A 51-year-old woman comes to the physician for a 3-month-history of worsening shortness of breath on exertion. Physical examination shows bibasilar crackles and mild pedal edema. Jugular venous pulsations are 5 centimeters above the sternal angle. Echocardiography shows an ejection fraction of 35%. Which of the following is the most appropriate next step in pharmacologic therapy?
Antagonism of β receptors
Antagonism of enzyme cleavage
Enhancement of cGMP production
Inhibition of calcium channels
Inhibition of phosphodiesterase
