[X-ray densitometric measurement of myocardial perfusion reserve in symptomatic patients without angiographically...

Patients with typical angina pectoris but without coronary artery disease (CAD) are distinct in clinical aspects. In only few patients no abnormality is detected. Most present at least one or more cardiovascular risk factors and/or signs of myocardial ischemia. As previous studies have shown, the coronary flow reserve is reduced in most of these cases. Regional measurements of the coronary flow reserve, performed by different approaches, have shown a profound variation in different myocardial areas. It is not yet clear, whether this heterogeneity is physiological or due to a pathologic process.

The aim of this study was the regional measurement of the myocardial perfusion reserve in patients without epicardial coronary stenoses using X-ray densitometry.

The myocardial perfusion reserve (MPR) for all patients in the coronary artery territories was 1.6 +/- 0.5 (LAD), 2.0 +/- 0.7 (RCx), and 2.2 +/- 0.6 (RCA). In hypertensive patients the MPR was significantly lower in all territories compared to normotensive patients (1.5 +/- 0.3 vs. 2.2 +/- 0.7 [LAD], 1.8 +/- 0.5 vs. 2.5 +/- 0.7 [RCx], 2.1 +/- 0.5 vs. 2.5 +/- 0.9 [RCA]). The rise time (AT) is inversely proportional to the perfusion. At rest it was significantly shorter in hypertensive patients compared to normotensive patients (5.0 +/- 1.0 s vs. 6.5 +/- 2.0 s [LAD], 4.8 +/- 1.1 s vs. 6.1 +/- 2.6 s [RCx], 5.9 +/- 1.4 s vs. 7.8 +/- 4.0 s [RCA]), while there was no difference at maximum papaverine-induced hyperemia. A statistical correlation between MPR and wall thickness was found only for the LAD area. The heterogeneity of perfusion under basal flow conditions was more pronounced in normotensive than in hypertensive patients, while under maximal hyperemia there was no detectable difference. There was no statistically significant correlation between the semiquantiative wash-in counts of myocardial scintigraphy and MPR.

In this group of symptomatic patients MPR is lower than the lower limit of normal MPR, which is 3 in healthy individuals according to the literature. Patients with known arterial hypertension show a more severely impaired MPR which is especially pronounced in the LAD area and can be explained by a higher perfusion at rest. According to the authors' approach X-ray densitometry in the setting of coronary angiography is feasible and cost-effective to obtain information about the microvasculature.