Predictive Value of the Transthoracic Echocardiography Index for Acute Kidney Injury after Cardiac Valve Surgery

Abstract

Background: We aimed to demonstrate whether the preoperative transthoracic echocardiography index (TTEI) could improve the predictive value of clinical parameters for cardiac valve surgery-associated acute kidney injury (CVS−AKI). Methods: A total of 213 patients who underwent surgical CVS at Renmin Hospital of Wuhan University were consecutively recruited in this retrospective study. TTE assessments were performed within 7 days before surgery and logistic regression was used to determine TTEI. A nomogram was constructed by integrating TTEI and clinical features, and the net reclassification index (NRI) and integrated discrimination improvement (IDI) were applied to evaluate the improvement in TTEI for CVS−AKI. Results: Among them, 66 patients (30.9%) developed CVS−AKI. The TTEI was calculated as follows: −6.579 + 0.068 × pulmonary artery systolic pressure (mmHg) −0.742 × LVEF (>55%, yes or no) + 0.346 × left ventricle posterior wall thickness (mm). The nomogram based on the TEEI and other clinical factors possessed excellent performance (C-index = 0.880), had great calibration and discrimination, and was clinically useful. Furthermore, NRI (0.07, 95% confidence interval, 95%CI, 0.01−0.12, p = 0.02) and IDI (0.08, 95%CI, 0.01−0.20, p = 0.02) indicated that TTEI could significantly improve the predictive value of clinical features for CVS−AKI. Conclusions: As a simple access and cost-effective parameter, the preoperative TTEI may be a reliable and useful factor for CVS−AKI.

Keywords: acute kidney injury; cardiac valve surgery; nomogram; risk assessment; transthoracic echocardiography index.

Figure 1

The flow chart of this study.

Figure 2

Representation of measured values based on echocardiographic views. (A) The measurements of the left atrial in parasternal left ventricular long axis (PLAX) view. (B) The measurements of the interventricular septum (IVS), left ventricular posterior wall (LVPW), and left ventricular end-diastolic diameter (LVEDD) in PLAX view. (C) Measurement of the mitral valve area in a patient with rheumatic heart disease; the mitral valve area was manually outlined and the mitral valve area is 0.89 cm². (D) The aortic valve area was calculated using continuity equations, and the effective valvar orifice area (EOA) of the aortic valve is 0.23 cm². (E) A continuous wave Doppler was used to measuring the end-expiration peak velocity of the tricuspid regurgitant (TR) jet. (F) The IVC size was measured in M-mode at the subcostal window. The IVC—CI (inferior vena cava collapsibility index) was calculated as follows: IVC-CI = [(IVC diameter in expiration—ICV diameter in inspiration)/ (IVC diameter in expiration)] × 100. Right atrial pressure (RAP) was estimated from the IVC-CI. (G) Quantitative assessment of aortic regurgitation using the proximal isovelosity surface area method (PISA). The effective regurgitant orifice area (EROA) is 0.33 cm² and the regurgitant volume (RV) is 100 mL. (H) Quantitative assessment of mitral regurgitation by PISA. The EROA is 0.25 cm² and the RV is 61 mL.

Figure 3

(A) The waterfall plot of TTEI value for each patient and (B) the relationship between TTEI and other TTE parameters and clinical features. * p < 0.05, ** p < 0.01, *** p <0.001.

Figure 4

The forest plot revealed the results of subgroup analysis for CVS−AKI based on low and high TTEI groups in the crude cohort.

Figure 5

Selection of significant factors associated with CVS−AKI by LASSO logistic regression model. (A) Identification of tuning parameter (λ) in the LASSO model. (B) Profiles of LASSO coefficient for clinical features.

Figure 6

The predictive nomogram for CVS−AKI.

Figure 7

Calibration and clinical utility of the predictive nomogram. (A) The predictive nomogram exhibited a high correlation between the actual probability and predicted probability for CVS−AKI. (B) Decision curve analysis for the predictive nomogram to predict CVS−AKI in this study.