Verapamil-Sensitive Left Anterior Fascicular Ventricular Tachycardia: Results of Radiofrequency Ablation in Six Patients

Verapamil-Sensitive Left Anterior Fascicular VT. Introduction: Verapamil-sensitive left ventricular tachycardia (VT) with a right bundle branch block (RBBB) configuration and left-axis deviation bas been demonstrated to arise from the left posterior fascicle, and can be cured by catheter ablation guided by Purkinje potentials. Verapamil-sensitive VT with an RBBB configuration and right-axis deviation is rare, and may originate in the left anterior fascicle. Methods and Results: Six patients (five men and one woman, mean age 54 ± 15 years) with a history of sustained VT with an RBBB configuration and right-axis deviation underwent electrophysiologic study and radiofrequency (RF) ablation. VT was slowed and terminated by intravenous administration of verapamil in all six patients. Left ventricular endocardial mapping during VT identified the earliest ventricular activation in the anterolateral wall of the left ventricle in all patients. RF current delivered to this site suppressed the VT in three patients (ablation at the VT exit). The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 35, 30, and 20 msec, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. In the remaining three patients, RF catheter ablation at the site of the earliest ventricular activation was unsuccessful. In these three patients, Purkinje potential was recorded in the diastolic phase during VT at the mid-anterior left ventricular septum. The Purkinje potential preceded the QRS during VT by 66, 56, and 63 msec, and catheter ablation at these sites was successful (ablation at the zone of slow conduction). During 19 to 46 months of follow-up (mean 32 ± 9 months), one patient in the group of ablation at the VT exit bad sustained VT with a left bundle branch block configuration and an inferior axis, and one patient in the group of ablation at the zone of slow conduction experienced typical idiopathic VT with an RBBB configuration and left-axis deviation. Conclusion: Verapamil-sensitive VT with an RBBB configuration and right-axis deviation originates close to the anterior fascicle. RF catheter ablation can be performed successfully from the VT exit site or the zone of slow conduction where the Purkinje potential was recorded in the diastolic phase.     

Retrograde Supernormal Conduction in Concealed Accessory Atrioventricular Pathway Following Catheter Ablation

Supernormal Conduction in Concealed Kent Following Ablation. A case is presented of a 63-year-old woman with a concealed accessory pathway that exhibited retrograde supernormal conduction after radiofrequency catheter ablation. Although ventricular pacing at a slow rate revealed no retrograde conduction over the accessory pathway following ablation, the tachycardia recurred 15 months later. During ventricular pacing there was retrograde 1:1 conduction over the accessory pathway at a fast rate while there was intermittent VA dissociation with rare retrograde conduction at the slower rate. Ventricular extrastimulus testing demonstrated a supernormal conduction zone of the coupling interval. Thus, accessory pathways may exhibit supernormal conduction after catheter ablation. Pacing should be performed at both slow and fast rates to confirm the presence of conduction block following ablation.     

Hybrid Therapy of Radiofrequency Catheter Ablation and Percutaneous Transvenous Mitral Commissurotomy in Patients With Atrial Fibrillation and Mitral Stenosis

AF Ablation and PTMC. Background: The rhythm control of atrial fibrillation (AF) associated with mitral stenosis (MS) is often difficult using antiarrhythmic drugs (AADs), even after a percutaneous transvenous mitral commissurotomy (PTMC). Few studies have examined the efficacy and safety of simultaneously performing radiofrequency catheter ablation (RFCA) and a PTMC in patients with MS and AF. Methods: Twenty consecutive patients with drug‐resistant AF and rheumatic MS underwent RFCA combined with a PTMC (n = 10; persistent AF‐8, long‐lasting [>1 year] persistent AF‐2; RFCA group) or transthoracic direct cardioversion (DC) following a PTMC (n = 10; persistent AF‐7, long‐lasting persistent AF‐3; DC group). In all patients, the mitral valve morphology was amenable to a PTMC, and more than 2 AADs had been ineffective in maintaining sinus rhythm (SR). In the RFCA group, a segmental pulmonary vein isolation (PVI) was performed in the initial 5 patients, and an extensive PVI was performed in the remaining 5. Results: During a mean follow‐up period of 4.0 ± 2.7 years, 8 patients (80%) in the RFCA group were maintained in SR, as compared to 1 (10%) in the DC group (hazard ratio, 0.16; 95% confidence interval, 0.03 to 0.75; P = 0.008 by the log‐rank test). The prevalence of the concomitant use of class I and/or class III AADs was comparable between the 2 groups (P = 0.70). No complications occurred during the procedure or follow‐up period in either group. Conclusions: The hybrid therapy using RFCA and a PTMC was safe and feasible, and significantly improved the AF free survival rate compared to DC following a PTMC. (J Cardiovasc Electrophysiol, Vol. 21, pp. 284–289, March 2010)     

Longitudinal Dissociation in the His Bundle: A Possible Mechanism of Two Distinct Cycle Lengths in Atrioventricular Reentrant Tachycardia

Two wide QRS tachycardias with identical morphology but different cycle lengths (CLs) developed in a 63-year-old man. Electrophysiological study demonstrated inducible atrioventricular reentrant tachycardia (AVRT) due to a concealed left posterior accessory pathway (AP), which was successfully ablated by radiofrequency application. Neither dual AV nodal pathways nor other APs were documented. Splitting of the His-bundle electrogram was shown, and programmed stimulation induced sudden prolongation of intra-hisian conduction time. These results suggest longitudinal dissociation in the His bundle may be responsible for two distinct CLs in AVRT without dualAV nodal physiology.     

Time- Versus Frequency-Domain Analysis in Predicting Cycle Length of Inducible Ventricular Tachycardia After Myocardial Infarction

To determine whether time- and frequency-domain analyses differ in their ability to predict sustained ventricular tachycardia (VT) induced by programmed ventricular stimulation, 60 consecutive patients with myocardial infarction and 30 healthy control subjects were evaluated. Programmed ventricular stimulation using three extrastimuli and signal-averaged ECG recordings were performed in patients with myocardial infarction. Of the 60 patients, sustained monomorphic VT (SMVT) with cycle length (CL) ± 250 ms (slow SMVT) was inducible in 9, and SMVT with CL < 250 ms (fast SMVT) was inducible in 9. The durations of the filtered QRS (f-QRS) at each high-pass filter (25, 40, and 80 Hz) and the low amplitude signal (LAS) at 25-Hz high-pass filtering were significantly longer in the slow SMVT group than in the fast SMVT, no VT, or normal control group. The root-mean- square voltages at 25-Hz and 8Q-Hz high-pass filters in the slow SMVT group were significantly lower than in the fast SMVT, no VT, or normal control group. There was no significant difference in time- domain variables among fast SMVT, no VT, and normal control groups. The CL of the induced sustained VT was significantly correlated with the durations of f-QRS and LAS, Concerning frequency-domain variables (area ratio and factor of normality), there was no significant difference between slow and fast SMVT groups. Both the slow and fast SMVT groups had a significantly higher area ratio and a significantly lower factor of normality than the group with no VT or the normal control subjects. In conclusion, there were significant correlations between time-domain variables and CL of SMVT, while there was no correlation when using frequency-domain parameters.     

Atrioventricular Nodal Physiology After Slow Pathway Ablation

The A V nodal physiology before and 1 week after “slow pathway potential” guided catheter ablation was examined in 32 patients with AV nodal reentrant tachycardia. A mean of 4.9 applications of radiofrequency energy eliminated AV nodal reentrant tachycardia in all patients. There were no significant differences in sinus cycle length (815 ± 159 msec vs 813 ± 162 msec;P = NS) and fast pathway conduction properties before and 1 week after ablation. Slow pathway conduction was completely eliminated in 10 (31%) (group I) of 32 patients after ablation. In the remaining 22 patients residual slow pathway conduction associated with one AV node echo was observed. In 15 patients (47%) (group II), the effective refractory period of the slow pathway showed a change of < 30 msec (265 ± 51 vs 266 ± 51 msec; P = NS), and in 7 patients (22%) (group III), a prolongation of more than 80 msec (247 ± 56 vs 340 ± 42 msec; P = 0.0001) before and 1 week after ablation. Minimal and maximal A₂-H₂ interval over the slow pathway in group II was not significantly changed (Min A₂-H₂:241 ± 37 vs 247 ± 40 msec; P = NS, Max A₂-H₂: 346 ± 79 vs 350 ± 60 msec; P = NS), while a significant prolongation was measured in group III (Min A₂-H₂: 261 ± 53 VS 373 ± 107 msec; P < 0.01. Max A₂-H₂: 359 ± 41 vs 427 ± 63 msec; P < 0.05) before and after ablation. Conclusion: In group II patients there was no evidence shown of impairment of the slow pathway. This suggests that disruption of the link between fast and slow pathways may be responsible for the elimination of AV nodal reentrant tachycardia, besides the elimination or impairment of the slow pathway itself, in “slow pathway potential” guided catheter ablation, and that the slow pathway potential may not necessarily represent activation of the slow pathway itself or of its atrial connection.     

Surveillance interval of endoscopic examinations for colorectal cancer screening

Background: There have been a few evidence‐based studies concerning the relationship between the length of the surveillance interval of colonoscopic examinations and the risk of colorectal cancer (CRC). The aim of the present study was to assess the appropriate interval between endoscopic examinations for CRC screening in a retrospective cohort study. Methods: The cohort included subjects in whom cancer was not detected at the initial endoscopic examination and in whom endoscopic examination(s) was subsequently performed one or more times. The results of the endoscopic examinations performed in the mass screening for CRC between November 1983 and March 1999 were analyzed. The study end point was the detection of CRC and the detection rates of cancer were assessed among those who underwent examinations at various intervals between successive endoscopic examinations. Results: Among the 117 636 cohort subjects, 63 invasive cancer cases and 112 mucosal cancer cases were found. The odds ratio (OR) for invasive cancer was not significantly elevated even when the interval between successive examinations was over 5 years. The OR for mucosal or invasive cancer was significantly elevated among the subjects in whom the interval between successive examinations was over 5 years (OR, 1.71; 95% confidence interval (CI), 1.07–2.73), than among those in whom the interval was 1 year. Conclusions: Since prolongation of the interval between endoscopic examinations of up to 5 years did not result in any change in the cancer risk among persons who are at average risk for CRC, 5 years may be an adequate interval between endoscopic examinations in the mass screening for CRC.     

Prediction of the Plasma Concentration Profiles of Orally Administered Drugs in Rats on the Basis of Gastrointestinal Transit Kinetics and Absorbability

A new method based on gastrointestinal transit kinetics has been developed for estimation of the absorption profiles of drugs administered orally as aqueous solutions. The utility of the method was evaluated in rats. The gastrointestinal transit profile for each segment was estimated by in-vivo studies using phenol red, an unabsorbable marker. The gastrointestinal transit profile of phenol red was well explained by a linear gastrointestinal transit kinetic model with eight segments. We also introduced the absorption process into the gastrointestinal transit kinetic model and the plasma profile was predicted by the convolution method. The absorbability of drugs in each segment was assessed by an in-situ absorption study. The validity of the model was evaluated for model drugs with different absorption characteristics. The plasma profiles predicted for ampicillin, theophylline and cephalexin were in good agreement with those observed. The overestimated plasma profile of propranolol suggests that the low bioavailability of propranolol is a result of first-pass metabolism by the intestine wall and the liver, because the calculated absolute absorption is almost perfect. This proposed model is also suitable for estimation of segmental absorption, which is useful for the development of drug delivery systems. We have demonstrated that the plasma profile of orally administered drugs can be predicted by use of gastrointestinal transit and segmental absorbability information and that this method is especially useful for estimating separately the effect of absolute absorption and first-pass metabolism on the bioavailability of drugs.     

Enhancement of J–ST-Segment Elevation by the Glucose and Insulin Test in Brugada Syndrome

NOGAMI, A., et al. : Enhancement of J–ST-Segment Elevation by the Glucose and Insulin Test in Brugada Syndrome. The effects of glucose and insulin on J–ST-segment elevation were evaluated in seven men   (mean age 45 ± 10 years)   with Brugada syndrome. Six patients had been reanimated from VF and one patient had experienced syncope. The effects of intravenous (1) pilsicainide 50 mg, (2) glucose 50 g, and (3) glucose 50 g plus regular insulin 10 IU on the precordial ECG leads were examined. Pilsicainide significantly enhanced J-ST elevation in all patients and induced VF in 1 patient. A significant accentuation of the abnormal J-ST configuration was observed in all patients at a mean of   51 ± 40   minutes after glucose and insulin infusion. Changes in blood glucose and serum potassium concentration were   111 ± 158 mg/dL   and   −0.30 ± 0.48 mEq/L   , respectively. These changes were not directly related to the ECG changes. Glucose infusion without insulin caused a subtle increase in J-ST elevation. In conclusion, the administration of glucose and insulin safely unmasked or accentuation the J–ST-segment elevation in Brugada syndrome. Blood glucose and insulin concentrations may be factors modulating the circadian or day-to-day ECG variations in this syndrome. (PACE 2003; 26[Pt. II]:332–337)