Chapter 5: The Hemodynamics of Right Ventricular Function

PATIENT CASE

A 52-year-old woman with a history of recurrent pulmonary emboli presents with jugular venous distention, ascites, and lower extremity edema. Laboratory studies reveal a mild transaminitis and an international normalized ratio of 1.3. She is referred for hemodynamic assessment.

BACKGROUND

The right ventricle (RV) has historically been ignored in the generalized assessment of cardiac function, with much of the attention being shifted to the left ventricle (LV) instead. The relative ease of imaging the LV and the known clinical consequences of LV dysfunction are likely reasons for the overshadowing of RV assessments; however, increasing recognition of RV importance in cardiac outcomes has refocused attention toward the “forgotten” ventricle.¹

Embryologically, the RV and LV do not share the same origin. Mammalian studies of cardiac development have shown that the precursor cells of RV development originate in the anterior heart field, which is separate in origin from the LV.² Morphologically, in the developed adult heart, the unique origins of the two ventricles lead to a combination of shared and separated fibers. Surface fibers of the heart are continuous between both ventricles; however, deep fibers appear to be distinct and run in different directions, thus affecting the mechanics of ventricular contraction.³ The LV contracts by the well-described “twisting” motion by shortening along the longitudinal and radial axes, but RV contraction is more complex. The RV free wall shortens along the radial access, and only the septum shortens longitudinally.⁴ Although the geometric motion of the septum can be visualized more as left ventricular, its contribution to RV contraction is significant (estimated between 20% and 80%).^4,5 This intricate interdependence between ventricles contributes to the complexity of assessing RV function.

IMAGING THE RIGHT VENTRICLE

The size and shape of the RV create difficulty in imaging the chamber, both for size estimation as well as functional assessment. Whereas the LV has a regular ellipsoid shape, the RV is semi-lunar and wraps itself around a portion of the RV. Two-dimensional imaging, such as standard echocardiography, is unable to capture the entire chamber in single or orthogonal views.⁶ Newer 3-dimensional echocardiography techniques have an improved ability to see the entire RV, but full resolution and assessment of function continue to be difficult and may be limited by the availability of technology capable of obtaining such images.⁷ Cardiac magnetic resonance imaging offers good resolution in evaluating the irregularly shaped RV⁸ but is often limited by the ability of a patient to undergo such imaging (eg, the presence of pacemakers or defibrillators). Given these challenges, noninvasive imaging is limited in its ability to assess RV function.

HEMODYNAMIC ASSESSMENTS OF THE RIGHT VENTRICLE

As an alternative to noninvasive imaging, hemodynamic assessments of the RV can be performed to better understand the function of the subpulmonic ...