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, with dynamic exercise primarily causing a volume load on the left ventricle (LV) and static exercise causing a pressure load 1.
Key Changes in the Ventricular Pressure-Volume Loop
- Increased end-diastolic volume: due to the Frank-Starling mechanism, which is the most important factor for athletes 1
- Decreased end-systolic volume: due to an increased contractile state of the LV 1
- Increased stroke volume: achieved by both an increase in end-diastolic volume and a decrease in end-systolic volume 1
- Volume load vs pressure load: dynamic exercise primarily causes a volume load on the LV, whereas static exercise causes a pressure load 1 ### Physiological Responses to Exercise As exercise intensity increases, cardiac output is increased by an augmentation in stroke volume and heart rate, as well as an increasing peripheral arteriovenous oxygen difference 2. At moderate- to high-intensity exercise, the continued rise in cardiac output is primarily attributable to an increase in heart rate, as stroke volume typically reaches a plateau at 50% to 60% of maximal oxygen uptake 2.
Clinical Implications
Understanding the changes in the ventricular pressure-volume loop during exercise is essential for assessing cardiac function and adapting exercise programs for individuals with cardiovascular abnormalities [(1, 2)].
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 3.
- 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 4.
- 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 4.
- 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 5.
- 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 6.
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 7.
- Ventricular efficiency also increases during exercise, suggesting improved external mechanical efficiency 3, 7.
- Arterial elastance decreases during exercise, indicating decreased afterload 7.
- Ventricular-arterial coupling, measured as the ratio of arterial elastance to ventricular elastance, also decreases during exercise, suggesting improved ventricular function 7.
Clinical Applications
The measurement of ventricular pressure-volume loops during exercise has clinical applications in the assessment of cardiac function and the diagnosis of cardiac disease.
- Pressure-volume loop analysis can be used to evaluate cardiac function in patients with cardiac disease, such as pulmonary arterial hypertension 6.
- The use of non-invasive methods, such as cardiac MRI, to measure ventricular pressure-volume loops during exercise may provide a useful tool for the assessment of cardiac function in clinical practice 7, 5.