A 21-year-old man with no significant past medical history is admitted to the hospital for evaluation of recurrent syncope of unknown etiology.
The day of admission, he felt palpitations and dyspnea while arguing with his significant other. Subsequently, he noticed visual blurring and lowered himself to the floor. The patient was uncertain of the sequence of events that immediately followed. His significant other, who witnessed the event, called emergency medical services.
He reports a history of palpitations during periods of emotional stress and two prior episodes of syncope while playing basketball. After both episodes of syncope, his only recollection is regaining consciousness while people were attending to him. He has never had any cardiovascular testing prior. His family history is remarkable for a brother diagnosed with possible hypertrophic cardiomyopathy, who received an implantable cardioverter-defibrillator at the age of 30 years.
Laboratory values are unremarkable, although a troponin I measurement is 0.58 ng/mL (normal <0.11 ng/mL). The patient's electrocardiogram (ECG) is displayed in Figure 1.
Figure 1
Which of the following is most likely responsible for his recurrent syncopal episodes?
Show Answer
The correct answer is: B. Fibrofatty replacement of the right ventricular myocardium.
Answer B is correct, as T wave inversions in leads V1-V4 with the absence of a right bundle branch block meet major criteria for the diagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy. Desmosomal genetic mutations are often identified in affected patients. Figure 2 depicts fibrofatty infiltration of the right ventricle on pre- and post-contrast imaging. It is important to recognize that fibrofatty infiltration alone does not meet major or minor criteria for the diagnosis. Major CMR criteria for the diagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy according to the 2010 revised task force criteria include: Regional right ventricular akinesis, dyskinesis or dyssynchronous RV contraction AND RV end-diastolic volume index of ≥110 ml/m2 for males; ≥100 ml/m2 for females OR right ventricular ejection fraction of ≤40%. A definite diagnosis can be made with fulfillment of two major criteria; one major and two minor criteria; or four minor criteria from different categories (which include imaging, tissue characterization, repolarization abnormalities, depolarization/conduction abnormalities, arrhythmias, and family history). Of note, the echocardiogram obtained as part of the initial workup revealed limited visualization of the right ventricle with mildly reduced systolic function and normal 2D measurements.
Figure 2
Answer A is incorrect. Although the patient does have a family history of hypertrophic cardiomyopathy, the patient does not have left ventricular hypertrophy by ECG criteria or by MRI.
Answer C is incorrect. Neurocardiogenic syncope would not explain the patient's abnormal ECG findings or abnormal CMR findings.
Answer D is incorrect. The patient does not have left ventricular hypertrophy on ECG or CMR, which would be expected with severe symptomatic aortic stenosis. Furthermore, aortic stenosis is not associated with fibrofatty infiltration of the right ventricle.
Answer E is incorrect. The ECG does not depict evidence of a delta wave, which is often present with antegrade conduction down the bypass tract. This option also does not explain the abnormal CMR findings.
References
Marcus FI, McKenna WJ, Sherrill D, et al. Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: proposed modification of the task force criteria. Circulation 2010;121:1533.
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