Dysrhythmia Cardiac Rhythm Interpretation 1 — Questions and Answers
Question 1: What is the defining characteristic of atrial fibrillation on an ECG?
- Regular R-R intervals with distinct P waves
- Irregularly irregular rhythm with no P waves (Correct answer)
- Sawtooth pattern P waves
- Wide QRS complexes without P waves
Correct answer: Irregularly irregular rhythm with no P waves
Atrial fibrillation (AFib) is definitively characterized on an ECG by an 'irregularly irregular' ventricular rhythm and the absence of distinct, organized P waves. Instead of clear P waves, chaotic fibrillatory waves are often seen, reflecting the uncoordinated electrical activity within the atria. This distinct pattern helps differentiate AFib from other arrhythmias.
Question 2: Which cardiac rhythm is characterized by a prolonged PR interval greater than 0.20 seconds?
- Atrial Flutter
- First-degree AV Block (Correct answer)
- Ventricular Tachycardia
- Complete Heart Block
Correct answer: First-degree AV Block
First-degree AV block is characterized by a consistent prolongation of the PR interval beyond the normal upper limit of 0.20 seconds. This indicates a delay in electrical conduction from the atria to the ventricles through the AV node, but every atrial impulse still reaches the ventricles. The prolonged PR interval is the defining diagnostic criterion for this specific type of heart block.
Question 3: What is the key ECG feature of ventricular tachycardia?
- Narrow QRS complexes with P waves
- Wide QRS complexes with a fast rate (Correct answer)
- Irregularly irregular rhythm
- Slow heart rate with ST elevation
Correct answer: Wide QRS complexes with a fast rate
Ventricular tachycardia (VT) originates from the ventricles, leading to abnormal, wide QRS complexes (typically >0.12 seconds) as ventricular depolarization is delayed. The 'tachycardia' aspect means the heart rate is fast, usually between 100-250 bpm. This combination of wide QRS and a rapid rate is the hallmark ECG feature distinguishing VT from supraventricular tachycardias.
Question 4: Which rhythm is described by a sawtooth pattern of P waves on an ECG?
- Atrial Fibrillation
- Atrial Flutter (Correct answer)
- Sinus Tachycardia
- Ventricular Fibrillation
Correct answer: Atrial Flutter
Atrial flutter is characterized by a rapid, regular atrial rhythm, typically between 250-350 bpm, caused by a re-entrant circuit in the atria. On an ECG, this manifests as distinct, uniform 'flutter waves' that resemble a sawtooth pattern, especially prominent in leads II, III, and aVF. These flutter waves represent the rapid atrial depolarization.
Question 5: Which of the following rhythms is considered a medical emergency due to its lack of cardiac output?
- Sinus Bradycardia
- Atrial Flutter
- Ventricular Fibrillation (Correct answer)
- First-degree AV Block
Correct answer: Ventricular Fibrillation
Ventricular fibrillation (VF) is a chaotic electrical activity in the ventricles that results in ineffective quivering rather than coordinated contractions. This completely prevents the heart from pumping blood, leading to an immediate cessation of cardiac output and collapse. Without immediate defibrillation, VF is rapidly fatal, making it a critical medical emergency.
Question 6: Which rhythm is identified by a complete dissociation between P waves and QRS complexes?
- Second-degree AV Block Type 1
- Second-degree AV Block Type 2
- Complete Heart Block (Correct answer)
- Sinus Arrhythmia
Correct answer: Complete Heart Block
Complete heart block, or third-degree AV block, is defined by a total dissociation between atrial and ventricular electrical activity. The atria and ventricles beat independently, meaning no atrial impulses are conducted through the AV node to the ventricles. On an ECG, this appears as P waves occurring regularly but with no consistent relationship to the QRS complexes, which are generated by an escape rhythm.
Dysrhythmia Cardiac Rhythm Interpretation 1
What is the defining characteristic of atrial fibrillation on an ECG?