Nonischemic sustained ventricular tachycardia: clinical outcome in 12 patients with arrhythmogenic right ventricular dysplasia

Diagnostic Efficacy of 123Iodo-Metaiodobenzylguanidine SPECT/CT in Cardiac vs. Neurological Diseases: A Comparative Study of Arrhythmogenic Right Ventricular Cardiomyopathy and α-Synucleinopathies

Background/Objectives: 123Iodo-metaiodobenzylguanidine single photon emission computed tomography/computed tomography (123I-MIBG SPECT/CT) is used to evaluate the cardiac sympathetic nervous system in cardiac diseases such as arrhythmogenic right ventricular cardiomyopathy (ARVC) and α-synucleinopathies such as Parkinson's diseases. A common feature of these diseases is denervation. We aimed to compare quantitative and semi-quantitative cardiac sympathetic innervation using 123I-MIBG imaging of ARVC and α-synucleinopathies. Methods: Cardiac innervation was assessed using 123I-MIBG SPECT/CT in 20 patients diagnosed with definite ARVC and 8 patients with clinically diagnosed α-synucleinopathies. Heart-to-mediastinum-ratio (H/M-ratio), as semi-quantitative, was evaluated. Additionally, standardized uptake value (SUV), as quantitative, was measured as SUVmedian, SUVmax, and SUVpeak in the left ventricle (LV), the right ventricle (RV), and in the global heart, based on a CT scan following quantitative image reconstruction. Results: The quantification of 123I-MIBG uptake in the LV, the RV, and the global heart was feasible in patients suffering from α-synucleinopathies. SUVmedian, and SUVpeak demonstrated a significant difference between ARVC and α-synucleinopathies across all regions, with the α-synucleinopathy group showing a lower uptake. In addition, the H/M ratio showed significantly lower uptake in patients with α-synucleinopathies than in patients with ARVC. Conclusions: Patients with α-synucleinopathies demonstrate significantly lower cardiac innervation in semi-quantitative and quantitative examinations than ARVC patients. The comparison of semi-quantitative and quantitative examinations suggests that quantitative examination offers an advantage. Quantitative analysis can be performed separately for the LV, RV, and global heart. However, analyzing the LV or RV does not provide additional benefit over analyzing the global heart in distinguishing between α-synucleinopathies and ARVC. Considering the different clinical manifestations of these two diseases, the absolute SUV values should not be generalized across different pathologies, and disease-specific ranges should be used instead.

Quantitative assessment of cardiac 123iodo-metaiodobenzylguanidine SPECT/CT in patients with arrhythmogenic right ventricular cardiomyopathy: Novel insight in disease monitoring

BACKGROUND

The heart-to-mediastinum ratio (H/M-Ratio) of 123iodo-metaiodobenzylguanidine (123I-MIBG) represents state-of-the-art assessment for sympathetic dysfunction in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). This study aims to evaluate quantitative reconstruction of 123I-MIBG uptake and to demonstrate its correlation with echocardiographic parameters.

METHODS

Cardiac innervation was assessed in 23 patients diagnosed with definite ARVC or borderline ARVC and 12 patients with other cardiac disease presenting arrhythmia, using quantitative 123I-MIBG Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) imaging. Tracer uptake was evaluated in the left (LV) and right ventricle (RV) based on a CT scan after quantitative image reconstruction. The relationship between tracer uptake and echocardiographic parameter data was examined.

RESULTS

Absolute quantification of 123I-MIBG uptake in the LV and RV is feasible and correlates accurately with the gold standard H/M Ratio. When comparing sensitivity and specificity, the area under the curve (AUC) favors standardized uptake value (SUV) of the RV over the right-ventricle-to-mediastinum-ratio (RV/M-Ratio) for diagnosing ARVC. A reduced RV-SUV in patients with definite ARVC is associated with reduced RV function. RV polar maps revealed globally reduced 123I-MIBG uptake without segment-specific reduction in the RV.

CONCLUSIONS

Quantitative 123I-MIBG SPECT in ARCV patients offers robust potential for clinical reporting and demonstrates a significant correlation with RV function. Segmental RV analysis needs to be evaluated in larger samples. In summary, cardiac 123I-MIBG imaging using SUV could facilitate image-guided therapy in patients diagnosed with ARVC.

Programmed Ventricular Stimulation: Risk Stratification and Guiding Antiarrhythmic Therapies

Electrophysiologic testing with programmed ventricular stimulation (PVS) has been utilized to induce ventricular tachycardia (VT), thereby improving risk stratification for patients with ischemic and nonischemic cardiomyopathies and determining the effectiveness of antiarrhythmic therapies, especially catheter ablation. A variety of procedural aspects can be modified during PVS in order to alter the sensitivity and specificity of the test including the addition of multiple baseline pacing cycle lengths, extrastimuli, and pacing locations. The definition of a positive result is also critically important, which has varied from exclusively sustained monomorphic VT (>30 seconds) to any ventricular arrhythmia regardless of morphology. In this review, we discuss the history of PVS and evaluate its role in sudden cardiac death risk stratification in a variety of patient populations. We propose an approach to future investigations that will capitalize on the unique ability to vary the sensitivity and specificity of this test. We then discuss the application of PVS during and following catheter ablation. The strategies that have been utilized to improve the efficacy of intraprocedural PVS are highlighted during a discussion of the limitations of this probabilistic strategy. The role of noninvasive programmed stimulation is also reviewed in predicting recurrent VT and informing management decisions including repeat ablations, modifications in antiarrhythmic drugs, and implantable cardioverter-defibrillator programming. Based on the available evidence and guidelines, we propose an approach to future investigations that will allow clinicians to optimize the use of PVS for risk stratification and assessment of therapeutic efficacy.

Multimodality imaging predictors of sudden cardiac death

Sudden cardiac death (SCD) is the worst clinical event occurring in the clinical context of cardiomyopathies. Current guidelines recommend using LV ejection fraction as the only imaging-derived parameter to identify patients who may benefit from ICD implantation in cardiomyopathies with reduced ejection fraction; however, a relevant proportion of high-risk population is left with unmet therapeutic goal. In case of dilated, hypertrophic, or arrhythmogenic cardiomyopathies, there is still a room for more sensitive and specific risk markers for identifying a cluster at higher risk of SCD. In this paper, we reviewed the evidence supporting the use of advanced echocardiography, CMR, and nuclear cardiology for SCD stratification in patients with the most common cardiomyopathies. The added value of these modalities may be explained on the basis of tissue characterization, especially scar detection, a central player in the pathogenesis of arrhythmias. Therefore, integration of these modalities to our everyday clinical practice may help in dealing with the gray zones where current guidelines are still ineffective for patient selection.

Usefulness of Total 12-Lead QRS Voltage for Diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy in Patients With Heart Failure Severe Enough to Warrant Orthotopic Heart Transplantation and Morphologic Illustration of Its Cardiac Diversity

Although several electrocardiographic features of arrhythmogenic right ventricular cardiomyopathy (ARVC) (also called dysplasia) have been described, total 12-lead QRS voltage is not one of them. This report describes total 12-lead QRS voltage in 11 patients with ARVC who underwent orthotopic heart transplantation (OHT) because of progressively severe heart failure. Additionally, it illustrates the varied morphologic features of ARVC. The total 12-lead nonpaced QRS voltages before OHT ranged from 28 to 118 mm (mean 74 ± 32), and those in the paced tracings, from 33 to 129 mm (62 ± 32). The voltages are the lowest we have encountered among 12 previously reported cardiovascular conditions. The heart weights among the 11 ARVC patients ranged from 285 to 670 g (mean 448 ± 125). Very low 12-lead QRS voltage is characteristic of patients with ARVC with heart failure severe enough to warrant OHT, and thus may serve as a clue to its diagnosis.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia in Saudi Arabia: a single-center experience with long-term follow-up

BACKGROUND AND OBJECTIVES

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a rare genetic disorder that primarily involves the right ventricle (RV). It is characterized by progressive replacement of RV myocardium by fibrofatty tissues. It commonly presents with ventricular tachycardia (VT) of RV origin and may result in RV failure. The aim of this study is to evaluate the clinical characteristics of adult patients with ARVC/D treated at the Heart Centre, King Faisal Specialist Hospital and Research Centre (KFSH&RC), Riyadh, Saudi Arabia.

DESIGN AND SETTINGS

This is a retrospective study of patients with ARVC/D diagnosed and treated at the KFSH&RC Heart Centre in Riyadh.

PATIENTS AND METHODS

Twenty-two cases with ARVC/D with regular follow-up at our Heart Centre from January 2007 to May 2010 were included in this study. The diagnosis of ARVC/D was made according to the revised International Task Force Criteria. The clinical data were collected from patients' charts and electronic medical records.

RESULTS

The majority of patients were males (18; 82%). The diagnosis of ARVC/D was definite in 18 patients (82%), borderline in 2 (9%), and possible in 2 (9%). The mean age at diagnosis was 33.3 years. The follow-up period ranged from 29 to 132 months, with a mean follow-up period of 84 months. Ten patients presented with sustained VT, and 3 were survivors of cardiac arrest. Electrocardiogram abnormalities were present in 16/22 patients (72.7%). Echocardiographic changes meeting major diagnostic criteria were seen in 16 patients (76%). Cardiac magnetic resonance imaging was performed in 11 patients, and showed changes compatible with major diagnostic criteria in 7 patients (64%). Implantable cardioverter defibrillators (ICDs) were implanted in 17 patients; 8 had appropriate ICD shocks and 5 had inappropriate ICD shocks. Antitachycardia pacing was effective in terminating most of the VT/ventricular fibrillation episodes.

CONCLUSION

ARVC/D is a rare but increasingly recognized heart muscle disease seen in Saudi Arabia and other parts of the world. It is associated with a highly nonspecific presentation. VT of RV origin is a common presentation for this disease. Antiarrhythmic medications and ICD implantation are the main management options.

Is cardiac MRI an effective test for arrhythmogenic right ventricular cardiomyopathy diagnosis?

AIM: To evaluate the referrals with suspected arrhythmogenic right ventricular cardiomyopathy (ARVC) and compare cardiac MR (cMR) findings against clinical diagnosis.

METHODS: A retrospective analysis of 114 (age range 16 to 83, males 55% and females 45%) patients referred for cMR with a suspected diagnosis of ARVC between May 2006 and February 2010 was performed after obtaining institutional approval for service evaluation. Reasons for referral including clinical symptoms and family history of sudden death, electrocardiogram and echo abnormalities, cMR findings, final clinical diagnosis and information about clinical management were obtained. The results of cMR were classified as major, minor, non-specific or negative depending on both functional and tissue characterisation and the cMR results were compared against the final clinical diagnosis.

RESULTS: The most common reasons for referral included arrhythmias (30%) and a family history of sudden death (20%). Of the total cohort of 114 patients: 4 patients (4%) had major cMR findings for ARVC, 13 patients (11%) had minor cMR findings, 2 patients had non-specific cMR findings relating to the right ventricle and 95 patients had a negative cMR. Of the 4 patients who had major cMR findings, 3 (75%) had a positive clinical diagnosis. In contrast, of the 13 patients who had minor cMR findings, only 2 (15%) had a positive clinical diagnosis. Out of the 95 negative patients, clinical details were available for 81 patients and none of them had ARVC. Excluding the 14 patients with no clinical data and final diagnosis, the sensitivity of the test was 100%, specificity 87%, positive predictive value 29% and the negative predictive value 100%.

CONCLUSION: CMR is a useful tool for ARVC evaluation because of the high negative predictive value as the outcome has a significant impact on the clinical decision-making.

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC/D): A Systematic Literature Review

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a genetic form of cardiomyopathy (CM) usually transmitted with an autosomal dominant pattern. It primary affects the right ventricle (RV), but may involve the left ventricle (LV) and culminate in biventricular heart failure (HF), life threatening ventricular arrhythmias and sudden cardiac death (SCD). It accounts for 11%-22% of cases of SCD in the young athlete population. Pathologically is characterized by myocardial atrophy, fibrofatty replacement and chamber dilation. Diagnosis is often difficult due to the nonspecific nature of the disease and the broad spectrum of phenotypic variations. Therefore consensus diagnostic criteria have been developed and combined electrocardiography, echocardiography, cardiac magnetic resonance imaging (CMRI) and myocardial biopsy. Early detection, family screening and risk stratification are the cornerstones in the diagnostic evaluation. Implantable cardioverter-defibrillator (ICD) implantation, ablative procedures and heart transplantation are currently the main therapeutic options.

Some previously neglected examples of arrhythmogenic right ventricular dysplasia/cardiomyopathy and frequency of its various reported manifestations

Four patients are described with either parchment-like thinning or partial but extensive myocyte depletion with severe fatty or fibrofatty infiltration of the free wall of the right ventricle in its outflow tract, including 2 previously reported patients who also had focal parchment-like thinning of the left ventricular free wall. Three had documented ventricular tachycardia, and the remaining patient had sudden death as his first and only manifestation of heart disease. Three patients had severe heart failure: in 1, it was fatal, and the other 2 underwent cardiac transplantation. Necropsy cases of parchment-heart syndrome before 1980 are reviewed, as well as large series of cases with arrhythmogenic right ventricular dysplasia (ARVD) reported subsequently. It is suggested that ARVD is not an ideal name for this condition, because malignant ventricular arrhythmias are not universal, the left ventricular free wall and/or ventricular septum are sometimes involved, and the name "ARVD" neglects the fact that severe heart failure may be prominent in these patients. The right ventricular wall can be thin or parchment-like, or it may not be thinned but consist mainly of adipose tissue with or without focal fibrous tissue and a few islands of myocytes. Nevertheless, because the name "ARVD" has been commonly used and recognized for >30 years, it is probably best retained for this condition.

Clinical and genetic characterization of families with arrhythmogenic right ventricular dysplasia/cardiomyopathy provides novel insights into patterns of disease expression

BACKGROUND

According to clinical-pathological correlation studies, the natural history of arrhythmogenic right ventricular dysplasia/cardiomyopathy is purported to progress from localized to global right ventricular dysfunction, followed by left ventricular (LV) involvement and biventricular pump failure. The inevitable focus on sudden death victims and transplant recipients may, however, have created a skewed perspective of a genetic disease. We hypothesized that unbiased representation of the spectrum of disease expression in arrhythmogenic right ventricular dysplasia/cardiomyopathy would require in vivo assessment of families in a genetically heterogeneous population.

METHODS AND RESULTS

A cohort of 200 probands and relatives satisfying task force or modified diagnostic criteria for arrhythmogenic right ventricular dysplasia/cardiomyopathy underwent comprehensive clinical evaluation. Desmosomal mutations were identified in 39 individuals from 20 different families. Indices of structural severity correlated with advancing age and were increased in long-term endurance athletes. Fulfillment of modified criteria indicated phenotypically mild disease, whereas asymptomatic status did not. In >80%, ECG, rhythm monitoring, and/or gadolinium-enhanced cardiovascular magnetic resonance were suggestive of LV involvement, the extent of which often was marked among individuals with chain-termination mutations and/or desmoplakin disease. Three patterns of disease expression were identified: (1) classic, with isolated right ventricular disease or LV involvement in association with significant right ventricular impairment; (2) left dominant, with early and prominent LV manifestations and relatively mild right-sided disease; and (3) biventricular, characterized by parallel involvement of both ventricles.

CONCLUSIONS

LV involvement in arrhythmogenic right ventricular dysplasia/cardiomyopathy may precede the onset of significant right ventricular dysfunction. Recognition of disease variants with early and/or predominant LV involvement supports adoption of the broader term arrhythmogenic cardiomyopathy.

Arrhythmogenic right ventricular dysplasia: a United States experience

BACKGROUND

Arrhythmogenic right ventricular dysplasia (ARVD) is an inherited cardiomyopathy characterized by right ventricular dysfunction and ventricular arrhythmias. The purpose of our study was to describe the presentation, clinical features, survival, and natural history of ARVD in a large cohort of patients from the United States.

METHODS AND RESULTS

The patient population included 100 ARVD patients (51 male; median age at presentation, 26 [interquartile range {IQR}, 18 to 38; range, 2 to 70] years). A familial pattern was observed in 32 patients. The most common presenting symptoms were palpitations, syncope, and sudden cardiac death (SCD) in 27%, 26%, and 23% of patients, respectively. Among those who were diagnosed while living (n=69), the median time between first presentation and diagnosis was 1 (range, 0 to 37) year. During a median follow-up of 6 (IQR, 2 to 13; range, 0 to 37) years, implantable cardioverter/defibrillators (ICD) were implanted in 47 patients, 29 of whom received an appropriate ICD discharge, including 3 patients who received the ICD for primary prevention. At follow-up, 66 patients were alive, of whom 44 had an ICD in place, 5 developed signs of heart failure, 2 had a heart transplant, and 18 were on drug therapy. Thirty-four patients died either at presentation (n=23: 21 SCD, 2 noncardiac deaths) or during follow-up (n=11: 10 SCD, 1 of biventricular heart failure), of whom only 3 were diagnosed while living and 1 had an ICD implanted. On Kaplan-Meier analysis, the median survival in the entire population was 60 years.

CONCLUSIONS

ARVD patients present between the second and fifth decades of life either with symptoms of palpitations and syncope associated with ventricular tachycardia or with SCD. Diagnosis is often delayed. Once diagnosed and treated with an ICD, mortality is low. There is a wide variation in presentation and course of ARVD patients, which can likely be explained by the genetic heterogeneity of the disease.

Predictors of adverse outcome in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy: long term experience of a tertiary care centre

OBJECTIVE

To investigate the predictors for adverse clinical outcome in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) during long term follow up.

METHODS

61 patients with ARVD/C were studied to assess the impact of family history, clinical findings, surface ECG parameters, echocardiographic findings, and electrophysiological findings on clinical outcome. The prevalence of these risk factors were compared in two patient groups: group A (patients with adverse clinical outcome: sudden cardiac death, death from heart failure, or heart transplant) and group B (survivors excluding patients who received a heart transplant).

RESULTS

Mean age at first diagnosis was 44 (14) years. The mean follow up duration was 55 (47) months. Ten patients (16%) died during follow up. The cause of death of eight of these patients was probably arrhythmic. Two patients died of advanced heart failure. Five patients underwent heart transplantation because of terminal heart failure. Risk factors significantly associated with adverse outcome were history of congestive heart failure (p < 0.001), the presence of left ventricular involvement on echocardiography (p < 0.001), left atrial dilatation (p < 0.05), prolonged PR duration (p < 0.01), prolonged QRS in V1 (p < 0.05), and bundle branch block (p < 0.05). In multivariate analysis, history of congestive heart failure and presence of left ventricular involvement were identified as independent risk predictors for an adverse outcome.

CONCLUSIONS

Congestive heart failure and left ventricular involvement are independently associated with adverse outcome in patients with ARVD/C during long term follow up.

Implantable cardioverter-defibrillators in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy

OBJECTIVES

The aim of this study was to assess the outcome of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) patients treated with an implantable cardioverter-defibrillator (ICD).

BACKGROUND

Arrhythmogenic right ventricular dysplasia/cardiomyopathy is associated with tachyarrhythmia and an increased risk of sudden death.

METHODS

This study included 42 ARVD/C patients with ICDs (52% male, age 6 to 69 years, median 37 years) followed at our center.

RESULTS

Mean follow-up was 42 +/- 26 months (range 4 to 135 months). Complications associated with ICD implantation included need for lead repositioning (n = 3) and system infection (n = 2). During follow-up, one patient died of a brain malignancy and one had heart transplantation. Lead replacement was required in six patients as a result of lead fracture and insulation damage (n = 4) or change in thresholds (n = 2). During this period, 33 of 42 (78%) patients received a median of 4 (range 1 to 75) appropriate ICD interventions. The median period between ICD implantation and the first firing was 9 months (range 0.1 to 66 months). The ICD firing storms were observed in five patients. Inappropriate interventions were seen in 10 patients. Predictors of appropriate firing were induction of ventricular tachycardia (VT) during electrophysiologic study (EPS) (84% vs. 44%, p = 0.024), detection of spontaneous VT (70% vs. 15%, p = 0.001), male versus female gender (91% vs. 65%, p = 0.04), and severe right ventricular dilation (39% vs. 0%, p = 0.013). Using multivariate analysis, VT induction during EPS was associated with increased risk for firing in ARVD/C patients; odds ratio 11.2 (95% confidence interval 1.23 to 101.24, p = 0.031).

CONCLUSIONS

Patients with ARVD/C have a high arrhythmia rate requiring appropriate ICD interventions. The ICD therapy appears to be well tolerated and important in the management of patients with ARVD/C.

Filtered QRS Duration on Signal-Averaged Electrocardiography Predicts Inducibility of Ventricular Tachycardia in Arrhythmogenic Right Ventricle Dysplasia

Treatment of arrhythmogenic right ventricular dysplasia (ARVD) is mostly based on the prevention of sudden cardiac death that results from arrhythmias. A clinical history suggestive of ARVD requires careful evaluation including electrophysiological study. The potential ability to identify those patients who will have inducible VT with electrophysiological study will enable better risk stratification and selection of vulnerable patients for electrophysiologically guided therapy. The purpose of the study was to evaluate the predictive ability of signal-averaged electrocardiography (SAECG) to predict inducibility of VT in patients with ARVD. The patient population consisted of 31 ARVD patients diagnosed with McKenna's criteria who underwent electrophysiological study. Electrophysiological study was considered positive if sustained monomorphic VT was induced. The sensitivity, specificity, and predictive accuracy of various SAECG criteria for inducibility of sustained monomorphic VT were also calculated. Twenty-one patients had inducible VT. The filtered QRS duration (fQRS), duration of signal <40 uV (LAS40), and root mean square voltage in the last 40 ms of QRS duration (RMS40) in ARVD patients induced versus noninduced were 122 +/- 21 and 103 +/- 8 ms (P=0.007), 45 +/- 20 and 28 +/- 14 ms (P=0.02), 19 +/- 19 and 32 +/- 22 uV (0.03), respectively. The ejection fractions were comparable in both groups. fQRS duration > or =110 ms had sensitivity of 91%, specificity of 90%, and a total predictive accuracy of 90% in predicting inducibility of VT in these patients. Filtered QRS duration on SAECG is predictive of electrophysiological study outcome in ARVD. Further studies will be needed to determine if SAECG results can predict the development of ventricular arrhythmias during follow-up.

Noninvasive risk stratification in arrhythmogenic right ventricular cardiomyopathy

The natural history of arrhythmogenic right ventricular cardiomyopathy is determined by the electrical instability of the dystrophic myocardium, which can precipitate arrhythmic cardiac arrest any time during the course of the disease and by the progressive myocardial loss that results in ventricular dysfunction and heart failure. Sudden death accounts for the majority of the fatal events but its occurrence is mostly unpredictable. There are no prospective and controlled studies assessing clinical markers that can predict the occurrence of life-threatening ventricular arrhythmias. However, the noninvasive risk profile, which emerges from retrospective analysis of clinical and pathologic series, is characterized by history of syncope, physical exercise, spontaneous ventricular tachycardia or ventricular fibrillation, right ventricular dysfunction, left ventricular involvement, right precordial negative T wave, right bundle branch block, QT-QRS dispersion, right precordial ST-segment elevation and late potentials. At present only QRS dispersion, history of syncope and right and/or left ventricular abnormalities at radionuclide angiography proved to be independent noninvasive predictors of sudden death.

Utility of SAECG in arrhythmogenic right ventricle dysplasia

BACKGROUND

Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by progressive replacement of RV myocardium with fibro-adipose tissue thought to be responsible for the presence of late potentials (LP) detected by SAECG. The general consensus on the role of SAECG in the diagnosis and prognosis of patients with ARVD is lacking. The purpose of this systematic review was to better define the role of SAECG in ARVD.

METHODS

An extensive review of literature was done to specifically describe the prevalence of LP in ARVD and its determinants, explore the various options available to improve the diagnostic ability of SAECG, and provide recommendations for proper utilization of this technique.

RESULTS

LPs are frequent in ARVD (47-100%), and more prevalent in severe disease and in patients with documented spontaneous VT. SAECG is a useful test in following the characteristic evolutivity of the disease. 4-16% of normal family members of patients with ARVD also have abnormal SAECG results. Detection of LP in ARVD can be improved by employing a high-pass filter of 25 Hz and specifically looking for changes in the Z leads.

CONCLUSIONS

SAECG testing should be considered a standard part of the evaluation of patients with known or suspected ARVD. Further research is needed to confirm the value of SAECG testing in predicting arrhythmia risk and assessing the rate of disease progression, as well as to determine if greater prevalence of SAECG abnormalities in family members of patients with ARVD represents early detection of ARVD. The ongoing multidisciplinary study of right ventricular dysplasia will hopefully answer some of these questions.

Electrophysiological characteristics and outcome in patients with idiopathic right ventricular arrhythmia compared with arrhythmogenic right ventricular dysplasia

BACKGROUND

Idiopathic right ventricular arrhythmias (IRVA) are responsive to medical and ablative treatment and have a benign prognosis. Arrhythmias caused by right ventricular dysplasia (ARVD) are refractory to treatment and may cause sudden death. It is difficult to distinguish between these two types of arrhythmia.

OBJECTIVE

To differentiate patients with IRVA and ARVD by a conventional electrophysiological study.

METHODS

56 patients with a right ventricular arrhythmia were studied. They had no history or signs of any cardiac disease other than right ventricular dysplasia. They were classified as having IRVA (n = 41) or ARVD (n = 15) on the basis of family history, ECG characteristics, and various imaging techniques. They were further investigated by standard diagnostic electrophysiology.

RESULTS

The two groups were clearly distinguished by the electrophysiological study in the following ways: inducibility of ventricular tachycardia by programmed electrical stimulation with ventricular extrastimuli (IRVA 3% v ARVD 93%, p < 0.0001); presence of more than one ECG morphology during tachycardia (IRVA 0% v ARVD 73%, p < 0.0001); and fragmented diastolic potentials during ventricular arrhythmia (IRVA 0% v ARVD 93%, p < 0.0001). Data from the clinical follow up in these patients supported the diagnosis derived from the electrophysiological study.

CONCLUSIONS

Patients with IRVA or ARVD can be distinguished by specific electrophysiological criteria. A diagnosis of ARVD can be made reliably on the basis of clinical presentation, imaging techniques, and an electrophysiological study.

Genotype-phenotype assessment in autosomal recessive arrhythmogenic right ventricular cardiomyopathy (Naxos disease) caused by a deletion in plakoglobin

OBJECTIVES

The purpose of this study was to examine the genotype-phenotype relation with respect to penetrance, age and severity of expression, disease progression and prognosis in a recessively inherited arrhythmogenic right ventricular cardiomyopathy (ARVC).

BACKGROUND

Naxos disease is a recessively inherited ARVC caused by a mutation in the gene encoding plakoglobin (cell adhesion protein) in which the cardiac phenotype is associated with palmoplantar keratoderma and woolly hair.

METHODS

Twelve families with Naxos disease underwent cardiac and molecular genetic investigation. Serial cardiac assessment with annual resting 12-lead and 24-h ambulatory electrocardiogram (ECG) and two-dimensional echocardiography was performed during 1 to 16 years, median 7 +/- 6 years in all 78 surviving members.

RESULTS

Twenty-eight surviving members were homozygous and 40 were heterozygous for the mutation. All adults who were homozygous (n = 26) fulfilled the diagnostic criteria for ARVC, the youngest by the age of 13 years. In eight who were heterozygous, minor ECG or echocardiographic abnormalities were observed. Of the 26 subjects who were affected homozygotes, 92% showed ECG abnormalities, 92% ventricular arrhythmias, 100% right ventricular structural alterations and 27% left ventricular involvement. During follow-up (10 +/- 6 years), 16 (62%) developed structural progression, 12 (46%) arrhythmic events and 7 (27%) heart failure. The annual disease-related and sudden death mortality was 3% and 2.3%, respectively.

CONCLUSIONS

Autosomal recessive ARVC caused by a mutation in plakoglobin was 100% penetrant by adolescence. Affected subjects who were homozygous experienced progressive disease with adverse prognosis. A minority of subjects who were heterozygous showed minor ECG/echocardiographic changes, but clinically significant disease did not develop.

Pacing in right ventricular dysplasia after disconnection surgery

This report describes a 33-year-old patient with arrhythmogenic right ventricular (RV) dysplasia who had a dual chamber pacemaker implanted at age 23 years for drug-induced bradycardia. Pacing was continued after right ventricular free-wall disconnection (RVFWD) at age 24 years. Her pacemaker was not replaced after battery depletion 7 years later. She presented the following year in severe right-sided heart failure. Her old pacemaker generator was replaced. This was followed by rapid resolution of her clinical failure and return to a full, active, physical lifestyle. This observation suggests the potential benefit of dual chamber pacing in patients with RV dysplasia after RVFWD.

Initiating sequences in exercise induced idiopathic ventricular tachycardia of left bundle branch-like morphology

Initiating sequences for VT may infer the underlying arrhythmogenic mechanisms. This study examines the initiating sequences of exercise induced idiopathic VT of left bundle branch block-like (LBBB-like) morphology and makes an attempt to relate these to clinical aspects and the mechanisms of arrhythmia. Thirty-two patients (mean age 33.4 +/- 13.2 years; 18 men) with exercise induced VT in the absence of structural cardiac abnormality on history, clinical examination, and noninvasive and invasive investigations were divided into two groups on the basis of the initiating sequence of VT on exercise. Group I consisted of patients with long-short sequence of RR intervals prior to the onset of VT (initiating/preinitiating cycle length ratio < or = 0.78). Group II consisted of patients without changes in cycle length prior to VT. Group I mechanism would suggest delayed afterdepolarizations (DADs) or reentry whereas group II mechanism triggered activity due to early afterdepolarizations. Fourteen patients (group I) had long-short sequence and 18 patients (group II) were without cycle length changes prior to VT initiated during exercise. VT axis was inferior in all 18 patients in group II but only in 9 patients in group I (P = 0.02). In these predefined patient groups, sustained monomorphic VT could not be initiated by programmed stimulation in any patient in group I, whereas four patients in group II had inducible VT. Patients in group II also had higher incidence of sustained VT on ambulatory monitoring (P < 0.05). The two groups did not differ in other respects. This study demonstrates the existence of at least two possible mechanisms of initiation of exercise induced idiopathic VT of LBBB-like morphology. VT initiated without cycle length changes is more common, more likely to have an inferior axis suggesting an outflow tract origin, and is probably related to triggered activity secondary to DADs. VT initiated with a long-short sequence is more often nonsustained and may have a superior axis suggesting an origin from the body or septal region of the ventricle. The two groups, therefore, exhibit differences in electrophysiological characteristics that may aid classification and therapy of this arrhythmia.

Increased atrial vulnerability in arrhythmogenic right ventricular disease

Supraventricular tachyarrhythmias (SVTA) may occur in patients with the arrhythmogenic right ventricular dysplasia (ARVD). The purpose of the study was to evaluate the incidence of SVTA in 47 patients with ARVD proved by right ventricular angiography. Thirty-three men and 14 women, aged 21 to 72 years (mean 44 +/- 18) were admitted for nonsustained or sustained ventricular tachycardia. Eight patients had a history of spontaneous SVTA several years before ventricular tachycardia occurrence. Protocol of the study consisted of programmed atrial stimulation with one and two extrastimuli delivered during sinus rhythm and two driven rhythms (600 and 400 msec), programmed ventricular stimulation with up to three extrastimuli and was performed in the control state and after infusion of isoproterenol. The results of programmed atrial stimulation were compared with those obtained in 36 asymptomatic subjects without heart disease and with a mean age of 50 +/- 18 years (control group). Sustained SVTA (> 1 minute) was induced in seven of eight patients with spontaneous SVTA, in 27 (69%) of those with ARVD, who did not have spontaneous SVTA, and in two control subjects (5.5%) (p < 0.001). SVTA was inducible in the control state, but ventricular tachycardia induction required isoproterenol in 11 of 27 patients. Two patients without SVTA history but with inducible SVTA developed later spontaneous SVTA. ARVD was associated with a significantly higher incidence of inducible SVTA than in a control population. Supraventricular tachycardias may precede ventricular tachycardias. This association argues for a diffuse myocardial disorder in ARVD.

Spectrum of clinicopathologic manifestations of arrhythmogenic right ventricular cardiomyopathy/dysplasia: a multicenter study

OBJECTIVES

The aim of the present investigation was to redefine the clinicopathologic profile of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC), with special reference to disease progression and left ventricular (LV) involvement.

BACKGROUND

Long-term follow-up data from clinical studies indicate that ARVC is a progressive heart muscle disease that with time may lead to more diffuse right ventricular (RV) involvement and LV abnormalities and culminate in heart failure.

METHODS

Forty-two patients (27 male, 15 female; 9 to 65 years old, mean [+/-SD] age 29.6 +/- 18) from six collaborative medical centers, with a pathologic diagnosis of ARVC at autopsy or heart transplantation, and with the whole heart available, were studied according to a specific clinicomorphologic protocol.

RESULTS

Thirty-four patients died suddenly (16 during effort); 4 underwent heart transplantation; 2 died as a result of advanced heart failure; and 2 died of other causes. Sudden death was the first sign of disease in 12 patients; the other 30 had palpitations, with syncope in 11, heart failure in 8 and stroke in 3. Twenty-seven patients experienced ventricular arrhythmias (ventricular tachycardia in 17), and 5 received a pacemaker. Ten patients had isolated RV involvement (group A); the remaining 32 (76%) also had fibrofatty LV involvement that was observed histologically only in 15 (group B) and histologically and macroscopically in 17 (group C). Patients in group C were significantly older than those in groups A and B (39 +/- 15 years vs. 20 +/- 8.8 and 25 +/- 9.7 years, respectively), had significantly longer clinical follow-up (9.3 +/- 7.3 years vs. 1.2 +/- 2.1 and 3.4 +/- 2.2 years, respectively) and developed heart failure significantly more often (47% vs. 0 and 0, respectively). Patients in groups B and C had warning symptoms (80% and 87%, respectively, vs. 30%) and clinical ventricular arrhythmias (73% and 82%, respectively, vs. 20%) significantly more often than patients in group A. Hearts from patients in group C weighed significantly more than those from patients in groups A and B (500 +/- 150 g vs. 328 +/- 40 and 380 +/- 95 g, respectively), whereas hearts from both group B and C patients had severe RV thinning (87% and 71%, respectively, vs. 20%) and inflammatory infiltrates (73% and 88%, respectively, vs. 30%) significantly more often than those from group A patients.

CONCLUSIONS

LV involvement was found in 76% of hearts with ARVC, was age dependent and was associated with clinical arrhythmic events, more severe cardiomegaly, inflammatory infiltrates and heart failure. ARVC can no longer be regarded as an isolated disease of the right ventricle.

Syncopal sustained ventricular tachycardia in a patient with right ventricular dysplasia

A 41-year-old man was hospitalized for syncopal sustained ventricular tachycardia with left bundle branch morphology. Diagnostic screening confirmed a right ventricular dysplasia: fibrofatty replacement of myocardium on endomyocardial biopsy and severe dilation of right ventricle with no left ventricular impairment was documented. His bundle recording showed an abnormally long HV interval, and programmed ventricular stimulation induced high-rate sustained ventricular tachycardia with left bundle branch block morphology associated with reduced systolic blood pressure and dizziness. Right ventricular burst pacing proved to be effective in restoring sinus rhythm. A single lead pectoral cardioverter-defibrillator was implanted and programmed for VVI and antitachycardia pacing, as first ventricular tachycardia therapeutic intervention. During 6-month follow-up, 1 asymptomatic ventricular tachycardia recurrence terminated by antitachycardia pacing was reported by the device. The possible role of the other therapeutic options such as drugs, ablation, and surgery for this specific case is also discussed.

Arrhythmogenic right ventricular cardiomyopathy. Dysplasia, dystrophy, or myocarditis?

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a frequent cause of sudden death in young individuals and athletes. Although familial occurrence has been documented and a gene defect was recently localized on chromosome 14q23-q24 the etiopathogenesis of the disease is still obscure.

METHODS AND RESULTS

A pathological study was conducted in 30 hearts with ARVC (age range, 15 to 65 years; mean, 28 years). In the 27 autopsy cases, the mode of death was sudden in 24 and congestive heart failure in 3. ECG, available in 19 cases, showed inverted T waves in the right precordial leads in 15 cases (79%) and ventricular arrhythmias in 15 (79%). Right ventricular aneurysms were present in 15 hearts (50%) and located in the inferior wall in 12. Left ventricle and ventricular septum were involved in 14 (47%) and 6 (20%) cases, respectively. Scattered foci of lymphocytes with myocardial death were observed in 20 cases (67%). Electron microscopy studies, although confirming the myocardial death and lymphocyte infiltrates, did not show any specific ultrastructural substrate. Two pathological patterns, fatty (40%) and fibrofatty (60%), were identified. The fibrofatty pattern was associated with a thinner right ventricular wall (P < .0001) and a higher occurrence of focal myocarditis (P < .001). In sections of right ventricular free wall with maximal fatty infiltration, the mean percentage area of fatty tissue was 35.9 +/- 11.1% in control versus 80.4 +/- 9.6% in the ARVC, fatty variety (P < .00001). Involvement of the left ventricle and/or ventricular septum, right ventricular aneurysms, and inflammation were found almost exclusively in the fibrofatty variety.

CONCLUSIONS

In the fibrofatty variety of ARVC, the myocardial atrophy appears to be the consequence of acquired injury (myocyte death) and repair (fibrofatty replacement), mediated by patchy myocarditis. Whether the inflammation is a primary event or a reaction to spontaneous cell death remains unclear.

Time-domain signal-averaged electrocardiogram in nonischemic ventricular tachycardia

The prevalence of late ventricular potentials (LVPs) detected by signal averaged ECG (SAECG) is variable in nonischemic heart diseases. In idiopathic dilated cardiomyopathy, the prevalence increases from about 25% to 70%-90% in cases of spontaneous sustained ventricular tachycardia (VT), is not significantly correlated with hemodynamic and Holter data, and has a good positive predictive value for induced and spontaneous sustained VT. However, its predictive value for cardiac death has not been established. In primary hypertrophic cardiomyopathy, LVPs are rare (about 10%), not correlated to hemodynamic data, enhanced in cases of spontaneous sustained VT (up to 77%), and have a good predictive value of induced VT. LVP-SAECG are frequent in arrhythmogenic right ventricular dysplasia (ARVD) (70%-80%). They can identify patients with VT and an unapparent or limited form of this disease, or ARVD with few ventricular arrhythmias. The prevalence (26%-37%) of LVPs in mitral valve prolapse is clearly higher than in normal individuals or in other valvular diseases and is enhanced in cases of spontaneous and induced VT. Its significance remains speculative. After surgical repair of tetralogy of Fallot, LVPs can identify a group of patients with higher probability of induced and spontaneous risk of VT. The usefulness and significance of LVPs in other nonischemic cardiac diseases have not to date been established. In "true" idiopathic VT, without proved structural cardiac disease, the prevalence of LVPs does not exceed that observed in normal individuals (0%-5%), but in "apparent" idiopathic VT the prevalence of LVPs rises to 20%-40%. In these latter cases more invasive techniques must be used to discover a limited form of myocardiopathy.

Current approaches in patients with ventricular tachyarrhythmias

The article has summarized the studies and ongoing trials looking at the significance and treatment of ventricular tachyarrhythmias. In most instances, the presence of these arrhythmias is associated with an increased risk of future arrhythmic events. Electrophysiologic studies are helpful in risk stratification in patients with coronary artery disease but can be misleading in the setting of dilated cardiomyopathy and often produce nonspecific results in patients with HCM. The need for an invasive electrophysiologic study is crucial in the diagnosis of certain ventricular arrhythmias that are amenable to cure with radiofrequency catheter ablation, such as idiopathic ventricular tachycardia and BBR-VT. The correct approach for patients with SVT not amenable to catheter ablation remains to be determined. In deciding whether to use a device or drug therapy, however, one should take into consideration the degree of left ventricular dysfunction and the overall health status of the patient. For example, device implantation clearly reduces sudden death in patients with severe left ventricular dysfunction but may not change total mortality because these same patients may die of congestive heart failure. Device therapy might be more cost-effective for patients with less severe depression of left ventricular function.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy: a review

Right ventricular dysplasia is being recognized with increasing frequency. It should be considered as a cause of ventricular tachycardia of left bundle branch block configuration and/or sudden unexpected death particularly during exercise in young men. The electrocardiogram (ECG) may show anterior precordial T wave inversion, particularly in lead V2 and/or a QRS complex duration > or = 110 ms in the right precordial leads. Echocardiographic studies focusing on the size and wall-motion abnormalities of the right ventricle are useful in confirming the diagnosis. Radionuclide angiography usually shows a moderately or markedly depressed right ventricular ejection fraction with normal or relatively well preserved left ventricular function. Cinemagnetic resonance imaging demonstrates abnormal fatty infiltration of the right ventricular myocardium and can show increased right ventricular dimensions as well as wall-motion abnormalities. Contrast ventricular angiography remains the gold standard to establish the diagnosis but must be performed with appropriate views and with care to avoid ventricular premature beats. Quantitative analysis of right ventricular dimensions can be performed in selected centers. Three-dimensional echocardiography is a promising approach to evaluate right ventricular wall-motion abnormalities as well as to demonstrate enlargement. The etiology and pathogenesis of this condition is not clear. A familial incidence has been well-documented in certain areas and an abnormal gene has been identified. Sporadic cases are the most common. In contrast to Uhl's anomaly, characterized pathologically by areas of paper thin myocardium, the right ventricular free wall is minimally decreased in thickness. Histologically there appears to be a replacement of musculature by fatty tissue. Medical therapy with sotalol or amiodarone, or combination therapy (Class Ic drugs plus beta-blocking drugs, or amiodarone plus beta-blocking drugs) is frequently effective in preventing recurrent ventricular tachycardia. Ablation using radiofrequency (RF) or direct current (DC) energy is reserved for patients who are unresponsive or intolerant of antiarrhythmic drugs. Ventricular arrhythmia recurrence of different morphology is not uncommon after apparent successful ablation. There appears to be a lower rate of successful ablation using RF energy. However, patients with this condition who have been resuscitated from sudden cardiac death or those refractory to medical treatment are candidates for ablation, implantation of an automatic cardioverter defibrillator, or cardiac transplantation. Surgery consisting of total disconnection of the right ventricle is a promising therapeutic modality.

Ventricular tachycardias with left bundle branch block morphology

The differential diagnosis of VTs with LBBB morphology includes several well-defined syndromes. Although the majority of cases are attributable to acquired structural heart disease, including ischemia, prior infarction, or dilated cardiomyopathy, consideration of specific right ventricular processes is essential to proper evaluation and treatment. The approach to older patients or those with evidence for heart disease should begin with an evaluation for coronary artery disease and an assessment of biventricular function. Careful evaluation for bundle branch reentry should be performed during electrophysiological study, especially when there is underlying conduction system disease. Younger patients, those without overt heart disease, or those with isolated right ventricular disease, should receive a complete noninvasive evaluation of right and left ventricular size and function. An abnormal SAECG or identification of intracardiac late potentials suggest right ventricular dysplasia or cardiomyopathy, whereas responsiveness to adenosine and absence of detectable heart disease support the diagnosis of idiopathic right VT. Newer techniques, including MRI, show promise in identifying subtle right ventricular disease not otherwise detectable even in the setting of presumed idiopathic right VT. Following surgical repair of selected congenital heart defects, particularly tetralogy of Fallot, symptoms of recurrent palpitations, near syncope, syncope, or aborted sudden death may be attributable to recurrent VT, and diagnostic electrophysiological study should be considered for these patients. Finally, SVTs with LBBB morphology, particularly cases associated with right-sided or septal accessory pathways, should always be considered in this differential diagnosis.

Time- and frequency-domain analyses of the signal-averaged ECG in patients with arrhythmogenic right ventricular dysplasia

BACKGROUND

Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by recurrent ventricular tachycardia of right ventricular origin and a cardiomyopathy with hypokinetic areas involving the free wall of the right ventricle. Subjects have a risk of sudden cardiac death, particularly during sports and strenuous exercise. Routine clinical examinations may be normal, but fragmented or delayed electrograms are usually recorded in the right ventricle of these patients. However, the frequency with which late potentials are detected by conventional time-domain analysis of the signal-averaged ECG (SAECG) is not high. This study evaluated the usefulness of the frequency-domain analysis of the SAECG in addition to the conventional time-domain analysis for a screening test to detect patients with ARVD.

METHODS AND RESULTS

SAECG was recorded by using a bipolar X, Y, and Z lead system in 28 patients with ARVD (mean age, 38 +/- 13 years) and 35 age-matched normal subjects (mean age, 35 +/- 11 years). The conventional time-domain analysis of the SAECG was performed at two different high-pass filter settings, 25 and 40 Hz, and the low-pass cutoff frequency was fixed at 250 Hz. The fast-Fourier transform analysis of SAECG was performed using a Blackman-Harris window. Area ratio 1 (area of 20 to 50 Hz)/(area of 0 to 20 Hz) and area ratio 2 (area of 40 to 100 Hz)/(area of 0 to 40 Hz) were calculated. In the conventional time-domain analysis, 20 (71%) and 18 (64%) patients had positive criteria at filter settings of 25 and 40 Hz, respectively. In the frequency-domain analysis, 18 (64%) and 20 (71%) patients had abnormal values in area ratios 1 and 2, respectively. Combining the time- and frequency-domain analyses, all patients were judged positive, with a sensitivity of 100% and a specificity of 94%.

CONCLUSIONS

Each result of the time- and frequency-domain analyses revealed that both methods had equivalent value. Combining the two domain analyses improved the sensitivity without reducing the specificity. These findings suggest that combining the time- and frequency-domain analyses of the SAECG may be useful as a screening test to detect patients with ARVD.

Regional myocardial sympathetic dysinnervation in arrhythmogenic right ventricular cardiomyopathy. An analysis using 123I-meta-iodobenzylguanidine scintigraphy

BACKGROUND

In patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), the frequent provocation of ventricular tachycardia during exercise, the sensitivity toward catecholamines, and the response toward antiarrhythmic drug regimen with antiadrenergic properties suggest an involvement of the sympathetic nervous system in arrhythmogenesis.

METHODS AND RESULTS

To analyze the presence, extent, and location of impaired myocardial sympathetic innervation in ARVC, 123I-meta-iodobenzylguanidine (123I-MIBG) scintigraphy was performed in 48 patients with ARVC. For comparison, 9 patients with idiopathic ventricular tachycardia and a control group of 7 patients without heart disease were investigated. In patients with ARVC, the clinical sustained (n = 25; 52%) or nonsustained (n = 23; 48%) ventricular tachycardia originated in the right ventricular outflow tract in 38 patients (79%), whereas in the remaining 10 patients (21%), the site of origin was the apical (n = 5) or inferior (n = 5) right ventricle. In 33 patients (69%), nonsustained or sustained ventricular tachycardia was provocable by exercise (n = 28 of 48; 58%) and/or by isoproterenol infusion (n = 16 of 37; 43%), whereas programmed ventricular stimulation induced sustained or nonsustained ventricular tachycardia in 16 patients each (33% each). With 123I-MIBG scintigraphy, the right ventricle was not visible in any patient. No areas of intense 123I-MIBG uptake ("hot spots") were observed. All patients of the control group and 7 of 9 patients (78%) with idiopathic ventricular tachycardia showed a uniform tracer uptake in the left ventricle. In contrast, only 8 of 48 ARVC patients (17%) showed a homogeneous distribution of 123I-MIBG uptake, whereas 40 patients (83%) demonstrated regional reductions or defects of tracer uptake. In 3 of 48 patients (6%), the defect area was < 15%; in 21 patients (44%), it was 15% to 30%; and in 16 patients (33%), it was > 30% of the polar map area of the left ventricle (mean, 23 +/- 15%; range, 0% to 57%). In 38 of 40 patients (95%) with an abnormal 123I-MIBG scan, reduced tracer uptake was located in the basal posteroseptal left ventricle, involving the adjacent lateral wall in 10, the anterior wall in 2, and the apex in 12 patients. Only 2 patients demonstrated isolated defects of the anterior or lateral wall; one involved the apex. Perfusion abnormalities in the areas of 123I-MIBG defects were excluded by stress/redistribution 201T1 single-photon emission computed tomography scintigraphy and by normal coronary angiograms in all patients. Abnormalities in 123I-MIBG scintigraphy in patients with ARVC correlated with the site of origin of ventricular tachycardia, demonstrating a regionally reduced tracer uptake in 36 of 38 patients (95%) with right ventricular outflow tract tachycardia compared with only 4 of 10 patients (40%) with other right ventricular origins of tachycardia. There was no correlation between the results of 123I-MIBG scintigraphy and the extent of right ventricular contraction abnormalities, right ventricular ejection fraction, biopsy results, coronary anatomy, or left ventricular involvement in ARVC.

CONCLUSIONS

In patients with ARVC, regional abnormalities of sympathetic innervation are frequent and can be demonstrated by 123I-MIBG scintigraphy. Sympathetic denervation appears to be the underlying mechanism of reduced 123I-MIBG uptake and may be related to frequent provocation of ventricular arrhythmias by exercise or catecholamine exposure in ARVC. Therefore, in patients with ARVC, the noninvasive detection of localized sympathetic denervation by 123I-MIBG imaging may have implications for the early diagnosis and for the choice of antiarrhythmic drugs in the treatment of arrhythmias.

Right ventricular cardiomyopathy in identical and nonidentical young twins

We describe the first sets of identical and nonidentical twins with right ventricular cardiomyopathy (RVC). Pair A: A 12-year-old boy was referred because of palpitation and syncope. Clinical and instrument examinations revealed an enlarged and depressed right ventricle (end-diastolic volume = 110 ml/m2; ejection fraction = 44%), spontaneous ventricular tachycardia, and fatty-fibrous infiltrates in the biopsy specimens. His asymptomatic, monozygotic twin showed localized involvement of the right ventricle with isolated, ventricular extrasystoles. Pair B: These 18-year-old nonidentical twin boys showed diffuse right ventricular involvement (end-diastolic volume = 110 ml/m2 and 114 ml/m2; ejection fraction = 30% and 24%, respectively), induction of sustained and nonsustained ventricular tachycardia, respectively, and fibrosis on endomyocardial biopsy. One of the boys died suddenly at rest after documented ventricular fibrillation. These cases support the hypothesis of a genetic etiology with a minor role for genotype and point to the important influence of environmental factors in determining the clinical features of the disease.

Value of the 12-lead electrocardiogram in arrhythmogenic right ventricular dysplasia, and absence of correlation with echocardiographic findings

The 12-lead electrocardiogram during sinus rhythm was studied in 20 patients with arrhythmogenic right ventricular (RV) dysplasia with symptomatic ventricular tachycardia. Findings were analyzed, together with echocardiographic evaluation of site, extent and progression of RV wall abnormalities. Electrocardiographic abnormalities were found in 90% of patients. No correlation was found between abnormalities on the initial 12-lead electrocardiogram, and the echocardiographic extent and location of RV involvement. Over time, echocardiographic progression of the disease was observed; RV size increased in 6 of 7 patients from 34 +/- 3 to 39 +/- 3 mm (p = 0.01), and there was progression in the extent of RV wall motion abnormalities in 4 of 7 patients. Analysis of serial electrocardiographic recordings did not reveal changes indicative of progression of the disease during follow-up of 71 +/- 48 months. It is concluded that electrocardiographic abnormalities suggesting arrhythmogenic RV dysplasia are present in 90% of symptomatic patients on the first electrocardiogram recorded during sinus rhythm. However, serial electrocardiographic recordings in these patients do not provide information regarding anatomic progression of the disease.

Treatment of presumed arrhythmogenic right ventricular dysplasia in an adolescent

Familial arrhythmogenic right ventricular dysplasia is a rare cardiomyopathy that is usually diagnosed on postmortem examination or on presentation with progressive congestive heart failure. We present a patient in whom an automatic implantable cardioverter-defibrillator was inserted prophylactically. A review of the condition and possible therapies is included.

Frequency analysis of signal-averaged electrocardiogram in patients with right ventricular tachycardia

OBJECTIVES

The purpose of this study was to analyze the frequency content of signal-averaged electrocardiograms (ECGs) in patients with idiopathic ventricular tachycardia of right ventricular origin and in patients with arrhythmogenic right ventricular dysplasia.

BACKGROUND

The late potentials in the time domains are usually found in patients with arrhythmogenic right ventricular dysplasia. They are not usually found in patients with idiopathic ventricular tachycardia of right ventricular origin.

METHODS

Fast Fourier transform analysis of signal-averaged ECGs was performed with the use of a Blackman-Harris window in 43 subjects: 20 normal volunteers (group I), 12 patients with idiopathic ventricular tachycardia of right ventricular origin (group II) and 11 patients with arrhythmogenic right ventricular dysplasia (group III), and the frequency spectrum was displayed in a three-dimensional graph. Area ratio (ratio of the area under the spectral plot from 40 to 120 Hz to the area from 0 to 120 Hz) was calculated in all subjects.

RESULTS

Area ratio was significantly higher in group II than in group I (243 +/- 45 vs. 196 +/- 15, p < 0.01) and significantly higher in group III (396 +/- 51) than in group I or II (p < 0.001). The high frequency components in group II were confined within the QRS complex in the three-dimensional graph, whereas those in group III extended outside the QRS complex.

CONCLUSIONS

Frequency analysis of the signal-averaged ECG with fast Fourier transform analysis can detect the high frequency components in patients with right ventricular tachycardia, including idiopathic ventricular tachycardia and arrhythmogenic right ventricular dysplasia.

Surgery for ventricular tachycardia associated with right ventricular dysplasia: disarticulation of right ventricle in 9 of 10 cases

Ten patients (nine men, one woman; mean age 39 years) with arrhythmogenic right ventricular dysplasia underwent surgery to control life-threatening drug refractory ventricular arrhythmias. All had ventricular tachycardia causing syncope and six had a history of cardiac arrest. In all a minimum of three antiarrhythmic drugs (mean five) had been ineffective. At operation, the right ventricle was grossly diseased in all patients. Ventricular tachycardias were induced and mapped intraoperatively in all patients. The surgical plan was to ablate the arrhythmogenic focus if it was less than 4 cm2; one patient was so managed. Of the remaining nine, four underwent partial (approximately 40% of the right ventricular free wall) and five underwent total right ventricular disarticulation. All survived the operation and are alive at a mean follow-up interval of 24 months (range 5 to 67). Two patients developed new sustained ventricular tachycardias. These were well tolerated and, unlike the original arrhythmias, were easily controlled by drug treatment. All patients who underwent right ventricular disarticulation manifested signs of right heart failure in the early postoperative period, but these lessened progressively with the development of systolic septal movement into the right ventricular cavity. All 10 patients are in New York Heart Association class I or II at last review. In selected patients with arrhythmogenic right ventricular dysplasia, surgery offers a curative treatment for ventricular tachycardia and should be considered for patients whose arrhythmias are life-threatening and refractory to drug treatment.

Arrhythmogenic right ventricular dysplasia

A 23-year-old man presented with recurrent exercise-induced ventricular tachycardia (VT), complicated by systemic embolisation. Catecholamine--sensitive VT was reproduced on exercise testing and programmed electrical stimulation, displaying features suggestive of enhanced automaticity as well as re-entry. Both 2D-echocardiography and gated heart pool scan showed localised dyskinetic bulging in the right ventricle. A diagnosis of arrhythmogenic right ventricular dysplasia was made. This condition should be excluded in all young patients with otherwise unexplained ventricular arrhythmias.