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Cardiac Biomarkers

Key Points

• Circulating cardiac biomarkers, biologic substances that are associated with cardiac stress, have growing clinical importance in
human and veterinary cardiology.
• There are currently feline assays for NT-proBNP and cardiac troponin I (cTnI) on the market, with published normal ranges.
• There are two point-of-care (cage-side) assays available for cTnI but the natriuretic peptides are not available as cage-side
tests.
• Biomarkers cannot replace echocardiography for diagnosing the presence and type of heart disease in an individual patient.
However, they can be useful tools in certain subsets of patients. For example, biomarker results can help differentiate between
primary respiratory vs primary cardiac disease in the critical, dyspneic feline patient.
• There is currently no evidence to support the use of any of these tests for screening clinically normal patients for heart disease.

INTRODUCTION cellular matrix remodeling, neurohormones, myocyte
injury and myocyte stress (Braunwald 2008).
The National Institutes of Health (NIH) has defined a Numerous circulating biomarkers (enzymes, hor-
biomarker as “a characteristic that is objectively mea- mones, and biologic substances) appear to have clinical
sured and evaluated as an indicator of normal biologic importance in human heart disease and failure. However,
processes, pathogenic processes or pharmacologic there have been few studies performed in cats. This dis-
responses to a therapeutic intervention.” This broad cussion will focus on those circulating biomarkers that
definition essentially allows the term to be used for a have been evaluated in the feline species. There are
wide range of measureable indexes in medicine: from several excellent reviews of biomarkers in human and
radiographic heart size to arrhythmia detection on an veterinary patients and the interested reader is referred
electrocardiogram. However, the term has gradually to them for further reading on the topic (Braunwald
evolved to be used most frequently to describe circulat- 2008; Boswood 2009).
ing biomarkers, most often those substances involved in
the neurohormonal response to heart failure or those HOMOCYST(E)INE AND B VITAMINS
substances released from myocardial tissue in response
to injury. Although many of these biomarkers are rou- In humans, high plasma homocysteine and low B vitamin
tinely used in human cardiovascular medicine, they are levels are risk factors for various vascular diseases.
only beginning to be characterized in the veterinary McMichael et al. (2000) evaluated circulating homocys-
species. However, the area is attracting a great deal of teine, B vitamins and amino acid concentrations in
work and results are encouraging that biomarkers will cats with cardiomyopathy and ATE. This group showed
ultimately play an important role in veterinary cardiol- that arginine concentrations were lower in cardiomyop-
ogy as well. Six main categories have been proposed to athic cats with ATE compared to cardiomyopathic cats
describe the various potential circulating biomarkers in without ATE and a group of healthy controls. In addi-
human medicine: inflammation, oxidative stress, extra- tion, both heart disease groups had lower plasma B 6 and

Feline Cardiology, First Edition. Etienne Côté, Kristin A. MacDonald, Kathryn M. Meurs, Meg M. Sleeper.
© 2011 John Wiley & Sons, Inc. Published 2011 by John Wiley & Sons, Inc.

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