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Biomedical subjects

K C Lau

Publications and source records attributed to K C Lau.

52 records · Page 3Linked to original sources
PubMed1987

Demonstration of ascending aorta in hypoplastic left heart syndrome with aortic atresia by balloon occlusion aortography.

Balloon occlusion angiography in the descending aorta produced clear retrograde visualization of the hypoplastic ascending aorta and related structures in eighteen neonates with aortic atresia. Transient bradycardia was the only complication observed. It is technically simpler than retrograde cannulation of the aorta via an arteriotomy and should be the method of choice when cardiac catheterization is required in patients with the hypoplastic left heart syndrome.

Aorta↗
PubMed1987

Cross-sectional and pulsed Doppler echocardiography of the atrioventricular junction of hearts with univentricular atrioventricular connexion.

The atrioventricular junction of 52 consecutive patients with univentricular atrioventricular connexion was examined by cross-sectional and pulsed Doppler echocardiography. The echocardiographic features were then compared with catheterisation and cineangiographic findings. In the diagnosis of the mode of atrioventricular connexion, cross-sectional echocardiography was superior to cineangiography in differentiating single inlet with absence of one atrioventricular connexion from double inlet with a common atrioventricular valve. Straddling atrioventricular valves were diagnosed by echocardiography alone. Using pulsed Doppler echocardiography, the diagnostic sensitivity of atrioventricular valvar regurgitation was 92.6% and the specificity 100%. By mapping the regurgitant jet with pulsed Doppler echocardiography, an index was derived to evaluate the severity of atrioventricular valvar regurgitation. The indices obtained correlated well with cineangiographic grading on a three-point scale (Spearman rank correlation coefficient: rs = 0.9). Thus, cross-sectional echocardiography coupled with a range-gated Doppler system provide accurate anatomical details of the atrioventricular junction and reliable assessment of atrioventricular valvar regurgitation in patients with univentricular atrioventricular connexion.

Adolescent↗
PubMed1987

Aortic atresia with complete transposition.

Aortic atresia with ventriculoarterial discordance in a three day old neonate was studied by cross sectional echocardiography and the anatomy was confirmed at necropsy.

Abnormalities, Multiple↗
PubMed1986

Atrioventricular septal defect after surgical resection of a subaortic shelf.

Left ventricular to right atrial (LV-RA) communications are rare septal defects. The majority of them are congenital in origin and acquired defects are exceedingly rare. The causes of acquired LV-RA communications include chest trauma, infective endocarditis, and valvar replacement. This report describes a case of direct LV-RA and interventricular communications occurring three months after excision of a subaortic shelf.

Aorta↗
PubMed1986

Retrograde transfemoral catheterization of the left ventricle in children with aortic valve stenosis.

In 19 consecutive children with aortic valve stenosis, the left ventricle was entered retrogradely with a Gensini catheter guided by a tip-deflector guidewire which could produce any desirable degree of curvature at its tip. In all patients, the aortic valve was retrogradely traversed for measurement of the pressure gradient (mean gradient = 53 mmHg, mean valve area = 0.36 cm2), and left ventriculography. No complications were encountered. This technique is safe, simple, and effective in retrograde catheterization of the left ventricle in children with aortic stenosis.

Adolescent↗
PubMed1986

The postnatal development of the optic nerve in hamsters: an electron microscopic study.

The postnatal development of the optic nerve in the golden hamster has been examined using the electron microscope. The number of the optic fibres present in the optic nerve showed an initial increase during the first day after birth but it declined afterwards and tapered off after Day 16. At its peak on postnatal Day 1, there was an average of 314,629 axons in the optic nerve but when the animal reached adulthood only 109,587 fibres remained amounting to about 65% loss of the total fibre population. The period of axon loss coincided with the appearance of large patches of degenerated profiles in the optic nerve. The occurrence of the optic fibre loss has been implied to correlate with the time when the retinal projections were undergoing a dynamic reorganization at the target sites during the process of establishing the adult patterns of retinofugal connections.

Animals↗
PubMed1986

Abnormal radial artery in Down's syndrome.

Abnormal arterial patterns in the forearm were discovered in 12 of 77 patients (16%) with Down's syndrome. Eight patients had an enlarged anterior interosseous artery, the distal portion of which was palpable over the dorsum of the hand; in seven it was associated with absence of the radial artery and in one it coexisted with the radial and ulnar arteries. Three patients had a hypoplastic radial artery and a relatively dominant ulnar artery. One patient had a vestigial radial artery that ended as muscular branches in the forearm. The developmental aspects of these aberrations are discussed.

Adolescent↗
PubMed1986

An echocardiographic study of perimembranous ventricular septal defect with left ventricular to right atrial shunting.

Twenty nine patients with isolated perimembranous ventricular septal defects were investigated by M mode, cross sectional, and pulsed Doppler echocardiography. Tricuspid valve anomalies were present in all six patients with a left ventricular-right atrial shunt but in only six (26%) of 23 patients who had interventricular shunts only. Systolic flutter of the tricuspid valve was shown in five (83%) of the six patients with a ventriculoatrial shunt but not in the other patients. Systolic turbulence in both the right ventricle and right atrium was detected by Doppler echocardiography only in patients with ventriculoatrial shunting. A perimembranous ventricular septal defect with left ventricular to right atrial shunt can be diagnosed by its combined M mode, cross sectional, and pulsed Doppler echocardiographic features.

Adolescent↗
PubMed1986

The role of cross sectional echocardiography and pulsed Doppler ultrasound in the management of neonates in whom congenital heart disease is suspected. A prospective study.

The application of cross sectional echocardiography and pulsed Doppler ultrasound to the management of symptomatic neonates with suspected congenital heart disease was studied in 96 consecutive cases. The ability of echocardiography to establish a complete and accurate diagnosis and a correct management plan was evaluated. Sequential segmental analysis of data from cardiac catheterisation and necropsy identified 536 cardiovascular anomalies. Of the 536 anomalies 512 were correctly diagnosed by echocardiography (sensitivity 95.5%). Seven false positive echocardiographic diagnoses were made (specificity 98.6%). Nearly all the missing diagnoses and all the false positive diagnoses made by echocardiography were extracardiac vascular anomalies. Normal cardiovascular anatomy was at all times correctly identified by echocardiography. In 12 babies (12.5%) a management plan could not be established because of inconclusive echocardiographic findings. Of the 84 proposed plans based on the echocardiographic findings, eight were found to be inappropriate after catheterisation. Thus, 76 babies (79.2%) could have been correctly managed without cardiac catheterisation. The combination of cross sectional echocardiography and pulsed Doppler ultrasound not only allows diagnosis of congenital cardiac anomalies in most neonates but can facilitate appropriate clinical management. Only a minority of neonates with suspected congenital heart disease require cardiac catheterisation and angiography.

Aortography↗
PubMed1980

Univentricular heart of right ventricular type: clinical, angiographic and electocardiographic features.

The sequential chamber analysis and angiographic, hemodynamic and clinical features, including those seen on electrocardiography, are presented in 18 patients with a univentricular heart of right ventricular type. In all cases a main chamber with a right ventricular trabecular pattern received both (or the sole) atrioventricular (A-V) connections, and a rudimentary chamber with a left ventricular trabecular pattern receiving no A-V connection was also present. The 18 patients were seen between 1971 and 1979; 6 died and the diagnosis was confirmed at autopsy. Twelve patients had double inlet, four absent right and two absent left A-V connections. Electrocardiography revealed right ventricular hypertrophy in all, and 11 had a superior mean frontal QRS axis. Chest roentgenography disclosed dextrocardia in 7 and levocardia in 11. Of 12 infants presenting with a marked decrease in pulmonary flow, 10 presented as ill neonates with hypoxia and acidosis. Four infants with increased pulmonary flow presented before 8 weeks with heart failure and mild cyanosis. Two with moderate pulmonary stenosis had mild cyanosis, but were asymptomatic. All had associated cardiac anomalies, pulmonary stenosis and persistent ductus arteriosus being the most common. For accurate diagnosis, angiographic demonstration of a posterior rudimentary chamber in addition to the main chamber of right ventricular trabecular pattern is mandatory.

Abnormalities, Multiple↗
PubMed1980

An explanation for failure of impedance apnoea alarm systems.

24-hour recordings of the ECG and respiration, the latter from an impedance technique, have shown a phenomenon which could account for hitherto unexplained failures of impedance apnoea alarm systems. Whenever apnoea is accompanied by bradycardia there is a pronounced increase in the amplitude of the cardiac impulse on the respiration carrier. This imitates the respiration signal and prevents the alarm from sounding. Conversely, apnoea unaccompanied by bradycardia does not present this problem and is detected by the alarm. If impedance alarm systems are to be used to detect apnoea they must be accompanied by a heart rate (ECG) detector.

Apnea↗
PubMed1979

Dextrocardia--value of segmental analysis in its categorisation.

Dextrocardia can be defined as a heart in the right chest with the major axis to the right. This definition, however, conveys no information regarding the chamber arrangements and internal anatomy of the heart. Of 40 patients satisfying this definition in the files of the Brompton Hospital, 33 had angiocardiographic data adequate for complete analysis in terms of connections, relations, and morphology of cardiac segments. They form the subject of this report. There were 16 (48%) patients with situs solitus, 11 (33%) with situs inversus, and six (18%) with situs ambiguus. Of the cases of situs ambiguus, four exhibited laevoisomerism and two dextroisomerism. Of the 16 patients with situs solitus, six had two ventricles and 10 had univentricular hearts; two patients had concordant and three discordant ventriculoarterial connections, seven had double outlet ventricle, and four a single outlet heart. Of the 11 patients with situs inversus, nine had two ventricles and two a univentricular heart of right ventricular type; the arterial connection was concordant in two, discordant in two, double outlet in six, and single outlet in one. Of the six patients with situs ambiguus and laevo or dextroisomerism, four had two ventricles, and two univentricular hearts; the arterial connection was concordant in one, double outlet in three, and single outlet in two. Segmental analysis and the use of basic descriptive terms are essential to define the complex anatomy of such hearts.

Angiocardiography↗
PubMedDate not supplied

Primary intraventricular cardiac tumors in children: contemporary diagnostic and management options.

We reviewed the intraventricular cardiac tumors presenting at our institution between 1985-1991, studying the presentation, modes of investigation, and evidence of hemodynamic compromise. Thirteen patients presented with intraventricular tumors during the study period. Two of the tumors were rhabdomyosarcomas, one was a myxoma, and 10 were rhabdomyomas. All patients were evaluated with two-dimensional and pulsed Doppler echocardiography and B-color imaging was undertaken in three patients. Four patients presented for elective scans to complement investigations for tuberous sclerosis, seven patients had cardiac symptoms, and two patients presented prenatally. Obstruction to intracardiac flow was present in five patients. Two patients had the tumor excised and one had an open biopsy of the tumor. One patient had an transvascular biopsy at cardiac catheter. Early detection of cardiac tumors is increasing, particularly rhabdomyomas. With fetal echocardiography, more patients should come to attention prenatally. B-color may be useful addition in assessing cardiac tumors, aiding detection and definition of intramural lesions.

Child↗
PubMedDate not supplied

Radiofrequency catheter ablation of right ventricular outflow tract tachycardia in a preschooler.

A 3-year-old girl presented with a febrile illness complicated by right ventricular outflow tract tachycardia, which persisted after resolution of the presumed viral infection. The tachycardia was intermittent, but was significantly exacerbated by exercise. Radiofrequency ablation (RFA) of the ectopic focus was successfully performed and the child remains free of tachycardia 12 months later. A review of the literature suggests that RFA in children is increasingly seen as a safe and convenient option for the treatment of supraventricular tachycardia, whereas the management of ectopic ventricular tachycardia in pediatric practice has not been well defined.

Catheter Ablation↗
PubMedDate not supplied

Aorto-pulmonary window.

Aorto-pulmonary window (septal defect) is an uncommon congenital cardiac malformation accounting for only about 0.5% of the cases of congenital heart disease catheterised at our institution. Of 15 patients with this anomaly eight had associated cardiac malformations. Three patients presented in the neonatal period and in these patients the other cardiac anomalies (aortic interruption in two, pulmonary atresia in one) determined the clinical presentation and haemodynamic disturbance. A second group of five patients presented with heart failure during infancy and in these patients additional anomalies, present in three, were "incidental" findings. A third group of seven patients with similar physical signs but without heart failure did not present until after the first year of life and all were asymptomatic. Associated anomalies, present in two, were again "incidental" in that they did not influence the presentation. Of 12 patients without serious associated anomalies, five, operated on before 1970, had division and suture of the aorto-pulmonary window with one death. In two the defect was patched from the pulmonary artery but one required re-closure from the aorta. In six the defect was successfully patched from the aorta, which is now the preferred technique.

Adolescent↗