Biomedical subjects

Vincent K H Tam

Publications and source records attributed to Vincent K H Tam.

7 recordsLinked to original sources

PubMed2006

Anomalous coronary artery with aortic origin and course between the great arteries: improved diagnosis, anatomic findings, and surgical treatment.

BACKGROUND: Anomalous origin of a coronary artery with subsequent coursing between the great vessels is a rare congenital heart defect that may cause myocardial ischemia and sudden death. Because of the fatality rate of this anomaly, many are diagnosed at the postmortem examination, and reports of surgical correction are few. We present our experience with the diagnosis and surgical treatment of this rare coronary anomaly. METHODS: Between June 2003 and August 2005, 9 patients (8 males) were diagnosed with anomalous origin of a coronary artery coursing between the great vessels. The mean age was 12 +/- 5.8 years (range, 4 months to 23 years). Three patients had an intramural origin of the coronary artery. One infant had a single coronary artery and was diagnosed during follow-up of other heart defects. The 8 older patients all presented with exertional syncope or chest pain and echocardiography was used for the initial diagnosis. Six patients had coronary artery reimplantation in the correct aortic sinus, 2 patients had unroofing of the intramural coronary segment, and 1 patient had pericardial patch enlargement of his right coronary artery before reimplantation. One patient, the infant, awaits repair at an older age. RESULTS: No postoperative deaths occurred. The mean hospital stay was 5.5 +/- 1.2 days (range, 4 to 8 days). Three patients had transient ST segment changes during the first 24 hours postoperatively. Follow-up was 4 months to 2.5 years. All patients underwent an exercise myocardial perfusion scan 3 months postoperatively without evidence of myocardial ischemia, and all patients remain clinically well. CONCLUSIONS: Echocardiography imaging of young patients with exertional syncope or chest pain is reliable for the diagnosis of this coronary anomaly. It is surgically correctable; however, individual coronary anatomy may cause the surgical approach to vary. The postoperative outcome is excellent.

Abnormalities, Multiple↗

PubMed2006

Repeat right ventricular outflow tract reconstruction using the Medtronic Freestyle porcine aortic root.

BACKGROUND AND AIM OF THE STUDY: A variety of valve substitutes are used for right ventricular outflow tract (RVOT) reconstruction in children and young adults after previous RVOT surgery that has led to significant pulmonary insufficiency and/or stenosis. Herein, the authors' experience with pulmonary valve replacement (PVR) using a porcine valved conduit late after previous RVOT surgery was reviewed. METHODS: Between August 2002 and April 2005, 31 patients (mean age 14.5 +/- 9.5 years; range: 1.2-33.1 years) underwent PVR using the Medtronic Freestyle porcine aortic root. These patients averaged two prior operations (range: 1-5) for the following diagnoses: tetralogy of Fallot +/- pulmonary atresia (n = 21); persistent truncus arteriosus (n = 5); aortic stenosis (Ross-Konno procedure) (n = 2); pulmonary atresia with intact ventricular septum; (n = 1); congenital pulmonary stenosis (n = 1); and transposition of the great arteries (n = 1). Of these patients, 29 (93.5%) underwent additional procedures at the time of pulmonary valve insertion including: branch pulmonary artery reconstruction (n = 21), atrial septal defect closure (n = 5), ascending aorta replacement (n = 4), pacemaker or defibrillator placement (n = 3), tricuspid valve repair (n = 2), ventricular septal defect closure (n = 2), and other procedures (n = 2). RESULTS: There were no early or late deaths. The mean hospital stay was 8.3 +/- 5.9 days (range: 4-25 days). One patient had a subarachnoid hemorrhage with transient left hemiparesis, and two patients had acute tubular necrosis with temporary dialysis treatment. All patients were well at a mean follow up of 13 +/- 9.3 months (range: 0.5-31 months). Echocardiography showed trivial or no pulmonary insufficiency in 30 patients (96.7%). The calculated mean peak systolic RVOT gradient by echocardiography was 23.4 +/- 7.6 mmHg. CONCLUSION: The Medtronic Freestyle bioprostheses demonstrated excellent short-term results for repeat RVOT reconstruction. This valve's hemodynamic characteristics are comparable to those of homografts, and it is an attractive alternative given the limited availability of homograft valves. A lack of availability in sizes smaller than 19 mm limits use of this valve in pediatric patients, and long-term results remain to be determined.

Adolescent↗

PubMed2003

Early experience with a modified Norwood procedure using right ventricle to pulmonary artery conduit.

BACKGROUND: A recent modification to the Norwood procedure involves the use of a right-ventricle (RV) to pulmonary artery (PA) conduit to provide pulmonary blood flow for patients with hypoplastic left heart syndrome (HLHS). This modification is thought to provide more stable hemodynamics by avoiding the diastolic "run-off" that occurs with a Blalock-Taussig shunt. METHODS: We reviewed our experience with the first 11 patients undergoing the RV-PA conduit modification of the Norwood operation and compared their outcomes with those of the preceding 22 patients who underwent a conventional Norwood procedure. RESULTS: Between July 1999 and March 2002, 33 patients with HLHS underwent the Norwood procedure at a median age of 5 days (range 1 to 31 days). Aortic atresia was present in 28 (85%). No significant difference was noted between the RV-PA (n = 11) and conventional Norwood (n = 22) groups with respect to measures of morbidity such as duration of mechanical ventilation or hospital stay. Patients who underwent the conventional Norwood procedure did have significantly lower diastolic blood pressure in the early postoperative period (38.4 +/- 4.4 mm Hg versus 49.5 +/- 4.3 mm Hg, p = 0.001). The operative and 1-year survival rates were 81% and 81%, respectively, for patients with the RV-PA modification, which was not significantly different from those of patients who underwent the conventional procedure, 81% and 73% (p = 1.00 and p = 0.36). Two patients developed a pseudoaneurysm of the RV infundibulum after placement of RV-PA conduit. Four sudden deaths occurred after hospital discharge, all occurring in the conventional Norwood group. CONCLUSIONS: The RV-PA conduit modification of the Norwood procedure results in excellent early survival. By avoiding low diastolic blood pressure this modification may provide superior perfusion to the coronary vascular bed and potentially reduce the risk of sudden unexpected death.

Cardiac Surgical Procedures↗

PubMed2003

Deletion of chromosome 22q11.2 and outcome in patients with pulmonary atresia and ventricular septal defect.

BACKGROUND: The 22q11.2 deletion (del22q) is present in many patients with conotruncal abnormalities including pulmonary atresia with ventricular septal defect (PA/VSD). We sought to determine the impact of the del22q on outcome in subjects with PA/VSD. METHODS: We reviewed the experience for all patients with PA/VSD who were born between January 1993 and April 2002 and presented to our institution. Patients with conotruncal defects were routinely evaluated for genetic disorders including del22q. Fluorescence in situ hybridization was used to test for del22q. RESULTS: There were 67 subjects with PA/VSD who presented during that time period; testing for del22q was performed in 58 of 67 (87%) and these 58 patients comprised the study population. The 22q11.2 deletion was present in 20 of 58 (34%) patients tested. Major aortopulmonary collaterals were defined by angiography and were present in 27 (47%). These collaterals were significantly more common among subjects with del22q (13 of 20, 65%; p = 0.04). The median cross sectional area of the pulmonary arteries, the Nakata index, was significantly less for patients with del22q (41 versus 142 mm(2)/m(2); p = 0.006). There were 3 subjects, all of whom had del22q, who did not undergo surgery owing to markedly hypoplastic pulmonary arteries. Of the remaining 55 patients, 53 had arteriopulmonary shunt with or without unifocalization as the initial procedure and 35 patients have undergone complete repair. There were 8 operative deaths and 1 nonoperative death. The 5-year survival was 36% for patients with del22q versus 90% for patients without del22q. The 22q11.2 deletion was a significant risk factor for death, even after adjusting for the presence of major aortopulmonary collaterals (p = 0.004). There was no significant difference between the two groups with respect to the incidence of serious viral, bacterial, or fungal infections in the perioperative period. CONCLUSIONS: Patients with del22q and PA/VSD are at increased risk for death owing to a variety of factors including less favorable pulmonary artery anatomy. A better understanding of del22q, pulmonary artery anatomy, and outcome is required.

Abnormalities, Multiple↗

PubMed2003

Mitral valve replacement in children.

BACKGROUND AND AIMS OF THE STUDY: Although repair of the mitral valve in children with or without concomitant congenital heart defects has improved significantly, it is not always achievable. The study aim was to review a 20-year experience of mitral valve replacement (MVR) in children. METHODS: Since 1980, 90 patients (37 males, 53 females; mean age 8.1 years; range: 3 weeks to 18 years) have undergone a total of 102 MVR operations (12 redo-MVR, nine multiple valves, and three with common atrioventricular valve replacement). Tissue valves were used in 13 patients (14%). The etiology for valve disease was congenital in 72 patients (80%), and 34 patients had atrioventricular septal defect (AVSD). Other etiologies included rheumatic heart disease (n = 8), myxomatous disease (n = 4), endocarditis (n = 3), and Kawasaki disease, left atrial myxoma and idiopathic hypertropic subaortic stenosis (each n = 1). In total, 36 patients (40%) had a previous mitral valve repair, and 34 (38%) had concomitant repair of associated lesions. RESULTS: Hospital mortality was significantly higher in children aged < 2 years (52%, 15 of 29) compared with older children (3%, 2 of 61) (p < 0.001). Fourteen hospital deaths were associated with failed repair of complex congenital heart defects, mainly AVSD under age 2 years, followed by MVR. Mean follow up was 9.3 years (range: 7 months to 21.5 years). There were four late deaths; major events included thromboemboli (n = 6), bleeding (n = 9), endocarditis (n = 1) and cardiomyopathy with orthotopic heart transplantation (n = 7). CONCLUSION: MVR is a good surgical option for a nonrepairable mitral valve in children aged over 2 years. MVR following failed AVSD repair carries a high incidence of morbidity and mortality.

Adolescent↗

PubMed2002

One hundred pulmonary valve replacements in children after relief of right ventricular outflow tract obstruction.

BACKGROUND: Surgical repair of obstructive lesions of the right ventricular outflow tract (RVOT) in children commonly creates pulmonary valve incompetence that may eventually require pulmonary valve replacement (PVR). We reviewed our experience with PVR late after RVOT reconstruction. METHODS: We performed 100 PVRs in 93 children 1.1 months to 22.4 years (median 8) after RVOT reconstruction. Children with right ventricular to pulmonary artery conduits and primary PVRs were excluded. Age at PVR was 4.5 months to 27.9 years (median 9.5 years). Initial diagnosis was tetralogy of Fallot and variants, 62; critical pulmonary stenosis, 15; pulmonary atresia with intact ventricular septum, 7; and others, 9. Eleven patients had a redo PVR. A total of 62 PVRs were homografts; 38 were porcine valves. RESULTS: There was one early death. On follow-up of 5 months to 12.4 years (mean 4.9 years) there were no late deaths although 1 child underwent cardiac transplantation. Actuarial freedom from redo PVR at 8 years was 100% for porcine valves but 70% for homograft valves (p = 0.17). For children younger than 3 years at PVR, freedom from reoperation was 76% at 1 year and 39% at 8 years compared with freedom from redo PVR at 8 years of 100% for children older than 3 years. On latest echocardiogram 97% of porcine valves had mild or no pulmonary regurgitation compared with 72% of homograft valves. CONCLUSIONS: PVR after RVOT reconstruction can be performed with low risk. Porcine valves may be superior to homograft valves although this advantage may be due to older age at time of PVR.

Adolescent↗

PubMed2002

Konno aortoventriculoplasty in children and adolescents: from prosthetic valves to the Ross operation.

BACKGROUND: In children with complex multilevel left ventricular outflow tract obstruction (LVOTO), the Konno aortoventriculoplasty is used to enlarge the aortic root and increase the size of the aortic valve implanted. We present our experience with the evolution of this surgical approach from prosthetic valves to the Ross operation. METHODS: Between March 1982 and July 2000, 60 patients (36 males and 24 females) had 72 Konno aortoventriculoplasties (prosthetic valve and Konno group [57 patients; redo, 12] and Ross-Konno group [15 patients]). The patients' ages ranged from 5 days to 18 years (mean, 8.2 years). The underlying anatomic diagnoses were congenital aortic stenosis and LVOTO in 51 patients, coarctation of the aorta with bicuspid aortic valve in 13, severe aortic insufficiency associated with a ventricular septal defect in 8, interrupted aortic arch in 6, mitral stenosis in 6, atrioventricular septal defect in 5, and endocarditis in 3. There was no statistical difference in age or diagnosis between the two groups. The prosthetic valve group included 42 mechanical valves, 9 homografts, and 6 xenografts. RESULTS: Follow-up ranged from 10 months to 18.5 years (mean, 9.7 years) in the prosthetic valve and Konno group compared with 5 months to 3.7 years (mean, 2.1 years) in the Ross-Konno group (p < 0.05). There were 10 early deaths and four late deaths in the prosthetic valve and Konno group as compared with one early death and two late deaths in the Ross-Konno group (p = not significant). Reoperations for LVOTO and aortic valve replacement were significantly higher in the prosthetic valve and Konno group as opposed to the Ross-Konno group (16 vs 0, p < 0.05) mainly because of the biological valve and Konno subgroup. There were no statistical differences in reexploration for bleeding, pacemaker insertion, and reoperations for indications other than LVOTO and aortic valve replacement between the two groups. CONCLUSIONS: The Konno aortoventriculoplasty is a good surgical option for complex LVOTO. Patients with a prosthetic valve and Konno carry a high rate of reoperation. Early operative results with the Ross-Konno operation seem promising.

Adolescent↗