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Biomedical subjects

F C Lin

Publications and source records attributed to F C Lin.

At least 19 recordsLinked to original sources
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↗
PubMed1991

Repetitive sinoatrial exit block as the major mechanism of drug-provoked long sinus or atrial pause.

Prolonged sinus or atrial pause occurred in six patients with paroxysmal supraventricular tachycardia after drug administration. All six patients had normal sinus node function during control electrophysiologic study; the sinus cycle length ranged from 510 to 900 ms (mean 743 +/- 141) and the longest sinus node recovery time ranged from 800 to 1,230 ms (mean 1,018 +/- 168). A long sinus or atrial pause occurring at the termination of tachycardia or cessation of atrial pacing, ranging from 3,100 to 8,200 ms (mean 6,270 +/- 1,674), was provoked by the administration of various drugs. These included an intravenous bolus injection of adenosine triphosphate (5 mg; one patient), intravenous bolus injection of verapamil (5 mg; one patient), a combination of a single oral dose of diltiazem (120 mg) and propranolol (20 to 40 mg; three patients), oral diltiazem (240 mg/day; one patient) and a combination of oral diltiazem (240 mg/day) and propranolol (160 mg/day; one patient). In five patients, low frequency deflections suggestive of sinus node activity with a cycle length between 620 and 3,500 ms were recorded during pauses. These findings suggest that repetitive sinoatrial exit block was responsible for the pause. Sinus slowing with a long arrest suggesting suppression of sinus automaticity was also noted in three of these five patients; the longest sinus arrest in these three patients was 4,160, 4,800 and greater than 4,910 ms, respectively. The remaining patient with a pause of 6,840 ms had no recordable sinus activity, either reflecting suppression of sinus automaticity or technical failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

Familial patent ductus arteriosus. Report of a family.

Three female patients of two generations in one family each had patent ductus arteriosus (PDA) that was proved by echocardiography and cardiac catheterization. Two of them received surgical ligation of the PDA because of large left to right shunt (Qp/Qs of 3.8 and 2.7, respectively), while the third patient with a Qp/Qs of 1.2 was not operated. Although the exact cause of PDA in this family is unclear, an autosomal recessive inheritance is highly possible.

Child↗
PubMed1990

Effects of isoproterenol on accessory pathway conduction in intermittent or concealed Wolff-Parkinson-White syndrome.

The effects of isoproterenol on accessory pathway conduction were evaluated in 24 patients with intermittent and 60 patients with concealed pre-excitation, using atrial and ventricular incremental and extrastimulus testing techniques. The atrial paced cycle length that induced block in the accessory pathway could be compared in 11 of the 24 patients with intermittent preexcitation before and after isoproterenol; it decreased from 622 +/- 212 ms to 408 +/- 128 ms (mean +/- standard deviation) after isoproterenol (p less than 0.01). The anterograde effective refractory period of the accessory pathway could be compared in 5 patients before and after isoproterenol; it decreased from 460 +/- 131 to 310 +/- 48 ms after isoproterenol (p less than 0.01). None of the 60 patients with concealed preexcitation showed ventricular preexcitation with isoproterenol infusion. Eighty-one of the 84 patients had clinically documented supraventricular tachycardia, suggesting the accessory pathway was capable of retrograde conduction. Retrograde study was performed in all 84 patients; 83 had retrograde conduction and the other had no retrograde conduction before and after isoproterenol. The ventricular paced cycle length that induced block in the accessory pathway could be compared in 38 patients before and after isoproterenol; it decreased from 342 +/- 71 to 296 +/- 39 ms after isoproterenol (p less than 0.001). The retrograde effective refractory period of the accessory pathway could be compared in 56 patients; it decreased from 293 +/- 76 to 238 +/- 36 ms after isoproterenol (p less than 0.001). In conclusion, isoproterenol facilitates anterograde and retrograde accessory pathway conduction, but the facilitation of anterograde conduction occurs only in those capable of spontaneous conduction.

Adolescent↗
PubMed1990

Identification of the uridine 5'-diphosphoglucose (UDP-Glc) binding subunit of cellulose synthase in Acetobacter xylinum using the photoaffinity probe 5-azido-UDP-Glc.

Photoaffinity labeling of purified cellulose synthase with [beta-32P]5-azidouridine 5'-diphosphoglucose (UDP-Glc) has been used to identify the UDP-Glc binding subunit of the cellulose synthase from Acetobacter xylinum strain ATCC 53582. The results showed exclusive labeling of an 83-kDa polypeptide. Photoinsertion of [beta-32P]5-azido-UDP-Glc is stimulated by the cellulose synthase activator, bis-(3'----5') cyclic diguanylic acid. Addition of increasing amounts of UDP-Glc prevents photolabeling of the 83-kDa polypeptide. The reversible and photocatalyzed binding of this photoprobe also showed saturation kinetics. These studies demonstrate that the 83-kDa polypeptide is the catalytic subunit of the cellulose synthase in A. xylinum strain ATCC 53582.

Affinity Labels↗
PubMed1990

Cloning and sequencing of the cellulose synthase catalytic subunit gene of Acetobacter xylinum.

The gene for the catalytic subunit of cellulose synthase from Acetobacter xylinum has been cloned by using an oligonucleotide probe designed from the N-terminal amino acid sequence of the catalytic subunit (an 83 kDa polypeptide) of the cellulose synthase purified from trypsin-treated membranes of A. xylinum. The gene was located on a 9.5 kb Hind III fragment of A. xylinum DNA that was cloned in the plasmid pUC18. DNA sequencing of approximately 3 kb of the Hind III fragment led to the identification of an open reading frame of 2169 base pairs coding for a polypeptide of 80 kDa. Fifteen amino acids in the N-terminal region (positions 6 to 20) of the amino acid sequence, deduced from the DNA sequence, match with the N-terminal amino acid sequence obtained for the 83 kDa polypeptide, confirming that the DNA sequence cloned codes for the catalytic subunit of cellulose synthase which transfers glucose from UDP-glucose to the growing glucan chain. Trypsin treatment of membranes during purification of the 83 kDa polypeptide cleaved the first 5 amino acids at the N-terminal end of this polypeptide as observed from the deduced amino acid sequence, and also from sequencing of the 83 kDa polypeptide purified from membranes that were not treated with trypsin. Sequence analysis suggests that the cellulose synthase catalytic subunit is an integral membrane protein with 6 transmembrane segments. There is no signal sequence and it is postulated that the protein is anchored in the membrane at the N-terminal end by a single hydrophobic helix. Two potential N-glycosylation sites are predicted from the sequence analysis, and this is in agreement with the earlier observations that the 83 kDa polypeptide is a glycoprotein. The cloned gene is conserved among a number of A. xylinum strains, as determined by Southern hybridization.

Amino Acid Sequence↗
PubMed1990

Participation of a concealed nodoventricular fiber in the genesis of paroxysmal tachycardias.

An unusual form of tachycardia circuit is described. The circuit incorporates a concealed nodoventricular fiber that conducts in a retrograde path, connects the atrioventricular node and the right ventricle, and also includes the distal portion of the atrioventricular node, the His-Purkinje system, and the ventricle. The study patient was first seen with paroxysmal tachycardias of normal QRS duration, complete right bundle branch block, and complete left bundle branch block. Electrophysiologic studies disclosed poor anterograde atrioventricular nodal conduction with a block proximal to His deflection that occurred at an atrial paced cycle length of 600 msec with no ventriculoatrial conduction. The tachycardias were inducible with two ventricular extrastimuli, had a His deflection that preceded each QRS complex and an HV interval identical to that during sinus rhythm, and revealed ventriculoatrial dissociation. Tachycardia with QRS patterns of right bundle branch block had a cycle 30 to 35 msec longer than tachycardias with either normal QRS duration or complete left bundle branch block. Tachycardias could be entrained by appropriate right ventricular pacing at rates slightly faster than the rate of tachycardia. Tachycardias could be terminated abruptly by an intravenous bolus of either adenosine triphosphate or verapamil.

Bundle-Branch Block↗
PubMed1990

Atrioventricular block in the atypical form of junctional reciprocating tachycardia: evidence supporting the atrioventricular node as the site of reentry.

Serial electrophysiologic studies were performed in 19 patients with the atypical form of supraventricular tachycardia having a long RP and short PR interval. In all 19 patients, supraventricular tachycardia was found to have a 1:1 P-QRS relation during initial control electrophysiologic studies, and in all 19 patients, electrophysiologic studies suggested that junctional reentry was the mechanism of supraventricular tachycardia. Seven of the 19 patients developed atrioventricular (AV) block during initiation of supraventricular tachycardia or after induction of supraventricular tachycardia following various drug administrations in subsequent studies. In three patients, second degree block within the His bundle or block distal to the His bundle recording site occurred after administration of quinidine. In one patient it occurred after procainamide, and in another patient it occurred after atropine. In one patient, 2:1 block proximal to the His deflection occurred after verapamil. In the remaining patient, a transient Wenckebach block proximal to the His deflection was noted after adenosine triphosphate. In this latter patient, 2:1 AV block was also noted after propranolol and digoxin. The site of reentry in these seven patients with AV block during supraventricular tachycardia was confined to the AV node area. Their supraventricular tachycardia did not involve a slowly conducting paraseptal accessory pathway because the distal AV node, His bundle and ventricle were not found to be necessary links in the tachycardia circuit.

Adolescent↗