Arrhythmogenic right ventricular dysplasia: cardiomyopathy current opinions on diagnostic and therapeutic aspects

Utility of exercise testing in children and teenagers with arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is increasingly recognized as an important cause of exertional sudden death in otherwise healthy young individuals and athletes. Graded exercise testing is routinely included in the evaluation of patients with suspected ARVC, but its diagnostic utility has not been systematically assessed. Using a single-center retrospective design, the rhythm response to graded exercise testing was examined in 33 tests performed in 16 young (aged <18 years) patients with established diagnosis of ARVC. Ventricular premature complexes (VPCs) were classified as absent (graded 0), as being isolated or in couplets (graded 1), or as comprising nonsustained ventricular tachycardia (graded 2) during pretest rest, at peak exercise, and during postexercise recovery. VPCs were absent at rest in 21 of 33 studies, subsequently appearing at peak exercise in 4 studies and during recovery in 2 studies. Isolated VPCs and couplets were present at rest in 9 of 33 studies, with subsequent exercise provoking higher grade ectopic activity in 2 instances at peak exercise and in 1 case during recovery, while VPCs decreased or remained unchanged in all other cases. In all 3 instances in which ventricular tachycardia was observed during pretest rest, there was either suppression (3 at peak exercise, 2 during recovery) or no change (1 case during recovery) in VPC grade. In conclusion, the exercise response of ventricular ectopic activity is highly variable in young patients with ARVC. The diagnostic utility of graded exercise testing is thus questionable in young patients with suspected ARVC, and the absence or suppression of VPCs during exercise should not be considered reassuring in terms of its diagnostic exclusion.

Rapid evolution of right ventricular cardiomyopathy after surgical closure of a secundum atrial septal defect

Rapidly developing diffuse right ventricular cardiomyopathy presenting with right heart failure in a 9-year-old boy within 2 months after surgical closure of a secundum atrial septal defect is reported. The child was treated by palliative surgery with partial exclusion of the right ventricle by bidirectional Glenn shunt.

Postoperative death in a patient with unrecognized arrhythmogenic right ventricular dysplasia syndrome

Arrhythmogenic right ventricular dysplasia is an inherited disease causing fatty replacement of heart tissue. This disease often presents as T-wave inversion in the anterior leads of the electrocardiogram (ECG) with life-threatening ventricular arrhythmias. In older patients, progressive right and left ventricular failure can develop. This is a case report of postoperative death occurring in a 59-yr-old woman with undiagnosed arrhythmogenic right ventricular dysplasia after hepatic cystectomy. The patient had T-wave inversion in the inferior ECG leads and no history of arrhythmias. During general anesthesia, cardiovascular collapse occurred in the absence of arrhythmias that was unresponsive to resuscitation.

Stretch-induced regional mechanoelectric dispersion and arrhythmia in the right ventricle of anesthetized lambs

Regional mechanical and electrophysiological changes accompany most ventricular arrhythmias and, it has been suggested, by mechanoelectric feedback. We hypothesized that an intervention producing regional mechanical dispersion was associated with regional, proarrhythmic electrical dispersion and studied the regional mechanoelectric feedback in the right ventricle (RV) of anesthetized lambs. Ten lambs were deeply anesthetized, and their hearts were exposed. Three tripodal devices, each incorporating three monophasic action potential electrodes and an integrated strain-gauge system, were placed on the RV apex outflow and inflow regions. Measurements were made before, during, and after 10-s pulmonary arterial occlusion. Pulmonary arterial occlusion increased RV pressure and overall regional segment length. Length excursion became out of phase with RV pressure beats immediately after occlusion, and the strain patterns were different in the three regions at the peak of occlusion. The occlusion resulted in different alterations in regional monophasic action potential morphology, including reduction in monophasic action potential amplitude and duration by different amounts and early afterdepolarizations that were unevenly distributed in the monophasic action potential recordings. This was associated with dispersion of repolarization and recovery time. The combination of electromechanical events precipitated a variety of arrhythmias. Acute RV distension is proarrhythmic, possibly through a causal relationship among mechanically induced afterdepolarizations, dispersion (heterogeneity) of mechanical strain, and dispersion of electrical recovery. The relationship among the different wall motions, the dispersion of repolarization, and arrhythmia underscored mechanoelectric feedback as an important part of arrhythmogenesis in pulmonary embolism and commotio cordis.

Magnetic resonance imaging of primary cardiomyopathies

Cardiomyopathies are diseases of the myocardium of unknown etiology associated with cardiac dysfunction. On the grounds of their morphology and pathophysiology, primary or idiopathic cardiomyopathies may be classified into a number of disorders; namely, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathy. The term "secondary cardiomyopathies" is reserved to specific heart muscle diseases clinically very similar to primary cardiomyopathies. Cardiac magnetic resonance imaging has long been used to study cardiac morphology and, more recently, to assess blood flow, perfusion, and contractile function. The emerging role of magnetic resonance imaging for the understanding and treatment of primary cardiomyopathies cannot be underestimated. From a clinical point of view, an examination based on a single, efficient, and noninvasive MR study focusing on the clinically relevant features of cardiomyopathies is an objective and reproducible means for diagnosing and monitoring hypertrophic, arrhythmogenic, dilated, and restrictive cardiomyopathies.

A recessive mutation in desmoplakin causes arrhythmogenic right ventricular dysplasia, skin disorder, and woolly hair

OBJECTIVES

The goal of this study was to analyze the genetic disorder of a family with cardiomyopathy, skin disorder, and woolly hair.

BACKGROUND

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disorder causing arrhythmia and sudden cardiac death. We report a patient with familial autosomal recessive ARVD, woolly hair, and a pemphigous-like skin disorder with a new mutation in the desmoplakin gene.

METHODS

Genomic deoxyribonucleic acid was extracted from the patient's blood and 12 first- and second-degree family members, and was amplified by polymerase chain reaction. Linkage analysis with polymorphic microsatellites was performed for 11 genes that code for structural desmosomal proteins. The genetic locus of the disease in this family was mapped to the chromosomal region 6p24 that contains the desmoplakin gene. Exons of the desmoplakin gene were analyzed by single-strand conformational polymorphism and direct sequencing. Confirmation of the mutation was carried out by restriction enzyme analysis.

RESULTS

We identified in the patient a homozygous missense mutation in exon 24 of the desmoplakin gene, leading to a Gly2375Arg substitution in the C-terminal of the protein where the binding site to intermediate filaments is located. Eight of 12 family members without hair or skin abnormalities were heterozygous for this mutation. The remaining 4, as well as 90 unrelated healthy control individuals of the same ethnic origin, were homozygous for the normal allele.

CONCLUSIONS

We have described a new mutation in the desmoplakin gene that causes familial ARVD. These findings suggest that desmosomal proteins play an important role in the integrity and function of the myocardium. Dysfunction of these proteins can lead to the development of cardiomyopathies and arrhythmias.

Clinical profile of arrhythmogenic right ventricular cardiomyopathy in Chinese patients

OBJECTIVE

To study the clinical profile of Chinese patients with arrhythmogenic right ventricular cardiomyopathy (ARVC).

PATIENTS

Chinese patients who fulfilled the diagnostic criteria of ARVC proposed by the Task Force of the European Society of Cardiology and of the scientific council on cardiomyopathy of the International Society and Federation of Cardiology were recruited for analysis.

METHODS

Clinical data of patients with ARVC including age, sex, family history, presenting symptoms, electrocardiograph (ECG), echocardiography, cardiac catheterization, magnetic resonance imaging (MRI), electrophysiology study (EPS) and therapeutic intervention were analyzed.

RESULTS

Eleven patients (seven males) were diagnosed with ARVC. Mean age at clinical presentation was 42.6+/-14.8 years. Two patients (18.1%) had positive family history of ARVC or premature sudden cardiac death. The commonest presenting symptoms were palpitation (73%) and dizziness (46%). Spontaneous ventricular tachycardia (VT) was the presenting arrhythmia in 54% and 1 (9%) with ventricular fibrillation and cardiac arrest. Seven patients (64%) had the ECG abnormality as defined by the Task Force. Echocardiography showed right ventricular (RV) dilatation in five patients (46%) and all patients had normal left ventricular function. Nine patients (90%) had RV wall thinning or fibrofatty replacement on MRI examination. Inducible monomorphic VT was detected in four out of nine patients at EPS. All eight patients had normal coronary arteries and left ventriculogram but RV dilatation and global hypokinesia was seen in three patients. Implantable cardioverter defibrillators were implanted in five patients and two of them had shocks delivered during the follow-up period.

CONCLUSION

In this study, familial incidence of premature sudden death in patients with ARVC appears to be low and left ventricular involvement in affected individuals is uncommon. MRI is still the best investigation for ARVC.

Etiology and management of sustained ventricular tachycardia

Ventricular tachyarrhythmias secondary to a variety of underlying cardiovascular problems pose a therapeutic challenge to the clinician. The initial presentation may be as sudden cardiac death, which underlies its public health problem. The underlying conditions predisposing to this arrhythmia include ischemic heart disease, dilated cardiomyopathy, hypertrophic cardiomyopathy, arrhythmiogenic right ventricle dysplasia and certain postoperative states including corrective surgery for tetralogy of Fallot and valve replacement. Other causes include prolonged QT syndrome, idiopathic right and left ventricle tachycardia and bundle branch re-entry tachycardia. Ischaemic heart disease is the most common cause of ventricular tachycardia and therapy has evolved considerably over the past two decades. The development of and refinements in the implantable cardioverter-defibrillator (ICD) have introduced a new dimension in therapeutic options and markedly improved survival in these patients. Insights in the dichotomy between arrhythmia suppression and total mortality have reoriented drug therapy with a decrease in the use of sodium channel blockers. beta-blockers have emerged as antiarrhythmic drugs in their own right and their synergistic effects with amiodarone have strengthened the antiarrhythmic drug arm. The role of these drugs in patients with hemodynamically stable ventricular tachycardia, especially in relatively preserved ventricles needs to be explored. Catheter ablation techniques have provided curative therapy in patients with idiopathic and bundle branch reentry tachycardia. Further advances in radiofrequency ablation, including use of newer mapping techniques, promise a greater role for ablation of ischemic ventricular tachycardia in the future. A hybrid approach consisting of drugs, catheter ablation and/ or ICD may provide effective therapeutic approach in some situations. Further innovations and technologic developments promise a further reorientation in therapy towards identification and treatment of the underlying arrhythmogenic substrate.