Abnormal ECG Flashcards
where are leads V1-6 placed?
V1 is just right of sternal border, V2 is just left of sternal border, and V3-6 move laterally to the left from there
which leads indicate the following:
a. normal electrical axis
b. LAD (left axis deviation)
c. RAD (right axis deviation)
d. extreme RAD
a. normal: QRS I(+), II(+)
b. LAD: QRS I(+), II(-)
c. RAD: QRS: I(-), AVF(+)
d. extreme RAD: QRS I(-), AVF(-)
what kind of electrical axis deviation would myocardial infarction cause?
LAD (left axis deviation)
what kind of electrical axis deviation would left posterior fascicular block cause?
right axis deviation (RAD)
left bundle branch divides into anterior and posterior fascicle - block in anterior fascicle will cause LAD, block in posterior fascicle will cause RAD
how you can tell from the R wave of an ECG if there is left or right ventricular hypertrophy?
rough measurement -
if R wave in the aVL is greater/equal to 11mm, there is LV hypertrophy
if R wave in V1 is greater/equal than 7mm, there is RV hypertrophy
how is 1st degree AV block represented on ECG?
PR interval > 200 msec
due to delay in AV node conductance (but every wave conducts)
where do Mobitz 1 vs Mobitz 2 heart block typically occurs?
2nd degree heart blocks
Mobitz 1 (Wenckebach): usually AV node, increasing PR intervals until dropped QRS
Mobitz 2: usually His-Purkinje (farther down in conductance system = worse), suddenly non-conducted QRS (same PR intervals), risk to progress to complete heart block
match with either Type I or II 2nd degree heart block
a. can occur in athletes with high vagal tone
b. underlying heart disease is present
c. can be induced by cardiomyopathy due to amyloidosis
d. can be induced by myocarditis due to Chagas disease
e. can be induced by myocarditis due to Lyme’s disease
f. usually in AV node
g. usually in His-Purkinje system
Type I (Wenckebach): usually in AV node, can occur in athletes with high vagal tone, can be induced by myocarditis due to Chagas disease
Type II: usually in His-Purkinje system, underlying heart disease present, can by induced by cardiomyopathy due to amyloidosis, can be induced by myocarditis due to Lyme’s disease
explain what a “cannon A wave” finding is
physical finding of complete heart block, due to ventricles contracting at the same time as the atria
large-amplitude waves seen in jugular veins during PE
what is an ECG finding in right or left bundle branch blocks?
Wide QRS - you can only get a narrow QRS if R/L bundle branches are depolarizing at the same time
what are ECG findings in left and right bundle branch blocks, respectively?
wide QRS either way
left: deep S-wave in V1, broad/notched R wave in V6
right: RSR’ (R-S-R prime: R prime just means a second/bigger R wave) in V1, deep/broad S wave in V6
which is more common, an anterior or posterior fascicular block?
recall left bundle branch divides into anterior and posterior fascicle - block in anterior fascicle will cause LAD, block in posterior fascicle will cause RAD
posterior fascicule is larger/wider
so it is more likely to get a block in anterior (smaller) fascicule
what does an abnormally short vs long PR interval indicate?
long PR interval = delay in AV node conduction, vagal stimulation
short PR interval = ventricular “pre-excitation” (Wolff-Parkinson White), junctional rhythm, SNS activation
what is Wolff-Parkinson White syndrome? how does it appear on ECG?
syndrome = WPW pattern + symptoms
accessory/extra electrical pathway (Bundle of Kent) allows conduction to bypass AV node —> ventricular pre-excitation
short PR interval + delta wave (wide base of QRS - gets narrow at peak once depolarization gets through AV node)
how do hyperkalemia and Na+ channel blockers affect the QRS complex?
widened QRS, due to slower conduction speed
