384 Morpho-functional analysis of subvalvular apparatus in mitral valve prolapse and response to dipyridamole stress echocardiography. A pilot study

Abstract

Abstract Aims Myocardial fibrosis has been found in papillary muscles (PM) and basal segment of left ventricular (LV) inferior-lateral wall in patients with mitral valve prolapse (MVP), which may be due to stretch from valve. Moreover, ST-segment depression is common in patients with MVP, despite low prevalence of epicardial coronary artery disease, and it is attributed to microvascular dysfunction or myocardial stretch. Longitudinal strain (LS) correlates with myocardial fibrosis, while dipyridamole stress echocardiography (DSE) identifies microvascular dysfunction. We aimed at assessing morphology and function of PM and left ventricular walls at rest and during DSE by LS, and at determining prevalence of microvascular dysfunction in patients with MVP. Methods and results Seven consecutive patients with MVP (age 55.4 ± 15.7 years, 57% female) and LV ejection fraction 64 ± 5% underwent DSE. Length and LS of PM were measured at rest and retrospectively compared with those of patients with ischaemic heart disease (n = 8, age 67.1 ± 10.1 years, 37% female) and healthy controls (n = 8, age 39.6 ± 13.3 years, 50% female). LS of PM and LV was also determined at rest and during stress in MVP. Length of PM did not differ among groups, but in MVP, posterior PM was longer than the anterior PM (24 ± 3.8 vs. 20.6 ± 3.6 mm, P = 0.028). Significant difference in resting PM LS was found among groups (overall P = 0.04), with PM LS value in MVP (16.7 ± 7.1%) intermediate between ischaemic (14.2 ± 3.2%) and controls (20.5 ± 2.7%). No difference was found between rest and stress LS of PM in MVP. Global LS tended to increase in MVP during DSE compared to rest (23.1 ± 3.8% vs. 21.1 ± 2.6%, respectively, P = 0.07), while no significant difference between rest and stress LS was found in every LV myocardial segments. Nevertheless, in MVP, LS of LV inferior-lateral wall tended to improve under DSE in patients with mild regurgitation (19.7 ± 4.6 vs. 14.2 ± 5 at rest), but to decrease (16 ± 6.1 vs. 20.3 ± 2.3 at rest) in patients with severe mitral regurgitation (P = 0.006 for interaction). ST-segment depression was elicited by DSE in 29% of MVP. No significant difference in echocardiographic parameters was found between patients with and without ST-segment depression. Conclusions In MVP, sub-valvular apparatus may have peculiar morpho-functional features. DSE does not alter LS of PM, neither of LV walls, except for inferior-lateral wall, which impairs in severe mitral regurgitation. Prevalence of microvascular dysfunction is comparable to that of the general population.