From the Guidelines
Raised Lactate Dehydrogenase (LDH) levels are more commonly associated with a mechanical aortic valve rather than cholestasis. Mechanical heart valves, including aortic valves, can cause hemolysis (destruction of red blood cells) as blood cells are damaged when passing through the valve. This hemolysis leads to the release of LDH from the damaged red blood cells into the bloodstream, resulting in elevated serum LDH levels. This is particularly notable in cases where there is paravalvular leakage or valve dysfunction. While cholestasis (impaired bile flow) can cause various laboratory abnormalities, including elevated alkaline phosphatase and bilirubin, it typically does not directly cause significant LDH elevation, as seen in studies such as 1. LDH is an intracellular enzyme found in many tissues, especially the heart, liver, red blood cells, kidneys, and skeletal muscles, and its elevation generally indicates cellular damage or destruction rather than impaired excretory function as seen in cholestasis. Some key points to consider in the diagnosis of cholestasis include:
- Elevated alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGT) levels, as noted in 1
- The use of imaging procedures, such as ultrasound or MRCP, to evaluate the biliary tree and exclude extrahepatic obstruction, as recommended in 1 However, these points do not directly relate to the elevation of LDH levels, which is more closely associated with mechanical aortic valve issues. In clinical practice, it is essential to consider the potential causes of elevated LDH levels and to evaluate patients accordingly, prioritizing the most likely cause based on the clinical presentation and laboratory findings, as suggested by the most recent and highest quality study 1.
From the Research
Conditions Associated with Raised LDH
- Mechanical Aortic Valve: Elevated plasma lactate dehydrogenase (LDH) concentration may reflect hemolysis due to mechanical heart valve dysfunction 2. Studies have shown that patients with properly working mechanical aortic valves have increased LDH levels, with values ranging from 163-374 U/l for certain valve types 2, 3.
- Cholestasis: There is no direct evidence in the provided studies to suggest that cholestasis is associated with raised LDH levels. However, it is known that LDH is elevated in various diseases, including liver disorders 4, 5, 6.
LDH Levels in Different Conditions
- Mechanical Heart Valves: LDH values > 400 U/l may indicate valvular dysfunction or leakage in patients with mechanical heart valves, excluding non-cardiac causes for hemolysis 2.
- Cancer and Infection: Very high isolated LDH levels (> 800 IU/ml) are associated with the presence of cancer, liver metastases, hematologic malignancies, and infection, and are a marker for severe prognosis and high mortality rate 6.
- Benign and Malignant Diseases: LDH level elevations are not helpful in differentiating between benign and malignant diseases, but an elevation higher than 10-fold the normal rate is a pejorative predictive criteria 5.