Fig. 1.

Experimental setup. (A) The heart imaging system consists of a custom-made vacuum-based heart stabilizer (for allocating different water immersion stick-type objective lenses), an electrocardiogram (ECG) recorder and amplifier, a small animal ventilator, a laser scanning microscope (LSM), acquisition signal electronics and an elaborating unit. The murine heart is held in contact with the stick objective via a gentle negative pressure. During imaging, ECG signals, lung airway pressure signals and the microscope scan timing signals are recorded for image reconstruction via retrospective gating. (B) A three-dimensional schematic model of the custom-made heart stabilizer. The stabilizer is connected to a vacuum regulator through a 1mm-diameter metal conduit (gray). Scale bar 5 mm. (C) Side section view of (B) with a stick-type objective lens. Arrows indicate the direction of the suction flow. The outer chamber of the stabilizer is under negative pressure and provides the vacuum, which gently holds the heart tissue in place,. The internal chamber is maintained at standard pressure and is filled with water for index matching of the objective lens. A cover slip glued at the end of the second chamber prevents water from leaking out. The myocardium is in direct contact with the cover slip.