Search PubMed⌕ Search

Biomedical subjects

J L Lin

Publications and source records attributed to J L Lin.

At least 91 records · Page 5Linked to original sources
PubMed1997

Mechanisms underlying different surface ECG morphologies of recurrent monomorphic ventricular tachycardia and their modification by procainamide.

INTRODUCTION: Distinct surface ECG morphologies (ECGMs), from one episode to the next, of recurrent monomorphic ventricular tachycardia (VT) in the same patient complicate endocardial catheter mapping and the success of ablative therapy. This study investigates the incidence and mechanisms of multiple ECGMs during recurrent monomorphic VTs in a canine model of experimental myocardial infarction (MI). METHODS AND RESULTS: Computerized ECG analysis and simultaneous endocardial and epicardial activation mapping with a 64 bipolar electrode array were used to analyze the relation between site of VT origin, local activation sequence, and surface ECGM in 72 VT episodes induced in 9 of 17 dogs with experimental MI. Pairwise comparisons of all VTs induced in the same animal were done in drug-free state (47 VTs) and after intravenous procainamide (25 VTs). In drug-free state, VT pairs with similar surface ECGMs manifested endocardial breakthrough sites (BSs) within a distance < 10 mm in 46 (100%) of 46 VT pairs compared to 43 (45%) of 95 VT pairs with different surface ECGMs (P < 0.0001). Of all 89 VT pairs with endocardial BSs within < 10 mm, similar endocardial activation patterns were found in 34 (74%) of 46 pairs with similar ECGMs in contrast to 6 (14%) of 43 pairs with different ECGMs (P < 0.001). Similar comparisons of VT pairs induced after intravenous procainamide administration showed that the endocardial BSs were located within < 10 mm in 9 (75%) of 12 VT pairs with similar and in 17 (49%) of 95 with different surface ECGMs, respectively (P = NS). CONCLUSIONS: In the same heart, similar surface ECGMs of recurrent VT are highly predictive of closely spaced endocardial BSs in drug-free state, but not after procainamide administration. Nearly half of the VTs with different surface ECGMs still originate from closely spaced endocardial BSs but commonly manifest a change in the endocardial activation spread from this site. Thus, assumptions about different mechanisms and sites of VT origin based on different surface ECGMs should be made with caution.

Animals↗
PubMed1997

Use of jugular venous blood, compared with mixed venous blood, for measurement of venous oxygenation indices in a porcine model of endotoxic shock.

OBJECTIVE: To evaluate the reliability of oxygen saturation and oxygen content values measured from jugular venous blood in estimating values measured from mixed venous blood during endotoxic shock. ANIMALS: 14 random-bred 10- to 15-kg Yorkshire pigs. PROCEDURE: 60 pairs of heparinized blood samples were simultaneously collected from the pulmonary artery and right jugular vein during an independent study, using a porcine model of endotoxic shock. Endotoxic shock was induced by infusion of Escherichia coli endotoxin. Eighteen of the sample pairs were obtained from pigs prior to infusion of endotoxin or from control pigs. Oxygen saturation and venous oxygen content were measured by direct oximetry. Analysis of bias and precision was used to compare jugular venous blood values with values obtained from mixed venous blood. Samples from endotoxemic pigs were subclassified on the basis of abnormal states of global oxygen imbalance associated with septic shock. RESULTS: Indices of venous oxygenation measured from jugular venous blood were an imprecise method of estimating values measured from mixed venous blood. There was no significant difference in bias between nonendotoxemic and endotoxemic pigs, regardless of abnormal hemodynamic states. CONCLUSION: Jugular venous blood oxygen saturation and oxygen content values should not be used to assess global oxygen transport during endotoxic shock.

Analysis of Variance↗
PubMed1996

Left atrial appendage blood flow in a case of persistent atrial standstill.

Persistent atrial standstill, characterized by absence of atrial activity on surface and intracavitary electrograms, absence of atrial mechanical activity, and inability to stimulate the atria electrically, is a rare disorder. Left atrial appendage blood flow has been reported to be related to P wave during sinus rhythm or local atrial electrogram during atrial fibrillation. However, distinct and periodical LAA blood flow was demonstrated in a patient with persistent atrial standstill by transesophageal echocardiography.

Atrial Function↗
PubMed1996

Importance of left atrial appendage function as a risk factor for systemic thromboembolism in patients with rheumatic mitral valve disease.

One hundred fifty-six patients with rheumatic mitral valve disease were studied with transesophageal echocardiography to assess the influence of left atrial (LA) appendage size and contractile function on the occurrence of systemic embolism. LA appendage function, represented by peak emptying velocity, was found to be a better indicator than LA spontaneous echo contrast as a risk factor for systemic thromboembolism.

Adult↗
PubMed1996

Differential displaying of mRNAs from the atrioventricular region of developing chicken hearts at stages 15 and 21.

In an effort to isolate novel genes that may be involved in the development of the cardiac cushions and then the formation of cardiac valves and septa, we utilized the differential mRNA display method in conjunction with the whole-mount in situ hybridization. The total RNAs used to differentially display were prepared from atrioventricular (AV) canal regions of stage 15 and stage 21 chicken hearts because critical events known to be important for the AV valve and septum formation occur during this period of the development. We have successfully obtained 14 potential candidate genes. Three examples, 15H16 (phospholamban), E13 (skeletal alpha-tropomyosin) and 21C (a novel gene), are discussed here. Levels of mRNA expression in developing hearts were determined by Northern blot analysis and their expression patterns were revealed and compared using whole-mount in situ hybridization. Both phospholamban and skeletal alpha-tropomyosin messages in the myocardium of the AV canal region showed significant decrease during this period of the development. The 21C differential display product detects a novel 9.5 Kb message whose expression is cardiac-specific at early stages of development. The expression level of the 21C gene appeared to be increased from stage 15 to stages 21 and 25 as determined by both Northern blot analysis and in situ hybridization. From these data, we demonstrate that the differential display method together with the whole-mount in situ hybridization could be an effective means for the isolation of novel and differentially expressed genes.

Animals↗
PubMed1996

Overexpression of microfilament-stabilizing human caldesmon fragment, CaD39, affects cell attachment, spreading, and cytokinesis.

Previous studies have demonstrated that overexpression of the carboxyl-terminal fragment, CaD39, of human fibroblast caldesmon in Chinese hamster ovary cells protected endogenous tropomyosin from turnover and stabilized actin microfilament bundles [Warren et al., 1994: J. Cell Biol. 125:359-368]. To assess the consequences of having CaD39-stabilized microfilaments in living cell, we characterized the motile behaviors of stable CaD39-expressing lines. We here found that CaD39-expressing cells adhered faster to plastic, glass, fibronectin-coated glass, and collagen-coated glass than control cells. Moreover, the CaD39-expressing cells also exhibited enhanced spreading immediately after attachment. Despite these differences, overexpression of CaD39 had little effect on the velocity of intracellular granule movement, or the velocity and persistence of cellular translocation. However, CaD39-expressing cells were more elongate and encompassed less area than non-expressing cells during migration in a wound-healing assay. In interphase cells, the expressed CaD39 fragments were found associated with tropomyosin-enriched microfilaments. Like endogenous caldesmon, the CaD39 fragment was also modified at mitosis. Although a significant portion of CaD39 underwent only partial modification, the majority of the CaD39 was released from the microfilaments during mitosis. This is consistent with the finding that the CaD39-induced advantage for attachment and spreading was lost during mitosis. In CaD39-expressing cells, an incomplete release of the CaD39 from microfilaments at mitosis was found which may be responsible for the increase in the frequency of multinuclear cells in CaD39-expressing lines.

Actin Cytoskeleton↗
PubMed1996

Influence of radiofrequency catheter ablation on myocardial metabolism.

We investigated the change of the arterial-coronary sinus lactate difference before and after radiofrequency ablation to assess the influence of radiofrequency ablation on myocardial metabolism. Sixteen patients underwent radiofrequency catheter ablation and blood sampling. The patients were further divided into two groups according to the energy received, group 1 (n = 8) with lower energy and group 2 (n = 8) with higher energy. The postpacing arterial-coronary sinus lactate difference was significantly higher than that 1 min after ablation (0.18 +/- 0.16 vs. -0.08 +/- 0.14 mmol/l, P < 0.01). The mean arterial-coronary sinus lactate difference obtained at 3 min, 5 min and 10 min increased gradually and finally approximated the postpacing lactate difference. The arterial-coronary sinus lactate difference 1 min after ablation of group 2 was significantly lower than that of group 1 (-0.03 +/- 0.14 vs. -0.13 +/- 0.14 mmol/l, P < 0.01). The arterial coronary sinus lactate differences of group 2 obtained at 3 min, 5 min and 10 min were also lower than those of group 1. However, the difference between the two groups decreased with time. This finding suggests that radiofrequency energy has an influence on the myocardial metabolism and higher energy causes more metabolic alteration than lower energy.

Adult↗
PubMed1996

Atrial compartment surgery for chronic atrial fibrillation associated with congenital heart defects.

In three adult patients, two with atrial septal defect and one with Ebstein's anomaly, chronic atrial fibrillation was documented for 13, 21, and 3 years, respectively. Atrial compartment surgery was performed for ablation of the atrial fibrillation concomitant with repair of the cardiac defects. The operation was performed with traditional cardiopulmonary bypass and crystalloid cardioplegia myocardial protection. A U-shaped incision was made in the right atrium: a longitudinal incision 1 cm lateral and parallel to the sulcus terminalis, extending along the borders of the atrial septum to 3 cm (upper margin) and 1 cm (lower margin) distant to the tricuspid anulus. Cryolesions of the atrial isthmus between the upper incision margin and the tricuspid valve anulus were created at -60 degrees C for 180 seconds at a time. After the operation, all three patients had restored and maintained normal sinus rhythm during follow-up periods of 32, 16, and 3 months. Doppler echocardiography detected the recovery of atrial contractility in all three patients. Atrial compartment surgery is a simple and effective method for elimination of chronic atrial fibrillation associated with congenital heart defects.

Adult↗
PubMed1996

QTc prolongation indicates a poor prognosis in patients with organophosphate poisoning.

This study reviewed emergency department electrocardiograms of 223 patients with organophosphate poisoning from January 1982 to June 1994: 97 (43.5%) had QTc prolongation and were placed in group A; 126 patients without QTc prolongation were designated as group B. Compared with group B, group A patients had a higher mortality (19.6% v 4.8%, P < .001) and a higher incidence of respiratory failure (56.7% v 20.6%, P < .001). Serum cholinesterase levels were determined in the 223 patients: 92 (41.3%) were classified as severe poisoning. 32 (14.3%) as moderate, 41 (18.1%) as mild, and 58 (25.7%) as very mild. The severe group had a high incidence of QTc prolongation (P < .001), a high incidence of respiratory failure (P < 0.001), and a higher mortality rate (P < 0.001) than the other groups. Of the QTc prolongation patients, 59.8% (55/92) had a high incidence of respiratory failure (78.2% v 35.1%, P < .0001) and a higher mortality rate (29.1% v 8.1%, P < 0.05) compared with 40.2% (37/92) of the patients without QTc prolongation in the severe group. In conclusion, a complete electrocardiogram at the emergency department is important and of prognostic value.

Adolescent↗
PubMed1996

Aluminium-containing agents may be toxic in predialysis chronic renal insufficiency patients.

OBJECTIVE: To investigate the possible toxic effects of long-term low dose aluminium (Al) exposure in predialysis chronic renal insufficiency (CRI) patients (serum creatinine > 1.4 mg dL-1). DESIGN: An open, random, and prospective clinical study. SETTING: The study was carried out at Chang Gung Memorial Hospital, a medical centre of Chang Gung Medical College. SUBJECTS: Seventy CRI patients who have regularly attended a nephrology out-patient department participated in this study. After a 3-month wash-out period 50 were given an Al loading test and 20 received no Al-containing agents. INTERVENTIONS: We used a low dose of Al(OH)3 (one tablet three times day-1, about 302 mg aluminium day-1) for 3 months as an Al loading test. MAIN OUTCOME MEASURES: The study was divided into two phases: phase 1. a basal study to measure serum Al, iron, ferritin, daily urinary Al excretion and renal function status; and phase 2, in which an Al loading test was performed. The phase 1 parameters were measured again after the Al loading test to compare the differences between pre- and post-study in the two groups. RESULTS: We found significant increments of serum Al and daily urinary Al excretion in all study group patients after the Al loading test. The increments of serum Al correlated with basal creatinine clearance (Ccr: r = -0.352, P < 0.05) and basal serum ferritin (r = -0.302, P < 0.05). Serum ferritin was significantly reduced after the Al loading tests, and the reduction (r = 0.357, P < 0.05) positively correlated with the increments of daily urinary Al excretion in the study group patients. However, no significant changes of serum Al, ferritin, and daily urinary Al excretion were noted in the control group patients. CONCLUSIONS: A long-term low dose Al exposure can cause significant Al accumulation and iron store depletion in CRI patients. Therefore, Al-containing agents should be used with caution in patients with CRI.

Adult↗
PubMed1996

Catheter ablation of junctional ectopic tachycardia by guarded low dose radiofrequency energy application.

The prognosis of junctional ectopic tachycardia has been poor. A 9-year-old boy with dilated cardiomyopathy and this incessant form of tachycardia underwent RF ablation. Without retrograde atrial depolarization during tachycardia, serials of low dose RF energy were applied near the His-bundle area to find out the arrhythmogenic foci. The optimal site for ablation showed rate acceleration at low dose application and rate slowing down followed by conversion upon increasing the energy. By using this guarded low dose ablation technique, the tachycardia was eliminated without AV block. The LV function also improved.

Cardiomyopathy, Dilated↗
PubMed1996

Pulse therapy with cyclophosphamide and methylprednisolone in patients with moderate to severe paraquat poisoning: a preliminary report.

BACKGROUND: Severe paraquat poisoning causes considerable morbidity and mortality. High doses of cyclophosphamide and dexamethasone have been used to treat patients with paraquat poisoning, but with mixed results. The use of pulse methylprednisolone and cyclophosphamide was investigated in the treatment of moderately severe paraquat poisoning. METHODS: During a six-year period 87 patients with paraquat poisoning were admitted to hospital, of whom 33 had moderate to severe intoxication. Seventeen patients received conventional treatment and served as historical controls, and 16 received intravenous infusions of cyclophosphamide 1 g daily for two days and methylprednisolone 1 g daily for three days. RESULTS: There were no differences between the groups in age, sex, severity of paraquat poisoning (as assessed by urine dithionite tests), or in the time elapsed from ingestion to presentation at hospital or to the beginning of haemoperfusion. No differences were seen in biochemical measurements on the third day after paraquat poisoning. The mortality in the pulse therapy group was lower than that in the control group (4/16 (25%) versus 12/17 (70.6%), p = 0.01). All fatalities were from progressive respiratory failure. CONCLUSIONS: Pulse therapy with cyclophosphamide and methylprednisolone may be effective in preventing respiratory failure and reducing mortality in patients with moderate to severe paraquat poisoning. Further controlled studies are needed to confirm this and to establish the mechanisms.

Adult↗
PubMed1996

Effect of long-term low-dose aluminum-containing agents on hemoglobin synthesis in patients with chronic renal insufficiency.

To investigate the possible toxic effects of long-term low-dose exposure to A1-containing agents in 55 patients with chronic renal insufficiency (CRI), 37 patients received A1(OH)3 1 tablet 3 times per day (about 302 mg/day of elemental A1) for 3 months and another 18 were used as a control group. The hematological, iron status and A1 data were measured before and after the study. CRI patients who had ingested A1-containing agents for 3 months had significant decreases in hematological parameters and increases in serum A1 and daily urinary A1 excretion. Serum ferritin negatively correlated with serum A1 (r = -0.586, p < 0.0005), and hemoglobin (Hb) positively correlated with renal A1 clearance (r = 0.573, p < 0.0005) and logarithmic transformation of serum A1 (r = -0.437, p < 0.01) in these patients, despite no significant correlations between initially basal hematological and A1 parameters. But there were no significant differences between variables of A1 and hematological parameters before and after 3 months of follow-up in the control group. All factors correlating with Hb were measured with stepwise regression analysis; renal A1 clearance, creatinine clearance (Ccr) and serum iron were the most significant correlation factors with Hb. After Ccr and serum iron had been adjusted, Hb (b = 0.069 +/- 0.02; p < 0.05) still positively correlated with renal A1 clearance. Comparing patients who had reduced Hb (at least 0.5 g/dl) and those who did not, the response group had a lower basal (Ccr, a higher serum A1 and a lower renal A1 clearance after A1 loading for 3 months. In conclusion, A1 does play a role in the significant reduction of Hb and hematocrit in CRI patients after A1 loading for 3 months, and patients with a lower Ccr may easily develop A1-induced hematologically toxic effects. A1-containing agents should be used with care in long-term therapies of CRI patients.

Adult↗
PubMed1996

The mechanism of sympathovagal imbalance in patients with myocardial ischemia.

To investigate the mechanism of sympathovagal imbalance due to myocardial ischemia, we studied 42 consecutive patients undergoing successful percutaneous transluminal coronary angioplasty by correlating frequency domain and time domain measures of heart rate variability with parameters such as echocardiography, stress thallium scanning and radionuclide angiography before, immediately after and 2 months after the procedure. Of these, 20 patients (Group N) had normal and 22 patients (Group A) had abnormal regional wall motion. A control group of 20 healthy subjects (Group C) underwent echocardiography and examination of heart rate variability twice at 2-month intervals to check for spontaneous variations. At baseline, frequency domain measures such as low and high frequency power and time domain measures such as SDANN index (the mean of the standard deviations of the average of RR intervals) were lower in Group A than in Groups N and C, whereas no differences were detectable in ultra low and very low frequency, total power, SDNN index (the mean of the standard deviations of the mean of normal RR intervals), and r-MSSD (the root mean square of successive RR differences). There was high association between the diastolic wall stress index and both high frequency (r = -0.82) and low frequency power (r = -0.77). There were similar findings for the systolic wall stress index (r = -0.72 for high frequency and r = -0.64 for low frequency power). After successful coronary angioplasty, regional wall motion, left ventricular wall stress indices and all measures of heart rate variability were unchanged in Group N. In Group A the mean summed segment score improved from 15.9 +/- 2.6 to 12.2 +/- 1.7 (p < 0.0001), and mean low frequency, mean high frequency power (logarithmic units), and SDANN index (msec) increased from 6.10 +/- 0.23 to 6.36 +/- 0.28 (p < 0.005), from 5.36 +/- to 0.40 to 5.70 +/- 0.39 (p < 0.01) and from 70 +/- 18 to 83 +/- 18 (p < 0.01) respectively. In addition, low and high frequency power and SDANN index, lower at baseline in Group A than in the other two groups, were comparable in the three groups after coronary angioplasty. The evolution of diastolic and systolic wall stress indices paralleled that of the above three parameters. In conclusion, diastolic and systolic wall stress indices, in addition to segmental left ventricular dysfunction, were synergistically involved in determining sympathovagal imbalance in patients with significant coronary artery disease; the reversal of left ventricular dysfunction and wall stress indices improves the profile of heart rate variability. Alterations in cardiac geometry and wall stress influence mainly the discharge of afferent sympathetic and efferent parasympathetic innervations and also principally the long-term heart rate variations instead of short-term modulation.

Angioplasty, Balloon, Coronary↗
PubMed1996

The cause-effect relationship of sympathovagal activity and the outcome of percutaneous transluminal coronary angioplasty.

We studied 25 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) to determine the association of sympathovagal imbalance and the outcome of coronary angioplasty. We examined the profiles of heart rate variability (HRV) using echocardiography, stress thallium scanning and radionuclide angiography before, immediately after and 1 month after the procedure. Coronary angiography was followed up at 6 months or if restenosis was suspected, to determine whether restenosis had occurred. Frequency domain (LF/HF) and time domain (SDNN, SDANN-ind, and r-MSSD) parameters were analyzed. According to the evolution of each parameter, we classified the patients into Group Ax (improved in HRV profile) and Group Bx (deteriorated in HRV profile) [x = 1 for LF/HF, 2 for SDNN, 3 for SDANN-ind, and 4 for r-MSSD]. We found that there was no definite association between Gensini score and HRV profiles at the baseline for each group. No significant changes existed between the HRV profiles before and immediately after PTCA. For the LF/HF ratio, 5 of 11 in Group B1 had restenosis while 0 of 14 in Group B2 and 1 of 19 in Group A2 had restenosis (p < 0.01). There were no significant predictive values for SDANN-ind and r-MSSD (p = 0.12 and 0.07, respectively). We conclude that the sympathovagal imbalance did not reflect the severity in coronary artery disease but was associated with restenosis after successful PTCA.

Aged↗