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E1838. When Right is Wrong: A Cardiac MR Imaging Review of Isolated Right Ventricular Enlargement
Authors
  1. Elizabeth Proffitt; Virginia Commonwealth University
  2. John Grizzard; Virginia Commonwealth University
Background
Isolated right ventricular (RV) enlargement is when the right ventricle demonstrates signs of failure such as enlargement and reduced systolic function with clinical evidence of heart failure in the setting of structurally and functionally normal left ventricle (LV). This can result from a variety of etiologies ranging from congenital abnormalities to acquired cardiomyopathies and valvular disease processes and is a complex diagnosis. These patients will often present in atypical ways which delays diagnosis and optimal treatment; however, due to our limited understanding of some of these processes, even with early diagnosis, treatment options can be limited. Also, patients with RV dysfunction have worse clinical outcomes independent of the underlying disease process. The focus will not be to discuss RV failure in conjunction with LV failure or RV failure as a result of pulmonary hypertension, but rather RV failure in isolation. Both are large and extensive topics for which ample literature is available. Our focus will be on isolated RV enlargement resulting from primarily right heart pathologies, a topic which receives far less attention. We will address some of these disease processes in detail with a focus on their appearance on cardiac MR. These diagnoses fall into four main categories - cardiomyopathy, shunts, valve disorders, and congenital abnormalities.

Educational Goals / Teaching Points
- Outline a systematic algorithm for all radiologists on how isolated RV enlargement can be successfully approached when seen on imaging with a primary focus on MR imaging findings. - Review RV physiology and provide a detailed review of the various individual diagnoses that can result in isolated RV enlargement.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
We propose a systematic algorithm for how to approach isolated RV enlargement when seen on imaging. Cardiac MRI is the gold standard in imaging to fully evaluate the structure, composition, and function of the RV. Determining RV size can be difficult due to its complex shape, but made easier by the multiplanar imaging available with MR. If RV dysfunction is present, attention should be paid to the post contrast imaging which will identify areas of scarring and inflammation. If RV function is determined to be normal, the two categories to next evaluate are that of valve disorders and shunts. Phase contrast imaging on cardiac MR is a very helpful tool for evaluating these potential etiologies of isolated RV failure. By combining the imaging findings with the patient’s history and detailed diagnostic information provided in this review, radiologists can successfully arrive at an educated diagnosis for isolated RV enlargement.

Conclusion
Isolated RV enlargement can be seen in a number of important and varied pathologic conditions. The clinical presentation can be subtle and mimic that of more common diagnoses and the imaging can be difficult to interpret without an orderly approach. In this review, we have suggested a systematic approach to a differential diagnosis and reviewed various diagnosis leading to isolated right ventricular enlargement in depth with a focus on cardiac MR imaging.