Clinical Briefs

By Louis Kuritzky, MD

Homocysteine- Lowering Therapy with Folic Acid, Vitamin B12, and Vitamin B6 and Clinical Outcome after Percutaneous Coronary Intervention

Homocysteine (HCST) has recently obtained substantial attention as a modifiable cardiovascular risk factor. Elevated levels of HCST have been associated with adverse cardiovascular outcome in a linear fashion, similar to cholesterol. It is suggested that elevations of HCST alter patterns of vascular smooth muscle cell growth and migration, endothelial function, lipoproteins, and coagulability. Hence, modification of HCST might favorably affect outcomes in high-risk CAD patients, such as those undergoing coronary angioplasty.

Schnyder and associates studied patients who underwent PCTA on at least 1 vessel for underlying stenosis > 50%, evaluating the effect of treatments known to reduce HCST: a combination of folic acid, vitamin B12, and vitamin B6. After PCTA, subjects were randomly assigned to the supplements or placebo, administered for 6 months. The primary study outcome was a composite of death, MI, and need for repeat revascularization for as long as 6 months after administration of the supplements.

At baseline, no patients had severe elevations of HCST, but mild-moderate increases were found in 29% of subjects. HCST-lowering therapy was associated with a risk reduction of 32% in the composite end point, mostly due to a 38% relative reduction in need for revascularization. This inexpensive multiple vitamin intervention holds promise in reducing cardiovascular risk among persons undergoing PCTA. 

Schnyder G, et al. JAMA. 2002;288: 973-979.

Effect of Cataract Surgery on Motor Vehicle Accidents in Older Adults

Older adults suffer visual impairment due to cataract (CAT) more often than any other single cause. More than half of adults older than age 65 have cataract, which is slightly more frequent in African Americans. Retrospective reviews have shown that among older drivers, presence of CAT was associated with an increased frequency of a recent motor vehicle accident (MVA) when compared with persons free of CAT.

The per capita MVA rate in older licensed drivers (40/1000) is substantially less than in persons younger than 25 (140/1000), but this is largely a result of the many fewer miles driven by older persons than younger. Hence, the per-mile driven rate of MVA among older drivers is actually comparable to that of the highest risk younger drivers. Whether correction of CAT results in improvements of MVA risk was the subject of this report.

Owsley et al prospectively compared patients (n = 277) with CAT who underwent intraocular lens implantation after CAT excision to untreated CAT patients, followed 4-6 years. During follow-up, the MVA rate/million miles traveled in the surgically treated group was less than half that seen in the untreated group. Though the trial was not randomized, the data are highly supportive of the potential favorable effect of CAT surgery on highway safety. 

Owsley C, et al. JAMA. 2002;288:841-849.

Inflammatory Biomarkers, Hormone Replacement Therapy, and Incident Coronary Heart Disease

The role of hormone replacement therapy (HRT) in menopausal women is an area of current controversy, primarily due to the discordance between observational data that suggested cardiovascular benefits associated with HRT, and recently completed interventional trials that have shown increases in venous and arterial thrombotic end points early after HRT initiation. Among the possible mechanisms for deleterious effects of HRT upon cardiovascular risk, changes in C-reactive protein (CRP) and interleukin (IL-6) might play a role.

Pradhan and associates studied subjects from the Women’s Health Initiative (n = 75,343) who had suffered an incident coronary heart disease event (n = 304). In their analysis, they compared CRP and IL-6 levels in persons with incident CHD vs. controls.

Although both baseline CRP and IL-6 were found to predict (independently) CHD events, only CRP levels were increased by the use of HRT. Comparatively, baseline CRP and IL-6 levels demonstrated greater effect on subsequent CHD events than did use or nonuse of HRT. Pradhan et al observe that it is the CRP level, rather than use of HRT, which is the primary determinant of subsequent risk for CHD events.

Pradhan AD, et al. JAMA. 2002;288: 980-987.

Dr. Kuritzky, Clinical Assistant Professor, University of Florida, Gainesville, is Associate Editor of Internal Medicine Alert.