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Arrhythmogenic right ventricular dysplasia is a rare disorder that is familial in 30% to 50% of cases. It is characterized by structural and functional abnormalities of the right ventricle and a propensity for ventricular arrhythmias and sudden death.
We report the case of a 59-year-old woman who had idiopathic, severe, right-sided heart failure and nonsustained ventricular tachycardia. She was diagnosed with arrhythmogenic right ventricular dysplasia by means of cardiac magnetic resonance imaging. We discuss the clinical features, diagnostic criteria, and role of cardiac magnetic resonance imaging in the diagnosis of arrhythmogenic right ventricular dysplasia.
Arrhythmogenic right ventricular dysplasia (ARVD) is a rare disorder characterized by structural and functional abnormalities of the right ventricle and a propensity for ventricular arrhythmias and sudden death.1–5 A family history of ARVD is present in 30% to 50% of cases.1,2 The most common pattern of inheritance is autosomal dominant, although an autosomal recessive pattern has been reported.3 Alternative causes have been proposed, including apoptosis, inflammation, infection, and degeneration,6 but substantive scientific evidence of their role in ARVD is sparse. Definitive diagnosis of ARVD is challenging, because the symptoms, physical findings, and electrocardiographic (ECG) results are often variable and inconclusive. We describe a patient with idiopathic, severe, right-sided heart failure and nonsustained ventricular tachycardia in whom ARVD was diagnosed by means of cardiac magnetic resonance imaging (MRI).
A 59-year-old woman presented at our cardiology clinic for evaluation of dyspnea and episodic hot flashes. On auscultation, her intrinsic cardiac rhythm was irregular. An ECG revealed frequent, multifocal, premature ventricular beats. A rhythm strip revealed nonsustained ventricular tachycardia, likely of right ventricular origin. The patient had a documented history of hypertension and idiopathic, severe, right-sided heart failure. Findings of a recent coronary angiogram were normal. Cardiac MRI was performed to evaluate the right ventricular cardiomyopathy of uncertain origin. This technique showed a greatly enlarged right ventricle and right atrium, with severe global dysfunction and multiple focal regions of dyskinesis (end-diastolic volume, 605 cc; end-systolic volume, 559 cc; stroke volume, 46 cc; and ejection fraction, 0.08). No left-to-right shunt was detected; specifically, there was no evidence of an atrial septal defect or of an anomalous pulmonary venous return to explain the right-sided chamber enlargement. Further, there were no findings to suggest pulmonary arterial hypertension or clinically significant pulmonary valve disease.
Black-blood and myocardial viability MRI with the delayed-enhancement technique revealed marked thinning and fibrous replacement of almost the entire right-ventricular free wall (Figs. 1–3). Cine images revealed extensive wall-motion abnormalities of the right ventricle. The left ventricle was normal in size with mildly reduced global systolic function. On the basis of these findings, ARVD was diagnosed. After further clinical confirmation of the diagnosis, an intracardiac defibrillator was implanted.
The typical clinical profile of a patient with ARVD is that of a middle-aged man who presents with palpitations, tachycardia, syncope, lightheadedness, or symptoms of right-sided heart failure. Generally, the physical findings are nonspecific. The ECG findings are highly variable; the most frequently encountered abnormalities are ventricular tachycardia with left bundle branch block and T-wave inversions in precordial leads V1 through V4. Rare ECG findings that are characteristic of ARVD patients include epsilon waves and prolonged QRS complexes (>110 ms) in the right precordial leads that are discordant with those in the left precordial leads.7
To facilitate the definitive diagnosis of ARVD, standardized diagnostic criteria have been proposed, based on the presence of major and minor structural, histologic, ECG, arrhythmic, and genetic factors.7 According to this classification system, a diagnosis of ARVD depends on the presence of 2 major criteria, or 1 major criterion plus 2 minor criteria, or 4 minor criteria from different groups.5 Microscopic evaluation of tissue from an endomyocardial biopsy is the gold standard. However, samples are routinely taken from the interventricular septum, despite the fact that the typical pathologic changes may be patchy and most frequently occur in the right ventricular free wall. (Biopsy of the right ventricular free wall is usually avoided because of the substantial risk of perforation.) Therefore, such biopsies lack sensitivity. In addition, echocardiography and angiography, although still used in many centers, are neither sensitive nor specific for tissue characterization.
In clinical practice, when one encounters a wide complex tachyarrhythmia with left bundle branch block morphology, a cardiac MRI examination should be considered in order to detect structural and wall-motion abnormalities of the right ventricle. Cardiac MRI is a powerful diagnostic tool because of its unique tissuecharacterizing capacity and potential to identify myocardial fibro-fatty infiltration and replacement. In addition, cardiac MRI can identify right atrial and ventricular dilation, and global and regional wall-motion abnormalities of the right ventricle. This imaging technique has the advantage of being a noninvasive diagnostic tool that avoids radiation and exposure to nephrotoxic contrast agents. Furthermore, cardiac MRI provides adjunctive information that may effectively exclude other causes of right-sided heart failure during a single imaging examination.
Cardiac computed tomography is an emerging technology in the diagnosis of ARVD and is particularly useful in identifying fatty deposits within the myocardium, although data concerning this method are preliminary.
Therapy for ARVD is currently palliative and is aimed at preventing the onset of life-threatening electrical instability with use of antiarrhythmic drugs (such as β-blockers and amiodarone). Intracardiac defibrillation is indicated for the secondary prevention of cardiac arrest in patients who have untreatable ventricular arrhythmias, particularly when previous episodes of ventricular fibrillation have occurred.8 Primary implantation of a defibrillator may be considered in patients who are at heightened risk. Cardiac transplantation is an option in the case of end-stage heart failure.
Address for reprints: Scott D. Flamm, MD, Cardiovascular Imaging Laboratory, Department of Radiology, Hb-6, Cleveland, OH 44195 E-mail: gro.fcc@smmalf