Sharp ECG Study Guide
4 primary characteristics of the heart - CORRECT ANSWER-automaticity
excitability
conductivity
contractility
automaticity - CORRECT ANSWER-i. Specific to the pacemaker cells; ability to
generate their own electrical impulse spontaneously
excitability - CORRECT ANSWER-Ability of ALL cardiac cells to respond to an electrical
impulse
conductivity - CORRECT ANSWER-i. Ability of ALL cardiac cells to conduct an electrical
impulse
contractility - CORRECT ANSWER-i. Specific to muscle cells; ability to cause cardiac
muscle contraction
electrons/ions responsible for depolarization/repolarization of the heart muscle -
CORRECT ANSWER-Potassium
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 ANSWER-i. 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 ANSWER-i. 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 ANSWER-i. 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 ANSWER-i. 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 ANSWER-ST 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
Layers of the heart - CORRECT ANSWER-pericardium
myocardium
endocardium
pericardium - CORRECT ANSWER-outermost 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 ANSWER-i. 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 ANSWER-i. 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.
causes of ST elevation - CORRECT ANSWER-i. MI (STEMI)
4 primary characteristics of the heart - CORRECT ANSWER-automaticity
excitability
conductivity
contractility
automaticity - CORRECT ANSWER-i. Specific to the pacemaker cells; ability to
generate their own electrical impulse spontaneously
excitability - CORRECT ANSWER-Ability of ALL cardiac cells to respond to an electrical
impulse
conductivity - CORRECT ANSWER-i. Ability of ALL cardiac cells to conduct an electrical
impulse
contractility - CORRECT ANSWER-i. Specific to muscle cells; ability to cause cardiac
muscle contraction
electrons/ions responsible for depolarization/repolarization of the heart muscle -
CORRECT ANSWER-Potassium
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 ANSWER-i. 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 ANSWER-i. 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 ANSWER-i. 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 ANSWER-i. 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 ANSWER-ST 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
Layers of the heart - CORRECT ANSWER-pericardium
myocardium
endocardium
pericardium - CORRECT ANSWER-outermost 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 ANSWER-i. 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 ANSWER-i. 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.
causes of ST elevation - CORRECT ANSWER-i. MI (STEMI)
