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Zorluk: ZorCardiovascular System

Paramedics bring a 26-year-old male to the emergency room following the sudden onset of profound palpitations and dizziness while jogging. The symptoms began approximately 4545 minutes prior to arrival. He has no significant past medical history and takes no medications, though he recalls a prior physician mentioning a "unique heart pattern" during a sports physical years ago. On physical examination, the patient is anxious but fully alert and oriented. His temperature is 36.8∘36.8^\circ C (98.2∘98.2^\circ F), blood pressure is 118/74118/74 mm Hg, and respiratory rate is 1616/min. Cardiac auscultation reveals a tachycardic, irregularly irregular rhythm without murmurs. The lungs are clear.

A 12-lead electrocardiogram demonstrates an irregularly irregular rhythm with a ventricular rate varying between 160160 and 210210/min. The QRS complexes are widened (0.150.15 seconds) and exhibit variable morphology from beat to beat. No distinct P waves are observed. A review of his electronic medical record reveals a baseline electrocardiogram from three years ago showing a PR interval of 0.100.10 seconds and a slurred, broad upstroke of the QRS complex.

Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Administration of intravenous adenosine
  2. B
    Administration of intravenous diltiazem
  3. Administration of intravenous procainamideCevap
  4. D
    Administration of intravenous amiodarone
  5. E
    Synchronized direct current cardioversion

Cevap

Administration of intravenous procainamide is the most appropriate next step in management.
The patient's clinical presentation of an irregularly irregular, wide-complex tachycardia with variable QRS morphologies, paired with a history of a short PR interval and a delta wave, is classic for atrial fibrillation occurring in the setting of Wolff-Parkinson-White (WPW) syndrome. Because the patient is hemodynamically stable (alert with a normal blood pressure of 118/74 mm Hg), the treatment of choice is chemical cardioversion using an agent that prolongs the refractory period of the accessory pathway. Intravenous procainamide is the preferred agent in this scenario.

Adım Adım Çözüm

1
Diagnose the underlying baseline cardiac condition from the prior electrocardiogram findings.
The short PR interval and slurred QRS upstroke (delta wave) clearly indicate Wolff-Parkinson-White (WPW) syndrome.
These findings are pathognomonic for the presence of an anomalous accessory electrical pathway (Bundle of Kent) connecting the atria and ventricles.
2
Interpret the current acute electrocardiogram.
An irregularly irregular rhythm with variable, wide QRS complexes at a highly rapid rate indicates atrial fibrillation with pre-excitation.
The atrial fibrillation impulses conduct down both the normal AV node and the accessory pathway, leading to a variable degree of QRS widening and an unusually rapid ventricular response.
3
Assess the patient's current hemodynamic status to guide intervention.
The patient is alert, oriented, and normotensive with a blood pressure of 118/74 mm Hg, indicating he is hemodynamically stable.
Hemodynamic stability determines whether immediate electrical intervention or medical therapy is indicated.
4
Select the appropriate pharmacological therapy while avoiding contraindicated agents.
Intravenous procainamide is selected because it targets the accessory pathway. AV nodal blockers must be strictly avoided.
AV nodal blockers prevent conduction through the normal pathway, driving all disorganized atrial impulses through the accessory pathway and risking degeneration into ventricular fibrillation.

Anahtar Kavram

Hemodynamically stable patients with pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome) require chemical cardioversion with rhythm control agents that target the accessory pathway, such as procainamide. AV nodal blocking agents are strictly contraindicated.
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Cardiovascular System

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