A patient presents with worsening shortness of breath and atrial fibrillation with rapid ventricular response. What is the recommended therapy in this hemodynamic unstable situation?

In the scenario of a patient presenting with worsening shortness of breath and atrial fibrillation accompanied by a rapid ventricular response, synchronized electrical cardioversion is the most appropriate therapy for a hemodynamically unstable patient.

Synchronized electrical cardioversion is indicated in cases of arrhythmias that result in significant symptoms or unstable hemodynamics, as it effectively restores a normal rhythm. It involves delivering a shock that is synchronized with the R wave of the ECG, thereby minimizing the risk of inducing ventricular fibrillation. In the context of atrial fibrillation with rapid ventricular response that leads to deterioration in the patient's hemodynamic status, immediate intervention is crucial. This method allows for a swift return to normal sinus rhythm, which can alleviate the patient's symptoms and improve cardiac output.

The other options, while useful in different contexts, do not provide the immediate effect required in this unstable situation. Transcutaneous pacing is generally used for bradycardia or when pacing is necessary due to heart block, not for atrial fibrillation. Intravenous beta-blockers like metoprolol and calcium channel blockers like diltiazem can be used for rate control in stable patients but are not suitable for acute management in a hemodynamically unstable setting