Effects of trans-mitral flow patterns and heart rate on intraventricular pressure gradients and E/E' in the early stage of a rat model of hypertensive cardiomyopathy.

Abstract

BACKGROUND: The mitral inflow spectral is expressed as two separate waves: early diastolic trans-mitral flow velocity (E) and late diastolic trans-mitral flow velocity (A) waves. When the heart rate (HR) increases and the diastolic time diminishes, the mitral flow pattern changes from EA-separation to EA-fusion. The E wave provides information about preload and diastolic function. Tissue Doppler imaging (TDI) and non-invasive intraventricular pressure gradient (IVPG) based on color-M-mode echocardiography are two techniques established in recent years with good repeatability in cardiac function evaluation, especially diastolic. HYPOTHESIS/OBJECTIVE: We hypothesize that IVPG and E/E' are differentially influenced by mitral inflow patterns. ANIMALS: A total of 66 hypertensive cardiomyopathy (HTN-CM) induced by abdominal aorta coarctation and 33 sham-operated rats were divided into 6 groups according to trans-mitral flow patterns. METHODS: Conventional echocardiography, TDI, and IVPG sampling were performed on rats under general anesthesia with 2.5% isoflurane at 3&#x202f;weeks after the operation. After code EA-separation&#x202f;=&#x202f;1, EA-half-separation&#x202f;=&#x202f;2, and EA-fusion&#x202f;=&#x202f;3, Pearson's correlation tests were performed. RESULTS: Both E and E' in EA-fusion (1.04&#x202f;&#xb1;&#x202f;0.13 and 7.65&#x202f;&#xb1;&#x202f;0.84) are higher than the EA-separation pattern in all rats (0.91&#x202f;&#xb1;&#x202f;0.10 and 5.51&#x202f;&#xb1;&#x202f;0.78,&#x202f;<&#x202f;0.001). The preload change has more impact on E' than E (0.443 vs. 0.218, p&#x202f;<&#x202f;0.001, respectively), which leads to decreased E/E' in EA-fusion. Total IVPG and basal IVPG positively correlated with the mitral inflow pattern (0.265 and 0.270,&#x202f;<&#x202f;0.001), while mid-to-apical IVPG was not (0.070,&#x202f;=&#x202f;0.281). CONCLUSION: The mitral inflow pattern positively correlates with basal IVPG, E, and E'. Mid-to-apical IVPG was independent of mitral inflow patterns, while E/E' tended to be lower when the mitral inflow pattern changed from EA-separation to EA-fusion.