From the Guidelines
The Valsalva maneuver decreases cardiac preload by reducing venous return to the heart due to increased intrathoracic pressure. This effect is most pronounced during phase II of the Valsalva maneuver, as described in a study published in the European Journal of Heart Failure 1. When a person performs the Valsalva maneuver, intrathoracic pressure increases significantly, compressing the great veins in the chest and reducing venous return to the heart. With less blood returning to the heart, there is a decrease in ventricular filling, which directly reduces preload.
Physiological Response to Valsalva Maneuver
The normal blood pressure response to the Valsalva maneuver is characterized by four phases:
- Phase 1: Initial increase in blood pressure due to acute increase in intrathoracic pressure
- Phase 2: Sharp decrease in blood pressure due to decreased venous return and compensatory increase in systemic vascular resistance and heart rate
- Phase 3: Short reduction in arterial pressure due to acute reduction in intrathoracic pressure
- Phase 4: Overshoot in arterial pressure due to increased venous return with a decrease in systemic vascular resistance and heart rate
Clinical Implications
The Valsalva maneuver can be used as a non-invasive bedside tool to evaluate volume status, as demonstrated by a study published in the European Journal of Heart Failure 1. Bedside sphygmomanometry can provide a qualitative assessment of volume status, and commercially available arterial waveform devices can provide a rapid and reliable beat-to-beat measurement of cardiovascular dynamics. The mechanism behind the abnormal response to the Valsalva maneuver in patients with heart failure is the maintenance of LV filling from increased central blood volume that maintains stroke volume, despite changes in intrathoracic pressures.
From the Research
Effect of Valsalva on Preload
- The Valsalva maneuver decreases venous return to the heart, which in turn decreases preload 2.
- During the strain phase of the Valsalva maneuver, peripheral venous pressures become increased, while systolic and pulse pressures begin to fall 2.
- The decrease in preload is due to the increase in intrathoracic pressure, which reduces the pressure gradient for venous return to the heart 2.
- In normal subjects, left ventricular end-diastolic volume decreases during the Valsalva maneuver, indicating a decrease in preload 3.
- However, in patients with cardiomyopathy, left ventricular end-diastolic volume may not decrease significantly during the Valsalva maneuver, suggesting a different response to the maneuver in these patients 3.
- The Valsalva maneuver can be used as a bedside test to estimate filling pressures in patients with heart failure, with an abnormal response to the maneuver indicating increased filling pressures 4, 5.