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Ming-Lon Young

Publications and source records attributed to Ming-Lon Young.

5 recordsLinked to original sources
PubMed2003

Multiple accessory pathways in pediatric patients with Wolff-Parkinson-White syndrome.

The characteristics of multiple accessory pathways in children have not been previously studied. Records were reviewed of 317 consecutive pediatric patients with Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency catheter ablation at our institution. Twenty-eight patients (9%) had multiple pathways (a total of 64 pathways: 21 patients had 2, 6 had 3, and 1 patient had 4 pathways). The locations were left free wall (22 pathways), right free wall (19 pathways), posteroseptal (17 pathways), and anteromidseptal (6 pathways). Of these 64 pathways, 55 were ablated successfully without complications, 5 failed ablation, and 4 fasciculoventricular fibers did not require treatment. Three patients had a newly found pathway at the repeat session. Three patients had atrioventricular nodal reentrant tachycardia and the slow pathway area was modified. One patient had failed initial ablation and had a successful ablation using a 3-dimensional electroanatomic mapping system. Compared with patients with a single pathway, those with multiple pathways exhibited a higher incidence of antidromic tachycardia, a shorter anterograde accessory pathway effective refractory period (<250 ms), a longer fluoroscopic time (65 +/- 43 vs 39 +/- 46 minutes, p <0.05), and a larger number of unsuccessful attempts (9 +/- 16 vs 5 +/- 8, p <0.05). Success rate (92% vs 93%) and recurrence rate (1.7% vs 2.1%) were similar in both groups. This study demonstrates that multiple pathways are not rare in pediatric patients and that multiple pathways contrast with a single pathway in a variety of conduction properties.

Adolescent↗
PubMed2003

Effects of a blocked atrial beat on the atrioventricular nodal recovery property in patients with dual nodal pathways.

Dual AVN physiology can be demonstrated by a variety of maneuvers. To determine whether AVN recovery times following a blocked extrastimulus facilitate or obscure detection of dual AVN physiology, 11 patients (9-17 years) were studied with dual AVN pathways by using single and double atrial extrastimuli. With a single atrial extrastimuli, the premature atrial stimulus (A2) was coupled to basic atrial beats (A1). The fast and slow AVN recovery curves were constructed with plots of the nodal conduction time against the recovery time (A1A2,A2H2). With double atrial extrastimuli, a fixed blocked A2 beat (A2B) was followed by a scanning atrial beat (A3). The nodal recovery property post-A2B was studied by plots of A2BA3,A3H3. In all patients the recovery curve of the fast pathway post-A2B had a leftward shift when compared to that of the pre-A2B curve (i.e., the AH was shortened at the same recovery time). The window of slow pathway conduction post-A2B disappeared totally in five patients and decreased significantly in six patients (post-A2B: 26 +/- 42 ms; pre-A2B: 80 +/- 65 ms, P < 0.05). In the six patients that still had slow pathway conduction post-A2B, the slow pathway effective refractory period post-A2B was significantly less than that of pre-A2B (215 +/- 38 vs 268 +/- 16 ms, P < 0.05). The fast pathway effective refractory period post-A2B was also diminished significantly (235 +/- 62 vs 357 +/- 76 ms, P < 0.0001). The authors conclude that blocked atrial beats decrease the visibility of the slow pathway conduction.

Adolescent↗
PubMed2003

MR evaluation of arrhythmogenic right ventricular cardiomyopathy in pediatric patients.

OBJECTIVE: The aim of our study was to correlate the findings of three MR imaging sequences with the clinical findings of possible arrhythmogenic right ventricular cardiomyopathy in pediatric patients. MATERIALS AND METHODS: Twenty-six consecutive pediatric patients underwent MR imaging with ECG-gated non-breath-hold spin-echo T1-weighted non-fat-suppressed and fat-suppressed sequences. The MR images were evaluated for thinning or fat signal in the right ventricular wall and for enlargement or increased trabeculation of the right ventricle or right ventricular outflow tract. Cine MR imaging was used to assess wall motion abnormalities. Cardiac biopsy was performed in 17 patients. Biopsy results and other clinical findings suggesting arrhythmogenic right ventricular cardiomyopathy were tabulated. RESULTS: Two MR imaging studies were of poor quality as a result of arrhythmias, and one study was incomplete. In the 23 remaining patients, there were (mean +/- SD) 1.5 +/- 1.0 and 0.8 +/- 1.0 findings of possible arrhythmogenic right ventricular cardiomyopathy in the non-fat-suppressed and the fat-suppressed sequences, respectively. Fat-compatible signal in the myocardium was detected in 16 (70%) of 23 non-fat-suppressed studies and in five (22%) of 23 fat-suppressed studies (p = 0.003). The non-fat-suppressed sequence had a higher sensitivity (75% vs 43%) and a lower specificity (38% vs 75%) for fatty infiltration than did the fat-suppressed sequence when correlated with the biopsies. The linear correlation between all MR findings and all clinical diagnostic criteria, including biopsy, was better for the combination of cine and both T1 sequences (r = 0.58) than for the non-fat-suppressed (r = 0.53) or fat-suppressed (r = 0.46) T1 sequences alone. CONCLUSION: MR imaging showed moderate correlation with the clinical criteria in the diagnosis of arrhythmogenic right ventricular cardiomyopathy.

Adolescent↗
PubMed2002

Quantitative assessment of the recovery property of atriofascicular/atrioventricular-type Mahaim fiber.

INTRODUCTION: One of the characteristics of the Mahaim fiber is that it possesses a decremental property related to the slow rate of recovery of its excitability similar to that of AV node. The aim of this study was to evaluate the recovery property of the atriofascicular/atrioventricular-type Mahaim fiber and compare it with that of the AV node. METHODS AND RESULTS: Nine patients with a Mahaim fiber were studied; 8 of the patients had atriofascicular/atrioventricular-type fiber. Different models were used to analyze the relationship between conduction time for the Mahaim fiber and the corresponding coupling intervals. The simplest model with the best fit was found to be the linear regression of the natural log of conduction time on corrected coupling intervals. The individual R2 values ranged between 0.43 and 0.98 for the Mahaim fiber and between 0.79 and 0.98 for AV node. The final model chosen for the log transformed data for the Mahaim fiber and for the AV node was the line with parameter estimates defined as a weighted average, over patients, of the corresponding individual line parameters. The weight used for each parameter was the inverse of its variance. The slopes of the lines of the transformed data were not significantly different between the Mahaim fiber and the AV node. Thus, the best fitting curve for the recovery property of the AF-type Mahaim fiber is a simple exponential curve similar to that of the AV node. CONCLUSION: The atriofascicular/atrioventricular-type Mahaim fiber has a quantitative recovery property very similar to that of the AV node.

Adolescent↗