Reduced longitudinal contraction is associated with ischemic mitral regurgitation after posterior MI

Abstract

The role of left ventricular (LV) longitudinal contraction in ischemic mitral regurgitation (MR) remains unclear. We hypothesized that reduced longitudinal contraction disrupts normal mitral valve plane displacement during systole and leads to mitral valve tethering, thereby inducing ischemic MR. Twenty-three Yorkshire pigs underwent induction of different-sized posterior myocardial infarction (MI) using a percutaneous approach. The incidence of MR and its association with LV longitudinal strain were examined using speckle-tracking echocardiography at 1 mo post-MI to determine their relationship. A total of 17 pigs survived MI and completed the study. Pigs developed no more than mild MR after proximal left circumflex artery (LCx) occlusion (LCx group; n = 7). Addition of a first diagonal branch (D1) occlusion to LCx-MI (LCx + D1 group; n = 7) resulted in moderate to severe MR development 1 mo post-MI. LCx + D1 animals had lower longitudinal strain compared with the LCx group, whereas circumferential strain and LV rotation did not differ significantly. Posterolateral annular displacement toward the apex was significantly reduced in LCx + D1 animals, whereas the septal annular displacement was similar, suggesting an asymmetric mitral annular plane excursion in the LCx + D1 group. To exclude the contribution of papillary muscle infarction in MR development in our model, three pigs underwent obtuse marginal branch + D1 occlusion. None of these pigs developed significant MR after 1 mo. In conclusion, reduced longitudinal contraction contributes to the development of ischemic MR in a large posterior MI. NEW & NOTEWORTHY In this study, using our unique swine models of different-sized myocardial infarction, we showed, for the first time, that reduced longitudinal contraction contributes to the development of ischemic mitral regurgitation in a large posterior myocardial infarction. Our study adds new insights into the mechanisms of ischemic mitral regurgitation pathophysiology.

Cardiac function, haemodynamics, and valve competence with exercise in patients with heart failure with preserved ejection fraction and mild to moderate secondary mitral regurgitation

“…28 The loss of longitudinal systolic mechanics may play an important role in the development of lesser grade MR in patients with HFpEF as well through reduction in papillary muscle tension on the mitral apparatus. 29 Indeed, the group differences for LV global longitudinal strain were notably more striking than for LA strain, as shown in Figure 3. However, LA myopathy was also more advanced, as indicated by poorer strain, more remodelling, and steeper LA diastolic pressure-volume relationships at rest and exercise (Figure 4).…”

“…carefully compared 25 patients with isolated ‘lone’ AF without LV dysfunction to patients with HFrEF, showing that induction of moderate or severe MR required not just mitral annular dilatation, but also LV dilatation and dysfunction 28 . The loss of longitudinal systolic mechanics may play an important role in the development of lesser grade MR in patients with HFpEF as well through reduction in papillary muscle tension on the mitral apparatus 29 . Indeed, the group differences for LV global longitudinal strain were notably more striking than for LA strain, as shown in Figure .…”

Experimental models of cardiac physiology and pathology

“…This can be reproduced in large animals by creating large infarction in the left ventricular posterior wall in sheep and pigs. These ischemic mitral regurgitation models generally exhibit progressive deterioration of heart failure (180,181). Artery to venous fistula models are another common method to induce volume-overload heart failure in large animals (182).…”

Speckle-Tracking Echocardiographic Strain Analysis Reliably Estimates Degree of Acute LV Unloading During Mechanical LV Support by Impella

“…Although cardiac anatomy of the pig is very similar to that of humans, different orientation of the heart may have affected the analysis due to the software setting that was designed to analyze the human heart. Nevertheless, using the Q-Lab software, we have previously reported its feasibility and utility in evaluating function of the pig heart [21,22,9,23]. Finally, although the investigators were blinded for the unloading status, the Impella cannula was visible on LV unloading images and precluded complete blinding.…”