A 38-year-old female with a history of mitral valve prolapse presents to the cardiac ICU following a mitral valve repair. The intraoperative course was significant for two periods of cardiopulmonary bypass because of a failed first repair. The patient’s hemodynamics is supported with a low-dose norepinephrine infusion. Following turning the patient in bed, there is an acute decrease in blood pressure refractory to treatment with multiple boluses of norepinephrine and phenylephrine. Emergent transthoracic echocardiography at the bedside demonstrates severe right ventricular dysfunction, in addition to new onset inferior and inferoseptal wall motion abnormalities.
What is the most appropriate next step in management?
A. Left-heart catheterizationCorrect Answer: D
During cardiopulmonary bypass for operations that involve opening to left atrium, air is introduced into the left-sided cardiac chambers. On separation from cardiopulmonary bypass, transesophageal echocardiography can be used to ensure adequate de-airing of the leftsided structures. Air is typically found near the pulmonary veins, left atrial appendage, along the atrial septum, and near the left ventricular apex. If the cardiac chambers are not adequately de-aired, air can enter the aorta and subsequently embolize to the coronary, cerebral, or systemic circulations causing ischemic complications. If air enters the coronary circulation while the patient is in the supine position, air preferentially enters the right coronary circulation because it has the most anterior coronary ostia. In addition, air may enter saphenous vein grafts because they are typically anastomosed to the anterior portion of the aorta. Although this is most likely to occur in the operating room, residual air can dislodge during transport or even in the ICU, particularly with a change in body position or turning. This 38-year-old patient likely does not have significant coronary artery disease, and a left-sided heart catheterization would not be the immediate next step in management. The most likely explanation is residual intracardiac air embolizing to the right coronary artery circulation. Intracoronary air can range from asymptomatic to complete hemodynamic deterioration and cardiac arrest, depending on the amount of air. Inotropic and vasopressor agents should be used to augment the blood pressure and cardiac output, thus flushing the air through the coronary circulation while monitoring ST segments for resolution. If resolution does not occur, other causes of postoperative STsegment elevation should be evaluated.
Another unique cause of ST-segment elevation following mitral valve surgery involves surgical occlusion of the left circumflex artery. The left circumflex artery lies within the left atrioventricular groove and courses along the posterior border of the mitral valve. In left dominant circulation when the left circumflex gives rise to the posterior descending artery, the circumflex courses even closer and along the entire posterior annulus of the mitral valve. Owing to this anatomic relationship, the surgical sutures may cross through the circumflex artery and cause iatrogenic ischemic injury. EKG and hemodynamic changes postoperatively will depend on the level of obstruction. Proximal circumflex injuries may lead to lateral and inferior wall ischemia; however, a distal circumflex injury in a patient with a left dominant circulation may present with only inferior wall ischemia.
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