EKGS.
Perfect Prep for Every Paper | Precision in Every Answer!
Sensitivity/ specificity of ekgs - Answer: •sensitivity (true positive) of 68% for diagnosing
STEMI
•specificity (true negative) of 97% for diagnosing STEMI
Unipolar leads - Answer: •Single conductor lead with an electrode located at the tip
•Electrode potential between electrode and physical or virtual ground
Bipolar leads - Answer: •Two separate and isolated conductors within a single-lead
•Electrode potential between two electrodes---one at the lead tip, one ~2cm proximal
Standard limb leads
3-electrode system - Answer: •RA: right arm
•LA: left arm
•LL: left leg
•Best results—place electrodes on the chest wall equidistant from the heart (rather than
specific limbs)
5-electrode system - Answer: •Uses 5-electrodes
•RA: right arm
•RL: right leg
•LA: left arm
•LL: left leg
•Chest
•Monitor displays the bipolar leads (I, II, and III)
•Single unipolar lead (depending on position of the brown chest lead (V1-V6) )
Precordial Leads - Answer: •Six leads numbered V1-V6
1
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,•V1: 4th ICS, right of sternum
•V2: 4th ICS, left of sternum
•V3: midpoint of V2 and V4
•V4: 5th ICS, midclavicular
•V5: 5th ICS, anterior axillary line
•V6: 5th ICS, midaxillary line
•Positioned in successive steps from the patient's right to left chest
•Positive electrodes in all chest leads (AV node in the center)
12-lead EKG - Answer: •10 electrodes
•4 on all 4 limbs (RA, LL, LA, RL)
•6 on precordium (V1-V6)
•Allows interpretation of specific areas of the heart
•Inferior (II, III, avf)
•Lateral (I, avl, V5, V6)
•Anterior (V1-4)
Posterior Leads - Answer: •3 leads to assess posterior cardiac activity
•V7, V8, V9 all in the same horizontal plan as V6
•V7: left posterior axillary line
•V8: tip of the left scapula
•V9: left paraspinal
Intrinsic pacemaker (SA node) - Answer: •Generates spontaneous action potentials
•Atrial pulse is transmitted to the ventricles by the AV system - Answer: •AV node
•Bundle of His
•Purkinje fibers
2
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, SA node: - Answer: •sinoatrial node. Medial to opening of superior vena cava.
Comprised of highly specialized cardiac muscle cells.
•Generate spontaneous action potentials—automaticity
Atrial myocardium: - Answer: •clusters of atrial myocardial cells around the crista
terminalis—entrance of the coronary sinus and inferior vena cava, as well as cells
around the mitral and tricuspid valves
•Not conduction cells, but contractile cells that possess automaticity
AV node: - Answer: •atrioventricular node. Medial to the right atrioventricular valve.
•Action potentials conducted by cell clusters surrounding the AV node.
Ensures ventricles receive signal to contract after atria have contracted
Purkinje fibers - Answer: •Large diameter cardiac muscle cells with few myofibrils. Many
gap junctions. Conduct action potential to ventricular muscle cells
•Bundle of His and entire Purkinje network possess automaticity
Intrinsic heart rate (IHR) refers to - Answer: the inherent rate at which the heart beats
without any external influences, such as the autonomic nervous system or hormones
Action potential = - Answer: •Depolarization (activation) followed by repolarization
(recovery)
Leakage of Na+ during the resting phase is the - Answer: pacemaker potential
Contractile cardiac cells have a resting potential (unlike SA node) which - Answer:
requires activation
If positive ions surrounding the cell membrane directly match the number and alignment
of negative ions inside the cell membrane, the resting cell is - Answer: polarized
3
APPHIA - Crafted with Care and Precision for Academic Excellence.
Perfect Prep for Every Paper | Precision in Every Answer!
Sensitivity/ specificity of ekgs - Answer: •sensitivity (true positive) of 68% for diagnosing
STEMI
•specificity (true negative) of 97% for diagnosing STEMI
Unipolar leads - Answer: •Single conductor lead with an electrode located at the tip
•Electrode potential between electrode and physical or virtual ground
Bipolar leads - Answer: •Two separate and isolated conductors within a single-lead
•Electrode potential between two electrodes---one at the lead tip, one ~2cm proximal
Standard limb leads
3-electrode system - Answer: •RA: right arm
•LA: left arm
•LL: left leg
•Best results—place electrodes on the chest wall equidistant from the heart (rather than
specific limbs)
5-electrode system - Answer: •Uses 5-electrodes
•RA: right arm
•RL: right leg
•LA: left arm
•LL: left leg
•Chest
•Monitor displays the bipolar leads (I, II, and III)
•Single unipolar lead (depending on position of the brown chest lead (V1-V6) )
Precordial Leads - Answer: •Six leads numbered V1-V6
1
APPHIA - Crafted with Care and Precision for Academic Excellence.
,•V1: 4th ICS, right of sternum
•V2: 4th ICS, left of sternum
•V3: midpoint of V2 and V4
•V4: 5th ICS, midclavicular
•V5: 5th ICS, anterior axillary line
•V6: 5th ICS, midaxillary line
•Positioned in successive steps from the patient's right to left chest
•Positive electrodes in all chest leads (AV node in the center)
12-lead EKG - Answer: •10 electrodes
•4 on all 4 limbs (RA, LL, LA, RL)
•6 on precordium (V1-V6)
•Allows interpretation of specific areas of the heart
•Inferior (II, III, avf)
•Lateral (I, avl, V5, V6)
•Anterior (V1-4)
Posterior Leads - Answer: •3 leads to assess posterior cardiac activity
•V7, V8, V9 all in the same horizontal plan as V6
•V7: left posterior axillary line
•V8: tip of the left scapula
•V9: left paraspinal
Intrinsic pacemaker (SA node) - Answer: •Generates spontaneous action potentials
•Atrial pulse is transmitted to the ventricles by the AV system - Answer: •AV node
•Bundle of His
•Purkinje fibers
2
APPHIA - Crafted with Care and Precision for Academic Excellence.
, SA node: - Answer: •sinoatrial node. Medial to opening of superior vena cava.
Comprised of highly specialized cardiac muscle cells.
•Generate spontaneous action potentials—automaticity
Atrial myocardium: - Answer: •clusters of atrial myocardial cells around the crista
terminalis—entrance of the coronary sinus and inferior vena cava, as well as cells
around the mitral and tricuspid valves
•Not conduction cells, but contractile cells that possess automaticity
AV node: - Answer: •atrioventricular node. Medial to the right atrioventricular valve.
•Action potentials conducted by cell clusters surrounding the AV node.
Ensures ventricles receive signal to contract after atria have contracted
Purkinje fibers - Answer: •Large diameter cardiac muscle cells with few myofibrils. Many
gap junctions. Conduct action potential to ventricular muscle cells
•Bundle of His and entire Purkinje network possess automaticity
Intrinsic heart rate (IHR) refers to - Answer: the inherent rate at which the heart beats
without any external influences, such as the autonomic nervous system or hormones
Action potential = - Answer: •Depolarization (activation) followed by repolarization
(recovery)
Leakage of Na+ during the resting phase is the - Answer: pacemaker potential
Contractile cardiac cells have a resting potential (unlike SA node) which - Answer:
requires activation
If positive ions surrounding the cell membrane directly match the number and alignment
of negative ions inside the cell membrane, the resting cell is - Answer: polarized
3
APPHIA - Crafted with Care and Precision for Academic Excellence.
