True versus false left ventricular aneurysm: differentiation with MR imaging--initial experience.

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/m(2); 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.