You are working with your patient and all of a sudden, she loses consciousness.

You conduct a pulse check, but it is hard to tell if you can feel anything.

After calling a code blue and starting chest compressions, you and the staff notice the patient is in ventricular fibrillation.

What is your next intervention in this situation?

Choice A rationale

An oxygen saturation (SpO_2) of 94% is mild hypoxemia (normal range is 95-100%), which is concerning but not the most critical finding compared to electrical changes indicating acute muscle injury. It could be due to pain, hypoventilation, or pre-existing lung disease, and is treatable with supplemental oxygen.

Choice B rationale

A heart rate of 110 beats per minute is sinus tachycardia (normal range is 60-100 bpm), which may be a compensatory response to pain, anxiety, or low cardiac output in ACS. While it increases myocardial oxygen demand, it is a secondary sign and less immediately critical than direct EKG evidence of transmural ischemia.

Choice C rationale

A blood pressure of 140/90 mmHg is Stage 2 hypertension (normal for adults is <120/<80 mmHg), which increases cardiac workload and is detrimental to an ischemic heart. However, it is a hemodynamic variable and not the most direct or specific evidence of active, transmural myocardial injury that requires immediate reperfusion.

Choice D rationale

ST-segment elevation in contiguous leads (V1-V4 are anterior leads) is the hallmark EKG finding for an ST-elevation myocardial infarction (STEMI), indicating an acute, complete coronary artery occlusion and transmural myocardial ischemia/injury. This is the most critical and life-threatening finding that mandates immediate reperfusion therapy. —.

Choice A rationale

Atrial depolarization, the electrical event initiating the P wave on the EKG, begins as the electrical impulse leaves the Sinoatrial (SA) node and spreads through the atria. The P wave represents the beginning and completion of this atrial depolarization, not the ST segment, which occurs much later in the cardiac cycle after ventricular contraction.

Choice B rationale

Ventricular depolarization, the rapid electrical spread that causes ventricular contraction, is represented by the QRS complex on the EKG. This complex follows the P wave and precedes the ST segment, making this choice an incorrect representation for the ST segment.

Choice C rationale

The time required for the electrical signal to travel from the atria through the AV node and bundle of His to the ventricles is measured by the PR interval on the EKG. This interval begins at the start of the P wave and ends at the start of the QRS complex, preceding the ST segment.

Choice D rationale

The ST segment begins at the J point (end of the S wave) and ends at the beginning of the T wave. This electrically neutral period reflects the time when the ventricles are fully depolarized (contracted) and isovolumetrically contracting, marking the completion of ventricular depolarization and the initiation of ventricular repolarization. —.