Ventricular tachycardias of right ventricular origin: markers of subclinical right ventricular disease

[Premature ventricular contractions and tachycardia in a structurally normal heart : Idiopathic PVC and VT]

Premature ventricular contractions (PVC) are a common, often incidental and mostly benign finding. Treatment is indicated in frequent and symptomatic PVC or in cases of worsening of left ventricular function. Idiopathic ventricular tachycardia (VT) is mostly found in patients with a structurally healthy heart. These PVC/VT usually have a focal origin. The most likely mechanism is delayed post-depolarization. Localization of the origin is based on the creation of an activation map with or without combination of pace mapping. Idiopathic PVC/VT are most frequently located on the outflow tracts of the right and left ventricles, including the aortic root. Other typical locations include the annulus of the tricuspid or mitral valve, papillary muscles and Purkinje fibers. Catheter ablation is an alternative to antiarrhythmic medication in symptomatic monomorphic PVC/VT. The success rate is good whereby mapping and ablation can often represent a challenge. This article is the fifth part of a series dedicated to specific advanced training in the field of special rhythmology and invasive electrophysiology. It describes the pathophysiological principles, types and typical findings that can be obtained during an electrophysiological investigation.

Conventional mapping and ablation of focal ventricular tachycardias in the healthy heart

Ventricular tachycardias (VT) in the healthy heart, also known as idiopathic VTs, often have a focal origin. Triggered activity due to delayed after-depolarization is the most likely mechanism of focal VTs. Localization of the site of origin of focal VTs is based on activation mapping with or without combination with pace mapping. The characteristic anatomic site of origin of idiopathic VTs is the right and left outflow tract. Other sites include the tricuspid and mitral annulus, the papillary muscles, and Purkinje fibers. Catheter ablation is indicated for monomorphic symptomatic VT and can be an alternative to antiarrhythmic drugs. Success rates are high, but mapping and ablation can be challenging. We review the main electrophysiological findings and the important clues for ablation of focal VTs. Specific considerations for each location are considered.

Right ventricular outflow tract tachycardia in children

OBJECTIVE

To assess the clinical spectrum of right ventricular outflow tract tachycardia and its management in children.

STUDY DESIGN

Five centers identified patients for retrospective review. Patients (age <18 years) demonstrating ventricular tachycardia with an inferior axis and left bundle branch block were included. Patients with structural heart disease, myocarditis, cardiomyopathy, or long QT syndrome were excluded. Demographics, clinical presentation, investigations, and treatment were analyzed. Holter data were used to quantify ectopy.

RESULTS

Patients (n = 48) were referred for evaluation of incidental findings (39/48), near syncope or syncope (7/48), or other (2/48). Investigations included magnetic resonance imaging (51%), endomyocardial biopsy (25%), and angiography (23%). Medical treatment was initiated in 26 of the 48 patients. The most common indications for treatment were frequent ectopy and symptoms. Medical treatment (P <.007) and observation alone (P <.02) were both associated with a reduction in ectopy. Symptoms persisted in 3 of 13 patients who were treated medically and in all untreated patients. At follow-up, there were no deaths and no difference in ectopy (P <.46) between patients who were treated medically and patients who were observed. Ablation was attempted in 6 of the 48 patients (successful in 4/6).

CONCLUSION

The clinical spectrum and management of right ventricular outflow tract tachycardia in children are diverse. Both medical therapy and observation alone were associated with a reduction in ectopy.

Magnetic Resonance Imaging Abnormalities in Right Ventricular Outflow Tract Tachycardia and the Prediction of Radiofrequency Ablation Outcome

BACKGROUND

Recent reports have shown abnormalities on cardiac magnetic resonance imaging (MRI) in patients with right ventricular outflow tract (RVOT) tachycardia.

OBJECTIVES

OBJECTIVES of this study were to demonstrate abnormalities on MRI and signal-averaged ECG (SAECG) in patients with RVOT tachycardia and their correlation with the outcome of radiofrequency (RF) ablation.

METHODS

We studied 41 patients with symptomatic RVOT tachycardia and 15 controls. SAECG and cardiac MRI were performed on every subject. An evaluation of structural abnormality, chamber size, function, and wall motion abnormality of the left and right ventricle was performed by MRI. Focal wall thinning was evaluated by the black blood technique and fatty infiltration was evaluated by the T1 image with and without fat suppression.

RESULTS

MRI abnormalities were demonstrated in 24 (58.5%) patients with RVOT tachycardia. The abnormalities included localized wall bulging in 22 (53.7%), focal wall thinning in 10 (24.4%), and fatty replacement in 9 (22%) patients. MRI abnormality was found in only one patient in the control group (P < 0.001). Late potentials from SAECG were demonstrated in six (10.7%) patients but none in the controls (P = 0.117). Among 29 patients who underwent RF ablation, 3 patients had a failed procedure and 3 having arrhythmia recurrence needed repeated ablation. MRI abnormalities and late potentials were associated with an unfavorable outcome of RF ablation.

CONCLUSIONS

MRI abnormalities were frequently found in patients with RVOT tachycardia. MRI abnormalities and late potentials can predict outcomes of RF ablation.

The value of magnetic resonance imaging for the diagnosis of arrhythmogenic right ventricular cardiomyopathy

This study evaluated the diagnostic significance of a magnetic resonance imaging (MRI) based scoring model for identification of arrhythmogenic right ventricular cardiomyopathy (ARVC) in patients with MRI evidence of RV abnormalities. Fifty-three patients with RV myocardial abnormalities on MRI were divided into a group with ARVC 1 (n=17) and a group with other RV arrhythmias (n=37). Decision tree learning (DTL) and linear classification (based on a modified ARVC scoring model of major and minor criteria) were used to identify and assess MRI criterion information value, and to induce ARVC diagnostic rules. All major ARVC criteria were more frequent in the ARVC group. Among minor criteria regional RV hypokinesia, mild segmental RV dilatation, and prominent trabeculae were more frequent in the ARVC group while mild global RV dilatation was more frequent in the non-ARVC group. RV aneurysm achieved highest importance in ARVC diagnosis (predictive accuracy 76.8%). Better diagnostic accuracy (sensitivity 93.3%, specificity 89.5%) was achieved when the MRI score for the major and minor criteria reached threshold value of four: two major criteria, or one major and two minor, or four minor criteria. Combinations between major and minor criteria contributed to a statistically valid model for ARVC diagnosis.

One-year outcome after radiofrequency catheter ablation of symptomatic ventricular arrhythmia from right ventricular outflow tract

Although ventricular premature complexes (VPCs) in patients without structural heart disease are benign, many patients experience disabling symptoms. Many patients need long-term medication, which is often ineffective and may have adverse effects. Radiofrequency catheter ablation (RFCA) may be an alternative treatment. RFCA was performed in 33 patients with severely symptomatic VPCs that were refractory to medication. Mean VPCs were 23,987 +/- 2,077 beats/24 hours. Twenty-four-hour ambulatory electrocardiographic monitoring, quality of life, and symptoms were assessed at a screening visit and 1 and 12 months after RFCA. RFCA was successfully performed in 32 patients (97%). This resulted in a significant improvement in symptoms, severity of ventricular arrhythmia, and quality of life at 1 and 12 months after the procedure. There were no major complications related to the procedure. Eight patients (24%) had residual arrhythmia. Five of them underwent repeated ablation with successful results. Thus, catheter ablation is a safe and effective treatment for symptomatic ventricular arrhythmia from the right ventricular outflow tract. It also improves the quality of life. Catheter ablation is a viable alternative to drugs in the presence of disabling symptoms.

Diagnosis of arrhythmogenic right ventricular dysplasia: a review

Arrhythmogenic right ventricular dysplasia (ARVD) is a myocardial disorder of primarily the right ventricle, with unknown cause and prevalence and with a frequent familial occurrence. The typical clinical manifestation consists of ventricular arrhythmias with a left bundle branch block (LBBB) pattern that occur predominantly in young adults. ARVD may result in sudden death. Other manifestations are electrocardiographic repolarization and depolarization changes, structural abnormalities that range from subtle wall aneurysms within the so-called "triangle of dysplasia" to biventricular regional or global dysfunction, and localized or widespread fibrofatty infiltration of the right ventricular myocardium. The diagnosis of ARVD is based on the presence of major and minor criteria encompassing genetic, electrocardiographic, pathophysiologic, and histopathologic factors. The imaging modalities used to evaluate right ventricular abnormalities include conventional angiography, echocardiography, radionuclide angiography, ultrafast computed tomography, and magnetic resonance (MR) imaging. Among these techniques, MR imaging allows the clearest visualization of the heart. Because MR imaging depicts both functional and structural abnormalities, positive MR imaging findings should be used as important additional criteria in the clinical diagnosis of ARVD. MR imaging appears to be the optimal technique for detection and follow-up of clinically suspected ARVD.

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.

Clinical characteristics and catheter ablation of left ventricular outflow tract tachycardia

Left ventricular outflow tract (LVOT) tachycardia is an uncommon form of idiopathic ventricular tachycardia (IVT). The underlying mechanism of this arrhythmia appears to be cyclic AMP-medicated triggered activity. The tachycardia occurs in the absence of structural heart disease and is generally benign, presenting commonly as palpitations and presyncope. It can manifest either a right or left bundle branch block morphology with an inferior axis. Subtle variations in the QRS morphology in leads I, V1, and V2 can help in localizing the anatomic site of origin (SOO). The arrhythmia is typically responsive to a variety of pharmacologic agents (beta-blockers, calcium channel blockers, Class I and II agents). Radiofrequency catheter ablation of LVOT tachycardia SOO as determined by pace mapping is quite efficacious (success rates of 90%). Magnetic electroanatomic mapping augments this by permitting three-dimensional catheter mapping and reproducible localization of the SOO. Catheter ablation should be considered relatively early in patients who experience severe symptoms with their arrhythmia and have failed, or are reluctant to take medications for the disorder.

Ventricular arrhythmias in normal hearts

Idiopathic ventricular tachycardia (VT) is characterized by two predominant forms. The most common form originates from the right ventricular outflow tract and presents as repetitive monomorphic VT or exercise-induced VT. The tachycardia is adenosine sensitive and is thought to be because of cAMP-mediated triggered activity. The other major form of idiopathic VT is owing to verapamil-sensitive intrafascicular re-entrant tachycardia, which most often originates in the region of the left posterior fascicle. Both forms of idiopathic VT can be readily treated with radiofrequency catheter ablation.

Ventricular tachycardia in an adolescent with arrhythmogenic right ventricular dysplasia

We report the case of an adolescent boy with exertional syncope and ventricular tachycardia caused by arrhythmogenic right ventricular dysplasia. Diagnosis was determined by transthoracic echocardiography and definitive management with an automatic internal cardiac defibrillator. Emergency physicians must be aware of this serious but treatable cause of adolescent exertional syncope.

Unusual features of right and left idiopathic ventricular tachycardia abolished by radiofrequency catheter ablation

Two unusual cases are presented with idiopathic right and left ventricular tachycardia (IVT) with intriguing clinical and electrophysiological characteristics. The first patient with a sustained IVT of right ventricular outflow tract origin, and an electrophysiological mechanism suggesting reentry, had been resuscitated from cardiac arrest. The second patient had an IVT with a left bundle branch block morphology, which originated from the basal-septal region of the left ventricle (left ventricular outflow tract tachycardia). Both patients were cured with radiofrequency catheter ablation, guided by endocardial activation sequence and pace mapping.

Idiopathic right ventricular outflow tract tachycardia: a clinical approach

Right ventricular outflow tract (RVOT) tachycardia is the most common form of idiopathic ventricular tachycardia (VT). Phenotypically, RVOT tachycardia segregates into two predominant forms, one characterized by repetitive monomorphic nonsustained VT and the other by paroxysmal exercise induced sustained VT. There is an increasing body of evidence to support the concept that both forms of tachycardia reflect disparate clinical manifestations of an identical cellular mechanism (i.e., cAMP-mediated triggered activity), which is identified clinically by the tachycardia's sensitivity to adenosine. The clinical characteristics, natural history, and approaches to therapy of RVOT tachycardia are delineated herein.

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.

Value of quantitative measurement of signal-averaged electrocardiographic variables in arrhythmogenic right ventricular dysplasia: correlation with echocardiographic right ventricular cavity dimensions

OBJECTIVES

We sought to investigate the relation between signal-averaged electrocardiographic (ECG) variables and the extent of right ventricular disease, as estimated by right ventricular enlargement during detailed echocardiography, in patients with arrhythmogenic right ventricular dysplasia.

BACKGROUND

In patients with ventricular tachycardia of right ventricular origin, a normal signal-averaged ECG is indicative of "idiopathic" ventricular tachycardia, whereas an abnormal signal-averaged ECG is a specific marker for right ventricular disease, especially dysplasia. Signal-averaged ECGs in these patients are mildly to grossly abnormal.

METHODS

Ten patients with the clinical diagnosis of arrhythmogenic right ventricular dysplasia were included. All patients had documented, sustained ventricular tachycardia, no coronary artery disease and a normal QRS duration of < or = 110 ms on routine 12-lead electrocardiography. Signal-averaged ECGs were recorded using time-domain analysis. Right ventricular cavity dimensions recorded during two-dimensional echocardiography were measured at the level of the inflow tract, midcavity and outflow tract. Signal-averaged ECG variables and echocardiographic measurements were correlated using linear regression analysis.

RESULTS

Nine of 10 patients had abnormal signal-averaged ECGs. There was a consistent correlation between all signal-averaged ECG variables and the right ventricular cavity dimensions at the level of the midcavity. The correlation was most significant with the duration of the filtered QRS complex (p < 0.001 for QRS duration, p < 0.01 for late potential duration and p < 0.05 for root-mean-square voltage of the last 40 ms). There was no consistent correlation between the signal-averaged ECG variables and right ventricular dimensions at the level of the inflow and outflow tracts.

CONCLUSIONS

The majority of patients with arrhythmogenic right ventricular dysplasia have abnormal signal-averaged ECGs. In the absence of bundle branch block, the extent of abnormality of signal-averaged ECG variables is in proportion to right ventricular cavity enlargement, and thus is indicative of the severity of right ventricular dysfunction.

Radiofrequency ablation of idiopathic ventricular tachycardia

BACKGROUND

Radiofrequency ablation (RFA) has been shown to be very effective in the treatment of supraventricular tachycardias and has replaced surgical ablation. Only a few reports of RFA for idiopathic ventricular tachycardia (VT) have appeared in the literature during the last two years.

AIM

This paper presents our experience with RFA for idiopathic VT in 19 patients.

MATERIAL

The age range of patients was 22-60, with a mean of 37.9 years. Twelve out of 19 were females, two patients had cardiac failure due to almost incessant VT while the rest had normal left ventricular function. Twelve patients had VT arising from the right ventricle (RV); of these, nine were from the outflow tract, two from the RV apex, and one from the mid-anterior RV. Seven patients had VT arising from the left ventricle (LV); of these, five were from the inferobasal portion of the septum and two were from the anterolateral area.

METHODS

In all patients the diagnostic study and therapeutic RFA were combined in a single procedure. Pacemapping was used to guide the site of RFA in patients with VT arising from the RV. Local activation time (LAT), Purkinje potentials (PP) and pacemapping were used to guide RFA in those patients with LV septal tachycardias.

RESULTS

A total of 21 RF procedures were performed in 19 patients and 15 out of 19 patients had successful VT ablation. Ten of the 12 patients with RV tachycardias and all five patients with LV septal (left axis, right bundle branch block) tachycardias were successfully ablated. One patient with mid anterior RV VT required two attempts for successful ablation. One patient with RV outflow tract (RVOT) VT could not be ablated despite two attempts. Two patients with LV tachycardias arising from the antero-lateral LV could also not be ablated. During a follow up period of two to 16 months none of the successful patients had recurrence of VT. The number of RF applications was one to 27, mean 10; fluoroscopy times were four to 75, mean 26.9 minutes.

CONCLUSION

Idiopathic VT frequently arises from the RVOT and inferobasal portion of the LV septum. These tachycardias can be diagnosed on clinical and ECG grounds. RFA for idiopathic VT arising from these areas has a high success rate and this mode of treatment should be considered as a nonpharmacological curative treatment for symptomatic patients.

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.