Relias Dysrhythmia Basic A 2025| 35 ECG Rhythm
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1
Questions with Verified Answers + Diagrams | A+
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QUESTION |1
Rationale:
The |rhythm |strip |presented |displays |an |overall |regular |sinus |rhythm |with |one |early, |wide, |and |bizarre |QRS
|complex |that |interrupts |the |normal |pattern. |This |aberrant |complex |is |not |preceded |by |a |P |wave, |and |it |has |a
|duration |significantly |longer |than |the |surrounding |QRS |complexes |— |a |hallmark |feature |of |a |premature
|ventricular |contraction |(PVC).
In |normal |sinus |rhythm, |each |QRS |complex |follows |a |P |wave |at |regular |intervals, |and |the |morphology |is
|uniform. |However, |in |this |strip, |one |QRS |complex |appears |prematurely |and |does |not |follow |the |same |shape |or
|duration |as |the |others, |indicating |that |it |originates |from |the |ventricles |rather |than |the |atria.
, This |distinguishes |the |rhythm |from:
• Sinus |rhythm |with |PAC |(D): |PACs |have |premature |P |waves |followed |by |normal-looking |QRS
|complexes. |Here, |the |aberrant |beat |lacks |a |preceding |P |wave |and |is |wide.
• Normal |sinus |rhythm |(C): |Normal |rhythm |would |not |include |premature |or |ectopic |beats.
• Sinus |tachycardia |(A): |Although |the |overall |rhythm |is |not |slow, |the |rate |is |not |fast |enough |to |be
Page || | |considered |tachycardia |(>100 |bpm), |and |the |irregular |beat |does |not |align |with |a |tachycardic |pattern.
2
PVCs |are |common |and |may |be |benign |or |related |to |underlying |cardiac |issues, |especially |if |they |occur
|frequently. |Recognition |is |key |in |telemetry, |med-surg, |and |cardiac |step-down |settings. |Patients |may |experience
|palpitations, |but |often |no |symptoms |are |present. |If |symptomatic |or |frequent, |further |evaluation |may |include
|electrolyte |monitoring, |cardiac |enzymes, |and |ECG.
RATIONAILE
This |ECG |rhythm |strip |clearly |demonstrates |the |characteristics |of |a |second-degree |AV |block, |Type |I, |also
|known |as |Mobitz |I |or |Wenckebach |phenomenon. |In |this |type |of |block, |the |PR |interval |progressively
|lengthens |with |each |successive |beat |until |a |P |wave |is |not |followed |by |a |QRS |complex |— |this |is |the |key
|diagnostic |hallmark.
If |you |closely |observe |this |strip:
• The |P |waves |are |present |and |consistent.
• The |PR |intervals |get |longer |and |longer, |beat |by |beat.
• Eventually, |a |QRS |complex |is |dropped |(you’ll |see |a |P |wave |that |isn’t |followed |by |a |QRS), |and |then |the
|cycle |repeats.
This |progressive |conduction |delay |occurs |at |the |level |of |the |AV |node, |which |temporarily |fails |to |conduct |the
|impulse |to |the |ventricles. |After |the |dropped |beat, |the |cycle |resets.
, Here’s |how |this |rhythm |differs |from |other |choices:
• A. |3rd |degree |heart |block: |This |shows |complete |dissociation |between |atrial |and |ventricular |activity.
|There’s |no |relationship |between |P |waves |and |QRS |— |which |is |not |the |case |here.
• C. |Sinus |bradycardia: |A |slow |but |regular |rhythm |with |consistent |PR |intervals |and |one |P |for |each |QRS
|— |there’s |no |dropped |beat |or |PR |variation.
Page || | • D. |Sinus |rhythm |with |1st |degree |AV |block: |This |would |show |a |consistently |prolonged |PR |interval
3 |(>0.20 |seconds), |but |no |dropped |QRS |complexes.
Mobitz |I |is |often |benign |and |transient, |especially |in |athletes |or |during |sleep, |and |may |not |require |treatment
|unless |symptomatic |(e.g., |syncope, |dizziness). |Monitoring |is |key, |and |atropine |may |be |considered |if
|symptomatic |bradycardia |is |present.
Page || |
1
Questions with Verified Answers + Diagrams | A+
Scored Pack
QUESTION |1
Rationale:
The |rhythm |strip |presented |displays |an |overall |regular |sinus |rhythm |with |one |early, |wide, |and |bizarre |QRS
|complex |that |interrupts |the |normal |pattern. |This |aberrant |complex |is |not |preceded |by |a |P |wave, |and |it |has |a
|duration |significantly |longer |than |the |surrounding |QRS |complexes |— |a |hallmark |feature |of |a |premature
|ventricular |contraction |(PVC).
In |normal |sinus |rhythm, |each |QRS |complex |follows |a |P |wave |at |regular |intervals, |and |the |morphology |is
|uniform. |However, |in |this |strip, |one |QRS |complex |appears |prematurely |and |does |not |follow |the |same |shape |or
|duration |as |the |others, |indicating |that |it |originates |from |the |ventricles |rather |than |the |atria.
, This |distinguishes |the |rhythm |from:
• Sinus |rhythm |with |PAC |(D): |PACs |have |premature |P |waves |followed |by |normal-looking |QRS
|complexes. |Here, |the |aberrant |beat |lacks |a |preceding |P |wave |and |is |wide.
• Normal |sinus |rhythm |(C): |Normal |rhythm |would |not |include |premature |or |ectopic |beats.
• Sinus |tachycardia |(A): |Although |the |overall |rhythm |is |not |slow, |the |rate |is |not |fast |enough |to |be
Page || | |considered |tachycardia |(>100 |bpm), |and |the |irregular |beat |does |not |align |with |a |tachycardic |pattern.
2
PVCs |are |common |and |may |be |benign |or |related |to |underlying |cardiac |issues, |especially |if |they |occur
|frequently. |Recognition |is |key |in |telemetry, |med-surg, |and |cardiac |step-down |settings. |Patients |may |experience
|palpitations, |but |often |no |symptoms |are |present. |If |symptomatic |or |frequent, |further |evaluation |may |include
|electrolyte |monitoring, |cardiac |enzymes, |and |ECG.
RATIONAILE
This |ECG |rhythm |strip |clearly |demonstrates |the |characteristics |of |a |second-degree |AV |block, |Type |I, |also
|known |as |Mobitz |I |or |Wenckebach |phenomenon. |In |this |type |of |block, |the |PR |interval |progressively
|lengthens |with |each |successive |beat |until |a |P |wave |is |not |followed |by |a |QRS |complex |— |this |is |the |key
|diagnostic |hallmark.
If |you |closely |observe |this |strip:
• The |P |waves |are |present |and |consistent.
• The |PR |intervals |get |longer |and |longer, |beat |by |beat.
• Eventually, |a |QRS |complex |is |dropped |(you’ll |see |a |P |wave |that |isn’t |followed |by |a |QRS), |and |then |the
|cycle |repeats.
This |progressive |conduction |delay |occurs |at |the |level |of |the |AV |node, |which |temporarily |fails |to |conduct |the
|impulse |to |the |ventricles. |After |the |dropped |beat, |the |cycle |resets.
, Here’s |how |this |rhythm |differs |from |other |choices:
• A. |3rd |degree |heart |block: |This |shows |complete |dissociation |between |atrial |and |ventricular |activity.
|There’s |no |relationship |between |P |waves |and |QRS |— |which |is |not |the |case |here.
• C. |Sinus |bradycardia: |A |slow |but |regular |rhythm |with |consistent |PR |intervals |and |one |P |for |each |QRS
|— |there’s |no |dropped |beat |or |PR |variation.
Page || | • D. |Sinus |rhythm |with |1st |degree |AV |block: |This |would |show |a |consistently |prolonged |PR |interval
3 |(>0.20 |seconds), |but |no |dropped |QRS |complexes.
Mobitz |I |is |often |benign |and |transient, |especially |in |athletes |or |during |sleep, |and |may |not |require |treatment
|unless |symptomatic |(e.g., |syncope, |dizziness). |Monitoring |is |key, |and |atropine |may |be |considered |if
|symptomatic |bradycardia |is |present.
