One-third of patients with inferior wall myocardial infarction have right ventricular involvement. The most serious complication of right ventricular infarction is shock. Right ventricular infarction results in a reduction in right ventricular end-systolic pressure, left ventricular end-diastolic size, cardiac output, and aortic pressure as the right ventricle becomes more of a passive conduit to blood flow. Left ventricular contraction causes bulging of the interventricular septum into the right ventricle, with resultant ejection of blood into the pulmonary circulation. As a result, right ventricular infarction in the setting of a large left ventricular infarction has a particularly devastating effect on hemodynamic function. Factors that reduce preload (volume depletion, diuretics, and nitrates) or decrease right atrial contraction (atrial infarction and loss of atrioventricular synchrony) and factors that increase right ventricular afterload (left ventricular failure) can lead to significant hemodynamic derangements.
Treatment of right ventricular infarction includes maintenance of preload, reduction of right ventricular afterload, and inotropic support of an ischemic right ventricle, in addition to early reperfusion.45 Patients with right ventricular infarction should not be treated with drugs, such as nitrates, that reduce preload. In the setting of right ventricular infarction, nitrates will often reduce cardiac output and produce hypotension. Instead, patients with marginal preload or hypotension should be treated with volume loading (normal saline). The increased preload will improve right ventricular cardiac output. If cardiac output is not improved after 1 to 2 L of normal saline, inotropic support with dobutamine should be initiated.
High-degree heart block is very common in patients with right ventricular infarction. The loss of right atrial kick can greatly compromise right ventricular cardiac output. Restitution of atrioventricular synchrony is important. For patients who require pacing in the setting of right ventricular infarction, it may be necessary to establish atrioventricular sequential pacing leads. Patients who do not attain hemodynamic improvement after placement of a ventricular pacer may still improve with atrioventricular sequential pacing reestablishing a right atrial kick.
When right ventricular infarction is accompanied by left ventricular dysfunction, the use of nitroprusside to reduce afterload, or intra-aortic balloon counterpulsation, may be of benefit. Reduction in left ventricular afterload may help passive movement of blood through the right ventricle.
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