Diagnosis
Right ventricular infarction should be suspected in all cases of inferior infarction and identified because its treatment is substantially different. The triad of hypotension, clear lungs, and jugular engorgement is highly specific but only 25% sensitive. Jugular engorgement alone has a sensitivity of 88% with specificity of 69%. Kussmaul’s sign is highly sensitive and specific. Other clinical signs may include right ventricular gallop and tricuspid regurgitation.
Hemodynamic measurements usually show right atrial pressures greater than 10 mmHg and above 80% of pulmonary capillary pressure. The right ventricular pressure curve frequently shows the square root sign.
The electrocardiogram is useful to demonstrate ST segment elevation greater than 1mm in lead V4r, which occurs only 10 hours after the onset of symptoms. This shunt should be taken routinely in all inferior infarcts or in other right bundle branch findings or complete AV blocks.
The echocardiogram frequently confirms the suspected diagnosis by showing a dilated right ventricle with areas of akinesia and alterations in septal mobility. Other findings may be bulging of the interatrial septum to the left, tricuspid insufficiency, ventricular septal defects or, in rare cases, the opening of a forced foramen ovale.
The isotopic ventriculogram of the right ventricle may also be useful to detect abnormalities with risk of mortality.
Specific treatment in right ventricular infarction
Treatment of ventricular infarction includes ensuring adequate preload to the ventricle, reducing afterload, inotropic support, and early reperfusion.
Preload maintenance includes:
volume loads with saline solution which can resolve hypotension and improve cardiac output, but if exceeded it has the counterproductive effect of deviating the septum to the left, making this ventricle restrictive and further worsening cardiac output. It has been proven that maintaining central venous pressures between 15 and 20 mmHg are sufficient and higher values do not have any additional beneficial effect. If after replacing the first 1 to 2 L of volume the patient does not regain hemodynamic stability, subsequent management should be guided by the data provided by a flotation catheter in the pulmonary artery.
Avoid concomitant use of nitrates, diuretics or morphine. Maintenance of atrio-ventricular synchrony, using temporary DDD pacemakers if appropriate in case of atrio-ventricular dissociation. Prompt electrical or pharmacological cardioversion in case of atrial fibrillation.
Inotropic support should be initiated as soon as replacement of the initial 1 to 2 L of volume appears ineffective in restoring hemodynamics. The preferred agent is Dobutamine, which has the property of being an inodilator and does not produce constriction of the lung bed, which would be undesirable in these circumstances. Milrinone sulfate is also an option for treatment, taking advantage of its good effect to reduce pulmonary vascular resistance that may accompany the clinical picture in some patients. Clinical and hemodynamic criteria may make it permissible to use any of the currently available inotropes if circumstances justify it.
Reducing right ventricular afterload is a priority in cases where it is secondary to left ventricular dysfunction and in these cases sodium nitroprusside or intra-aortic balloon pump or ACE inhibitors could be used.
Reperfusion should be a priority in this subgroup of patients and can be achieved by thrombolytic agents, primary angioplasty, or revascularization surgery in selected patients with multivessel disease.
Additionally, the complications that may arise from these infarctions must be treated, such as: shock, high-grade AV block, atrial fibrillation, high-grade ventricular arrhythmias, rupture of the interventricular septum, formation of intraventricular thrombi and pulmonary embolisms, tricuspid insufficiency, pericarditis and shunt from right to left through the Foramen Ovale that causes hypoxemia that does not improve with oxygen.
Prognosis of right ventricular MI
The presence of right ventricular involvement associated with inferior infarction causes its usual in-hospital mortality to increase from 6% to 31%. The long-term prognosis is good and depends more on the involvement of the left ventricle. Right ventricular function usually returns over time.
Bibliography
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