Sharp ECG Study Guide Latest update
2025/2026 Graded A+
Layers of the heart - correct answerpericardium
myocardium
endocardium
pericardium - correct answeroutermost layer: fibrous and serous
fibrous
-outer sack that anchors the heart
serous
-inner, fluid secreting membrane with two layers
-parietal (lines inner surface of fibrous sac)
-visceral (AKA epicardium) lines myocardium
-between the two is the pericardial space, with 10-30ml of fluid to give the heart space
to relax and contract
myocardium - correct answeri. Thick, middle muscular layer that makes up the bulk of
the heart wall
ii. Composed of cardiac muscle cells and is responsible for the heart's ability to contract
endocardium - correct answeri. Thin layer of tissue that lines the inner surface of heart
muscle and heart chambers
ii. Extensions and folds of this tissue forms the valves of the heart.
4 primary characteristics of the heart - correct answerautomaticity
excitability
conductivity
contractility
automaticity - correct answeri. Specific to the pacemaker cells; ability to generate their
own electrical impulse spontaneously
excitability - correct answerAbility of ALL cardiac cells to respond to an electrical
impulse
conductivity - correct answeri. Ability of ALL cardiac cells to conduct an electrical
impulse
, contractility - correct answeri. Specific to muscle cells; ability to cause cardiac muscle
contraction
electrons/ions responsible for depolarization/repolarization of the heart muscle - correct
answerPotassium
i. Primary ion inside the cell
ii. Plays a role in depolarization and repolarization
Sodium
i. Primary ion outside the cell
ii. Major role in depolarization
sodium-potassium pump - correct answeri. Actively transports ions across the
membrane against the electrochemical gradient
ii. In a resting cardiac cell, there are more negative ions on the inside than the outside.
This is a resting, or polarized cell. No electrical activity is occurring and there is an
isoelectric (straight) line on ECG
depolarization - correct answeri. When a cell is stimulated, potassium begins to leave
the cell, increasing permeability to sodium
ii. Sodium rushes in, causing the inside of the cell to be more positive than negative
iii. Contraction is a mechanical process that FOLLOWS the electrical event of
depolarization
repolarization - correct answeri. Sodium-potassium pump activated to transport sodium
out of the cell and move potassium back into the cell
ii. Inside becomes more negative again
Positive, negative, and biphasic deflection - correct answeri. Positive deflection: electric
current flowing towards the positive pole
ii. Negative deflection: electric current flowing towards the negative pole
iii. Biphasic deflection: current flowing away from both poles
ST segment - correct answerST represents early ventricular repolarization
Measure .04 (one box) from J point...
elevation or depression is considered abnormal if displacement is greater than 1mm
from baseline
causes of ST elevation - correct answeri. MI (STEMI)
2025/2026 Graded A+
Layers of the heart - correct answerpericardium
myocardium
endocardium
pericardium - correct answeroutermost layer: fibrous and serous
fibrous
-outer sack that anchors the heart
serous
-inner, fluid secreting membrane with two layers
-parietal (lines inner surface of fibrous sac)
-visceral (AKA epicardium) lines myocardium
-between the two is the pericardial space, with 10-30ml of fluid to give the heart space
to relax and contract
myocardium - correct answeri. Thick, middle muscular layer that makes up the bulk of
the heart wall
ii. Composed of cardiac muscle cells and is responsible for the heart's ability to contract
endocardium - correct answeri. Thin layer of tissue that lines the inner surface of heart
muscle and heart chambers
ii. Extensions and folds of this tissue forms the valves of the heart.
4 primary characteristics of the heart - correct answerautomaticity
excitability
conductivity
contractility
automaticity - correct answeri. Specific to the pacemaker cells; ability to generate their
own electrical impulse spontaneously
excitability - correct answerAbility of ALL cardiac cells to respond to an electrical
impulse
conductivity - correct answeri. Ability of ALL cardiac cells to conduct an electrical
impulse
, contractility - correct answeri. Specific to muscle cells; ability to cause cardiac muscle
contraction
electrons/ions responsible for depolarization/repolarization of the heart muscle - correct
answerPotassium
i. Primary ion inside the cell
ii. Plays a role in depolarization and repolarization
Sodium
i. Primary ion outside the cell
ii. Major role in depolarization
sodium-potassium pump - correct answeri. Actively transports ions across the
membrane against the electrochemical gradient
ii. In a resting cardiac cell, there are more negative ions on the inside than the outside.
This is a resting, or polarized cell. No electrical activity is occurring and there is an
isoelectric (straight) line on ECG
depolarization - correct answeri. When a cell is stimulated, potassium begins to leave
the cell, increasing permeability to sodium
ii. Sodium rushes in, causing the inside of the cell to be more positive than negative
iii. Contraction is a mechanical process that FOLLOWS the electrical event of
depolarization
repolarization - correct answeri. Sodium-potassium pump activated to transport sodium
out of the cell and move potassium back into the cell
ii. Inside becomes more negative again
Positive, negative, and biphasic deflection - correct answeri. Positive deflection: electric
current flowing towards the positive pole
ii. Negative deflection: electric current flowing towards the negative pole
iii. Biphasic deflection: current flowing away from both poles
ST segment - correct answerST represents early ventricular repolarization
Measure .04 (one box) from J point...
elevation or depression is considered abnormal if displacement is greater than 1mm
from baseline
causes of ST elevation - correct answeri. MI (STEMI)
