Examkin

Question

Difficulty: HardCardiovascular System

A 65-year-old woman is evaluated in the emergency department due to a two-day history of progressively worsening shortness of breath, a cough productive of yellow sputum, and a sensation of a racing heartbeat. Her medical history includes chronic obstructive pulmonary disease (COPD) and essential hypertension. Her daily home medications include an inhaled long-acting muscarinic antagonist and a low-dose thiazide diuretic. Vital signs show a temperature of 37.5°C (99.5°F), blood pressure of 132/84 mmHg, pulse of 128/min, and respiratory rate of 24/min. Pulse oximetry on room air is 88%. Physical examination reveals a prolonged expiratory phase with diffuse bilateral expiratory wheezing, but no inspiratory crackles. The jugular venous pressure is 8 cm H2O. Cardiac auscultation reveals an irregularly irregular rhythm with a loud P2, but no S3 gallop or murmurs are appreciated. Trace bilateral lower extremity edema is present. An electrocardiogram demonstrates a narrow QRS complex tachycardia with an irregular R-R interval, varying PR intervals, and three distinct P-wave morphologies in lead II. Which of the following is the most appropriate initial management for this patient's condition?

  1. Nebulized albuterol and supplemental oxygenAnswer
  2. B
    Intravenous bumetanide
  3. C
    Intravenous metoprolol
  4. D
    Intravenous nitroglycerin
  5. E
    Synchronized direct current cardioversion

Answer

Nebulized albuterol and supplemental oxygen
The most appropriate initial management is to treat the underlying cause of the arrhythmia. The patient's electrocardiogram shows multifocal atrial tachycardia (MAT), characterized by an irregularly irregular rhythm, varying PR intervals, and at least three distinct P-wave morphologies in a single lead. MAT is most commonly triggered by an exacerbation of underlying pulmonary disease, such as COPD, leading to hypoxia and right heart strain. Therefore, the gold standard of treatment is optimizing pulmonary function with bronchodilators and supplemental oxygen. Once the hypoxemia and airway resistance improve, the MAT typically resolves spontaneously.

Step-by-Step Solution

1
Interpret the physical exam and vital signs.
The patient is hypoxic (88%) with diffuse wheezing, a prolonged expiratory phase, and no crackles or S3, indicating an acute COPD exacerbation rather than acute decompensated heart failure.
Differentiating between pulmonary and cardiac causes of dyspnea is critical for avoiding contraindicated therapies like diuretics or beta-blockers in acute bronchospasm.
2
Analyze the electrocardiogram findings.
An irregularly irregular narrow QRS tachycardia with at least three distinct P-wave morphologies and varying PR intervals confirms the diagnosis of multifocal atrial tachycardia (MAT).
MAT must be differentiated from atrial fibrillation, which lacks distinct P waves, because their management strategies differ significantly.
3
Determine the next best step in management for MAT.
Select therapy that treats the underlying cause (COPD exacerbation) using bronchodilators and oxygen, rather than primary antiarrhythmic medications.
MAT is secondary to underlying conditions (most commonly hypoxia, hypercapnia, and pulmonary hypertension from COPD). Direct cardiac interventions are often ineffective and can be harmful.

Key Concept

Management of multifocal atrial tachycardia (MAT) centers on treating the underlying respiratory condition (e.g., COPD exacerbation) with bronchodilators and oxygen, rather than using direct antiarrhythmic agents.
Rate this question

Topics

Cardiovascular System

More questions from this topic