EFFECT OF AGING ON MYOCARDIAL PERFUSION RESERVE

Myocardial perfusion reserve (hyperemic divided by basal myocardial blood flow) describes vasodilator responsiveness of coronaryresistive vessels. The effect of aging and gender on myocardial perfusion reserve remains controversial. Methods: We studied 56 normal volunteers (21 women, 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/kg/min, n = 10). For comparative analysis, patients were grouped according 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. There was an increase in basal flow with age (r = 0.45, p < 0.025), although 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 < 0.05 versus all groups <70 yr). Conclusion: Myocardial blood flow during basal and hyperemia conditions are roughly comparable up to 60 yr of age. Above this age, there is significant increase in basal flow associated with an increase in systolic blood pressure. Above 70 yr, there is a significant reduction in hyperemic flow, and thus myocardial perfusion reserve independent of hemodynamic response to vasodilator stress.