A 44-year-old man with no significant past medical history presents to the hospital with several weeks of progressive dyspnea on exertion and palpitations. 12-lead ECG is performed and reveals atrial flutter with a ventricular rate of 145 beats per minute. Transthoracic echocardiogram is performed and demonstrates a reduced left ventricular ejection fraction of 35% with normal right ventricular function and no other significant abnormalities. Transesophageal echocardiogram is also performed which does not show any evidence of left atrial appendage thrombus. He is started on apixaban. Which of the following is the next best step for management of this patient’s condition?

A 65-year-old woman with a history of diabetes presents to the emergency department after an episode of syncope while driving. 12-lead ECG is obtained and demonstrates atrial fibrillation with a ventricular rate of 62 beats per minute and occasional monomorphic PVCs with a nonspecific intraventricular conduction delay and a QTc of 490 ms. Transthoracic echocardiogram demonstrates a left ventricular ejection fraction of 62%. Cardiac MRI is performed which shows a thickened interventricular septum with a maximum of 32 mm along with 20% late gadolinium enhancement. Holter monitoring is performed which demonstrates frequent episodes of nonsustained ventricular tachycardia. There is no evidence of obstructive physiology on echo or MRI. Which of the following is the next best step in management?

A 35-year-old woman with a history of a surgically corrected atrial septal defect in infancy presents to the hospital with weight gain, fatigue, and shortness of breath. Her left ventricular ejection fraction is severely depressed at 20%. 12-lead ECG demonstrates atrial flutter with a rate of 160 bpm. In the emergency department, she becomes acutely hypotensive and undergoes emergent cardioversion. Repeat ECG demonstrates sinus rhythm with a normal QRS and normal QT interval. She is started on anticoagulation and admitted to the hospital. Which of the following is a reasonable next step?