The crocodilian heart and central hemodynamics

Area of Science:

• Comparative anatomy
• Cardiovascular physiology
• Herpetology

Background:

• Crocodilian hearts possess two atria and two ventricles, similar to birds and mammals.
• Unique cardiovascular anatomy includes a right aorta (RAo) from the left ventricle and a left aorta (LAo) from the right ventricle.
• The foramen of Panizza connects the RAo and LAo outside the valves.

Purpose of the Study:

• To elucidate the functional significance of the foramen of Panizza in crocodilian cardiovascular physiology.
• To describe the dynamics of blood flow within the left aorta (LAo) and its regulation.
• To investigate the conditions under which a pulmonary bypass (right-to-left shunt) occurs.

Main Methods:

• Analysis of crocodilian cardiac anatomy and vascular connections.
• Hemodynamic principles applied to understand blood flow dynamics.
• Physiological conditions influencing pressure gradients and valve function were considered.

Main Results:

• During diastole, the foramen of Panizza equalizes pressure between the RAo and LAo, typically keeping the LAo pressure higher than right ventricular pressure.
• LAo blood flow is biphasic with systolic reversal due to foramen closure by the RAo valve, resulting in low net flow.
• A right-to-left shunt (pulmonary bypass) occurs when right ventricular systolic pressure exceeds LAo pressure, facilitated by pulmonary vasoconstriction or decreased systemic blood pressure.

Conclusions:

• The foramen of Panizza plays a crucial role in regulating LAo pressure and flow dynamics.
• The crocodilian cardiovascular system exhibits a sophisticated mechanism for shunting blood, allowing adaptation to varying physiological demands.
• This unique anatomy facilitates a functional pulmonary bypass, contributing to the survival and adaptability of crocodilians.