Preoperative liver dysfunction presents a significant risk factor for severe morbidity and mortality in the postoperative period of cardiac surgery. However, neither commonly used surgical risk assessment tools nor most registries account for it, as these scores were initially developed at a time when patients with advanced liver disease were frequently excluded from surgical treatments. With an increasingly elderly and comorbid patient population, and the rise of less invasive therapeutic options, the need to reassess surgical risks remains essential to select appropriate candidates.

The primary assessment tools for liver dysfunction include the Child-Pugh and MELD scores. The Child-Pugh score evaluates three laboratory parameters (bilirubin, albumin, and prothrombin time/INR) and two clinical features (ascites and encephalopathy) to classify liver dysfunction into three categories: Class A (well-compensated liver disease, 5–6 points), Class B (significant functional impairment, 7–9 points), and Class C (decompensated liver disease, 10–15 points). This classification provides a prognostic indicator, with a 1-year survival rate of 100% (85% at 2 years) for Class A, 80% for Class B, and 45% for Class C. The MELD score, developed later to prioritize liver transplant candidates, assesses four laboratory parameters (creatinine, bilirubin, INR, and sodium, with the latter added to refine the model as the MELD-Na score) and the need for dialysis ≥2 times per week. This scoring system predicts a 3-month mortality risk of <2%, 6%, 20%, >50%, or >70% for scores of <9, 10–19, 20–29, 30–39, and ≥40 points, respectively.

This meta-analysis included 33 studies with a total of 48,891 patients, comparing perioperative mortality and morbidity (neurological events, prolonged mechanical ventilation, bleeding and/or transfusion requirements, and acute renal failure), as well as long-term mortality, between patients scoring above and below established cutoffs: 6 points for Child-Pugh (Class A vs. B/C) and 15 points for MELD. All adverse outcomes were significantly worse for groups scoring above the cutoff (perioperative mortality HR = 3.72, neurological events HR = 1.49, prolonged ventilation HR = 2.45, bleeding HR = 1.95, acute renal failure HR = 3.84, and long-term mortality HR = 1.29).

The authors concluded that staging via these risk scores is essential in assessing patients with advanced liver disease to ensure appropriate decision-making and assign the best therapeutic options available.

COMMENTARY:

This is the most comprehensive study to date on the impact of advanced liver disease in patients undergoing cardiac surgery. Both scores have proven useful in evaluating candidates for cardiac surgery, establishing cutoffs at ≤6 points for Child-Pugh and ≤15 points for MELD.

It is logical to associate higher cardiac surgery mortality with more severe liver dysfunction, given the increased rates of preoperative morbidity and the development of postoperative complications. In a subanalysis of one study included in the meta-analysis (Gopaldas et al.), the main detrimental effect of surgery was related to the use of cardiopulmonary bypass (CPB), which increased mortality by 4.6 times compared to surgeries without CPB. This factor could open the door to considering CPB-free procedures as a preferable alternative for these patients, particularly in terms of myocardial revascularization and structural heart disease treatment (TAVI, mitral clip, percutaneous mitral prosthesis, tricuspid clip, etc.) or aortic pathologies (TEVAR). Nonetheless, this indication, based on sound clinical judgment, remains compassionate and outside clinical guidelines, as this patient profile has been systematically excluded from the evidence that currently guides these recommendations (except for the PARTNER I B study, which included patients with advanced liver disease as a reason for TAVI inoperability vs. medical treatment).

Finally, the prognostic value of liver dysfunction grading offered by these scales, beyond the mentioned cutoffs, should be considered. Scores above 9 points on the Child-Pugh scale or 20 points on the MELD scale may be deemed markers of futility, associated with nearly 50% annual mortality and thus offering no significant clinical benefit from correcting the underlying heart disease. Therefore, in the absence of liver dysfunction considerations within traditional risk scores, categorizing patients with specific scoring systems with prognostic implications becomes crucial for determining the best therapeutic management for patients with advanced liver disease.

REFERENCE:

Kirov H, Caldonazo T, Audisio K, Rahouma M, Robinson NB, Cancelli G, et al. Association of liver dysfunction with outcomes after cardiac surgery—a meta-analysis. Interact Cardiovasc Thorac Surg. 2022 Dec 8;35(6). doi: 10.1093/icvts/ivac280.