Right & Left Heart Differences
As Critical Care Nurses, we must understand those differences to see the big picture of what is happening with our patients and certain pathophysiology.
The heart is a single organ with two sides separated down the middle by the intraventricular septum. Even though it is one organ, the two sides vastly differ in structure and function.
Right Side of the Heart:
Structure:
Structurally, the right ventricle is positioned more anteriorly within the chest wall than the left ventricle, which makes it more susceptible to injury related to blunt chest trauma.
The right ventricle has a crescent shape and a thinner myocardial wall (about ⅙ the muscle mass of the LV) because it pumps blood a short distance to the lungs. Two valves, the tricuspid and pulmonic valves, exist within the right side of the heart.
Function:
Although the left side of the heart seems to get all the attention, the right side plays a vital role in the overall cardiovascular system, mostly due to its relation to pulmonary circulation.
The primary role of the right side of the heart is to receive deoxygenated blood and mobilize it into the lungs to participate in gas exchange. Right-sided oxygen saturation can be measured by obtaining a SvO₂ or ScvO₂, providing valuable information on cellular O₂ consumption and demand.
The right side is a low-pressure and low-resistance system due to the thin and compliant pulmonary arteries within the pulmonary circulatory system. This is also why, structurally, it has a thinner myocardial wall. It simply doesn’t have to work as hard (read: lazy).
The RV is very sensitive to acute changes in afterload. Even small changes in PVR will significantly overload the right heart, contributing to hemodynamic instability and RV failure.
Various disease processes (i.e., idiopathic pulmonary arterial hypertension, ARDS, pulmonary emboli, COPD) can contribute to increases in pulmonary vascular resistance (PVR), as can treatments such as the delivery of high levels of PEEP.
An increase in afterload will directly influence the right ventricle’s ability to mobilize blood into the pulmonary circulation and over to the left side of the heart, decreasing LV preload. As we know, preload is a determinate of cardiac output!
The right side of the heart is considered a volume pump. It matches the stroke volume of the LV despite having a lower ejection fraction. The end-diastolic volume is greater than that of the LV, and it is more tolerant to acute changes in preload. The right ventricle’s increased compliance contributes to its ability to manage increases in volume without resulting in a decrease in stroke volume, assuming it is working optimally.
Although the right and left sides of the heart are unique in structure and function, they still depend on each other for optimal cardiovascular function and hemodynamic stability.
The right side of the heart might be lazy and sensitive, but it packs a big punch. As ICU nurses we must remember it when looking at the big picture of our critically ill patients.
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