By Michael H. Crawford, MD, Editor

SYNOPSIS: An international database of patients with significant degenerative mitral valve regurgitation (MR) was used to derive and test a score using clinical and echocardiographic data to estimate mortality with medical and surgical therapy. From seven weighted characteristics, investigators developed a 0-12 score that predicted medical and surgical long-term mortality with high discriminatory ability (C-statistic, 0.78 and 0.81, respectively). Investigators found the score added incremental information to surgical scores and believe that it will be useful for therapeutic decision-making.

SOURCES: Grigioni F, Clavel MA, Vanoverschelde JL, et al. The MIDA mortality risk score: Development and external validation of a prognostic model for early and late death in degenerative mitral regurgitation. Eur Heart J 2018;39:1281-1291.

Vahanian A, Iung B. Predicting the outcome of degenerative mitral regurgitation: A step forward but still a long way to go! Eur Heart J 2018;39:1292-1294.

Mitral valve regurgitation (MR) is the most frequent valve disease. Degeneration often with prolapse is the most common cause of MR. Although surgical risk scores exist, there is no non-surgical, long-term mortality score to help guide clinicians. Accordingly, investigators sought to develop and validate such a score from a large international degenerative MR database (MIDA). Prognostic markers from clinical data and echocardiography were selected from current guidelines and assessed in the derivation cohort (2,472 patients with a flail leaflet), which established the weight of each marker. The resulting MIDA score was tested for predictive ability for one year mortality, regardless if the patient underwent subsequent surgery. The MIDA score was validated in the MIDA-BNP registry (1,194 patients with flail or prolapsed leaflets) over a 10-year follow-up. Since the results of the two cohorts were analogous in the prognostic ability of the MIDA score, they were combined (n = 3666) for a more robust analysis. The weighted markers were age > 65 years (3 points), symptoms (3 points), right ventricular systolic pressure > 50 mmHg (2 points), atrial fibrillation (1 point), left atrial diameter > 5.5 cm (1 point), left ventricular (LV) end-systolic diameter > 4.0 cm (1 point), and LV ejection fraction (EF) < 60% (1 point), for a total possible score of 0-12. After a mean eight-year follow-up, 1,151 of the 3,666 patients died. Overall survival was 84% at five years and 69% at 10 years. During a mean medical follow-up of two years, 521 patients died. Eventually, surgery was performed in 2,659 patients (90% repair); 630 died during follow-up. The MIDA score accurately predicted mortality in both medical and surgical patients (see Table) and added incremental value to surgical scores such as the EuroScore II. The authors concluded that the MIDA score may represent an innovative tool to help manage degenerative MR patients, whether they are under medical or surgical care.

COMMENTARY

As soon as a patient with significant degenerative MR becomes symptomatic or develops one other criteria for mitral valve surgery, a surgical risk score is deployed, and decisions about surgery are made. This biases surgical therapy toward lower-risk patients, which many studies have demonstrated. Part of the problem is the lack of a good estimator of mortality on medical therapy; hence, the impetus for the development of the MIDA score, the use of which may help prevent leaving high-risk patients on medical therapy. This is especially important today because we have minimally invasive surgery and percutaneous approaches to mitral valve repair. The MIDA score robustly predicted early and late mortality in medical and surgical patients with good discrimination (C-statistic, 0.78 and 0.81, respectively). Thus, the authors thought it could be a useful tool for decision-making in patients with significant MR.

The strengths of this study were that it is the largest study of degenerative MR to date, with more than 3,000 patients; it included clinical and echo parameters and is of incremental value over surgical scores. However, there were some weaknesses. There was a selection bias toward severe MR patients, but with low surgical risk (mean EuroScore, 1.2). The precise grading of MR was not specified, but was a combination of measures. Patients undergoing percutaneous repair were underrepresented, and comorbidities were not considered. Consequently, Vahanian and Iung concluded in an accompanying editorial that one could not use this score alone to make decisions; rather, one must consider all available data and make a reasoned clinical judgment. They emphasized that directing the Heart Team to evaluate the patient, as recommended by the European Society of Cardiology Guidelines (2017), is the best approach. However, I don’t think committees should make clinical decisions, but rather help inform the patients and their doctors’ decisions. In this context, the MIDA score will be a useful adjunct to decision-making in degenerative MR patients.

Table. One-year Medical and Surgical Mortality vs. Five-year Medical and Surgical Survival

MIDA Score

One-year Mortality Medical %

One-year Mortality Surgical %

Five-year
Survival
Medical %

Five-year
Survival
Surgical %

0

0.4

1.0

98

99

7-8

17

7

57

82

11-12

48

14

21

57