Search PubMed⌕ Search

Biomedical subjects

F Y Lin

Publications and source records attributed to F Y Lin.

At least 91 records · Page 5Linked to original sources
PubMed1994

Regression of left ventricular mass after mitral valve repair of pure mitral regurgitation.

To evaluate the effect of mitral valve repair on the regression of left ventricular mass, we studied 50 consecutive patients with severe, pure mitral regurgitation undergoing mitral valve repair. Two-dimensional echocardiograms were recorded a mean 2.5 +/- 2.0 weeks before and 6.5 +/- 2.5 months after valve operation. Postoperative significant mitral regurgitation was present in 3 patients. After mitral valve repair there were significant decreases in left ventricular end-diastolic volume index (133 +/- 39 mL/m2 to 79 +/- 35 mL/m2; p < 0.001), end-systolic volume index (44 +/- 26 mL/m2 to 30 +/- 26 mL/m2; p < 0.001), stroke volume index (89 +/- 29 mL/m2 to 49 +/- 19 mL/m2; p < 0.001), and mass index (211 +/- 82 g/m2 to 134 +/- 52 g/m2; p < 0.001). There also were significant decreases in left atrial dimension (47 +/- 9 mm to 38 +/- 9 mm; p < 0.001), left ventricular end-diastolic dimension (61 +/- 8 mm to 48 +/- 7 mm; p < 0.001), and end-systolic dimension (39 +/- 8 mm to 32 +/- 7 mm; p < 0.001). Left ventricular ejection fraction decreased slightly from 0.69 +/- 0.12 to 0.64 +/- 0.12; p < 0.01) after repair. Thus, correction of pure mitral regurgitation leads to reduction of the cardiac chamber size and left ventricular volumes as well as regression of the left ventricular mass.

Adolescent↗
PubMed1994

Anatomic substrate of the slow atrio-ventricular nodal pathway in an experimental atrio-ventricular nodal reentrant tachycardia.

We investigated the anatomic substrate of the slow pathway of the atrio-ventricular (AV) node in a dog with AV nodal reentrant tachycardia. Sustained AV nodal reentrant tachycardia was repeatedly induced in a mongrel dog after putting cryolesions on the anterior atrial septum for 1 month. A posterior perinodal dissection was performed for ablation of the slow pathway and cure of the tachycardia. After the operation, AV nodal reentrant tachycardia and discontinuity of the AV conduction were no longer demonstrated. A histologic examination of the AV junction revealed that the dissection injured mainly in two areas: (1) the superficial atrial fibers of the subendocardium over the compact AV node; and (2) the inferior portion of the posterior atrial inputs near the tricuspid annulus. The compact AV node and its transitional cells remained intact. In conclusion, our results suggested that (1) the anatomic circuit of AV nodal reentrant tachycardia does involve some extranodal atrial tissues; and (2) the superficial right atrial fibers over the AV node and/or the inferior portion of the posterior atrial inputs, contribute to part of the slow AV nodal pathway.

Animals↗
PubMed1994

Recovery of atrial function after atrial compartment operation for chronic atrial fibrillation in mitral valve disease.

OBJECTIVES: We prospectively studied the recovery of atrial function after atrial compartment operation and mitral valve surgery in patients with chronic atrial fibrillation caused by mitral valve disease. BACKGROUND: Chronic atrial fibrillation is the most common arrhythmia in mitral valve disease. This arrhythmia is associated with excessive morbidity and mortality. Mitral valve surgery alone rarely eliminates it. METHODS: Twenty-two patients underwent mitral valve surgery and a new surgical method, atrial compartment operation. Doppler echocardiography was performed in all patients before operation and at 1 week and 2 and 6 months after operation in the successful cardioversion group. Peak early diastolic (E) and atrial (A) filling velocities, peak A/E velocity ratio and A/E integral ratio of the mitral and tricuspid valves were measured. RESULTS: Sinus rhythm was restored immediately after operation in 91% of patients and was maintained for > 1 week in 15 (68%) of 22 patients and > 6 months in 14 (64%) of 22. Eleven of 15 patients had left atrial paralysis (A/E integral ratio 0) at 1 week and 6 of 14 patients at 2 months. Nine of 15 patients had right atrial paralysis (A/E integral ratio 0) at 1 week and 1 of 14 patients at 2 months. Both left and right atrial contractile function (presence of an A wave on Doppler findings) was detected at 6 months in 14 patients. Mean (+/- SD) peak atrial filling velocity of the mitral valve was 15 +/- 26 cm/s at 1 week, 38 +/- 39 cm/s at 2 months and 93 +/- 32 cm/s at 6 months (p < 0.001). Mean peak atrial filling velocity of the tricuspid valve was 14 +/- 19 cm/s at 1 week, 33 +/- 19 cm/s at 2 months and 50 +/- 19 cm/s at 6 months (p < 0.001). Peak early diastolic and atrial filling velocities, peak A/E velocity ratio and A/E integral ratio of the mitral and tricuspid valves increased significantly from 1 week to 6 months. CONCLUSIONS: Chronic atrial fibrillation in mitral valve disease can often be eliminated by atrial compartment operation. No surgical mortality or significant complications were encountered. Both left and right atrial function, as manifested by Doppler findings, recover after compartment operation and improve over time. The mechanical function of the right atrium recovers earlier than that of the left.

Adolescent↗
PubMed1994

Relationship between ventricular rate and cardiac output in mimic experimental atrial fibrillation.

In treating atrial fibrillation (AF) the goal of ventricular rate reduction is still not determined. An animal model of AF was developed in which the relationship between ventricular rate and the parameters of cardiac function in AF can be studied. To simulate AF, complete heart block was chemically produced on open-chest dogs. Then, assisted by a portable computer, the ventricles were paced with a series of grossly irregular stimuli of predetermined rates, while atria were paced rapidly (500 beats/min). The resulting electrocardiogram and pressure were indistinguishable from the naturally occurring AF. It was found that in AF with ventricular rates that were lower than that of the control state, cardiac output was decreased. Cardiac output increased and reached a plateau when the ventricular rate increased to the level of the control state and then kept stable up to a rate of 320 beats/min. There was a discrepancy between the effective ventricular rate (rate of beats with pulse pressures > or = 25 mmHg in the femoral artery) and the electrical ventricular rate. When the electrical ventricular rate increased over the control ventricular rate the effective ventricular rate did not increase in a parallel manner. Rather, the effective ventricular rate leveled off at the control ventricular rate. This discrepancy may explain the parallel relationship between the effective ventricular rate and cardiac output.

Animals↗
PubMed1994

Effect of EGb 761, a ginkgo biloba extract, on early arrhythmia induced by coronary occlusion and reperfusion in dogs.

EGb 761 is a preparation of Ginkgo biloba extract, which has complex biologic actions including free radical scavenging activity. To examine the anti-arrhythmic effect of EGb 761, a canine preparation of coronary artery occlusion-reperfusion was tested. Under intravenous anesthesia and open chest conditions, 32 dogs were subjected to 30 min of coronary occlusion, followed by reperfusion. Twelve received EGb 761 by intravenous injection, 1 mg/kg five minutes before coronary occlusion, followed by a continuous infusion of 0.1 mg/kg/min until five minutes after reperfusion. Immediately prior to reperfusion, an additional bolus dose of EGb 761 (1 mg/kg) was again injected (group A). The remaining 20 dogs received saline injection, and served as the control (group B). The electrocardiographic changes were recorded during the whole experimental course. The results showed that, during coronary occlusion, group A dogs had a lower count of ventricular premature beats than group B dogs. However, there was no difference in the incidence of ventricular tachycardia (VT) between the two groups. The duration of VT of the treated dogs was similar to that of the control dogs. The incidence of ventricular fibrillation (VF) was also similar. Upon reperfusion, the treated dogs were shown to be protected from VF. The duration of VT was also shorter in the treated group, although the incidence of VT was not different between the two groups. EGb 761 is effective in preventing early VF induced by coronary reperfusion while ineffective in protecting the ischemic VT and VF.

Animals↗
PubMed1994

Separation of thoracopagus conjoined twins. A case report.

A pair of thoracopagus conjoined twins with a connection at the atrioventricular groove of both hearts and a huge conjoined liver were surgically separated. An aortopulmonary shunt was created for Twin B, a victim of complex congenital heart disease with hypoplastic right heart syndrome, who died 5 hours later. However, Twin A survived after prolonged endotracheal intubation and parenteral nutrition. He survived for 7 months, and went home, but finally died of sepsis. In reviewing 47 pairs of surgically separated thoracopagus conjoined twins, in 30 pairs of type A (Leachman's classification, completely separate hearts), 42 patients survived (70%); in 5 pairs of type B (atrial connection only), one patient survived (10%); in 9 pairs of type C (both atrial and ventricular interconnections), none survived; in 3 pairs of unknown type, 2 survived. Total survival rate of surgically separated thoracopagus conjoined twins was 47.9%. The survival rate was 38.2% in those operated in the neonatal period (n = 34) and 63.6% in those operated over 1 month of age (n = 44) (p = 0.016). In conclusion, thoracopagus conjoined twins are rare. Although its separation carries a high risk, especially in those with cardiac connection, this report confirmed that separation is still feasible under proper preparation and planning.

Electrocardiography↗
PubMed1994

Hyperbilirubinemia after cardiac operation. Incidence, risk factors, and clinical significance.

Three hundred and two consecutive patients who had undergone cardiac operation for various cardiac lesions were studied prospectively to evaluate the incidence, risk factors, and the associated mortality of postoperative hyperbilirubinemia after cardiopulmonary bypass. Concentrations of the serum total (conjugated and unconjugated) bilirubin, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, albumin, globulin, and serum haptoglobin were measured before the operation and again on the first, second, and seventh postoperative days. Postoperative hyperbilirubinemia was defined as occurrence of a serum total bilirubin concentration of more than 3 mg/dl in any measurement during the postoperative period. Logistic regression was done to identify possible risk factors for postoperative hyperbilirubinemia. Overall incidence of postoperative hyperbilirubinemia was 35.1%; the incidence of postoperative hyperbilirubinemia was higher in patients whose valves were replaced with mechanical prostheses than in those without prostheses (p < 0.00001). In patients with postoperative hyperbilirubinemia, 70% of the increase of total bilirubin on the first postoperative day came about from an increase in unconjugated bilirubin. Serum haptoglobin decreased significantly at the same time (p < 0.01). Development of the postoperative hyperbilirubinemia was associated with a higher mortality (5.6% versus 0.5%, p < 0.01) and higher frequency of use of intraaortic balloon counterpulsation, especially for patients in whom the highest postoperative total bilirubin occurred after the first 2 days. The numbers of valves replaced, preoperative right atrial pressure, and preoperative total bilirubin concentration are the significant risk factors that, in combination, correctly predict the occurrence of postoperative hyperbilirubinemia in 80% of the patients. We concluded that postoperative hyperbilirubinemia results mainly from an increase in unconjugated bilirubin and is associated with higher mortality, especially for patients in whom highest postoperative total bilirubin occurred late after operation. Patients with the higher preoperative right atrial pressure and total bilirubin level who then underwent multiple valve replacement procedures are at greater risk for development of postoperative hyperbilirubinemia.

Cardiac Surgical Procedures↗
PubMed1994

Surgical ablation of Wolff-Parkinson-White syndrome in children and young adults.

From 1988 to 1991, nine patients with structural normal heart, aged 10 to 23 (median 13 years), Wolff-Parkinson-White Syndrome patients were operated at National Taiwan University Hospital. The diagnosis was established by surface electrocardiograms recorded during sinus rhythm and tachycardia, and by complete cardiac electrophysiologic studies. The location of accessory pathways (AP) were: 4 left lateral, 3 right lateral, 1 right posteroseptal and 1 right anteroseptal AV groove. In all 6 patients with manifest WPW syndrome, the location of AP could be correctly predicted by the surface EKG delta wave polarity. In all 9 patients with WPW syndrome, intraoperative epicardial and endocardial mappings confirmed their location. Wide endocardial dissection were undertaken. No surgical morbidities or mortality was encountered except in one case which developed transient postpericardiotomy syndrome. During the follow-up (2 to 4 years), all of them were in sinus rhythm, drug free and tachycardia free. In conclusion, (a) the sites of AP and the arrhythmia mechanisms can be reliably predicted by surface EKG and catheter mapping techniques; (b) surgical cure of supraventricular tachycardia could be achieved safely in children; and (c) surgical ablation still is indicated when catheter ablation is unsuccessful, or when coexistent complex cardiac pathology requires surgical intervention in small children.

Adolescent↗
PubMed1993

Experimentally created atrioventricular node reentrant tachycardia in the dog: evidence of a brake system for nodal reentry in the anterior interatrial septum.

OBJECTIVES: The purpose of the study was to investigate the hypothesis that nodal approaches of both anterior and posterior atrial input sites of the atrioventricular (AV) node contribute to part of the circuit of AV node reentrant tachycardia. Thus, tachycardia might be elicited by a premature atrial impulse that arrived at the AV node through one input site while blocked at another. BACKGROUND: Atrioventricular node reentrant tachycardia is the most common supraventricular tachycardia in humans, yet the exact pathway of the reentrant circuit is unknown. METHODS: In eight dogs, an operation that blocked atrial impulses from the anterior input site to the AV node was performed through a right thoracotomy with the inflow occlusion method. The right atrial free wall and the anterior atrial septum between the sinoatrial node and the AV node were completely divided, whereas the tissues within the triangle of Koch remained intact. Thus, atrial impulses were blocked from the anterior input site in the right atrium and the atrial septum and were conducted only through the left atrial free wall to the posterior atrial septum into the AV node. RESULTS: In a baseline electrophysiologic study before operation, dual AV conduction pathways were demonstrated in seven of eight dogs, but none of the seven had inducible AV node reentrant tachycardia. A repeat study 1 week postoperatively revealed that 1) both PR and AH intervals were prolonged during sinus rhythm (p < 0.01); 2) anterograde and retrograde conduction of the AV node showed no significant changes; and 3) AV node reentrant tachycardia was induced in four dogs (50%), of which three had sustained tachycardia. CONCLUSIONS: These results are compatible with the hypothesis that both nodal approaches of atrial input sites of the AV node contribute to part of the circuit of AV node reentrant tachycardia. They also confirm Moe's hypothesis of the existence of a brake system that prevents sustained AV node reentry. Our data suggest that the brake system is located in the anterior atrial septum.

Animals↗
PubMed1993

Diagnostic accuracy of transesophageal echocardiography for detecting left atrial thrombi in patients with rheumatic heart disease having undergone mitral valve operations.

Transesophageal echocardiography (TEE) has emerged as an efficient method for detecting left atrial (LA) thrombi in recent years, but its accuracy has not been fully evaluated. A prospective clinicopathologic study in 213 consecutive patients with chronic rheumatic mitral valve disease over a period of 39 months was undertaken. All patients underwent open heart surgery within 3 days after the TEE study. The presence or absence of LA thrombi was confirmed at surgery by direct inspection of the left atrium and proven by histopathologic examination. Of the 213 patients, 147 had predominant mitral stenosis, and the remaining 66 patients had significant mitral regurgitation. Twenty-eight patients had LA thrombi by TEE criteria. These findings were all confirmed at surgicopathologic studies (specificity 100%). However, in 2 patients, LA thrombi were present but could not be detected by TEE (sensitivity 93.3%). Therefore, the positive predictive value was 100%, the negative predictive value was 98.9% and the diagnostic accuracy was 99.1%. No thrombi were found in patients with significant mitral regurgitation. The frequency of LA thrombi in patients with predominant mitral stenosis was 20% (30 of 147), and most of these patients had chronic atrial fibrillation (28 of 30, 93%). Only 16 patients (16 of 30, 53%) were found to have LA thrombi by transthoracic echocardiography. Furthermore, our data showed poor correlation between the echogenicity of LA thrombi and the degree of thrombus organization. Thus, TEE is excellent for detecting LA thrombi in patients with rheumatic heart disease severe enough to warrant mitral valve operations.

Adolescent↗
PubMed1993

Characterization and seroepidemiology of a type 5 astrovirus associated with an outbreak of gastroenteritis in Marin County, California.

The Marin County strain of type 5 astrovirus was associated with two separate outbreaks of nonbacterial gastroenteritis in California in 1978. A safety-tested, bacterium-free filtrate prepared from a stool specimen of an individual who was ill during the original outbreak was given orally to 19 adult volunteers. One volunteer developed a gastrointestinal illness, and nine had serologic responses. Several diarrheal stool specimens from the ill volunteer contained a large number of 27-nm particles. By using immune electron microscopy with acute- and convalescent-phase sera from the original outbreak, these 27-nm particles were shown to be identical to the viral inoculum. The Marin County virus, purified from the stool of the ill volunteer, was shown by immunoprecipitation and polyacrylamide gel electrophoresis to contain a single structural protein with a molecular weight of 30,000. The buoyant density of the virion was 1.39 g/cm3 in cesium chloride. By electron microscopy, approximately 5% of the particles had the characteristic stellate configuration of astrovirus, and serologic studies by immunofluorescence technique confirmed previous classification of the Marin County virus as a type 5 astrovirus. Radioimmunoassay and biotin-avidin immunoassay were used to detect antibody to the Marin County virus in paired acute- and convalescent-phase sera from 32 outbreaks of nonbacterial gastroenteritis, but none of these outbreaks could be attributed to this virus. Prevalence of antibody to this strain of astrovirus was approximately 13% in children 6 months to 3 years of age and increased to 41% in older children and young adults.

Acute Disease↗
PubMed1992

Characteristic abnormal features of body surface potential maps predictive of ventricular tachycardia following coronary artery occlusion in dogs.

In a search for features predictive of ventricular arrhythmias in myocardial ischemia, the body surface potential maps of 17 dogs with coronary artery occlusion were studied. Ventricular tachycardia occurred in 9 (53%) of the 17 dogs. Multiple distribution of the abnormal potential minimum was found in 6 (67%) of the 9 dogs with (group A) and none of the 8 dogs without ventricular tachycardia (group B). The difference was statistically significant (p less than 0.01). The abnormal "early reversal" phenomenon of potential distribution was observed in 6 (67%) of group A and 7 (88%) of group B. The difference was not statistically significant (p greater than 0.05). The area of abnormal negative potential was 28.0 +/- 8.5 cm2 for group A and 14.5 +/- 5.5 cm2 for group B (p less than 0.001). The abnormal negative potential lasted for 25.4 +/- 3.5 ms in group A and 10.1 +/- 5.1 ms in group B (p less than 0.001). The abnormally early appearance of potential minimum lasted for 24.2 +/- 5.1 ms in group A and 10.5 +/- 5.4 ms in group B (p less than 0.001). The data suggest that the distribution, area, and duration of the abnormal negative potential of the body surface potential map are useful in the prediction of ventricular tachycardia associated with coronary artery occlusion.

Animals↗
PubMed1992

Detection of patent foramen ovale by contrast transesophageal echocardiography.

A series of 32 patients undergoing cardiac catheterization and/or operation to document the presence of patent foramen ovale (PFO) were studied. All were examined by contrast transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) during normal breathing and the Valsalva maneuver. A right-to-left shunt at the atrial level was visualized by contrast TEE in 14 patients during normal breathing and in 20 patients during the Valsalva maneuver. In comparison, contrast TTE revealed this shunt in only eight patients during normal breathing and in 12 patients during the Valsalva maneuver. All of the foramina proved to be patent by contrast TTE were also found by contrast TEE. All but one (19 of 20) patients, shown to have PFO by contrast TEE, could be confirmed at cardiac catheterization and/or operation. Using cardiac catheterization and/or operation as a gold standard, contrast TEE appears to be a more sensitive (100 percent vs 63 percent, p less than 0.005) and accurate (97 percent vs 78 percent, p less than 0.05) method than contrast TTE in the detection of PFO.

Adolescent↗
PubMed1992

Open heart surgery in geriatric patients.

With the progress of medical science, the scope of open heart surgery has expanded. From 1975 through 1987, we operated on 114 consecutive patients aged 65 years and over with the aid of a cardiopulmonary bypass in the Department of Surgery, National Taiwan University Hospital. The annual number of these elderly patients has increased gradually, reaching 6.4% of the annual open heart cases in 1987. Eighty-six of our 114 patients were males and 28 were females. Their ages ranged from 65 to 88 years with an average of 68.5 years. Overall, 65 patients (57%) were operated on for coronary artery disease and/or its associated lesions; 41 (36%), for valvular heart disease; six, for aortic dissection; two, for cardiac tumor; and one, for congenital pulmonary stenosis. One patient had combined coronary artery disease and aortic dissection. The mortality for isolated coronary artery bypass surgery was 12%; for single valvular surgery it was 11%. The complexity of the surgical procedure increased the operative mortality. The overall mortality was 23.6% (27/114), with subsequent death in 5.7% during an average of 25 months of follow-up. Because of the degeneration of organ-systems in elderly patients, and its frequent association with poor cardiac reserve and other medical problems, these elderly cardiac patients should be checked thoroughly before they are considered for open heart surgery. Our experience suggests that open heart surgery can be done in selected patients aged 65 years or older with acceptable risks. Age alone should not be an absolute contraindication to surgery, and clinical improvement is to be expected after surgery.

Age Factors↗
PubMed1991

[Treatment with new surgical method for chronic atrial fibrillation in 5 cases with mitral valve disease].

Chronic atrial fibrillation is the most common arrhythmia in patients with mitral valve disease, it not only deteriorates cardiac output, but also promotes a 5.6 times higher incidence of thromboembolic events. Nevertheless, the exact mechanism of atrial fibrillation is still poorly understood. Moreover, the long-term results of treatment, either by drugs or cardioversion, are almost always disappointing. Recent investigations suggest that atrial fibrillation is probably due to intraatrial multiple reentrant waves. It is also well-known from animal experiments that for sustenance of the fibrillation a critical mass of atrium is necessary. Based on these data, a new surgical method has been carefully designed to reduce atrial mass and to prevent sustenance of fibrillation. Between July and December 1988, five patients, one male and four females, with mitral valve disease and chronic atrial fibrillation were selected for this new surgical method. The age distribution ranged from 25 to 57 years, with a mean of 36 +/- 13 years. All of them had chronic atrial fibrillation which had been documented for more than one year. The operation was performed using the cardiopulmonary bypass and cardioplegia myocardial protection techniques. The left atrium was opened via the interatrial sulcus. After the mitral valve was repaired, cryosurgery (-60 degrees C for 120 sec) was applied along the borders of the left atrial free-wall. The left atrium was separated by these cryolesions into two sections, each about half the mass of the original and both sections were connected with a few atrial fibers located behind the coronary sinus. No surgical mortality or complications were encountered.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Effects of linolenic acid on the canine heart.

Disturbances in lipid metabolism have been observed during the early phase of acute myocardial ischemia. Accumulation of fatty acids in and around the ischemic cardiac cells has been implicated to play a role in both contractile and electrophysiological abnormalities. Linolenic acid is an essential fatty acid and constitutes the phospholipid moiety of the cell membrane. The purpose of this work was to study the effects of linolenic acid on the heart using canine preparations. A direct left atrial injection was used as the route of administration because intravenous injections of linolenic acid inevitably cause pulmonary edema. A surface lead electrocardiogram (ECG), an epicardial electrogram, femoral arterial pressure, left ventricular pressure and its time derivative (dp/dt) were recorded before and after drug administration. Various dosages of linolenic acid (1 mg, 5 mg, 10 mg, 20 mg, 30 mg and 60 mg/kg) and a control buffer solution were tested. The results showed that linolenic acid has a potent dose-dependent bradycardic and myocardial depression effect starting from a dose of 5 mg/kg (delta HR = -20.1 +/- 4.0 bpm, delta dp/dt = 364.3 +/- 66.0 mmHg, sec-1, p less than 0.01 vs. control). At a high dose of 30 mg/kg, linolenic acid induced premature ventricular complexes. Furthermore, ventricular tachycardia was observed in 5 of the 8 dogs (62.5%) receiving the high dose of 60 mg/kg. We conclude that linolenic acid has profound effects on the canine heart; at a low dose, it causes bradycardia and myocardial depression, while at a high dose, it also produces ventricular irritability.

Animals↗