The Clinical Dilemma and Study Design
Surgeons repairing primary mitral regurgitation often face the anxious question: Will this patient's left ventricle recover, or will postoperative dysfunction develop despite successful valve repair? The research related to this was published in the Journal of the American Society of Echocardiography. Among 223 patients (median age 60 years, 21% women) with chronic primary MR undergoing mitral valve repair, researchers systematically assessed preoperative LV characteristics using both echocardiography (Echo) and cardiac magnetic resonance (CMR). The primary endpoint—postoperative LV dysfunction (LVEF <50% on follow-up Echo)—occurred in 41 patients (18%) after a median 8.7-month follow-up.
Who Got Into Trouble? Baseline Predictors
Patients developing postoperative LV dysfunction had distinct preoperative LV profiles. These patients have lower CMR LVEF (P = 0.003), larger absolute and indexed LV end-systolic diameters (LVESDs) and volumes (LVESVs) (all P ≤ 0.009), and a trend toward lower Echo LVEF (P = 0.072). 
These align with clinical intuition: patients with more advanced LV remodeling preoperatively carried a higher risk of postoperative failure despite successful valve repair.
Individual Parameters: Disappointing Discrimination
Individual Echo and CMR parameters showed only modest discriminative ability. The AUC was 0.59 (0.49-0.68) for echo LVEF, 0.66 for CMR-indLVESD, 0.65 for CMR-LVEF, and 0.70 (0.61-0.78) for indexed (ind-) LV end-systolic diameter (indLVESD). Strain imaging, whether by Echo or CMR, failed to improve risk stratification.
Echo indexed LVESD and CMR LVEF emerged as the strongest individual predictors, but AUCs in the 0.59–0.70 range underscore the limitations of single-parameter approaches for surgical timing decisions.
The 2-Step Algorithm: Risk Stratification That Works
Researchers developed a sequential 2-imaging modality approach that meaningfully separated risk. 
Step 1: Echo indLVESD
<18 mm/m²: 9% postoperative LV dysfunction risk
Step 2: For Echo indLVESD ≥18 mm/m² → CMR LVEF
CMR LVEF >56%: 20% postoperative LV dysfunction risk
CMR LVEF ≤56%: 41% postoperative LV dysfunction risk
This algorithm identified 3 clinically distinct risk tiers using complementary strengths of each modality: Echo excels at indexed linear measurements, while CMR provides superior volumetric and functional assessment.
For the Heart Team
When facing the borderline MR patient, Echo indLVESD remains the initial filter. Values <18 mm/m² predict excellent LV recovery post-repair. But ≥18 mm/m² demands CMR LVEF, separating 20% risk from 41% risk with actionable clarity.
No single parameter suffices. The Echo-CMR relay leverages each modality's strengths to deliver stratified, not binary, risk assessment—precisely what surgical timing decisions require.
Bottom line: Postoperative LV dysfunction remains unpredictable (AUCs 0.59–0.70), but this 2-step approach meaningfully separates surgical candidates into 9% vs 20% vs 41% risk groups, guiding shared decision-making when guidelines leave gray zones.