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Biomedical subjects

H M Lo

Publications and source records attributed to H M Lo.

At least 19 recordsLinked to original sources
PubMed2001

Recurrent cardiac myxoma with multiple distant metastasis and malignant change.

A 37 year-old female underwent open heart surgery for a left atrial myxoma. The post-operative course was uneventful and she was discharged two weeks later. She had regular monthly follow-up in the outpatient department until 10 months postoperatively when she was readmitted to the orthopedic ward for excision of a left ankle tumor. Two days after admission, she developed severe orthopnea. The initial diagnosis was heart failure, and she was transferred to the medical ward for treatment. Transthoracic and transesophageal echocardiography revealed a recurrent left atrial tumor. Because of acute obstruction of the mitral valve and deterioration of her condition, she underwent emergent open heart surgery. The recurrent atrial tumor was excised; histopathologic examination revealed a myxoid sarcoma. Multiple tumors were found on this admission, including a mass in the neck and in the left forearm; computed tomography revealed a brain tumor in the left posterior frontal lobe and a chest wall tumor. She died two months later. Recurrent cardiac myxoma with multiple distant metastasis may have a malignant potential. Because of the potential for tumor recurrence, long-term and regular follow-up is mandatory.

Adult↗
PubMed2000

Role of electrophysiological studies and arrhythmia intervention in repairing Ebstein's anomaly.

BACKGROUND: Repairing Ebstein's anomaly without correction of associated arrhythmia may result in sudden death. Catheter or surgical ablation is indicated for various symptomatic tachyarrhythmias in Ebstein's anomaly. METHODS: Between October 1973 and October 1997, 30 patients with Ebstein's anomaly underwent surgical repair in our hospital. Tricuspid valve replacement was performed in 13 patients, tricuspid annuloplasty and valvuloplasty in the remaining 17 patients. Preoperative electrophysiological studies were performed in 11 patients after 1980. Concomitant arrhythmia ablation was done in 10 patients: 4 for Wolff-Parkinson-White syndrome, 2 for atrioventricular (AV) nodal reentrant tachycardia, one for ventricular tachycardia and 3 for paroxysmal atrial flutter and fibrillation. RESULTS: No mortality or major morbidity occurred in those patients undergoing arrhythmia intervention. There were 7 deaths in total; 6 died suddenly, and the other died of purulent mediastinitis. None of the 6 sudden deaths underwent preoperative electrophysiological evaluation. The functional recovery was good in all survivals. CONCLUSIONS: We conclude that detailed preoperative electrophysiological evaluation in patients with Ebstein's anomaly is mandatory. Aggressive surgical intervention of the associated arrhythmias in addition to anatomic correction can reduce the sudden death in Ebstein's anomaly.

Adolescent↗
PubMed2000

Biphasic changes in autonomic nervous activity during pregnancy.

To understand the sequential response of the autonomic nervous system to pregnancy, we studied heart rate variability in 23 first trimester, 23 second trimester and 21 third trimester pregnant women. Twenty non-pregnant women were recruited as controls. Time and frequency domain measures of heart rate variability in three recumbent positions were compared. We found that normalized high-frequency power in the supine position increased significantly in the first trimester (42.2 (95% confidence interval (CI) 5.4) nu (normalized unit); P < 0.05) compared with non-pregnant controls (33.0 (6.0) nu), and then decreased progressively in the second (27.3 (6.7) nu) and third (21.8 (6.0) nu; P < 0.05) trimesters. The low-/high-frequency power ratio in the supine position decreased significantly in the first trimester (0.8 (0.3); P < 0.05) compared with that of non-pregnant controls (1.1 (0.3)) and increased progressively in the second (1.5 (0.4)) and third (2.1 (0.8); P < 0.05) trimesters. When the position was changed from the supine to the right lateral decubitus, the percentage change in normalized high-frequency power correlated significantly and negatively with normalized high-frequency power in the supine position in non-pregnant controls (r = -0.56, P = 0.01) and in pregnant women in the first (r = -0.44, P = 0.034), second (r = -0.68, P < 0.001) and third (r = -0.68, P < 0.001) trimesters. These results indicate that autonomic nervous activity shifted towards a lower sympathetic and higher vagal modulation in the first trimester, and changed towards a higher sympathetic and lower vagal modulation in the third trimester as gestational age increased. The balance between the haemodynamic changes of pregnancy and aortocaval compression caused by the enlarging gravid uterus may be responsible for the biphasic changes in autonomic nervous activity during pregnancy.

Adult↗
PubMed2000

Effect of different recumbent positions on spectral indices of autonomic modulation of the heart during the acute phase of myocardial infarction.

OBJECTIVE: To examine which recumbent position can lead to the highest vagal modulation in patients during the acute phase of myocardial infarction. DESIGN: Descriptive study. SETTING: Intensive care unit in a medical center. PATIENTS: A total of 52 patients admitted to the intensive care unit because of acute myocardial infarction (AMI), 41 patients with coronary artery disease (CAD), and 28 patients with patent coronary arteriogram. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Heart rate variability analysis was performed in patients with AMI, patients with CAD, and patent coronary controls in supine, left lateral decubitus, and right lateral decubitus positions in random order. In the right lateral decubitus position, the vagal modulation was the highest and the sympathetic modulation was the lowest among three recumbent positions in three groups of patients. When the position was changed from supine to right lateral decubitus, the increase in vagal modulation was greater in patients who had more severely depressed vagal modulation in the supine position and the rate of increase was the greatest in patients with AMI, followed by patients with CAD and patent coronary controls. Detailed analysis showed that the vagal enhancing and sympathetic suppression effect of the right lateral decubitus position applied to patients with Q wave myocardial infarctions. CONCLUSIONS: The right lateral decubitus position can lead to the highest vagal modulation and the lowest sympathetic modulation among three recumbent positions in patients with Q wave myocardial infarction. The right lateral decubitus position can be used as an effective vagal enhancer in patients with Q wave myocardial infarction but without severe bradycardia or atrioventricular block.

Aged↗
PubMed2000

Expression pattern in a modified equalized kidney cDNA library of hypertensive rat.

BACKGROUND: Genes with important functions and rarely expressed would probably more easily be cloned from a modified equalized kidney cDNA library for further investigation. METHODS: A kidney cDNA library of a spontaneously hypertensive rat was synthesized by a modified equalization method. Inserts of random clones were amplified by PCR and sequenced. Sequences were compared against a nonredundant database in GenBank. The cDNA profile was compared with an expression profile of a mouse renal proximal tubule cDNA library. Seven clones were analyzed by Northern blot analysis. The cDNA ends of two novel genes were amplified by PCR, sequenced and analyzed. RESULTS: 336 cDNA clones were analyzed and grouped into 323 species of transcript with 77 species similar to previously reported genes. Northern blot analysis identified one kidney-specific, one rarely expressed and lung-specific, and another relatively testis-specific gene. Two novel genes were cloned. One was 4.1 kb in length and encoded a 390-amino acid zinc-finger protein. Another was 2.5 kb and encoded a 474-amino acid protein of unknown function. Compared with the expression profile of a mouse renal proximal tubule cDNA library, this kidney library had a lower proportion of ribosomal genes and had a greater proportion of genes for signal transduction and DNA or RNA binding. CONCLUSIONS: Rare or novel genes could be more easily isolated from this library for molecular study of hypertension and renal pathophysiology.

Amino Acid Sequence↗
PubMed2000

Cloning a novel metallophosphoesterase gene from a kidney cDNA library of hypertensive rat.

BACKGROUND AND PURPOSE: Genetic and environmental factors may contribute to the pathogenesis of essential hypertension. To facilitate genetic studies of hypertension and renal disorders, we sought to clone novel genes from a modified, equalized kidney (MEK) cDNA library of a spontaneously hypertensive rat (SHR). METHODS: A kidney cDNA library of an SHR was synthesized using the modified equalization method. Inserts of 350 random clones were amplified by polymerase chain reaction (PCR) and sequenced, of which 246 were presumably unknown after being compared against a nonredundant database in the GenBank. The cDNA ends of clone 38S were obtained by rapid amplification of cDNA ends, sequenced, and then analyzed with Translate, Prosite, Profile, SignalP, and TMpred programs. RESULTS: The full-length cDNA was 938 bp, and translated into a 182-amino acid protein. The deduced protein had a metallophosphoesterase domain, a signal peptide at its amino end, a protein kinase C phosphorylation site, and a transmembrane domain. Northern blot analysis revealed that this gene was expressed in the heart, brain, spleen, lungs, liver, skeletal muscles, kidneys and testes of Sprague-Dawley rats. A putative protein of Arabidopsis thaliana shares 62% homology with protein 38S, but the two proteins differ in terms of function and structure. CONCLUSIONS: Our results support that protein 38S is a novel membrane metallophosphoesterase, although its function in the kidneys remains to be elucidated. This study also demonstrates the feasibility of using PCR to clone novel genes from our MEK cDNA library.

Acid Phosphatase↗
PubMed1999

Comparison of supine and upright positions on autonomic nervous activity in late pregnancy: the role of aortocaval compression.

In order to understand the effect of aortocaval compression on autonomic nervous activity, we compared the effects of supine and upright postures on measures of heart rate variability in late pregnancy. Thirty-two women in late pregnancy and 23 nonpregnant age-matched women were studied. Both time and frequency domain heart rate variability measures were compared between the supine and upright positions, and between pregnant women and controls. The pregnant women had smaller mean RR interval, standard deviation of RR intervals and normalised high-frequency power, and a larger low- to high-frequency power ratio than nonpregnant women in the supine position. When the position was changed from upright to supine in nonpregnant women, the percentage change in the mean RR interval and normalised high-frequency power were increased, whereas the percentage change in the coefficient of variation of RR interval and low- to high-frequency power ratio were decreased. In contrast, the percentage change in normalised high-frequency power was decreased and the percentage change in low- to high-frequency power ratio was increased in pregnant women when the position was changed from upright to supine. These results indicate that the vagal enhancing effect seen in normal subjects when changing position from upright to supine was reversed in women in late pregnancy. Aortocaval compression in the supine position in pregnant women might be responsible for this reversal in the autonomic response to lying down.

Adult↗
PubMed1999

Return of autonomic nervous activity after delivery: role of aortocaval compression.

We have compared measures of heart rate variability (HRV) in 15 women in late pregnancy before and 3 months after delivery and in 20 non-pregnant controls, to study the effect of aortocaval compression on autonomic nervous activity. Normalized high-frequency power was used as an index of vagal activity and the low-/high-frequency power ratio as index of sympathovagal balance. We found that the decrease in vagal activity and increase in sympathovagal balance before delivery returned to normal 3 months after delivery. Percentage changes in vagal activity and sympathovagal balance 3 months after delivery in the left lateral decubitus position were least among three recumbent positions. The relief of aortocaval compression as a result of delivery of the fetus may be the main cause of return of autonomic nervous activity 3 months after delivery. Postpartum hormonal changes may also contribute to return of autonomic nervous activity after delivery.

Adult↗
PubMed1999

Impaired cardiac performance relating to delayed left atrial activation after atrial compartment operation for chronic atrial fibrillation.

In the presence of a normal atrial systole and optimal AV delay, atrial kick contributes to a significant fraction of the stroke volume. This atrial contribution may be lost during atrial asystole or mismatch in the timing of atrial and ventricular contraction. A patient received atrial compartment operation for his chronic AF. Although the AF was successfully converted to sinus rhythm, the conduction from the right to left atrium was markedly delayed so that the left atrial and ventricular activations occurred almost simultaneously. This delay in left atrial activation resulted in impaired cardiac performance.

Atrial Fibrillation↗
PubMed1999

Effect of acupuncture at nei-kuan on left ventricular function in patients with coronary artery disease.

Effect of acupuncture at Nei-Kuan (EH-6) on left ventricular ejection fraction (LVEF) was examined in 22 patients with angiographically proved coronary artery disease (CAD) and 22 normal subjects. Serial equilibrium radionuclide angiography was done to measure LVEF at 4 different times (at baseline, at 1 to 15 minutes, and 16 to 30 minutes during acupuncture, and immediately after acupuncture). One week later, each patient had an identical imaging protocol with acupuncture performed at a dummy point. Our results showed that in normal subjects, the mean values of LVEF did not change significantly during or after acupuncture. In contrast, in patients with CAD, the mean values of LVEF in the initial 15 minutes of acupuncture significantly increased from baseline (42.5 +/- 15.6% vs. 40.6 +/- 15.4%, p < 0.05). The increase persisted through the next 15 minutes of acupuncture and 15 minutes after acupuncture, but became insignificant at one week. Thus, acupuncture at Nei-Kuan can temporarily improve LV function in patients with CAD.

Acupuncture Points↗
PubMed1999

Characteristic findings of body surface potential map during ventricular repolarization in patients with coronary heart disease.

The objective of the present study was to investigate the characteristics of body surface potential map (BSPM) findings during ventricular repolarization in patients with coronary artery disease (CAD). A total of 108 consecutive patients, 99 men and 9 women with angina pectoris and positive treadmill exercise test results as well as angiographically documented CAD underwent BSPM study in a fasting state. Their ages ranged from 30 to 70 years. There were 13 patients with right coronary artery (RCA) lesions, 37 with left anterior descending artery (LAD) lesions, 5 with left circumflex artery (LCX) lesions, 17 with both RCA and LAD lesions, 12 with both LCX and LAD lesions, and 24 with 3-vessel disease. The BSPMs were obtained by using the heart potential map system designed by Toyama et al. There were 59 lead points on the anterior chest wall and 28 on the back. The BSPMs in isopotential distribution were made every one msec throughout the ventricular activation period. The distribution of positive and negative potentials, potential maximum and potential minimum, polarity of potential distribution, and the reversal of potential distribution during ventricular repolarization were analyzed. The following information on BSPMs was obtained: (1) In early ventricular repolarization, the negative potential and the potential minimum appeared abnormally on the anterior thorax. The potential abnormality displayed on the right portion or the inferior portion in patients with RCA lesions, on the middle portion or the left portion in patients with LAD lesions, and on the left-superior portion or the left-middle portion in patients with LCX lesions. In patients with multi-vessel disease, the abnormal potential distribution showed a combined pattern of individual vessel lesions. (2) In some cases, the multipolar potential distribution appeared abnormally during the initial stage and the peak of the T wave. (3) The reversal of potential distribution was observed in about half of the patients. The characteristic findings of the BSPM during ventricular repolarization, including abnormal potential distribution, multipolar potential distribution and reversal of potential distribution, will be of clinical value in patients with CAD.

Adult↗
PubMed1999

Implications of an early reversal pattern of body surface potential maps in coronary artery disease.

During early ventricular depolarization, the normal body surface potential map (BSPM) has a maximal potential that is greater than the absolute value of the minimal potential; this reverses in late depolarization, so that the absolute value of the minimal potential is greater. Nevertheless, an abnormal "early reversal" BSPM pattern has been observed in some patients with cardiovascular disease. To investigate the implications of this abnormal pattern, BSPMs were studied in 100 patients with angiographically proven coronary artery disease (CAD). There were 57 patients (57%; group A) with an abnormal early reversal pattern and 43 (43%; group B) without this early reversal pattern. A significant (> 70% narrowing) CAD lesion was observed in a significantly higher proportion of group A (97%) than group B (77%) patients, although the number of involved coronary arteries was not significantly different between the two groups. The maximal extent of the abnormal negative potential was significantly greater in group A (21.2 +/- 9.6 cm2) than in group B (12.2 +/- 7.5 cm2). The abnormal negative potential lasted significantly longer in group A (22.1 +/- 12.1 msec) than in group B (14.4 +/- 9.2 msec). Similarly, the minimal potential lasted significantly longer in group A (20.1 +/- 11.3 msec) than in group B (11.8 +/- 7.1 msec). These findings suggest that the abnormal early reversal BSPM pattern is a valuable indicator of extensive myocardial lesions and the severity of CAD.

Adult↗
PubMed1998

Atrial dissociation after atrial compartment operation for chronic atrial fibrillation in mitral valve disease.

Atrial dissociation with segmental atrial arrhythmia is an interesting electrophysiological phenomenon. It was rarely reported before to be caused by anatomical exit block after cardiac surgery. We report the case of a 28-year-old patient who developed atrial disassociation after a surgical method for correcting atrial fibrillation--atrial compartment operation. The segmental atrial flutter was first found by Doppler echocardiography and proved later by detailed intracardiac mapping.

Adult↗
PubMed1998

The use of body surface potential map for identifying sites of accessory pathway in patients with Wolff-Parkinson-White syndrome.

The body surface potential map (BSPM) may reflect regional myocardial electrical activity. This technique can thus provide information regarding the excitation of ventricles. This study is an attempt to evaluate the usefulness of BSPM in determining the sites of the atrioventricular (AV) accessory pathway (AP) in patients with Wolff-Parkinson-White (W-P-W) syndrome. The BSPMs were obtained from 40 consecutive patients with W-P-W syndrome in a fasting state, using the heart potential map system designed by Toyama et al. Unipolar electrocardiograms were recorded simultaneously from 87 lead points on the chest surface, including 59 lead points on the anterior chest and 28 on the back. Wilson's central terminal was used as a voltage reference and BSPMs in an isopotential distribution pattern were made every millisecond throughout ventricular activation from these unipolar ECGs with the use of a microcomputer system. All patients underwent an electrophysiologic study (EPS) at cardiac catheterization. We analyzed the potential distribution during ventricular depolarization and compared the results between EPS and BSPM findings. The following results were obtained: (1) seven types of BSPM pattern were identified in accordance with the sites of the AV AP confirmed by EPS; (2) the location of the potential minimum of ventricular depolarization and the direction of the excitation wavefront during early ventricular depolarization, the reversal pattern of ventricular potential distribution, the epicardial right ventricular breakthrough and the dynamic change of ventricular potential distribution were useful for the detection of the ventricular pre-excitation site; (3) epicardial right ventricular breakthrough occurred in nearly all patients with left ventricular free wall accessory AV connections; (4) the abnormal early reversal pattern of ventricular potential distribution did not occur in patients with left ventricular AV connections but did appear in most patients with right ventricular free wall AV connections. Accordingly, BSPM is a reliable non-invasive procedure to determine the ventricular pre-excitation sites of patients with W-P-W syndrome.

Adolescent↗
PubMed1997

Congenital mitral stenosis: challenge of percutaneous transvenous mitral commissurotomy.

A 26-year-old woman with congenital mitral stenosis and embolic stroke was referred to our hospital. The echocardiogram showed a hypoplastic posterior mitral valve leaflet with short, unbalanced chordal attachments to the posteromedial papillary muscle. The mitral valve area was 0.9 cm2 by the pressure half-time method. There was no left atrial thrombus and spontaneous echo contrast. Percutaneous transvenous mitral commissurotomy was performed since the suggestion of surgical management was refused by her family members. A rupture at the chordae tendinae of the hypoplastic posterior papillary muscle developed during the procedure and needed mitral replacement. We advise that percutaneous transvenous mitral commissurotomy be avoided in adult patients with congenital mitral stenosis having an asymmetric and hypoplastic mitral valve.

Adult↗
PubMed1997

Lack of association of the angiotensin converting enzyme polymorphism with essential hypertension in a Chinese population.

To examine the association between insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene and essential hypertension in a Chinese population, a case-control study was conducted using 157 hypertensive and 115 normotensive subjects. The I/D polymorphism of the ACE gene was identified by polymerase chain reaction. Plasma ACE activity was determined using spectrophotometry. The difference of allele frequencies between normotensives and hypertensives was statistically significant (chi 2 = 4.467, P = .035), while the genotype distribution was not different between normotensive and hypertensive subjects (chi 2 = 3.954, P = .138). Plasma ACE activity was highest in the DD genotype, followed by the ID genotype, and the lowest in the II genotype (P = .0001 in normotensives and P = .163 in hypertensives, respectively). Thus, we conclude that the ACE gene polymorphism is not associated with essential hypertension in this Chinese population, but plasma ACE activity is genetically determined in the normotensive Chinese.

Adult↗