ECG Flashcards
pacemaker rate at the SA node
60-100
pacemaker rate @ AV node
40-55
pacemaker rate @ bundle of His, bundle branches, purkinje fibers
25-40
normal P wave duration
0.06-0.11
normal QRS complex duration
0.07-0.11
normal PR interval duration
0.12-0.2
ventricular myocyte repolarization (phase 3)
T wave
the entire action potential for the ventricular myocytes (depolarization- plateau- repolarization)
QT interval
ventricular myocyte plateau phase (phase 2)
ST segment
ECG interpretation - top 4 questions
- are there P waves?
- is there a P wave following every QRS?
- what is pacing the heart?
- what does each deflection look like?
axis: 0 degrees
lead I
axis: 60 degrees
lead II
axis: 120 degrees
lead III
axis: -30 degrees
avL
axis: 90 degrees
avF
axis: -150 degrees
avR
precordial lead placement: right 4th interspace, adjacent to sternum
V1
precordial lead placement: left 4th interspace adjacent to the sternum
V2
precordial lead placement: positioned halfway between V2 and V4
V3
precordial lead placement: the 5th interspace on the midclavicular line;
V4
precordial lead placement: placed directly lateral to V4 with V5 on the anterior axillary line and V6 on the midaxillary line.
V5, V6
which segment is roughly coincident with phase 2 of the AP?
ST segment
that point where the QRS joins the ST segment with an angle normally about 90°
The J point
which pacemaker is not included in the PR interval?
the SA node
why is the t wave and the qrs upright?
b/c the myocardium repolarizes in the opposite direction from the depolarization event
waves and complexes analysis consists of what?
- Duration
- Amplitude
- Morphology
- Vector
p waves are always negative in ______
aVR
what is the best lead to look at p waves?
lead 2
tall p waves in lead 2 & V1 associated with what abnormality?
right atrial conduction abnormality
notched p waves in lead 2 associated with what abnormality?
left atrial conduction abnormality
PR interval >0.2 sec
1st degree AV block
what can cause the PR interval to prolong?
increases with age
what does the QT interval represent?
the time that it takes the entire heart to cycle 1x
how to measure QT interval
beginning to QRS to end of T wave
axis determination: if lead 1 & aVF positive?
axis is normal
axis determination: if lead 1 is positive, aVF is negative
axis if leftward
axis determination: is lead 1 is negative, aVF is positive
axis is rightward
tall pointy p wave in lead 2?
right atrial abnormality
people with ____BBB have a worse CV prognosis than ppl who don’t
LBBB
results in broad QS in V1 and broad, slurred R wave in V6;
LBBB
shows broad QRS with an rSR’ pattern in V1 and deep, broad S wave in V6.
RBBB
how many fascicles in right bundle?
1
Left axis, at least –45 degrees, QRS
Left Anterior Fascicular Block
Right axis, usually +120 or more, normal QRS, no evidence or RVH
Left Posterior Fascicular Block
what are the most common types of trivascicular blocks?
RBBB + LAFB + 1st degree AV block
if block in all fascicles is complete?
3rd degree AV block
PR interval >0.2, unrelated to ischemic heart disease & generally benign
first degree AV block
PR interval, usually normal, progressively lengthens until AV conduction is lost; Grouped QRS complexes, longest cycle is less than twice the length of the shortest cycle;
2nd degree AV block Type 1: “the Wenckebach phenomenon
which type almost always includes a BBB, includes dropping of the QRS without prolongation of PR interval
2nd degree AV block type 2
which type of 2nd degree AV block has a worse prognosis?
type 2
what are the 3 main determinants of myocardial oxygen demand?
HR, contractility, myocardial wall tension
which layer of the myocardium is most susceptible to damage?
subendocardial layer
pre-excitation plus the classic supraventricular arrhythmia
Wolff-Parkinson-White syndrome
ECG result is a short PR interval (
ventricular pre-excitation
what is the most common cause of a pause on an ECG?
nonconducted atrial premature
ventricular prematures that occur in the ________ventricle are more commonly associated with heart disease
LEFT VPD
is a fib or a flutter faster & irregularly irregular?
atrial fib
what is the Most common arrhythmia in US
a fib
common in healthy young people, related to anxiety, excess caffeine, fatigue
reentrant junctional tachyarrhytmias
if apply carotid sinus massage to sinus tach, what happens?
can break the rhythm
if apply carotid sinus massage to atrial flutter
doesn’t convert, but brings out the flutter waves
if apply carotid sinus massage to reentrant jxnal tachycardia?
converts to sinus rhythm
