Right Ventricular Involvement in Coronary Artery Disease: Role of Echocardiography for Diagnosis and Prognosis




The right ventricle differs from the left ventricle in many anatomic and physiologic aspects. This disparity renders the right ventricle less vulnerable to ischemia and less susceptible to myocardial injury when right coronary artery occlusion occurs compared with the extent of left ventricular dysfunction during left coronary artery occlusion. Acute right ventricular (RV) myocardial infarction is usually caused by proximal right coronary artery occlusion and therefore is usually associated with inferior myocardial infarction. Conventional echocardiography along with Doppler tissue imaging has played a significant role in early diagnosis of RV myocardial infarction and has a role in prognostic stratification. Stress echocardiography is less validated and more technically demanding in detecting RV reversible dysfunction compared with left ventricular dysfunction. The threshold of RV ischemia during stress echocardiography is higher compared with left ventricular ischemia and usually affects the inferior RV wall. Further studies, particularly with the use of novel echocardiographic techniques such as speckle-tracking and three-dimensional echocardiography, may be required to better elucidate the role of the right ventricle in coronary artery disease


For many years, the right ventricle was overshadowed by the left ventricle, gaining the nickname “the neglected chamber.” Only over the past decades has the impact of right ventricular (RV) performance on clinical status and prognosis been recognized in a variety of pathologic conditions, such as myocardial infarction (MI), heart failure, pulmonary hypertension, and congenital heart diseases. Imaging techniques such as echocardiography and magnetic resonance imaging (MRI) have played a major contribution in the understanding of RV remodeling in those conditions.


Echocardiography, thanks to its noninvasive nature and wide availability, has become the mainstay in the evaluation of the right ventricle in the daily clinical practice. However, the complex RV geometry poses significant difficulties in the evaluation of RV function. Recent advances in echocardiography with Doppler tissue imaging (DTI), speckle-tracking and three-dimensional (3D) echocardiography have provided revived expectations for the better assessment of RV anatomy and function.


RV involvement often occurs in coronary artery disease (CAD), but its detection remains challenging. In this article, we review the role of echocardiography in the detection and evaluation of RV ischemia and ascertain its prognostic impact.


RV Anatomy and the Coronary Circulation


The right ventricle is situated immediately posterior to the sternum and anterior to the left ventricle as it wraps around it. The main anatomic and physiologic features that differentiate the right ventricle from the left ventricle are presented in Table 1 .



Table 1

Main structural and functional characteristics of the right and left ventricle
























































Characteristic Right ventricle Left ventricle
Structure Inflow region, trabeculated myocardium, infundibulum No infundibulum, limited trabeculation
Shape From the side: triangular; cross section: crescentic Elliptic
End-diastolic volume (ml/m 2 ) 75 ± 13 66 ± 12
Ventricular wall thickness (mm) 2–5 7–11
Mass (g/m 2 ) 26 ± 5 87 ± 12
Ejection fraction (%) >45% >55%
Orientation of myofibers Subepicardial: circumferentially; subendocardial: longitudinally Subepicardial: obliquely; subendocardial: longitudinally; middle layers: circumferentially
Systolic pressure/diastolic pressure (mm Hg) 25/4 130/8
Pattern of contraction Mainly longitudinal Twisting and rotational
Stroke work index (g/m 2 /beat) 8 ± 2 50 ± 20
Vascular resistance (dyne · s · cm −5 ) 70 (20–130) 1,100 (700–1,600)
Adaptation to disease states Better adaptation to volume overload states Better adaptation to pressure overload states


When the coronary circulation is right dominant or codominant, as is usually the case, most of the right ventricle is supplied by the right coronary artery (RCA). The definition of dominance is determined by the artery (RCA or left circumflex coronary artery [LCx]) that gives rise to the posterior descending artery (PDA), the posterolateral artery (PLA), and the atrioventricular (AV) nodal artery. The most common pattern (about 85%) is right dominance, whereby the RCA supplies the PDA, the PLA, and the AV nodal artery, followed by the left-dominant system (about 8%), whereby the LCx gives rise to the PDA, the PLA, and the AV nodal artery, and the codominant system (about 7%), with the RCA supplying only the PDA.


The RCA emerges from the anterior sinus of Valsalva and courses through the right AV groove to the inferior part of the septum. During its course, it gives off a variable number of branches: the small conus artery (the first branch of the RCA, present in 50% to 60% of individuals), the right atrial branches, the RV acute marginal branches (among which a large acute marginal runs along the margin of the right ventricle), and in the case of dominance the PDA (which runs along the posterior interventricular sulcus), the PLA, and the AV nodal artery ( Figure 1 ).




Figure 1


Coronary angiogram of the RCA in a normal subject. (A) Right anterior oblique view and (B) anteroposterior view with cranial angulation. AM , Acute marginal.


From the echocardiographer’s perspective, the right ventricle is divided into four segments: the infundibulum (or outflow tract), anterior free wall, lateral wall, and inferior wall ( Figure 2 ). The vulnerability to ischemia of each segment is determined by the extent of blood supply. In particular, (1) the infundibulum receives dual blood supply by the conus artery from the RCA and branches from the left anterior descending coronary artery (LAD); (2) the anterior wall receives dual blood supply by ventricular acute marginal branches from the RCA and branches from the LAD; (3) the inferior wall is supplied by small branches from the large acute marginal and the PDA (in addition, septal branches from the PDA perfuse the inferior part of the interventricular septum); and (4) the lateral wall is supplied by ventricular acute marginal branches from the RCA.




Figure 2


For echocardiographic analysis, the right ventricle (RV) is divided into four segments: the infundibulum, anterior wall, lateral wall, and inferior wall. The most useful projections for assessing RV function during stress echocardiography are presented. Ao , Aorta; LA , left atrium; LV , left ventricle; RA , right atrium.


The dual blood supply (RCA and LAD) of the infundibulum and the anterior wall makes these segments the most resistant to ischemia, while the inferior wall is the most susceptible and the lateral wall has an intermediate level of susceptibility to ischemia.


The right ventricle has also an extensive system of collateral vessels. An important collateral vessel is the moderator band artery, which arises from the first or second septal perforating branch of the LAD and through the moderator band reaches the base of the anterior papillary muscle, where it forms anastomotic connections with branches of the RCA. This collateral route can protect the right ventricle in the event of proximal RCA occlusion. A less important source of collateral blood flow is provided by Kugel’s artery, which bridges the RCA and LCx and is present in only 6% of individuals.




Resistance of the Right Ventricle to Ischemia


In the absence of RV hypertrophy or pulmonary hypertension, the right ventricle is less vulnerable to ischemia than the left ventricle. The more favorable balance between RV oxygen supply and demand can be explained by several factors ( Table 2 ):




  • The lower oxygen demands of the right ventricle: The right ventricle is much thinner (one fourth of left ventricular [LV] mass) and performs only one sixth of the stroke work performed by the left ventricle, because it ejects the same stroke volume against a low-resistance pulmonary vascular circulation.



  • The greater oxygen extraction reserve of the right ventricle: At rest, the right ventricle extracts only 50% of the oxygen delivered by coronary blood flow, whereas the left ventricle extracts about 75%. Therefore, the right ventricle has the ability to raise oxygen extraction in cases of increased oxygen demands during stress or ischemia.



  • In the absence of severe RV hypertrophy or pressure overload, the proximal RCA has a homogeneous pattern of flow during both systole and diastole, which results in better oxygen supply. Conversely, LV perfusion occurs mainly during diastole.



  • The rapid development of collateral circulation through left-to-right (mainly via the moderator band artery) in the case of proximal RCA occlusion, as previously described.



  • When the conus artery has a separate ostium (about 30% of subjects), there is an additional protective mechanism against infundibular ischemia, because its contraction is preserved in proximal RCA occlusion.



Table 2

Pathophysiologic and anatomic characteristics of the right ventricle explaining the lower propensity compared with the left ventricle to ischemia













Lower oxygen consumption because of thinner walls (about one fourth of LV mass) and contraction against a lower pressure system (pulmonary resistance about 1/15th of systemic)
Ability to increase more oxygen extraction during stress or ischemia because the right ventricle extracts at rest about 50%, whereas the left ventricle extracts about 75%
Better oxygen supply because of homogeneous RCA blood flow during both systole and diastole, whereas left coronary artery blood flow occurs predominantly during diastole
Potential for rapid development of collateral circulation in the case of RCA occlusion (mainly provided by the LAD via the moderator band artery)
When the conus artery has a separate ostium (about 30% of subjects), contraction of the infundibulum is preserved in case of proximal RCA occlusion




Resistance of the Right Ventricle to Ischemia


In the absence of RV hypertrophy or pulmonary hypertension, the right ventricle is less vulnerable to ischemia than the left ventricle. The more favorable balance between RV oxygen supply and demand can be explained by several factors ( Table 2 ):




  • The lower oxygen demands of the right ventricle: The right ventricle is much thinner (one fourth of left ventricular [LV] mass) and performs only one sixth of the stroke work performed by the left ventricle, because it ejects the same stroke volume against a low-resistance pulmonary vascular circulation.



  • The greater oxygen extraction reserve of the right ventricle: At rest, the right ventricle extracts only 50% of the oxygen delivered by coronary blood flow, whereas the left ventricle extracts about 75%. Therefore, the right ventricle has the ability to raise oxygen extraction in cases of increased oxygen demands during stress or ischemia.



  • In the absence of severe RV hypertrophy or pressure overload, the proximal RCA has a homogeneous pattern of flow during both systole and diastole, which results in better oxygen supply. Conversely, LV perfusion occurs mainly during diastole.



  • The rapid development of collateral circulation through left-to-right (mainly via the moderator band artery) in the case of proximal RCA occlusion, as previously described.



  • When the conus artery has a separate ostium (about 30% of subjects), there is an additional protective mechanism against infundibular ischemia, because its contraction is preserved in proximal RCA occlusion.



Table 2

Pathophysiologic and anatomic characteristics of the right ventricle explaining the lower propensity compared with the left ventricle to ischemia













Lower oxygen consumption because of thinner walls (about one fourth of LV mass) and contraction against a lower pressure system (pulmonary resistance about 1/15th of systemic)
Ability to increase more oxygen extraction during stress or ischemia because the right ventricle extracts at rest about 50%, whereas the left ventricle extracts about 75%
Better oxygen supply because of homogeneous RCA blood flow during both systole and diastole, whereas left coronary artery blood flow occurs predominantly during diastole
Potential for rapid development of collateral circulation in the case of RCA occlusion (mainly provided by the LAD via the moderator band artery)
When the conus artery has a separate ostium (about 30% of subjects), contraction of the infundibulum is preserved in case of proximal RCA occlusion




Pathophysiology of RV MI


Acute RV MI is usually caused by proximal RCA occlusion and therefore is usually associated with inferior MI. Isolated RV MI occurs in <3% of all acute MIs and is caused by the occlusion of a nondominant RCA or by the isolated occlusion of an RV branch. The prevalence of RV involvement in the setting of inferior MI ranges between 14% and 84% according to the diagnostic criteria. Rarely, occlusion of the LCx in a left-dominant system can lead to RV involvement and may be limited to the inferior RV wall, while occasionally LAD occlusion may affect the anterior part of the RV free wall. Cardiac MRI has shown that early RV ischemic injury (edema with or without late gadolinium enhancement) occurs in one in three anterior MIs, most commonly in the setting of proximal LAD occlusion.


As might be expected, the severity of RV dysfunction depends on the location of RCA occlusion. Severely compromised RV function results from RCA occlusion proximal to the major marginal branches, whereas myocardial injury may be minimal, affecting only the inferior RV wall, when the RCA is occluded distally. Several studies suggest that spontaneous recovery of RV dysfunction after an acute MI is common. Cardiac MRI has shown that although RV late gadolinium enhancement is observed in 54% of patients with acute inferior MIs, 4 months later, late gadolinium enhancement usually disappears, and when it persists, it is located in a very limited area. Therefore, it has been suggested that the term “RV MI” might be a misnomer and that RV MI includes a spectrum of conditions ranging from transient ischemic myocardial dysfunction or stunning, the usual type of ischemic injury, to myocardial necrosis.


Although functional recovery of the right ventricle is common after an ischemic insult, inferior MI complicated by RV MI carries an adverse, particularly short-term prognosis. The mechanism that underlies this excess risk is unclear, but it may be related to the relatively high arrhythmogenic potential of the right ventricle.

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May 31, 2018 | Posted by in CARDIOLOGY | Comments Off on Right Ventricular Involvement in Coronary Artery Disease: Role of Echocardiography for Diagnosis and Prognosis

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