Sydney, Australia - The caliber of the small veins and arteries in the eye may be useful in predicting the future risk of cardiovascular death, according to a new study [1].

The study, published online in Heart July 13, 2006, found that retinal vascular caliber predicted CHD death independent of traditional cardiovascular risk factors in men and women aged 49 to 75 years, but not in older people.

The researchers, led by Dr Jie Jin Wang (University of Sydney, Australia), explain that microvascular disease may have a role in CHD pathogenesis and that the retinal microvasculature offers an easily accessible site for noninvasive evaluation of the condition of the microcirculation.

In an interview with heartwire, coauthor Dr Paul Mitchell (University of Sydney, Australia) noted that screening people for heart disease this way may not be feasible at present but could be in the future. "At present, this is not something that can be done in a family doctor's office or even a specialist's office very easily, as it is still a research tool. Retinal photos need to be taken and graded in a standardized manner. But moves are under way to try to automate the assessment using a specialized scanning device for the eye that would be relatively easy and quick to perform. This is not yet feasible, as a number of issues still need to be overcome, although the prospect for its successful development in the future I think is high," he commented.

In the paper, Wang, Mitchell, and colleagues point out that previous studies have suggested a link between retinal arteriolar changes and CHD and that several of these studies reported a stronger link in women than in men. For example, the Atherosclerosis Risk in Communities (ARIC) study found that a smaller arteriole-to-venule ratio (AVR; the ratio of the caliber of retinal arterioles to that of venules) was associated with a higher risk of incident CHD death in women but not in men. Wang et al point out that there is a need to confirm these findings in other populations and to establish whether lower AVR represents narrower arterioles, wider venules, or both.

They therefore investigated these issues in the Blue Mountains Eye Study—a population-based cohort of 3 340 predominantly white people aged 49 years or older at the start of the study in 1992, who all had retinal photographs gradable for retinal-vessel caliber taken at baseline. CHD-related death was confirmed from the Australian National Death Index.

During the nine years of the study, 78 women (4.1%) and 114 men (7.8%) had incident CHD-related deaths, and there was an approximate doubling in risk per standard-deviation increase in venular caliber, after adjustment for traditional risk factors. But this association was seen only in those aged 75 or younger.

In addition, in women aged 49 to 75 years, smaller AVR and narrower arterioles were associated with CHD death, with a 1.3- to twofold increase in the risk of CHD death with each standard-deviation decrease in arteriolar caliber, supporting the hypothesis that microvascular disease may be more prominent in CHD among women.

There was a borderline significant association between AVR and CHD death in men aged 49 to 75 years, which strengthened after stratification and became significant in men without hypertension (but not in men with hypertension). The authors write: "This association in men without hypertension is driven mainly by increasing venular caliber and contrasts with the situation in women, where increasing venular caliber was associated with CHD deaths in women with hypertension (rather than women without hypertension) and suggests that microvascular disease processes may affect men and women differently."

They say that, to their knowledge, this study is the first not only to examine the AVR but also specifically to examine arteriolar and venular calibers and CHD death and that they have shown that the relationship between small AVR and CHD death in women reflects both narrower arterioles and wider venules. They note that wider venular calibers has been linked to several traditional CHD risk factors—namely, smoking, systemic inflammation, higher total serum cholesterol, measures of atherosclerosis, and obesity—and that wider venules may be a marker for the severity of these risk factors, just as arteriolar narrowing is a marker for the severity of hypertensive damage.

The authors caution that the number of CHD deaths was small in this study and the findings need confirmation in other populations. But they conclude that, if confirmed, these results imply that microvascular disease processes may have a more prominent role in CHD pathogenesis in women than in men and that there is a possible role for retinal venules and arterioles in CHD risk assessment in both men and women.