Feature-Tracking Method Can Estimate Right Ventricular Contractile Properties in Rats With Pulmonary Hypertension

Haruka Sato; Yui Takahashi; Taiki Hasegawa; Yuka Someya; M Nishiyama; Ayana Matsumoto; Natsuki Morita; Chiyohiko Shindoh; Hideki Ota; Ryuta Kawashima

doi:10.1253/circrep.cr-25-0028

June 20, 2025Circulation ReportsOpen Access

Feature-Tracking Method Can Estimate Right Ventricular Contractile Properties in Rats With Pulmonary Hypertension

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Why the study?

It was not determined whether right ventricular longitudinal strain measured with a feature-tracking method can accurately assess right ventricular contractility.

Does right ventricular longitudinal strain with a feature-tracking method accurately assess right ventricular contractility compared to right ventricular ejection fraction in rats with pulmonary hypertension?

Key Points

To determine whether right ventricular longitudinal strain assessed via feature-tracking cardiovascular magnetic resonance reflects right ventricular myocardial contractility more accurately than ejection fraction in pulmonary arterial hypertension.
Administered subcutaneous monocrotaline (n=19) or solvent control (n=4) to rats to induce pulmonary arterial hypertension.
Performed 7-T retrospective electrocardiogram-gated cine magnetic resonance imaging at four weeks to assess right ventricular longitudinal strain and ejection fraction, followed by invasive right ventricular pressure measurements.
Isolated right ventricular trabeculae to measure electrically stimulated contractile force and maximum rate of force development (dF/dt).
Monocrotaline-treated rats exhibited significantly elevated systolic right ventricular pressure alongside reduced developed force and maximum dF/dt compared to control rats.
Right ventricular longitudinal strain was impaired across all monocrotaline-treated rats and correlated linearly with maximum dF/dt, whereas right ventricular ejection fraction remained preserved (>40%) in 8 of 16 evaluated monocrotaline rats despite verified contractile decline.

Structured PICO

Does right ventricular longitudinal strain with a feature-tracking method accurately assess right ventricular contractility compared to right ventricular ejection fraction in rats with pulmonary hypertension?

P

Population

23 male Sprague-Dawley rats weighing 180 g (n=19 monocrotaline-induced pulmonary hypertension model, n=4 controls).

I

Intervention

Subcutaneous injection of monocrotaline (60 mg/kg) to induce pulmonary hypertension, followed by cardiovascular magnetic resonance (CMR) feature-tracking analysis at 4 weeks.

C

Comparator

Subcutaneous injection of an equal volume of solvent.

O

Outcome

Correlation of feature-tracking-based right ventricular longitudinal strain (RVLS) and right ventricular ejection fraction (RVEF) with contractile properties (maximum dF/dt) of RV muscle trabeculae at 4 weeks.surrogate

Right ventricular longitudinal strain assessed by feature-tracking CMR reflects right ventricular contractile properties more accurately and earlier than right ventricular ejection fraction in a rat model of pulmonary hypertension.

Limitations

Maximum dF/dt was measured in trabeculae at a constant sarcomere length of 2.0 µm, while RVLS and RVEF with CMR can change depending on preload and afterload.
Did not use a conventional technique such as magnetic resonance tagging or speckle-tracking echocardiography to obtain RVSL.
Did not investigate pathological or biochemical changes such as myocardial fibrosis.

Implication

Should not change practice yet; leaves open whether RV strain outperforms RVEF for early contractility in human PH.

Abstract

Background: Right ventricular (RV) function is a prognostic factor in patients with pulmonary arterial hypertension (PAH). Cardiovascular magnetic resonance (CMR) imaging has been used to assess RV function. However, it is not determined whether RV longitudinal strain (LS) with a feature-tracking method can accurately assess RV contractility. In this study, feature-tracking-based RVLS and RV ejection fraction (RVEF) were compared with contractile properties of RV muscle obtained from rat hearts with PAH. Methods and Results: Monocrotaline (MCT-rats, n=19) or solvent (Ctr-rats, n=4) was injected subcutaneously into rats. Four weeks after the injection, retrospective electrocardiogram-gated cine magnetic resonance (8 phases/beat) was imaged using a 7-T magnetic resonance imaging (MRI) scanner and RV pressure was measured. Trabeculae were dissected from the RV and electrically stimulated. Force was measured and maximum dF/dt was calculated as a parameter of contractile properties. Compared with Ctr-rats, MCT-rats showed higher systolic RV pressure. RVLS in all MCT-rats was lower than that in Ctr-rats, while RVEF was preserved (>40%) in 8 out of 16 MCT-rats. MCT-rats showed lower developed force and maximum dF/dt than Ctr-rats. Maximum dF/dt was linearly correlated with RVLS. In contrast, whether RVEF was preserved, maximum dF/dt was decreased in MCT-rats. Conclusions: The present study suggests that RVLS with a feature-tracking method can assess RV contractile properties more accurately than RVEF in rats with PAH. It is useful to estimate the RV function based on feature tracking.