P1246Myocardial transit time (MTT) - a novel and easy-to-perform CMR parameter to assess microvascular disease

Abstract

Abstract Background Myocardial microvascular disease is primarily characterized by arteriolar obliteration and capillary rarefaction, and may occur during the disease course of different disorders. With the present study, we introduce a novel and easy-to-perform cardiovascular magnetic resonance (CMR) parameter named “myocardial transit time” (MTT). Methods N=20 patients with known hypertrophic cardiomyopathy (HCM) and N=20 control patients without relevant cardiac disease underwent dedicated CMR studies on a 1.5-T MR scanner (Ingenia, Philips, Best, The Netherlands). The CMR protocol comprised cine and late-gadolinium-enhancement (LGE) imaging and first-pass perfusion acquisitions at rest for MTT measurement: an imaging plane covering both the aortic bulbus and the coronary sinus was planned in order to track the flooding of gadolinium. MTT was defined as the time interval between first appearance of gadolinium in the aortic bulbus and the subsequent appearance of gadolinium in the coronary sinus reflecting the transit time of gadolinium in the myocardial microvasculature (in the absence of epicardial coronary artery disease). Results There was no significant difference in left ventricular ejection fraction (LV-EF) between both groups: 61% (55–68%) in HCM patients vs. 60% (58–67%) in controls (p=ns) whereas LV mass was significantly higher in HCM patients (79g/m2 (63–98g/m2) vs. 50g/m2 (45–56g/m2) in controls, p<0.001). The extent of LGE was 17% (6–22%) in HCM patients while there was no LGE at all in the control group (p<0.001). MTT at rest was substantially longer in HCM patients: 11.0sec (9.1–14.5sec) vs. 6.5sec (4.8–8.4sec) in controls (p<0.001). Correlation analyses revealed a significant relationship between LV mass and MTT (r = +0.64, p<0.001) as well as between LGE extent and MTT (r=0.75, p<0.001). ROC analysis resulted in an area-under-curve (AUC) of 0.90 for MTT and showed an optimal sensitivity/specificity cut-off of 7.85sec to differentiate HCM from controls. Patient characteristics HNCM patients (N=20) Control group (N=20) p-value Absolute MTT, sec 11.0 (9.1–14.5) 6.5 (4.8–8.4) <0.001 MTT indexed to heart rate 0.159 (0.100–0.198) 0.081 (0.063–0.106) <0.001 No. of patients with MTT <7.85 sec, n (%) 2 (10) 15 (75) <0.001 MTT = Myocardial Transit Time, HNCM = Hypertrophic Non obstructive Cardiomyopathy. Multiple images illustrating MTT method Conclusion “Myocardial transit time” (MTT) is a novel and easy-to-perform CMR parameter that allows a quick assessment of the extent of myocardial microvascular disease. This novel CMR parameter may open new vistas in the assessment of microvascular disease - not only in HCM patients. Future studies will show the usefulness and clinical relevance of this novel CMR parameter.