What is the effect of the Valsalva maneuver on the afterload of the right ventricle (RV)?

From the Guidelines

The Valsalva maneuver increases the afterload of the right ventricle by compressing the pulmonary vasculature and increasing pulmonary vascular resistance, thereby elevating the pressure against which the right ventricle must pump. This effect is a result of the increased intrathoracic pressure created by forceful exhalation against a closed glottis during the Valsalva maneuver, as described in the context of right-sided heart failure management 1. The right ventricle (RV) is particularly sensitive to changes in afterload due to its unique geometry and function, with peak RV pressure occurring before the end of systolic ejection, leading to a more trapezoid-appearing RV PV loop 1.

Key Points About RV Afterload

• RV afterload is most appropriately defined as the RV wall stress during systolic ejection, estimated by the summation of the resistive and pulsatile components of blood flow 1.
• Commonly used measures of RV afterload, including PA systolic pressure (PASP) and pulmonary vascular resistance (PVR), provide an inadequate description of RV afterload because they do not account for contributions of pulsatile loading 1.
• The RV has a shallower end-systolic PV slope than the LV, which results in lesser change in end-systolic pressure, generating greater change in end-systolic volume, making RV systolic function highly sensitive to changes in afterload 1.

Clinical Implications

The increase in RV afterload during the Valsalva maneuver can have significant clinical implications, particularly for patients with pre-existing right heart failure. As noted in the management of right-sided heart failure, acute increases in RV afterload, such as those caused by a large pulmonary embolism, can abruptly decrease RV stroke volume with minimal increase in RV systolic pressure 1. This mechanism explains why patients with right heart failure often struggle with activities involving Valsalva-like maneuvers, as these can worsen right ventricular workload and potentially exacerbate heart failure symptoms.

Mechanism of Action

The effect of the Valsalva maneuver on RV afterload occurs in phases, initially causing decreased venous return and increased systemic blood pressure, followed by decreased venous return leading to decreased cardiac output and blood pressure, an initial further drop in blood pressure due to pulmonary vessel expansion when the maneuver stops, and finally, a blood pressure overshoot as cardiac output normalizes while peripheral vasoconstriction persists. Understanding this mechanism is crucial for managing patients with right heart failure and advising them on activities that may exacerbate their condition.

From the Research

Effect of the Valsalva Maneuver on Right Ventricular Afterload

• The Valsalva maneuver increases intrathoracic pressure, which incites a sequence of rapid changes in preload and afterload stress 2.
• During the strain, venous return to the heart is decreased and peripheral venous pressures become increased, leading to an increase in total peripheral resistance and afterload 2.
• The increase in afterload is counterbalanced by a decrease in systolic and pulse pressure, but an increase in mean arterial pressure 2.
• The Valsalva maneuver also affects right ventricular function, with studies showing that it can increase the right ventricular ejection fraction and prolong bolus duration and right ventricular transit time 3.

Mechanisms of Right Ventricular Afterload

• Right ventricular afterload is determined by the dynamic interaction between pulmonary vascular resistance, characteristic impedance, and wave reflection 4.
• Pulmonary vascular impedance represents the most comprehensive measure of right ventricular afterload, but its measurement is complex 4.
• Characteristic impedance and wave reflection coefficient can be derived from right ventricular pressure waveform analysis and can be used to improve estimation of right ventricular afterload 4.

Clinical Implications

• The Valsalva maneuver can be used to assess right ventricular function and afterload, with changes in right ventricular ejection fraction and afterload parameters providing insight into right ventricular-vascular coupling 3, 4.
• Understanding the mechanisms of right ventricular afterload is important for the management of pulmonary hypertension and other cardiovascular diseases 5, 6, 4.
• Right ventricular afterload increases with increasing tidal volume during mechanical ventilation, highlighting the importance of cardioprotective ventilation strategies 6.