'Four chamber working mode perfusion' differs from the Langendorff mode in a number
of aspects. First, there is two-way flow through the aorta whereas only retrograde flow existed
during Langendorff mode. Second, all 4 chambers of the heart are filled with changing volumes and
the natural flow through the heart is preserved; the atrial flow empties into the ventricle during
diastole where it is then ejected from the ventricle during systole. Third, the aortic valve opens
and closes as the heart contracts. Finally, the flow into the coronaries is determined by the
contraction/performance of the heart itself and not by an external pump, as in the Langendorff
Working mode has also been called physiological perfusion because it objective is to best simulate
or recreate the in vivo perfusion and flows through heart. The preload and afterload
provided by the isolated heart apparatus are the primary determinants of flow through the 4 heart
chambers and the coronary system. For example, a rise in the preload will increase atrial and
ventricular filling and which translates into greater contractility (Frank-Starling principle).
However, overdistension of the ventricle will increase the oxygen demand and have a negative effect
on contractility. Afterload is characteristic of the pressure work the ventricle must do to overcome
the impedance to ejection created by the diastolic pressure in the aorta. A reduction of afterload
will increase cardiac output but extreme hypotension will decrease coronary flow and impair
contractility. If afterload is increased, the stroke volume and ejection fraction will decline.
Therefore, by adjusting the preloads and afterloads various cardiac states can be simulated in the
Visible Heart® apparatus of both the normal or impaired (diseased) heart.