Reprinted by permission from Primary Cardiology, January 1995.
Olga Shindler MD, Alan Spotnitz MD, Daniel Shindler MD
A 66 year old female was referred for cardiac catheterization 3 months after acute myocardial infarction. During the ventriculographic injection dye was noted in the pulmonary artery, indicating the presence of shunt between the left ventricle and the right cardiac chambers. Oxygen step-up confirmed a ventricular septal defect and the patient was referred for an echocardiogram to further determine the anatomic features of the ventricular septal defect. On transthoracic echocardiography color Doppler showed a shunt from the left ventricle to the right ventricle. There was also evidence of a basal inferior aneurysm. The question then arose whether this was a true aneurysm or a pseudoaneurysm with actual rupture into the pericardial space. Transesophageal echocardiography was performed to answer this question. It showed thinning of the posterior left ventricular wall with expansion into an aneurysmal chamber. Doppler showed that the direction of blood flow was from the left ventricular cavity into the aneurysmal chamber and from there to the right ventricular cavity. Intravenous contrast injection of agitated saline opacified the right ventricular chambers without appearance of contrast in the aneurysmal chamber or in the left ventricle. Therefore, there was no right to left shunt. Chilled, agitated 5% albumin was injected intravenously with transpulmonary passage, appearing in the left ventricular cavity and then in the aneurysmal pouch. Since the right ventricular cavity was still filled with contrast it was not possible to establish whether any of the contrast was shunting from the aneurysmal chamber to the right ventricular cavity. The contrast density in the aneurysmal chamber appeared similar to the ventricular cavity contrast pattern. There was also no difference in the degree of contrast swirling in these two chambers indicating similar flow patterns. The duration of contrast effect was also no different in the aneurysmal pouch compared to the left ventricle. This suggested that the pressures in both chambers were similar since these particular albumin contrast bubbles implode and disappear with the usual systolic pressures of the left ventricular cavity. The patient was referred for open heart surgery where, indeed, it was confirmed that this was a true, rather than a false aneurysm. The ventricular septal defect connected from the aneurysmal portion (external to the original left ventricular perimeter) to the right ventricle. It was closed with a patch after the aneurysm was resected.
This case illustrates several important points about the important diagnostic role of echocardiography in complications of acute myocardial infarction. Echocardiography was employed following cardiac catheterization because of its unique ability to image the left ventricular walls as well as the pericardial space. The echocardiographic information supplemented the knowledge about the left ventricular cavity gained during cardiac catheterization. The combination of Doppler and contrast echocardiography further enhanced the anatomic information gained from 2D echo. An important distinction between a true and false aneurysm is the size of the neck connecting the ventricular cavity with the aneurysmal portion. In this case the 2D appearance was misleading. It was complemented by the Doppler and contrast information. Doppler showed flow from the ventricular cavity to the aneurysm. Contrast suggested that the pressures in the two chambers were similar with no evident stasis in the aneurysmal portion. The combination of ventricular septal defect with the aneurysm precluded the diagnostic value of Doppler. The blood in the aneurysm circulated to the right ventricle. Doppler showed systolic flow into the aneurysm. The diastolic reflow pattern is usually helpful in distinguishing true from pseudoaneurysm. In this case, the unloading of the aneurysm into the right ventricle (through the ventricular septal defect) decompressed the aneurysm. As a result, there was no diastolic reflow between the aneurysm and the left ventricle. Nevertheless, even with the use of contrast not all questions were answered. For example, the presence of contrast in the right side chambers made it impossible to comment on left to right passage of contrast. Fortunately, color Doppler was used for that purpose. On the other hand, the property of this contrast preparation of imploding with high left ventricular pressures allowed some speculation about the pressures in the aneurysm compared to the pressure in the left ventricle. Albumin contrast appears as faint linear reflections with a swirling pattern and a limited life span. It is easy to time the duration of contrast effect by simply reviewing the video tape frame by frame. Visual inspection allows differentiation between a swirling contrast pattern such as is seen in patients with left atrial stasis or with echo guided pericardiocentesis. In the pericardium contrast movement is slow and swirling and has a longer half life. Conversely, contrast flow in an aneurysm directly connected to the left ventricular cavity has, as in this patient, a similar contrast flow pattern and half life. Transesophageal echocardiography further enhances the utility of ultrasound by providing high resolution images. This contrast technique (which does not require sonication) was capable of providing the above information thanks to the high resolution of transesophageal images. This case illustrates an important complication of myocardial infarction that has commonly been associated with progression to death. Surgery is routinely performed in patients with acute ventricular septal defects during myocardial infarction. In this patient the diagnosis was made three months after the actual infarction. She went to surgery on an elective basis. Conversely, had this been a pseudoaneurysm, surgery would have been considered mandatory. Thus, echocardiographic differentiation between a true and an pseudoaneurysm has important implications for the cardiac surgeon.
Now that albumin echo contrast is commercially available, it has the potential to help in this diagnosis.
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