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Difficulty: HardCardiovascular System

A 34-year-old woman presents to the emergency department complaining of a sudden-onset "racing heart" and mild palpitations that began 30 minutes ago. She has no significant past medical history and takes no medications. On evaluation, she is alert, oriented, and conversing comfortably. Her blood pressure is 118/76 mmHg, pulse is 185/min, and respiratory rate is 18/min. Cardiopulmonary examination is otherwise unremarkable, with clear lungs and no murmurs. An electrocardiogram reveals a regular, narrow-complex tachycardia at a rate of 185/min with no discernible P waves. Assuming the patient's hemodynamic status remains stable but the arrhythmia is refractory to each successive intervention, arrange the following management steps in the correct chronological sequence according to standard clinical algorithms.

  1. 1Perform a modified Valsalva maneuver
  2. 2Administer a rapid intravenous push of 6 mg adenosine
  3. 3Administer a rapid intravenous push of 12 mg adenosine
  4. 4Administer an intravenous non-dihydropyridine calcium channel blocker
  5. 5Perform synchronized direct current cardioversion

Answer

The correct sequence for managing stable paroxysmal supraventricular tachycardia (PSVT) is: vagal maneuvers, followed by a 6 mg dose of adenosine, followed by a 12 mg dose of adenosine, followed by an intravenous calcium channel blocker, and finally synchronized cardioversion if the condition is refractory.
The management of a regular, narrow-complex tachycardia (PSVT) in a hemodynamically stable patient strictly follows an escalating algorithmic progression to balance efficacy with patient safety. It must begin with non-invasive vagal maneuvers (e.g., modified Valsalva). If these are unsuccessful, a short-acting AV nodal blocking agent (adenosine) is utilized, strictly starting with a 6 mg rapid intravenous push. If the rhythm fails to convert, a second, larger dose of 12 mg is administered. Continued failure of adenosine prompts the transition to longer-acting, second-line AV nodal blockers such as intravenous diltiazem or metoprolol. Finally, if the patient remains refractory to all medication or acutely decompensates (becomes hemodynamically unstable), synchronized direct current cardioversion is required as the definitive salvage therapy.

Step-by-Step Solution

1
Assess the patient's hemodynamic stability.
The patient is alert, conversing comfortably, and has a normal blood pressure of 118/76 mmHg, indicating a stable presentation.
Hemodynamic stability is the primary branch point in tachycardia algorithms, determining whether to pursue medical management or proceed directly to immediate electrical cardioversion.
2
Interpret the electrocardiogram findings.
A regular, narrow-complex tachycardia without discernible P waves strongly characterizes paroxysmal supraventricular tachycardia (PSVT).
Accurate rhythm identification is necessary to select the appropriate, specific Advanced Cardiovascular Life Support (ACLS) pathway.
3
Determine the stepwise sequence of interventions for stable PSVT.
The algorithm progresses from least invasive (vagal maneuvers) to short-acting pharmacotherapy (adenosine 6 mg, then 12 mg), to longer-acting pharmacotherapy (calcium channel blockers), and finally to procedural intervention (synchronized cardioversion).
This progressive approach minimizes procedural risks and adverse drug side effects while escalating treatment intensity only as dictated by the patient's response.

Key Concept

Management algorithm for stable Paroxysmal Supraventricular Tachycardia (PSVT)
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Topics

Cardiovascular System

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