Age–gender considerations on survival in patients undergoing radial artery grafting

I read with great interest the article by Pullan et al. [1] on the effect of patient sex on survival in patients undergoing isolated coronary artery bypass grafting (CABG) receiving a radial artery (RA). I congratulate them on their well-designed analysis. They concluded that men who received an RA graft when undergoing isolated CABG have a significant survival benefit; furthermore, RA makes no difference to long-term survival in female patients [1]. Median follow-up was 7.02 (interquartile range 4.1–10.1) years. Recently, we published our results on long-term patients’ survival after first-time isolated CABG with left internal thoracic artery (LITA) to left anterior descending artery (LAD) graft and either RA or saphenous vein graft as a secondary graft. We performed subgroup analysis to delineate the effect of age, gender and diabetes. We showed that CABG using the RA in combination with the LITA-to-LAD group is associated with improved long-term overall survival (P = 0.03). The long-term data allowed delineation of the clinical benefit beginning at 5 years postoperatively. Median follow-up was 9.4 (interquartile range 5.7–11.9) years. Follow-up in the RA subgroup was 10.3 (interquartile range 5.7–11.9) years. Statistically, the benefit was most pronounced in the following order: diabetics (P = 0.005), women (P = 0.02) and the elderly (P = 0.04) [2]. The use of RA for CABG has undisputable advantages: the length of the conduit per se (approximately around 20 cm), its large diameter, its exposure to arterial blood pressure, the thickness of the wall and its lower susceptibility to atherogenesis. There is a difference in survival between males and females using RA as a second conduit for the following reasons. Receptor-mediated (acetylcholine-induced) and receptor-independent (calcium ionophore-induced) factors modulate endothelium relaxation. Shapira et al. [3] have shown enhanced physiological characteristics related to endothelial production or vessel relaxation in response to nitric oxide in RA when compared with other conduits. Men have a higher diameter of the RA compared with women [4]. Joannides et al. [4] reported the influence of vascular dimension on gender difference in flow-dependent dilatation of peripheral conduit arteries. Herman et al. [5] have shown deleterious effect of physiological levels of androgen hormone in men and the decrease of androgen levels related to age as a benefit on coronary artery disease and endothelium function in the developing atherogenic process. The oestrogen has its own cardioprotective effects elevating the HDL, lowering the LDL, reducing the fibrinogen, maintaining the vasculature tone, inhibiting platelet aggregation and adhesion and inhibiting the development of atherosclerotic plaques [6]. Majmudar et al. [6] showed the positive effects of oestrogen in increasing the nitric oxide release in the arterial vasculature. In conclusion, male patients who had RA conduits have better results over the age of 60 years because of diminishing of androgen hormone and its deleterious effect on the arterial wall [5]. Oestrogen hormone in the premenopausal female plays a positive role in modulation of endothelium flow-mediated dilatation of the RA [6]. Age–gender considerations should be taken into account on using RA or arterial conduits grafting.