Cardiac related
Lactate Dehydrogenase isoenzyme 1 (LD1)

Author: Larry Bernstein, M.D. (see Authors page)

Revised: 2 February 2016, last major update December 2010

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Lactate Dehydrogenase isoenzyme 1 [title]
Cite this page: Lactate dehydrogenase isoenzyme 1 (LD1). website. Accessed October 23rd, 2016.
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
  • LDH is an enzyme (EC 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
  • 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  • However, the use of LD1 to diagnose AMI has been largely superseded by Troponin I or T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

  • Patients presenting 12+ hours after the onset of chest pain or other symptoms suggestive of an acute myocardial infarction

  • The LD1 isoenzyme typically is elevated in acute renal failure and with hemolytic anemia

Reference ranges
  • Must interpret values in context of clinical findings