Background
Right ventricular infarction was first recognized in a subgroup of patients with inferior wall myocardial infarctions who demonstrated right ventricular failure and elevated right ventricular filling pressures despite relatively normal left ventricular filling pressures. Increasing recognition of right ventricular infarction, either in association with left ventricular infarction or as an isolated event, emphasizes the clinical significance of the right ventricle to total cardiac function.
Interest in recognizing right ventricular infarction noninvasively has grown because of the therapeutic implications of distinguishing patients with right ventricular dysfunction from those with the more usual clinical presentation of left ventricular dysfunction. Patients with right ventricular infarctions associated with inferior infarctions have much higher rates of significant hypotension, bradycardia requiring pacing support, and in-hospital mortality than isolated inferior infarctions. [1]
See Are You Missing Subtle MI Clues on ECGs? Test Your Skills, a Critical Images slideshow, to help identify a variety of electrocardiographic abnormalities.
For more information, see Myocardial Infarction.
Pathophysiology
The right ventricle is a thin-walled chamber that functions at low oxygen demands and pressure. It is perfused throughout the cardiac cycle in both systole and diastole, and its ability to extract oxygen is increased during hemodynamic stress. All of these factors make the right ventricle less susceptible to infarction than the left ventricle.
The posterior descending branch of the right coronary artery usually supplies the inferior wall of the right ventricle. The acute marginal branches of the right coronary artery supply the anterior wall of the right ventricle, and the conus branch supplies the infundibulum of the right ventricle. [2]
A direct correlation exists between the anatomic site of right coronary artery occlusion and the extent of right ventricular infarction. Studies have demonstrated that more proximal right coronary artery occlusions result in larger right ventricular infarctions. [3] On occasion, the right ventricle can be subjected to infarction from occlusion of the left circumflex coronary artery. [4]
When contractility and associated diastolic dysfunction are impaired attendant to right ventricular infarction, the right ventricular diastolic pressure increases substantially and systolic pressure decreases. In such a scenario, concomitant left ventricular dysfunction, with an increase in right ventricular afterload, is possible. In such a setting, right ventricular output can decrease dramatically, and right atrial pressure increases. In this circumstance, the right ventricle serves as a poorly functioning conduit between the right atrium and the pulmonary artery.
Elevation of right atrial pressure secondary to right ventricular infarction serves as a stimulus for secretion of atrial natriuretic factor. Increased levels of this polypeptide can be detrimental by virtue of the potent vasodilating, natriuretic, diuretic, and aldosterone-inhibiting properties of atrial natriuretic factor, thereby worsening the clinical syndrome of right ventricular infarction. [5] The potential hemodynamic derangements associated with right ventricular infarction render the afflicted patient unusually sensitive to diminished preload (ie, volume) and loss of atrioventricular synchrony. These 2 circumstances can result in a severe decrease in right and, secondarily, left, ventricular output. [6, 7, 8]
Early reperfusion of the occluded coronary artery resulting in right ventricular infarction is associated with prompt reduction in right atrial pressure. The extent of right ventricular infarction varies greatly and is dependent on the site of occlusion of the right ventricular arterial supply. If the occlusion occurs before the right ventricular marginal branches and if collateral blood flow from the left anterior descending coronary artery is absent, then the size of infarction is generally greater. [9, 10]
Epidemiology
Isolated infarction of the right ventricle is rare; right ventricular infarction is usually noted in association with inferior wall myocardial infarction. The incidence of right ventricular infarction in such cases ranges from 10% to 50%, depending on the series. [11]
The incidence of clinically evident right ventricular infarction is considerably less than that found at autopsy. [10, 12, 13, 14] One reason for the discrepancy is the difficulty in establishing the presence of right ventricular infarction in living subjects. Additionally, right ventricular dysfunction and stunning are frequently transient, such that estimation of the true incidence of right venticular infarction is difficult. Criteria have been set forth to diagnose right ventricular infarction; even when strictly employed, however, the criteria lead to underestimation of the true incidence of right ventricular infarction. [15, 16, 17]
Tables
Leads |
Sensitivity (%) |
Specificity (%) |
V1 |
28 |
92 |
V3 R |
69 |
97 |
V4 R |
93 |
95 |
