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Predicting Survival in Patients Receiving Continuous Flow Left Ventricular Assist Devices: The HeartMate II Risk Score
Study Questions:
What is the utility and validity of a derived model to predict survival in candidates for HeartMate II (HMII) left ventricular assist device (LVAD) support?
Methods:
Patients enrolled into the HMII bridge to transplantation and destination therapy trials (N = 1,122) were randomly divided into derivation (DC) (n = 583) and validation cohorts (VC) (n = 539). Preoperative candidate predictors of 90-day mortality were examined in the DC with logistic regression, from which the HMII Risk Score (HMRS) was derived. The HMRS was then applied to the VC.
Results:
There were 149 (13%) deaths within 90 days. In the DC, mortality (n = 80) was higher in older patients (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.1-1.7 per 10 years), those with greater hypoalbuminemia (OR, 0.49; 95% CI, 0.31-0.76 per mg/dl of albumin), renal dysfunction (OR, 2.1; 95% CI, 1.4-3.2 per mg/dl creatinine), coagulopathy (OR, 3.1; 95% CI, 1.7-5.8 per international normalized ratio [INR] unit), and in those receiving LVAD support at less experienced centers (OR, 2.2; 95% CI, 1.2-4.4 for <15 trial patients). Mortality in the DC low, medium, and high HMRS groups was 4%, 16%, and 29%, respectively (p < 0.001). In the VC, corresponding mortality was 8%, 11%, and 25%, respectively (p < 0.001). HMRS discrimination was good (area under the receiver-operating characteristic curve, 0.71; 95% CI, 0.66-0.75).
Conclusions:
The authors concluded that the HMRS might be useful for mortality risk stratification in HMII candidates, and may serve as an additional tool in the patient selection process.
Perspective:
The authors developed and prospectively validated a model for assessing patient risk in the era of continuous flow LVAD support using a large multicenter clinical trial data set. The HMRS components—age, serum albumin, creatinine, INR, and implant center LVAD experience—highlight important preoperative determinants of survival after LVAD implantation. The risk score may be useful for patient, family, and referring provider education, providing patient-level LVAD mortality risk assessment regardless of bridge to transplantation or destination therapy indication. Furthermore, the HMRS also identifies important preoperative risk factors that may be targets for interventions to improve LVAD candidate survival.
Keywords: Odds Ratio, Heart-Assist Devices, Hypoalbuminemia, Creatinine, Blood Coagulation Disorders, Heart Transplantation, Heart Diseases, International Normalized Ratio, Serum Albumin, Heart Failure, ROC Curve, Confidence Intervals, Risk Assessment, Logistic Models
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