New Frontiers in Aortic Regurgitation Disease Management

AR can be categorized into acute and chronic. Acute AR entails a quick and sudden volume overload of the left ventricle whereas chronic AR entails a gradual overload. The primary diagnostic tool to evaluate AR is transthoracic echocardiography which sheds light on the type and degree of valve dysfunction and the hemodynamic burden induced by the valve defect. Echocardiography — which uses high-frequency sound waves to take images of the heart — can also provide information on the progressive increase in LV volumes. Other diagnostic tools include chest X-rays, CMR and coronary angiograms. However, an accurate evaluation of AR is dependent on a thorough understanding of the mechanism of AR, which requires understanding the valve morphology as well as measurements of different segments of the aorta.

Quantifying AR severity has been clinically challenging. Typically, echocardiography is used in combination with CMR to gain a composite understanding of AR severity. Moreover, guidelines from the American College of Cardiology and the American Heart Association suggest CMR usage when echocardiography results are inconclusive. CMR imaging is a reproducible and non-invasive technology that is the gold standard for assessing LV volume, LVEF and mass. Since quantitative CMR studies in AR are few, Malahfji set out to investigate the association of CMR quantitative thresholds and outcomes in asymptomatic AR patients with preserved LVEF (LVEF greater than or equal to 50%). According to Malahfji, “In this multicenter study of asymptomatic AR patients with preserved left ventricular systolic function, we identified quantitative CMR parameters associated with clinical outcomes that can guide clinical management decisions. These results support the incorporation of left ventricular volumes rather than left ventricular diameters in the evaluation and management of patients with moderate to severe AR.” Malahfji and his team studied 458 patients with moderate or severe AR as a part of a multicenter study of four U.S. prospective institutional registries. The median age of these patients was 60, and the median follow-up period was 2.4 years. The primary outcome was the development of symptoms, LVEF depreciation to less than or equal to 50%, indications for surgery or death. The secondary outcome was the same except for surgery. Based on multivariate regression analysis and receiver operating characteristic analysis, Malahfji concluded that CMR parameters associated with clinical outcomes can guide decision-making in AR management. Furthermore, Malahfji noted that LV volume measurements are more beneficial as compared to LV diameters. Improved decision-making can reduce morbidity and mortality, especially since surgery at earlier time points is likely to improve AR outcomes. The study, led by Malahfji, aimed to address knowledge gaps in the field of AR management in three key aspects. First, it provides a better understanding of the relationship between LV volumes and AR outcomes. Second, it provides data sets for AR prognostic analysis from a large sample size. Thirdly, it recommends using CMR LV volume assessments for clinical decisions in AR management. This is particularly valuable since LV end-systolic diameter measurements can vary based on the technique used. The main limitation of this study is a potential selection bias since the patients were referred for advanced imaging beyond echocardiography. Further studies are warranted to evaluate the diagnostic accuracy of CMR. Multiparametric and multi-imaging approaches can be implemented in concert to gather data sets for optimizing diagnosis, monitoring prognosis and accurate decision-making in AR management.