Brief Reports

Comparison of Quantitative Doppler With Magnetic Resonance Imaging for Assessment of the Severity of Mitral Regurgitation

Accurate quantification of regurgitant volume is a central component to the management of mitral regurgitation. Cardiac magnetic resonance imaging (CMR) accurately quantifies mitral regurgitation as the difference between left ventricular stroke volume and forward stroke volume using steady state free precession and phase contrast imaging. The CMR measurement of mitral regurgitant volume is reproducible and can quantify mitral regurgitation in patients without regard to regurgitant jet morphology, such as patients with multiple and eccentric jets. It can be used to quantify regurgitant volume in patients with multiple valve lesions and concomitant intracardiac shunts without the use of intravenous contrast. Studies have highlighted the accuracy and reproducibility of CMR in quantifying mitral regurgitation and have begun to link CMR to clinical outcomes.

Dilated cardiomyopathy (DCM) is defined as a disease of the myocardium characterized by left ventricular dilatation and systolic impairment that cannot be exclusively explained by abnormal loading conditions (such as hypertension or valvular heart disease) or coronary artery disease. The true prevalence is debated because of a lack of large contemporary population studies. The original Olmsted County study, performed between 1975 and 1984, estimated the prevalence to be in the region of 1 in 2700 individuals. However, the calculated prevalence of hypertrophic cardiomyopathy in the same study has since been shown to be a gross underestimate, possibly explained by the fact that echocardiography was still a developing technique. Recent reports have estimated the prevalence to be closer to 1 in 400 people in the United States. Nevertheless, DCM is a commonly encountered condition, representing the most frequent indication for cardiac transplantation and a common cause of heart failure and sudden cardiac death. Despite therapeutic advances, 3-year treated mortality rates are estimated to be 12% to 20%. Definitive early investigation giving a prompt and accurate diagnosis is therefore essential for the expedient introduction of targeted therapy. We will discuss the benefits of cardiovascular magnetic resonance in the investigation of DCM after a brief overview of our current understanding of the disease.

Mitral regurgitation (MR) is a complex valve lesion that can pose significant management challenges for the cardiovascular clinician. This Expert Consensus Document emphasizes that recognition of MR should prompt an assessment of its etiology, mechanism, and severity, as well as indications for treatment. A structured approach to evaluation based on clinical findings, precise echocardiographic imaging, and when necessary, adjunctive testing, can help clarify decision making. Treatment goals include timely intervention by an experienced heart team to prevent left ventricular dysfunction, heart failure, reduced quality of life, and premature death.

Grading of chronic aortic regurgitation (AR) and mitral regurgitation (MR) by cardiovascular magnetic resonance (CMR) is currently based on thresholds, which are neither modality nor quantification method specific. Accordingly, this study sought to identify CMR-specific and quantification method–specific thresholds for regurgitant volumes (RVols), RVol indexes, and regurgitant fractions (RFs), which denote severe chronic AR or MR with an indication for surgery. The study comprised patients with moderate and severe chronic AR (n = 38) and MR (n = 40). Echocardiography and CMR was performed at baseline and in all operated AR/MR patients (n = 23/25) 10 ± 1 months after surgery. CMR quantification of AR: direct (aortic flow) and indirect method (left ventricular stroke volume [LVSV] − pulmonary stroke volume [PuSV]); MR: 2 indirect methods (LVSV − aortic forward flow [AoFF]; mitral inflow [MiIF] − AoFF). All operated patients had severe regurgitation and benefited from surgery, indicated by a significant postsurgical reduction in end-diastolic volume index and improvement or relief of symptoms. The discriminatory ability between moderate and severe AR was strong for RVol >40 ml, RVol index >20 ml/m², and RF >30% (direct method) and RVol >62 ml, RVol index >31 ml/m², and RF >36% (LVSV-PuSV) with a negative likelihood ratio ≤ 0.2. In MR, the discriminatory ability was very strong for RVol >64 ml, RVol index >32 ml/m², and RF >41% (LVSV-AoFF) and RVol >40 ml, RVol index >20 ml/m², and RF >30% (MiIF-AoFF) with a negative likelihood ratio < 0.1. In conclusion, CMR grading of chronic AR and MR should be based on modality-specific and quantification method–specific thresholds, as they differ largely from recognized guideline criteria, to assure appropriate clinical decision-making and timing of surgery.