Left Ventricular Pseudoaneurysm: An Unusual Complication of Pericarditis and Staphylococcus Aureus Septicemia

Staphylococcus aureus septicemias in children are severe infections that may involve the heart, leading to pericarditis or endocarditis.1 Ventricular pseudoaneurysm has rarely been described under these circumstances. Pseudoaneurysm is an uncommon result of a left ventricular wall rupture. The hemorrhage that follows the myocardial rupture is restricted in its extent by the adherent pericardium. With each heart contraction blood erupts into the aneurysmal sac causing gradual dilation of the fibrous wall while the size of the hole in the ventricular wall remains unchanged.2 Even a small pseudoaneurysm can rupture and cause sudden death.3 The diagnosis may be of critical importance for the early surgical repair which consists of evacuating the sac and suturing the defect in the myocardium.4 We report a case of pseudoaneurysm of the left ventricle caused by septic pericarditis after staphylococcal osteomyelitis and septicemia. Case report. An 8-year old black male was admitted to the Emergency Room with right hip pain and high grade fever after a closed trauma to the right thigh 6 days earlier. Swelling and redness were observed. The patient was febrile and lethargic, with pain during active and passive movement of the right hip joint. A joint puncture disclosed a seropurulent fluid and surgical drainage was performed. S. aureus was identified in this material as well as in the blood culture. Oxacillin (200 mg/kg/day) and amikacin (15 mg/kg/day) were administered for the first 14 days. On the third day of hospitalization signs of pulmonary consolidation were noted, and a chest roentgenogram revealed bilateral bronchopneumonia. On the fifth day the patient became tachycardic with weak heart sounds. A two-dimensional Doppler echocardiogram showed pericardial effusion. Surgical drainage revealed a suppurative hemorrhagic fluid; however, the culture was sterile. A rigid chest tube was introduced and maintained in the anterior precordial region for 2 days. Fever persisted in spite of improvement of the pulmonary infection, and the patient looked well. Computed tomographic scanning of the right hip joint revealed femoral osteomyelitis. At the end of the second week of hospitalization, oxacillin therapy was replaced by vancomycin (60 mg/kg/day) while amikacin was continued. Control echocardiograms, performed once every 7 days, showed small thickening of the pericardium without involvement of other structures. On the 19th day of hospitalization the fever started to fall, diminishing intensity and frequency. On the 40th day, 7 days after the last echocardiogram, a systolic murmur of moderate intensity was heard over the left border of the sternum, in the third and fourth intercostal spaces. A chest radiograph showed enlargement of the cardiac area with blurring of the left border of the heart. The Doppler echocardiogram showed myocardial rupture located in the posterior free wall of the left ventricle (near the subvalve portion of the mitral valve), with formation of a large pseudoaneurysm circumscribed by the pericardium. The color Doppler demonstrated bidirectional turbulent flow in the neck of the pseudoaneurysm. Chest computed tomographic scanning showed a paracardiac mass beside the left ventricle. Magnetic resonance imaging (MRI) (Fig. 1) confirmed the diagnosis, demonstrating with sharp definition the abrupt discontinuity of the posterior left ventricular wall close to the mitral valve. The patient was submitted to aneurysmectomy with myocardial suture without complications. During surgery rupture of the left ventricular wall was observed next to the subvalvar portion of the mitral valve, which communicated with a cavity of approximately 3.5 by 5.5 cm surrounded by thick pericardium. There were no blood clots in its interior. The mitral valve as well as adjacent myocardium were normal. Histologic examination of the resected tissue showed a wall of fibrous tissue with no adjacent thrombus and absence of myocardial cells. The postoperative course was uneventful. Antibiotics were discontinued 10 weeks after admission. Cardiac function and echocardiographic examinations remained normal 1 year after hospital discharge. Discussion. Ventricular pseudoaneurysm is a rare entity. In children it follows a myocardial rupture secondary to trauma, whereas in adults it is observed predominantly after myocardial infarction.1, 3, 5, 6 Other causes include congenital heart disease, syphilis, tuberculosis and Chaga's disease.6 Staphylococcal infection as a cause of ventricular pseudoaneurysm is extremely rare.2, 7, 8 Onset generally occurs in the endocardium, spreading thereafter to the myocardium, more frequently as a result of a ring abscess.2, 9 Isolated pericarditis is rarely described as the onset of the process, and to our knowledge it has seldom been described in the pediatric literature.7 The possibility of the occurrence of a mitral endocarditis in our patient seems highly unlikely because echocardiograms periodically performed did not show alterations. During surgery the mitral valve was normal. Ventricular pseudoaneurysm may also occur as a result of intramyocardial abscess formation in the setting of septicemia.10 However, no echocardiographic or MRI findings pointing to that condition were present in our patient. Myocardial lesion, secondary to the thoracic drainage, also seems unlikely because the rupture was identified in the posterior wall of the left ventricle, whereas the chest tube was introduced into the anterior cardiac region. In our case pericardial infection probably spread to the myocardium with subsequent rupture, as described previously.2 Thickness and adhesion of the pericardium as a result of the inflammatory process prevented death that could have occurred as a consequence of a massive hemopericardium.11 The late appearance of the aneurysm suggests a vulnerable period simultaneous with or after acute staphylococcal infection during which the strength of the cardiac wall is reduced and myocardial rupture is more likely to occur.2, 7 Our case illustrates the nonspecific signs and symptoms that may accompany the occurrence of pseudoaneurysms. Abnormalities include murmurs, abnormal precordial movement and signs of congestive heart failure.10 The thoracic roentgenogram and the electrocardiogram are nonspecific. Doppler echocardiogram, color Doppler and MRI showed the ventricular wall rupture.12, 13 The size, character and location of the pseudoaneurysm and its communication with the left ventricle were clearly identified as well. Two-dimensional echocardiography may be useful in detecting ventricular pseudoaneurysm but sometimes does not distinguish it from loculated pericardial effusion, true aneurysms or pericardial cysts.14, 15 Color Doppler is superior not only by demonstrating the blood flow into the pseudoaneurysm but also in assessing the volume and pressure gradients. With the help of MRI one has the advantage of being able to define the size and location of associated myocardial lesions as well as clots within the aneurysmal sac.4 While true aneurysms are composed of myocardial scar tissue, the wall of pseudoaneurysms is composed of fibrous tissue and pericardium and carries a higher risk of unpredictable rupture and sudden death.12 Other complications include congestive heart failure, arrhythmias and embolic phenomena. Prompt diagnosis and surgical intervention are essential for a favorable outcome.10 In summary we have described the occurrence of a ventricular pseudoaneurysm in a child with staphylococcal septicemia and pericarditis after 30 days of apparent favorable clinical outcome. The color Doppler echocardiogram, computed tomographic scanning and MRI were essential for the diagnosis of this rare complication. This case as well as the other two reported in the literature2, 7 clearly show that a prolonged follow-up with serial Doppler echocardiograms may be important for patients with staphylococcal pericarditis. Márcia Melo Campos Pahl, M.D.; Julio Arruda, M.D.; Alfredo Elias Gilio, M.D.; Bernardo Ejzenberg, Ph.D.; Evandro Baldacci, M.D., Ph.D.; Yassuhiko Okay, M.D., Ph.D. Department of Pediatrics Hospital Universitário Universidade de Sao Paulo Sao Paulo, BrazilFIG. 1: MRI axial view, showing five cardiac chambers, the fifth close to the left ventricle (LV), formed by the pericardium, confirming the diagnosis of ventricular pseudoaneurysm (PVA). The rupture of the myocardium (large arrow) is located near the mitral valve (small arrow).