A 38-year-old male presents with sudden onset palpitations. He has no known comorbidities and his vitals are stable. ECG shows an irregularly irregular rhythm with no identifiable P waves and a ventricular rate of 130 beats per minute. What is the most likely diagnosis?

1. A

   A. Multifocal atrial tachycardia

2. B

   B. Atrial fibrillation

3. C

   C. Atrial flutter

4. D

   D. Supraventricular tachycardia

Appeared in: INI-CET EXAM -2026

Explanation

• The patient's ECG shows an 'irregularly irregular rhythm,' which is a hallmark of Atrial Fibrillation (AFib).
• The absence of identifiable P waves, replaced by chaotic fibrillatory waves, confirms that the atria are not contracting in a coordinated manner.
• The ventricular rate of 130 bpm is a rapid ventricular response (RVR) to the chaotic atrial signals, which is common in untreated AFib.
• These three findings together—irregularly irregular rhythm, no P waves, and a rapid ventricular rate—are the classic triad for diagnosing Atrial Fibrillation.

Why Other Options Were Wrong

• Option A: Multifocal atrial tachycardia (MAT) is characterized by the presence of at least three different P-wave morphologies. The patient's ECG has no identifiable P waves.
• Option C: Atrial flutter typically presents with a regular (or sometimes predictably irregular) ventricular rhythm and characteristic 'sawtooth' flutter waves instead of P waves. The patient's rhythm is irregularly irregular.
• Option D: Supraventricular tachycardia (SVT) is a broad term, but it most often refers to arrhythmias like AVNRT which are characterized by a regular, rapid rhythm. The patient's rhythm is distinctly irregular.

Related Visual

Clinical Relevance

• Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing ECG Interpretation of Cardiac Arrhythmias in acute care settings.
• Prompt identification of Atrial Fibrillation is critical due to the increased risk of thromboembolism and stroke. The quivering atria allow blood to stagnate, promoting clot formation.
• Management priorities for a stable patient with new-onset AFib include controlling the ventricular rate (rate control) and assessing the need for anticoagulation to prevent stroke.
• What if the patient was hemodynamically unstable (e.g., hypotensive, altered mental status, signs of shock)? The priority would shift from rate control to immediate synchronized cardioversion to restore a stable rhythm.

How to Approach the Question

• First, analyze the keywords in the clinical scenario: 'sudden onset palpitations,' 'irregularly irregular rhythm,' 'no identifiable P waves,' and a rate of 130 bpm.
• Systematically evaluate the rhythm. The term 'irregularly irregular' is a powerful clue that strongly points towards Atrial Fibrillation.
• Next, look for P waves. The description 'no identifiable P waves' rules out rhythms where P waves are present, such as sinus tachycardia or multifocal atrial tachycardia.
• Consider the remaining options. Atrial flutter has flutter waves (sawtooth pattern) and is often regular. SVT is typically a regular rhythm.
• Synthesize the findings: The combination of an irregularly irregular rhythm and absent P waves is the classic definition of Atrial Fibrillation. The rate of 130 bpm is consistent with AFib with a rapid ventricular response.

Concept Tested & Keywords

• Concept Tested: ECG Interpretation of Cardiac Arrhythmias
• Stem keywords: palpitations, ECG, irregularly irregular rhythm, no identifiable P waves, ventricular rate 130
• Lead-in keywords: most likely diagnosis
• Clinical cues: The combination of 'irregularly irregular rhythm' and 'no identifiable P waves' is a classic descriptor for Atrial Fibrillation.

Question ID

QBjDElNlOJtyUUoUYUADp5

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 1 p. 1987-1989

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 641-643

E6 Pharmacology Nursing Lilley 11e Part 2 p. 86-88