Methods. 23 consecutive patients (61.2±6.8 years; 12 women) with suspected and known stable CAD were enrolled. Within 7 days all patients underwent non-invasive assessment of myocardial blood flow (MBF) and coronary flow reserve (CFR), obtained by a dynamic acquisition with CZT and Tc99-MIBI, and invasive assessment of coronary anatomy with the estimation of FFR values in at least one main coronary artery showing an intermediate coronary lesion (40-90% stenosis). The values of stress (adenosine pharmacological test) and rest MBF were calculated semi-automatically by a net retention model. The values of CFR were calculated as MBF ratio (MBF stress / MBF rest). Additionally, flow difference (FD) as the stress MBF minis the rest MBF was calculated. FFR was calculated invasively during the steady-state (60-90 sec) adenosine induced hyperemia as a ratio of the mean distal intracoronary pressure to the mean arterial pressure.
Results. 7(30%), 3(13%), and 2(9%) patients had >70% coronary lesions in 1, 2, or 3 vessels, respectively. Complete coronary occlusions were revealed in 2 vessels from 2 patients, while 35(38%) vessels did not show any relevant coronary luminal narrowing. FFR was assessed in 28 vessels showing intermediate coronary lesions. The average FFR value was 0.81±0.1. A moderate correlation between stenosis severity and FFR values was revealed (r=0.45; p=0.01). We found moderate correlations between stenosis severity and stress MBF (r=-0.46; p=0.01) as well as FD (r=-0.37; p=0.04). Significant correlations between FFR values and absolute myocardial perfusion parameters on CZT were revealed. Based on the ROC analysis, abnormal FFR values were best predicted by CZT-derived absolute stress MBF, MFR and FD with values of =0.54 ml/min/g, =1.48 and =0.18 ml/min/g, respectively showing the highest accuracy in predicting the presence of invasively determined myocardial inducible ischemia. Specifically, when regional MFR was below the cut-off value of =1.48, FFR was pathological in the 90% of the cases. Conversely, in the case of normal MFR values, FFR was preserved in the 78% of the cases
Conclusion. There is a good relationship between regional stress MFR and invasive FFR. In selected patients it could be of help in order to assess the hemodynamic significance of coronary artery stenosis non-invasively and to better stratify the risk of CAD.