IBHRE EXAM SCRIPT 2026
COMPREHENSIVE QUESTIONS WITH
VERIFIED SOLUTIONS
◉ effective refractory period
Answer: the longest coupling interval to be associated with block
◉ resting (transmembrane) potential
Answer: the voltage difference between the inside and outside of the
cell fiber (negative inside cell)
◉ action potential
Answer: the cellular characteristics of depolarization and
repolarization. Consists of 5 phases (0-4)
◉ Phase 0 of action potential
Answer: the depolarization phase. during this phase, th rapid
sodium channels are stimulated to open, causing the resting
transmembrane potential to spike from about -90 mV to about 0 mV.
◉ Phase 1 of action potential
,Answer: Early repolarization
◉ Phase 2 of action potential
Answer: the plateau phase. this phase, mediated by the slow calcium
channels, essentially disrupts and delays repolarization started in
phase 1 and prolongs the refractory period
◉ Phase 3 of action potential
Answer: the end of repolarization. Note: the period beginning at the
end of phse 0 through the end of phase 3 is the refractory period of
cardiac tissue. (opening of K+ channels, K+ out
(closing of ca+ channels))
◉ Phase 4 of action potential
Answer: the resting phase. It is during this phase that, in some
cardiac cells, ions leak back and forth between membranes and
cause a gradual increase in the transmembrane (resting) potential.
◉ Automaticity
Answer: The spontaneous depolarization to threshold, characteristic
of cardiac pacemaker cells.
◉ AR interval
,Answer: this begins when the atrial escape interval is allowed to
time out completely
◉ Atrial escape interval
Answer:
◉ AVRT (Atrioventricular reentrant tachycardia)
Answer: av conduction and accessory pathway create a reentrant
circuit causing tachycardia
◉ AVNRT (AV nodal reentrant tachycardia)
Answer: This occurs when a reentrant circuit occurs in the AV node.
A premature beat reactivates the slow pathway and creates a loop
with the fast pathway after its refractory period. this rhythm
accounts for 60% of SVT and paroxysmal AT/AF. the rhythm will
have a narrow QRS and have a rate of about 150-200 bpm
◉ AVNRT treatment
Answer: -Catheter ablation of the slow pathway
◉ AVNRT - symptoms
Answer: palpitations, neck throbbing, polyuria, syncope
, ◉ Adenosine with AVNRT
Answer: this helps differentiate AVNRT from AT. If AV block is
produced but A rhythm remains its AT
◉ Rheobase
Answer: the lowest threshold possible on the strength/duration
curve
◉ Chronoxie
Answer: the pulse width on the strength duration curve where the
rheobase x 2 is the point for the stimulus strength. This is the most
efficient pulse width
◉ charge
Answer: current x time (mC)
◉ energy
Answer: current x voltage x time (mJ)
◉ ANP/BNP (atrial natriuretic peptide) increases
Answer: Substance produced by atrium when its subjected to a
higher pressure, point to VVIR pacing and loss of capture as culprit
COMPREHENSIVE QUESTIONS WITH
VERIFIED SOLUTIONS
◉ effective refractory period
Answer: the longest coupling interval to be associated with block
◉ resting (transmembrane) potential
Answer: the voltage difference between the inside and outside of the
cell fiber (negative inside cell)
◉ action potential
Answer: the cellular characteristics of depolarization and
repolarization. Consists of 5 phases (0-4)
◉ Phase 0 of action potential
Answer: the depolarization phase. during this phase, th rapid
sodium channels are stimulated to open, causing the resting
transmembrane potential to spike from about -90 mV to about 0 mV.
◉ Phase 1 of action potential
,Answer: Early repolarization
◉ Phase 2 of action potential
Answer: the plateau phase. this phase, mediated by the slow calcium
channels, essentially disrupts and delays repolarization started in
phase 1 and prolongs the refractory period
◉ Phase 3 of action potential
Answer: the end of repolarization. Note: the period beginning at the
end of phse 0 through the end of phase 3 is the refractory period of
cardiac tissue. (opening of K+ channels, K+ out
(closing of ca+ channels))
◉ Phase 4 of action potential
Answer: the resting phase. It is during this phase that, in some
cardiac cells, ions leak back and forth between membranes and
cause a gradual increase in the transmembrane (resting) potential.
◉ Automaticity
Answer: The spontaneous depolarization to threshold, characteristic
of cardiac pacemaker cells.
◉ AR interval
,Answer: this begins when the atrial escape interval is allowed to
time out completely
◉ Atrial escape interval
Answer:
◉ AVRT (Atrioventricular reentrant tachycardia)
Answer: av conduction and accessory pathway create a reentrant
circuit causing tachycardia
◉ AVNRT (AV nodal reentrant tachycardia)
Answer: This occurs when a reentrant circuit occurs in the AV node.
A premature beat reactivates the slow pathway and creates a loop
with the fast pathway after its refractory period. this rhythm
accounts for 60% of SVT and paroxysmal AT/AF. the rhythm will
have a narrow QRS and have a rate of about 150-200 bpm
◉ AVNRT treatment
Answer: -Catheter ablation of the slow pathway
◉ AVNRT - symptoms
Answer: palpitations, neck throbbing, polyuria, syncope
, ◉ Adenosine with AVNRT
Answer: this helps differentiate AVNRT from AT. If AV block is
produced but A rhythm remains its AT
◉ Rheobase
Answer: the lowest threshold possible on the strength/duration
curve
◉ Chronoxie
Answer: the pulse width on the strength duration curve where the
rheobase x 2 is the point for the stimulus strength. This is the most
efficient pulse width
◉ charge
Answer: current x time (mC)
◉ energy
Answer: current x voltage x time (mJ)
◉ ANP/BNP (atrial natriuretic peptide) increases
Answer: Substance produced by atrium when its subjected to a
higher pressure, point to VVIR pacing and loss of capture as culprit
