Potential role of fibrosis imaging in severe valvular heart disease

Currently, the most encountered valve diseases include aortic stenosis (AS) and mitral regurgitation (MR); data from population based studies have shown that approximately 9% of individuals aged 65 years or more have either MR or AS.1 w1 While indications for surgery are well defined in symptomatic patients, the optimal timing of surgery in asymptomatic severe AS or MR remains controversial. Currently, surgical intervention is considered in the presence of reduced left ventricular ejection fraction (LVEF), left ventricular (LV) dilatation, pulmonary hypertension, reduced exercise capacity, increased plasma concentrations of biomarkers (eg, N-terminal pro-brain natriuretic peptide (NT-proBNP)), and arrhythmias (eg, atrial fibrillation), since all these variables are associated with worse prognosis if treated medically.w2 w3 However, most of these variables are encountered only when AS or MR have progressed significantly, leading to suboptimal clinical outcomes after surgery.w2 w3 Accordingly, markers that could identify early structural and functional abnormalities of the LV are needed to potentially facilitate the decision for timing of surgery, thereby improving clinical outcomes. In both AS and MR, ultrastructural changes of the LV with expansion of the extracellular matrix and fibrosis formation may occur due to pressure and volume overload, respectively.w4 w5 Fibrosis causes increased LV stiffness, leading to diastolic dysfunction and subtle worsening of systolic function, whereas overt LV systolic dysfunction (reduced LVEF) will occur later in the course of AS and MR. Focal fibrosis reflects scar tissue formation by replacing dead myocardial cells with collagen, which is observed after myocardial infarction, for example. In valvular heart disease, however, pressure or volume overload predominantly cause diffuse interstitial fibrosis, a distinct type of fibrosis.w4–w6 This type of fibrosis increases the interstitial collagen without notable cell loss and therefore it may be (partially) reversible.w6 Recently, a rapid development in non-invasive imaging technology has occurred which …