ECG Flashcards
P-R interval
0.12 - 0.20 sec (3 - 5 small squares)
QRS width
0.08 - 0.12 sec (2 - 3 small squares)
QT interval
0.35-0.43 seconds
Widowmaker:
expression describing the complete closure of the left anterior descending (LAD) coronary artery. The LAD is an essential coronary artery and its occlusion can result in immediate death
Sinus node artery supplies:
right atrium
Right marginal artery supplies:
right ventricle
Posterior descending artery supplies:
inferior walls of both ventricles
interior portion of the interventricular septum
Circumflex artery supplies:
left atrium
posterior and lateral walls of the left ventricle
anterior and inferior walls of the left ventricle
Left anterior descending artery
anterior portion of the interventricular septum
diastole:
Phase of the cardiac cycle when myocardium is relaxed
systole
Phase of the cardiac cycle when the myocardium contracts
Atrial systole
when atria contract
Ventricular systole
when ventricles contract
ECG - electrocardiogram
graphic recording of electrical events
established electrode pattern results in specific tracing pattern
electrical pattern reveals blood supply problems
ECG records a positive (upward) deflection
If an electrode is placed so that wave of depolarization spreads toward the recording electrode
negative (downward) deflection
If wave of depolarization spreads away from recording electrode
V1
Fourth intercostal space to the right of the sternum
V2
Fourth intercostal space to the Left of the sternum
V3:
Directly between leads V2 and V4
V4:
Fifth intercostal space at midclavicular line
V5:
Level with V4 at left anterior axillary line
V6:
Level with V5 at left midaxillary line. (Directly under the midpoint of the armpit)
Where does Lead I travel?
travels’ horizontally
Its left pole (LA) is positive and its right pole (RA) is negative
What does Lead I show?
Shows a positive wave when an impulse moves towards the left arm, negative wave when an impulse moves away from the left arm
P wave:
atrial depolarization
PR segment:
delay of conduction from AV node
QRS complex:
ventricular depolarization (.06-.10 sec)
ST segment:
repolarization begins
T Wave:
repolarization
Sinus Pause/Block:
SA node fails to initiate impulse, usually only for one cycle
RR interval: occasional pauses noted
Causes of Sinus Block:
increased parasympathetic activity
disease of SA node
infection
severe ischemia
Atrial tachycardia:
3 or more premature atrial complexes in a row
P waves not always present before QRS complex
Atrial flutter:
multiple P waves before QRS complex
Atrial Fibrillation
no P waves
AV node controls impulse that activates QRS complex
Causes of atrial fibrillation
atria does not contract
could develop clots
CHF, ischemia
Junctional (Nodal) Rhythm
AV node takes over as pacemaker of heart
no P wave before QRS complex
1st Degree AV block
impulse at SA node delayed on way to AV node
lengthened PR interval
2nd Degree AV block Type I (Mobitz I)
prevents conduction of some impulse thru AV node
P wave can stand alone
lengthening of PR interval
2nd Degree AV block Type II (Mobitz II)
no conduction of impulses to ventricles without change to PR interval
ratio of P waves to QRS complex greater than 1:1
2-4 P waves for every QRS complex
3rd Degree AV Block
all impulses initiated above ventricles; are not conducted to ventricles
no relation between P waves and QRS complex
Premature Ventricular Complex
impulse originates in ventricles
QRS complex: wide without P wave, followed by compensatory pause
Ventricular Tachycardia
3 or more PVCs in a row
no P wave
QRS wide and bizarre
Ventricular Fibrillation
erratic quivering of ventricular muscles resulting in no cardiac output
What does T wave inversion mean?
ischemia
What does elevated ST segment mean?
ischemia
What does depressed ST segment mean?
infarction
