Fast determination of regional myocardial strain fields from tagged cardiac images using harmonic phase MRI

Background-Tagged MRI of the heart is difficult to implement clinically bec ause of the lack of fast analytical techniques. We investigated the accurac y of harmonic phase (HARP) imaging for rapid quantification of myocardial s trains and for detailed analysis of left ventricular (LV) function during d obutamine stimulation. Methods and Results-Tagged MRI was performed in 10 volunteers at rest and d uring 5 to 20 mu g(-1) . kg(-1) . min(-1) dobutamine and in 9 postinfarct p atients at rest. We compared 2D myocardial strains (circumferential shorten ing, Ecc; maximal shortening, E-2; and E-2, direction) as assessed by a con ventional technique and by HARP. Full quantitative analysis of the data was 10 times faster with HARP. For pooled data, the regression coefficient was r=0.93 for each strain (P<0.001). In volunteers, Ecc and E-2 were greater in the free wall than in the septum (P<0.01), but recruitable myocardial st rain at peak dobutamine was greater in the LV septum (P<0.01). E-2 orientat ion shifted away from the circumferential direction at peak dobutamine (P<0 .01). HARP accurately detected subtle changes in myocardial strain fields u nder increasing doses of dobutamine. In patients, HARP-determined Ecc and E -2 values were dramatically reduced in the asynergic segments as compared w ith remote (P<0.001), and E-2 direction shifted away from the circumferenti al direction (P<0.001). Conclusions-HARP MRI provides fast, accurate assessment of myocardial strai ns from tagged MR images in normal subjects and in patients with coronary a rtery disease with wall motion abnormalities. HARP correctly indexes dobuta mine-induced changes in strains and has the potential for on-line quantitat ive monitoring of LV function during stress testing.