Wide QRS Complex Arrhythmia with Alternating QRS Morphology: What Is the Mechanism?

A 75‐year‐old man was admitted due to an electrical storm with appropriate recurrent implantable cardioverter defibrillator (ICD) discharges. The patient had had an extensive anterolateral myocardial infarction with associated severe left ventricular dysfunction 10 years earlier (left ventricular ejection fraction, 25%), and an ICD was placed 9 years before admission for primary prevention of sudden cardiac death. A first invasive study induced up to five ventricular tachycardias and an extensive endocardial substrate ablation was performed. Despite intravenous β‐blockers, general anesthesia and procainamide infusion, the patient continued to have recurrent episodes of very slow sustained ventricular tachycardia with a right bundle branch block pattern. In a subsequent invasive study, no mid‐diastolic activity was found despite careful mapping during the induced clinical ventricular tachycardia and ablation attempts inside the apical endocardial scar were unsuccessful. A percutaneous epicardial approach with navigation system support (EnSite Precision^TM Cardiac Mapping System v. 2.0, St. Jude Medical, St. Paul, MN, USA) without antiarrhythmic infusion was planned. A wide QRS complex rhythm with alternating QRS morphology was readily induced by epicardial ventricular pacing trains (Fig. 1, top) that elicited both arrhythmia QRS patterns with very long stimulus QRS intervals (Fig. 1, bottom). What is the possible mechanism of this arrhythmia? Do we need further pacing maneuvers during the arrhythmia to localize critical sites at which ablation pulses can predictably be successful?     

Electrocardiographic patterns of superior right ventricular outflow tract tachycardias: distinguishing septal and free-wall sites of origin

INTRODUCTION: The superior right ventricular outflow tract (RVOT) septum and free wall are common locations of origin for outflow tract ventricular tachycardias (VT). We hypothesized that (1) unique ECG morphologies of pace maps from septal and free-wall sites in the superior RVOT could be identified using magnetic electroanatomic mapping for accurate anatomical localization; and (2) this ECG information could help facilitate pace mapping and accurate VT localization. METHODS AND RESULTS: In 14 patients with structurally normal hearts who were undergoing ablation for outflow tract VT, a detailed magnetic electroanatomic map of RVOT was constructed in sinus rhythm, then pace mapping was performed from anterior, mid, and posterior sites along the septum and free wall of the superior RVOT. Pace maps were analyzed for ECG morphologies in limb leads and transition patterns in precordial leads. Monophasic R waves in inferior leads for septal sites were taller (1.7 +/- 0.4 mV vs 1.1 +/- 0.3 mV; P < 0.01) and narrower (158 +/- 21 msec vs 168 +/- 15 msec; P < 0.01) compared with free-wall sites; lacked "notching" (28.6% vs 95.2%; P < 0.05); and showed early precordial transition (by lead V4; 78.6% vs 4.8%; P < 0.05). A positive R wave in lead I also distinguished posterior from anterior septal and free-wall sites. Based on QRS morphology in limb leads and precordial transition pattern (early vs late), in a retrospective analysis, a blinded reviewer was able to accurately localize the site of origin of clinical arrhythmia (the successful ablation site on the magnetic electroanatomic map) in 25 of 28 patients (90%) with superior RVOT VT. CONCLUSION: Pace maps in the superior RVOT region manifest site-dependent ECG morphologies that can help in differentiating free-wall from septal locations and posterior from anterior locations. Despite overlap in QRS amplitude and duration, in the majority of patients a combination of ECG features can serve as a useful template in predicting accurately the site of origin of clinical arrhythmias arising from this region.     

Quantitative susceptibility mapping and 23Na imaging‐based in vitro characterization of blood clotting kinetics

Blood clotting is a fundamental biochemical process in post‐hemorrhagic hemostasis. Although the varying appearance of coagulating blood in T₁‐ and T₂‐weighted images is widely used to qualitatively determine bleeding age, the technique permits only a rough discrimination of coagulation stages, and it remains difficult to distinguish acute and chronic hemorrhagic stages because of low T₁‐ and T₂‐weighted signal intensities in both instances. To investigate new biomedical parameters for magnetic resonance imaging‐based characterization of blood clotting kinetics, sodium imaging and quantitative susceptibility mapping (QSM) were compared with conventional T₁‐ and T₂‐weighted imaging, as well as with biochemical hemolysis parameters. For this purpose, a blood‐filled spherical agar phantom was investigated daily for 14 days, as well as after 24 days at 7 T after initial preparation with fresh blood. T₁‐ and T₂‐weighted sequences, a three‐dimensional (3D) gradient echo sequence and a density‐adapted 3D radial projection reconstruction pulse sequence for ²³Na imaging were applied. For hemolysis estimations, free hemoglobin and free potassium concentrations were measured photometrically and with the direct ion‐selective electrode method, respectively, in separate heparinized whole‐blood samples along the same timeline. Initial mean susceptibility was low (0.154 ± 0.020 ppm) and increased steadily during the course of coagulation to reach up to 0.570 ± 0.165 ppm. The highest total sodium (NaT) values (1.02 ± 0.06 arbitrary units) in the clot were observed initially, dropped to 0.69 ± 0.13 arbitrary units after one day and increased again to initial values. Compartmentalized sodium (NaS) showed a similar signal evolution, and the NaS/NaT ratio steadily increased over clot evolution. QSM depicts clot evolution in vitro as a process associated with hemoglobin accumulation and transformation, and enables the differentiation of the acute and chronic coagulation stages. Sodium imaging visualizes clotting independent of susceptibility and seems to correspond to clot integrity. A combination of QSM and sodium imaging may enhance the characterization of hemorrhage.     

Trilinear Modeling of Event-Related Potentials

This paper describes a method for estimating a set of spatial components (brain maps) and temporal components (waveforms) of brain potentials. These components play the role of bases of a coordinate system, in the sense that the brain potentials of any subject can be represented as superpositions of these components. The representation is unique given the spatial and temporal components, and this decomposition is particularly appealing for comparing the brain potentials of different subjects (say alcoholics and controls). It can also be used for single trial modeling, clinical classification of patients, and data filtering. The method is based on the topographic component model (TCM, Möcks 1988) which models brain potentials in a trilinear form. We extend the TCM in two aspects. First, the diagonal amplitude matrix is replaced by a general loading matrix based on some neurophysiological considerations. Secondly, the number of spatial components and the number of temporal components can be different. The spatial components and temporal components are obtained respectively by performing singular value decomposition (SVD). This method is illustrated with visual P3 data.     

三维电解剖标测及单根环状标测电极指导下CPVA术治疗心房颤动

目的探讨在三维电解剖标测及单根环状标测电极指导下以环肺静脉口电隔离术（CPVA）为核心治疗心房颤动（房颤）的疗效。方法对32例房颤患者均在CARTO三维电解剖标测及单根环状标测电极指导下行CPVA,其中辅助行碎裂电位消融6例,上腔静脉消融术2例,三尖瓣峡部、二尖瓣峡部及冠状窦内消融各1例。结果26例阵发性房颤不再被诱发,6例慢性房颤中术中房颤终止2例、电复律转为窦性心律4例;手术操作时间（119&#177;37）min,X线透视时间（25&#177;12）min;随访（9&#177;5）个月成功率为90.6%。均无手术并发症。结论三维电解剖标测及单根环状标测电极指导下以CPVA为核心,其他消融方法为辅的房颤消融策略安全有效,可提高消融成功率,缩短手术时间,减少并发症、复发。     

无左心房和肺静脉三维重建的阵发性心房颤动导管消融术

Objective To investigate the differences between modeling and non-modeling left atrium in Carto XP system guided catheter ablation for paroxysmal atrial fibrillation. Methods Thirty-one cases of par-oxysmal atrial fibrillation treated by the same electrophysiologist with guidance of Carto XP during Jan to Dec in 2008 were enrolled. Catheter ablation was accomplished without left atrium and pulmonary veins modeling in 17 patients (non-modeling group) and with left atrium modeling in 14 patients (modeling group). The detailed ablation method was based on circumferential pulmonary veins isolation (CPVI). And linear ablation of tricus-pid valvular isthmus was selectively proceeded individually. The ablation endpoint was set to complete isolation of pulmonary vein potential from left atrium and no continuous fast atrial arrhythmia including atrial fibrillation, atrial flutter and atrial tachycardia could be induced. Comparisons for each step during procedure and the fol-low-up outcomes had been done. Results The male: female ratio of the 2 groups were 10:4 and 11 : 6 (P >0.05). The average age were (54.64 ± 15.58) and (59.41 ± 10.59) (P >0.05) ,the diseased courses were (5.05 ±10.4) years and (7.34±7.74)years(P >0.05),the left atrial sizes were (35.29±4.73) mm and (36.47 ±6.15)mm (P > 0.05), the total procedure time was (107.23±28.92) rain and (93.47 ±26.09) win (P>0.05). The X-ray exposure time was (21.09 ±6.49)min (modeling group) and (14.16±5.35)min (non-modeling group,P < 0.05). The CPVI time of fight pulmonary veins was (27.29±18.53) rain (model-ing group) and 18.00 ±4.51 min (non-modeling group, P < 0.05). The CPVI time of left pulmonary veins was (28.14 ±9.26) rain (modeling group) and (23.94±7.10) rain (non-modeling group, P < 0.05). The successful rates was 85.7% (modeling group) and 82.4% (non-modeling group, P > 0.05) over follow-up for 2 to 13 months. Conclusion Carto system guided catheter ablation of paroxysmal atrial fibrillation without modeling of left atrium and pulmonary veins could take less time in X-ray exposure and ablation steps, compa-ring with left atrium modeling one.