an elongate outer tube of biocompatible material comprising a proximal end and a distal end and a central portion therebetween, wherein the elongate outer tube is capable of being flexed if a threshold amount of force is applied, the elongate outer tube comprising a curved deflection between the distal end and the central portion; the curved deflection comprising a stiffness sufficient to cause the esophagus to conform to the shape of the curved deflection when the elongate outer tube is inserted into the esophagus;

an elongate insertion tube or rod comprising a distal end and a proximal end, the elongate insertion tube being smaller in diameter than the elongate outer tube, the elongate insertion tube being formed of material comprising a stiffness sufficient to create the threshold amount of force applied from within the elongate outer tube to at least partially straighten the curved deflection when the elongate insertion tube or rod is inserted in the deflection, wherein a length of the elongate outer tube from a central portion to the distal end is predetermined to place the curved deflection at a targeted esophagus location near the left atrium of the heart and the curved deflection is U-shaped or is compound curve shaped; and

a handle at the proximal end of the elongated outer tube, the handle comprising view holes to view markings on the elongate insertion tube or rod, the markings and view holes combining to provide a depth insertion indicator, which indicates the relative position of the elongate insertion tube or rod in the elongate outer tube, wherein the elongate outer tube comprises bellows and the curved deflection includes bellows comprising different stiffnesses, wherein the bellows comprising different stiffnesses in the curved deflection comprise a section of one or more bellows of lesser stiffness between two sections of one or more bellows of a greater stiffness.