In the February 17 issue of the New England Journal of Medicine (1) Hambrecht et.al. found a positive effect of exercise on endothelial function (ENF) in coronary patients. It is very significant since exercise has also a favorable effects on the known cardiovascular risk factors (CVRF), including body mass index (BMI), insulin resistance and resting heart rate (RHR). How could we assess ENF (and it's improvements) in the daily clinical practice ?

The usual methods to assess ENF are either invasive or need ultrasound. Since blood flow depends on ENF, and flow mediated dilatation (FMD) may be induced by reactive hyperaemia after vessel occlusion and release (VOAR) (2), and determination of oxygen saturation (SpO₂) depends on adequate flow of the limb (3), we realized that the recovery time of SpO₂ (RTSpO₂) after VOAR could be an indicator of ENF (or dysfunction).

We started testing this idea in young patients without CVRF and found that RTSpO₂ is not more than 3 seconds. In a pilot group of 20 patients with several CVRF (half of them hypertensive), RTSpO₂ is more than 3 to 4 seconds. Only 3 of them had a positive Allen-test.

Since abnormal ENF is an early and central event in atherogenesis, we need assessing methods that are reproducible, inexpensive and easy to do if they are to be of widespread use, both for diagnose and follow up of improvements on ENF after interventions like exercise, diet or drugs. It would be very desirable that experts like Hambrecht et.al., or the group of Vita and Keaney (4), could compare RTSpO₂ to the standard methods and confirm if it could be of widespread use.

Enrique Sánchez-Delgado, MD

Heinz Liechti, M.Sc.

Laboratorios Solka,

Managua, Nicaragua

e-mail: heinz-liechti@scientist.com

1. Hambrecht R, et.al., Effects of Exercise on Coronary Endothelial Function in Patients with Coronary Artery Disease. N Engl J Med 2000; 342:454-60
2. Lehmann E, et al., Non-Invasive assessment of cardiovascular disease in diabetes mellitus. Lancet 1997; 350 (suppl I):14-19
3. Mertzlufft F, Nichtinvasive kontinuierliche Messung der arteriellen O₂ - Sättigung. In: Zander/Mertzlufft (Hrsg), Der Sauerstoff-Status des arteriellen Blutes, Symp. Mainz 1986, pp 109-119 (Karger, Basel 1988)
4. Vita J and Keaney J, Exercise - Toning Up the Endothelium ? N Engl J Med 2000; 342:503-505

(submitted to New England Journal of Medicine, March,1,2000)