Electrocardiography Flashcards
Fascicles
three conducting fiber bundles (right branch of bundle of HIS + anterior and posterior hemibranches)
unifascicular block of conduction through one of the three bundles
still allows impulse from atria into ventricles
bifascicular block
still allows impulse from atria into ventricles
trifascicular block
same effect as AV node blockade…prevents signals from atria to ventricles
trifascicular block causes
myocardial scarring from infarction
amyloidosis
sarcoidosis in the heart, esp. in young AA
A cardiac arrhythmia (esp. heart block) in young african american suggests…
possible cardiac sarcoidosis
Each heartbeat is reflected on EKG by 3 major deflections
- P wave
- QRS complex
- T wave
PR interval
onset of P to end of QRS
represents length of time for signals to propagate from SA node through AV node and ventricles
Normal PR interval
120-200ms
first degree AV block (1st degree heart block)
PR>200ms but w/ all impulses from atria getting through
QRS interval
less than or equal to 100ms
longer QRS intervals
aberrantly conducted impulses or impulses from abnormal places
If the QRS interval is not widened, QT interval represents…
ventricular repolarization
needs correction for heart rate to be helpful, since faster HRs mean faster repolarization
QTc
QT interval corrected for heart rate
normally less than or equal to 440ms
prolonged QT…most common cause
dangerous!
myocardial ischemia
other causes of prolonged QT
blood electrolyte abnormalities (i.e. hypokalemia, hypocalcemia, hypomagnesemia)
channelopathy
reflect anatomic site of heart disease w/in organ
abnormalities in 12-lead EKG
Disease of the anterior LV served by LAD coronary artery
Abnormalities in leads V1-V4
disease of lateral left ventricle served by left circumflex coronary artery
abnormalities in V5-V6
disease in right coronary artery territory, the inferior left ventricle
Abnormalities in leads II, III, and aVF
acute blockage of a major epicardial coronary artery
elevation of ST segment (end of QRS and beginning of T wave)
T wave commonly inverted
large transmural myocardial infarction
permanently misshapen QRS complex w/ abnormally large, long, deep initial downward deflection (pathologic Q wave)
innocent Q waves
some heart murmurs
some S3s and S4s
abnormalities in 12-lead EKG
reflect anatomic site of heart disease w/in organ
Abnormalities in leads V1-V4
Disease of the anterior LV served by LAD coronary artery
abnormalities in V5-V6
disease of lateral left ventricle served by left circumflex coronary artery
Abnormalities in leads II, III, and aVF
disease in right coronary artery territory, the inferior left ventricle
elevation of ST segment (end of QRS and beginning of T wave)
T wave commonly inverted
acute blockage of a major epicardial coronary artery
permanently misshapen QRS complex w/ abnormally large, long, deep initial downward deflection (pathologic Q wave)
large transmural myocardial infarction
Differentiate b/w sinus tachycardia and tachyarrhythmia
sinus tachycardia knows its limits and will not go over rate of 220 minus pt’s age
a 20 yr old w/ sinus tachycardia of 200 (who has not just sprinted) is…
critically ill, but not likely from intrinsic heart disease
look for: anaphylaxis PE cocaine occult bleeding sepsis SIRS thyroid storm
many tachyarrhythmias that orriginate from above ventricles (supraventricular) are…
sort of innocent
examples:
**atrial fibrillation
atrial flutter
supraventricular tachycardia
atrial fibrillation
easy to spot
rhythm is irregular
rate is high or normal (60-220)
no P waves
atrial flutter
results from reentrant circuit around tricuspid valve
two P waves for each QRS
HR around 150
Supraventricular tachycardia
reentrant pathway in atria right near AV node
can respond to home remedy vagal maneuvers such as Valsalva maneuver, carotid sinus massage, immersion of face in a pan of ice water
Ventricular tachyarrhythmias
dangerous
2 major types of ventricular arrhythmias
ventricular tachycardia
ventricular fibrillation
QRS complex wide (over 120ms) and HR usually less than 200
ventricular tachycardia
- -If all QRS look alike…monomorphic
- -if QRS complexs vary in morphology…polymorphic
ventricular tachycardia
can degenerate into ventricular fibrillation
ventricular fibrillation
immediately life-threatening
totally diordered rapid stimulation of ventricles
due to fragmentation of wave of depolarization into numerous tiny wavelets going every which way
chaotic pattern w/out discrete QRS complexes
Ventricular fibrillation
Treatment for v fib
elecrical defibrillation or punch to the sternum if not available
(RARE: punch to sternum in healthy individual can cause fatal arrhythmia…commotio cordis)
