EKG Test 3 Questions with complete
solution 2026/2027
sinus node block - correct answer sinus node fires normally, but wave of depolarization is immediately
blocked and not transmitted into the atrial tissue.
AV block - correct answer any conduction block between the SA node and terminal Purkinje fibers
(includes AV node and His bundle)
Bundle branch block - correct answer bundle branch block = a conduction block in one or both of the
ventricular bundle branches
First degree AV blocks - correct answer prolonged delay in conduction at AV node or His bundle. Wave
of depolarization spreads normally from sinus node thru atria but gets delayed at AV node --> prolonged
PR
Dx of first-degree AV block requires only that the PR interval be longer than 0.2 seconds (one small box)
every atrial impulse does make it through the AV node and activate the ventricles, so its not really a
block but more like a delay
Every QRS has a p wave
second-degree AV block (general) - correct answer not every atrial impulse is able to pass thru AV node
into the ventricles. Some p waves fail to conduct thru the ventricles, ratio of p waves to QRS complexes
= > 1:1
2 types: Mobitz type I and II
, Mobitz Type I second-degree AV block (Wenckebach) - correct answer block w/in the AV node
block/delay is variable, increasing with each impulse. Each successive atrial impulse encounters a longer
and longer delay in the AV node until one impulse (usually every third or fourth) fails to make it through.
Progressive lengthening of PR interval w/ ea beat and then a p wave is not followed by a QRS (dropped
beat). After this initial drop beat, sequence repeats itself over and over
4:3 Wenckebach block = beat, beat, beat, p wave, DROPPED QRS, beat beat beat DROP, beat beat beat
4 p waves : 3 QRS
Mobitz type II second-degree AV block - correct answer block BELOW the AV node in the His bundle
some but not all of the impulses are transmitted to ventricles. ratio of conducted beats to nonconducted
is rarely constant
Dx = presence of a dropped beat WITHOUT progressive lengthening of the PR interval.
Is it possible to distinguish from Mobitz I or II in a 2:1 AV block? - correct answer No. it is impossible to
make this determination with only a 2:1 ratio b/c the distinction depends on a progressive PR
lengthening
true or false? Wenckenbach is typically transient and benign and rarely progresses into 3rd degree heart
block - correct answer true
Which type of 2nd degree HB can cause serious heart disease that can suddenly progress into third
degree HB? - correct answer Mobitz Type II
solution 2026/2027
sinus node block - correct answer sinus node fires normally, but wave of depolarization is immediately
blocked and not transmitted into the atrial tissue.
AV block - correct answer any conduction block between the SA node and terminal Purkinje fibers
(includes AV node and His bundle)
Bundle branch block - correct answer bundle branch block = a conduction block in one or both of the
ventricular bundle branches
First degree AV blocks - correct answer prolonged delay in conduction at AV node or His bundle. Wave
of depolarization spreads normally from sinus node thru atria but gets delayed at AV node --> prolonged
PR
Dx of first-degree AV block requires only that the PR interval be longer than 0.2 seconds (one small box)
every atrial impulse does make it through the AV node and activate the ventricles, so its not really a
block but more like a delay
Every QRS has a p wave
second-degree AV block (general) - correct answer not every atrial impulse is able to pass thru AV node
into the ventricles. Some p waves fail to conduct thru the ventricles, ratio of p waves to QRS complexes
= > 1:1
2 types: Mobitz type I and II
, Mobitz Type I second-degree AV block (Wenckebach) - correct answer block w/in the AV node
block/delay is variable, increasing with each impulse. Each successive atrial impulse encounters a longer
and longer delay in the AV node until one impulse (usually every third or fourth) fails to make it through.
Progressive lengthening of PR interval w/ ea beat and then a p wave is not followed by a QRS (dropped
beat). After this initial drop beat, sequence repeats itself over and over
4:3 Wenckebach block = beat, beat, beat, p wave, DROPPED QRS, beat beat beat DROP, beat beat beat
4 p waves : 3 QRS
Mobitz type II second-degree AV block - correct answer block BELOW the AV node in the His bundle
some but not all of the impulses are transmitted to ventricles. ratio of conducted beats to nonconducted
is rarely constant
Dx = presence of a dropped beat WITHOUT progressive lengthening of the PR interval.
Is it possible to distinguish from Mobitz I or II in a 2:1 AV block? - correct answer No. it is impossible to
make this determination with only a 2:1 ratio b/c the distinction depends on a progressive PR
lengthening
true or false? Wenckenbach is typically transient and benign and rarely progresses into 3rd degree heart
block - correct answer true
Which type of 2nd degree HB can cause serious heart disease that can suddenly progress into third
degree HB? - correct answer Mobitz Type II
