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?
Correct 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.
References:
A 34-year-old female with a history of rheumatic heart disease presents for mitral valve replacement. Preoperative echocardiography demonstrates a transmitral gradient of 14 mm Hg, a mitral valve area of 0.9 cm2 , and an underfilled left ventricle with normal function. Electrocardiogram shows atrial fibrillation.
What is the most likely finding on postoperative transesophageal echocardiography following mitral valve replacement in this patient?
Correct Answer: C
Left ventricular preload (left ventricular end diastolic volume) is decreased in chronic mitral stenosis leading to deconditioning of left ventricle with time. Following mitral valve replacement, the abrupt increase in preload frequently unmasks left ventricular dysfunction requiring temporary postoperative inotropic support. The transpulmonary gradient is the difference between the mean pulmonary artery pressure and the left atrial pressure. Following mitral valve replacement, both values drop (mean pulmonary artery pressure decreases more than the left atrial pressure), thus the transpulmonary gradient decreases. Right ventricular function will typically improve because of the decreased transpulmonary gradient. This may reduce the degree of tricuspid regurgitation (typically due to right ventricular dilation). In the presence of a prosthetic mitral valve, the transmitral gradient is typically less than 6 mm Hg. A higher gradient is concerning patient prosthesis mismatch (the prosthetic valve is too small for the size of the patient).
Mitral stenosis is typically secondary to rheumatic heart disease. In approximately 40% of patients, mitral stenosis occurs with mitral regurgitation. The second most common valve affected is the aortic valve followed by the tricuspid valve. The time course between rheumatic fever and obstructive mitral valve disease can vary from a couple years to more than 20 years. Rheumatic heart disease causes characteristic changes in the mitral valve including leaflet-edge thickening, chordal shortening and fusion, and commissural fusion. The normal mitral valve area is 4 to 6 cm2 . Mild mitral stenosis occurs as the mitral valve area drops below 2 cm2 , and stenosis is severe with a mitral valve area of less than 1 cm2 . Mitral stenosis leads to increased left atrial pressures, left atrial dilation, and increased pulmonary venous, capillary, and ultimately arterial pressures. Anything that increases blood flow across the stenotic mitral valve (tachycardia due to exercise, anemia, infection) will increase the pressure gradient (modified Bernoulli equation: pressure gradient = 4*velocity 2 ) and worsen pulmonary congestion. Atrial fibrillation reduces cardiac output by eliminating the atrial contribution to diastolic filling leading to increased left atrial pressure and worsened pulmonary congestion. Atrial fibrillation in patients with mitral stenosis begins intermittently and progresses to persistent atrial fibrillation overtime as the left atrium continues to dilate.
A 48-year-old male with a history of hypertension, patent foramen ovale, coronary artery disease, and diabetes mellitus presents with increasing shortness of breath, wheezing, peripheral edema, diarrhea, and headache. Transthoracic echocardiography shows severe tricuspid regurgitation, severe mitral regurgitation, and evidence of right ventricular failure. The subvalvular apparatus of the tricuspid and mitral valves appear thickened.
What is the likely etiology?
Correct Answer: A
Neuroendocrine tumors are rare tumors arising primarily in the gastrointestinal tract (67.5%) and the bronchopulmonary system (25.3%). These tumors may secrete many different products, including 5- hydroxytryptamine (5-HT, serotonin), prostaglandins, histamine, substance P, and transforming growth factor-β. These vasoactive substances are typically metabolized in the liver; however, when metastasis form and bypass this metabolism, systemic symptoms can develop. Approximately half of patients with neuroendocrine tumors will develop carcinoid syndrome, characterized by cutaneous flushing, diarrhea, and bronchospasm, and only 20% to 30% of those patients will develop carcinoid heart disease. The neuroendocrine products cause deposition of plaques along the endocardial surfaces of the valve leaflets, chordae tendinae, papillary muscles, and walls of the heart. These deposits primarily form on the ventricular aspect of the valves. The most common valve involved is the tricuspid valve because of the metabolism of the products in the pulmonary circulation. This can result in tricuspid regurgitation or a combination of tricuspid regurgitation and stenosis. The mitral valve can be involved in the setting of a patent foramen ovale, in which case the vasoactive substances bypass the lung. Carcinoid heart disease can present with signs and symptoms of right ventricular failure including dyspnea, peripheral edema, and liver disease; however, not all patients with carcinoid heart disease present with symptoms. The most common cause of death in these patients is right ventricular failure, and the second most common cause is tumor progression.
Mild tricuspid regurgitation is common in patients with a normal right ventricle and tricuspid valve. However, various pathologies can contribute to an increased severity of tricuspid regurgitation. The most common cause of tricuspid regurgitation is right ventricular dilation, which causes dilation of the tricuspid annulus (secondary/functional tricuspid regurgitation). Typically, a right ventricular systolic pressure of 55 mm Hg or greater will cause functional tricuspid regurgitation. Other causes include rheumatic and carcinoid heart disease, endocarditis, Ebstein anomaly, connective tissue disease (Marfan), and rheumatoid arthritis. Tricuspid regurgitation is well tolerated in patients with no evidence of pulmonary hypertension or right ventricular failure; however, tricuspid regurgitation in the setting of pulmonary hypertension can lead to heart failure and is associated with poor survival. Management of carcinoid heart disease involves diuretics and salt and water restriction. When severe, tricuspid valve replacement is the operation of choice. Because of the tricuspid valve restriction in addition to the calcified and diseased subvalvular apparatus, a tricuspid valve repair is not an option.
Reference:
A 78-year-old female presents with a femur fracture following a fall. She is persistently hypotensive in the ICU before surgery for open reduction internal fixation. Transthoracic echocardiography demonstrates the following continuous wave Doppler waveform:
What is the most likely diagnosis?
The left ventricular outflow tract gradient of hypertrophic cardiomyopathy is characteristically dagger-shaped. The waveform has a convex to the left orientation initially, which switches to concave to the left on the initiation of obstruction. This concave to the left orientation occurs because of the increased acceleration across the outflow tract, which is progressively narrowing (outflow obstruction). This increased acceleration does not occur with a subaortic membrane because the subaortic membrane causes a fixed and not dynamic obstruction. The gradient waveform through the aortic valve in patients with aortic stenosis is symmetric and demonstrates a convex to the left formation until the peak velocity. Severe aortic insufficiency may cause increased gradients as well, because of the increased flow through the aortic valve, which is the sum of the flow from the left atrium and the regurgitant flow from the aortic valve. According to the modified Bernoulli principle (4V2 , where V is peak velocity), this increased velocity will increase the transvalvular pressure gradient.
Transthoracic apical 5-chamber view with continuous wave Doppler. Difference between fixed obstruction of the left ventricular outflow tract due to aortic stenosis and dynamic obstruction of left ventricular outflow tract in left ventricular obstructive hypertrophy.
A 78-year old female with severe aortic stenosis presents to the ICU following a transcatheter aortic valve replacement (TAVR). Preprocedural transthoracic echocardiography demonstrated severe aortic stenosis with left ventricular hypertrophy and an asymmetric septal bulge. Left ventricular wall thickness in the parasternal short axis view is 1.6 cm with a small cavity. Postoperatively, the patient develops sudden onset hypotension requiring vasopressor support; however, blood pressure continues to decrease despite escalating doses of norepinephrine.
The vital signs are:
Transthoracic echocardiography demonstrates an underfilled left ventricle with midventricular obstruction.
Hypotension following TAVR can be due to hypovolemia, acidosis, bleeding, myocardial infarction, acute heart failure, cardiac tamponade, aortic root injury, severe paravalvular leak, or dynamic intracavitary gradients. The abrupt release of the fixed aortic obstruction following TAVR can result in improvement in ventricular function. This increased inotropy can precipitate hypertrophic cardiomyopathy–like physiology in these severely hypertrophied ventricles. Patients with small left ventricular end diastolic diameters, asymmetric hypertrophy, high-valve gradients, and increased ejection fraction have an increased risk of dynamic intracavitary gradients. When these gradients are associated with acute hypotension and cardiovascular collapse, the term “suicide left ventricle” has been used. Treatment mirrors the treatment for the left ventricular outflow tract obstruction seen in hypertrophic cardiomyopathy. The most appropriate first choice in this patient’s management is correction of hypovolemia with fluid bolus administration. If hypotension persists despite increased preload, the catecholamine agents should be avoided and noncatecholamine vasopressors (phenylephrine, vasopressin) should be used. Beta blockers may be useful as well to decrease inotropy and allow ventricular filling, in the absence of hypotension.
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