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

Miki Hirose ¹ Danfu Ma ² Kazumi Shimada ¹ Tomohiko Yoshida ^3,4 Katsuhiro Matsuura ⁵ Pitipat Kitpipatkun ¹ Akari Hatanaka ¹ Yanbing Zhao ² Ken Takahashi ⁶ Ryou Tanaka ^1* Lina Hamabe ^7*

• ¹ Veterinary Teaching Hospital, Veterinary Medicine, Tokyo University of Agriculture and Technology, Tokyo, Japan, Tokyo, Japan
• ² College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China, Nanjing, China
• ³ Diagnostic Center for Animal Health and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan
• ⁴ Department of Small Animal Medical Centre, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan, Hokkaido, Japan
• ⁵ Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States
• ⁶ Department of Pediatrics and Adolescent Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan, Tokyo, Japan
• ⁷ Department of Veterinary Clinical Oncology, Tokyo University of Agriculture and Technology, Tokyo, Japan, Tokyo, Japan

The mitral inflow spectral is expressed as two separate waves; early diastole transmitral flow velocity (E) and late diastolic trans-mitral flow velocity (A) waves. When heart rate (HR) increases, and the diastolic time diminishes the mitral flow pattern change 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 gradients (IVPG) based on color-M-modeechocardiography are two techniques established in recent years with good repeatability at cardiac function evaluation especially diastolic. Hypothesis/Objective: We hypothesize that IVPG and E/E' are differentially influenced by mitral inflow patterns. Animals: 66 hypertensive cardiomyopathies (HTN-CM) induced by abdominal aorta coarctation, and 33 sham-operated rats were divided into six 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 weeks after the operation. After code EA-separation=1, EA-half-separation=2, and EA-fusion=3, Pearson's correlation tests were performed. Results: Both E and E' in EA-fusion (1.04±0.13 and 7.65±0.84) are higher than the EA-separation pattern in all rats (0.91±0.10 and 5.51±0.78, p<0.001). The preload change has more impact on E' than E (0 .443 vs 0.218, p <0.001, respectively), which leads to decreased E/E' in EA-fusion. Total IVPG and basal IVPG positively correlated with mitral inflow pattern (0.265 and 0.270, p <0.001), while mid-to-apical IVPG was not (0.070, p=0.281). Conclusions: Mitral inflow pattern positively correlates with basal IVPG, E, and E'. Mid-to-apical IVPG was independent of mitral inflow patterns, while E/E' tend to be lower when the mitral inflow pattern changed from EA-separation to EA-fusion.