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Biomedical subjects

F C Lin

Publications and source records attributed to F C Lin.

At least 73 records · Page 4Linked to original sources
PubMed1994

Double loop figure-of-8 reentry as the mechanism of multiple atrioventricular node reentry tachycardias.

Seven patients with multiple atrioventricular node reentry tachycardia were analyzed to unravel the mechanism of these tachycardias. Six of the seven patients showed anterograde dual atrioventricular node pathways and one showed anterograde conduction through the fast pathway. Three types of retrograde pathways were noted among these seven patients: (1) the fast pathway with the earliest atrial activation at the His bundle area; (2) the intermediate pathway with the earliest atrial activation at the ostium of the coronary sinus; and (3) the slow pathway with the earliest atrial activation at the ostium of the coronary sinus. All seven patients used the intermediate pathway for retrograde conduction. However, one patient showed evidence of retrograde slow pathway conduction with demonstrable retrograde dual pathways, and another showed evidence of retrograde fast pathway conduction with a shift of atrial activation sequence when conduction switched to the intermediate pathway. Four different types of reentry circuits using either the fast or the slow pathway as the anterograde limb and one of the three retrograde pathways as the retrograde limb were demonstrated in these seven patients, resulting in two types of tachycardias in four patients and three types of tachycardias in three patients. A change in tachycardia type could be induced with atrial or ventricular stimulation. A radiofrequency current delivered to the inferior aspect of Koch's triangle along the tricuspid anulus in five patients resulted in selective ablation or modification of the intermediate pathway or the slow pathway, with preservation of anterograde atrioventricular conduction and abolition of tachycardias. The findings suggest that a double loop figure-of-8 reentry circuit including a fast pathway, a slow pathway, and an intermediate pathway is responsible for multiple atrioventricular node reentry tachycardias.

Adult↗
PubMed1994

Radiofrequency ablation therapy in idiopathic left ventricular tachycardia with no obvious structural heart disease.

BACKGROUND: The feasibility and efficacy of radiofrequency ablation therapy in idiopathic left ventricular tachycardia has not been assessed in a large group of patients. METHODS AND RESULTS: Twenty consecutive patients with idiopathic left ventricular tachycardia and without structural heart disease underwent electrophysiological study, pharmacological interventions with administration of verapamil and adenosine, and radiofrequency ablation therapy. There were 17 men and 3 women with a mean age of 28 +/- 8 years. The QRS configuration during tachycardia was of right bundle branch block and superior axis in 13 patients, indeterminate axis in 6 patients, and right axis in 1 patient. The tachycardia was electrically inducible and responsive to verapamil but not to adenosine. Thirteen patients demonstrated entrainment. Activation and pace-mapping studies disclosed that the tachycardia originated from the inferior apical septum in 15 patients, the midseptum in 4 patients, and the anterior lateral wall of the left ventricle in 1 patient. Radiofrequency ablation was successful in 17 of the 20 patients (85%). The successful ablation sites were characterized by an endocardial activation time 30 milliseconds earlier than the onset of QRS during tachycardia and by a pace-mapping QRS similar to or closely resembling the tachycardia. All patients displayed sharp spikes preceding the local ventricular electrogram at the ablation site. However, these sharp spikes also were noted in 15 control patients and were not specific for this tachycardia; they persisted after ablation. There were no complications. A follow-up of 7 +/- 8 months in the 17 successfully ablated patients showed no symptomatic tachyarrhythmias without medications. Six patients underwent repeat electrophysiological study, and no induction of tachycardia was revealed. CONCLUSIONS: Radiofrequency ablation therapy is effective and safe in patients with idiopathic left ventricular tachycardia. It should be considered as the primary therapeutic modality in these patients.

Adult↗
PubMed1994

Concertina-like phenomenon in ventricular preexcitation due to spontaneous atrioventricular nodal Wenckebach periodicity.

Electrophysiologic study and radiofrequency ablation therapy were performed in a 28-year-old male patient with the Wolff-Parkinson-White syndrome and electrocardiographic manifestation of concertina phenomenon. His bundle recordings showed a sinus cycle length of 720 = ms with a cyclic variation of QRS morphologies of every 3 beats and an antidromic atrial echo following the last fully preexcited QRS complex. After successful radiofrequency ablation of a left posterior accessory pathway, spontaneous 3:2 atrioventricular nodal Wenckebach periodicity was noted and the mechanism of the concertina phenomenon was unraveled.

Adult↗
PubMed1994

Worsening of vasovagal syncope after beta-blocker therapy.

Head-up tilt test was done in a 27-year-old man with recurrent syncope of unexplained cause. Severe sinus bradycardia and hypotension accompanied by light-headedness, cold sweating, and nausea occurred at 80 degrees head-up position during 4 micrograms/min isoproterenol infusion. Oral propranolol, 160 mg/d, in four divided doses, effectively prevented the above-mentioned abnormal vasovagal reflexes; diltiazem was only partially effective while disopyramide, aminophylline, or atropine was ineffective in preventing the abnormal vasovagal reflexes induced by head-up tilt with isoproterenol infusion. However, the patient experienced ten episodes of syncope in 2 weeks after he was discharged from the hospital on a regimen of atenolol, 50 mg/d. His symptoms ameliorated immediately after discontinuation of atenolol therapy and he became free of severe symptoms while receiving fludrocortisone. Thus, we have documented a patient with worsening of vasovagal syncope after beta-blocker therapy.

Adrenergic beta-Antagonists↗
PubMed1993

Radiofrequency ablation in multiple accessory pathways and the physiologic implications.

The presence of multiple accessory pathways was noted in 24 of 210 consecutive patients (12 males and 12 females aged 15 to 77 years [mean +/- SD 43 +/- 16]) with the Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency ablation. Six had 3 and 18 had 2 accessory pathways. There were 25 manifest and 29 concealed accessory pathways. The location of the accessory pathways was in the left free wall in 22, the right free wall in 17, the left posterior portion of the ventricular septum in 8, the right posterior portion of the ventricular septum in 6, and the midseptum in 1. The success rate of accessory pathway ablation and the fluoroscopic time in these 24 patients with multiple accessory pathways were 89% and 78 +/- 66 minutes, respectively, whereas they were 98% (p < 0.01) and 36 +/- 37 minutes (p = 0.01) in the 186 patients with a single accessory pathway. The mean applications, the power level of the radiofrequency current and the application duration in these 24 patients were 21 +/- 22, 30 +/- 3 W, and 27 +/- 10 seconds, respectively. In the 186 patients with a single accessory pathway, they were 9 +/- 12 applications (p = 0.02), 30 +/- 4 W (p = NS) and 26 +/- 9 seconds (p = NS), respectively. Seventeen of the 24 patients had a follow-up electrophysiologic study 89 +/- 40 days after ablation, and 2 (12%) had resumption of a right and left accessory pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Prognosis after a first Q-wave myocardial infarction in ethnic Chinese people: a prospective study.

The prognosis after a first Q-wave myocardial infarction was investigated in 206 Chinese patients of 65 years or younger who had a predischarge cardiac catheterization and coronary angiography. Three patients studied were lost to follow-up. In the remaining 203 patients with ages of between 28 and 65 years, 101 (49.8%) had 0- or 1-vessel disease, 56 (27.6%) had 2-, and 38 (18.7%) had 3-vessel disease. Significant left main coronary artery stenosis was noted in 8 (3.9%). During a mean follow-up of 33 months, 33 (16.3%) patients had 36 episodes of cardiac events, and 16 (7.9%) died of cardiac causes. Stepwise logistic regression analysis revealed that the left ventricular ejection fraction and left main coronary artery disease were predictors of cardiac mortality, while age and the extent of coronary artery disease were predictors of total cardiac events. There was no variable that could predict recurrence of myocardial infarction.

Aged↗
PubMed1993

A simple technique for selective radiofrequency ablation of the slow pathway in atrioventricular node reentrant tachycardia.

OBJECTIVES: A simple technique was designed for radiofrequency ablation therapy of atrioventricular (AV) node reentrant tachycardia. BACKGROUND: This technique was based on the hypothesis that slow pathway conduction reflects conduction through the compact node and its posterior atrial input. METHODS: A total of 100 consecutive patients were studied; there were 37 men and 63 women, with a mean age of 48 +/- 15 years. All 100 patients had induction of sustained tachycardia with (51 patients) or without (49 patients) administration of isoproterenol or atropine, or both. The ablation catheter was initially manipulated to record the largest His bundle deflection from the apex of Koch's triangle. It was then curved downward and clockwise to the area of the compact node when His deflection was no longer visible and the ratio of atrial to ventricular electrogram was < 1. The radiofrequency current was delivered from the 4-mm tip electrode a mean of 5 +/- 7 times at a power of 25 +/- 4 W for a duration of 21 +/- 4 s. The total fluoroscopic time was 19 +/- 11 min. RESULTS: Selective ablation (56 patients) or modification (26 patients) of the slow pathway without affecting anterograde and retrograde fast pathway conduction was achieved in 82 patients. Ablation or modification of both the retrograde fast pathway and the slow pathway but with preservation of anterograde fast pathway conduction was noted in 12 patients. Ablation or modification of the retrograde fast pathway alone or both anterograde and retrograde fast pathway conduction was noted in three patients. Complete AV node block occurred in three patients. Seventy-three patients had no induction of echo beats or tachycardia and 24 patients had induction of a single echo beat after ablation. Follow-up study was performed in 62 patients 76 +/- 18 days after ablation. Thirty-nine patients had no induction of echo beats or tachycardia, 22 had induction of echo beats alone and 1 patient had induction of sustained tachycardia. CONCLUSION: Selective ablation of the slow AV node pathway can be achieved by a simple procedure with a high success rate and few complications.

Adolescent↗
PubMed1993

Radiofrequency ablation therapy in three patients with paroxysmal atrial tachycardia.

Radiofrequency ablation therapy was performed in three patients with paroxysmal atrial tachycardia. There were two females and one male, aged 80, 63, and 75 years, respectively. All three patients had induction of sustained atrial tachycardia. The tachycardia could be terminated by overdrive atrial pacing or atrial premature stimulation; it could also be terminated by intravenous bolus of adenosine triphosphate. In all three patients, there was no fragmented atrial electrograms recorded within the right atrium, and there was no ventriculo-atrial conduction during ventricular pacing. The earliest atrial activation during tachycardia in these three patients was registered, respectively, at a site slightly posterior and inferior to the His-bundle recording site, at the anterior-superior border of Koch's triangle slightly posterior to the His-bundle recording site, and at the mid-lateral aspect of the right atrium over the crista terminalis at the junction of right atrial appendage and sinus venarum. Radiofrequency current was delivered to the site of the earliest atrial activation during tachycardia through a 4-mm tip electrode catheter. It resulted in termination of tachycardia and ablation of the tachycardia focus. Follow-up observation over a period of 16, 15, and 4 months, respectively, in these three patients showed no recurrence of tachycardia. A repeat electrophysiological study was performed 52 and 63 days after ablation in two patients and revealed no induction of atrial tachycardia.

Aged↗
PubMed1992

Usefulness of predischarge electrophysiologic study in predicting late outcome after surgical ablation of the accessory pathway in the Wolff-Parkinson-White syndrome.

A predischarge electrophysiologic study was performed in 113 patients with the Wolff-Parkinson-White (WPW) syndrome who had undergone surgical ablation of the accessory pathway. The study was performed 5 to 20 (mean 10 +/- 3) days after surgery. There were 82 male and 31 female patients (aged 4 to 58 years, mean 36 +/- 13). Sixty-one patients (54%) had manifest, 52 (46%) had concealed and 12 (11%) had multiple accessory pathways. All but 1 patient had atrioventricular reentrant tachycardia incorporating single or multiple accessory pathways during the control electrophysiologic study. The accessory pathways were located in the left ventricular free wall in 60% of cases, right ventricular free wall in 22%, posteroseptum in 13%, and anteroseptum in 5%. The predischarge electrophysiologic study showed that the accessory pathway was capable of anterograde and retrograde conductions in 4 patients (all with manifest WPW syndrome). Four patients showed induction of supraventricular tachycardia, including 2 with atrioventricular reentrant tachycardia, and 2 with atrioventricular nodal reentrant tachycardia. Recurrence of supraventricular tachycardia was noted in 5 patients during a follow-up of 28 +/- 26 months. Of these 5 patients, 2 had inducible and 3 had no inducible supraventricular tachycardia during the predischarge electrophysiologic study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Nature of dual atrioventricular node pathways and the tachycardia circuit as defined by radiofrequency ablation technique.

OBJECTIVES: A comprehensive electrophysiologic study followed by selective radiofrequency ablation from three sites was performed in patients with atrioventricular (AV) node reentrant tachycardia to better delineate the nature of the tachycardia circuit. BACKGROUND: We postulated that the retrograde fast pathway is the anterior superficial group of transitional cells and the slow pathway is the compact node with its posterior input of transitional cells. Twenty-three consecutive patients were studied. In nine, the atria could be dissociated from the tachycardia by delivery of an atrial extrastimulus during tachycardia. METHODS: Radiofrequency ablation was performed with three approaches. The anterior approach was designed to interrupt the anterior superficial atrial input to the compact node, the posterior approach to interrupt the posterior atrial input to the compact node and the inferior approach to destroy the compact node itself. RESULTS: Selective ablation of the retrograde fast pathway was achieved in seven patients, six with the anterior and one with the inferior approach. Anterograde fast pathway conduction was not affected, whereas retrograde fast pathway conduction was either abolished or markedly depressed. None had induction of echoes or tachycardia after ablation. Selective ablation of the slow pathway was successful in 13 patients, 1 with anterior, 3 with posterior and 9 with inferior approaches. In these 13 patients, both anterograde and retrograde fast pathway conduction were not affected, the dual pathway physiology was abolished and the tachycardia was not inducible after ablation. Ablation of both the retrograde fast pathway and the slow pathway occurred with the inferior approach in three patients. CONCLUSIONS: We conclude that the retrograde fast pathway is likely to be the anterior superficial group of transitional cells, whereas the slow pathway is the compact node and its posterior input of transitional cells. A barrier seems to exist between the atrium and the tachycardia circuit. In a broad view of the AV node structure, the tachycardia circuit is confined to the node.

Atrial Function↗
PubMed1992

Sinus automaticity and sinoatrial conduction in severe symptomatic sick sinus syndrome.

Electrophysiologic studies with recordings of sinus node electrograms were performed in 38 patients with severe symptomatic sick sinus syndrome. Thirty-two of the 38 patients had episodic tachyarrhythmias and 17 presented with syncope. The clinically documented sinus or atrial pause was 5.6 +/- 2.8 s (mean +/- SD). Patients were divided into three groups according to electrophysiologic findings. Group I consisted of nine patients with complete sinoatrial block. Sinus node electrograms were recorded during the episodes of long pauses. Seven patients had unidirectional exit block, with the atrial impulse being capable of retrograde penetration to the sinus node causing suppression of sinus automaticity; two had bidirectional sinoatrial block. Group II consisted of 22 patients with either 1:1 sinoatrial conduction (group IIa = 13 patients) or second degree sinoatrial exit block (group IIb = 9 patients) during spontaneous sinus rhythm. Sinoatrial exit block, ranging from 1 to greater than 14 sinus beats, was observed during postpacing pauses that ranged from 1,650 to 37,000 ms (mean 7,286 +/- 6,989). The maximal sinus node recovery time ranged from 770 to 5,580 ms (mean 3,004 +/- 1,686) and was normal in 5 patients and prolonged in 17. Group III consisted of seven patients with no recordable sinus node electrogram, reflecting either a technical failure or a quiescence of sinus activity. The sinus node recovery time in these seven patients ranged from 1,190 to 4,260 ms (mean 2,949 +/- 1,121). Thus, abnormalities in both sinus node automaticity and sinoatrial conduction are responsible for the long sinus or atrial pauses in the sick sinus syndrome. However, complete sinoatrial exit block can occur and cause severe bradycardia with escape rhythm; repetitive sinoatrial exit block plays a major role in producing posttachycardia pauses.

Cardiac Pacing, Artificial↗
PubMed1992

Application of neural networks in medical diagnosis: the case of sexually-transmitted diseases.

In this paper neural networks are used to formulate a means of diagnosing sexually-transmitted diseases (STD's). An overview of the theoretical background of neural networks is presented. A summary of the diseases used in the project and their signs and symptoms are given. These signs and symptoms are used to train a network. Upon presentation of a set of signs and symptoms to the trained network, the presence of a disease or diseases with those symptoms may be deduced.

Diagnosis, Computer-Assisted↗
PubMed1992

Effect of heart rate on pressure half-time in patients with mitral stenosis.

The effect of heart rate on pressure-half time has been controversial. This study attempted to clarify this issue in patients with mitral stenosis. Twenty cases were enrolled, 10 with atrial fibrillation and 10 with sinus rhythm. Twenty beats were analyzed for each patient. The results showed that in patients with atrial fibrillation the pressure half-time was hardly measurable in the cardiac cycles with a ventricular rate more than 100/min; by excluding these fast beats, the pressure half-time showed no relationship with the heart rate. Similarly, there was no significant correlation between heart rate and pressure half-time in patients with sinus rhythm when the heart rate was less than 70/min. However, if the sinus rate was more than 70/min, the correlation became statistically significant. We conclude that when using pressure half-time to derive mitral valve area we should avoid to use the beats with ventricular rate greater than 100/min in patients with atrial fibrillation. In patients with sinus rhythm, we should try to use those beats with heart rate greater than 70/min if possible. Otherwise, significant error may occur.

Adult↗
PubMed1992

Simplified continuity equation: a simple, accurate, and noninvasive method in the evaluation of aortic stenosis.

Traditional evaluation of aortic stenosis usually requires cardiac catheterization for estimation of aortic valve area by the Gorlin formula. However, it is invasive and has been shown to be inaccurate in the presence of aortic regurgitation or low cardiac output. Evaluation of aortic stenosis by Doppler echocardiography using a continuity equation has been proved to have excellent correlation with cardiac catheterization. It requires hand tracing and computer software for calculation of time velocity integral. Recently, a simplified continuity equation was introduced, which uses the peak velocities instead of time velocity integrals. It saves time and obviates the computer assistance. The purpose of this study is to evaluate its accuracy using the standard continuity equation as the reference standard. Seventy patients with pure or combined aortic stenosis were examined. There was an excellent correlation between these two methods (r = 0.979, 95% confidence interval: 0.978-0.980). The aortic valve area derived from the peak velocity method = 0.018 + 0.949 X aortic valve area derived from the time velocity integral. The difference between the two methods was 0.04 +/- 0.08 cm2 (mean +/- SD) with a 95% confidence interval of -0.12 to 0.20 cm2. Furthermore, the correlation still remained good even in the presence of significant aortic regurgitation or impaired left ventricular function. In conclusion, the simplified continuity equation is a safe, time-saving, and accurate method for the evaluation of aortic stenosis.

Adult↗
PubMed1991

Identification of a new gene in an operon for cellulose biosynthesis in Acetobacter xylinum.

DNA sequencing of the region downstream of the cellulose synthase catalytic subunit gene of Acetobacter xylinum led to the identification of an open reading frame coding for a polypeptide of 86 kDa. The deduced amino acid sequence of this polypeptide matches from position 27 to 40 with the N-terminal amino acid sequence determined for a 93 kDa polypeptide that copurifies with the cellulose synthase catalytic subunit during purification of cellulose synthase. The cellulose synthase catalytic subunit gene and the gene encoding the 93 kDa polypeptide, along with other genes probably, are organized as an operon for cellulose biosynthesis in which the first gene is the catalytic subunit gene and the second gene codes for the 93 kDa polypeptide. The function of the 93 kDa polypeptide is not clear at present, however it appears to be tightly associated with the cellulose synthase catalytic subunit. Sequence analysis of the polypeptide shows that it is a membrane protein with a signal sequence at the N-terminal end and a transmembrane helix in the C-terminal region for anchoring it into the membrane.

Amino Acid Sequence↗