If the pre-arrest ECG shows an anterior wall myocardial infarction, the cardiac arrest is most likely due to which issue?

• A. Impaired electrical conduction due to hyperkalemia
• B. Impaired contractility leading to reduced cardiac output
• C. Pericardial tamponade
• D. Tension pneumothorax

Answer: (B)

An anterior wall MI injures a large portion of the left ventricle, so the heart’s pumping ability is impaired. When contractility falls acutely, stroke volume and cardiac output drop dramatically, making it hard to sustain circulation and often leading to cardiac arrest from pump failure. This is the direct consequence of the infarcted myocardium: the heart can’t push blood effectively.

Hyperkalemia causes electrical disturbances unrelated to the infarct itself, and issues like tamponade or tension pneumothorax are obstructive problems that aren’t the immediate result of an anterior MI. Hence the most likely mechanism is impaired contractility leading to reduced cardiac output.