Ischaemic ventricular aneurysms: true or false?

Left ventricular aneurysm is a common complication of acute myocardial infarction. The reported incidence ranges from 4%, if the definition is restricted to a localised protrusion of the extemal aspect of the left ventricle, to 40%, if localised akinesia or dyskinesia during systole is the criterion.' It has become a common clinical practice to classify ven-tricular aneurysms with an external bulge as true or false.23 The wall ofthe true aneurysm is derived from the myocardium itself whereas the wall of the false aneurysm (pseudoaneurysm) is derived from the pericardium (figure). The pseudoaneurysm is thought to be the result of a "near miss" myocardial rupture during an acute infarct with the formation of a subpericardial haematoma.' An acute pericarditis develops and fibrous thickening of the pericardium encompasses the haematoma, ultimately forming the free wall of a sac that connects by a narrow aperture with the left ventricular cavity. The designation of true or false applies solely to the postulated origin of the wall of the sac; both are aneurysms as defined as an external bulge filled with pulsating blood. Although pseudoaneurysms were first described at necropsy, this approach cannot either establish the frequency of pseudoaneurysms in living patients or define the risk of rupture. Basic principles suggest that the risk that a haematoma retained only by the visceral pericardium will rupture fatally within a day or two must be very high; long term survival with the formation of a pseudoaneurysm would accordingly be rare. Two series composed of nine pathologically proven cases of pseudoaneurysm, in which echocar-diography had been carried out in life, laid down criteria for the diagnosis.27 The diagnostic echocar-diographic features were that the maximal intemal diameter of the neck (O max) was less than the maximal parallel intemal diameter of the sac (D max) and that the ratio 0 max/D max never exceeded 0-5. The ratio for true aneurysms was > 1. A paper in this issue of the British Heart Journal8 challenges the view that pseudoaneurysms can be diagnosed in life with such confidence. Four lesions that conformed to the echocardiographic criteria of "false aneurysms" (pseudoaneurysms) were found to be "true" aneurysms when their wall was subsequently examined histologically. The histological criteria used to establish the myocardial origin of the aneurysm wall were the presence of residual islands of myocytes and coronary arteries draping the external surface of the sac. B3oth criteria are established as the morphological …