1. In this retrospective cohort study, the degree of symptom burden correlated well with left ventricular end systolic volume index as assessed by cardiac magnetic resonance imaging.
2. Used in this setting, cardiac magnetic resonance imaging could help identify patients at risk of heart failure or death and assist in clinical decision-making.
Level of Evidence Rating: 2 (Good)
Study Rundown: Chronic aortic regurgitation (AR) leads to pressure and volume overload on the left ventricle (LV) and can lead to ventricular remodeling over time. Greater LV volume is associated with dysfunction and should therefore be quantified to understand disease course and prognosis. However, assessing LV volume with transthoracic echocardiography (TTE) alone can be challenging. This study sought to describe the accuracy and clinical utility of cardiac magnetic resonance (CMR) in assessing LV volume and function in patients with chronic AR.
178 patients were included, of whom 158 (89%) had minimal or no symptoms of aortic regurgitation at baseline. Assessment by TTE found that approximately half (54%) of all patients had moderate AR and that the remainder had moderate-severe AR. The measure of LV size was not found to correspond functionally with the New York Heart Association (NYHA) measures of heart failure severity (I and II versus more severe III and IV grades). In contrast, CMR observed ventricular remodeling which was more severe in NYHA class III and IV heart failure patients compared to class I and II. Patients who experienced death or heart failure (new or exacerbated) in the follow up period were found to have greater left ventricular end systolic volume index (LVESVi) scores at baseline as assessed by CMR compared to patients who did not experience the primary outcome.
This retrospective cohort study found that LVESVi accurately predicted symptomatic progression of aortic regurgitation in patients with minimal symptoms at baseline. This work describes the many advantages and clinical indications for performing CMR in addition to TTE in assessing ventricular remodeling in patients with valvular disease. A limitation of the study was that the sample was highly selective, potentially reflecting some referral and inclusion bias. As well, imaging data from a single time point was extrapolated across a 3-year follow up period; future studies should address changes in LV structure and function with repeat imaging studies longitudinally.
In Depth [retrospective cohort study]: A multicenter retrospective cohort study was performed in the United States. Adults with moderate or severe AR who received CMR within 90 days of diagnosis were eligible for inclusion. Patients who had acute aortic dissection, cardiomyopathy, previous valve replacement, severe concomitant valvular disease, or poor image quality for echocardiography or CMR were excluded.
TTE findings described 54% of patients as having moderate AR and 46% having moderate-severe AR. Other valvular lesions identified by TTE were aortic stenosis (9%), mitral regurgitation (10%) and tricuspid regurgitation (8%). The mean LVESVi in patients who experienced death, new or exacerbated heart failure during follow up was 57 ml/m2 (standard deviation, 43); in patients who did not experience the primary outcome the mean LVESVi was 45 ml/m2 (24). Median LVSEVi as assessed by TTE was 27 ml/m2 (interquartile range 20-42) in baseline NYHA class I and II patients and 38 (30-58) ml/m2 in NYHA III and IV patients; a non-statistically significant difference (p= 007). In contrast, the same parameter assessed by CMR found a significant difference between low and high NYHA grades: 42 (30-58) ml/m2 versus 66 (46-85) ml/m2 (p < 0.001).
TTE was also found to underestimate forward stroke volume index and cardiac index in comparison with CMR. Amongst the 158 patients who had no, or minimal symptoms at baseline, 31% went on to undergo aortic valve replacement in the subsequent 3-year follow up and 31.6% of the medically managed patients experienced the composite primary outcome (death, heart failure, worsening symptoms). The hazard ratio for experiencing this composite outcome in patients with LVESVi greater than the cutoff point of 45 ml/m2 was 2.28 (95% confidence interval 1.30-4.00).
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