TEE is useful in identifying MAs of the sinus of Valsalva and thoracic aorta. Recommendations 1. Either CT scanning or multislice CT angiography with 3D reconstruction is indicated for initial imag- ing (Class I; Level of Evidence B). 2. TEE is useful in identifying MAs of the sinus of Valsalva and thoracic aorta (Class I; Level of Evidence B). Outpatient Therapy Outpatient parenteral antibiotic therapy (OPAT) is efficacious, safe, and cost-effective for a variety of infections,323 325 includ- ing IE that requires prolonged parenteral therapy in hospital- ized patients who otherwise no longer require inpatient care but do require continued parenteral antimicrobial therapy. Antibiotic regimens recommended for IE vary widely and often require 4 weeks of therapy, generally given by the intra- venous route. Absorption of orally administered antimicrobial agents may be unreliable, and such a strategy is generally not recommended as sole therapy for IE. Several other aspects of OPAT such as drug stability at room temperature; frequency of drug dosing; access to ancillary equipment, including ambula- tory pumps; insurance coverage; and whether the patient has a history of IDU can all affect the ultimate use of OPAT. The timing for transition from inpatient antibiotic therapy to OPAT and patient exclusion criteria have been critically evaluated by Andrews and von Reyn.326 These guidelines are based on the local availability of medical care in the outpa- tient setting and risk factors and timing of potential adverse outcomes that would be best managed in the inpatient setting. Before OPAT is considered, most patients with IE should first be evaluated and stabilized in the hospital; only rarely can some patients be treated entirely as outpatients. Patients selected for OPAT should be at low risk for the complications of IE, the most frequent of which are heart failure and systemic emboli. 