- What is the most likely diagnosis?
Answer: Ventricular tachycardia
In an older patient with structural heart disease (prior MI), any wide-complex tachycardia should be considered ventricular tachycardia (VT) until proven otherwise. While SVT with aberrancy is a possibility, VT is far more common and life-threatening in this clinical context. Atrial flutter would typically have a narrow QRS unless there is a pre-existing bundle branch block. Torsades de pointes is a polymorphic VT, which would appear as an irregular rhythm with varying QRS morphology, unlike the regular rhythm described.
- What is the most likely arrhythmia?
Answer: Multifocal atrial tachycardia (MAT)
The presence of a tachycardic rhythm (rate >100/min) with at least three different P-wave morphologies, varying PR intervals, and an irregular rhythm is the definition of multifocal atrial tachycardia (MAT). MAT is strongly associated with severe pulmonary disease, such as a COPD exacerbation. While atrial fibrillation is also irregularly irregular, it has no discernible P waves. Atrial flutter would show characteristic 'sawtooth' flutter waves. Sinus tachycardia with PACs would have a dominant, consistent sinus P-wave morphology.
- Which of the following is the most appropriate initial step in management?
Answer: Carotid sinus massage
This hemodynamically stable patient presents with a supraventricular tachycardia (SVT), most likely AVNRT. The initial management for stable SVT should be vagal maneuvers, such as carotid sinus massage or the Valsalva maneuver. If these are unsuccessful, intravenous adenosine is the next step. Diltiazem is a second-line pharmacologic agent. Synchronized cardioversion is reserved for hemodynamically unstable patients.
- What is the most likely diagnosis?
Answer: Third-degree (complete) AV block
The ECG findings describe complete atrioventricular (AV) dissociation, where the atria (P waves at 90/min) and ventricles (QRS complexes at 40/min) are beating independently. This is the definition of third-degree, or complete, AV block. The narrow QRS indicates the escape rhythm is originating from the AV junction. Mobitz II would show some relationship between P waves and QRS complexes (e.g., 2:1 or 3:1 block). Sick sinus syndrome can cause bradycardia but not necessarily complete AV dissociation.
- In addition to defibrillation and CPR, which of the following is the most appropriate immediate pharmacologic treatment?
Answer: Intravenous magnesium sulfate
The patient has developed torsades de pointes (TdP), a polymorphic ventricular tachycardia occurring in the setting of a prolonged QT interval. Her alcoholism and malnutrition put her at risk for electrolyte abnormalities like hypomagnesemia and hypokalemia, common causes of QT prolongation. The first-line treatment for TdP (both stable and unstable) is intravenous magnesium sulfate, which helps stabilize the cardiac membrane. Amiodarone can further prolong the QT interval and should be avoided. Calcium is for hyperkalemia, and bicarbonate is for specific toxicities or acidosis.
- Which of the following medications should be avoided in this patient?
Answer: Adenosine
This patient has atrial fibrillation with rapid conduction down an accessory pathway, a life-threatening arrhythmia in WPW syndrome. Administering AV nodal blocking agents (such as adenosine, beta-blockers, calcium channel blockers, or digoxin) is contraindicated because blocking the normal AV pathway can lead to preferential and extremely rapid conduction down the accessory pathway, potentially degenerating into ventricular fibrillation. The treatment of choice for a stable patient is an antiarrhythmic like procainamide or ibutilide. If the patient were unstable, synchronized cardioversion would be appropriate.
- In addition to his current medications, which of the following is indicated to reduce his risk of sudden cardiac death?
Answer: Implantable cardioverter-defibrillator (ICD)
An implantable cardioverter-defibrillator (ICD) is indicated for primary prevention of sudden cardiac death in patients with ischemic cardiomyopathy, an LVEF ≤35%, and NYHA class II or III symptoms, provided they are at least 40 days post-MI and are on optimal medical therapy. A pacemaker is for bradyarrhythmias. Prophylactic amiodarone has not been shown to improve survival in this population and has significant side effects. Bypass grafting is for revascularization and would have been considered earlier if appropriate.
- Which of the following is the most likely diagnosis?
Answer: Second-degree AV block, Mobitz type I
The ECG finding of progressive PR interval prolongation followed by a non-conducted P wave ('dropped beat') is the classic description of second-degree AV block, Mobitz type I (also known as Wenckebach phenomenon). First-degree AV block involves a constantly prolonged PR interval with no dropped beats. Mobitz type II involves dropped beats without preceding PR prolongation. Third-degree AV block involves complete dissociation between P waves and QRS complexes.
- What is the most appropriate immediate next step in management?
Answer: Prepare for transcutaneous pacing
This patient has symptomatic, high-degree AV block causing hemodynamic instability (hypotension, altered mental status). The immediate priority is to increase the heart rate and restore cardiac output. Transcutaneous pacing is the fastest and most reliable method to achieve this in an unstable patient. Atropine is unlikely to be effective for a high-degree (infranodal) block and should not delay more definitive therapy. While a permanent pacemaker will be needed, it is not the immediate intervention. Vasopressors like dopamine can be used as a bridge but pacing is the primary treatment.
- What is the most appropriate next step in management?
Answer: Permanent pacemaker implantation
The ECG describes second-degree AV block, Mobitz type II, characterized by intermittent non-conducted P waves with a constant PR interval in the conducted beats (no gradual PR prolongation before the dropped beat). Mobitz type II block is considered high-risk because it occurs below the AV node (infranodal) and can unpredictably progress to complete heart block and asystole. Therefore, a permanent pacemaker is indicated, even in asymptomatic patients. Reassurance is inappropriate due to the high risk of progression. Atropine is not a long-term solution. Stress testing is not indicated and could be dangerous.
- What is the most likely diagnosis?
Answer: Atrioventricular nodal reentrant tachycardia (AVNRT)
The patient's presentation of sudden-onset palpitations with a regular, narrow-complex tachycardia at a rate of 170/min and absent P waves is classic for atrioventricular nodal reentrant tachycardia (AVNRT), a type of supraventricular tachycardia. Atrial fibrillation would be irregularly irregular. Ventricular tachycardia would typically show a wide QRS complex. Sinus tachycardia is a physiologic response and would have visible P waves preceding each QRS complex.
- What is the most appropriate next step in her management?
Answer: Pursue a rhythm-control strategy
This patient remains highly symptomatic from her atrial fibrillation despite adequate rate control. In such cases, especially in a younger, active individual, a rhythm-control strategy is indicated to improve symptoms and quality of life. Options for rhythm control include antiarrhythmic medications (e.g., flecainide, amiodarone) or catheter ablation. Simply increasing the beta-blocker or adding digoxin would further control the rate but is unlikely to resolve symptoms that are due to the loss of sinus rhythm itself. Reassurance is inappropriate given her functional impairment.
- These ECG findings are most characteristic of which underlying condition?
Answer: Wolff-Parkinson-White (WPW) syndrome
The combination of a short PR interval (<120 ms) and a slurred upstroke of the QRS complex, known as a 'delta wave,' is the pathognomonic ECG finding for Wolff-Parkinson-White (WPW) syndrome. This pattern is caused by pre-excitation of the ventricles via an accessory pathway that bypasses the AV node. Brugada syndrome has a characteristic coved ST-segment elevation in V1-V2. Long QT syndrome is defined by a prolonged QT interval. Hypertrophic cardiomyopathy may show signs of left ventricular hypertrophy but not a short PR and delta wave.
- Which of the following is the most appropriate immediate intervention?
Answer: Synchronized cardioversion
The patient is in atrial fibrillation with rapid ventricular response and is hemodynamically unstable, as evidenced by hypotension, signs of shock (cool extremities, diaphoresis), altered mental status (confusion), and acute heart failure (pulmonary edema). The immediate priority is to restore a stable rhythm and improve cardiac output. Therefore, urgent synchronized cardioversion is indicated. Pharmacologic rate or rhythm control (amiodarone, diltiazem) is too slow for an unstable patient. Anticoagulation with heparin is important but is not the immediate life-saving intervention.
- Which of the following is the most appropriate long-term treatment for this patient?
Answer: Permanent pacemaker implantation
This patient has symptomatic bradycardia (syncope) directly attributable to his low heart rate (sinus bradycardia). This is a clear indication for a permanent pacemaker to prevent further syncopal episodes and improve his quality of life. Atropine is used for acute, not chronic, management. An ICD is indicated for preventing sudden death from tachyarrhythmias, not for treating bradycardia. Since the cause of his syncope has been identified on the ECG, further monitoring with an event monitor is unnecessary before intervention.
- Which of the following best describes the approach to stroke prevention in this patient?
Answer: Stroke risk and anticoagulation indications are the same as for atrial fibrillation.
Atrial flutter carries a similar thromboembolic risk to atrial fibrillation. Therefore, the management of stroke prevention is identical. The decision to initiate anticoagulation should be based on the CHA2DS2-VASc score, regardless of whether the arrhythmia is atrial flutter or atrial fibrillation. The ventricular rate and future plans for ablation do not change the need for risk stratification and appropriate anticoagulation.
- Which of the following is the most appropriate long-term management to prevent a recurrence?
Answer: Implantable cardioverter-defibrillator (ICD)
This patient survived a cardiac arrest due to ventricular fibrillation not associated with a transient or reversible cause (like an acute MI or electrolyte disturbance). This constitutes a clear indication for secondary prevention of sudden cardiac death. An implantable cardioverter-defibrillator (ICD) is the standard of care and has been proven to improve survival in these patients. While antiarrhythmic drugs like amiodarone may be used as adjunctive therapy, they are not a substitute for an ICD. A pacemaker would not treat a tachyarrhythmia.
- Which of the following is the most appropriate initial pharmacologic treatment?
Answer: Intravenous amiodarone
For a hemodynamically stable patient with monomorphic ventricular tachycardia, the first-line treatment is an intravenous antiarrhythmic agent. Amiodarone is a preferred agent according to ACLS guidelines. Procainamide or sotalol are also options. Adenosine is used for diagnosing and treating supraventricular tachycardia, not VT. Magnesium sulfate is the treatment of choice for torsades de pointes (polymorphic VT). Verapamil (a calcium channel blocker) is contraindicated in wide-complex tachycardias of unknown origin as it can cause hemodynamic collapse if the rhythm is VT.
- What is the most appropriate long-term management strategy for his arrhythmia?
Answer: Rate control
In an elderly, minimally symptomatic patient with persistent atrial fibrillation, a rate-control strategy is generally preferred and has been shown to have non-inferior outcomes compared to a rhythm-control strategy regarding mortality and stroke risk. Rhythm control strategies (e.g., antiarrhythmic drugs like amiodarone, or catheter ablation) are associated with more side effects and are typically reserved for patients who remain symptomatic despite adequate rate control or in younger patients. Digoxin is primarily used for rate control, not rhythm control.
- Which of the following is the most appropriate long-term therapy to reduce her risk of thromboembolic events?
Answer: Direct oral anticoagulant
This patient's CHA2DS2-VASc score is 4 (Age ≥75=2 points, Hypertension=1 point, Diabetes=1 point). A score of 2 or greater in men or 3 or greater in women is a clear indication for long-term oral anticoagulation. Direct oral anticoagulants (e.g., apixaban, rivaroxaban) or warfarin are recommended over antiplatelet agents like aspirin or clopidogrel, which are less effective for stroke prevention in atrial fibrillation. No therapy would leave her at significant risk for stroke.
