CV - introduction to the ECG Flashcards
the ____________ node is the pacemaker of the heart.
sinoatrial (SA)
electrical impulses initiated by the sinoatrial node proceed through ____________ which activate a wave of ____________ in the atrium that converges on the ____________ node.
internodal tracts
depolarization
atrioventricular (AV)
there is a brief delay at the atrioventricular node, after which the impulses rapidly flow through the ____________ and activate the ventricles through the ____________.
bundle of his
right and left bundles
after traveling through the right and left bundles, the impulses then diverge into ____________ which activate ____________ and ____________.
purkinje fibers
ventricular myocardial cell depolarization
contraction
the initial deflection is the ____________ wave.
P
the P wave is due to ____________.
atrial depolarization
the deflection following the P wave is the ____________.
QRS
the QRS is due to ____________.
ventricular depolarization
the Q is ____________, the R is ____________ and the S is a ____________ deflection.
negative
positive
late negative
the normal duration of the QRS is ____________ seconds.
0.06 to 0.10
the ____________ wave is the deflection following QRS.
T wave
the T wave is due to ____________.
ventricular repolarization
a normal PR interval is ____________ seconds.
0.12 to 0.20
the QT interval represents ____________.
the total duration of depolarization and repolarization
unipolar leads measure the difference in electrical potential between ____________ and ____________.
a point on the body
virtual reference point with zero electrical potential located in the center of the heart
bipolar leads measure the difference in electrical potential between ____________.
two different points on the body
depolarization moving towards a limb lead will produce a ____________ deflection.
positive
define ischemia
ischemia occurs when blood supply is insufficient to meet the oxygen demand in the ventricles
ischemic changes in the EKG alter ____________ and affect the ____________ and ____________ wave.
ventricular repolarization
ST segment
T
ischemia due to sudden high oxygen demand in the presence of fixed coronary obstruction causes ____________ of the ST segment.
depression
typically, T waves and Q waves go in the ____________ direction.
same
an inverted T wave is a sign of ____________.
ischemia
ST ____________ is a sign of transmural injury in an acute pericarditis or acute coronary syndrome, usually with a clot due to platelet aggregation obstructing a coronary artery.
elevation
Q waves in inferior leads (II, III aVF) are due to ____________.
inferior infarcts
Q waves in leads V1-V4 are due to ____________.
anterior wall infarcts
Q waves in leads I, aVL and the anterolateral leads (V5, V6) are associated with ____________.
lateral wall infarcts