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Biomedical subjects

C K Mok

Publications and source records attributed to C K Mok.

At least 19 recordsLinked to original sources
PubMed1996

Intraoperative TEE assessment of ventricular septal defect with aortic regurgitation.

BACKGROUND: It is desirable to repair but not replace the aortic valve in patients with ventricular septal defect and acquired aortic regurgitation. Precise definition of the valvar pathology with monitoring of its repair perioperatively would enhance the surgical management of this condition. METHODS: Fourteen consecutive patients (age, 10.6 +/- 6 years; weight 29.7 +/- 5.7 kg) who underwent repair of ventricular septal defect with aortic regurgitation were studied by intraoperative transesophageal echocardiography. The severity of prolapse of each of the individual aortic cusps and its adjacent sinus was assessed and the valvar regurgitation quantified by Doppler-derived regurgitant indices. The echocardiographic and surgical findings were correlated and the preoperative and postoperative echocardiographic data were compared to assess the effectiveness of operation. RESULTS: Eight subarterial and six perimembranous defects were located accurately and their sizes (11.8 +/- 3.0 mm) correlated well (r = 0.80) with the surgical measurements. Transesophageal echocardiography detected prolapse of the aortic valve and its sinus in all 14 patients. The severity of the prolapse was severe in 10, moderate in 4, and mild in 5 leaflets. One the basis of these findings, together with the Doppler-derived mean regurgitant indices, exploration of the valve and valvuloplasty were executed appropriately in 12 of 14 patients. In all 14 patients, transesophageal echocardiography after bypass revealed no further cuspal prolapse and significant reduction of the mean regurgitant index (0.55 +/- 0.23 to 0.17 +/- 0.15, p < 0.0001). Residual ventricular septal defect was detected in 5 patients and the only patient with significant shunting who required reexploration was identified correctly. CONCLUSIONS: Intraoperative transesophageal echocardiography can assess effectively the surgical repair of ventricular septal defect with aortic regurgitation and provide information that directs and alters surgical plans to the benefit of patients.

Adolescent↗
PubMed1996

Surgical resection of pulmonary metastases from nasopharyngeal carcinoma.

BACKGROUND: Nasopharyngeal carcinoma (NPC), unlike other head and neck cancers,is known for its propensity for distant metastases. Chemotherapy remains the mainstay of treatment because of this and the chemosensitivity of the tumour, but long-term control is rare. The surgical management of pulmonary metastases of other extrathoracic malignancies prompted this review of surgical management of patients with NPC. METHODS: Thirteen thoracotomies were performed in 12 patients with pulmonary metastases as the first and only site of relapse of nasopharyngeal carcinoma. Postoperative chemotherapy was given in four patients, radiotherapy to the mediastinum in one patient and both chemotherapy and radiotherapy in two patients. The survival pattern of this group of 12 patients was compared with a historical control group consisting of 65 patients without surgical resection. RESULTS: Lymph node involvement was documented in four patients during operation. Four patients relapsed after surgical resection, two of them were from the group of three patients with lymph node involvement. The site of subsequent relapse was the lung for three patients and the skeletal system for the fourth. The 2 year actuarial survival of the surgically resected group compared favourably with the historical control group (80% and 24.1%, respectively; P=0.0002 by Mantel-Cox text). CONCLUSIONS: Surgical resection of pulmonary metastases from NPC seems to be a promising approach thought the effect of case selection cannot be excluded and further studies are indicated. The importance of exploration and dissection of mediastinal nodes in the surgical management of pulmonary metastases from NPC was demonstrated.

Actuarial Analysis↗
PubMed1995

Surgical repair of coarctation of the aorta in neonates: factors affecting early mortality and re-coarctation.

Between October 1979 and January 1993, 85 Chinese neonates in Hong Kong underwent surgical repair for coarctation of the aorta. Their mean (s.e.) age and body weight at operation was 15.6(8.5) days and 3.06(0.56) kg, respectively. Simple coarctation was present in 17 babies, while 36 had additional ventricular septal defect and 31 had associated major complex intracardiac lesions. Subclavian flap aortoplasty was performed in 56 babies, resection with end-to-end anastomosis in 18 and aortoplasty with the use of a GORETEX patch in 11. The overall early mortality rate was 16.5%. To identify risk factors for early operative mortality, various clinical variables, surgical options, associated heart lesions and dimensions of the aortic arch at different sites for each patient were reviewed. Univariate analysis identified statistically significant differences between the survivors and non-survivors for the following factors: preoperative body-weight, arterial pH and base excess, serum urea and creatinine levels. Stepwise logistic regression further distinguished serum creatinine levels and the period of operation as two significant risk factors. Contrary to previous reports, the dimensions of the aortic arch and type of surgery did not affect early operative mortality. Among the 71 hospital survivors followed for 38.2(38) months, residual or recurrent coarctation of the aorta was detected in 12(17%). The different surgical operations were not related to the incidence of late complication. The size of the distal transverse arch, however, was different (P=0.05) in those who did and did not develop aortic sequela. Successful balloon angioplasty was subsequently performed in 11 patients. In an era of echocardiography with prenatal diagnosis and therapeutic catheterization, early recognition of the disease with prompt prostaglandin infusion should prevent collapse of the baby, thus avoiding renal impairment and sever metabolic acidosis. Balloon angioplasty would offer a simple effective treatment of patients who developed aortic re-coarctation.

Aortic Coarctation↗
PubMed1993

Management evolution of pulmonary atresia and intact ventricular septum.

To examine the impact on survival and clinical course of incorporating the morphologic classification of the right ventricle into the evolving management strategy for babies with pulmonary atresia and intact ventricular septum, the surgical results and follow-up status of the first 62 consecutive patients managed in this hospital between 1979 and 1990 were reviewed. Before 1984, all 23 babies from group I underwent primary right ventricular outflow reconstruction irrespective of right ventricular morphology and size. Since 1984, depending on the morphology and size of the right ventricle, 39 babies from group II had either closed transventricular pulmonary valvotomy (n = 31) or a shunt operation (n = 8). There were 10 hospital (43%) and 2 late deaths (total mortality 52%) in our group I patients. Three of the 11 long-term survivors had cyanosis at rest but none had any residual pressure gradient across the pulmonary outflow. Group II had 6 hospital (15%) and 4 late deaths (total mortality = 26%). Of the 29 long-term survivors, 9 had a second-stage right ventricular outflow reconstruction, 8 had balloon valvuloplasty and 2 had successful Fontan operation. At the latest follow-up, 5 children from this group have cyanosis at rest, 1 has a residual gradient (55 mm Hg) across the infundibulum, and 3 have right ventricular dysfunction. The hospital and total mortality for babies in group II was significantly lower than that in group I (p < 0.01). These data suggest that tailoring the treatment to the right ventricular anatomy results in a lower overall mortality although long term postoperative hemodynamic abnormalities are observed in both groups.

Abnormalities, Multiple↗
PubMed1993

Paediatric thymoma: unusual occurrence in two siblings.

Invasive cystic thymoma is reported in two siblings (an 11-year-old girl and a 9-year-old boy) and the radiographic, CT and ultrasonographic features are described. The tumours were removed by thoracotomy. Familial thymic masses are reviewed, and the imaging differential diagnosis of cystic anterior mediastinal mass in a child is discussed.

Child↗
PubMed1992

Modified Fontan procedure for severe Ebstein's malformation with predominant tricuspid stenosis.

Two children, aged 7 and 6 years, had severe Ebstein's malformation of the tricuspid valve and underwent operation because of progressive cyanosis (saturation, 70%). Preoperative angiography demonstrated linear attachment of the distal edges of the displaced anterosuperior and mural leaflets, leaving only a "keyhole" communication between the atrialized and functional portions of the right ventricle. Operation was directed toward completely excising these dysplastic leaflets, which were obstructing the flow of blood. The continuity between the functional right ventricle and pulmonary trunk was left intact. In addition, an atriopulmonary truncal connection was established. Postoperatively, both children were in functional class I with arterial saturation of 95%. Angiography and Doppler echocardiography demonstrated that there was a dominant phase of systolic flow of blood up the pulmonary trunk from the right ventricle, and also diastolic filling of the pulmonary arteries through the atriopulmonary truncal connection. The filling patterns did not change over time for the follow-up period of 4 and 1.5 years, respectively. This modified Fontan procedure appears to be an effective surgical alternative for some patients with severe Ebstein's malformation and predominant tricuspid stenosis.

Child↗
PubMed1992

Balloon valvuloplasty after pulmonary valvotomy for babies with pulmonary atresia and intact ventricular septum.

During a 2 1/2-year period, staged procedures of transventricular closed pulmonary valvotomy followed by balloon valvuloplasty were attempted in 12 babies with pulmonary atresia and an intact ventricular septum. All babies immediately underwent valvotomy when echocardiography revealed a tripartite right ventricle with adequate inflow and outflow dimensions and without sinusoidal-coronary arterial fistulas. After valvotomy, the overall mortality rate was 25% (3/12), but the only surgical death (1/12, 8%) was due to failure to establish continuity between the right ventricular cavity and the pulmonary trunk. The other 2 babies died of neonatal complications after successful valvotomy. Angiocardiography performed 5 to 18 months after valvotomy documented substantial growth of the right ventricular inflow and outflow dimensions in the 9 survivors. Twelve balloon dilation procedures were then performed in 7 babies. All except 1 achieved a significant drop in the right ventricular to left ventricular peak systolic pressure ratio (0.96 +/- 0.40 to 0.56 +/- 0.28; p less than 0.01). Balloon valvuloplasty was not required in 1 baby and failed in the other, who then underwent successful right ventricular outflow tract reconstruction. After these staged procedures, follow-up at 1 month to 20 months (mean follow-up, 14.8 months) revealed resting cyanosis in 3 babies, which was related to severe residual infundibular stenosis (55 mm Hg) in 1 and a subnormal tricuspid valve annulus in 2. The remaining 5 babies (including 1 who required no valvuloplasty) were active and pink (saturation greater than 97%) and had a mean Doppler estimated gradient of 19 mm Hg (range, 8 to 36 mm Hg) across the pulmonary valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1990

Ascending aortic dissection complicating syphilitic aortitis, late after aortic valve replacement.

A 54-year-old man underwent aortic valve replacement for syphilitic aortic regurgitation. Eight years later, he was admitted with sudden precordial discomfort and symptoms of superior vena caval obstruction. Ascending aortic dissection was diagnosed by echocardiography and computed tomography of the thorax. The patient succumbed rapidly after admission. Postmortem findings and histological features were compatible with syphilitic aortitis, without significant atherosclerosis. This case report adds to the sparse literature on aortic dissection complicating syphilitic aortitis, and illustrates that, at certain stages of the disease process, syphilitic aortitis can lead to such a degree of mechanical instability of the aortic wall as to predispose to dissection.

Aortic Rupture↗
PubMed1990

An unusual cause of disabling angina following aortic valve replacement.

Severe ostial stenosis of the coronary arteries following aortic valve replacement is a potentially lethal complication. The usual presentations are recent onset of severe angina, ventricular arrhythmias, congestive heart failure, and sudden death. It is generally accepted to arise from injury to the coronary arteries during direct cannulation and continuous perfusion of cardioplegia under high pressure during operation. We report on a patient who developed critical left coronary ostial stenosis after aortic valve replacement. The cause for the stenosis was probably related to the over-sizing and orientation of the prosthesis. The prosthesis was replaced and patch angioplasty of the left coronary ostia performed. The patient was well with normal coronary anatomy three years after surgery.

Adult↗
PubMed1989

Experience with the management of primary endodermal sinus tumor of the mediastinum.

Ten male patients with extensive primary endodermal sinus tumor of the mediastinum were treated with chemotherapy (with or without surgical excision and radiation therapy) between 1977 and 1985. Three patients, treated with cyclophosphamide-vincristine-based chemotherapy, died 1.5, 2.5, and 6.0 months, respectively, after initial diagnosis. Of the seven patients treated with cisplatin-based chemotherapy, one patient died of septicemia at 2.5 months after diagnosis and was disease-free at autopsy examination. Three other patients died of progressive disease at 7.0, 13.0, and 14.0 months, respectively. The three survivors remain alive at 17.0, 31.0, and 40.0 months from diagnosis; all are without evidence of disease. Of the three patients who underwent excision of the residual mediastinal tumor after cisplatin-based chemotherapy, persistent local disease was found in two patients. One of these two patients died of recurrent disease. All surviving patients had surgical resection of the tumor either before or after cisplatin-based chemotherapy, with or without radiotherapy and the timing of therapeutic interventions was guided by changes in the serum alpha-fetoprotein concentrations after initial therapy and during follow-up. Our experience suggests that the optimal management of patients with primary mediastinal endodermal sinus tumor requires an aggressive multidisciplinary approach guided by the extent of the tumor and the serum tumor marker levels.

Adolescent↗
PubMed1989

Left subclavian arterioesophageal fistula induced by a foreign body.

A left subclavian arterioesophageal fistula was diagnosed in a 35-year-old man at exploratory thoracotomy for suspected aortoesophageal fistula. After successful closure of the arterial fistula the patient developed a mediastinal abscess and esophagopleural fistula. The latter was successfully managed by retrosternal jejunal esophagoplasty followed by excision of the thoracic esophagus. This report documents a case of left subclavian arterioesophageal fistula and illustrates the importance of early diagnosis and surgical intervention of arterial perforation secondary to a foreign body in the esophagus.

Abscess↗
PubMed1989

Biventricular perforation by a temporary pacing electrode: recognition from the lateral chest radiograph.

A temporary pacing electrode was inserted in a patient with severe calcific aortic stenosis complicated by complete atrioventricular block. Despite normal pacing and sensing function, a diagnosis of myocardial perforation was made on the basis of a lateral chest radiograph. Neither the surface electrocardiogram nor the frontal chest radiograph suggested evidence of myocardial perforation, and echocardiographic diagnosis was limited by poor echogenicity of the patient. Biventricular perforation with pericardial effusion were documented at operation.

Cardiac Pacing, Artificial↗
PubMed1989

The management of symptomatic neonates with suspected congenital heart disease using combined cross-sectional echocardiography and pulsed Doppler flow study as the definitive investigations.

We studied prospectively 140 consecutive symptomatic neonates with suspected congenital heart disease by combined cross-sectional and pulsed Doppler echocardiography. Using the sequential segmental approach, the anatomy at all cardiovascular junctions was clearly defined in 89 (64%) babies. Based on the non-invasive investigations, 47 went to surgery while 42 babies were treated medically. The other 51 babies underwent further cardiac catheterisation. Of these, only 23 (16%) required diagnostic catheterisation prior to their management decision. The remaining 28 babies were catheterised for (1) angiographic measurement of anatomical structures (n = 12), (2) haemodynamic measurement (n = 1), and (3) balloon atrial septostomy (n = 15). One hundred and two babies had ultimate verification of their echocardiographic diagnoses. A total of 612 cardiovascular segments were identified. There were 33 (5%) echocardiographic errors, 23 of missed or uncertain diagnosis and 10 wrong interpretations. The diagnostic sensitivity and specificity for the combined non-invasive technique were thus 96 and 98%, respectively. Only one death was attributed directly to an echocardiographic error. Hence when the clinical outcome was taken into consideration, 88 of the 89 neonates without an initial catheterisation were judged to be appropriately managed for their presentation.

Echocardiography↗
PubMed1989

Left ventricular pseudoaneurysm after replacement of the mitral valve: long-term survival and spontaneous closure.

Left ventricular pseudoaneurysms, with or without overt ventricular rupture, are usually fatal in the absence of prompt surgical intervention. This report details the long-term survival of a patient who developed a left ventricular pseudoaneurysm following repair of ventricular rupture subsequent to replacement of the mitral valve, with spontaneous closure of the "neck" of the pseudoaneurysm.

Aged↗