Regional myocardial strain before and after mitral valve repair for severemitral regurgitation

Magnetic resonance tagging (MRI) can be used to study intramyocardial train s in human in vivo. We wished to determine whether patients with severe mit ral regurgitation demonstrate subtle myocardial contractile dysfunction des pite normal left ventricular (LV) ejection fraction (EF) and how mitral val ve repair (MVR) may preserve EF in such patients. MRI was performed on seve n patients with severe mitral regurgitation (mean age +/- SD, 65 +/- 13 yea rs) and normal EF day 1 (range, 0-8 days) before (Pre) and week 8 +/- 3 aft er (Post) MVR and on nine normal volunteers (mean age, 32 +/- 4). LV mass i ndex (LVMI), end-diastolic and end systolic volume, mass/volume ratio, EF, and sphericity index were measured Pre and Post. Two-dimensional strain ana lysis of MR tagged images was performed and expressed as Ll (greatest systo lic lengthening, radial in normal subjects), L2 (greatest systolic shorteni ng, circumferential in normals), and beta (angular deviation of L1 from the radial direction). LVMI fell from 142 +/- 38 g/m(2) Pre to 117 +/- 44 g/m( 2) Post (p less than or equal to 0.008) as did LV end-diastolic volume (117 +/- 26 to 69 +/- 12 ml, p less than or equal to 0.003), whereas, EF remain ed unchanged (59 +/- 7% at both time points). LV mass/volume ratio increase d from 2.2 +/- 0.3 g/ml Pre to 3.1 +/- 0.4 g/ml Post (p less than or equal to 0.02) and sphericity index fell from 0.86 +/- 0.10 to 0.71 +/- 0.13 (p = 0.02). In the short axis, L1 was greater in patients with mitral regurgita tion than normal subjects (19 +/- 9% vs 16 +/- 6%, p less than or equal to 0.003) and tended to increase further after MVR (21 +/- 8%, p less than or equal to 0.06 vs. Pre). beta was abnormal in mitral regurgitation (19 +/- 8 vs. 12 +/- 8. degrees,, in control subjects, p < 0.0001) and remained abno rmal after MVR (19 +/- 9 degrees.). L2 in the short axis was depressed in m itral regurgitation compared with control subjects, (12 +/- 6% vs. 21 +/- 6 %, p less than or equal to 0.001) and was further depressed after MVR (9 +/ - 7%, p, < 0.001 vs. Pre). As detected by MRI, regional myocardial strains are abnormal in severe mitral regurgitation despite normal EF, characterize d by increased short-axis, systolic lengthening that is abnormally directed and by reduced shortening. After MVR, the further increase in short-axis l engthening may preserve EF despite its, abnormal, direction and a fall in s hortening. The increase in short-axis lengthening may be due in part to the reduction in LV sphericity after MVR.