IBHRE - International Board of Heart Rhythm Examiners Arrhythmia Interpretation and Diagnosis Questions and Answers — Questions and Answers
Question 1: A 65-year-old male with a history of myocardial infarction presents with a regular, wide complex tachycardia at 150 bpm. The ECG shows a QRS duration of 160 ms, a northwest axis, and evidence of AV dissociation. In lead V1, there is a monophasic R wave. Which of the following is the most likely diagnosis?
- Supraventricular tachycardia with aberrancy
- Atrial flutter with a bundle branch block
- Ventricular tachycardia (Correct answer)
- Antidromic atrioventricular reentrant tachycardia
Correct answer: Ventricular tachycardia
Ventricular tachycardia (VT) is the most likely diagnosis. Several features in the description strongly suggest VT over a supraventricular rhythm with aberrancy. These include a history of structural heart disease (prior MI), QRS duration >140 ms, a northwest axis (extreme axis deviation), and the presence of AV dissociation. A monophasic R wave in V1 is also a classic morphological criterion for VT.
Question 2: A 58-year-old patient presents to the clinic for a follow-up visit. They mention having intermittent, crushing chest pain over the past week, but are currently pain-free. The ECG shows deeply inverted, symmetric T-waves in leads V2 and V3, with minimal (<1mm) ST-segment elevation and preserved R-wave progression. What is the most likely diagnosis?
- Brugada syndrome
- Wellens' syndrome (Correct answer)
- Acute pericarditis
- Left ventricular hypertrophy with strain
Correct answer: Wellens' syndrome
The ECG findings described are characteristic of Wellens' syndrome (specifically Type B). This pattern, often seen when the patient is pain-free, is highly specific for a critical, proximal stenosis of the left anterior descending (LAD) artery and indicates a high risk of an impending large anterior wall myocardial infarction.
Question 3: Which of the following ECG findings is the defining characteristic of a Mobitz Type II second-degree atrioventricular block?
- Progressive prolongation of the PR interval until a QRS complex is dropped.
- A constant PR interval in all conducted beats before an unexpected, non-conducted P-wave. (Correct answer)
- Complete dissociation between P-waves and QRS complexes.
- A PR interval that is consistently greater than 200 ms.
Correct answer: A constant PR interval in all conducted beats before an unexpected, non-conducted P-wave.
Mobitz Type II second-degree AV block is characterized by a constant and unchanging PR interval in the conducted beats preceding a suddenly dropped QRS complex (a non-conducted P-wave). Unlike Mobitz Type I (Wenckebach), there is no progressive lengthening of the PR interval. This type of block is typically located in the His-Purkinje system and carries a higher risk of progressing to complete heart block.
Question 4: A patient with a dual-chamber pacemaker presents with palpitations. Device interrogation reveals a tachycardia with a ventricular paced rate at the programmed upper tracking rate. The intracardiac electrogram shows a consistent 1:1 ventriculoatrial (VA) conduction pattern where a ventricular paced event is followed by a retrograde atrial sensed event, which then triggers the next ventricular paced event. What is the most likely diagnosis?
- Atrial fibrillation with rapid ventricular response
- Sensor-indicated tachycardia
- Runaway pacemaker
- Pacemaker-mediated tachycardia (PMT) (Correct answer)
Correct answer: Pacemaker-mediated tachycardia (PMT)
This scenario describes a classic endless loop or pacemaker-mediated tachycardia (PMT). PMT is a reentrant arrhythmia where the pacemaker forms the antegrade limb (atrial sensing to ventricular pacing) and the patient's native conduction system provides the retrograde limb (ventricle to atrium). The cycle of V-pace -> retrograde P-wave -> A-sense -> V-pace maintains the tachycardia.
Question 5: Which of the following ECG findings is considered the only potentially diagnostic pattern for Brugada syndrome without provocative testing?
- Saddleback-shaped ST-segment elevation of ≥2 mm in V1-V2.
- Coved-type ST-segment elevation of ≥2 mm in at least one right precordial lead (V1-V3) followed by a negative T-wave. (Correct answer)
- Deeply inverted T-waves in leads V2-V3 with preserved R-wave progression.
- ST-segment elevation >1 mm in leads II, III, and aVF.
Correct answer: Coved-type ST-segment elevation of ≥2 mm in at least one right precordial lead (V1-V3) followed by a negative T-wave.
The Type 1 Brugada pattern is the only ECG finding considered diagnostic of Brugada Syndrome when associated with clinical criteria (e.g., syncope, family history of sudden death). It is defined by a coved-type ST-segment elevation of 2 mm or more in at least one of the right precordial leads (V1, V2, or V3), followed by a negative or biphasic T-wave.
Question 6: In analyzing a narrow complex tachycardia, which of the following findings would most strongly favor a diagnosis of typical atrioventricular nodal reentrant tachycardia (AVNRT) over orthodromic atrioventricular reentrant tachycardia (AVRT)?
- A long RP interval where the P-wave is clearly visible in the ST segment.
- The presence of QRS alternans.
- A visible retrograde P-wave (pseudo r' in V1 or pseudo S in inferior leads) immediately following the QRS complex, resulting in a short RP interval. (Correct answer)
- Initiation of the tachycardia by a premature ventricular contraction.
Correct answer: A visible retrograde P-wave (pseudo r' in V1 or pseudo S in inferior leads) immediately following the QRS complex, resulting in a short RP interval.
Typical (slow-fast) AVNRT involves near-simultaneous activation of the atria and ventricles. This results in the retrograde P-wave being buried within the QRS complex or appearing just at the end of it, creating a very short RP interval (often <70-90 ms). This can manifest as a 'pseudo r' wave' in V1 or a 'pseudo S wave' in the inferior leads. In contrast, orthodromic AVRT involves a larger reentry circuit, typically leading to a longer RP interval.
IBHRE - International Board of Heart Rhythm Examiners Arrhythmia Interpretation and Diagnosis Questions and Answers
A 65-year-old male with a history of myocardial infarction presents with a regular, wide complex tachycardia at 150 bpm.
The ECG shows a QRS duration of 160 ms, a northwest axis, and evidence of AV dissociation.
In lead V1, there is a monophasic R wave.
Which of the following is the most likely diagnosis?