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Biomedical subjects

H M Lo

Publications and source records attributed to H M Lo.

At least 55 records · Page 3Linked to original sources
PubMed1994

Characteristic abnormal findings of ambulatory blood pressure indicative of hypertensive target organ complications.

To study the correlation between ambulatory blood pressure and target organ complications of hypertension, ambulatory blood pressure monitoring was performed on 290 patients with mild to moderate essential hypertension before treatment. Their target organ complications of hypertension were assessed by ECG, chest X-ray, urinalysis and an eye-fundus examination. An average ambulatory diastolic blood pressure value greater than the casual diastolic blood pressure was found in 35% of subjects with ECG evidence of left ventricular hypertrophy (LVH) and 5.2% of subjects without (P < 0.001); in 36.5% of patients with chest roentgenographic evidence of LVH and 8.4% of patients without (P < 0.0001); in 38.5% of patients with proteinuria and 11% of patients without (P < 0.0001); and in 27.1% of subjects with retinopathy and 10.7% of subjects without (P < 0.01). A similar result was observed for the systolic blood pressure. A reversed circadian pattern of ambulatory diastolic blood pressure was observed in 32.5% of patients with ECG evidence of LVH and 12.9% without (P < 0.0001); in 28.8% of patients with chest roentgenographic evidence of LVH and 16% without (P < 0.05); in 26.9% of subjects with proteinuria and 17.4% without (P < 0.05); in 37.5% of patients with retinopathy and 14.5% without (P < 0.0001). A similar result was also demonstrated for ambulatory systolic blood pressure. There was a close relationship between the blood pressure load and hypertensive target organ complications in terms of LVH and proteinuria, and between significant nocturnal reduction of ambulatory systolic blood pressure and LVH.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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

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

Body surface potential maps of ventricular depolarization in normal adults.

Body surface potential maps were obtained in 50 normal adults using the heart potential map system designed by Yamada. Group A (younger adult group) consisted of 30 persons whose ages ranged from 20 to 39 years. Group B (middle-aged group) included 20 persons whose ages ranged from 40 to 59 years. Although there were slight variations in the pattern of isopotential distribution among the subjects studied, a consistent pattern with a similar sequence was observed in both study groups. However, there were some parameters which significantly differed between groups A and B, including the earliest appearance time of the anterior negative potential (p < 0.05), the anterior potential minimum (p < 0.001), the posterior positive potential (p < 0.001), the midsternal minimum (p < 0.001), the largest potential minimum (p < 0.05), the largest potential maximum (p < 0.005), the "reversal" pattern (p < 0.001), the multipolar potential distribution in the upstroke (p < 0.001) and the amplitude of potential minimum in the periods 50 msec (p < 0.005) and 60 msec (p < 0.01) of ventricular depolarization. Accordingly, the data obtained regarding the time relationship between the bipolar and multipolar phases, the distribution and time course of the potential as well as the dynamic changes in potential voltage, particularly the age-related potential pattern will serve as a basis for further study of BSPM.

Adult↗
PubMed1993

Influence of age on ambulatory blood pressure in treated hypertensive patients with normal casual pressure.

To investigate the influence of age on ambulatory blood pressure monitoring (ABPM) in hypertensive patients whose controlled casual blood pressure was normal, we studied the ABPM in 225 patients, including 122 men and 103 women, aged from 45-74 years. They were classified into three groups: Group A included 93 patients aged 45 to 54 years; Group B included 99 patients, aged 55-64 years; and Group C included 33 patients, aged 65 years and over. The various ABPM data were analyzed and compared among the three groups. The following results were found. The blood pressure (BP) averages for the whole day were normal in all three groups. There was no difference in the systolic BP average among the three groups, but the diastolic BP average declined as age increased. The variability in the systolic BP measurements increased with age. The variability in diastolic BP did not seem to change as conspicuously with age, except for the group C patients who showed a larger variability at nighttime than the other two groups. There were 123 patients (54.7%) with evidence of diurnal change in BP, and the incidence of diurnal change in BP decreased with age. The frequency of abnormally high systolic BP was similar among the three groups, but the frequency of an abnormally high diastolic BP decreased significantly with age. As for the maximal BP levels recorded in the ABPM, group C patients had a higher maximal systolic BP than the other two groups. Therefore, age has a great influence on ABPM in controlled hypertensive patients with normal casual BP.

Aged↗
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

Holter monitoring in patients with Wolff-Parkinson-White syndrome: with special reference to intermittent pre-excitation.

To characterize the intermittency of pre-excitation in patients with Wolff-Parkinson-White syndrome (W-P-W), we studied the ambulatory electrocardiograms (ECGs) of 48 patients (32 men and 16 women with a mean age of 38.5 years) with W-P-W. As documentation, at least one ECG for each patient had been performed during the follow-up period at our clinics. All cardiovascular drugs were discontinued for at least two days before Holter ECG monitoring. Through a careful beat-to-beat analysis of the QRS complex morphology, we were able to classify these patients into three groups: persistent pre-excitation in 26 (54.2%); intermittent pre-excitation in 17 (35.4%); and no pre-excitation in five (10.4%). There was no significant difference in sex, frequency of arrhythmias or mean heart rate among the three groups. Among the 17 showing intermittent pre-excitation, type A W-P-W was more prevalent (12 cases), and the ratio of pre-excitation to normal beats tended to decrease with age. Conduction normalized gradually with an increase in heart rate in 12 patients and suddenly in five other cases. There were two patients who showed a period of 2:1 pre-excitation intermingled with 1:1 pre-excitation and 1:1 normalized beats. These changes occurred with equal frequency both during the daytime and at night. These findings suggest that intermittent pre-excitation is a rather frequent phenomenon in patients with W-P-W. It occurs more frequently in type A patients and in older patients. Therefore, it may be an intermediate phase between manifest and concealed W-P-W.

Adolescent↗
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↗
PubMed1991

[Barium intoxication: a case report].

Barium intoxication, a rare cause of hypokalemia, can sometimes result in respiratory paralysis and ventricular tachyarrhythmia. Herein, we report one such case. A 29-year-old man swallowed barium-contaminated fried flour-coated sweet potatoes. Then, abdominal discomfort, vomiting, diarrhea, progressive muscular weakness, apnea and ventricular tachycardia developed and laboratory data revealed profound hypokalemia. He regained his health after mechanical ventilation, anti-arrhythmic agent and aggressive potassium chloride supplement. Analysis of blood, urine and contaminated flour showed the presence of barium carbonate. Barium intoxication is a medical emergency which requires rapid therapy to prevent mortality.

Acute Disease↗
PubMed1991

Molecular cloning of complementary deoxyribonucleic acid (cDNA) for the rat atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) is a cardiac hormone with an important role in fluid, electrolyte and hemodynamic homeostasis. Rat ANP cDNA was cloned from the cDNA library constructed using 1 microgram of atrial mRNA from the heart of Wistar rats. Eight positive clones were isolated with an ANP oligonucleotide probe. One of them with about a 0.8 kb insert was selected for further subcloning and sequencing analysis. The rat ANP cDNA had 813 base pairs with a concensus sequence for transcription initiation, termination and poly A tailing. The deduced amino acid sequence contains a potential glycosylation site and two putative protease cleavage sites. Northern blot analysis showed that the ANP gene was specifically transcribed in the rat atria rather than the ventricles. The results suggest that ANP gene expression is differentially and developmentally controlled.

Amino Acid Sequence↗
PubMed1991

Diagnostic value of measuring BCG sonicate antigen and anti-BCG antibodies in the cerebrospinal fluid and blood of patients with tuberculous meningitis.

Fourteen cerebrospinal fluid (CSF) and paired blood samples were obtained from patients with tuberculous meningitis, seven with positive culture and seven clinical/laboratory diagnosis. Another 14 paired specimens served as control, including 7 infectious meningitis and 7 non-inflammatory neurological diseases. Four groups were thus classified, including confirmed and suspected patients, and controls with infectious meningitis and neurological diseases. Measurements of Bacillus Calmette-Guérin (BCG) sonicate antigen and IgG antibody were performed using enzyme-linked immunosorbent assay. Generally, CSF BCG sonicate antigen level and anti-BCG sonicate antibody of patients with tuberculosis meningitis were higher than in control groups; greater antigen levels were found in confirmed patients than in non-inflammatory subjects (p less than 0.05), and in suspected patients than in infectious and non-inflammatory subjects (p less than 0.05 and p less than 0.01). For serum anti-BCG sonicate levels, confirmed patients had higher antibody value than non-inflammatory subjects (p less than 0.05). To conclude, detection of high levels of both BCG sonicate antigen and antibody in CSF and blood samples shows great value in the diagnosis of tuberculous meningitis. However, given the limited samples of the current research, more data are needed to elucidate the sensitivity and specificity of such tests.

Adolescent↗
PubMed1990

The value of body surface potential maps in detecting abnormal ventricular wall motion.

In an effort to enlarge the clinical application of body surface potential maps (BSPMs), the authors studied the relationship between abnormal ventricular wall motion and BSPMs in 98 consecutive patients with angiographically proven coronary artery disease (CAD). Forty-nine of the patients (50%) had wall motion abnormalities as seen on single-plane left cine ventriculograms. During early ventricular depolarization, normal BSPMs have a potential maximum that is greater than the absolute value of the potential minimum; this reverses in late depolarization such that the absolute value of the potential minimum is the greater. The patients showed a significantly early reversal (p less than 0.001), and 55 (56.1%) had abnormal "early reversal" BSPMs. This abnormal "early reversal" is closely related to abnormal ventricular wall motion. Using it as an indicator of abnormal wall motion, the authors obtained the sensitivity, specificity, positive predictive value, and negative predictive value of the following conditions: LAD lesions, LCX, RCA, LAD and RCA lesions, LAD and LCX, and three-vessel disease, and for all patients. A relatively high sensitivity (85%) and specificity (80%) was found in patients with LAD lesions only or multivessel lesions in addition to LAD lesions.

Adult↗
PubMed1990

Reappraisals of atrioventricular node reentrant tachycardia: lessons learned from surgical treatment.

The exact site of reentrant circuit involved in the atrioventricular node reentrant tachycardia was questioned. Seven patients (6 females and 1 male), aged 21 to 64 years (mean = 40 +/- 17 years), with refractory nodal reentry, underwent surgical treatment. The associated cardiac diseases included rheumatic valvar disease in two and an atrial septal defect. Electrophysiologic studies before surgery showed dual nodal pathways in 4 patients. Right atrial endocardial mapping was performed and the earliest retrograde atrial activation during tachycardia was mapped to the apex of the triangle of Koch in 6 patients and near the orifice of coronary sinus in one. Perinodal dissection was performed according to the location of earliest retrograde atrial activity. Care was taken to preserve as much of the atrioventricular node and its arterial supply as was possible. Immediately after surgery, conduction in an antegrade direction recovered and the tachycardia could no longer be reproduced. There was no surgical mortality or morbidity. At 10 to 26 months of follow-up, all patients remain free of tachycardia without antiarrhythmic drugs. Four patients underwent repeated electrophysiologic studies at 2 weeks to 6 months after surgery. Dual nodal pathways were no longer demonstrated. It is concluded that the perinodal atrial tissue plays a part in the atrioventricular nodal reentry, and that surgical dissection is a simple and effective treatment for patients with refractory atrioventricular node reentrant tachycardia.

Adult↗
PubMed1990

The value of body surface potential maps in assessment of experimental myocardial infarction.

Body surface potential maps (BSPMs) and the pathology of 32 dogs with coronary artery ligations were analyzed to research the application of BSPMs to acute myocardial infarction (AMI). The group consisted of 18 dogs with left anterior descending coronary artery (LAD) ligations, 8 with right coronary artery (RCA) ligations and 6 with left circumflex coronary artery (LCX) ligations. The abnormal distribution of negative potential and minimal potential were observed in all of the dogs. In dogs with RCA ligations, the abnormal negative potential displayed on the right-superior, right-inferior or right portion of the anterior thorax. In those with LAD ligations, the abnormal potential appeared on the left-superior, left-inferior, middle-superior or middle portion of the anterior thorax. In those with LCX ligations, the abnormal potential showed on the left-superior or left-middle portion of the thorax. A good correlation was observed between the area of myocardial lesion and the extent of abnormal negative potential distribution (r = 0.82, p less than 0.001). A close correlation was also found between the area of myocardial lesion and the duration of abnormal negative potential (r = 0.61, p less than 0.05). This study suggests that BSPMs are useful in the assessment of AMI in terms of diagnosis, location and extent of myocardial infarct.

Animals↗