Assignment task: The nurse provides care for a client with a history of mitral valve stenosis on a telemetry unit. The nurse notes new onset of atrial fibrillation on the monitor. Assessment of the client reveals a heart rate of 180 beats per minute and blood pressure 59/30 mm Hg, and the client is not arousable to verbal stimuli. Which action will the nurse take first?
1. Administer an IV bolus of 70 units/kg heparin.
2. Assess the client's lung sounds.
3. Prepare for immediate synchronized cardioversion.
4. Request a transesophageal echocardiogram.