[Intraoperative transesophageal echocardiography: guidelines for anesthesiologist training. Joint Task Force of the Echocardiography Section and other Imaning Techniques of the Spanish Society of Cardiology and of the Cardiothoracic Surgery Section of the Spanish Society of Anesthesiology, Recovery, and Pain Therapy] Revista española de cardiología. [Rev Esp Cardiol] Journal article