Case of the month header
 August 2010

Dear SCCT Member:

As you know, the SCCT is the only professional medical membership organization dedicated to ensuring patient access to the appropriate use of cardiovascular CT. The SCCT Board of Directors thought that it would be beneficial to our members to create a Case of the Month series showcasing cardiac CTA in various clinical scenarios. Please provide feedback or forward any questions to info@scct.org.

Sincerely,
John R Lesser, MD, FSCCT
Suhny Abbara, MD, FSCCT
Jeff Carr, MD, FSCCT
Daniel Entrikin, MD, FSCCT

Mass-querading Left Ventricular Infarct

Vikram Venkatesh MD, James K Woo MD, John Lichtenberger MD, Hector M Medina MD, MPH, Suhny Abbara, MD
Massachusetts General Hospital, Harvard Medical School, Boston, MA
History

A 53-year-old male patient with a history of congestive heart failure, hypertension, type 2 diabetes mellitus and alcohol abuse presented to the emergency department with intermittent shortness-of-breath at rest, increased exertional dyspnea and bilateral leg edema for the past four days.  A transthoracic cardiac ultrasound was ordered to evaluate the lower extremity edema and known depressed ejection fraction.
Findings

2D echocardiography showed mild to moderate systolic dysfunction and a mass located in midventricular inferior wall (Fig 1). Differential diagnoses included metastatic lesion, sarcoma, lipoma and angiosarcoma.

A cardiac MRI was ordered for further characterization and demonstrated transmural delayed hyperenhancement, myocardial thinning and hypokinesis in a corresponding area (Fig  2).
There were additional foci of patchy late gadolinium enhancement remote from this site (not shown).

CT demonstrated thinning and low attenuation in the same location, consistent with fatty metaplasia due to remote myocardial infarction. The RCA was mostly non-dominant except for an acute marginal branch that crosses the middle cardiac vein and supplied a small focus of the midventricular inferior wall segment. This unusual vessel, which is known as a "posterior right diagonal" branch, demonstrated a distal occlusive lesion. [1] (Fig. 3a,b,c)



Figure 3
August 2010 Figure 3
   
Discussion

The putative mechanism for low attenuation on cardiac CT related to infarction includes non-enhancement and edema in the acute phase, and subsequently fatty and fibrous infiltration of necrotic myocardium. [2] In this case CT definitively excluded the presence of a mass, and instead demonstrated that the echocardiographic findings were related to fatty metaplasia attributable to a remote infarct in an unusual distribution. Studies suggest that cardiac CT can be used for infarct characterization with accuracy similar to that achieved by MR.[3,4] The presence of a right posterior diagonal artery in an otherwise left dominant system was observed in only one out of 607 consecutive patients who underwent coronary angiography.[1]  In this case, MR and CT were of paramount importance in ruling out cardiac mass, and explaining the artifact seen on echocardiography. CT additionally demonstrated the occluded unusual vessel responsible for the myocardial infarction.
References
 
1. Margaris NG, Kostopoulos KG, Nerantzis CE, Filippatos GS, Kardaras FG, Salahas AI, Antonellis JP, Ifandis GP, Kranidis AI, Tavernarakis AG. Posterior right diagonal artery. An angiographic study. Angiology. 1997 Aug;48(8):673-7.

2. Nikolaou K, Knez A, Sagmeister S, Wintersperger BJ, Boekstegers P, Steinbeck G, Reiser MF, Becker CR. Assessment of myocardial infarctions using multidetector-row computed tomography. J Comput Assist Tomogr. 2004 Mar-Apr;28(2):286-92.

3. Gerber BL, Belge B, Legros GJ, Lim P, Poncelet A, Pasquet A, Gisellu G, Coche E, Vanoverschelde JL. Characterization of acute and chronic myocardial infarcts by multidetector computed tomography: comparison with contrast-enhanced magnetic resonance. Circulation. 2006 Feb 14;113(6):823-33

4. Choe YH, Choo KS, Jeon ES, Gwon HC, Choi JH, Park JE. Comparison of MDCT and MRI in the detection and sizing of acute and chronic myocardial infarcts. Eur J Radiol. 2008 May;66(2):292-9.




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