A 50-year-old breast cancer patient admitted to the ED with shortness of breath and suffers a sudden cardiac arrest. After an initial cycle of CPR, a sinus tachycardia rhythm is visible on the monitor, but a manual pulse is not detected. POCUS reveals a visible pulse in the carotid and a persistent pulse oximetry waveform is present. Chest compressions are stopped, and cardiac POCUS is undertaken. Vigorous LV contractions are detected without evidence of tamponade. The RV is distended, and the septum is deviated toward the left heart. What is the most likely cause of this PEA arrest?