Prevalence of Hyperhomocyseinemia in Patients requiring Coronary Artery Bypass
O Stanger, T Lang, L Salaymeh, H Rabl, B Rigler
Keywords
aneurysm, aorta, bypass surgery, cardiac, cardio-pulmonary, cardiopulmonary bypass, cardiothoracic, carotid, chest, heart, heart-lung machine, medicine, surgery, thoracic, valve, vascular, vessel
Citation
O Stanger, T Lang, L Salaymeh, H Rabl, B Rigler. Prevalence of Hyperhomocyseinemia in Patients requiring Coronary Artery Bypass. The Internet Journal of Thoracic and Cardiovascular Surgery. 1996 Volume 2 Number 1.
Abstract
Purpose
Hyperhomocysteinemia has been suggested as an independent risk factor for premature atherosclerosis 1,2 and is associated with an elevated risk for thromboembolic events 3 and a higher mortality ratio in patients with Coronary Artery
Disease (CAD) 4.
Biochemistry
Homocysteine is a sulfur-containing amino acid formed during the metabolism of methionine
(itself being an essential protein and consumed with food,-mainly meat and cheese products). Two
major pathways regulate the metabolism of homocysteine:
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Remethylation of homocysteine to methionine is catalysed by methionine-synthase and requires folic acid and vitamin B12 as essential co-factors.
-
Transsulfuration of homocysteine to cystathione (and cysteine) is catalysed by the vitamin B6-dependent enzyme cystathionine-ß-synthase. Deficits of the vitamins mentioned are associated with elevated homocysteine levels in plasma and may increase the risk of atherosclerosis and thromboembolic events.
5
Methods
85 male patients (mean age 49.2 ± 5.1years) with angiographically confirmed Coronary Artery
Disease (CAD) were included in this study. Inclusion and exclusion criterias have been described
earlier elsewhere3. All patients were expecting Coronary Artey Bypass Grafting (CABG) within
one week at the time of investigation. Total plasma homocysteine (tHcy) concentrations were
assessed in a fasting state and 6 hours after administration of an oral methionine-loading-test (0.1 g
methionine / kg / body weight), using HPLC with fluoresence detection. Increase of fasting and
post-load tHcy-levels were related to vitamin B12- and folate concentrations.
Results
In this study population, a total of 32 patients (37%) had pathological homocysteine values.
Fasting hyperhomocysteinemia (tHcy > 15m mol/l) was detected in 19 patients, with a
mean value of 19.98 (15.36-22.99). The oral methionine-loading-test identified additional 13
patients (+40%) with a mean value of 53.13 (40.01-79.75). These patients had normal fasting levels
and required the methionine-loading-test for positive identification. The increase of tHcy (fasting /
post-load) showed an inverse correlation with plasma folate concentrations, but not with plasma
vitamin B12 levels.
Conclusions
Prevalence of hyperhomocysteinemia is high,- 37% in this study group (compared to 5-7%, that can be expected in the general population 6,7). The methionine-loading-test identified 40% of the patients with pathological tHcy values, and is therefore a useful tool in searching for hyperhomocysteinemia. High post-load increase of homocysteine is associated with low folate concentrations, not with vitamin B12 levels. Available prospective studies (max. follow-up 5 years) document the inverse relation-ship between tHcy- levels and clinical outcome in CAD-patients 4,6. However, whether the easy and effective tHcy- lowering therapy through vitamin supplementation can slow the progression of CAD requires further investigation and long-term prospective studies.
