Researchers have devised a new simple score to predict mortality following mitral transcatheter edge-to-edge repair (TEER).¹

For this study published in the Journal of American College of Cardiology, data was obtained from the retrospective multinational Percutaneous Mitral Valve Repair and Nutritional Status Registry (MIVNUT) of 1119 patients referred for TEER between 2012 and 2020 in Europe and Canada. The research objective was to create and validate a user-friendly score, “MitraScore” to predict the risk of mortality in patients undergoing TEER. Data from patients undergoing TEER between 2016 and 2020 in the prospective Italian Society of Interventional Cardiology Registry of Transcatheter Treatment of Mitral Valve Regurgitation (GIOTTO) was used to validate the proposed score.

The MitraScore was developed using data from 1119 patients in MIVNUT and it was validated in 725 patients in the GIOTTO registry. Nearly 32% deaths occurred during follow up (median 1.6 years) and 28% patients required rehospitalization.

Thirty-three variables related to lab investigations, drugs, comorbidities and echocardiography reports were analysed to formulate the risk score. Ultimately eight variables were found to be independent predictors of mortality after the multivariate analysis. These factors were:

1. Age ≥75 years
2. Anemia
3. Estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2
4. Left ventricular ejection fraction (LVEF) <40%
5. Peripheral artery disease
6. Chronic obstructive pulmonary disease
7. High dose diuretic (≥80 mg furosemide/day or use of ≥2 diuretic agents excluding antialdosteronic drugs)
8. No therapy with renin-angiotensin system (RAS) inhibitors 

Each risk factor was assigned one point. The score was calculated by “simple arithmetic sum of the number of risk variables”.

With every point of the score, the relative risk for all-cause mortality increased by 55% with a hazard ratio (HR) of 1.55. The discrimination ability of the score for mortality was modest in the derivation group (c-statistic 0.70) as well in the validation cohort (c-statistic 0.66). But, according to the study authors, this was “better than those of EuroSCORE II (c-statistic 0.61) or Society of Thoracic Surgeons score (c-statistic 0.57)”.

Based on the MitraScore, patients were risk stratified into low (≤25th percentile), moderate-risk (25-75th percentile) and high-risk (≥75th percentile). “As the MitraScore risk groups progressed from low to high, the risk for death and/or heart failure hospitalization increased from a hazard ratio of 1.97 for moderate risk to 3.69 for high risk in the derivation cohort and from 2.48 to 4.44, respectively, in the validation cohort.”

The present study has demonstrated that the MitraScore can come to the aid of the treating physician as a handy tool for early identification of patients treated with TEER at high-risk of mortality during the follow-up period.

In an accompanying editorial commentary on this research, Mohamad Alkhouli et al have critically analysed the performance of the score, accuracy of the score vis a vis the simplicity of calculation and also its practical utility as a risk prediction tool.2 They have identified lack of some clinical data such as frailty, procedure-related factors as a limitation of the study.  But, though the MitraScore is only mildly predictive, they do point out that it is comparable to other scores like the CHA2DS2-VASc (c-statistic of 0.61), ABC score (c-statistic of 0.68).

The advantage of the MitraScore is that it is simple to calculate with easily available parameters and is therefore user-friendly. But they write, “with the availability of advanced statistics and the rise of artificial intelligence research and applications, should we not be aiming at more (not less) intricate risk schemes that incorporate imaging, laboratory, and clinical data to allow more precise risk estimation?”. There is no right answer to this dilemma because technology cannot totally replace good clinical acumen. Hence, they also acknowledge that “MitraScore represents a momentous step towards improving the triaging of patients referred for TEER”.

References

1. Raposeiras-Roubin S, et al. A score to assess mortality after percutaneous mitral valve repair. J Am Coll Cardiol. 2022;79(6):562-573, https://doi.org/10.1016/j.jacc.2021.11.041.
2. Alkhouli M, et al. Risk stratification of patients undergoing mitral TEER. J Am Coll Cardiol. 2022 Feb;79(6) 574–576.