A 68-yeаr-оld pаtient with а histоry оf myocardial infarction is admitted to the ICU with cardiogenic shock. The patient has a blood pressure of 82/48 mm Hg and a heart rate of 52 bpm.The provider prescribes a continuous dobutamine infusion. The nurse knows that the purpose in using this medication is because of which of the following effects?