Intraventricular pressure gradient: a novel colour M-mode echocardiographic-derived imaging modality to assess and predict the alterations following acute myocardial infarction
Authors: El-Husseiny H M , Mady E A , Takahashi K , Tanaka R 
Published: January 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Myocardial infarction (MI), caused by partial or total interruption of myocardial blood supply, is among the leading causes of morbidity and death. It can go silent (undetected), or it can be a catastrophic occurrence with severe hemodynamic alterations and abrupt death. Hence, immediate diagnosis or even prediction of these changes is really significant. Being the gold standard technique, echocardiography is typically adopted to identify heart dysfunctions. However, it exhibits a modest aptitude to foresee these variations. Intraventricular pressure gradient (IVPG) was introduced recently as a precise colour M-mode echocardiographic (CMME)-derived diastolic function imaging modality to assess the cardiac performance. Yet, its potential to assess and anticipate the alterations post-acute MI was not explored.

Purpose
The chief goal of this work is to study the efficacy of IVPG to measure and expect the alterations of rats’ cardiac functions at early stages of MI induced by variable LAD suture occlusion sites.

Methods
Fifty-five male SD rats were operated. Three different LAD occlusion sites were adopted to induce MI. In one group, LAD was occluded at the junction between LA and LV (MI-H, n=20). The middle and low ligation sites were more distal away from the base in two distinct groups (MI-M, n=15, and MI-L, n=10). The typical thoracotomy was accomplished in sham animals without occlusion of LAD (Sham, n=10). The sham and survived MI animals were checked using conventional echocardiography and CMME-derived IVPG on days 1, 7, 14, and 21 post MI induction. Afterwards, they were euthanized after transcatheter hemodynamics recording under the effect of anesthesia. The heart sections were stained to calculate the infarction size.

Results
The MI-H animals showed the lowest survival rate (35 % vs. 66.67, and 80 % in MI-M and MI-L groups; respectively). Moreover, they presented the most serious cardiac and hemodynamic alterations. The values of mid-to-apical, mid, and apical IVPG segments were significantly (P&lt; 0.001) declined in MI-M and MI-H groups compared to sham on days 7, 14, and 21. Likewise, they presented a meaningful reduction of the total IVPG on days 14, and 21. Contrarily, the basal IVPG was markedly (P&lt; 0.0001) elevated. Despite the echocardiographic changes were firstly recorded on day 14, the variations in the IVPG were recorded on day 7. The IVPG variables were significantly (P&lt; 0.0001) correlated with the echocardiographic, the hemodynamic (LVSP, LVDP, LVEDP, +dP/dtmax, -dP/dtmin, Tau) variables, and the infarction size. Moreover, all IVPG indices could significantly predict the cardiac and hemodynamic alterations occurred in varied degrees of severity. The Bland-Altman test confirmed the reproducibility of our IVPG measures.

Conclusion
CMME-derived IVPG is a novel and promising imaging modality with superior ability than conventional echocardiography to assess and predict the alterations encountered due to acute MI.