Sympathovagal Balance Prior to Onset of Repetitive Monomorphic Idiopathic Ventricular Tachycardia

Repetitive monomorphic idiopathic (RMI) ventricular tachycardia (VT) occurs typically in patients without structural heart disease, originates in most cases from the right ventricular outflow tract, and can often be induced by exercise or isoproterenol. This study analyzed the dynamic changes in autonomic tone immediately before the spontaneous onset of RMIVT using frequency-domain heart rate variability (HRV) indices. We analyzed the ambulatory electrocardiographic recordings from 6 men and 8 women (mean age: 43 ± 18 years; mean number of VT runs per day: 134 ± 213; mean VT rate: 194 ± 40 bpm; median VT run length: 4 cycles) with RMIVT. A total of 36 clusters of nonsustained episodes of RMIVT preceded by ≥1 hour of sinus rhythm without VT were analyzed (25 minutes before the onset of RMIVT divided into five 5-minute periods; 8 minutes before onset of RIMVT divided into eight 1-minute periods). During 25 minutes preceding the onset of VT, the mean RR interval decreased from 767 ± 118 to 723 ± 105 ms (P = 0.015) and the low-frequency (LF)/high-frequency (HF) ratio increased from 2.24 ± 0.79 to 2.49 ± 1.0 (P = 0.03). During the 8 minutes before VT onset, the mean RR interval decreased from 745 ± 118 to 718 ± 102 ms (P = 0.001) and the LF components increased from 205 ± 72 to 253 ± 113 ms (P = 0.014). No change in HF components was observed during the 25 or 8 minutes periods preceding the RMIVT onset. The changes in HRV indices suggest a strong time-dependent primary activation of sympathetic tone prior to the occurrence of RMIVT. Withdrawal of vagal tone does not appear essential to the initiation of RMIVT clusters.     

Edrophonium-Induced Right Ventricular Outflow Tract Tachycardia

Idiopathic right ventricular outflow tract-ventricular tachycardia (RVOT-VT) generally occurs when sympathetic nervous system activity is increased, though, in a few patients, it develops when parasympathetic nervous activity (PNA) is increased. Among 101 consecutive patients with RVOT-VT confirmed by endocardial catheter mapping, 5 (4.9%) presented with nocturnal RVOT-VT. Autonomic nervous balance was studied by heart rate variability (HRV) analysis from 24-hour ambulatory electrocardiogram (ECG). Standard programmed ventricular stimulation (PVS), ventricular burst pacing, and drug provocation were performed to induce RVOT-VT. In the studied five patients, the average number of mostly nocturnal ventricular premature contractions (VPCs) was 6649 ± 4472/day. Two patients had nocturnal nonsustained RVOT-VT on 24-hour ambulatory ECG recordings. The HRV analysis revealed that a progressive increase in high-frequency power coincided with an increase in VPCs or development of RVOT-VT at night, whereas low/high frequency ratio did not change significantly during the 24-hour period. RVOT-VT could not be induced by PVS, ventricular burst pacing, or isoproterenol or adenosine triphosphate i.v. However, RVOT-VT could only be induced by edrophonium, 5 mg i.v., in all patients. An increase in PNA was observed in a few patients before the development of RVOT-VT. Edrophonium facilitated induction of RVOT-VT in such patients.     

Morphological Variation of Nonreentrant Idiopathic Ventricular Tachycardia Originating from the Right Ventricular Outflow Tract and Effect of Radiofrequency Lesion

RF catheter ablation was performed in 16 patients with nonreentrant idiopathic VT originating from the RVOT. All documented VT was monomorphic, but subtle morphological variation in the VT-QRS complex was observed in 10 (63%) of 16 patients. Through endocardial mapping, VT origin was determined within a narrow site (< 0.5 ± 0.5 cm) in 4 of the 10 patients with the morphological variation. In the other 6 of 10 patients, the origin extended to an area of > 0.5 ± 0.5 cm. In VT with morphological variation, the local electrogram at the site of VT origin also showed variation in morphology and activation sequence. For VT of narrow origin, RF application to the site eliminated the VT. However, in VT from a wide arrhythmogenic area, RF current had to be delivered to 3–7 distinct sites to cover the possible origin, and specific QRS configuration of VT and/or PVC was ablated at each of the earliest activation site. All but one VT were successfully ablated by RF current. Subtle morphological variation was frequent in this type of VT, and about half were associated with a wide arrhythmogenic area. Precise mapping and analysis of the efficacy of each BF application might be helpful to better understand the relationship between subtle changes of VT-QRS morphology and their origins.     

Repetitive Ventricular Responses Induced by Radiofrequency Ablation for Idiopathic Ventricular Tachycardia Originating from the Outflow Tract of the Right Ventricle

In 23 consecutive patients, radiofrequency (RF) ablation was used as treatment for idiopathic ventricular tachycardia (VT) originating from the outflow tract of the right ventricle. In this study, we focused on the repetitive ventricular response (> 5 consecutive QRS beats during RF application). The incidence and clinical implications of the repetitive ventricular response were examined through the results of endocardial mapping and RF ablation. VT origin was mapped as the earliest activation site during VT, and it was determined within 0.5 × 0.5 cm (narrow site) in 13 patients and wider than 0.5 × 0.5 cm (wide origin) in the other 10 patients. The repetitive ventricular response was induced during application of RF current in 14 of 23 patients (61%), and it was more frequently observed in VT from a wide origin (100%) than in the VT from a narrow site (31%). The QRS morphology of the repetitive ventricular response was identical to that of clinical VT. As RF application was continued and/or repeated, the RR interval of the repetitive ventricular response was gradually prolonged, the number of consecutive QRS complexes was decreased, and clinical VT was finally eliminated. The overall success rate of RF ablation was 96% (22/23 patients), and no complications were observed. In conclusion, a repetitive ventricular response was frequently observed in idiopathic right VT. The changing pattern of repetitive ventricular response, slowing, and/or disappearing was consistent with successful RF ablation.     

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 nonsustainnd 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.     

Distribution of Successful Ablation Sites of Idiopathic Right Ventricular Outflow Tract Tachycardia

Background: There are few studies evaluating the distribution of successful ablation sites of idiopathic right ventricular outflow tract (RVOT) arrhythmias using a three-dimensional electroanatomical mapping system. This study aims to clarify the favorite site of idiopathic RVOT arrhythmias through electroanatomical voltage mapping using the CARTO system (Biosense Webster, Diamond Bar, CA, USA).
Methods: A consecutive series of 72 patients (mean age 43.6 ± 16.2 years, 32 males) who underwent radiofrequency catheter ablation (RFCA) for a total of 82 morphologies of idiopathic RVOT arrhythmias were studied. Detailed three-dimensional electroanatomical voltage maps of the RVOT were obtained using the CARTO system prior to the RFCA during sinus rhythm. The voltage on bipolar electrogram was defined as follows: amplitude < 0.5 mV as "low-voltage zone," amplitude between 0.5 and 1.5 mV as "transitional-voltage zone," and amplitude >1.5 mV as "high-voltage zone." Successful ablation sites were electroanatomically classified into each voltage zone.
Results: Successful ablation was acquired in 63 patients and 71 RVOT arrhythmias (63/72 patients: 87.5%, 71/82 RVOT arrhythmias: 86.5%). In the successful group, three arrhythmias (4.2%) were classified in the low-voltage zone, 63 arrhythmias (88.7%) in the transitional-voltage zone, and five arrhythmias (7.0%) in the high-voltage zone.
Conclusions: This study indicates that the vast majority of successful ablation sites for idiopathic RVOT arrhythmias are located in the transitional-voltage zone. Mapping of the transitional-voltage zone may be an important landmark of RFCA for RVOT arrhythmia.     

Catheter Ablation for Ventricular Tachycardia from a Diverticulum at the Right Ventricular Outflow Tract

A case is presented of a 73-year-old man with drug resistant ventricular tachycardia that originated from the right ventricular outflow tract. A right ventriculogram showed a diverticulum in the interventricular septum at the right ventricular outflow tract. Low energy radiofrequency catheter ablation within the diverticulum was performed successfully and safely.     

Relationship Between Spectral Measures of Heart Rate Variability and Ventricular Ectopic Activity in Patients with Idiopathic Ventricular Tachycardia

This study examines the relationship of hourly spectral measures of heart rate variability (HRV) to the occurrence of ventricular ectopic (VE) activity in 20 patients with idiopathic ventricular tachycardia and frequent VE's. Spectral measures of HRV were obtained from 24-hour Holler recordings from the patients in a drug free state and included the total energies in the spectrum, the low frequency components (1) (0.04–0.15 Hz) representing predominantly sympathetic lone with some contribution from the parasympathetic and high frequency components (H) (0. 15–0.4 Hz) representing mainly parasympathetic tone. A high H component (parasympathetic) was defined as area > 12 msec and high L components (sympathetic) as area > 30 msec. On an hourly analysis of spectral components in relation to VE activity, VE's occurred significantly more frequently during periods of low H and low L (F = 20.5, DF = 3, P < 0.0001). The number of VE's did not differ statistically in the other combinations of H and L components flow H, low L = 612.8 (50.1); high H, low L = 180.1 (36.8); low H, high L = 338.4 (58.9); high H, high L - 204.9 (17.7) VE's/hr (SEM). The results suggest that VE's are more frequent during periods of low H and low L and are diminished when either H or L are increased in patients with idiopathic ventricular tachycardia. The results would be consistent with the hypothesis that the parasympathetic nervous system has an electro physiologically stabilizing effect on the myocardium.     

Reentrant Ventricular Outflow Tract Tachycardia Arising from Focal Scar Detected by Delayed Enhancement Magnetic Resonance Imaging

A 58‐year‐old man was referred to our emergency room with hemodynamically unstable sustained ventricular tachycardia (VT). The morphology of the VT exhibited a left bundle branch block and inferior axis deviation. He had no past history of cardiovascular disease. Echocardiography, cardiac catheterization, cardiac biopsy, gallium scintigram, myocardial scintigram, T1,T2‐weighted magnetic resonance imaging (MRI), and gadolinium‐enhanced cine MRI did not detect any structural heart disease or abnormal cardiac function. However, delayed‐enhancement MRI (DE‐MRI) detected a focal intramural scar within the septal ventricular outflow tract. An electrophysiological study revealed a sustained VT with several morphologies and the entrainment phenomenon. Radiofrequency catheter ablation to the site corresponding to the focal scar detected by DE‐MRI successfully eliminated the VT. (PACE 2012;35:e349–e352)     

Ventricular Fibrillation Triggered during and after Radiofrequency Energy Delivery to the Site of Origin of Idiopathic Right Ventricular Outflow Tract Arrhythmia

We observed a case of idiopathic ventricular arrhythmias originating from the right ventricular outflow tract (RVOT). The origin of target premature ventricular contraction (PVC) and nonsustained ventricular tachycardia (VT) was within a wide low‐voltage area around the RVOT. During radiofrequency (RF) application to the site of arrhythmia origin, polymorphic VT and ventricular fibrillation were repeatedly triggered by new PVC that had developed near the site of ablation. This electrical storm persisted >30 minutes after cessation of RF current delivery, and was suppressed by additional RF applications to the site of origin of the new PVC.     

Radiofrequency Catheter Ablation of Symptomatic Ventricular Ectopic Beats Originating in the Right Outflow Tract

Ectopic activity originating in the right ventricular outflow tract is a frequent finding and may result in severe symptoms such as dyspnea, palpitations, and lack of physical capacity correlated with a low cardiac output. In 12 consecutive symptomatic and drug refractory patients, we performed a study with intracardiac mapping and ablation procedure. The origin of the ectopic beats was identified, and the ablation procedure was performed. Patients were examined by serial ECG, Holter ECG, bicycle ECG, echocardiography, and thoracic X ray. At baseline, the mean number of ectopic beats was 23,823 during Holter ECG. No other arrhythmias were present. Patients underwent basic electrophysiological study, mapping process, and ablation in a single procedure. Ablation was performed with a deflectable thermocoupled catheter with tip electrodes of 4 mm. Criteria for identification of the origin of the ectopic beats included pace mapping with 12 leads and earliest endocardial activation. One male patient suffered from myocarditis; the other 11 patients had no underlying structural heart disease. The mean age was 38 years. Ablation procedure with delivered temperature of 70 °C was successful in 11 of 12 patients eliminating the focus. The mean procedural time was 79± 34 minutes; mean fluoroscopy time was 13.8± 8.8 minutes; and mean number of applications was 4.4± 2.8. No adverse effects occurred during a follow-up period of 10 months after ablation. The mean number of ectopic beats per 24 hours after ablation was 317 ± 599 with a P value of 0.00024. The clinical symptoms improved in all but one patient. One patient had a recurrence after 2 months that could be successfully treated by a second procedure. In our experience, temperature guided radiofrequency catheter ablation is safe and effective for the treatment of patients with symptomatic ectopic activity of the right outflow tract. As long as we lack the experience of a greater patient cohort and a longer follow-up, only drug resistant and highly symptomatic patients should be selected.     

Right Ventricular Outflow Tract Tachycardia as a Result of Blunt Chest Trauma

Two patients presented with monomorphic ventricular tachycardia after blunt chest trauma. In both cases, the arrhythmia had a left bundle branch block, inferior axis morphology comparable to that seen with idiopathic ventricular tachycardia originating from the right ventricular outflow tract (RVOT). In one patient, the arrhythmia persisted and required catheter ablation. A history of cardiac trauma should be considered in patients presenting with RVOT tachycardia.     

Automated Template Matching to Pinpoint the Origin of Right Ventricular Outflow Tract Tachycardia

Background: Template matching, a technique that examines the similarity between two QRS complexes, has not been broadly applied clinically.
Methods: The 16 patients enrolled in this study underwent radiofrequency catheter ablation (RFCA) at the site of five ventricular tachycardias (VT) and of premature ventricular contractions (PVC) arising from 25 sites in the right ventricular outflow tract (RVOT), under the guidance of conventional pace and activation mapping. After RFCA, (a) a template-matching score using a correlation coefficient, and (b) a pace-map score were calculated at 30 successful and 48 unsuccessful ablation sites.
Results: The template-matching score at successful ablation sites (94 ± 4%) was significantly higher than at unsuccessful (85 ± 9%) ablation sites (P < 0.001). A ≥ 90% average matching score identified successful ablation sites with a sensitivity of 90% and specificity of 69%. While there was a significant correlation between the template-matching score and visually judged pace-map score (r = 0.63, P < 0.0001), the area under the receiver operating characteristic curve of the template matching score was larger than that of the pace-map score (0.80 vs. 0.67).
Conclusions: Automated template matching was useful for localizing the optimal ablation site during RFCA of RVOT-VT/PVC.     

Interplay between Arrhythmias Originating in the Right Ventricular Outflow Tract and the Left Coronary Cusp

A 35‐year‐old man was referred for ablation of ventricular tachycardia with two different morphologies triggering each other. After elimination of the first arrhythmia in the right ventricular outflow tract, ablation of the second morphology was performed 8 mm below the left main stem after contrast injection into the left coronary cusp through the irrigated‐tip ablation catheter. (PACE 2012;35:e356–e357)     

Early Afterdepolarizations in a Patient with Idiopathic Monomorphic Right Ventricular Tachycardia

To identify the role of afterdepolarizations in the induction of idiopathic monomorphic right ventricular tachycardia (VT), monophasic action potentials (MAPs) were recorded in a patient with this type of VT. The VT had a left bundle branch block configuration and inferior axis, and originated in the right ventricular outflow tract (RVOT). MAPs were recorded with a contact electrode at the origin of the VT, as well as other ventricular sites. The VT was induced by the intravenous administration of isoproterenol and/or rapid ventricular pacing and was preceded by short-long-short sequences of RR intervals. Early afterdepolarizations (EADs) in MAPs were recorded at the origin of VT (RVOT), but not recorded at other ventricular sites. These data suggest that catecholamine sensitive triggered activity seems to be the mechanism of idiopathic monomorphic right VT and EADs can be recorded in association with the occurrence of this type of VT.     

Idiopathic Ventricular Tachycardia Originating from the Left Ventricle Near the His Bundle

A 62‐year‐old man with idiopathic ventricular tachycardia (VT) exhibiting left bundle branch block and left inferior axis QRS morphology with a Qr in lead III underwent electrophysiological testing. Successful ablation was achieved in the left ventricle (LV) at a site with an excellent pace map, adjacent to the His bundle electrogram recording site. At that site, the sequence of the ventricular electrogram and late potential recorded during sinus rhythm reversed during spontaneous premature ventricular contractions with the same QRS morphology as the VT. This case shows that VT can arise from the LV ostium adjacent to the membranous septum. (PACE 2010; 33:e114–e118)     

Value of Heart Rate Variability to Predict Ventricular Arrhythmias in Recipients of Prophylactic Defibrillators with Idiopathic Dilated Cardiomyopathy

GRIMM, W., et al. : Value of Heart Rate Variability to Predict Ventricular Arrhythmias in Recipients of Prophylactic Defibrillators with Idiopathic Dilated Cardiomyopathy. This study investigated the relation between heart rate variability (HRV) measured as standard deviation of normal to normal RR intervals (SDNN) on baseline 24-hour ambulatory electrocardiogram (ECG) and subsequent appropriate implantable cardioverter defibrillator (ICD) interventions in 70 patients with idiopathic dilated cardiomyopathy (IDC) in whom ICDs were implanted prophylactically in the presence of a low left ventricular ejection fraction (LVEF). During   43 ± 26   months of follow-up, 26 of 70 (37%) study patients with IDC received one or more appropriate ICD interventions for sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) documented by electrograms stored in the ICD. Mean SDNN at ICD implant was   94 ± 33 ms   . No difference was found between patients with   (90 ± 25 ms)   versus without   (96 ± 37 ms)   appropriate ICD interventions for VT or VF during follow-up. Multivariate Cox regression analysis of baseline clinical characteristics including age, gender, LVEF, NYHA functional class, nonsustained VT on Holter, history of syncope, left bundle branch block, baseline medication and HRV revealed LVEF as the only significant predictor of arrhythmia. These findings do not support the use of HRV measured as SDNN on 24-hour ambulatory ECG to select patients with IDC for prophylactic ICD therapy. (PACE 2003; 26[Pt. II]:411–415)