The Gerbode defect is a rare form of intracardiac shunt from the left ventricle to the right atrium. It results from a defect in the membranous portion of the interventricular septum. It can be congenital or acquired. The acquired form is more frequent and can be caused by previous heart valve surgery, infective endocarditis, trauma, and myocardial infarct; the postoperative cause is the most frequent. It is also more prevalent in male and it is common after procedures involving the interventricular septum or close structures and when aggressive debridement is done. The incidence of the Gerbode defect after surgical procedures is 0.65% and should be suspected when there is circulatory failure after a cardiac surgery. A high suspicion must be maintained, especially if predisposing factors, such as severe calcific valve disease and mediastinal radiation, are present. There are three types of Gerbode defect: type 1 or indirect, type 2 or direct, and type 3. The type 1 is an infravalvular defect in the interventricular part of the membranous septum, corresponding to 76% of the cases; type 2 or direct is a supravalvular defect in the atrioventricular part of the membranous septum; type 3 is a combination of types 1 and 2. The most common symptoms are fever and dyspnea. Cardiac murmur is mostly systolic, grade III or IV in the left sternal border, but it can also be systolic and diastolic. Associated disorders include heart failure, cardiac chamber dilatation, and valve insufficiency.
A 48-year-old female patient, with rheumatic valvar disease, was submitted to a mitral valve replacement with a biological prosthesis 22 years ago. A trans-thoracic echocardiogram was performed and showed rupture of one leaflet of the prosthetic mitral valve. The patient was then submitted to another mitral valve replacement and received a mechanical prosthesis. In the postoperative period, a trans-thoracic echocardiogram showed a shunt between the left ventricle and the right atrium, important tricuspid regurgitation, left and right ventricles with normal function, FEVE 68%, TAPSE 17 mm, and PSAP 80 mmHg. She was then submitted to a third cardiac surgery to correct the Gerbode defect. She was admitted in the operating room oriented, alert, hemodynamically stable. She was monitored with cardioscopy, pulse oximetry, invasive arterial pressure, and trans-esophageal echocardiogram. A peripheral venous access and a central venous line were punctured. Anesthetic induction was performed with etomidate 20 mg, midazolam 5 mg, sufentanil 50 μg, and rocuronium 50 mg and was maintained with sevoflurane. The defect was corrected with a bovine pericardial patch, and a tricuspid repair was also made with an inorganic pericardial patch. The cardiopulmonary bypass lasted for eighty minutes. When transitioning to pulsate circulation, the patient presented total atrioventricular blockade. An epicardial pacemaker was placed. Bleeding was increased after the cardiopulmonary bypass period and the patient received red blood cells and platelets. Methadone was administered for postoperative analgesia. The patient was sent to the ICU, sedated and intubated with continuous noradrenaline and dobutamine. The patient was extubated after 6 h in the ICU and recovered with no complications.
Gerbode leads to a shunt from the left ventricle to the right atrium during systole because of the great pressure gradient between these two chambers. The greater blood flow to the right atrium leads to a higher flow to the right ventricle. The result of this shunt is an enlargement of the right cardiac chambers, pulmonary hypertension, right heart failure, pulmonary congestion, and a low cardiac output. If this defect causes an acute accumulation of blood in the right atrium, it is possible that the flow direction reverses in the diastolic phase of the left ventricle. The anesthetic goals for these patients involve maintaining hemodynamic and respiratory stability. A raise in the pulmonary vascular resistance should be avoided and hypoxemia, hypoventilation, anemia, acidosis, and hypercapnia cannot occur. To better manage pulmonary hypertension and right ventricular dysfunction, it is important to adopt strategies that permit to optimize rate and rhythm, raise right ventricle preload and contractility and to reduce right ventricle afterload. A higher heart rate should be maintained, because it improves cardiac output, reduces right ventricle overload and tricuspid regurgitation. When sinus rhythm is kept, the atrial performance is enhanced and ventricular preload is optimized. Volume status must be optimized with caution. Pulmonary vasodilators, such as nitric oxide, can be used to reduce afterload and should be preferred as it reduces the risk of systemic hypotension and ventilation–perfusion mismatch. The systemic vascular resistance should be maintained and the pulmonary vascular resistance should be kept in lower values when compared to systemic vascular resistance. An adequate systemic arterial pressure will provide a better right coronary artery perfusion and contribute to the right ventricle function. Norepinephrine and vasopressin are effective vasopressors; however, vasopressin leads to a lower increase in the pulmonary vascular resistance when compared to norepinephrine. Dobutamine enhances the right ventricle function and the phosphodiesterase III inhibitors can also improve its contractility and reduce the pulmonary vascular resistance improving the right ventricle performance. Nebulized milrinone has been increasingly used, since it causes less systemic hypotension and less disturbances in the ventilation–perfusion matching. Levosimendan may also be useful for improving the right ventricle function, because it improves contractility without raising oxygen demand. The trans-esophageal echocardiogram is essential for diagnosis and confirmation of successful repair of the shunt. The defect can be visualized in the following views: mid-esophageal 4 chambers, mid-esophageal right ventricle inflow–outflow, and mid-esophageal reversed 4 chamber view (130–160°). It is essential to see the origin of the blood flow shunt to confirm the Gerbode defect and to make deferential diagnosis with severe pulmonary hypertension. To make differential diagnosis, it is vital to correctly identify a Gerbode defect, which presents with: normal pulmonary diastolic arterial pressure, atypical jet direction, shunt during systole, lack of ventricular septal flattening, and no right ventricular hypertrophy. The treatment strategy should be individualized, according to the patient comorbidities and features of the defect. The surgical treatment for acquired defects is more common. Percutaneous closure of this defect is also possible and can result in hemolysis and acute kidney injury; in spite of that, it is an effective plan for high-risk patients. Complications include heart block, residual shunt, infective endocarditis, hemolysis, respiratory insufficiency, and atrial fibrillation. In conclusion, this case report brings up a rare disease with so many particularities that should be remembered when caring for these patients in order to pursue a better outcome.
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