A patient presents to the Emergency Department (ED) with chest pain.

An EKG is done and the patient is found to have an ST elevation myocardial infarction (STEMI). Your hospital has a catheterization lab and is capable of doing percutaneous coronary intervention on site.

This patient should have a percutaneous coronary intervention (PCI) to open the blocked artery within

Choice A rationale

Forceful coughing increases intrathoracic pressure and vagal stimulation, activating the parasympathetic system to slow AV nodal conduction. This vagal maneuver transiently interrupts reentrant circuits responsible for paroxysmal supraventricular tachycardia (PSVT), restoring normal sinus rhythm. The maneuver is noninvasive, first-line, and physiologically effective for terminating AV nodal reentry tachycardia by enhancing acetylcholine-mediated suppression of nodal conduction velocity and refractory period shortening.

Choice B rationale

Bearing down as during a bowel movement, known as the Valsalva maneuver, similarly increases vagal tone. The increased intrathoracic pressure transiently reduces venous return, stimulating baroreceptors and causing reflex bradycardia. This vagal reflex inhibits reentrant impulses through the AV node, terminating PSVT episodes. The Valsalva maneuver is evidence-based, safe, and recommended as the initial nonpharmacologic intervention before pharmacologic or electrical therapy.

Choice C rationale

Jumping up and down once has no physiologic effect on vagal tone or AV nodal conduction. PSVT involves a reentrant circuit within or near the AV node, requiring vagal or pharmacologic interruption. Physical exertion like jumping may transiently increase sympathetic output, worsening tachycardia rather than terminating it. Therefore, this action provides no therapeutic value and is not recommended for PSVT management.

Choice D rationale

Adenosine rapidly blocks AV nodal conduction by hyperpolarizing nodal tissue through A1 receptor activation, effectively terminating AV nodal reentrant tachycardia. It is administered as a rapid intravenous bolus due to its 10-second plasma half-life. Adenosine temporarily induces asystole before sinus rhythm resumes. It is a first-line pharmacologic intervention when vagal maneuvers fail, demonstrating high efficacy in converting PSVT to normal sinus rhythm.

Choice A rationale

Synchronized cardioversion delivers a low-energy electrical shock timed to the QRS complex to interrupt a rapid, organized rhythm like atrial fibrillation or ventricular tachycardia with a pulse. It is contraindicated in ventricular fibrillation (VF) because VF is a chaotic, unsynchronized rhythm, and mistimed delivery can worsen the rhythm.

Choice B rationale

Ventricular fibrillation (VF) is a lethal cardiac rhythm characterized by chaotic, uncoordinated electrical activity, resulting in no mechanical pump function and immediate cardiac arrest. The definitive and most critical intervention to terminate VF and restore a perfusing rhythm is immediate, high-energy, unsynchronized electrical shock, known as rapid defibrillation.

Choice C rationale

While placing the patient on oxygen (normal range 95-100% saturation) is a general supportive measure in cardiac arrest, it is not the primary intervention for a patient in ventricular fibrillation (VF). The immediate priority is defibrillation to restart the heart, as oxygenation without circulation is ineffective.

Choice D rationale

The Advanced Cardiac Life Support (ACLS) protocol for pulseless cardiac arrest prioritizes high-quality chest compressions and early defibrillation for shockable rhythms like ventricular fibrillation (VF). Rescue breaths are part of the C-A-B sequence (Circulations, Airway, Breathing) but are secondary to defibrillation in VF and should not delay the shock.