Ruptured pseudoaneurysm of the mitral-aortic intervalvular fibrosa as a sequelae of left ventricular outflow endocarditis mimicking an acute aortic root dissection in a 20 year old male with bicuspid aortic valve

Tóm tắt

Background

Mitral-aortic intervalvular fibrosa (MAIF) is a fibrous region located between the anterior mitral leaflet and noncoronary cusp. Pseudoaneurysm of the mitral-aortic intervalvular fibrosa (P-MAIF) is a rare and potentially fatal entity usually associated with aortic or mitral valve surgery. However, P-MAIF as a subaortic complication of native aortic valve endocarditis can occur.

CASE SYNOPSIS

A 20 year-old male with no apparent cardiovascular illness presents with fever, angina and orthopnea. Pertinent PE findings were pericardial friction rub, pulsus paradoxus and muffled heart sounds. On 2D-echocardiogram, a bicuspid aortic valve with mobile vegetation and massive pericardial effusion with tamponade physiology was noted. Emergent pericardiostomy and drainage was performed. Pericardial sample and blood cultures yielded a positive culture for methicillin-resistant coagulase-negative Staphylococcus aureus. Initiation of a 6-week IE regimen of IV vancomycin was then initiated. Lysis of fever and remission of heart failure ensued 5 days post operatively.

On the third week of hospital admission, the patient had recurrence of angina with hypotension. Repeat 2D-echocardiogram depicted an aortic root dissection. Impression on CT aortogram was a short segment ascending aortic dissection; however, P-MAIF was also considered. Pericardiotomy and repair of a ruptured P-MAIF draining into the posterior transverse sinus was then performed via pericardial patching.

DISCUSSION AND SIGNIFICANCE

Pseudoaneurysm of the mitral-aortic intervalvular fibrosa (P-MAIF) is a rare complication of infective endocarditis. Aortic valve infections may directly extend into the MAIF area. Because of the avascular nature of this intervalvular fibrosa, this region is more prone to injury and infectious insults. The proposed mechanism is through continuous impinging of an infected aortic regurgitant jet on this vulnerable region. Bicuspid aortopathy is also a predisposing factor for this sequelae because it causes an innate congenital weakness of the MAIF.

CONCLUSION

Transthoracic echocardiography remains the first-line imaging modality for suspected periaortic abscess or other IE complications but only has 43% sensitivity. Transesophageal echocardiography has a higher sensitivity rate of 90%. A pulsatile echo-free sac that expands during systole and collapses on diastole is the typical echocardiographic finding. Multimodality imaging aided in the accurate interrogation of structures and arrival at this complex diagnosis.