Biomedical subjects

K L Chan

Publications and source records attributed to K L Chan.

248 records · Page 14Linked to original sources

PubMedDate not supplied

Application of transthoracic and transesophageal echocardiography in the diagnosis and management of infective endocarditis.

Infective endocarditis continues to be a cause of significant cardiac morbidity and mortality. To improve the prognosis of patients with this disorder, early diagnosis is crucial but difficult to establish on the basis of clinical parameters alone. Echocardiography, both transthoracic and transesophageal techniques, has a major role in the detection of vegetations that are the hallmark of endocarditis. Valvular and perivalvular complications can also be well assessed by echocardiography. With the improved resolution provided by recent technologic advances in echocardiography, vegetations can be reliably detected in most patients with endocarditis. We propose that present diagnostic criteria for endocarditis be revised to include echocardiographic findings as a major parameter in the diagnosis. Finally, a diagnostic approach incorporating transthoracic and transesophageal echocardiography in these patients will be discussed taking into consideration the different degrees of clinical suspicion for the existence of the disease.

Diagnosis, Differential↗

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Spontaneous drainage of paravalvular abscess diagnosed by transesophageal echocardiography.

Paravalvular abscesses, which occur in up to 30% of cases of native valve endocarditis, are being detected with increasing frequency with the use of transesophageal echocardiography. Abscesses of the mitral aortic intervalvular fibrosa have been described but only in association with native or prosthetic aortic valve endocarditis. We describe a patient with native mitral valve endocarditis complicated by an abscess in the fibrosa. A 51-year-old diabetic man presented with Staphylococcus aureus mitral valve endocarditis. A transesophageal echocardiographic study done 8 days after admission revealed two large masses at the base of the anterior mitral leaflet with extension into the fibrosa consistent with a paravalvular abscess that was not detected by precordial echocardiography. A repeat transesophageal echocardiographic study done 20 days after admission showed spontaneous drainage of the abscess and a subsequent fistula between the left atrium and left ventricle. This case highlights the important role that transesophageal echocardiography has in suspected and known cases of endocarditis. Its major advantage of delineating posterior cardiac structures allowed accurate diagnosis and serial evaluation of this previously unreported complication of endocarditis.

Abscess↗

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Biplane transesophageal echocardiography: clinical applications of the long-axis plane.

Tomography of the heart and great vessels is limited during conventional transesophageal echocardiography by the inability to rotate the transducer at the end of the transesophageal echocardiographic endoscope. A biplane transesophageal echocardiographic probe has been developed recently with a second transducer capable of long-axis imaging that yields long-axis views in addition to the familiar short-axis views. We describe our experience with 37 patients with a variety of cardiovascular diseases. In 17 patients new diagnostic information was obtained, although management was not changed. Long-axis scanning was particularly useful in the assessment of diseases of the thoracic aorta, valvular morphology and regurgitation, and congenital heart disease. Important limitations of the biplane imaging system include reduced image quality and a continued inability to rotate the transducer to obtain any desired plane of imaging. Nonetheless, biplane imaging enhances the versatility of transesophageal echocardiography and improves three-dimensional conceptualization of cardiac disease.

Aortic Diseases↗

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Canadian consensus recommendations for the measurement and reporting of diastolic dysfunction by echocardiography: from the Investigators of Consensus on Diastolic Dysfunction by Echocardiography.

Abnormalities of diastolic filling are increasingly recognized as a cause of symptoms and predictors of outcome in patients with most forms of heart disease. Noninvasive assessment of diastolic filling is possible in almost all patients, but accurate evaluation must relate echocardiographic Doppler measurements to the complex physiologic and hemodynamic factors responsible for normal and abnormal filling. This evaluation has been facilitated by recent correlation of Doppler measurement of mitral and pulmonary venous inflow with hemodynamic studies. These studies have confirmed that when a careful, integrated approach is taken, Doppler flow patterns can document a progressive pattern of abnormality in many conditions. Impaired left ventricular (LV) relaxation is seen early and is recognized by a decrease in early transmitral LV filling and an increased proportion of filling during atrial contraction. As abnormalities progress, increasing LV chamber stiffness and elevated left atrial pressure lead to a "pseudonormal" filling pattern that previously has caused considerable confusion. This can be unmasked by careful evaluation of pulmonary venous inflow and the use of the Valsalva maneuver. When marked diastolic abnormalities are present, LV filling has restrictive features characterized by rapid early filling, a very stiff left ventricle with high filling pressures, and a poor prognosis. Routine measurement of indexes of diastolic filling have been hampered by uncertainty as to what should be measured, what techniques should be used, definition of normal values, and a clear method of reporting findings. This report represents the efforts of a Canadian consensus group to define a national standard for the performance and reporting of echocardiographic Doppler studies of diastolic filling.

Aged↗

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Sonicated albumin in exercise echocardiography: technique and feasibility to enhance endocardial visualization.

Left ventricular cavity opacification can be produced by the intravenous injection of sonicated albumin (Albunex 422). A recent study suggested that sonicated albumin may be useful in dobutamine stress echocardiography, but its use in exercise echocardiography has not been reported. The purposes of the study were to assess the feasibility of using Albunex to enhance endocardial visualization and to evaluate the factors affecting Albunex kinetic in exercise echocardiography. Fifteen healthy volunteers underwent two exercise echocardiograms on the same day, with intravenous injection of Albunex during one of the studies. Two injections up to a maximum of 20 ml of Albunex per injection were given to enhance the four- and two-chamber views, both at rest and immediately after exercise. The degree of left ventricular enhancement and the percentages of endocardial visualization were measured in both resting and exercise images. Variables relating to the kinetics of Albunex, which included volume of contrast injected, transit time, heart rate, and cardiac output at the time of image acquisition, were also assessed. There was no difference in the image acquisition time between the two exercise echocardiograms. Albunex produced good left ventricular opacification both at rest and after exercise. More endocardial border was visualized with contrast injection than without (91.2% +/- 11.5% vs 85.8% +/- 14.2%, p = 0.007). The transit times and volumes of Albunex injected were significantly less after exercise than at rest. The parameters were inversely related to heart rate and cardiac output. In conclusion, intravenous injection of Albunex is a promising means to enhance left ventricular endocardial visualization in exercise echocardiography and can be readily incorporated without causing a significant delay in obtaining images after exercise. Whether its use can improve diagnostic accuracy of exercise echocardiography requires further studies.

Adult↗

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Computed tomography of the superior mesenteric artery syndrome.

An acute presentation of the superior mesenteric artery syndrome was diagnosed in a 13-year-old Chinese boy in whom no predisposing cause was found at surgery. Duodenogram combined with dynamic computed tomography, including 2-dimensional multiplanar reconstructions, was useful in confirming the diagnosis prior to definitive surgery.

Acute Disease↗

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Plants as sources of antimalarial drugs, Part 4: Activity of Brucea javanica fruits against chloroquine-resistant Plasmodium falciparum in vitro and against Plasmodium berghei in vivo.

Extracts of Brucea javanica fruit have been prepared and monitored for their in vitro and in vivo antiplasmodial activities. The antimalarial activity of the fruit was found to be attributable to its quassinoid constituents. Nine of the quassinoids possessed in vitro IC50 values between 0.046-0.0008 microgram/ml against the chloroquine resistant Plasmodium falciparum strain (Kl) tested. The two quassinoid glycosides tested were considerably less active in vitro than the aglycones. Four quassinoids were found to possess activity in vivo against Plasmodium berghei infections in mice after oral dosing. All five quassinoids tested in vivo showed some toxicity.

Animals↗

PubMedDate not supplied

Octreotide therapy for pancreaticopleural fistula.

Pancreaticopleural fistula is a rare but remediable complication of pancreatitis. Hitherto, treatment by means of total parenteral nutrition and thoracocentesis had resulted in an overall success rate of 40% only. Surgical obliteration of persistent fistulae is required in many cases, as the underlying pancreatic duct lesion often prevents spontaneous closure of the fistula. We report a patient suffering from pancreaticopleural fistula with a tightly strictured pancreatic duct. The fistula was successfully obliterated with the use of octreotide addition to thoracocentesis and total parenteral nutrition. Pancreatic bypass surgery was later performed only for pain relief. We believe that octreotide can effectively suppress pancreatic secretion and promote closure of pancreaticopleural fistula even in the presence of severe pancreatic duct lesions. Thus the risk of infection and early surgery for persistent fistula can be minimized.

Adult↗

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Ultrasound-guided hydrostatic reduction of childhood intussusception: technique and demonstration.

The authors review the technique of ultrasound-guided hydrostatic reduction of childhood intussusception and illustrate, in real-time fashion, the treatment of three cases with this technique. Two cases of successful reduction of ileocolic intussusception are demonstrated. The third case is an example of the complex fronded appearance of ileo-ileocolic intussusception and failed reduction. This technique is recommended as an alternative method for the treatment of childhood intussusception, as it does not involve ionizing radiation and is a simple and safe procedure.

Enema↗

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Variability in schizonticidal drug susceptibility amongst clones and isolates of Plasmodium falciparum.

Plasmodium falciparum isolates from Malaysia, Africa and Thailand were cultured in vitro following the method of Trager and Jensen and subsequently cloned using the limiting dilution method of Rosario. These clones were presently characterized against three schizonticidal drugs, chloroquine, mefloquine and quinine, using the modified in vitro microtechnique. Results showed that all the clones derived from Gombak A isolate were chloroquine-resistant with average IC50 values ranging at 0.1377-1.0420 microM (0.007-0.058 mefloquine activity), sensitive to mefloquine at 0.0032-0.0103 microM and quinine at 0.0025-0.0428 microM (0.075-3.080 mefloquine activity). Similarly, the TGR clone displayed resistance to chloroquine at 0.1715-0.5875 microM (0.002-0.029 mefloquine activity) but were also sensitive to mefloquine at 0.0008-0.0058 microM and quinine at 0.0055-0.0700 microM (0.055-0.202 mefloquine activity). In contrast, four out of six Gambian clones were sensitive to chloroquine at 0.0047-0.0172 microM (0.122-0.617 mefloquine activity) but all were sensitive to mefloquine at 0.0008-0.0029 and 0.0016-0.0102 microM (0.096-1.813 mefloquine activity). In general, most of the clones displayed susceptibility patterns similar to that of their parent isolates against the three schizonticidal drugs except Gm/B2 and Gm/H5 Gambian clones were chloroquine-resistant at 0.3427 microM (0.006 mefloquine activity) and 0.2260 microM (0.004 mefloquine activity), respectively. Further results indicated that they were pure clones compared to their parent isolates as their schizonticidal drug susceptibilities were statistically different (p < 0.05) except Gm/C6 and TGR/B7 clones against mefloquine (p < 0.05).

Animals↗

PubMedDate not supplied

Susceptibility of Malaysian Plasmodium falciparum isolates to antimalarial drugs after cryopreservation and 12 months of continuous in vitro culture.

Eleven Malaysian Plasmodium falciparum isolates were cultured in vitro and later subjected to antimalarial evaluations in 96-well microtiter plates. After cryopreservation, the IC50 (nM) for ST 195, ST 196, ST 197, ST 244 and ST 245 isolates were, respectively: 180.9, 198.7, 482.0, 580.0 and 690.1 for chloroquine; 3.4, 3.4, 9.2, 4.0 and 5.8 for mefloquine; 21.9, 10.5, 40.7, 40.1 and 48.7 for quinine; 136.7, 58.8, 116.4, 29.4 and 95.4 for cycloguanil, and 48.3, 57.5, 47.4, 61.5 and 37.8 for pyrimethamine. Before cryopreservation they were 172.5, 141.5, 453.2, 636.0 and 651.6 nM for chloroquine; 4.8, 2.6, 9.0, 6.9 and 5.8 nM for mefloquine; 21.3, 8.3, 41.9, 49.6 and 40.1 nM for quinine, 129.9, 47.3, 109.3, 30.6 and 95.4 nM for cycloguanil, and 45.4, 47.4, 40.2, 66.3 and 36.0 nM for pyrimethamine. IC50 (nM) for Gombak A, Gombak C, ST 9, ST 12, ST 85 and ST 148 isolates after 12 months of continuous in vitro culture were, respectively: 477.0, 492.3, 367.1, 809.4, 566.5 and 341.8 for chloroquine; 2.9, 11.1, 8.5, 16.9, 5.3 and 4.2 for mefloquine; 6.2, 58.3, 52.7, 36.7, 31.8 and 26.2 for quinine; 154.5, 57.2, 130.3, 94.2, 81.4 and 102.9 for cycloguanil, 26.9, 24.9, 43.8, 31.0, 14.1 and 56.7 for pyrimethamine. Before the 12-month culture they were 472.3, 452.9, 352.7, 773.7, 702.7 and 322.7 nM for chloroquine; 2.6, 13.2, 8.5, 17.2, 5.0 and 4.0 nM for mefloquine; 6.2, 85.4, 53.9, 38.5, 35.8 and 38.5 nM for quinine; 106.8, 74.3, 112.4, 89.8, 91.8 and 103.3 nM for cycloguanil, and 26.9, 31.4, 47.0, 28.1, 14.9 and 56.7 nM for pyrimethamine. Thus none of these isolates differed in their original susceptibilities after either of these procedures.

Animals↗

PubMedDate not supplied

Noninvasive assessment of prosthetic heart valves.

Objective assessment of prosthetic valvular function is crucial in the patient with a prosthetic heart valve. Combined two-dimensional echocardiography and Doppler examination is the imaging modality of choice in this setting because it provides detailed anatomic and hemodynamic information. These procedures allow detection of valve related complications as well as subclinical prosthetic dysfunction. Combined Doppler echocardiography should be an essential part of the follow-up of these patients.

Aortic Valve↗

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Comprehensive assessment of cardiac anatomy in anesthetized patients by transesophageal echocardiography.

Transesophageal echocardiography (TE) is a new imaging modality which provides a unique acoustic window to assess cardiac structures. The feasibility of using TE to obtain eight tomographic views of the heart was examined prospectively in 25 patients within 4 h following cardiac surgery. With the exception of the left ventricular apical view, which was not obtainable in 32% of patients, all views were present in each patient. Thus, TE not only provides a comprehensive assessment of cardiac anatomy, but also allows detailed left ventricular regional wall motion evaluation in the majority of patients.

Cardiac Surgical Procedures↗

PubMedDate not supplied

Liver transplantation--perspective from Hong Kong.

BACKGROUND/AIMS: We report our experience of 27 orthotopic liver transplantations in 26 patients performed at Queen Mary Hospital, Hong Kong during the period of October 1991 to October 1995. PATIENTS AND METHODS: There were 19 adults and 7 pediatric patients with a mean age of 29 years (range 8 months to 62 years). The underlying liver diseases of the 26 patients were biliary atresia (n = 6), Alagille syndrome (n = 1), primary biliary cirrhosis (n = 2) cryptogenic cirrhosis (n = 2), alcoholic cirrhosis (n = 5), Wilson's disease (n = 1), fulminant hepatic failure (n = 3), polycystic liver (n = 2), secondary biliary cirrhosis (n = 1), HBV cirrhosis (n = 2) and autoimmune hepatitis with hepatocellular carcinoma (n = 1). The pathology leading to re-transplantation in a pediatric patient was post-transplant hepatitis of unknown etiology. The liver grafts were obtained from 19 brainstem dead and 8 living donors. The pediatric patient requiring re-transplantation received a left lateral segment graft from her mother. Two adults received left lobe grafts from their family members. RESULTS: The overall graft survival is 88% and patient survival is 92%. There were only 2 deaths: one patient developed primary graft nonfunction and died from intracerebral bleeding 39 days after transplantation and the other died from graft rejection resistant to salvage by steroid pulse and OKT3. The other patients are well with functioning grafts. CONCLUSIONS: We hope that the current success rate can convince people in our locality in cadaveric organ donation so that living donors do not run the risk of dying from the operation, although the risk is estimated to be very small.

Adult↗