Review Article

What Limits Cardiac Performance during Exercise in Normal Subjects and in Healthy Fontan Patients?

Table 1

Comparison of exercise-induced changes in pulmonary versus systemic vascular resistance and pressure. The pulmonary vasculature has very low resistance at rest but relatively limited capacity for further reduction. Therefore, exercise-induced increases in flow result in greater pressures due to the inability to compensate by reducing resistance. As described by the simplified Poiseuille’s law: Pressure = Flow Resistance.

Left VentricleRight Ventricle

Rest

Cardiac Output (L/min)55
Vascular resistance (dyne-sec cm5)110070
Afterload Pressure (mmHg)130/75 (85)25/9 (15)

Exercise

Cardiac Output (L/min)2525
Vascular resistance (dyne-sec cm5)
Afterload Pressure (mmHg)