Dysrhythmias - Critical Care UPDATED
ACTUAL Exam Questions and CORRECT
Answers
P Wave
Represents time for the passage of the electrical impulse through the atrium causing atrial
depolarization (contraction). Should be upright. - CORRECT ANSWER 0.06-0.12
Disturbance in conduction within atria
PR Interval
Measured from beginning of P wave to beginning of QRS complex. Represents time taken for
impulse to spread through the atria, AV node and bundle of His, bundle branches, and Purkinje
fibers, to a point immediately preceding ventricular contraction. - CORRECT
ANSWER 0.12-0.20; 0.10 seconds is normal
Disturbance in conduction usually in AV node, bundle of His, or bundle branches but can be in
atria as well
QRS Complex
Q wave: First negative (downward) deflection after the P wave, short and narrow, not present in
several leads. - CORRECT ANSWER <0.03
MI may result in development of a pathologic Q wave that is wide ( ≥0.03 sec) and deep ( ≥25%
of the height of the R wave)
R Wave
, R wave: First positive (upward) deflection in the QRS complex. - CORRECT
ANSWER Not usually measured
tall R waves could indicate right ventricle enlargement; also the name given to a QRS complex
with an entirely positive waveform
S wave: First negative (downward) deflection after the R wave. - CORRECT
ANSWER Not usually measured
left ventricular enlargement can produce abnormally steep S wave
QRS Intervals
Measured from beginning to end of QRS complex. Represents time taken for depolarization
(contraction) of both ventricles (systole). - CORRECT ANSWER <0.12
Disturbance in conduction in bundle branches or in ventricles; greater than 0.11 is abnormal;
between 0.10 and 0.12 is an incomplete bundle branch block; >= 0.12 is a complete bundle
branch block;
low amplitude <5 mm in limb leads and <10 mm in chest leads
ST Segment
Measured from the S wave of the QRS complex to the beginning of the T wave. Represents the
time between ventricular depolarization and repolarization (diastole). Should be isoelectric (flat).
- CORRECT ANSWER 0.12
Disturbances (e.g., elevation, depression) usually caused by ischemia, injury, or infarction;
concave up elevation benign, concave down associated with injury; provides strongest evidence
for MI;
ACTUAL Exam Questions and CORRECT
Answers
P Wave
Represents time for the passage of the electrical impulse through the atrium causing atrial
depolarization (contraction). Should be upright. - CORRECT ANSWER 0.06-0.12
Disturbance in conduction within atria
PR Interval
Measured from beginning of P wave to beginning of QRS complex. Represents time taken for
impulse to spread through the atria, AV node and bundle of His, bundle branches, and Purkinje
fibers, to a point immediately preceding ventricular contraction. - CORRECT
ANSWER 0.12-0.20; 0.10 seconds is normal
Disturbance in conduction usually in AV node, bundle of His, or bundle branches but can be in
atria as well
QRS Complex
Q wave: First negative (downward) deflection after the P wave, short and narrow, not present in
several leads. - CORRECT ANSWER <0.03
MI may result in development of a pathologic Q wave that is wide ( ≥0.03 sec) and deep ( ≥25%
of the height of the R wave)
R Wave
, R wave: First positive (upward) deflection in the QRS complex. - CORRECT
ANSWER Not usually measured
tall R waves could indicate right ventricle enlargement; also the name given to a QRS complex
with an entirely positive waveform
S wave: First negative (downward) deflection after the R wave. - CORRECT
ANSWER Not usually measured
left ventricular enlargement can produce abnormally steep S wave
QRS Intervals
Measured from beginning to end of QRS complex. Represents time taken for depolarization
(contraction) of both ventricles (systole). - CORRECT ANSWER <0.12
Disturbance in conduction in bundle branches or in ventricles; greater than 0.11 is abnormal;
between 0.10 and 0.12 is an incomplete bundle branch block; >= 0.12 is a complete bundle
branch block;
low amplitude <5 mm in limb leads and <10 mm in chest leads
ST Segment
Measured from the S wave of the QRS complex to the beginning of the T wave. Represents the
time between ventricular depolarization and repolarization (diastole). Should be isoelectric (flat).
- CORRECT ANSWER 0.12
Disturbances (e.g., elevation, depression) usually caused by ischemia, injury, or infarction;
concave up elevation benign, concave down associated with injury; provides strongest evidence
for MI;
