STS Mitral Valve Repair/Replacement (MVRR) Composite Score

Due to the complex methodology used to construct the composite measure, it is impractical to separately discuss the numerator and denominator. The following discussion describes how each domain score is calculated and how these are combined into an overall composite score.

The STS Mitral Valve Repair/Replacement (MVRR) Composite Score comprises two domains consisting of six measures:

Domain 1 – Absence of Operative Mortality
Proportion of patients (risk-adjusted) who do not experience operative mortality. Operative mortality is defined as death before hospital discharge or within 30 days of the operation.

Domain 2 – Absence of Major Morbidity
Proportion of patients (risk-adjusted) who do not experience any major morbidity. Major morbidity is defined as the occurrence of any one or more of the following major complications:
1. Prolonged ventilation
2. Deep sternal wound infection
3. Permanent stroke
4. Renal failure and
5. Reoperations for bleeding, prosthetic or native valve dysfunction, and other cardiac reasons, but not for other non-cardiac reasons.

Participants receive a score for each of the two domains, plus an overall composite score. The overall composite score was created by “rolling up” the domain scores into a single number. In addition to receiving a numeric score, participants are assigned to rating categories designated by the following:
1 star – lower-than-expected performance
2 stars – as-expected performance
3 stars – higher-than-expected performance

Patient Population: The analysis population consists of patients aged 18 years or older who undergo isolated MVRR with or without concomitant tricuspid valve repair (TVr), surgical ablation for atrial fibrillation (AF), or repair of atrial septal defect (ASD).

Time Window: 3 years

Data Completeness Requirement: Participants are excluded from the analysis if they have fewer than 36 isolated MVRR procedures in the patient population.

Estimation of Composite Scores and Star Ratings: The statistical methodology used to estimate the STS
MVRR composite score and star rating for each participant site was similar to that used for the STS isolated CABG, isolated AVR, and AVR+CABG measures. As with previous composite scores, we first translated risk-standardized event rates into risk-standardized absence of event rates so that a higher score indicated better performance. We then rescaled the morbidity and mortality domains by dividing by their respective standard deviations and then added the two domains together.