Biomedical subjects

D P Chan

Publications and source records attributed to D P Chan.

At least 19 recordsLinked to original sources

PubMed2001

Sonography of the normal scapholunate ligament and scapholunate joint space.

PURPOSE: The aims of this study were to assess the visibility of the normal scapholunate ligament on sonography and to establish the normal scapholunate joint space width in the neutral position and radial and ulnar deviation. METHODS: Two hundred normal wrists in 100 subjects (55 men and 45 women; mean age, 40 years; range, 19-83 years) were examined with high-resolution sonography (5-12-MHz linear-array transducer). The visibility and thickness of the scapholunate ligament were recorded. The width of the scapholunate joint space, or interval, was measured in the neutral position and radial and ulnar deviation. The width of the distal radius was recorded as a comparative standard for the patients' body habitus. RESULTS: The dorsal scapholunate ligament was completely (100%) visible in 95 wrists (48%), partially (> or = 50%) visible in 60 (30%), barely (< 50%) visible in 15 (8%), and not visible in 30 (15%). The volar scapholunate ligament was completely visible in 13 wrists (7%), partially visible in 17 (9%), barely visible in 15 (8%), and not visible in 151 (76%). The proximal component of the ligament was not visible in any subject. Measurement of the scapholunate interval was limited by the lack of identifiable anatomic marks for reference. The mean width of the dorsal scapholunate interval was 4.2 mm (range, 2.3-6.3 mm) in the neutral position. The interval did not differ more than 2.5 mm between the left and right wrists. No predictable change in width on ulnar or radial deviation was evident. The mean scapholunate intervals and mean distal radial width were significantly wider in men than in women and on the right side than on the left side. CONCLUSIONS: The dorsal scapholunate ligament is completely or partially visible in 78% of normal wrists. Its detection following injury may help to exclude the possibility of scapholunate dissociation. There is a quite wide variation in scapholunate interval widths on sonography and an unpredictable response with stress testing. The absence of a visible scapholunate ligament on sonography does not indicate injury.

Adult↗

PubMed2001

Association of human beta-herpesviruses with the development of cervical cancer: bystanders or cofactors.

BACKGROUND/AIM: Human papillomaviruses (HPVs) are important, but not sufficient, for the development of cervical cancer. All three human beta-herpesviruses--cytomegalovirus (CMV) and human herpesviruses (HHV) types 6 and 7--have been detected in the cervix. In addition, CMV and HHV-6 can interact with HPVs in vivo. This study examined the possible role of beta-herpesviruses in cervical cancer development. METHODS: HPV, CMV, HHV-6, and HHV-7 were detected by the polymerase chain reaction using cervical scrapes taken at colposcopy from 388 women. HPV types were identified using restriction fragment length polymorphisms. Colposcopy guided biopsies were taken from abnormal areas, and the histological findings were regarded as the final diagnoses. The associations between herpesvirus infection and the degree of cervical lesion were analysed with respect to HPV status. RESULTS: Of the 388 women, 51.8% had a normal cervix, 14.4% had cervical intraepithelial neoplasia grade 1 (CIN1), 8.2% had CIN2, 19.3% had CIN3, and 6.2% had invasive carcinoma. Overall, the positive rates for high, intermediate, and low risk HPVs were 18.8%, 21.4%, and 5.2%, respectively. Fifteen patients harboured HPVs for which the genotype could not be identified. Positive rates for CMV, HHV-6, and HHV-7 were 9.5%, 3.6%, and 3.4%, respectively. HPV positive patients carried a higher risk for high grade lesions (CIN2/3 or carcinoma) (odds ratio (OR), 5.24; 95% confidence interval (CI), 3.19 to 8.62; chi 2 = 51.79; p < 0.001), whereas those positive for CMV, HHV-6, or HHV-7 did not. Thirteen of 131 patients with high grade lesions had HPV/herpesvirus coinfections, but no association with the cervical lesion was noted. Furthermore, positive rates for herpesviruses among HPV negative, high/intermediate risk HPV negative, and high risk HPV negative subgroups were similarly low and without a significant association. CONCLUSIONS: The ubiquitous nature of herpesviruses may pose difficulty in elucidating their pathogenic role. These results indicate that CMV, HHV-6, and HHV-7 are bystanders rather than cofactors in the oncogenesis of cervical cancer.

Adolescent↗

PubMed2001

Evaluation of extraction methods from paraffin wax embedded tissues for PCR amplification of human and viral DNA.

AIM: To evaluate the efficiency of phenol/chloroform, microwave, and Qiagen spin column based DNA extractions from paraffin wax embedded tissue for use in the polymerase chain reaction (PCR). In addition, to assess the reliability of amplifying a housekeeping gene to indicate successful viral DNA extraction. METHODS: DNA samples extracted from 20 blocks of cervical carcinoma tissues using the three methods were subjected to PCRs targeting 509 bp and 355 bp of the beta globin gene, and 450 bp and 150 bp of human papillomavirus (HPV) DNA. RESULTS: Microwave extraction showed the highest positive rate for beta globin PCR, whereas the spin column method was the most efficient for HPV DNA extraction. When the 509 bp beta globin and 450 bp HPV PCR results were correlated, two of 10, eight of 12, and nine of 10 beta globin positive extractions prepared by means of the phenol/chloroform, microwave, and spin column methods, respectively, yielded HPV DNA of the expected size. For the beta globin negative samples, HPV was detected in three of 10, two of eight, and four of 10 samples. CONCLUSIONS: HPV DNA extraction was most efficient using the Qiagen spin column and had the highest positive predictive value when a housekeeping gene was used as an indicator of successful viral DNA extraction; the phenol/chloroform method was the least efficient. The potential drawbacks of some extraction methods when using a human housekeeping gene to assess the quality of viral DNA extraction need to be considered.

Carcinoma, Squamous Cell↗

PubMed2000

Importance of atrial flutter isthmus in postoperative intra-atrial reentrant tachycardia.

BACKGROUND: In survivors of congenital heart surgery, intra-atrial reentrant tachycardia (IART) often develops. Previous reports have emphasized the atriotomy scar as the central barrier around which a reentrant circuit may rotate but have not systematically evaluated the atrial flutter isthmus in such patients. We sought to determine the role of the atrial flutter isthmus in supporting IART in a group of postoperative patients with congenital heart disease. METHODS AND RESULTS: Nineteen postoperative patients with IART underwent electrophysiological studies with entrainment mapping of the atrial flutter isthmus for determining postpacing intervals. Radiofrequency ablation was performed at the identified isthmus in an effort to create a complete line of block. Twenty-one IARTs were identified in 19 patients, with a mean tachycardia cycle length of 293+/-73 ms. The atrial flutter isthmus was part of the circuit in 15 of 21 (71. 4%). In the remaining 6 of 21, the ablation target zone was at sites near atrial incisions or suture lines. Ablation was successful in 19 of 21 (90.4%) IARTs and in 14 of 15 (93.3%) cases at the atrial flutter isthmus. CONCLUSIONS: In most of our postoperative patients, the atrial flutter isthmus was part of the reentrant circuit. The fact that the atrial flutter isthmus is vulnerable to ablation suggests that whenever IART occurs late after repair of a congenital heart defect, the atrial flutter isthmus should be evaluated. These data support the theory that some form of conduction block between the vena cava is essential for the establishment of a stable substrate for the atrial flutter reentrant circuit.

Adolescent↗

PubMed1998

Oral fluid therapy. A promising treatment for vasodepressor syncope.

OBJECTIVE: To investigate the predictive value of an intravenous fluid bolus during tilt table testing on clinical outcome and to evaluate of oral therapy is an effective treatment for patients with vasodepressor syncope. DESIGN: Retrospective cohort. SETTING: Regional pediatric cardiology outpatient clinic. PATIENTS: Patients (N = 58) with a positive baseline tilt table testing result who were treated with oral fluid therapy between February 1991 and March 1996. INTERVENTIONS AND MAIN OUTCOME MEASURES: Patients with a positive tilt table test result were given an intravenous bolus of isotonic saline solution. Responders were identified as having a negative tilt table test result after the bolus. Patients were prescribed a protocol of oral fluid therapy. Data were obtained from the medical record and a mailed survey. RESULTS: Of the 58 subjects, 90% had no recurrent syncope while receiving oral fluid therapy. During tilt table testing, the mean decrease in mean arterial pressure seen with symptomatic events was lower after the intravenous fluid. The heart rate, which dropped during the initial test, increased during the rests after the intravenous bolus. In the nonresponders, symptomatic episodes occurred significantly later in the tilt table test when given fluids. The response to intravenous fluid bolus had positive predictive value of 92% and negative predictive value of 11% of clinical outcome. CONCLUSIONS: Our data suggest that oral fluid therapy is an effective treatment for vasodepressor syncope in our population. Fluid bolus response during tilt table testing has a high positive but a low negative predictive value of response to oral fluid therapy. We now recommend oral fluid therapy as a primary intervention and reserve tilt table testing for oral fluid therapy failures.

Adolescent↗

PubMed1998

Halm-Zielke instrumentation for primary stable anterior scoliosis surgery: operative technique and 2-year results in ten consecutive adolescent idiopathic scoliosis patients within a prospective clinical trial.

Halm-Zielke instrumentation (HZI) was developed to eliminate the disadvantages of Zielke instrumentation (VDS) in terms of lack of primary stability and a kyphogenic effect. HZI is an anterior double-rod system. The system is composed of a lid-plate, which is fixed at the lateral aspect of the vertebral body with two screws, a sunk screw anteriorly and a VDS screw posteriorly. The lid-plate design provides the lowest possible implant profile. The longitudinal components consist of a threaded VDS rod and a solid, fluted rod. Correction is performed with the threaded rod and the solid rod. The solid rod allows internal derotation and relordosation, eliminates the Zielke three-point lever system and augments the system. The fluted design of the rod provides rotatory stability. This is a report of the first ten consecutive adolescent idiopathic scoliosis patients in a prospective clinical trial using HZI with a minimum follow-up of 2 years. Curves ranged from 36 degrees to 77 degrees. Correction of the frontal plane averaged 77.5% and 72.2% postoperatively and at follow-up, respectively. Thoracolumbar kyphosis was present in three patients and corrected in all from an average of +18 degrees to +1.7 degrees at follow-up. Implant-related complications were not observed. All patients were treated without any additional external immobilization. In our opinion, HZI is a major improvement on the original Zielke VDS. It eliminates the kyphogenic effect and provides primary stability.

Adolescent↗

PubMed1997

Digital acoustic analysis of precordial innocent versus ventricular septal defect murmurs in children.

This study examines whether digital acoustic analysis of individual cardiac sound components for intensity, timing, and frequency could differentiate between innocent and pathologic murmurs. With use of this new technology, sensitive and specific criteria can be established for a fast and easy screening procedure to help differentiate between innocent and ventricular septal defect murmurs in children with suspected heart disease.

Adolescent↗

PubMed1997

Effects of commonly used adrenergic agonists on left ventricular function and systemic vascular resistance in young piglets.

This study compared the effects of high-dose infusions of various adrenergic agonists on cardiovascular function in piglets. We hypothesized that agonists would have different effects on systolic, diastolic, and vascular functions. Nine anesthetized 3-week-old piglets underwent cardiac catheterization. Manometric and conductance catheters measured pressures and volumes. Data were acquired at rest and during infusions of epinephrine, norepinephrine, dopamine, dobutamine, isoproterenol, and phenylephrine. End-systolic elastance, preload-recruitable stroke work, cardiac output, the maximum and minimum derivatives of left ventricular pressure, the relaxation constant tau, peak filling rate, and end-diastolic stiffness were obtained. Contractile efficiency and the cardiac output/pressure-volume area ratio were calculated. Regression was used for analysis of variance; p < 0.05 was considered significant. All agonists increased indexes of contractility. beta-Adrenergic agonists enhanced relaxation. Isoproterenol and dopamine increased efficiency. No drug changed diastolic stiffness. Therefore both alpha-adrenergic and beta-adrenergic agonists have inotropic effects in the 3-week-old piglet. Some beneficial effects of beta-agonists on cardiac output may be due to enhancement of relaxation and to afterload reduction. Various agents exert different effects on the cardiovascular system, and these differences may be clinically important.

Adrenergic Agonists↗

PubMed1997

Left ventricular systolic function, arterial elastance, and ventricular-vascular coupling: a developmental study in piglets.

Circulatory changes occur during perinatal life that increase cardiac output and left ventricular contractile reserve. To examine postnatal changes in left ventricular systolic function and ventricular-vascular coupling, piglets underwent cardiac catheterization at 1, 2, 4, and 6 wk of age. We measured end-systolic elastance (Ees), preload-recruitable stroke work, dP/dt(max), the dP/dt(max) end-diastolic volume relation, cardiac index, heart rate, arterial elastance (Ea), and the ratio Ea/Ees, at rest, during isoproterenol infusions (0.05-1.0 microg/kg/min), and after propranolol (1 mg/kg i.v.). Resting heart rate and cardiac index decreased between 1 and 6 wk. In 1 wk olds, resting Ees was at maximum and was unchanged during isoproterenol infusion; isoproterenol increased other contractility indices. Two, 4, and 6 wk olds demonstrated reserve using all contractility indices. Contractile efficiency was not different between ages. In 1 wk olds, Ea decreased during isoproterenol infusion; isoproterenol did not change Ea at 6 wk. Ea/Ees was higher at rest at 6 wk than at 1 wk, and fell significantly on isoproterenol; isoproterenol did not change Ea/Ees at 1 wk. With beta-adrenergic stimulation, 1 wk olds increased cardiac index by increasing heart rate and decreasing afterload, 6 wk olds increased cardiac index by increasing heart rate and contractility; no change in contractile efficiency was found in either group. In summary, contractile reserve is limited at 1 wk when measured by Ees, but other indices demonstrated reserve. Indexed Ea falls in response to beta-adrenergic stimulation in all ages but 6 wk. Ventricular-vascular coupling is optimized at 1 wk even under baseline conditions.

Adrenergic beta-Agonists↗

PubMed1996

Safety of thoracic transverse process fixation: an anatomical study.

An anatomical study of the passage of the implant placed around thoracic transverse process was undertaken in human cadavers to investigate the safety of thoracic transverse process fixation. A simulated surgical procedure for implant placement around the transverse processes of T1-T10 was carried out in eight fresh human cadavers using a mock plastic implant, 7.0 mm wide and 1.5 mm thick. A total of 80 implanted thoracic vertebrae were dissected systematically. One implanted spinal column was sectioned sagittally through the costotransverse space. The parietal pleura, the intercostal vessels, and intercostal nerves were not injured by the implants in any of the specimens. All the implants were located posterior to the intercostal nerves and vessels, lateral to the pedicles, and outside the spinal canal. The transverse processes of T1-T10 are safe structures for implant anchorage in posterior spinal instrumentation.

Aged↗

PubMed1995

Surgical approaches for the correction of unstable thoracolumbar burst fractures: a retrospective analysis of treatment outcomes.

The authors retrospectively studied 49 nonparaplegic patients who sustained acute unstable thoracolumbar burst fractures. All patients underwent surgical treatment and were followed for an average of 27 months. All but one patient achieved solid radiographic fusion. Three treatment groups were studied: the first group of 16 patients underwent anterior decompression and fusion with instrumentation; the second group of 27 patients underwent posterior decompression and fusion; and the third group of six patients had combined anterior-posterior surgery. Prior to surgical intervention, these groups were compared and found to be similar in age, gender, level of injury, percentage of canal compromise, neurological function, and kyphosis. Patients treated with posterior surgery had a statistically significant diminution in operative time and blood loss and number of units transfused. There were no significant intergroup differences when considering postoperative kyphotic correction, neurological function, pain assessment, or the ability to return to work. Posterior surgery was found to be as effective as anterior or anterior-posterior surgery when treating unstable thoracolumbar burst fractures. Posterior surgery, however, takes the least time, causes the least blood loss, and is the least expensive of the three procedures.

Adolescent↗

PubMed1994

Coronary artery fistula in the pediatric age group: a 19-year institutional experience.

Ten patients with coronary artery fistulae were identified from records at Columbus Children's Hospital between 1974 and 1993. Clinical presentations of patients were quite variable, from 1 day to 20 years of age. Symptoms ranged from none to severe cardiorespiratory failure requiring extracorporeal membrane oxygenation. Long term follow-up revealed one sudden death and one spontaneous closure of the fistula. This lesion should be ruled out in patients who present as extracorporeal membrane oxygenation candidates. Patients with mild forms of this lesion may be followed up medically if the left to right shunt is inconsequential, because spontaneous closure is a possibility. Because of the risk of sudden death, close long-term follow-up is mandatory even for operated patients, and antiplatelet therapy should be considered for these patients.

Adult↗

PubMed1994

Use of cardiac catheterization in pediatric cardiac surgical decisions.

Current practice patterns relating to pediatric cardiac catheterization (Cath) have considerable economic implications. The decreased cost and risk of noninvasive methods such as echocardiography (ECHO) and magnetic resonance imaging (MRI) make them attractive alternative diagnostic methods if they can sufficiently define cardiac anatomy and the need for surgical intervention. We reviewed a recent cardiac surgical series of 465 cases in 1.5 years to determine how often a Cath was performed prior to surgery. Overall, 59.4% of the procedures were preceded by a Cath (76% of open heart operations, and 26.7% of closed heart operations). We specify the situations where we feel enough information is available for preoperative decision making from non-invasive testing, and we present some diagnostic pitfalls that have been encountered.

Cardiac Catheterization↗

PubMed1994

Effects of renin-angiotensin system in mediating endothelin-induced renal vasoconstriction: therapeutic implications.

PURPOSE: Experiments were designed to determine whether angiotensin converting enzyme inhibition with quinaprilat can prevent endothelin-mediated decreases in renal blood flow and the glomerular filtration rate in the anesthetized dog. METHODS: To mimic the activation of the renal endothelin system that occurs in a number of cardiorenal disease states, endothelin was administered intrarenally in a group of mongrel dogs. Quinaprilat, the major active metabolite of quinapril, was infused in a separate group. One kidney (group 1) or both kidneys (group 2) were exposed in order to measure renal blood flow by an electromagnetic flow probe. Mean arterial blood pressure was measured through a catheter in a femoral vein. Blood samples were taken to determine plasma renin activity. Urine was collected. RESULTS: The infusion of endothelin decreased renal blood flow and the glomerular filtration rate and increased renal vascular resistance. These renal vascular responses were associated with increased plasma renin activity, indicating activation of the renal renin-angiotensin system. Quinaprilat attenuated the renal vascular responses. CONCLUSIONS: These studies provide further evidence of the importance of the renal renin-angiotensin system in mediating the renal vasoconstrictor actions of endothelin and indicate the therapeutic potential for quinapril in opposing the actions of endothelin in states of excessive endothelin activation.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1993

Nonoperative treatment in burst fractures of the lumbar spine (L2-L5) without neurologic deficits.

A retrospective review of 20 patients treated nonoperatively for burst fractures of the lumbar spine (L2-L5) was performed. All patients were neurologically intact at the time of injury. Follow-up averaged 3.9 years with a range of 2.1 to 9.1 years. Fourteen patients were men and six were women. The average age at injury was 35.8 years (8-67 years). Sixty-five percent of the injuries were the result of motor vehicle accidents and 35% falls from height. Fifty-five percent were two-column injuries and 45% three-column injuries. Kyphotic deformity averaged 8 at injury (-7 to 30) and 9.6 at follow-up (-8 to 33). Computed tomography scans were performed in nine patients during evaluation of injury. Spinal canal compromise averaged 40% (18-75%). Eighteen patients (90%) were considered to have a good to excellent functional outcome, whereas two patients had a fair outcome. No patient had a poor outcome. In no patient did neurologic deterioration or symptomatic spinal stenosis develop. Twenty-five percent of patients had no back pain, 70% mild back pain, and 5% moderate back pain. No patient was totally incapacitated by pain. Of those employed, all returned to full-time work. Nonoperative treatment should be considered as an alternative in the treatment of lumbar burst fractures (L2-L5) in patients presenting without initial neurologic deficits.

Adult↗

PubMed1993

Comparison of operative versus nonoperative treatment of lumbar burst fractures.

The outcomes of traumatic two- and three-column lumbar burst fracture patients treated operatively and nonoperatively were investigated with respect to treatment complications, resumption of employment, and quality of life. Data were obtained from hospital records, radiographs, and written questionnaires. Of 93 patients diagnosed with lumbar fracture between January 1987 and December 1989, 22 met the criteria for study (12 operative, ten nonoperative). Exclusion was based on single-column compression or chance fractures, neurologic compromise, and nontraumatic fractures. The patient groups had distinctly different fracture patterns based on degree of anterior column compression (ACC). Trends toward significant differences in kyphotic angulation and canal compromise were noted. There were no preoperative complications. Varying modes of external immobilization were used in both groups. One patient in each group used narcotic medications for pain at final follow-up evaluation. When comparing the operatively and nonoperatively treated lumbar burst fracture patients in this study group, no significant difference in treatment outcome was established. Nonoperative treatment remains a viable alternative to operative intervention in selected lumbar burst fracture patterns.

Adult↗

PubMed1993

Influence of pedicle fixation on postoperative pain.

From October 1988 through November 1990, 29 lumbar and lumbosacral spine fusion patients, 11 instrumented and 18 noninstrumented, were observed. Seventeen were men and 12 were women, with a mean age of 42.6 years (range, 22-83). The narcotic equivalent (NE) in milligrams/kilogram/day of medication used was analyzed. Age, sex, height, and weight were compared to the type, dose, mode, and duration of medication administration. Morphine was the reference point narcotic at 1.0:1.0. Levels fused, use of instrumentation, and prior surgery were related to NE. No significant differences in age, total body weight, height, levels fused, or hospital stay were established. There were 89.6% of patients over the ideal body weight by a mean 17.47 kg or 38.3 lb. The mean population NE was 3.76 mg/kg/day. Prior surgery patients tended to request narcotics intramuscularly for a longer period, while older patients tended to receive less medication. Patient obesity was related to lower NE. This study could not demonstrate a decrease in postoperative pain as it relates to the amount of narcotic medication received with the use of pedicle instrumentation.

Adult↗

PubMed1992

Renal-specific actions of angiotensin II receptor antagonism in the anesthetized dog.

The role of angiotensin II (AII) in the regulation of systemic hemodynamic and renal function and sodium excretion, although important in states characterized by the activation of the renin-angiotensin system, remains unclear under basal conditions. The current studies were designed to define the role of AII in the basal regulation of cardiovascular and renal function using a specific AII receptor antagonist, DuP 753, in the normal anesthetized dog. No changes in mean arterial pressure, cardiac output, or systemic vascular resistance were observed during the infusion of DuP 753. In contrast, a significant increase in glomerular filtration rate (19.7 +/- 0.9 to 26.1 +/- 2.0 mL/min) and renal blood flow (151 +/- 20 to 188 +/- 26 mL/min), with a decrease in renal vascular resistance (0.85 +/- 0.10 to 0.66 +/- 0.06 mm Hg/mL/min) was observed. Associated with the renal hemodynamic changes, a diuretic (0.16 +/- 0.05 to 0.57 +/- 0.21 mL/min) and natriuretic (31.2 +/- 7.0 to 100.5 +/- 22.2 microEq/min) response was also demonstrated. Renal hemodynamic changes were also associated with a decrease in tubular sodium reabsorption characterized by an increase in the fractional excretion of sodium (1.10 +/- 0.3 to 2.61 +/- 0.62%), with an associated decrease in whole-kidney proximal tubular reabsorption indicated by an increase in fractional excretion of lithium (31.2 +/- 2.2 to 40.8 +/- 3.9%). In addition, a kaliuretic (17.9 +/- 2.1 to 27.1 +/- 2.4 microEq/min) response was observed despite a concurrent decrease in plasma aldosterone (10.8 +/- 1.5 to 8.1 +/- 1.0 ng/dL).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗