Right Ventricular Outflow Tract Group Research Articles

Electrocardiographic criteria for localization of ventricular premature complexes from the inferior right ventricular outflow tract.

BackgroundThe ventricular premature complexes (PVCs) originating from the superior right ventricular outflow tract (RVOT) have high success rates by catheter ablation. It may not be the same when the origin is in the inferior RVOT.ObjectiveTo identify electrocardiographic (ECG) characteristics that predict the site for successful ablation of PVCs originating in the inferior RVOT.MethodsOf 309 consecutive patients with symptomatic PVCs despite medical therapy, 124 had PVCs originating from the RVOT, and 107 RVOT cases without structural heart disease and no bundle branch block in sinus rhythm were enrolled in the study. Among them, 74 have a superior RVOT origin, and 33 have an inferior RVOT origin.ResultsThe proportion with multiple morphologies of PVC was significantly higher in the inferior RVOT group than in the superior RVOT group (24.24 vs. 6.76%, P = 0.011). The QRS duration of PVCs with an inferior RVOT origin was more expansive than PVCs with a superior RVOT origin (162.42 ± 19.69 ms vs. 140.90 ± 11.30 ms; P < 0.001). Furthermore, the QRS wave in V1 in patients in the inferior RVOT group was more likely to have a negative delta wave at the onset of the QRS (27.27 vs. 1.39%, P < 0.001). We found that the areas under the receiver-operating characteristic curve (AUCs) for PVC diagnosis with an inferior RVOT origin ranged from 0.812 to 0.841 depending on ECG features, with the highest AUC for the QRS duration of PVCs and the amplitude of R waves in lead II. These ECG indices had good predictability for judging the origin of PVCs in the RVOT; the best threshold for the QRS duration of PVCs was 145 ms, and the best thresholds for the amplitude of R waves in leads II, III, and aVF were 1.35, 1.35, and 1.15 mV, respectively.ConclusionWhen evaluating a patient with PVCs, the source is likely to be the inferior RVOT if the ECG presentation conforms to the morphological characteristics of the RVOT, meanwhile, the QRS wave is relatively broad and polymorphic, and the main waves in limb leads (II, III, and aVF) are upward with low amplitude.

Different expressions of cardiac biomarkers between different types of acquired right ventricular outflow tract abnormality in monochorionic twins.

To investigate the differences in amniotic fluid cardiac biomarkers and clinical features among types of right ventricular outflow tract (RVOT) abnormality in monochorionic (MC) twins. This prospective study included MC twins that underwent laser surgery. Recipient or larger twins (group A) and donor or smaller twins (group B) were assessed and divided into those with a normal right ventricular outflow tract (normal RVOT), functional pulmonary atresia (fPA), or pulmonary stenosis (PS). Amniotic fluid levels of NT-proBNP (afNT-proBNP) and cardiac troponin T (afTnT) were examined during surgery. Of 190 fetuses in group A, there were 14 RVOT abnormality cases (including 7 fPA and 7 PS). No group B fetuses showed RVOT abnormality findings. In group A, later and earlier gestational age at surgery were observed in fPA (25.1±2.8weeks) and PS groups (17.8±0.9weeks). All survived PS cases demonstrated progressive pulmonary valve obstruction, not observed in fPA groups. AfNT-proBNP were significantly higher in fPA and PS than in the normal RVOT group (p<0.05). AfTnT was significantly higher in group A with PS than fPA and normal RVOT groups (p<0.05). Among RVOT abnormality types in group A, amniotic fluid cardiac biomarkers were differently expressed, and clinical features were also differentiated. These findings provide insight into the pathophysiological influence on RVOT in MC twins. This study was registered with the Japanese Clinical Trial Registry "UMIN-CTR" (http://www.umin.ac.jp/ctr/index-j.htm; trial ID numbers UMIN000024486 and 000037702).

Validation of an electrocardiographic marker of low voltage areas in the right ventricular outflow tract in patients with idiopathic ventricular arrhythmias.

Previous studies have reported the presence of subtle abnormalities in the right ventricular outflow tract (RVOT) in patients with apparently normal hearts and ventricular arrhythmias (VAs) from the RVOT, including the presence of low voltage areas (LVAs). This LVAs seem to be associated with the presence of ST-segment elevation in V1 or V2 leads at the level of the 2nd intercostal space (ICS). Our aim was to validate an electrocardiographic marker of LVAs in the RVOT in patients with idiopathic outflow tract VAs. A total of 120 patients were studied, 84 patients referred for ablation of idiopathic VAs with an inferior axis by the same operator, and a control group of 36 patients without VAs. Structural heart disease including arrhythmogenic right ventricular cardiomyopathy was ruled out in all patients. An electrocardiogram was performed with V1-V2 at the 2nd ICS, and ST-segment elevation ≥1 mm and T-wave inversion beyond V1 were assessed. Bipolar voltage map of the RVOT was performed in sinus rhythm (0.5-1.5 mV color display). Areas with electrograms <1.5 mV were considered LVAs, and their presence was assessed. We compared three groups, VAs from the RVOT (n = 66), VAs from the LVOT (n = 18) and Control group (n = 36). ST-elevation, T-wave inversion and left versus right side of the VAs were tested as predictors of LVAs, respective odds ratio (ORs) (95% confidence interval [CI]) and p values, were calculated with univariate logist regression. Variables with a p < .005 were included in the multivariate analysis. ST-segment elevation, T-wave inversion and LVAs were present in the RVOT group, LVOT group and Control group as follows: (62%, 17%, and 6%, p < .0001), (33%, 29%, and 0%, p = .001) and (62%, 25%, and 14%, p < .0001). The ST-segment elevation, T-wave inversion and right-sided VAs were all predictors of LVAs, respective unadjusted ORs (95% CI), p values were, 32.31 (11.33-92.13), p < .0001, 4.137 (1.615-10.60), p = .003 and 8.200 (3.309-20.32), p < .0001. After adjustment, the only independent predictor of LVAs was the ST-segment elevation, with an adjusted OR (95% CI) of 20.94 (6.787-64.61), p < .0001. LVAs were frequently present in patients with idiopathic VAs. ST-segment elevation was the only independent predictor of their presence.

Different response to vitamin D supplementation of PVCs from RVOT and non-outflow tract RV regions

Abstract Background Recent publications have shown that premature ventricular contractions (PVCs)_ from the right ventricular outflow tract (RVOT) have a good response to vitamin D supplementation in patients that have a vitamin D deficiency. Purpose The present study aimed to compare the response to vitamin D supplementation of of 2 types of PVCs: from RVOT and from other RV areas outside RVOT Methods Our study included 16 patients from the Outpatient Clinic of the Rehabilitation Hospital, of whom all had vitamin D deficiency. Four patients had high PVC burden with an RV morphology other than RVOT and were matched 1:3 for age and sex with 12 patients with high PVC burden and RVOT morphology. Results Mean age was 26 years in both group and 33% were females. The mean 25-OH vitamin D value was 17.7±2.9 ng/ml in the non RVOT group and 21.6±5.3 ng/ml in the RVOT group. After 3±1.7 month of treatment with 2000–5000 U/day, 25 OH vitamin D increased to. 31.1±3.2. in the non-RVOT group and to 35.9±5.1 in the RVOT group. After treatment PVC burden decreased from 19956±2618 to 19399±3015 (NS) in the non-RVOT group and from 21057±9594 to 4249±2835 (p=0.0001) in the RVOT group. Conclusions After 3 months of vitamin D supplementation in patients with high burden PVC and vitamin D deficiency, the burden decreased significantly by more than 75% in the RVOT morphology group but not in the non- RVOT morphology group. Funding Acknowledgement Type of funding sources: None. PVC burden in the non RVOT groupPVC burden in the RVOT group

Modified Precordial Lead R-Wave Deflection Interval Predicts Left- and Right-Sided Idiopathic Outflow Tract Ventricular Arrhythmias.

This study evaluated if modifying electrocardiographic (ECG) precordial leads to a higher intercostal position improved the accuracy of outflow tract ventricular arrhythmia (OTVA) localization. Precordial ECG prediction algorithms that use a standard lead configuration localize OTVA with variable accuracy. Patients who underwent OTVA ablation were prospectively enrolled to have a standard and modified (high) precordial ECG. R- and S-wave amplitudes and intervals were measured to develop an algorithm that differentiated the right ventricular outflow tract (RVOT) and the left ventricular outflow tract (LVOT) with high accuracy-the modified lead R-wave deflection interval (RWDI). This interval was defined from the earliest QRS onset (using all modified leads) to the lead with longest R-wave deflection. The RWDI was compared with all other ECG algorithms. A total of 50 patients (38 women; mean age 51 ± 17 years) had successful catheter ablation for OTVA (RVOT 60%, LVOT 40%). The modified lead RWDI was significantly shorter in the RVOT group (18.5ms, interquartile range 25th to 75th percentile [IQR25-75]: 0 to 29.5ms) compared with the LVOT group (67.5ms, IQR25-75: 56.5 to 77ms; p<0.05). Using a RWDI≤40ms to predict an RVOT focus, the sensitivity and specificity of the modified lead RWDI were 100% and 95%, respectively; the area under the receiver-operating characteristic curve was 0.96. This was superior to all previously developed algorithms. In a computed tomography analysis (n=50), the modified leads were significantly closer to the outflow tracts compared with the standard precordial leads. The modified lead RWDI is a simple, easily interpretable algorithm that can potentially differentiate a right- or left-sided origin of OTVA with high accuracy.

Amplitude of QRS complex within initial 40 ms in V2 (V2QRSi40): Novel electrocardiographic criterion for predicting accurate localization of outflow tract ventricular arrhythmia origin

The initial depolarization vector of outflow tract (OT) ventricular arrhythmia (VA) varies in different origins, which may help to predict OT-VA origin more accurately. The purpose of this study was to develop a more accurate electrocardiographic (ECG) criterion for differentiating between left and right OT-VA origins. We studied 275 patients with successful ablation in the right ventricular outflow tract (RVOT) (n = 207) or left ventricular outflow tract (LVOT) (n = 68) in the development cohort. Amplitude of the QRS complex within initial 40 ms (QRSi40) in precordial leads was measured. A novel criterion for identifying OT-VA origin was developed based on the development cohort. Predictive performance of novel criterion was further validated by comparing with previous ECG criteria (V2S/V3R index, V2 transition ratio, and transition zone index) in the validation cohort with 107 patients (RVOT 75; LVOT 32). QRSi40 of identical precordial leads were significantly greater in the LVOT group than the RVOT group (P <.05). In the development cohort, QRSi40 of V2 (V2QRSi40) exhibited the greatest area under the curve of 0.950, with cutoff ≥0.52 mV predicting LVOT origin (sensitivity 86.0%; specificity 94.6%). In the validation cohort, V2QRSi40 ≥0.52 mV outperformed previous criteria in predictive performance (accuracy 90.7%; sensitivity 84.4%; specificity 93.3%). This advantage of V2QRSi40 over previous criteria also held true for subgroups of transition zone index = 0 and V3 R/S transition. V2QRSi40 is a novel and accurate ECG criterion to predict OT-VA origin that outperforms previous criteria.

Effect of radiofrequency on epicardial myocardium after ablation of ventricular arrhythmias from within coronary sinus.

Radiofrequency (RF) ablation of idiopathic ventricular arrhythmias (IVA) from the coronary venous system (CVS) has been increasingly performed, but real effect of ablation lesions from CVS on epicardial myocardium has not been studied. To compare effects of RF delivered inside the distal CVS during ablation of IVAs originating from left ventricular summit (LVS) with IVAs ablated from right ventricular outflow tract (RVOT) using cardiac magnetic resonance imaging (CMRI). Twenty consecutive patients with IVAs who underwent acutely successful RF ablation at initial appropriate sites, i.e., distal CVS (Group 1, n = 10) or RVOT (Group 2; n = 10) were enrolled. Detailed contrast-enhanced CMRI of each patient was performed 3 months later. Presence and location of scars, distance of CVS to epicardial ventricular myocardium were measured and analyzed. Group 1 consisted of 10 and Group 2 consisted of 10 patients. Three months after the ablation, only three patients in Group 1 had detectable late gadolinium enhancement (LGE) on CMRI while nine out of 10 patients in Group 2 had evident LGE on CMRI (P: 0.02). The mean distance of distal CVS to epicardial anterobasal myocardium was measured to be 8.8 ± 1.6mm in Group 1. In three cases that had detectable scar on superior anterobasal LV epicardium, the mean distance was 7.4 ± 1.1mm. RF delivery inside the CVS is less likely to produce detectable LGE on CMRI compared to RVOT. This may partially explain less than ideal long-term results after ablation of LVS IVAs from within the great cardiac vein/anterior interventricular vein.

Idiopathic ventricular arrhythmias originating from the right coronary sinus: Prevalence, electrocardiographic and electrophysiological characteristics, and catheter ablation

Ventricular arrhythmias (VAs) of the right coronary cusp (RCC) are not fully characterized. To investigate the electrocardiographic and electrophysiological characteristics, mapping and ablation of RCC-VAs. Among 256 consecutive patients undergoing electrophysiological evaluation and ablation of VAs of ventricular outflow tract origin, data were compared among 27 RCC-VAs, 50 VAs of the septal aspect of right ventricular outflow tract (RVOT), including from pulmonary artery, and 9 VAs of left coronary cusp (LCC). The only electrocardiographic characteristic that differentiated VAs originating from the RCC and RVOT was the amplitude of the R wave in lead I. During VAs of the RCC, the earliest activation site (EAS) in the right ventricle was localized in the middle-posterior septal region of the RVOT. The distance between the His bundle and the EAS in the RVOT in the RCC group was shorter than that in the RVOT and LCC group; the distance ≤ 29.4 mm, which rules out an RVOT and LCC origin, had 92.6% sensitivity and 100% specificity for RCC-origin speculation. Double or complex potentials were recorded in RVOT middle-posterior septal area surrounding the EAS in 20 of 27 RCC-VA patients (70%). Most of the successful ablation sites (24/27) were located in the anterior and upper margin of the RCC, close to the middle-posterior septal region of the RVOT. The prepotential (P1) amplitude and the P1-to-QRS complex interval may be indicators of successful RCC-VA ablation sites. RCC-VAs are not uncommon and have unique electrocardiographic and electrophysiological characteristics that distinguish an RCC origin of VA from RVOT and LCC origins. Most RCC-VAs were ablated successfully in the anterior and upper aspects of the RCC.

Assessment of left ventricular electromechanical activation during right ventricular apical and outflow tract pacing

Abstract Background Right ventricular (RV) apical pacing, induces asynchronous ventricular contraction and impairs cardiac function. Alternative sites of pacing particularly right ventricular outflow tract (RVOT) may have a more favorable hemodynamic profile, physiological left ventricular (LV) activation and normal ventricular contraction pattern. The Aim of the study was to find out the best alternative sites to RV apex for permanent pacemaker (PM) lead fixation in the RVOT, based on the width of the QRS in the surface ECG. Patients and methods The study included 69 patients with pacemaker-dependent complete heart block; 35 with active pacemaker lead fixation in the site which achieved narrowest max. QRS duration in the RVOT (group 1) and 34 with active pacemaker lead fixation in RV apex (group 2). Results High RVOT septum was the site which achieved the narrowest QRS duration on surface ECG (117.86 ± 8.43 ms) when compared with RV apex (140.29 ± 13.14) ( p p p Conclusion High RVOT septum is the ideal site for PM lead implantation. Compared with RV apical pacing, it is associated with improvement in functional and hemodynamic parameters over medium-term follow-up.

Comparison of left ventricular systolic function and mechanical dyssynchrony using equilibrium radionuclide angiography in patients with right ventricular outflow tract versus right ventricular apical pacing: A prospective single-center study

BackgroundChronic ventricular pacing is known to adversely affect left ventricular (LV) function. Studies comparing right ventricular outflow tract (RVOT) pacing with RV apical (RVA) pacing have shown heterogeneous outcomes. Our aim was to objectively assess LV function and mechanical dyssynchrony in patients with RVOT and RVA pacing using equilibrium radionuclide angiography (ERNA). MethodsFifty-one patients who underwent permanent pacemaker implantation and had normal LV function were prospectively included. Twenty-nine patients had pacemaker lead implanted in the RVOT and 22 at the RVA site. All patients underwent ERNA within 5 days post-pacemaker implantation and follow-up studies at 6 and 12 months. Standard deviation of LV mean phase angle (SD LV mPA) expressed in degrees, which was derived by Fourier first harmonic analysis of phase images, was used to quantify left intraventricular dyssynchrony. ResultsNo significant difference was observed between the two groups with respect to indication (P = .894), Type/mode (P = .985), and percentage of ventricular pacing (P = .352). Paced QRS duration was significantly longer in RVA group than RVOT group (P = .05). There was no statistically significant difference between the RVA and RVOT groups at baseline with respect to LVEF (P = .596) and SD LV mPA (P = .327). Within the RVA group, a significant decline in LVEF was observed over 12-month follow-up (from 57.3% ± 5.32% to 55.6% ± 6.25%; P = .012). In the RVOT group, the change in LVEF was not statistically significant (from 56.7% ± 4.08% to 54.3% ± 6.63%; P = .159). No significant change in SD LV mPA was observed over 12-month follow-up within the RVA group (from 10.5 ± 2.58° to 10.4 ± 3.54°; P = 1.000) as well as in the RVOT group (from 9.7 ± 3.28° to 9.4 ± 2.85°; P = .769). However, between the RVA and RVOT groups, no significant difference was observed at 12-month follow-up in terms of LVEF and dyssynchrony (LVEF P = .488; SD LV mPA P = .296). ConclusionNo significant difference was observed between RVOT and RVA groups with regard to LV function and synchrony over a 12-month follow-up. RVOT pacing offers may lead to better preservation of LV function on longer follow-up.

Development of mitral and tricuspid regurgitation in right ventricular apex versus right ventricular outflow tract pacing

This study aimed at comparing the development of tricuspid and mitral regurgitation between the right ventricular outflow tract (RVOT) and right ventricular apex (RVA) pacing. We prospectively enrolled 164 patients for permanent pacemaker implantation due to sick sinus syndrome or atrioventricular block and randomly divided them into two equal groups to receive either RVOT or RVA pacing. Patients with heart failure or valvular disease were excluded. The post-procedural echocardiographic evaluations were performed 1year after the pre-procedural echocardiography, and the results were compared with respect to the development of mitral and tricuspid regurgitation and probable changes in the ejection fraction (EF). Age, gender, pacing mode, and baseline cardiac rhythm did not significantly differ between the RVOT and RVA pacing groups. The incidence of mitral regurgitation was significantly higher in the RVA group (p = 0.03), but the incidence of tricuspid regurgitation was similar in both groups. There was a trend toward less tricuspid regurgitation in the RVOT group; however, it was not statistically significant. The mean EF was not significantly different between the study groups. It seems that the incidence of mitral regurgitation in RVA pacing is significantly higher than that in RVOT pacing. The formation of tricuspid regurgitation needs to be discussed in the future. IRCT201103146061N1.

An observational registry on efficacy and safety of the right ventricular outflow tract as a site for ICD leads: results of the EFFORT (EFFicacy Of Right ventricular outflow Tract as site for ICD leads) registry

Although pacing from the right ventricular outflow tract (RVOT) has been shown to be safe and feasible in terms of sensing and pacing thresholds, its use as a site for implantable cardioverter defibrillator (ICD) leads is not common. This is probably due to physicians' concerns about defibrillation efficacy. To date, only one randomized trial, involving 87 enrolled patients, has evaluated this issue. The aim of this observational study has been to compare safety (primary combined end point: efficacy of a 14-J shock in restoring sinus rhythm, R wave amplitude >4 mV and pacing threshold <1 V at 0.5 ms) and efficacy (in terms of effectiveness of a 14-J shock in restoring sinus rhythm after induction of VF, secondary end point) of two different sites for ICD lead positioning: RVOT and right ventricular apex (RVA). The study involved 185 patients (153 males; aged 67 ± 10 years; range, 28-82 years). Site of implant was left to physician's decision. After implant, VF was induced with a 1-J shock over the T wave or--if this method was ineffective--with a 50-Hz burst, and a 14-J shock was tested in order to restore sinus rhythm. If this energy was ineffective, a second shock at 21 J was administered and--eventually--a 31-J shock followed--in case of inefficacy--by a 360-J biphasic external DC shock. Sensing and pacing thresholds were recorded in the database at implant, together with acute (within 3 days of implant) dislodgement rate. The combined primary end point was reached in 57 patients in the RVOT group (0.70%) and in 81 patients in the RVA group (0.79%). The 14-J shock was effective in 159 patients, 63 in the RVOT group (77%) and 86 in the RVA group (83%). Both the primary and the secondary end points are not statistically different. R wave amplitude was significantly lower in the RVOT group (10.9 ± 5.2 mV vs. 15.6 ± 6.4 mV, p < 0.0001), and pacing threshold at 0.5 ms was significantly higher (0.64 ± 0.25 V vs. 0.52 ± 0.20 V, p < 0.01), but these differences do not seem to have a clinical meaning, given that the lower values are well above the accepted limits in clinical practice. Efficacy and safety of ICD lead positioning in RVOT is comparable to RVA. Even if we observed statistically significant differences in sensing and pacing threshold, the clinical meaning of these differences is--in our opinion--irrelevant.

Clinical and Electrophysiological Difference Between Idiopathic Right Ventricular Outflow Tract Arrhythmias and Pulmonary Artery Arrhythmias

The precise incidence and characteristics of ventricular arrhythmias originating from the pulmonary artery have not been fully described. The purpose of this prospective study was to clarify these points. Thirty-three consecutive patients with an idiopathic left bundle branch block and inferior-axis deviation type ventricular arrhythmia were included. All patients underwent detailed electroanatomical mapping (CARTO, Biosense-Webster, Diamond Bar, CA, USA) during sinus rhythm prior to the catheter ablation. The precise location of the catheter tip at the successful ablation site was confirmed by both electroanatomical mapping and contrast radiography. The clinical and electrophysiological data were compared between the right ventricular outflow tract (RVOT) arrhythmia patients (RVOT group) and PA arrhythmia patients (PA group). Eight patients (8/33 patients: 24.2%) had their ventricular arrhythmias successfully ablated within the PA. The local bipolar electrogram at the successful ablation sites in the PA group exhibited a significantly greater duration (P < 0.05) and lower amplitude (P < 0.05) than did those in the RVOT group (n = 19). In the PA group, all patients exhibited a multicomponent electrograms composed of a spiky potential and a dull potential, which might have consisted of near-field PA activation and a far-field ventricular activation, respectively, at the successful ablation site. Direct ablation to the spiky electrogram was able to eliminate the arrhythmias in all the PA group patients. PA arrhythmias may be more common than previously recognized. Careful mapping and interpretation of low amplitude and multicomponent electrograms are important for recognizing ventricular arrhythmias originating from the PA.

A Prospective Randomized Trial of Defibrillation Thresholds from the Right Ventricular Outflow Tract and the Right Ventricular Apex

Right ventricular outflow tract (RVOT) pacing has been suggested to improve hemodynamics and to help prevent pacing-induced cardiomyopathy. Pacing from the RVOT is feasible and equivalent in terms of sensing and stimulation threshold. However, physicians have been reluctant to use RVOT pacing because of concerns that defibrillation efficacy might be adversely affected. To date, there have been no randomized-controlled trials published comparing the defibrillation threshold in leads implanted in the RVOT and the right ventricular apex (RVA). The purpose of this study was to compare defibrillation thresholds (DFT) in the RVOT and RVA. Ventricular sensing and stimulation thresholds were also compared. This prospective, randomized, multicenter study included 87 patients (70 males, age 69 +/- 11 years). At implantation, the patient's ventricular implantable cardioverter-defibrillator (ICD) lead position was randomized to either the RVOT or RVA. A four-shock Bayesian up-down method was used to determine the DFT. Patients were followed for 3 months postimplant. DFTs were not significantly different in leads implanted in the RVOT (median 8.8 J [6.28, 12.9] vs. 7.9 J [6.20, 12.6], P = 0.65). Threshold and impedance measurements were stable in both RVOT and RVA groups from implant to follow-up. All ICD leads remained stable chronically at the 3-month follow-up. DFTs in leads placed in the RVOT and RVA are comparable. RVOT ICD lead placement is safe and exhibits similar lead stability, threshold, and impedance measurements as the traditional RVA location.

Survival Analysis in Patients With Preserved Left Ventricular Function and Standard Indications for Permanent Cardiac Pacing Randomized to Right Ventricular Apical or Septal Outflow Tract Pacing

Optimal right ventricular (RV) pacing site in patients referred for permanent cardiac pacing remains controversial. A prospective randomized trial was done to compare long-term effect of permanent RV apex (RVA) vs RV outflow tract (RVOT) pacing on the all-cause and cardiovascular mortality. A total of 122 consecutive patients (70 men, 69 +/-11 years), with standard pacing indications were randomized to RVA (66 patients) or RVOT (56 patients) ventricular lead placement. After the 10-year follow-up period the mortality data were summarized on the basis of an intention-to-treat analysis. During the long-term follow-up, 31 patients from the RVA group died vs 24 patients in the RVOT group (hazard ratio (HR), 0.96; 95% confidence interval (CI), 0.57-1.65; P=0.89). There were 10 cardiovascular deaths in the RVA and 12 in the RVOT group (HR, 1.04; 95%CI, 0.45-2.41; P=0.93). There were no differences in the all-cause or cardiovascular mortality between the pacing sites after adjustment for age, gender, arterial hypertension, atrial fibrillation, New York Heart Association class and left ventricular end-diastolic diameter. The RVOT provides no additional benefit in terms of long-term survival over RVA pacing.

Right and Left Ventricular Outflow Tract Tachycardias: Evidence for a Common Electrophysiologic Mechanism

"Idiopathic" ventricular arrhythmias most often arise from the right ventricular outflow tract (RVOT), although arrhythmias from the left ventricular outflow tract (LVOT) are also observed. While previous work has elucidated the mechanism and electropharmacologic profile of RVOT arrhythmias, it is unclear whether those from the LVOT share these properties. The purpose of this study was to characterize the electropharmacologic properties of RVOT and LVOT arrhythmias. One hundred twenty-two consecutive patients (61 male; 50.9 +/- 15.2 years) with outflow tract arrhythmias comprise this series, 100 (82%) with an RVOT origin, and 22 (18%) with an LVOT origin. The index arrhythmia was similar: sustained ventricular tachycardia (VT) (RVOT = 28%, LVOT = 36%), nonsustained VT (RVOT = 40%, LVOT = 23%), and premature ventricular complexes (RVOT = 32%, LVOT = 41%) (P = 0.32). Cardiac magnetic resonance imaging and microvolt T-wave alternans results (normal/indeterminate) were also comparable. In addition, 41% with RVOT foci and 50% with LVOT foci were inducible for sustained VT (P = 0.48), and induction of VT was catecholamine dependent in a majority of patients in both groups (66% and 73%; RVOT and LVOT, respectively; P = 1.0). VT was sensitive to adenosine (88% and 78% in the RVOT and LVOT groups, respectively, P = 0.59) as well as blockade of the slow-inward calcium current (RVOT = 70%, LVOT = 80%; P = 1.00) in both groups. Electrophysiologic and pharmacologic properties, including sensitivity to adenosine, are similar for RVOT and LVOT arrhythmias. Despite disparate sites of origin, these data suggest a common arrhythmogenic mechanism, consistent with cyclic AMP-mediated triggered activity. Based on these similarities, these arrhythmias should be considered as a single entity, and classified together as "outflow tract arrhythmias."

Electrocardiographic Characteristics of Repetitive Monomorphic Right Ventricular Tachycardia Originating Near the His‐Bundle

Most idiopathic nonreentrant ventricular tachycardia (VT) and ventricular premature contractions (VPCs) arise from the right or left ventricular outflow tract (OT). However, some right ventricular (RV) VT/VPCs originate near the His-bundle region. The aim of this study was to investigate ECG characteristics of VT/VPCs originating near the His-bundle in comparison with right ventricular outflow tract (RVOT)-VT/VPCs. Ninety RV-VT/VPC patients underwent catheter mapping and radiofrequency ablation. ECG variables were compared between VT/VPCs originating from the RVOT and near the His-bundle. Ten patients had foci near the His-bundle (HIS group), with the His-bundle local ventricular electrogram preceding the QRS onset by 15-35 msec (mean: 22 msec) and His-bundle pacing produced a nearly identical ECG to clinical VT/VPCs. The HIS group R wave amplitude in the inferior leads (lead III: 1.0 +/- 0.6 mV) was significantly lower than that of the RVOT group (1.7 +/- 0.4 mV, P < 0.05). An R wave in aVL was present in 6 of 10 HIS group patients, while almost all RVOT group patients had a QS pattern in aVL. Lead I in HIS group exhibited significantly taller R wave amplitudes than RVOT group. HIS group QRS duration in the inferior leads was shorter than that of the RVOT group. Eight of 10 HIS group patients exhibited a QS pattern in lead V1 compared to 14 of 81 RVOT group patients. HIS group had larger R wave amplitudes in leads V5 and V6 than RVOT group. VT/VPCs originating near the His-bundle have distinctive ECG characteristics. Knowledge of the characteristic QRS morphology may facilitate catheter mapping and successful ablation.

Usefulness of electroanatomical mapping to differentiate between right ventricular outflow tract tachycardia and arrhythmogenic right ventricular dysplasia

Differentiation between the different right ventricular rhythm disorders and specifically between arrhythmogenic right ventricular dysplasia (ARVD) and right ventricular outflow tract (RVOT) tachycardias has important clinical implications but remains a clinical challenge. We tested the hypothesis that the spatial association of local electrographic parameters may be used to discriminate between these 2 entities. Electroanatomic mapping of the right ventricle was performed in 3 groups: patients who had typical RVOT tachycardia, a control group of patients who had no ventricular arrhythmias, and patients who had a diagnosis of ARVD based on clinical, electrocardiographic, and structural findings. Electroanatomic mapping in the RVOT tachycardia group showed normal electrographic parameters throughout the right ventricle (unipolar electrographic amplitude 9.9 +/- 0.9 mV, duration 55 +/- 1 ms, amplitude/duration 0.193 +/- 0.022) that were no different from those in the control group. In contrast, dysplastic regions in the ARVD group were characterized by significantly lower amplitude (unipolar 3.6 +/- 0.4 mV), prolonged electrographic duration (unipolar 73 +/- 4 ms), and a decreased amplitude/duration ratio (unipolar 0.054 +/- 0.008) compared with the unaffected zones in the same hearts and with all regions in the RVOT and control groups. Thus, endocardial electrographic parameters do not differ between patients who have RVOT and control patients. RVOT tachycardia can be differentiated from ARVD by the absence of abnormal right ventricular electrographic findings. This ability may have important clinical implications and supports the concept of different underlying mechanisms for these 2 entities.