1351063 - Intramyocardial Septal Dissecting Hematoma following Inferior Myocardial Infarction

Description of Clinical Presentation: A previously healthy 36-year-old man presented to the emergency room with four days of chest pain. ECG showed ST elevations in the inferior and anteroseptal leads. Emergent cardiac catheterization showed complete occlusion of the proximal right coronary artery (RCA) with a high thrombus burden. The left anterior descending artery (LAD) was patent. TIMI 3 flow was established following mechanical thrombectomy and drug-eluting stent placement in the RCA. A transthoracic echocardiogram showed a moderately thick dyskinetic septum with a septal mass protruding into the right ventricular outflow tract. Right ventricular systolic function was severely reduced. The patient required temporary ionotropic support for cardiogenic shock from right ventricular dysfunction but was eventually started on goal-directed medical therapy.

Diagnostic Techniques and Their Most Important Findings: Echocardiography: A repeat echocardiogram again showed a dyskinetic septum with 3 cm x 1.5 cm echogenic spherical fixed mass along the right ventricular aspect of the septum which had increased in size in comparison to the prior echocardiogram. Use of contrast agent during the echocardiography showed a lack of contrast uptake in the septum and the mass in RV.
Cardiac MRI: Patient underwent Cardiac MRI(CMR) 1.5T (Optima MR450w, GE Medical Systems) scan to further characterization of the RV mass. Sequences included multiplanar b-SSFP CINE stacks, 3-short axis T2(T2 weighted DIR FSE in short acxis) and 2D inversion recovery FGRE late gadolinium enhacement (LGE) images. Septum appeared dyskinetic on MRI. T2W images showed increased septal T2 signal intensity, consistent with edema. LGE images in short axis projection displayed transmural scar in septum and apical inferior walls. However, LGE images showed hypointense zone within the Intramyocardial mass consistent with the diagnosis of intramyocardial hematoma in the given clinical context.

Learning Points from this Case: Anteroseptal ST elevations on the presenting ECG, dyskinetic septum and septal mass could not be explained by occluded RCA and a patent LAD. Possibility of thrombus on the right ventricular aspect of the interventricular septum was entertained. Contrast echocardiography confirmed avascular nature of the mass, which further raised the possibility of a thrombus. MRI was used to characterize the mass which showed intramyocardial hematoma amidst a septal transmural scar. Mass effect in the septal dissection plane was thought to contribute to anteroseptal infarct, dyskinesis, and anterseptal ST elevations despite having a patent LAD. This further emphasizes on the importance of adopting CMR for evaluation of cardiac masses. Of note, the possibility of intramyocardial hematoma should be entertained in patients with a cardiac mass seen in the context of acute myocardial infarction. Cardiac MRI is a helpful tool for characterization of intracardial masses.