From the Guidelines
The ventricular pressure-volume loop during exercise is characterized by an increase in end-diastolic volume and a decrease in end-systolic volume, resulting in an increased stroke volume 1.
Key Changes in the Ventricular Pressure-Volume Loop
- Increased end-diastolic volume: due to the Frank-Starling mechanism, which allows the heart to pump more blood as the ventricle fills with more blood 1
- Decreased end-systolic volume: due to an increased contractile state of the left ventricle, allowing for more efficient pumping of blood 1
- Increased stroke volume: resulting from the combination of increased end-diastolic volume and decreased end-systolic volume 1
Exercise-Induced Changes in Cardiac Function
- Increased cardiac output: achieved through increases in stroke volume and heart rate, with a greater contribution from heart rate at moderate- to high-intensity exercise 1
- Increased heart rate: due to vagal withdrawal and increases in circulating or neurally produced catecholamines 1
- Increased peripheral arteriovenous oxygen difference: allowing for increased oxygen extraction and delivery to the working muscles 1
From the Research
Ventricular Pressure-Volume Loop During Exercise
The ventricular pressure-volume loop is a graphical representation of the relationship between ventricular pressure and volume throughout the cardiac cycle. During exercise, this loop changes to accommodate increased cardiac output and altered loading conditions.
- The left ventricular pressure-volume loop can be constructed from catheterization data and RN-angiocardiography 2.
- Studies have shown that during exercise, the left ventricular pressure-volume loop shifts downward, with the minimum left ventricular pressure decreasing and the maximum mitral valve pressure gradient increasing 3.
- This shift is thought to be due to sympathetic stimulation and tachycardia, which produce a decrease in the time constant of the fall of isovolumic left ventricular pressure 3.
- The right ventricular pressure-volume loop can also be measured during exercise, and has been shown to be affected by volume calibration methods, such as cardiac MRI or hypertonic saline 4.
- In patients with pulmonary arterial hypertension, poor cardiac output reserve during exercise is associated with right ventricular stiffness and impaired interventricular dependence, as measured by pressure-volume loop analysis 5.
Changes in Ventricular Function During Exercise
During exercise, ventricular function changes to meet increased cardiac output demands.
- Contractility, measured as maximal ventricular elastance, increases in both endurance-trained and sedentary individuals during exercise 6.
- Ventricular efficiency also increases during exercise, suggesting improved external mechanical efficiency 2, 6.
- Arterial elastance decreases during exercise, indicating decreased afterload 6.
- Ventricular-arterial coupling, measured as the ratio of arterial elastance to ventricular elastance, also decreases during exercise, suggesting improved ventricular-arterial interaction 6.
Clinical Implications
The ventricular pressure-volume loop during exercise has important clinical implications, particularly in patients with cardiac disease.
- Pressure-volume loop analysis can be used to evaluate cardiac function and ventricular-arterial interaction during exercise 2, 6.
- Abnormalities in the ventricular pressure-volume loop during exercise may indicate underlying cardiac disease or dysfunction 3, 5.
- Understanding the changes in ventricular function during exercise can inform the development of exercise-based treatments for cardiac disease 6.