Coronary Artery Bypass Grafting in a Child with Familial Hypercholesterolemia

INTRODUCTION

This report describes our experience with successful triple bypass grafting in a 7-year-old child with 3-vessel coronary artery disease and supravalvular aortic stenosis, due to homozygous familial hypercholesterolemia.

CASE REPORT

History and Physical

A 7-year-old girl presented for coronary artery bypass grafting with 3-vessel disease. At age 6-8 months the patient presented with masses on the buttocks and heal, which her physician related to diet. Masses continued to develop and became painful two months prior to admission, leading to biopsy and the diagnosis of lipoma. The patient’s cholesterol level was checked and found to be greater than 900 mg/dL, at which time she was diagnosed with homozygous familial hypercholesterolemia. The patient had occasional brief, non-exertional chest pain and shortness of breath with exercise. Otherwise, she had no limitations in her daily activities. The patient was started on Lipitor 5-10mg qd and ASA 40.5 mg qd.

Cardiac catheterization revealed: supravalvular aortic stenosis; mild to moderate aortic insufficiency; and coronary artery disease with 20% proximal and 35-50% left main narrowing, diffuse 20-40% narrowing of LAD, diffuse proximal narrowing of the circumflex, 60-70% narrowing of large mid obtuse marginal, and a large normal diagonal. There was a dominant right coronary artery with 60% proximal narrowing, 35-50% mid RCA narrowing, and 95% distal narrowing, with collateral filling of diffusely diseased distal RCA.

Family history consisted of a great, great uncle who had a MI at age 29, and mother with increased cholesterol. Father’s history is unknown.

Surgical Procedure

At operation, the right and left internal mammary arteries were harvested and anastamosed to the circumflex and to the LAD respectively. The right radial artery was harvested and anastamosed to the distal RCA. The non-coronary sinus and ascending aorta were enlarged with pericardial patch placement.

Regarding cardiopulmonary bypass (CPB), the patient was heparinized with 400 u/kg of beef lung heparin and ACT’s were maintained within normal range for bypass. The patient’s BSA was 1.07 m2 with a full flow of 2.35 L/min. The patient was cooled to 28 degrees C, using nasopharyngeal temperature monitoring. Following placement of an aortic cross-clamp, the heart was arrested with cold high potassium 4:1 blood cardioplegia given antegrade and retrograde. The maintenance doses of retrograde low potassium 4:1 blood cardioplegia were given every 10-15 minutes. Prior to the aortic cross-clamp removal, warm retrograde low potassium 4:1 blood cardioplegia was given. Crystalloid prime was used along with a hemoconcentrator. 700 ml of ultrafiltrate were removed resulting in a circulating hematocrit of 19%. Total aortic cross-clamp and bypass times were 87 and 116 minutes respectively. Postoperatively, the patient did well and was discharged on post-op day five on a low-cholesterol and low-fat diet.

DISCUSSION AND CONCLUSION

Symptomatic coronary artery disease develops in children with homozygous familial hypercholesterolemia, but fortunately, only one child in half a million is affected (1). In persons with the more frequent heterozygous form and in those with less clearly defined genetic forms of hypercholesterolemia, clinical disease can emerge by the fourth or fifth decade of life (1). Familial hypercholesterolemia is caused by mutations in low-density lipoprotein (LDL)-receptor gene that result in impaired clearance of plasma LDL and increased risk of coronary heart disease (2). Some patients are responsive to treatment with medications such as Lovastin and Lipitor, or LDL apheresis. During treatment with LDL apheresis (Liposorber system), the mean acute percentage reduction is 52.6% for total cholesterol and 63.1% for LDL-C (3). In some rare cases, as with our patient, unresponsiveness to medical treatment leads to the need for early myocardial revascularization or even the need for a heart/liver transplant.

Although the presentation of a coronary artery bypass grafting procedure in a young child is a rare occurrence for a perfusionist, the considerations such as hemodilution, cannula size, oxygenator size, and myocardial protection remain similar to other cases involving CPB.

REFERENCES

1. Stary HC. Evolution and progression of atherosclerotic lesions in coronary arteries in children and young adults. Arteriosclerosis 1989:Vol 9, No 1, 19-32.

2. Bourbon M, Fowler AM, Sun XM, Soutar AK. Inheritance of two different alleles of the low-density lipoprotein (LDL)-receptor gene carrying the recurrent Pro664Leu mutation in a patient with homozygous familial hypercholesterolemia. Clin Genet 1999, Sept;56(3):225-31.

3. Bambauer R, Schneidewind JM, Latza R. Apheresis technologies for prevention and regression of atherosclerosis: clinical results. ASAIO J 1999, Sep-Oct;45(5):403-7.

4. Lambert M, Lupien PJ, Gagne C. Treatment of familial hypercholesterolemia in children and adolescents: effects of Lovastatin. American Academy of Pediatrics 1996; Vol 97(5):619-628.

5. Sandiforn FM, Vargo TA, Joung-Yi Shih. Successful triple coronary artery bypass in a child with multiple coronary aneurysms due to Kawasaki’s disease. J Thorac Cardiovasc Surg 1980; 79:283-287.