Can TEE Predict Kidney Risk After Heart Bypass? Surprising Insights from a Multicenter Study

The Search for Early AKI Predictors in CABG

Acute kidney injury (AKI) is a common and serious complication after coronary artery bypass grafting (CABG), often leading to increased hospital stays and higher mortality. Traditional markers like serum creatinine (Scr) and urine output are delayed and influenced by many factors. This has inspired researchers to seek better intraoperative predictors. One such candidate is the respiratory variability in the inferior vena cava diameter (ΔIVC) measured via transesophageal echocardiography (TEE), which has shown promise in fluid management for ventilated patients. This prospective multicenter study published in the Annals of Cardiac Anaesthesia explores whether ΔIVC can also predict AKI after CABG.

Study Design: Rigorous Multicenter Cohort Approach

Between September 2021 and July 2022, 266 adults scheduled for elective CABG were recruited across two hospitals in Shandong, China. After exclusions, 140 patients were analyzed. Key exclusion criteria included pre-existing severe kidney disease, significant valvular disease, diabetes with complications, and contraindications to TEE. ΔIVC was measured at three critical time points during surgery, and patients were followed for AKI and major adverse cardiovascular and cerebrovascular events (MACCEs). Statistical analyses, including multivariate logistic regression, adjusted for potential confounders such as age, surgery duration, and bypass time to ensure robust results.

Major Findings: CVP, Not ΔIVC, is Linked to Postoperative AKI

1. ΔIVC Not Associated with AKI

Contrary to initial hypotheses, the study found no statistically significant association between intraoperative ΔIVC (at any measured time point) and the incidence of postoperative AKI in CABG patients.

2. Central Venous Pressure (CVP) Emerges as Key Predictor

Multivariate analysis revealed that the central venous pressure measured after sternal closure (T3) was independently associated with AKI risk. Every 1 mmHg increase in CVP raised the risk of AKI by 17%. This suggests that elevated CVP may reflect venous congestion impacting renal perfusion.

3. AKI Linked to Poorer Outcomes

Patients who developed AKI had higher rates of MACCEs and mortality within 30 days post-surgery, aligning with previous studies that highlight the severe prognosis associated with postoperative AKI.

4. Limitations and Clinical Implications

While CVP showed fair predictive ability (AUC-ROC 0.631), its specificity was low, suggesting it should not be the sole marker. The study’s observational design and reliance on serum creatinine for AKI diagnosis may have led to underestimation of AKI incidence. Importantly, the findings do not undermine the general value of TEE in cardiac care but highlight the need for further research into TEE-based predictors for AKI.

Conclusion: Rethinking Intraoperative Monitoring for AKI Prevention

This pioneering multicenter cohort study underscores that while ΔIVC via TEE is not a reliable standalone predictor for postoperative AKI in CABG patients, elevated CVP after sternal closure may serve as an early warning. These insights prompt further research into perioperative hemodynamic monitoring and the nuanced role of TEE in cardiac surgery.

Citation:

Liu B, Song X, Xu H, Zhang G, Wang H, Sun Y, et al. The relationship between intraoperative respiratory variability of the inferior vena cava diameter on transesophageal echocardiography and acute kidney injury in patients undergoing coronary artery bypass grafting surgery: A prospective multicenter cohort study. Ann Card Anaesth 2026;29:95-103.