EFFECT OF AGING ON MYOCARDIAL PERFUSION RESERVE

Myocardial perfusion reserve (hyperemic divided by basal myocardial bl ood flow) describes vasodilator responsiveness of coronaryresistive ve ssels. The effect of aging and gender on myocardial perfusion reserve remains controversial. Methods: We studied 56 normal volunteers (21 wo men, 35 men; aged 50 +/- 20 yr, range 21-86 yr) with O-15-water PET to measure myocardial blood flow during basal and hyperemic stales with intravenous dipyridamole (0.56 mg/kg, n = 46) or adenosine (140 mu g/k g/min, n = 10). For comparative analysis, patients were grouped accord ing to age: <30 yr (n = 11), 30-49 yr (n = 18), 50-69 yr (n = 15) and greater than or equal to 70 yr (n = 12). Results: Overall, basal flow was 1.00 +/- 0.26 ml/min/g and hyperemic flow was 3.31 +/- 1.38 ml/min /g, resulting in a myocardial perfusion reserve of 3.38 +/- 1.35. Ther e was an increase in basal flow with age (r = 0.45, p < 0.025), althou gh hyperemic flow was only lower in patients greater than or equal to 70 yr, causing a significant reduction in myocardial perfusion reserve : 3.54 +/- 0.96 in <30 yr, 4.23 +/- 1.35 in 30-49 yr, 3.51 +/- 1.21 in 50-69 yr and 1.94 +/- 0.46 in greater than or equal to 70 yr (p < 0.0 5 versus all groups <70 yr). Conclusion: Myocardial blood flow during basal and hyperemia conditions are roughly comparable up to 60 yr of a ge. Above this age, there is significant increase in basal flow associ ated with an increase in systolic blood pressure. Above 70 yr, there i s a significant reduction in hyperemic flow, and thus myocardial perfu sion reserve independent of hemodynamic response to vasodilator stress .