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Notes: We summarize the lessons learned from studies of hard scattering processes in high-energy electron-proton collisions at HERA and antiproton-proton collisions at the Tevatron, with the aim of predicting new strong interaction phenomena observable in next-generation experiments at the Large Hadron Collider (LHC). Processes reviewed include inclusive deep-inelastic scattering (DIS) at small x, exclusive and diffractive processes in DIS and hadron-hadron scattering, as well as color transparency and nuclear shadowing effects. A unified treatment of these processes is outlined on the basis of factorization theorems of quantum chromodynamics, and using the correspondence between the "parton" picture in the infinite-momentum frame and the "dipole" picture of high-energy processes in the target rest frame. The crucial role of the three dimensional quark and gluon structure of the nucleon is emphasized. A new dynamical effect predicted at high energies is the unitarity, or black disk, limit (BDL) in the interaction of small dipoles with hadronic matter, owing to the increase of the gluon density at small x. This effect is marginally visible in diffractive DIS at HERA and will lead to the complete disappearance of Bjorken scaling at higher energies. In hadron-hadron scattering at LHC energies and beyond (cosmic ray physics), the BDL will be a standard feature of the dynamics, with implications for (a) hadron production at forward and central rapidities in central proton-proton and proton-nucleus collisions, in particular events with heavy particle production (Higgs), (b) proton-proton elastic scattering, and (c) heavy-ion collisions. We also outline the possibilities for studies of diffractive processes and photon-induced reactions (ultraperipheral collisions) at LHC, as well as possible measurements with a future electron-ion collider.

Notes: This case report describes a patient with a sustained monomorphic VT after surgical repair of a tetralogy of Fallot (TOF). In combination with the three-dimensional electroanatomic mapping system, CARTO, and conventional mapping techniques the VT was identified as a macro-reentrant tachycardia circling around the border between pulmonary graft and right ventricular outflow tract (RVOT). A y-shaped ablation line crossing this zone was created. The VT terminated during RF application and was not inducible again. This case underlines the use of a combined conventional and three-dimensional electroanatomic mapping technique can be helpful for catheter ablation of ventricular arrhythmias in TOF patients. (PACE 2004; 27[Pt. I]:801–804)

Notes: WEISS, C., et al.: Impact of the Distribution and Structure of Myocardium in the Pulmonary Veins for Radiofrequency Ablation of Atrial Fibrillation. Focal AF is frequently triggered by ectopic beats mostly originating from the pulmonary veins (PVs). So far, the morphological substrate for this entity is not well defined. Therefore, the distribution of myocardial cells within the PV were examined as potential target sites for RF application. The PVs (118) of 30 human autopsied hearts (age of death 63 ± 13 years, 17 men) were dissected in their complete circumference starting 1 cm from the ostium. Tissue sections of the PV were stained with hematoxylin-eosin and with Masson's trichrome. To characterize the developmental state of the myocardial tissue in the PV, immunohistochemistry was performed with antibodies reacting with antigens which are stage specifically expressed during cardiac development (HNK1/Leu7, α-SMA, calponin and desmin). Furthermore, proliferative activity was assessed using antibodies against the Ki-67 antigen (MIB-1). In two hearts a left-sided common PV ostium was found. The other hearts showed four separated PV ostia. The ostium diameter of the right inferior PV (1.2 ± 0.3 cm) was significantly smaller (P 〈 0.05) than remaining PV ostia (right superior 1.5 ± 0.2, left superior, 1.5 ± 0.3 and left inferior 1.4 ± 0.3 cm) of the 118 specimen. There was no significant difference in the presence of myocardium in the PV 1-cm distant from the ostium comparing the right superior (78%), the right inferior (81%), the left superior (81%), and the left inferior (81%) PV. In 54% of cases the myocardial bundles covered the complete PV circumference. In up to 38% of the small extensions of the myocardial bundles myocardial cells, characterized by distinct cross-striations and spindle shape were found. However, since these cells could not be labeled for other markers than desmin, their immature state seems unlikely. The anatomic distribution of myocardium in the PV suggests that RF applied to the entire circumference may be frequently required for its electrical isolation. Whether spindle-shaped myocytes have different electrophysiological behavior has to be further investigated.

Notes: WEISS, C., et al.: Subthreshold Stimulation at the Focal Origin of Para-Hisian-Located Ectopic Atrial Tachycardia. The focal origin of ectopic atrial tachycardia (EAT) is occasionally located in the superoparaseptal region adjacent to the bundle of HIS. Radiofrequency catheter ablation (RFCA) of EAT in this anatomic location implies the potential hazard of adverse impairment of the AV conduction. Therefore, careful precise mapping is mandatory. Subthreshold stimulation as defined as the delivery of noncaptured low energy pulses has been introduced as an additional mapping technique for slow pathway ablation in the setting of AV nodal reentrant tachycardia and other reentrant tachycardia. A patient with a right superoparaseptal EAT focus, in which subthreshold stimulation (STS) could determine the site of successful subsequent RFCA is described. During STS with EAT termination no AV conduction disturbances, junction-escape rhythms or atrial capture could be recorded. Thus STS may be used as an additional mapping tool to identify successful ablation sites in EAT.

Notes: WEISS, C., et al.: Radiofrequency Catheter Ablation Using Cooled Electrodes: Impact of Irrigation Flow Rate and Catheter Contact Pressure on Lesion Dimensions. Irrigation of radiofrequency current (RF) ablation reduces the risk of thrombus formation. The aim of this study was to investigate the impact of different irrigation catheter flow rates and contact pressures from the catheter on the development of lesion dimension and thrombus formation. A thigh muscle preparation was achieved in six sheep to create a cradle that was filled and perfused with heparinized blood (250 mL/min, 37C°). RF ablation (30 s, 30 W) was initially performed with three different irrigation flow rates (5 mL/min, 10mL/min, and 20 mL/min) and a perpendicular position (0.1 N contact pressure) of the irrigated ablation catheter (“Sprinklr,” Medtronic, Inc., Minneapolis, MN, USA). The next lesions were induced with constant contact pressure of 0.05 Newton (N); 0.1 N; 0.3 and 0.5 N and a parallel or perpendicular orientation of the catheter, respectively. A constant irrigation flow of 10 mL/min was maintained during these RF applications. Cross sections of the lesions were investigated with regard to maximal depth and maximal diameter at and below the surface. During high flow irrigation (20 mL/min) the surface diameter was significantly smaller (0.63 ± 0.1 cm) compared to irrigation flow rates of 5 mL/min (0.88 ± 0.2 cm) and 10 mL/min (1 ± 0.1 cm). Thrombus formation was not observed during any RF application. Only in perpendicular catheter orientations with a contact pressure of 0.5 N were significantly deeper lesions (0.85 ± 0.12 cm) induced compared to 0.05 N (0.55 ± 0.02 cm), 0.1 N (0.7 ± 0.01 cm) and 0.3 N (0.67 ± 0.01 cm) contact pressure. There was no significant difference in lesion depth with different flow rates. Irrigated RF ablation even with low flow rates and high catheter contact pressure prevented thrombus formation at the electrode. Smaller lesion diameters have been created with high irrigation flow rates. The deeper lesion created with high catheter contact pressure might be caused by a greater power transmission to the tissue.

Notes: VENTURA, R., et al.: Atrial Premature Beats in Patients with Focal Atrial Fibrillation: Incidence at Baseline and Impact of Provocative Maneuvers. This study evaluated the incidence of atrial premature beats (APBs) and the impact of various provocative maneuvers in patients with focally initiated AF. Fifty patients (39 men, 57 ± 0.4 years) with focally initiated, paroxysmal AF underwent Holter recording and a standardized protocol of provocative maneuvers: vagomechanical stimulation, adenosine 12 mg IV, esmolol 500 ng/kg IV, orciprenaline IV 5 mg/50 mL saline 0.9%, and atropine 0.01 mg/kg IV A surface ECG was recorded for 20 minutes at baseline and following each part of the protocol. High focal activity was defined as ≥ 1 APB/minute. During Holter ECG, 29 (58%) patients had an amount of 〈 200 APBs, 12 (24%) patients 〈 700 ≥ 200, and 9 (18%) patients ≥ 700 APBs. Less than 1 hour of high focal activity was observed in 34 (68%) of the 50 patients. Before starting provocative maneuvers 15 (30%) patients had high focal activity whereas 35 (70%) presented 〈 1 APB/minute. In 29 (58%) patients APBs increased by ≥ 1/min during provocative maneuvers: by vagomechanical stimulation in 11 patients, after adenosine in 15, esmolol in 12, orciprenaline in 15, and after atropine in 9 patients. In all patients with ≥ 1 APB/min at baseline, focal activity decreased or disappeared during some single provocative maneuvers. AF occurred in eight patients under provocative maneuvers. No predictive factors of a successful provocative maneuver were detected with regard to the baseline patients characteristics and Holter results. In conclusion, patients with focally initiated AF have a low incidence of spontaneous APBs. Various provocative maneuvers successfully increase APBs in more than half of the patients; orciprenaline had the highest efficacy. Some provocative maneuvers may suppress APBs in the setting of high focal activity at baseline.

Notes: Induction of complete bidirectional conduction block via the posterior isthmus of the right atrium is introduced as a standard endpoint for catheter ablation of atrial flutter. The present study sought to investigate the impact of changes in P wave duration and morphology detected by the surface ECG during coronary sinus and posterolateral right atrial stimulation as a marker for conduction block. Morphology and duration changes of the paced P wave before and after radiofrequency catheter (RFC) ablation were estimated in 22 patients referred for ablation of atrial flutter. We looked for a morphology change of the terminal portion in the 12-lead ECG and an increment of P wave duration. In 16 of 22 patients in whom atrial flutter ablation resulted in a complete bidirectional block, the conduction block was unidirectional in 4 patients and conduction times remained unchanged in 2 patients. After induction of complete bidirectional block a change of the terminal portion of the P wave towards a more positive morphology in one or more inferior leads was detected in 14 (88%) of 16 patients during coronary sinus stimulation and in 15 (94%) of 16 patients during posterolateral right atrial stimulation. These changes were predominantly observed in the inferior leads. Positive morphology changes of the terminal P wave portion in the inferior leads indicating conduction block with a sensitivity of 86% and a specificity of 100% were observed. An increment of 10 ms or more in P wave duration indicates conduction block with a specificity of 100% and a sensitivity of 67%. There was a significantly larger increment of P wave duration during coronary sinus (CS) stimulation compared to posterolateral right atrial stimulation (38 ± 21 vs 16 ± 21 ms). The analysis of P wave duration and morphology in the inferior leads of the surface ECG is a reliable tool to assess the intraatrial conduction after atrial flutter ablation. Different conduction during coronary sinus and pos-terolateral right atrial pacing may cause a different P wave duration after ablation.

Notes: Catheter ablation orientated on the induction of a functional intraatrial block within the posterior isthmus of the tricuspid annulus has been shown to effectively abolish atrial flutter. In order to improve and simplify the current technique, a strategy based on an electrode catheter for combined right atrial and coronary sinus mapping and stimulation was explored prospectively. Twenty-four consecutive patients referred for catheter ablation of recurrent type I atrial flutter were included. A steerable 7 Fr catheter (Medtronic/Cardiorhythm) composed of two segments with 20 electrodes was used for right atrial and coronary sinus activation mapping and stimulation. Multiple steering mechanisms allowing intubation and positioning of the distal part within the coronary sinus were incorporated into the device. Adequate positioning of the mapping catheter was achieved solely via a transfemoral approach in all patients after 7.7 ± 4.6 minutes, providing stable electrogram recordings during the entire ablation procedure. Radiofrequency current ablation (16.3 ± 9.6 pulses) caused a significant bidirectional increase of the mean intraatrial conduction times via the posterior isthmus irrespective to the stimulation interval. Significant changes of intraatrial conduction properties were induced during ablation in 22 of 24 patients (bidirectional block: n = 18, unidirectional block: n = 3, conduction delay: n = 1, unchanged conduction: n = 2). Following ablation atrial flutter was noninducible in all patients. Twenty-two of 24 patients (92%) remained free of atrial flutter episodes during a follow-up of 12.5 ± 5.7 months. Two of six patients without a bidirectional conduction block had a recurrence of atrial flutter. Atrial flutter ablation guided by the induction of an intraatrial conduction block can be effectively performed with this novel strategy for combined mapping of the posterior tricuspid isthmus, including coronary sinus and right atrial free wall. This transfemoral approach has a high accuracy with respect to the detection of radiofrequency current-induced changes of intraatrial conduction patterns.

Notes: Coronary Sinus Mapping. Introduction: Local electrogranis recorded from the coronary sinus and great cardiac vein provide important information for the diagnosis of various arrhythmias and identification of target sites for ablation of left-sided accessory pathways. One limitation of present techniques is the inability, in many cases, to probe the great cardiac vein at the anterior mitral annulus. We tested the feasibility of a new technique for catheterization of the coronary sinus and great cardiac vein by means of a small-diameter electrode catheter advanced via a right femoral approach through an angiography catheter. Methods and Results: Of 22 patients (12 men and 10 women; ages 44.5 ± 13.4 years) undergoing radiofrequency ablation of a supraventricular tachycardia, cannulation of the coronary sinus orifice using a 6-French 1L or 2L Amplatz catheter was achieved in 20 patients (91%) within 0.9 ± 0.6 minutes; after cannulation, a 2-French octapolar electrode catheter with a soft radiopaque tip and a 3-mm interelectrode distance could he advanced in all 20 patients through the guiding catheter to the great cardiac vein in the anterior region of the AV sulcus within 0.8 ± 0.7 minutes. Atrial and ventricular local potentials were recorded all along the mitral annulus during sinus rhythm, atrial and ventricular pacing, or supraventricular tachycardia. Variation of local potential amplitude never exceeded 20% of the mean and presented similar stability at all annular regions. The arrhythmogenic substrate was identified in all patients. Of 18 patients with 21 left-sided accessory pathways, an accessory pathway potential could he recorded at the ablation site by one or more adjacent epicardial electrode pairs in 10 pathways. No procedure-related complications were observed. Conclusions: The technique introduced in this study proved feasible in 91% of patients. Its main advantages are the simplicity and rapidity of coronary sinus cannulation and the ability to advance the electrode catheter to the anterior cardiac vein. In addition, closely spaced bipolar electrograms resulted in enhanced atrial, ventricular, and accessory pathway potential resolution.

Notes: Introduction: Pulmonary veins (PVs) are the predominant location of triggers for atrial fibrillation (AF), but little is known about the electrophysiologic properties of PVs. In addition, the influence of amiodarone on the electrophysiologic properties of PVs has not been elucidated. Methods and Results: Fifty-five patients with symptomatic and drug-resistant AF were divided into two groups: group 1 patients (n = 29) without antiarrhythmic drug therapy at the time of electrophysiologic study (EPS), and group 2 patients (n = 26) undergoing continuous long-term treatment with amiodarone. EPS including programmed stimulation of both atria and within the PVs was performed in both groups. In group 1, the effective refractory period (ERP) of all PVs (174 ± 62 msec) was significantly shorter than the ERP of the left atrium ([LA] 254 ± 30 msec, P = 0.0001) and right atrium ([RA] 221 ± 29 msec, P = 0.0001). The same pattern was observed in group 2 (PV: 210 ± 58 msec; LA: 259 ± 35 msec, P = 0.0001; RA: 246 ± 37 msec, P = 0.0255). The ERP of all stimulated PVs was significantly lower in group 1 (174 ± 62 msec) than in group 2 (210 ± 58 msec; P = 0.0001). The ERP of the left superior and right superior PVs and RA but not the left inferior PV and LA were significantly increased in patients treated with amiodarone. Decremental conduction properties were observed in all stimulated PVs, and there were no significantly differences between the maximal decrement of both groups. Conclusion: The distinctive electrophysiologic properties of PVs are emphasized by amiodarone therapy. Long-term amiodarone treatment is responsible for heterogeneous alteration of the PV electrophysiology, which may account for the individual antiarrhythmic responses in a subset of patients with paroxysmal AF.