C-Reactive Protein to Albumin Ratio offers superior risk prediction in patients undergoing mitral valve edge-to-edge repair: a comparison to established surgical risk scores
Authors: Koell B , Ludwig S , Weimann J , Waldschmidt L , Schirmer J , Reichenspurner H , Blankenberg S , Conradi L , Schofer N , Kalbacher D 
Published: October 2022

Abstract

Background
The population of patients with relevant mitral regurgitation (MR) who stand to gain optimal benefit from mitral valve transcatheter edge-to-edge repair (TEER) remains to be determined. Prior to TEER, a heart-team approach with interdisciplinary decision-making is mandatory integrating both the patient profile and relevant co-morbidities. In addition, the application of established surgical risk scores is recommended by current guidelines. Whether alternative risk prediction is more suitable for this fragile patient cohort burdened with various co-morbidities has not been examined in detail. A simplified approach may be achieved by using the C-Reactive Protein to Albumin Ratio (CAR), but its value in TEER is unclear.

Methods
This single-center, retrospective study thought to determine long-term prognostic accuracy of different risk scores in patients with relevant MR undergoing TEER. For this analysis, 316 patients with a median follow-up time of 5.81 years were included. The primary outcome measure was defined as all-cause mortality. ROC analysis was conducted for the identification of the optimal CAR threshold, subsequently dichotomizing patients into two groups (CAR ≤0.4 and CAR &gt;0.4) estimating their long-term event rate using the Kaplan-Meier method. In addition, we evaluated the prognostic value of CAR compared to two conventional surgical risk scores (logistic EuroSCORE and Society of Thoracic Surgeons [STS] risk score) using C-Index analysis.

Results
Among 316 high-risk patients undergoing TEER (mean age 75.6±8.2 years, 61.7% male, median logistic EuroSCORE 19.9% [11.7; 31.6], median STS Score 3.8% [2.2; 5.7]), 176 (55.7%) patients had a CAR value ≤0.4. Patients with an elevated CAR (&gt;0.4) predominantly suffered from a higher burden of co-morbidities, such as peripheral artery disease (p=0.001), chronic obstructive pulmonary disease (p=0.044), and chronic kidney disease (p=0.015). Consequently, these patients had significantly higher logistic EuroSCORE and STS Score than patients with CAR ≤0.4 (logistic EuroSCORE p=0.002; STS Score p&lt;0.001). Stratification according to the CAR threshold of 0.4 led to significant differences in the Cumulative Incidence curves (p&lt;0.001). In addition, log-rank test revealed a superior risk stratification of the simplified CAR approach compared to established surgical risk scores (Figure 1). This effect consequently reflects in a higher adjusted C-Index for CAR (0.608) compared to logistic EuroSCORE (0.502; p&lt;0.001) and STS Score (0.498; p&lt;0.001).

Conclusions
Our data provide first evidence that alternative risk prediction using CAR allows for a feasible and easy-to-use risk prediction in a real-word TEER cohort presenting with advanced age, a high proportion of frailty and numerous co-morbidities. Alternative risk prediction in TEER patients should be investigated in more detail as the established surgical risk scores seem to demonstrate limited applicability in patients scheduled for TEER.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): University Medical Center Hamburg-Eppendorf, Hamburg, Germany