Three-Directional Evaluation of Mitral Flow in the Rat Heart by Phase-Contrast Cardiovascular Magnetic Resonance
March
Three-Directional Evaluation of Mitral Flow in the Rat Heart by Phase-Contrast Cardiovascular Magnetic Resonance
Kristine Skårdal 0 1 2
Emil KS Espe 0 1 2
Lili Zhang 0 1 2
Jan Magnus Aronsen 0 1 2
Ivar Sjaastad 0 1 2
0 1 Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo , Oslo , Norway , 2 KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo , Oslo , Norway , 3 Bjørknes College , Oslo , Norway
1 Funding: This work was supported by the South- Eastern Norway Regional Health Authority, Anders Jahre's fund for the Promotion of Science, the Research Council of Norway, Familien Blix' Fond Til Fremme Av Medisinsk Forskning and Stiftelsen KG Jebsen
2 Editor: Juan Carlos del Alamo, University of California San Diego, UNITED STATES
Determination of mitral flow is an important aspect in assessment of cardiac function. Traditionally, mitral flow is measured by Doppler echocardiography which suffers from several challenges, particularly related to the direction and the spatial inhomogeneity of flow. These challenges are especially prominent in rodents. The purpose of this study was to establish a cardiovascular magnetic resonance (CMR) protocol for evaluation of three-directional mitral flow in a rodent model of cardiac disease. Three-directional mitral flow were evaluated by phase contrast CMR (PC-CMR) in rats with aortic banding (AB) (N = 7) and sham-operated controls (N = 7). Peak mitral flow and deceleration rate from PC-CMR was compared to conventional Doppler echocardiography. The accuracy of PC-CMR was investigated by comparison of spatiotemporally integrated mitral flow with left ventricular stroke volume assessed by cine CMR.
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OPEN ACCESS
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
Competing Interests: The authors have declared
that no competing interests exist.
Purpose
Results
PC-CMR portrayed the spatial distribution of mitral flow and flow direction in the atrioventricu
lar plane throughout diastole. Both PC-CMR and echocardiography demonstrated increased
peak mitral flow velocity and higher deceleration rate in AB compared to sham. Comparison
with cine CMR revealed that PC-CMR measured mitral flow with excellent accuracy.
Echocardiography presented significantly lower values of flow compared to PC-CMR.
Conclusions
For the first time, we show that PC-CMR offers accurate evaluation of three-directional mitral blood flow in rodents. The method successfully detects alterations in the mitral flow pattern in response to cardiac disease and provides novel insight into the characteristics of mitral flow.
Introduction
Mitral flow is an important entity in cardiac diseases involving diastolic dysfunction and
heart failure. The mitral flow in diastole is a result of two main components; the initial
passive filling, E, caused by the depressurization of the ventricle, and the active filling, A,
resulting from atrial contraction. The flow pattern depends on the loading conditions of the heart,
thus in cardiac disease, the flow pattern is affected and changing in response to disease
progression. Accordingly, evaluation of the mitral flow pattern is an important part of assessing
cardiac function.
Traditionally, mitral flow is evaluated using pulsed Doppler echocardiography, relying on
positioning a finite sampling volume at the assumed point of peak flow [
1,2
]. Since only the
flow component directed directly towards or away from the transducer is detected, geometric
correction is essential, but might be challenging, especially in small animals [3]. In addition,
the spatial mitral flow velocity profile is inhomogeneous across the valve [
4,5
].
Cardiovascular magnetic resonance (CMR) has successfully been applied to assess blood
flow in the major vessels in humans, and to observe regurgitation [
6–8
]. In the setting of mitral
flow, three-directional velocity encoded phase-contrast CMR (PC-CMR) can provide classical
flow parameters, such as peak mitral flow velocity and deceleration rate of the mitral flow
signal, as well as directional and distributional assessment of the mitral flow. Additionally,
profiting from complete spatial and temporal coverage of the flow profile, PC-CMR can be used to
measure the blood volume flowing through the mitral valve [
9
].
In the present study, we have established and validated a PC-CMR protocol for studying
three-directional time-resolved mitral inflow in rats. PC-CMR offers comprehensive evaluation
of mitral flow with new insight into its directional characteristics and spatial distribution in
healthy and diseased hearts.
Materials and Methods
Animal model
All procedures were approved by the Norwegian Animal Research Authority (FOTS ID 3820),
in accordance with the European Convention for the Protection of Vertebrate Animals used for
Experimental and other Scientific Purposes (ETS no.123). Male Wistar Hanno (...truncated)