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AFBAcid-fast bacillus
AIDSAcquired immunodeficiency syndrome
ALTAlanine aminotransferase
ANAAntinuclear antibody
ASTAspartate aminotransferase
CBCComplete blood cell count
CFComplement fixation
CHFCongestive heart failure
CKCreatine kinase
CNSCentral nervous system
CSFCerebrospinal fluid
CXRChest x-ray
CYPCytochrome P450
DiffDifferential cell count
EDTAEthylenediaminetetraacetic acid (edetate)
ELISAEnzyme-linked immunosorbent assay
GNRGram-negative rod
GNCBGram-negative coccobacillus
GPCGram-positive coccus
GVCBGram-variable coccobacillus
HLAHuman leukocyte antigen
INRInternational Normalized Ratio
MNMononuclear cell
MRIMagnetic resonance imaging
NPONothing by mouth (nil per os)
PCRPolymerase chain reaction
PMNPolymorphonuclear neutrophil (leukocyte)
POOrally (per os)
PTHParathyroid hormone
RBCRed blood cell
RPRRapid plasma reagin (syphilis test)
SIADHSyndrome of inappropriate antidiuretic hormone (secretion)
SLESystemic lupus erythematosus
T4Tetraiodothyronine (thyroxine)
TSHThyroid-stimulating hormone
VDRLVenereal Disease Research Laboratory (syphilis test)
WBCWhite blood cell
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How to Use This Section

This chapter includes criteria for the diagnosis of basic electrocardiographic waveforms and cardiac arrhythmias. It is intended for use as a reference and assumes a basic understanding of the electrocardiogram (ECG).

Electrocardiographic interpretation is a "stepwise" procedure, and the first steps are to study and characterize the cardiac rhythm.

Step One (Rhythm)

Categorize what you see in the 12-lead ECG or rhythm strip, using the three major parameters that allow for systematic analysis and subsequent diagnosis of the rhythm:

  1. Mean rate of the QRS complexes (slow, normal, or fast).

  2. Width of the QRS complexes (wide or narrow).

  3. Rhythmicity of the QRS complexes (characterization of spaces between QRS complexes) (regular or irregular).

Step Two (Morphology)

Step 2 consists of examining and characterizing the morphology of the cardiac waveforms.

  1. Examine for atrial abnormalities and bundle branch blocks (BBBs) (See Bundle Branch Block).

  2. Assess the QRS axis and the causes of axis deviations (See The Mean QRS Axis in the Frontal Plane (Limb Leads)).

  3. Examine for signs of left ventricular hypertrophy (See Left Ventricular Hypertrophy).

  4. Examine for signs of right ventricular hypertrophy (See Right Ventricular Hypertrophy (RVH)).

  5. Examine for signs of myocardial infarction, if present (See Myocardial Injury, Ischemia, and Infarction).

  6. Bear in mind conditions that may alter the ability of the ECG to diagnose a myocardial infarction (See Test Performance Characteristics for Electrocardiographic Criteria in the Diagnosis of Myocardial Infarction).

  7. Examine for abnormalities of the ST segment or T wave (See Tables 7–6, Table 7–7, Table 7–8, and Table 7–9).

  8. Assess the QT interval (See Prolonged QT Interval).


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