Discussion
Congenital LV diverticulum is a rare cardiac anomaly with 0.42% prevalence in adults and may range from 5 to 90 mm, with normal LV systolic function 5-7 . It is thought to occur early in embryogenesis, emerging from an outer pouching of the endomyocardium through a weak LV segment. On cardiac imaging, LV diverticulum appears like an outer sac arising from the LV wall, the ratio of the connecting neck compared with the maximum diameter of the diverticulum varies, always less than 17. LV diverticulum may be associated with midline thoracoabdominal defects, other congenital cardiac malformations, or can be isolated without intracardiac and extracardiac anomalies8,9. In isolated LV diverticulum, the patient is usually asymptomatic or may have overlapping symptoms of heart failure, chest pain, or dyspnea as seen in both aneurysms and pseudoaneurysms. And complications like embolism, infective endocarditis, arrhythmia and, rarely, rupture can be the initial presentation 2,3,5.
Cardiac imaging is the most powerful tool for diagnosing LV diverticulum and for differentiating it from aneurysms especially pseudo-aneurysms, and delayed enhancement cardiac MRI is the most recently recommended10-12. LV diverticulum is usually classified into two types, fibrous and muscular types. Muscular type contains all three muscle layers with normal contractile function and is not prone to rupture, and is easier to differentiate from true-aneurysms which always accompany akinetic or dyskinetic wall complicating myocardial infarction. The fibrous type diverticulum, with complete absence of myocardium is usually located at the cardiac base or at the subvalvular area, making it difficult to differentiate from pseudo-aneurysms2,7,13. The LV pseudo-aneurysm is usually caused by cardiac rupture with discontinuity of the ventricular wall, and is encircled by adherent pericardium or scar tissue, with no myocardial tissue. The cause of pseudo-aneurysms includes acute myocardial infarction (AMI), endocarditis, trauma, iatrogenic operation (cardiac surgery, intervention), purulent pericarditis 14-17. Over 50% of cases are due to AMI, and the most common location is the posterior and inferior wall.
Our patient denied any previous cardiac medical history, the coronary arteries were normal without any evidence for atherosclerotic disease and all other imaging investigations including; echocardiography, MRI, left ventriculography and surgery confirmed the presence of the LV pseudo-aneurysm. There were only few cardiomyocytes in the whole layer of the ventricular wall on histology. Based on the history and imaging findings, we believe that the most accurate diagnosis of this case is the ruptured LV diverticulum causing pseudo-aneurysm which was complicated with a large thrombus and pericardial effusion. Since the LV systolic function was preserved and the patient was hemodynamically stable, the surgical repair with patch was successful.