Published online before print June 13, 2005, 10.1148/radiol.2361031699
(Radiology 2005;236:65-75.)
© RSNA, 2005
True versus False Left Ventricular Aneurysm: Differentiation with MR Imaging—Initial Experience1
Eli Konen, MD,
Naeem Merchant, MD,
Carlos Gutierrez, MD,
Yves Provost, MD,
Linda Mickleborough, MD,
Narinder S. Paul, MD and
Jagdish Butany, MD, FRCPC
1 From the Department of Medical Imaging (E.K., N.M., Y.P., N.S.P.), Toronto Lung Transplant Program (C.G.), and Department of Pathology (J.B.), Toronto General Hospital, University Health Network, Toronto, Ontario, Canada; and Division of Cardiovascular Surgery, University of Toronto, Ontario, Canada (L.M.). Received October 22, 2003; revision requested January 12, 2004; final revision received August 28; accepted September 29.
Address correspondence to E.K., Department of Diagnostic Imaging, Chaim Sheba Medical Center, Tel Hashomer 52621, Israel (e-mail: eli.konen{at}sheba.health.gov.il).
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ABSTRACT
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PURPOSE: To assess the usefulness of cardiac magnetic resonance (MR) imaging for differentiation of true from false left ventricular aneurysm in patients after myocardial infarction.
MATERIALS AND METHODS: Cardiac MR images obtained in 22 sequential patients (20 men, two women; mean age, 63 years; age range, 45–75 years) with pathologically proved left ventricular true aneurysm (n = 18) or false aneurysm (n = 4) after myocardial infarction were retrospectively analyzed. The MR imaging protocol included steady-state cine imaging followed by perfusion measurement and delayed contrast-enhanced imaging with delays of 15 and 20 minutes. Differences between true and false aneurysms with regard to maximal internal width of orifice, maximal parallel internal diameter, ratio of maximal orifice to maximal internal diameter, presence of mural thrombus and delayed enhancement of pericardium, left ventricular end-diastolic volume, and left ventricular ejection fraction were analyzed by using the Mann-Whitney U test or Fisher exact test, as appropriate.
RESULTS: Inferior wall location was noted in two of four patients with false aneurysm and in none of 18 patients with true aneurysm (P = .03). The remaining aneurysms were apicoanterior (two false, 10 true) or apical (eight true). False aneurysms had a ratio of maximal internal width of the orifice to maximal parallel internal diameter that was significantly lower than that of true aneurysms (0.73 vs 1.00, P < .001) and had a significantly higher left ventricular end-diastolic volume (median, 202 vs 136 mL/m2; P = .001), as well as a nonsignificant tendency toward lower left ventricular ejection fraction (17% vs 28%, P = .15). Mural thrombus was identified in all four patients with false aneurysm and in seven of 18 patients with true aneurysm (P = .09). Delayed enhancement of pericardium was noted in all four patients with false aneurysm and in three of 18 patients with true aneurysm. Resultant sensitivity of MR imaging for the detection of false left ventricular aneurysm was four of four, specificity was 15 of 18, accuracy was 19 of 22, and positive and negative predictive values were four of seven and 15 of 15 patients, respectively.
CONCLUSION: Initial experience with a small number of patients suggests that marked delayed enhancement of the pericardium is a characteristic feature of false aneurysm. Study with a larger patient sample is required to further assess this feature.
© RSNA, 2005
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INTRODUCTION
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False aneurysm of the left ventricle is a rare complication of myocardial infarction. It is defined as a rupture of the myocardium that is contained by pericardial adhesions. The result is the formation of a pseudoaneurysm that maintains communication with the left ventricular cavity. Unlike a true aneurysm, which contains some myocardial elements in its wall, the walls of a false aneurysm are composed of organized hematoma and pericardium and lack any element of the original myocardial wall. True aneurysms are likely to rupture only in the early postinfarction period and are often managed medically. Surgical repair is indicated only when there is associated congestive heart failure or arrhythmia, and it is successful only if there is relative preservation of contractile performance in the nonaneurysmal portion of the left ventricle. In contrast, false aneurysms, irrespective of their age, may rupture (1) and, thus, require surgical repair. Therefore, accurate differentiation between the two entities is clinically important.
Left ventricular angiography and echocardiography have been used to evaluate left ventricular aneurysms. Angiography, however, is an invasive procedure that incurs the risk of dislodging a potential thrombus within the aneurysm, while echocardiography often has a field-of-view limitation, especially in the left ventricular apex, where the majority of aneurysms occur. The role of cardiac magnetic resonance (MR) imaging in the evaluation of patients with ischemic heart disease is constantly growing. Cine MR imaging enables assessment of left ventricular morphology and function (2) and was recently suggested also to have an important role in pre- and postsurgical evaluation of patients with left ventricular aneurysm (3). In addition, delayed contrast material–enhanced MR imaging has been shown to be a promising technique for the delineation of myocardial viability (4–6). However, the role of cardiac MR imaging in the differentiation of true from false left ventricular aneurysm is still uncertain (7). Thus, the purpose of our study was to assess the usefulness of cardiac MR imaging for differentiation of true from false left ventricular aneurysm in patients after myocardial infarction.
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MATERIALS AND METHODS
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Patients
All 22 consecutive patients (20 men, two women; mean age, 63 years; age range, 45–75 years) with a suspected left ventricular aneurysm (18 true, four false) who were referred for cardiac MR imaging between July 1, 2001, and December 31, 2002, and who subsequently underwent surgical repair, were included in the present study. Cardiac MR imaging was performed in all patients for preoperative evaluation of left ventricular function, geometric distortion, and myocardial viability. In all cases, left ventricular aneurysm was previously suggested by findings at echocardiography and/or angiography. The indication for surgery in all patients was left ventricular failure. In all patients with this condition, aneurysmectomy was performed in conjunction with coronary artery bypass grafting. The patient's clinical information was reviewed by an experienced cardiac surgeon (L.M., 23 years of experience). Our institutional review board approved the retrospective evaluation of the patient's records and images and did not require the patient's informed consent.
MR Imaging
All MR imaging examinations were performed with a 1.5-T MR imager (CV/i; GE Medical Systems, Waukesha, Wis) by using a dedicated cardiac coil. Images were acquired with electrocardiographic gating and a steady-state cine technique (fast imaging employing steady-state acquisition) and with 3.7–7.1/1.4–3.1 (repetition time msec/echo time msec), in short-axis oblique, long-axis oblique, and transverse planes. This was followed by perfusion studies and delayed contrast-enhanced imaging. Perfusion studies were performed by using previously described methods (8) during intravenous injection of 10 mL of gadodiamide (Omniscan; Nycomed Imaging, Oslo, Norway) at a dose of 0.5 mmol/kg and a rate of 4 mL/sec with an automatic injector (Spectris; Medrad, Indianola, Pa). Delayed contrast-enhanced images were obtained after an additional injection of 0.2 mmol/kg gadodiamide at a volume of up to 20 mL by using an inversion-recovery-prepared breath-hold gradient-echo cine imaging sequence (5.4–7.1/1.4–3.1/200 [repetition time msec/echo time msec/inversion time msec]; flip angle of 25°; section thickness of 10–12 mm). Long-axis and short-axis oblique views were obtained 15 and 20 minutes, respectively, after the contrast agent injection. In four patients, additional contrast-enhanced fast steady-state cine images were acquired in selected planes as clinically indicated during the examination.
Image Evaluation
All MR images were retrospectively evaluated by two radiologists, an experienced staff member (N.M., 9 years of experience with cardiac MR imaging) and a fellow in cardiovascular MR imaging (E.K.), in consensus. Both reviewers were blinded to the patient's name and echocardiographic, angiographic, surgical, and clinical data. MR images were analyzed for the location of the aneurysm, the maximal internal width of the orifice, and the maximal parallel internal diameter by using previously published methods for echocardiographic measurements (9–11) and for the presence of mural thrombus. Since we had previously encountered a case of a postsurgical left ventricular false aneurysm with marked delayed enhancement of the pericardium, we assessed all 22 cases for the presence of this finding by using a subjective three-point scale: 0, no pericardial enhancement; 1, pericardial enhancement less than adjacent enhancing infarcted myocardium; and 2, pericardial enhancement equal to or greater than adjacent enhancing infarcted myocardium. In addition, the left ventricular end-diastolic volume and left ventricular ejection fraction were calculated from the cine MR images by an additional independent staff radiologist (Y.P., 3 years of experience with cardiac MR imaging) who was blinded to the clinical data and to other imaging findings. The calculations were obtained by using a workstation (Advantage for Windows, revision 4.0P; GE Medical Systems, Buc, France) and software (MRI-Mass; Medis, Leiden, the Netherlands). Calculated volumes were corrected for body surface area.
Pathologic Analysis
All patients underwent aneurysmectomy and reperfusion surgery. Pathologic examination of the resected aneurysm was performed in all cases by an experienced pathologist (J.B., 15 years of experience with cardiac pathology). The diagnosis of false left ventricular aneurysm was based on the presence of pericardial tissue and the absence of myocardial fibers. MR imaging findings were compared with the pathologic diagnosis, which served as the reference standard.
Statistical Analysis
Because the number of subjects with a false aneurysm was small (n = 4), the distribution of data for those subjects was assumed to be non-Gaussian. Differences between patients with true and false left ventricular aneurysms with regard to patient age, maximal internal width of the orifice, maximal parallel internal diameter, ratio of the maximal internal width of the orifice to the maximal parallel internal diameter, and calculated left ventricular end-diastolic volume and left ventricular ejection fraction were analyzed by using the Mann-Whitney U test; differences in the location of the aneurysm and presence of mural thrombus were analyzed by using the Fisher exact test. All tests were two tailed, and a P value of less than .05 was considered to indicate a statistically significant difference. Results were calculated and reported as the median, first quartile (ie, 25th percentile), and third quartile (ie, 75th percentile). Statistical analysis was performed by using software (SAS, version 8.04 for Windows; SAS Institute, Cary, NC). Sensitivity, specificity, accuracy, and positive and negative predictive values of pericardial delayed enhancement for the detection of false left ventricular aneurysm were calculated by defining an enhancement score greater than 0 as a positive result.
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RESULTS
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Cine MR imaging revealed in all cases a dyskinetic segment in the left ventricular wall, a finding suggestive of aneurysm. Patients with a false left ventricular aneurysm were significantly older (median age, 75.5 years; first quartile, 73.0 years; third quartile, 76.5 years) than patients with a true aneurysm (median age, 61.5 years; first quartile, 57.0 years; third quartile, 65.0 years) (P = .007). Inferior wall location was noted in two of the four patients with a false aneurysm (Figs 1, 2) and in none of the 18 patients with a true aneurysm (P = .03). The remaining false aneurysms were apicoanterior in location (n = 2), and the remaining true aneurysms were apical (n = 8) or apicoanterior (n = 10). The maximal internal width of the orifice and maximal parallel internal diameter did not differ significantly between the two groups, but the ratio of the maximal internal width of the orifice to the maximal parallel internal diameter was significantly lower (P = .001) in patients with a false aneurysm (Table 1, Figs 1–3) than in patients with a true aneurysm (Fig 4). A mural thrombus was noted in all four patients (100%) with a false aneurysm (Figs 1b, 2b, 3) and in seven (39%) of 18 patients with a true aneurysm (P = .09).
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Figure 1a. Pathologically proved left ventricular false aneurysm in 76-year-old man after myocardial infarction. (a) Short-axis oblique view obtained with a fast steady-state cine MR imaging sequence (3.8/1.4) shows interruption of the basal-inferior wall and formation of a bulging cavity (*) in which dyskinetic wall movement is visible. (b) Long-axis oblique view, obtained with inversion-recovery-prepared breath-hold cine gradient-echo sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm) 15 minutes after injection of gadodiamide, shows delayed enhancement of the pericardium that forms the wall (large arrows) of the false aneurysm, as well as hypointense thrombus (small arrows) that abuts the false aneurysm wall. Note that the maximal width of the orifice (4.5 cm) is shorter than the maximal parallel internal diameter (6.1 cm), a typical feature of false aneurysm.(c) Long-axis oblique view parallel to b shows additional delayed enhancement (arrows) in remote areas of pericardium that cover the anterior left ventricular wall, which has normal thickness.
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Figure 1b. Pathologically proved left ventricular false aneurysm in 76-year-old man after myocardial infarction. (a) Short-axis oblique view obtained with a fast steady-state cine MR imaging sequence (3.8/1.4) shows interruption of the basal-inferior wall and formation of a bulging cavity (*) in which dyskinetic wall movement is visible. (b) Long-axis oblique view, obtained with inversion-recovery-prepared breath-hold cine gradient-echo sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm) 15 minutes after injection of gadodiamide, shows delayed enhancement of the pericardium that forms the wall (large arrows) of the false aneurysm, as well as hypointense thrombus (small arrows) that abuts the false aneurysm wall. Note that the maximal width of the orifice (4.5 cm) is shorter than the maximal parallel internal diameter (6.1 cm), a typical feature of false aneurysm.(c) Long-axis oblique view parallel to b shows additional delayed enhancement (arrows) in remote areas of pericardium that cover the anterior left ventricular wall, which has normal thickness.
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Figure 1c. Pathologically proved left ventricular false aneurysm in 76-year-old man after myocardial infarction. (a) Short-axis oblique view obtained with a fast steady-state cine MR imaging sequence (3.8/1.4) shows interruption of the basal-inferior wall and formation of a bulging cavity (*) in which dyskinetic wall movement is visible. (b) Long-axis oblique view, obtained with inversion-recovery-prepared breath-hold cine gradient-echo sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm) 15 minutes after injection of gadodiamide, shows delayed enhancement of the pericardium that forms the wall (large arrows) of the false aneurysm, as well as hypointense thrombus (small arrows) that abuts the false aneurysm wall. Note that the maximal width of the orifice (4.5 cm) is shorter than the maximal parallel internal diameter (6.1 cm), a typical feature of false aneurysm.(c) Long-axis oblique view parallel to b shows additional delayed enhancement (arrows) in remote areas of pericardium that cover the anterior left ventricular wall, which has normal thickness.
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Figure 2a. Pathologically proved left ventricular false aneurysm in 71-year-old man after myocardial infarction. (a) Short-axis oblique view obtained with a fast steady-state cine MR imaging sequence (3.6/1.5) shows interruption of the basal-inferior wall and formation of a bulging cavity with dyskinetic wall motion on cine images. The maximal width of the orifice (4.3 cm) is shorter than the maximal parallel internal diameter (6.9 cm). (b) Long-axis oblique view obtained with an inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm), 15 minutes after contrast material injection, shows delayed enhancement (arrows) of wall of false aneurysm and small hypointense mural thrombus (arrowhead). (c) Short-axis oblique view obtained at delayed contrast-enhanced imaging 20 minutes after contrast material injection shows hyperintense line of pericardial enhancement that extends continuously from false aneurysm wall to remote areas (arrows) of pericardium in anterior left ventricular wall.
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Figure 2b. Pathologically proved left ventricular false aneurysm in 71-year-old man after myocardial infarction. (a) Short-axis oblique view obtained with a fast steady-state cine MR imaging sequence (3.6/1.5) shows interruption of the basal-inferior wall and formation of a bulging cavity with dyskinetic wall motion on cine images. The maximal width of the orifice (4.3 cm) is shorter than the maximal parallel internal diameter (6.9 cm). (b) Long-axis oblique view obtained with an inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm), 15 minutes after contrast material injection, shows delayed enhancement (arrows) of wall of false aneurysm and small hypointense mural thrombus (arrowhead). (c) Short-axis oblique view obtained at delayed contrast-enhanced imaging 20 minutes after contrast material injection shows hyperintense line of pericardial enhancement that extends continuously from false aneurysm wall to remote areas (arrows) of pericardium in anterior left ventricular wall.
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Figure 2c. Pathologically proved left ventricular false aneurysm in 71-year-old man after myocardial infarction. (a) Short-axis oblique view obtained with a fast steady-state cine MR imaging sequence (3.6/1.5) shows interruption of the basal-inferior wall and formation of a bulging cavity with dyskinetic wall motion on cine images. The maximal width of the orifice (4.3 cm) is shorter than the maximal parallel internal diameter (6.9 cm). (b) Long-axis oblique view obtained with an inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm), 15 minutes after contrast material injection, shows delayed enhancement (arrows) of wall of false aneurysm and small hypointense mural thrombus (arrowhead). (c) Short-axis oblique view obtained at delayed contrast-enhanced imaging 20 minutes after contrast material injection shows hyperintense line of pericardial enhancement that extends continuously from false aneurysm wall to remote areas (arrows) of pericardium in anterior left ventricular wall.
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Figure 3a. Pathologically proved large apicoanterior false aneurysm in 75-year-old man after myocardial infarction. (a) Long-axis oblique view obtained with inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (5.4/1.4/200; flip angle, 25°; section thickness, 10 mm), 15 minutes after contrast material injection, shows enhanced wall (large arrows) of false aneurysm with continuous line of basal-inferior pericardial enhancement (arrowheads) and internal thrombus (small arrows). The maximal width of the orifice (6.5 cm) is shorter than the maximal parallel internal diameter (8.5 cm).(b) Short-axis oblique view obtained with the same sequence as a, 20 minutes after contrast material injection, shows delayed enhancement of pericardium (arrowheads) in a continuous line with enhanced wall of left ventricular aneurysm (large arrows), as well as mural thrombi along the wall of the false aneurysm (small arrows).
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Figure 3b. Pathologically proved large apicoanterior false aneurysm in 75-year-old man after myocardial infarction. (a) Long-axis oblique view obtained with inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (5.4/1.4/200; flip angle, 25°; section thickness, 10 mm), 15 minutes after contrast material injection, shows enhanced wall (large arrows) of false aneurysm with continuous line of basal-inferior pericardial enhancement (arrowheads) and internal thrombus (small arrows). The maximal width of the orifice (6.5 cm) is shorter than the maximal parallel internal diameter (8.5 cm).(b) Short-axis oblique view obtained with the same sequence as a, 20 minutes after contrast material injection, shows delayed enhancement of pericardium (arrowheads) in a continuous line with enhanced wall of left ventricular aneurysm (large arrows), as well as mural thrombi along the wall of the false aneurysm (small arrows).
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Figure 4. Pathologically proved apicoanterior true aneurysm in 58-year-old man after myocardial infarction. Long-axis oblique view obtained with inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm), 15 minutes after contrast material injection, shows contrast enhancement (large arrows) along the left ventricular wall, which correlates with findings of transmural myocardial infarction with marked endocardial fibrosis at pathologic analysis; areas of nonenhancing hypointense parietal pericardium adjacent to the aneurysm (small arrows) and in remote areas along the inferior wall (arrowheads); and a moderate amount of pericardial effusion (*). The maximal width of the orifice (6.9 cm) is slightly greater than the maximal parallel internal diameter (6.7 cm) of the true aneurysm.
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The scores for delayed enhancement of the pericardium in both groups of patients are shown in Table 2. MR images in all four patients with a false aneurysm demonstrated marked delayed enhancement (score of 2) (Figs 1–3), while images in only one of 18 patients with a true aneurysm showed a similar degree of delayed enhancement and images in two of the 18 patients showed a mild degree of enhancement (score of 1). In the remaining patients with left ventricular true aneurysm, the nonenhancing pericardium, which appeared as a distinct hypointense thin line surrounding the heart, could be distinguished from the enhancing infarcted myocardium (Figs 4, 5). With a score greater than 0 considered to indicate a positive result, the sensitivity of pericardial delayed enhancement for the detection of a false left ventricular aneurysm was 100% (four of four patients), specificity was 83.3% (15 of 18 patients), accuracy was 86.4% (19 of 22 patients), positive predictive value was 57.1% (four of seven patients), and negative predictive value was 100% (15 of 15 patients). The pericardial enhancement was not confined to the pericardium bordering the false cavity but extended continuously along areas of pericardium surrounding normal myocardium (Figs 2c, 3, 4).
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TABLE 2. Results of Image Scoring for Delayed Enhancement of Pericardium in Patients with True and False Left Ventricular Aneurysms
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Figure 5a. Pathologically proved apicoanterior true aneurysm in 59-year-old man after myocardial infarction. (a) Long-axis and(b) short-axis oblique views obtained with inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm), 15 and 20 minutes, respectively, after contrast material injection, show enhancement along the infarcted anterior and apical left ventricular wall (arrows) but no substantial enhancement of pericardium (arrowheads).
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Figure 5b. Pathologically proved apicoanterior true aneurysm in 59-year-old man after myocardial infarction. (a) Long-axis and(b) short-axis oblique views obtained with inversion-recovery-prepared breath-hold gradient-echo cine MR imaging sequence (7.1/3.1/200; flip angle, 25°; section thickness, 10 mm), 15 and 20 minutes, respectively, after contrast material injection, show enhancement along the infarcted anterior and apical left ventricular wall (arrows) but no substantial enhancement of pericardium (arrowheads).
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Patients with a false aneurysm had a significantly higher left ventricular end-diastolic volume than did those with a true aneurysm (P = .001) and had a nonsignificant tendency toward a smaller left ventricular ejection fraction (P = .15) (Table 1).
Pathologic analysis in all four patients with a false aneurysm revealed severe wall thinning with various degrees of neovascularization and with no evidence of residual muscle fibers or elastic tissue.
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DISCUSSION
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A cardiac false aneurysm is defined as a rupture of the myocardium that is contained by pericardial adhesions (12). It usually represents a rare complication of myocardial infarction, but it may also occur after cardiac surgery, chest trauma, and endocarditis. Pathologic examination shows fibrous tissue and lack of the myocardial elements that are usually seen in the wall of true aneurysms (13).
It is traditionally believed that a false aneurysm has a high risk of rupture even several years after its formation (14). Although recent reports suggest a more favorable outcome (15), surgical repair is still regarded as the treatment of choice. In contrast, true aneurysm, which occurs in 5%–10% of patients with acute myocardial infarction, does not tend to rupture at the chronic stage and therefore, in the absence of other indications for surgery (eg, refractory angina pectoris, congestive heart failure, systemic embolization, or refractory arrhythmia), is treated medically. Hence, a correct diagnosis and differentiation between the two entities has important clinical implications.
Although typical features suggestive of false aneurysm have been described by using two-dimensional echocardiography (9–11), angiography (16), computed tomography, and MR imaging with previous generations of MR units (17), it may be difficult to distinguish between the two entities in some cases. Recent cardiac MR imaging studies with delayed contrast enhancement have shown promising results for the detection and delineation of myocardial infarction (4–6). The potential role of this technique in differentiation between false and true aneurysms is still unclear, and, to the best of our knowledge, was discussed in only a single case report (7). The results of the present study suggest that marked delayed enhancement of the pericardium might be a helpful additional imaging feature for differentiation between true and false left ventricular aneurysms in patients after myocardial infarction. Intense delayed enhancement (score of 2) of the pericardium was noted in all four cases of false aneurysm. In contrast, only one of 18 cases of true aneurysm showed a similar intense enhancement, while faint delayed pericardial enhancement (score of 1) was observed in two additional cases. The resulting sensitivity of this feature was 100%, specificity was 83.3%, and accuracy was 86.4%. In all cases, the enhancement was not limited to an area adjacent to the myocardial infarction but rather extended to normal myocardium, including remote areas such as the pericardial recesses.
Microscopic examinations of the resected pericardium from all four patients showed an organizing pericardium with evidence of neovascularization. Delayed contrast enhancement due to an unknown mechanism was previously shown to occur in nonperfused myocardial scar tissue (4). We hypothesize that chemical irritation of the pericardium by blood released in the acute phase of myocardial rupture might have caused a diffuse pericardial inflammatory reaction and, subsequently, some degree of fibrotic reaction by means of a mechanism similar to that in myocardial scarring, with resultant delayed enhancement of the pericardium.
Cardiac MR imaging is an established technique and is probably the most accurate technique for evaluation of left ventricular function and volume (18). Our study results show for the first time, to our knowledge, a significantly higher left ventricular end-diastolic volume in patients with a false aneurysm than in those with a true aneurysm. Our results suggest that the left ventricular end-diastolic volume might be higher in patients with a false aneurysm than in those with a true aneurysm. Since there is an overlap of values between the two groups, however, a false aneurysm cannot be definitely excluded by using this criterion only.
Two of the four false aneurysms in our series involved the left ventricular inferior wall, while none of the true aneurysms were located in that area. This result concords with that in the study by Yeo et al (11), who showed an inferolateral location in 18 (82%) of 22 consecutive patients with postinfarction false aneurysm diagnosed ante mortem, in most cases with two-dimensional echocardiography, during a 16-year period. Twenty years earlier, Higgins et al (16) found at cardiac catheterization that eight (72%) of 11 postinfarction false aneurysms involved a portion of the inferolateral or inferior wall versus 4% of 50 consecutive true aneurysms. Nevertheless, a substantial number of false aneurysms are located in other areas of the left ventricular wall, limiting the value of this feature for differentiation between true and false aneurysms.
Researchers in several previous studies (9–11,16,17) showed that false aneurysms have a typical narrow ostium connecting the aneurysmal sac to the ventricle. In most cases, the internal neck width (ie, the maximal internal width of the orifice) is less than the maximal parallel internal diameter, with a resultant ratio of less than 1.00 between these two measurements, while in cases of true aneurysm the ratio is usually greater than 1.00. Our results correlate with the results of these previous studies: We obtained a median ratio of 0.73 for patients with a false aneurysm, significantly lower than that in patients with a true aneurysm.
Left ventricular thrombus formation is a frequent complication of myocardial infarction; it occurs in 11.5% of all anterior wall infarctions (19), and it is more common in cases of left ventricular aneurysm formation (9,10). Although an associated mural thrombus was noted in all four patients with a false aneurysm, compared with 39% of patients with a true aneurysm, the difference did not reach statistical significance (P = .09), because of the limited number of patients with a false aneurysm. The distinction between a thin mural thrombus and the myocardium might be difficult with both transthoracic and transesophageal echocardiography (20). A recent report suggested that cardiac MR imaging with delayed contrast enhancement might be superior to transesophageal echocardiography for the detection of left ventricular thrombi (21). This represents an additional clinically important advantage of cardiac MR imaging with delayed contrast enhancement for the evaluation of patients with suspected left ventricular aneurysm, and it further justifies the use of this technique in the routine evaluation of these patients.
A main limitation of our study was the small number of patients with a false aneurysm. However, the main observation first described, to our knowledge, in this article (ie, marked delayed enhancement of the pericardium) appeared in all patients with a false aneurysm and in only a minority of those with a true aneurysm. Future studies of cardiac MR imaging with delayed contrast enhancement in a larger patient series are required to further assess the value of this feature. Such studies should also include left ventricular volumetric and functional assessments based on cine MR imaging, to further define the role of left ventricular end-diastolic volume in differentiating between true and false aneurysms.
In conclusion, our findings suggest that cardiac MR imaging may play an important role in differentiating between true and false left ventricular aneurysms in patients after myocardial infarction. Further studies with delayed contrast enhancement are required to further assess the value of this feature in particular and the overall role of cardiac MR imaging in the diagnosis of false left ventricular aneurysm.
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FOOTNOTES
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Authors stated no financial relationship to disclose.
Author contributions: Guarantors of integrity of entire study, E.K., N.M.; study concepts, E.K.; study design, E.K., N.M.; literature research, E.K., Y.P.; clinical studies, N.M., Y.P., E.K., N.S.P.; data acquisition, N.M., Y.P., L.M., N.S.P., J.B.; data analysis/interpretation, N.M., C.G., Y.P., L.M., J.B.; statistical analysis, C.G.; manuscript preparation, E.K., N.S.P.; manuscript definition of intellectual content, E.K., N.M.; manuscript editing, N.M., Y.P.; manuscript revision/review, N.M., L.M., J.B.; manuscript final version approval, all authors
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ABSTRACT
INTRODUCTION
