Chemistry, toxicology & urinalysis
Organ specific
Cardiac
LD1-Lactate dehydrogenase isoenzyme 1
Author: Larry Bernstein, M.D.
Last author update: 1 December 2010
Last staff update: 27 June 2020
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Lactate Dehydrogenase isoenzyme 1 [title]
Cite this page: Bernstein L. LD1-Lactate dehydrogenase isoenzyme 1. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/chemistrycardiacld1.html. Accessed April 25th, 2024.
Definition / general
- LDH measures the amount of serum lactate dehydrogenase (LDH), which is released into the circulation with an acute myocardial infarction (AMI) due to tissue damage
- LDH is elevated on the second day after chest pain and remains elevated for up to 4 days
- LD1 is the heart specific form of the enzyme present in AMI between 12 and 24 hours after onset of chest pain
Pathophysiology
- LDH is an enzyme (EC 1.1.1.27) ubiquitous in tissue
- It has five isoenzymes, each with a different composition of M-type and H-type subunits in a tetrameric structure
- LD1 (HHHH) is present in cardiac muscle and erythrocytes
Laboratory
Methodology
Indications
Limitations
Reference ranges
- LD2 is usually the predominant form in serum
- In acute myocardial infarction, the serum levels of LD1 are greater than LD2 (a "flipped pattern")
- However, the use of LD1 to diagnose AMI has been largely superseded by Troponin I or T
- The isoenzyme 1 of LD is measured by immunoprecitation of LD 2-5 and measuring the residual activity
- Also by electrophoresis and staining of agarose media
Indications
- Patients presenting 12+ hours after the onset of chest pain or other symptoms suggestive of an acute myocardial infarction
Limitations
- The LD1 isoenzyme typically is elevated in acute renal failure and with hemolytic anemia
Reference ranges
- Must interpret values in context of clinical findings
