Correspondence

Coronary Microvascular Dysfunction

N Engl J Med 2007; 356:2324-2325May 31, 2007

Article

To the Editor:

Camici and Crea (Feb. 22 issue)1 review the different causes and mechanisms of coronary microvascular dysfunction. However, coronary microvascular dysfunction due to aging deserves further comment. Age is a recognized risk factor for cardiovascular disease, and senescence is associated with morphologic and functional changes in the coronary microvasculature.2 Studies in animals have shown that coronary flow reserve and the endothelium-dependent dilatation of the resistance arteries decrease with age.3 It has been suggested that endothelium-dependent dilatation of the resistance coronary arteries evoked by acetylcholine may decrease with age in humans.4

The mechanisms underlying the age-associated reduction in the ability of the coronary microvasculature to dilate in response to acetylcholine are controversial. With advancing age, nitrous oxide–dependent mechanical and agonist-mediated endothelial vasodilatation is reduced in humans and animals.5 Coronary microvascular dysfunction due to aging should not be underestimated. Although pharmacologic treatment has been shown to restore coronary blood reserve in endothelial dysfunction due to aging, its effect on the clinical outcome remains to be determined.

J. Roberto Duran, III, M.D.
George Taffet, M.D.
Baylor College of Medicine, Houston, TX 77030
duran@bcm.tmc.edu

5 References

1. 1

   Camici PG, Crea F. Coronary microvascular dysfunction. N Engl J Med 2007;356:830-840
   Full Text | Web of Science | Medline

2. 2

   Lakatta EG, Yin FCP. Myocardial aging: functional alterations and related cellular mechanisms. Am J Physiol 1982;242:H927-H941
   Web of Science | Medline

3. 3

   Toma BS, Wangler RD, DeWitt DF, Sparks HV Jr. Effect of development on coronary vasodilator reserve in the isolated guinea pig heart. Circ Res 1985;57:538-544
   Web of Science | Medline

4. 4

   Egashira K, Inou T, Hirooka Y, et al. Effects of age on endothelium-dependent vasodilation of resistance coronary artery by acetylcholine in humans. Circulation 1993;88:77-81
   Web of Science | Medline

5. 5

   Csiszar A, Ungvari Z, Edwards JG, et al. Aging-induced phenotypic changes and oxidative stress impair coronary arteriolar function. Circ Res 2002;90:1159-1166
   CrossRef | Web of Science | Medline

Author/Editor Response

We agree with Duran and Taffet that coronary microvascular function changes significantly with aging. Indeed, we stated, “In healthy persons, however, coronary flow reserve varies according to age and sex. Therefore, it is essential to compare data on coronary flow reserve in patients with data obtained in age-matched and sex-matched control subjects.” Using positron-emission tomography, Uren et al.1 and Chareonthaitawee et al.2 have shown that resting and hyperemic myocardial blood flow remain unchanged in persons up to 60 years of age. After 60 years of age, there is a significant increase in resting myocardial blood flow, associated with an increase in systolic blood pressure. After 70 years of age, there is a significant reduction in hyperemic myocardial blood flow and in coronary flow reserve. There are probably multiple causes of these age-related changes, and they remain incompletely understood.

Paolo G. Camici, M.D.
Imperial College, London W12 0NN, United Kingdom
paolo.camici@csc.mrc.ac.uk

Filippo Crea, M.D.
Catholic University, 00168 Rome, Italy

2 References

1. 1

   Uren NG, Camici PG, Melin JA, et al. Effect of aging on myocardial perfusion reserve. J Nucl Med 1995;36:2032-2036
   Web of Science | Medline

2. 2

   Chareonthaitawee P, Kaufmann PA, Rimoldi O, Camici PG. Heterogeneity of resting and hyperemic myocardial blood flow in healthy humans. Cardiovasc Res 2001;50:151-161
   CrossRef | Web of Science | Medline

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1. 1

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