Setup of an ex vivo system for an isolated zebrafish heart. (A) Equipment needed, including a dissecting microscope (1), with a camera (2), pump (3) and stimulator (4). (B) Two-line 34G catheters (5) are placed on a Sylgard-coated Petri dish with the use of insect pins; 2 hearts are tied on the ends of the catheters (inset depicts the position of a cannula in the heart; arrowhead points to the place of the tie by the atrioventricular junction), which are put in front of a mirror (6); platinum electrodes (7) are used for electrical field stimulation. A pool (8) was made to control the solution level. (C) Diagram of the perfusion system.

Comparison of cardiac function measurements obtained from the ex vivo method and from in vivo HFE. (A) Representative images of adult hearts at end-diastolic and end-systolic phases of cardiac cycle ex vivo. Scale bar: 1 mm. (B) Representative echocardiographic images of adult fish hearts at end-diastolic and end-systolic phases in vivo. (C) Parameters of the same group of 20 fish obtained from either HFE or ex vivo assay at low and high load. HR, heart rate; bpm, beats per minute.