Electrocardiogram (ECG) Flashcards
Where are the 4 limb leads located?
Which is the ground electrode?
Right Arm(RA): infraclavicular fossa Left Arm (LA): infraclavicular fossa Leg LEG (LL): left side of abdomen below rib cage Right Leg (RL): right side of abdomen RL IS GROUND ELECTRODE
How many leads vs. how many electrodes are used with ECG?
12 lead 10 electrodes (4 limb leads and 6 precordial leads)
What is the location for the precordial leads?
V1: 4th intercostal space at right sternal border (start on other side of heart)
V2: 4th intercostal space on left sternal border
V3: midway between V2 and V4
V4: 5th intercostal space at left midclavicular line
V5: left anterior axillary line at V4 level
V6: left midaxillary line at V4/V5 level
What occurs during
- P wave
- PR interval
- QRS Complex
- QT Interval
- ST Segment
- T Wave
- P wave - atrial depolarization
- PR interval - time for atrial depolarization and conduction from SA node to AV node
- QRS Complex - ventricular depolarization and atrial repolarization
- QT Interval - time for both ventricular depolarization and repolarization (INCLUDES ENTIRE T WAVE)
- ST Segment - isoelectric period following QRS
- T Wave - ventricular repolarizations
- How long is the PR interval?
- How long is QRS complex?
- How long is QT interval?
- 0.12 - 0.20 seconds OR 12 to 20 ms (includes entire P wave)
- 0.06-0.10 seconds or 6 to 10 ms
- 0.20 - 0.40 or 20 to 40 ms (includes entire Q and T waves)
what is normal sinus rhythm?
60-100 bpm
Sinus brachy vs. tachycardia?
Brachy <60 bpm
Tachy > 100 bpm
What is a sinus rhythm but with intermittent failure of either SA nod impulse formation or AV node conduction that results in the occasional complete absence of P or QRS waves?
Sinus Arrest
What occurs when an ectopic foci in the atrium initiates an impulse before the SA node and the P wave is premature with ABNORMAL CONFIGURATION?
Premature Atrial Contractions (PACS)
What is the clinical significance of Premature Atrial Contractions?
very common and generally benign (stress, affeine, smoking, alcohol)
However may progress to atrial flutter, tachycardia, or fibrillation
what is ectopic very rapid atrial tachycardial with a rate of 250-350 bpm?
Atrial Flutter
What is the shape of the P waves with Atrial Flutter?
Saw-tooth P waves
What are 2 main conditions that Atrial Flutter occurs with?
Valvular Disease (especially mitral) and ischemic heart disease
Common arrhythmia where atria depolarized 350-600 times per minute?
Atrial Fibrilation
What does the ECG look like with Atrial Fibrilation?
irregular undulations of ECG without discrete P waves
What 3 conditions does A-Fib appear in?
Coronary artery disease, hypertension, and valvular disease
What does a 1st degree AV block look like on ECG and what are symptoms?
PR interval longer than 0.2 seconds but constant beat to beat
No symptoms or significant change in cardiac function
what causes first degree AV block?
many reasons including medication to suppress AV conduction
How does a second degree AV block appear on ECG?
AV conduction disturbance in which impulses between atria and ventricles fail intermittently
What are the two types of Second Degree AV blocks and whats the differenc?
Mobitz I: progressive prolongation of PR interval until 1 impulse is not conducted (GENRALLY BENIGN)
Mobitz II: consecutive PR intervals are same and normal followed by non-conduction of one or more impulses (more serious)
What occurs with 3rd degree heart block?
ALL impulses are blocked at AV node and none are transmitted to ventricles
atria and ventricles paced independently with atria>ventricles
What degree of AV block is a medical emergency requiring a pacemaker?
3rd degree AV block
what are 4 causes of third degree AV block?
degenerative changes of conduction systems, digitalis, heart surgery, and acute MI
How does a Premature Ventricular Contraction (PVC) generally appear on the ECG?
P wave is usually absent and QRS complex has a wide and abberant shape
What is a Bigeminy vs Trigeminy?
Bigeminy: normal sinus impulse followed by a PVC
Tigeminy: PVC occurs after every two normal sinus impulses
What is 3 or more consecutive PVCs at a ventricular rate >150 bpm?
Ventricular Tachycardia (V-Tach)
How does ventricular tachycardia appear on ECG?
P waves are absent and QRS complexes are wide adn abberant in appearance
When does V-tach become life threatening?
When it lasts longer than 30 seconds or if it degenerates into ventricular fibrillation
what is it called when ventricles do not beat in a coordinated fashion but fibrillate or quiver asynchronously and ineffectively?
Ventricular Fibrillation
How does Ventricular Fibrillation appear on ECG?
fibrallatory waves with irregular pattern that is either fine or course
What is the immediate intervention required for Ventricular Fibrillation?
Defibrilation
What shows a stright line pattern on ECG and requires immediate CPR and medications to stimulate cardiac activity?
Ventricular Asystole
what are 4 possible areas to find signs of Myocardial Ischemia and Infarction on an ECG?
- ST Segment depression
- ST Segment Elevation
- Q Wave
- T Wave Inversion
Where is ST elevation seen on ECG?
0.08 seconds AFTER (2 small boxes) the J point (junction between end of QRS complex and beginning of ST segment)
What are 3 causes of ST segment depression?
- Subendocardial Ischemia
- Digitalis Toxicity
- Hypokalemia
What is the earliest sign of acute transmural infarction on ECG?
TRANSMURAL: MI is characterized by ischemic necrosis of the full thickness of the affected muscle segment(s), extending from the endocardium through the myocardium to the epicardium
ST Segment Elevation
What is a characteristic marker of infarction?
Q wave longer than 0.04 sec and larger than 1/3 the amplitude of the R wave
Small box is 0.04 seconds and 1 mm
When does T wave inversion occur?
hours or days after MI as the result of delay in repolarization produced by injury
Other than infarction, what is another reason a T-Wave inversion may occur? (2)
with right and left bundle branch blocks and after a CVA
How many seconds are typically on an ECG strip?
10 seconds
how many millimeters is each large and small box on ECG?
what is the time interval per box????
**KNOW BOTH OF THESE**
Small box: 1 mm
LArge box: 5 mm
Small box: 40 ms
Large box: 200 ms
How to caculate HR?
Multiple QRS complexes by 6 in 10 second strip OR
count the number of large squares between two consecutive P waves and divide by 300
Measuring the PR interval will determine what?
Determine if a conduction block is present
Normal time is 0.12 to 0.20 seconds
Where is ST segment evaluated?
0.08 seconds after the J point
What is the difference between ST segment depression and ST segment elevation on ECG?
ST Segment Depression inidicates subendocardial (non-full thickness) ischemia
ST Segment Elevation indicates acute transmural (full thickness) infarction
