrial Appendage↗
PubMed2006

Multiple wave diffraction anomalous fine structure.

A new method, multiple-wave diffraction anomalous fine structure, combining the x-ray multiple-wave diffraction and diffraction anomalous fine structure techniques, is proposed. The real part of dispersion correction Deltaf' and fine structure chi function can be obtained directly by multiple diffraction analysis without using Kramers-Krönig relations and kinematical fitting of diffracted intensity. Better wave vector sensitivity of the fine structure is expected. The multiple-wave diffraction anomalous fine structure experiment for a GaAs single crystal is reported as an example.

Journal Article↗
PubMed2006

The electroanatomic characteristics of the cavotricuspid isthmus: implications for the catheter ablation of atrial flutter.

INTRODUCTION: Radiofrequency ablation (RFA) of typical AFL is sometimes difficult because of the poor electroanatomic approach to the cavotricuspid isthmus (CTI). The aim of this study was to correlate the anatomy of the CTI between contact mapping (NavX) and right atrial angiography (RAG), and to investigate the impact of the electroanatomic characteristics of the CTI on the RFA of typical atrial flutter (AFL). METHODS: One hundred patients with typical AFL undergoing RFA were studied. The image-guided group consisted of 50 consecutive patients with the guidance of NavX. NavX geometry and RAG were performed to investigate the morphology of the CTI. The bipolar voltages of the CTI were collected during sinus rhythm by a NavX. The control group consisted of 50 consecutive patients with the guidance of conventional fluoroscopy. RESULTS: There was a good correlation between the angiography and NavX for the anatomy of the CTI. The pouch type had a longer length of CTI than the flat type (33.4 +/- 5.0 vs 22.6 +/- 8.4 mm, P < 0.0001) and deeper depth than the concave type (6.5 +/- 2.2 vs 3.7 +/- 0.8 mm, P < 0.0001) on the angiography. The pouch-type CTI had a longer ablation time and larger pulses of RFA than the other two types. The control group had a longer ablation time, fluoroscopy time, and larger pulses of RFA than image-guided group. CONCLUSIONS: The 3-D mapping system provided a good reconstruction of CTI, which may help in the RFA in patients with a complex anatomy of the CTI.

Adult↗
PubMed2006

Substrate mapping to detect abnormal atrial endocardium with slow conduction in patients with atypical right atrial flutter.

OBJECTIVES: The purpose of this study was to investigate the relationship between the abnormal substrate and peak negative voltage (PNV) in the right atrium (RA) with atypical flutter. BACKGROUND: The impact of a local abnormally low voltage electrogram on the local activation pattern and velocity of atrial flutter (AFL) remains unclear. METHODS: Twelve patients with clinically documented AFL were included to undergo noncontact mapping of the RA. The atrial substrate was characterized by the: 1) activation mapping; 2) high-density voltage mapping; and 3) conduction velocity along the flutter re-entrant circuit. The normalized PNV (i.e., the relative ratio to the maximal PNV) in each virtual electrode recording was used to produce the voltage maps of the entire chamber. The protected isthmus was bordered by low voltage zones. RESULTS: Atypical AFL of the RA was induced by atrial pacing in 12 patients, including 10 upper loop re-entry and 2 RA free wall re-entry flutter. These protected isthmuses were located near the crista terminalis. The mean width of the protected isthmus was 1.7 +/- 0.3 cm and mean voltage at the isthmus was -0.91 +/- 0.39 mV. The conduction velocities within these paths were significantly slower than outside the path (0.30 +/- 0.18 m/s vs. 1.14 +/- 0.41 m/s, respectively; p = 0.004). The ratiometric PNV of 37.6% of the maximal PNV had the best cut-off value to predict slow conduction, with a high sensitivity (92.3%) and specificity (85.7%). CONCLUSIONS: Characterization of the RA substrate in terms of the unipolar PNV is an effective predictor of the slow conduction path within the critical isthmus of the re-entrant circuit.

Adult↗
PubMed2006

Frequency analysis in different types of paroxysmal atrial fibrillation.

OBJECTIVES: This study sought to investigate the regional frequency distribution from multiple bi-atrial sites in different types of paroxysmal atrial fibrillation (AF). BACKGROUND: A previous study showed a left atrium (LA) to right atrium (RA) frequency gradient in patients with paroxysmal AF. METHODS: Forty-four patients (age = 60 +/- 16, male patients = 27) with paroxysmal AF originating from the pulmonary veins (PVs) (n = 31) or superior vena cava (SVC) (n = 13) were included. Frequency analysis was performed on the intracardiac electrograms (7 s, 1 kHz/channel) recorded from PV, posterior LA, coronary sinus (CS), posterolateral RA, and SVC. The largest peak frequency was identified as the dominant frequency (DF). RESULTS: In the PV-AF patients, there was a frequency gradient from the PV ostium to the LA, RA, and SVC (8.5 +/- 3.3 Hz vs. 5.9 +/- 1.1 Hz vs. 5.2 +/- 0.85 Hz vs. 5.5 +/- 0.48 Hz, respectively, p < 0.001). The highest DFs were mostly located at the arrhythmogenic PV ostium (58%). The DFs of the arrhythmogenic PV and PV ostium were significantly higher than those of the non-arrhythmogenic PVs and PV ostia (p < 0.05). In the SVC-AF patients, there was a frequency gradient from the SVC to the RA, LA, and PV (8.0 +/- 2.4 Hz vs. 5.9 +/- 1.1 Hz vs. 5.9 +/- 0.7 Hz vs. 5.8 +/- 0.7 Hz, respectively, p = 0.001). The highest DFs were mostly located inside the SVC (77%) instead of the SVC ostium (as compared with PV-AF patients, p = 0.035). CONCLUSIONS: The location of the highest DF depended on the arrhythmogenic PV or SVC. A frequency gradient was present between the arrhythmogenic thoracic vein and atrium in all patients.

Atrial Fibrillation↗
PubMed2006

Coronary sinus morphology in different types of supraventricular tachycardias.

BACKGROUND: Atrioventricular nodal reentry tachycardia (AVNRT) is based on the concept of dual AV node pathways that are functionally and anatomically distinct. The bigger coronary sinus ostium (CSO) in patients with AVNRT compared to other supraventricular tachycardias (SVTs) may produce separation of atrial inputs into the AV node or create anisotropic conduction, thus giving rise to a different AV nodal physiology. Previous studies measuring the size of the CSO using CS angiography between patients with AVNRT and other SVTs showed conflicting results. Besides, no previous studies have compared the CS morphology of the different forms of AVNRT. OBJECTIVES: This study compares the size and morphology of the CS among patients with typical AVNRT, atypical AVNRT and accessory pathways mediated reentrant tachycardia (AVRT). METHODS: Ninety-six patients with clinically documented SVTs were divided into three groups. The diameter of the CS was measured in LAO projection during end ventricular systole (by choosing the last ventricular inward motion). The CSO as well as 5, 10 and 15 mm inside the CS were measured. CS morphology is defined as either wind-sock shape or tubular shape. RESULTS: The size of the CS ostium was 13.58 +/- 3.98, 15.93 +/- 4.86 and 12.50 +/- 2.83 mm for the atypical AVNRT, typical AVNRT and AVRT, respectively (p = 0.03). There was significant difference in the size of the CS from the ostium until 15 mm into the CS between 1) typical AVNRT and AVRT, 2) typical AVNRT and atypical AVNRT. Typical and atypical AVNRT patients had more windsock morphology CS (13/32, 40.6% and 10/32, 31.2%) compared to AVRT which had only one (1/32, 3.1%) windsock morphology (p = 0.002). CONCLUSION: The easier CS cannulation in patients with typical AVNRT could be due to a bigger CS size and to a more windsock morphology. The CS size and morphology may be a very important substrate of tachycardia in patients with AVNRT.

Adult↗
PubMed2006

The different mechanisms between late and very late recurrences of atrial fibrillation in patients undergoing a repeated catheter ablation.

INTRODUCTION: The mechanisms of late (<1 year after the ablation) and very late (>1 year after the ablation) recurrences of paroxysmal atrial fibrillation (AF) after catheter ablation have not been reported. METHODS AND RESULTS: Fifty consecutive patients undergoing a repeated electrophysiologic study to investigate the recurrence of paroxysmal AF after the first ablation were included. Group 1 consisted of 12 patients with very late (26 +/- 13 months) and group 2 consisted of 38 patients with late (3 +/- 3 months) recurrence of paroxysmal AF. In the baseline study, group 1 had a lower incidence of AF foci from the pulmonary veins (PVs) (67% vs 92%, P = 0.048) and a higher incidence of AF foci from the right atrium (50% vs 13%, P = 0.014) than group 2. In the repeated study, group 1 had a higher incidence of AF foci from the right atrium (67% vs 3%, P < 0.001) and a lower incidence of AF foci from the left atrium (50% vs 97%, P < 0.001), including a lower incidence of AF foci from the PVs (50% vs 79%, P = 0.07) and from the left atrial free wall (0% vs 29%, P = 0.046) than group 2. Furthermore, most of these AF foci (64% of group 1, 65% of group 2) were from the previously targeted foci. CONCLUSION: The right atrial foci played an important role in the very late recurrence of AF, whereas the left atrial foci (the majority were PVs) were the major origin of the late recurrence of AF after the catheter ablation of paroxysmal AF.

Atrial Fibrillation↗
PubMed2006

Preexisting pulmonary vein stenosis in patients undergoing atrial fibrillation ablation: a report of five cases.

INTRODUCTION: Acquired pulmonary vein (PV) stenosis is a well-known complication following catheter ablation of atrial fibrillation (AF). However, the details of congenital PV stenosis have not been reported in patients who underwent catheter ablation of AF. METHODS AND RESULTS: A total of 178 patients (110 men, age: 54 +/- 11 years) with drug-refractory AF received MRA or multidetector CT (MDCT) before ablation for delineation of PV morphologies. Five PVs in 5 patients (2.8%) showed at least 50% stenosis before ablation. We demonstrated two types of preexisting PV stenosis. Type I is the external compression of PV by the descending aorta, observed in LIPV of the three patients. Type II is the focal narrowing of PV, observed in RSPV of the two patients. CONCLUSION: Preexisting stenosis of PV may be a consequence of congenital focal narrowing or external compression by the adjacent structures. Detection of this condition by 3D CT or MRA before catheter ablation can provide information for planning of ablation strategy and prevent misdiagnosis of ablation-related PV stenosis.

Adult↗
PubMed2006

Anatomic proximity of the esophagus to the coronary sinus: implication for catheter ablation within the coronary sinus.

INTRODUCTION: The anatomic proximity between the esophagus and the coronary sinus (CS) might render the esophagus vulnerable to thermal injury during ablation. Therefore, we investigated the anatomic relationship between the esophagus and the CS in patients with atrial fibrillation (AF). METHODS AND RESULTS: Thirty patients (25 males, mean age = 54 +/- 11 years) with drug-refractory paroxysmal AF were included. Sixteen-slice multidetector computed tomography was performed to depict the course of the esophagus and relationship to the CS. The esophagus was in direct contact with the CS in 57% (17/30) of patients (group 1). The mean length of the contact was 6.1 +/- 3.4 mm. In the remaining 13 patients, the esophagus did not come in direct contact with the CS (group 2). The shortest distance between the esophagus and the CS was 4.0 +/- 2.6 mm. The CS diameter (9.4 +/- 1.8 vs 8.5 +/- 2.4 mm, P = 0.15), esophagus width (18.6 +/- 1.6 vs 18.6 +/- 1.7 mm, P = 0.87), anteroposterior diameter of the left atrium (35.9 +/- 3.8 vs 35.0 +/- 3.3 mm, P = 0.58), thickness of the anterior wall of the esophagus (2.9 +/- 0.6 vs 2.9 +/- 0.6 mm, P = 0.97), and shortest distance from the esophagus to the CS ostium (19.3 +/- 5.4 vs 25.0 +/- 6.2 mm, P = 0.02) and to the great cardiac vein (8.5 +/- 5.3 vs 12.1 +/- 6.9 mm, P = 0.10) were compared between the two groups. CONCLUSIONS: In 57% of our patients, the esophagus was in direct contact with the CS, and a significantly shorter distance between the esophagus and the CS ostium was noted in these patients. It is important to prevent esophageal damage when applying energy within the CS.

Adult↗
PubMed2006

Morphologic characteristics of the left atrial appendage, roof, and septum: implications for the ablation of atrial fibrillation.

INTRODUCTION: The left atrium (LA) ablation in different regions, including LA appendage (LAA), LA roof, and LA septum, has recently been proposed to improve the success rate of treating patients with atrial fibrillation (AF). The purpose of this study was to investigate the anatomy of LAA, LA roof, and LA septum, using computed tomography (CT). METHODS AND RESULTS: Multidetector CT scan was used to depict the LA in 47 patients with drug-refractory paroxysmal AF (39 males, age = 50 +/- 12 years) and 49 control subjects (34 males, age = 54 +/- 11 years). The area of LAA orifice, neck, and the length of roof line were greater in AF group than in control subjects. Three types of LAA locations and two types of LAA ridges were observed. Higher incidence of inferior LAA was noted in AF patients. The different morphologies of LA roof were described. Roof pouches were revealed in 15% of AF and 14% of controls. Moreover, we found septal ridge in 32% of AF and 23% of controls. CONCLUSIONS: Considerable variations of LAA and LA roof morphologies were demonstrated. Peculiar structures, including roof pouches and septal ridges, were delineated by CT imaging. These findings were important for determining the strategy of AF ablation and avoiding the procedure-related complications.

Adult↗
PubMed2005

Predictors of non-pulmonary vein ectopic beats initiating paroxysmal atrial fibrillation: implication for catheter ablation.

OBJECTIVES: The purpose of this study was to investigate the predictor of non-pulmonary vein (PV) ectopic beats initiating paroxysmal atrial fibrillation (PAF). BACKGROUND: Non-PV ectopic beats can initiate PAF in some patients and play an important role in the recurrence of PAF after PV isolation. Information on the predictors of non-PV ectopic beats initiating PAF is unknown. METHODS: This study included 293 patients (215 men and 78 women, age 60 +/- 14 years) with clinically documented drug-refractory PAF. Of the 94 patients with non-PV ectopic beats initiating PAF, 38 (40%) patients had superior vena cava (SVC) ectopic beats and 32 (34%) had left atrial posterior free wall (LAPFW) ectopic beats. RESULTS: In a univariate analysis, only female gender was related to the presence of non-PV (p = 0.016) and SVC ectopic beats (p = 0.012). Right atrial enlargement (p = 0.005) and left atrial enlargement (p < 0.001) were related to the presence of LAPFW ectopic beats. In a multivariate analysis, female gender (p = 0.043; odds ratio 2.00, 95% confidence interval [CI] 1.02 to 3.92) and left atrial enlargement (p = 0.007; odds ratio 2.34, 95% CI 1.27 to 4.32) could predict the presence of non-PV ectopic beats. Subgroup analysis showed that female gender could predict the presence of SVC ectopic beats (p = 0.039; odds ratio 2.14, 95% CI 1.04 to 4.43). In contrast, left atrial enlargement could predict the presence of LAPFW ectopic beats (p = 0.002; odds ratio 3.89, 95% CI 1.62 to 9.38). CONCLUSIONS: The location of non-PV ectopic beats initiating PAF can be predicted by both gender and left atrial enlargement.

Atrial Fibrillation↗
PubMed2005

Sinus node injury as a complication of superior vena cava isolation.

We report a case with SVC ectopy initiating AF; the origin and breakout point of the sinus node was inside the SVC, and the SVC ectopy was conducted through the same path as the sinus node activation to depolarize the right atrium. Injury to the sinus node happened after successful isolation of SVC.

Atrial Fibrillation↗
PubMed2005

Catheter ablation of atrial fibrillation versus atrioventricular junction ablation plus pacing therapy for elderly patients with medically refractory paroxysmal atrial fibrillation.

BACKGROUND: Catheter ablation of atrial fibrillation (AF) has become another nonpharmacologic therapeutic option for medically refractory paroxysmal AF. Whether this method is better than atrioventricular (AV) junction ablation plus pacing therapy is unknown. The purpose of this study was to compare the very long-term (longer than 4 years) clinical outcomes of the 2 methods in elderly patients (>65 years old) with medically refractory paroxysmal AF. METHODS: From January 1995 to December 2001, 71 elderly patients with medically refractory paroxysmal AF were included; group 1 included 32 patients with successful AV junction ablation plus pacing therapy and group 2, 37 patients with successful catheter ablation of AF. RESULTS: After a mean follow-up of more than 52 months, the AF was better controlled in the group 1 patients than group 2 (100% vs 81%, P = 0.013), however, they had a significantly higher incidence of persistent AF (69% vs 8%, P < 0.001) and heart failure (53% vs 24%, P = 0.001). Furthermore, the incidence of ischemic stroke and cardiac death was similar between the 2 groups. Compared with the preablation values, a significant increase in the NYHA functional class (1.7 +/- 0.9 vs 1.4 +/- 0.7, P = 0.01) and significant decrease in the left ventricular ejection fraction (44 +/- 8% vs 51 +/- 10%, P = 0.01) were noted in the group 1 patients, but not in the group 2 patients. CONCLUSIONS: Although AV junction ablation plus pacing therapy better controlled the AF in elderly patients with medically refractory paroxysmal AF, that method was associated with a higher incidence of persistent AF and heart failure than catheter ablation of AF in the very long-term follow-up.

Aged↗