We performed a systematic search using MEDLINE and Google Scholar. Keywords included in our research were CMR, Aortic Stenosis (AS) and Myocardial Fibrosis. The chosen articles were included in our study, if they supported a solid approach in left ventricular changes in patients with aortic valve stenosis.
The most important findings of the studies consisted on:
Myocardial fibrosis
is stated as a substantial expansion collagen fiber in myocardial tissue (4). There have been described different subtypes of myocardial fibrosis:
-Reactive interstitial fibrosis
-Infiltrative interstitial fibrosis
-Replacement fibrosis
The extent of fibrosis in AS is related with the intensity of the patient’s symptoms, the decline on cardiac function and physical capacity, as well as the increased mortality (5).
Late gadolinium enhancement (LGE) is well established method capable to quantify myocardial replacement fibrosis and scar. In AS patients, the predominant pattern has midwall location (fig.5) and can be linear, focal(multi), patchy or diffuse in appearance (6). The presence and extent of LGE represent a promising stratification marker (7).
Use of novel techniques as T1 mapping, allows quantitative assessment of diffuse myocardial fibrosis with the use of T1 native and extracellular volume (ECV) fraction (8), which are well validated, and biopsy proven. Both appear to be elevated in hypertrophic diseased myocardium (9), although T1 native is mostly unable to discriminate between healthy individuals and asymptomatic patients with low moderate degree of AS (8). A new parameter indexed extracellular volume (iECV) quantifies the total LV extracellular volume indexed to body surface area and appears to provide a greater discrimination between disease states (10).
LV (left ventricle) hypertrophy
is the response to pressure overload, caused by aortic valve stenosis, but it is reported a serious heterogeneity in the degree of developed hypertrophy in patients with comparable aortic orifice narrowing (11). Most importantly, the degree of LV hypertrophy has been correlated with adverse early and long-term postoperative outcomes (12). LV wall thickness is measured in an end diastolic CMR cine image. There have been described 4 different geometrical patterns of LV thickening: -Concentric remodeling - Concentric hypertrophy (most common) - Asymmetric remodeling -Asymmetric hypertrophy (13).
The burden of Aortic valve calcification (AV Calcium score)
is an additional indication of disease progression and adverse prognosis (14),
following a straight association between total measurements of calcified plaques and grade of AS (15).
The biggest concern is as the only treatment of AS is valve replacement, it is extremely important to be able to provide the optimal timing for valve intervention as the natural history of the disease is lading from hypertrophic myocardial response to LV decompensation, resulting to heart failure (16). CMR can assess the consequences of the AS on remodeling of LV myocardium by conjoining the evaluation of LV function and extent of myocardial fibrosis, but can also provide valuable preprocedural information’s, as well as post procedural impact assessment and possible complications uncovering (17).