Chemistry
Cardiac related
Lactate Dehydrogenase isoenzyme 1 (LD1)


Topic Completed: 1 December 2010

Minor changes: 6 April 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Lactate Dehydrogenase isoenzyme 1 [title]

Larry Bernstein, M.D.
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Cite this page: Bernstein L. Lactate dehydrogenase isoenzyme 1 (LD1). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/chemistrycardiacld1.html. Accessed May 24th, 2020.
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
  • 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  • However, the use of LD1 to diagnose AMI has been largely superseded by Troponin I or T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
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