Myocardial remodelling in aortic regurgitation: time to think beyond volumes and function?

Abstract

Current guideline criteria for surgical intervention in chronic aortic regurgitation (AR) rely on fixed thresholds of left ventricular size and ejection fraction, but these metrics may overlook early myocardial injury and under-appreciate patient heterogeneity, particularly in women and older adults. Cardiovascular magnetic resonance (CMR) offers robust quantification of regurgitant volume, three-dimensional ventricular volumes, and both focal (late gadolinium enhancement) and diffuse (T1-mapping-derived extracellular volume) fibrosis. Observational studies have linked CMR-detected fibrosis to worse clinical outcomes and less favourable reverse remodelling after valve intervention, suggesting that fibrosis may mark the transition from compensated overload to irreversible myocardial damage. In this narrative review, we appraise the limitations of current guidelines, compare echocardiographic and CMR approaches to AR assessment, and summarize the evidence supporting myocardial fibrosis as a potential imaging biomarker for risk stratification. We discuss how integrating CMR-derived fibrosis metrics with volumetric and functional data could personalize timing of aortic valve intervention. While prospective studies are needed to validate fibrosis-guided decision-making, this evolving paradigm holds promise for earlier identification of patients at risk for irreversible myocardial injury, with the ultimate goal of preserving ventricular function and improving long-term outcomes.

Keywords: MRI; aortic regurgitation; aortic valve disease; valvular heart disease.

Graphical Abstract

(A) Multipanel figure of the quantification of aortic regurgitation (AR) on echocardiography. (A) Parasternal long axis (PLAX) view with colour flow Doppler showing severe AR. The colour baseline can be shifted in order to measure the proximal isovelocity surface area. (A, B). M-mode with colour flow doppler transecting the AR jet in the PLAX view to measure the proportion of the left ventricular outflow tract filled by the AR jet. (A, C). Apical 5 chamber view demonstrating jet of severe AR (a, d). Pulsed wave Doppler measured in the proximal descending aorta showing holodiastolic flow reversal. (B). Multipanel figure of the assessment of AR and myocardial remodelling by CMR. (B, A). Two-dimensional phase contrast imaging of the aortic arch at the level of the main pulmonary artery. Flow is measured in the descending aorta by drawing a contour in all phases. (B, B). Parasagittal balanced steady state free precession image of the aorta. Flow plane in (B, A). marked in red. (b, c). Flow profile in the descending aorta, showing holodiastolic flow reversal. (C) Strain imaging demonstrating global reduced global longitudinal strain. (D). Four-chamber extracellular volume (ECV) map showing patchy increase in ECV throughout the myocardium. (E). Late gadolinium enhancement image showing patchy non-infarct pattern scar throughout the myocardium (particularly in the inferior wall and septum). (F). Septal myocardial biopsy (unpublished data from our institution) from a patient with severe AR stained with Masson’s trichrome showing islands of replacement fibrosis within the myocardium. This patient had persistent LV dilatation without significant remodeling after AVR. Created in https://BioRender.com.

Figure 1

Sex-related differences in myocardial remodelling patterns in AR. Reprinted from Tower-Rader et al. creative commons license here http://creativecommons.org/licenses/by/4.0/. (A) Normal left ventricle. (B) Conical pattern of LV remodelling seen more commonly in women, and early in male AR remodelling. (C) Spherical remodelling more commonly seen in males.

Figure 2

Echocardiography for AR quantification. (A) PLAX view with colour flow Doppler showing severe AR. The colour baseline can be shifted in order to measure the proximal isovelocity surface area. (B) M-mode with colour flow Doppler transecting the AR jet in the PLAX view to measure the proportion of the left ventricular outflow tract filled by the AR jet. (C) Apical 5 chamber view demonstrating jet of severe AR. (D) Pulsed wave Doppler measured in the proximal descending aorta showing holodiastolic flow reversal.

Figure 3

Assessment of AR and myocardial remodelling by CMR. (A) Two-dimensional phase contrast imaging of the proximal ascending aorta just above the aortic valve. Flow is measured by drawing a contour (red) in all phases. (B) Parasagittal balanced steady state free precession image of the aorta- visual assessment of flow reversal can be performed. A flow plane could be planned (green dotted line) to quantify flow reversal in the descending aorta. (C) aortic regurgitation. (D) Four-chamber ECV map showing patchy increase in ECV throughout the myocardium. (E) LGE image showing patchy non-infarct pattern scar throughout the myocardium (particularly in the inferior wall and septum).

Figure 4

Algorithm for incorporating CMR into the assessment for early surgery in patients with AR where transthoracic echocardiography is uncertain. (A) Two-dimensional phase contrast imaging of the proximal ascending aorta just above the aortic valve. Flow is measured by drawing a contour (red) in all phases. Parasagittal balanced steady state free precession image of the aorta- visual assessment of flow reversal can be performed. A flow plane could be planned (green dotted line) to quantify flow reversal in the descending aorta. (B) 17 segment left ventricular bulls eye plot demonstrating a pattern of reduced GLS. (C) Four-chamber ECV map showing patchy increase in ECV throughout the myocardium.