Free NCCT EKG Interpretation of Complex Arrhythmias Questions and Answers — Questions and Answers
Question 1: An EKG strip shows an irregularly irregular rhythm with no discernible P waves and a variable ventricular rate. What is the most likely interpretation?
- Atrial Flutter
- Atrial Fibrillation (Correct answer)
- Sinus Tachycardia
- Ventricular Tachycardia
Correct answer: Atrial Fibrillation
Atrial Fibrillation (A-Fib) is characterized by chaotic atrial electrical activity, leading to an irregularly irregular ventricular response and the absence of clear P waves. The baseline may appear chaotic or fibrillatory, which distinguishes it from other rhythms.
Question 2: On an EKG, you observe a progressively lengthening PR interval until a QRS complex is dropped. Which type of AV block is this?
- First-degree AV block
- Second-degree AV block, Mobitz I (Wenckebach) (Correct answer)
- Second-degree AV block, Mobitz II
- Third-degree AV block
Correct answer: Second-degree AV block, Mobitz I (Wenckebach)
Mobitz I, also known as the Wenckebach phenomenon, is a type of second-degree AV block where there is a progressive delay in AV conduction. This is seen on the EKG as a PR interval that gets longer with each beat until a QRS complex is completely blocked or 'dropped'.
Question 3: A patient's EKG shows a rapid, wide-complex tachycardia with a regular rhythm. What is the most likely life-threatening arrhythmia?
- Atrial Fibrillation with RVR
- Supraventricular Tachycardia (SVT)
- Ventricular Tachycardia (V-Tach) (Correct answer)
- Sinus Bradycardia
Correct answer: Ventricular Tachycardia (V-Tach)
Ventricular Tachycardia (V-Tach) is a life-threatening arrhythmia characterized by a rapid heart rate (typically >100 bpm) and wide QRS complexes (>0.12 seconds). It originates in the ventricles and can quickly lead to cardiac arrest if the patient is unstable or pulseless.
Question 4: Which EKG finding is the hallmark of a third-degree (complete) heart block?
- A constant PR interval that is longer than 0.20 seconds
- Progressively lengthening PR interval with dropped QRS complexes
- Complete dissociation between P waves and QRS complexes (Correct answer)
- A 'sawtooth' pattern of P waves
Correct answer: Complete dissociation between P waves and QRS complexes
In a third-degree AV block, there is no electrical communication between the atria and ventricles. The atria (P waves) and ventricles (QRS complexes) beat independently of each other, resulting in a complete AV dissociation where there is no consistent relationship between P waves and QRS complexes.
Question 5: An EKG strip displays a regular rhythm with a ventricular rate of 75 bpm. The atrial rate is 300 bpm, and the baseline has a distinct 'sawtooth' appearance. What is this rhythm?
- Atrial Fibrillation
- Atrial Flutter (Correct answer)
- Sinus Tachycardia
- Junctional Rhythm
Correct answer: Atrial Flutter
Atrial Flutter is caused by a re-entrant circuit in the atria, creating rapid, regular atrial depolarizations (flutter waves) that often resemble the teeth of a saw. Not all atrial impulses conduct to the ventricles, resulting in an AV block (e.g., a 4:1 block in this case, 300/75).
Question 6: What EKG characteristic best describes a Premature Ventricular Contraction (PVC)?
- A narrow QRS complex that occurs earlier than expected
- A wide, bizarre-looking QRS complex that occurs early, not preceded by a P wave (Correct answer)
- An inverted P wave preceding a narrow QRS complex
- A dropped QRS complex following a normal P wave
Correct answer: A wide, bizarre-looking QRS complex that occurs early, not preceded by a P wave
A PVC is an ectopic beat originating from an irritable focus within the ventricles. This results in a premature, wide (>0.12s), and oddly shaped QRS complex because the impulse does not follow the normal conduction pathway. It is not preceded by a P wave and is typically followed by a compensatory pause.
Question 7: An EKG shows a regular rhythm at a rate of 50 bpm. The QRS complexes are narrow, but P waves are absent or inverted. This rhythm most likely originates from the:
- Sinoatrial (SA) node
- Atrioventricular (AV) junction (Correct answer)
- Ventricles
- Atrial tissue
Correct answer: Atrioventricular (AV) junction
A junctional escape rhythm occurs when the SA node fails to fire, and the AV junction takes over as the pacemaker. Its intrinsic rate is 40-60 bpm, and because the impulse originates in the AV junction, P waves are either absent, inverted (due to retrograde conduction), or buried within the QRS.
Free NCCT EKG Interpretation of Complex Arrhythmias Questions and Answers
An EKG strip shows an irregularly irregular rhythm with no discernible P waves and a variable ventricular rate.
What is the most likely interpretation?