Heart Waveforms/ECG Flashcards
P wave
atrial depolarization
PR interval
time for atrial depolarization and conduction from SA node to AV node
duration 0.12-0.20 seconds
QRS complex
ventricular depolarization and atrial repolarization
duration 0.06-0.10 seconds
QT interval
time for both ventricular depolarization and repolarization
duration 0.20-0.40 seconds
ST segment
isoelectric period following QRS when ventricles are depolarized
T wave
ventricular repolarization
Premature atrial contractions (PAC)
P wave is premature with abnormal configuration
very common
benign
atrial flutter, tachy, fibrillation
Atrial flutter
sawtooth P waves
occurs with valvular disease, ischemic heart disease, HTN, MI
A-fib
not discrete P waves
1st degree AV block
PR interval is longer than 0.2 seconds but relatively constant from beat to beat
no symptoms
can be caused from medications
2nd degree AV block
disturbance which impulses between atria and ventricles fail intermittently
two types
Mobitz I (2nd degree AV block)
Mobitz II
progressive prolongation of PR interval until one impulse is not conducted
consecutive drop in PR interval
3rd degree AV block
all impulses are blocked
considered medical emergency
PVC
P wave is usually absent and QRS has wide aberrant shape
Bigeminy- normal sinus impulse followed by PVC
Trigeminy- PVC occurs after every two normal sinus impulses
common
asymptomatic
V-tach
P waves are absent and QRS are wide and aberrant
longer than 30 seconds is life threatening
V-fib
no cardiac output
pt becomes unconscious
Ventricular asystole
death
CPR
MI ECG signs:
ST segment depression
ST segment elevation
Q wave
T wave inversion
subendocardial ischemia
earliest sign of acute transmural infarction
marker of infarction due to necrosis
occurs hours or days after MI
Absolute indication for ending a stress test
drop in SBP>10 mmHg with other evidence of ischemia
moderately severe angina (3/4)
increasing nervous system symptoms (ataxia, dizziness)
cyanosis, pallor
sustained v-tach
>1.0 mm ST elevation
Relative indications for ending a stress test
drop in SBP> 10 mmHg without other evidence of ischemia
>2 mm ST displacement (horizontal or downsloping)
arrhythmias other than sustained v-tach
fatigue, SOB, wheezing, leg cramps and claudication
development of BBB
increasing chest pain
hypertensive response (>250 and/or >115)
How to analyze a ECG?
scan the rhythm
determine HR
evaluate R-R interval
Evaluate P waves
measure PR interval
examine QRS
assess ST segment 0.08 seconds after J point
How to determine HR on ECG
count number of QRS complexes in 6 second strip and multiply by 10
R-R intervals time
0.04
P waves in ECG
present vs absent
identical in shape
upright in leads I, II, III
each P wave followed by a QRS
P waves present measure PR interval and what should the length be
0.12-0.20
QRS width
0.04-0.10
Negative stress test=
Positive stress test=
low probability of coronary artery disease
high probability of coronary artery disease
Percussion interpretation:
flat or dull
resonance
hyperresonance
tympany
like on a thigh (suggest neoplasm in lung, atelectasis or consolidation)
normal air filled lung
emphysematous lung; pneumothorax
drumbeat-large pneumothorax
