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Background and Purpose: Despite available criteria, diagnosis of the mechanisms of wide complex tachycardia is often incorrect. We aimed in this study to identify reasons for misdiagnoses and the value and limitations of clinical and surface electrocardiographic criteria.Data Identification: The analyzed data of 150 consecutive patients with wide QRS tachycardia from this study and a literature search of key papers in English since 1960 on clinical and surface electrocardiographic criteria form the basis of this report. The final correct diagnosis was made with intracardiac electrograms.Data Extraction and Analysis: Among the 150 patients, 122 had ventricular tachycardia, 21 had supraventricular tachycardia with aberrant conduction, and 7 had accessory pathway conduction. Only 39 of 122 patients with ventricular tachycardia were correctly diagnosed initially. In others, the diagnoses were supraventricular tachycardia with aberrant conduction (43 of 122) or simply a wide QRS tachycardia (40 of 122). Misdiagnosis in patients with aberrant or accessory pathway conduction was also common. Standard electrocardiographic criteria for ventricular tachycardia had unacceptable sensitivity, poor specificity, or both. Collectively such criteria allowed a correct diagnosis of ventricular tachycardia in 92% of cases. Diagnosis of ventricular tachycardia was also suggested by its association with structural heart disease. Criteria suggestive of ventricular tachycardia included atrioventricular dissociation, positive QRS concordance, axis less than -90 deg to +/- 180 deg, combination of left bundle branch block and right axis, QRS duration of greater than 140 ms with right bundle branch block and greater than 160 ms with left bundle branch block and, a different QRS during tachycardia compared to baseline preexisting bundle branch block.Conclusions: Ventricular tachycardia is the commonest underlying mechanism for wide QRS tachycardia. A correct diagnosis can usually be made from clinical and surface electrocardiographic criteria. [ABSTRACT FROM AUTHOR]

Objectives The primary objectives of this study were to assess the feasibility of temperature-controlled radiofrequency catheter ablation of left and right sided manifest accessory pathways in patients with Wolff-Parkinson-White syndrome and to gain more insights into biophysical aspects of temperature-controlled catheter ablation in humans. Background The electrode-tissue interface temperature and other biophysical parameters are among important variables determining the efficacy and safety of radiofrequency ablation of accessory pathways. Experimental studies have shown that radiofrequency-induced tissue necrosis can be accurately predicted by monitoring of catheter tip temperature. Methods 38 consecutive patients (14 f, 24 m; aged 42 ± 12 years) with anterograde conducting accessory pathways (left sided: n=22; right sided: n=l6) underwent temperature-controlled radiofrequency ablation (HAT 200S, Dr Osypka, Germany). The electrode temperature was monitored via a thermistor embedded into a 4 mm catheter tip. Power output was adjusted automatically during energy delivery in a closed loop system (preselected temp.: 70·1 ± 5·8°C). Results Accessory pathway conduction was successfully abolished in all patients after the delivery of 2·3 ± 2·1 radiofrequency pulses (range: 1–9, median: 2). Interruption of the accessory pathway as evidenced by loss of preexcita tion occurred after 5·9 ± 5·4 s. At the time of the interruption of the accessory pathway the catheter tip temperature measured 54·2 ± 11· 2 ° C in patients with left and 44·9 ± 5·0° C in patients with right sided accessory pathways, respectively (P<0·008). Higher temperature levels during left sided applications did not shorten the time it took for the effect to appear (left sided accessory pathway: 7· 5 ± 6· 3 s, right sided accessory pathway: 3· 7 ± 2· 9 s; ns). The catheter tip temperature was significantly higher during left compared to right sided applications after 5 (52· 1 ± 3· 1 °C vs 47· 2 ± 4· 3 ° C) and 10s (61· 5 ± 6· 2 ° C vs 52· 7 ± 4· 2° C) following initiation of the impulse (P<0· 005). Power output and delivered energy did not differ significantly at the time of accessory pathway abolition. Peak values of delivered power (45· 1 ± 10· 9 W vs 41· 3 ± 10· 6W; P< 0· 05) and total delivered energy (2452 ± 1335 J vs 1392 ± 762 J; P<0· 02) were significantly higher in the group of right sided pathways compared to left sided applications. The peak temperature measured 77· 1 ± 13 °C during effec tive and 69· 9 ± 14 °C during ineffective energy applications (P<0· 05). The time it took for the effect to appear was significantly longer in transiently effective pulses (10· 4 ± 7· 2 s) compared to permanently effective applications (5· 9 ± 5· 4 s; P<0· 02). Despite temperature control, an abrupt rise in impedance was observed in 10 of 89 (11%) energy applications. No procedure-related complications occurred. Conclusions Temperature-controlled radiofrequency ablation of manifest accessory pathways is highly effective and safe. The temperature response is faster and signficantly higher in left-sided energy applications compared to right-sided pulses. Peak temperature levels measured at the electrode tip are significantly higher during effective than ineffective pulses. Sudden rises in impedance are not com pletely prevented during temperature-controlled radiofrequency ablation of accessory pathway, although no procedure-related complications were noted in this patient cohort. [ABSTRACT FROM PUBLISHER]

Objective: The aim of this prospective study was to analyse the yield of programmed ventricular stimulation at the right ventricular apex compared with the outflow tract. Methods: A stepwise randomized cross-over protocol of programmed ventricular stimulation with alternating stimulation at both sites was used in 66 patients who were studied because of sustained ventricular tachycardia (n = 30), ventricular fibrillation (n = 7), or non-sustained ventricular tachycardia and/or syncope (n = 29). Results: There were no significant differences between the results of stimulation from either right ventricular site with regard to the presence or absence of structural heart disease, spontaneous arrhythmia, ejection fraction or effective refractory periods. Overall, monomorphic ventricular tachycardia was inducible in 33 patients (50%); in 25 patients (75.8%), this arrhythmia was induced from both sites. However, in only 17 of these 25 patients (68%) did the induced monomorphic ventricular tachycardias have the same morphologies and similar (± 50 ms) cycle lengths. Ventricular fibrillation was inducible in 11 patients (17%), mostly by three extrastimuli (n=8; 73%). : (1) stimulation from at least two right ventricular sites is desirable because of their independent contribution to the induction of ventricular tachyarrythmias, (2) the non-inducibility or inducibility at one ventricular site does not predict the effect at another stimulation site, (3) the effective refractory period at the right ventricular apex and outflow tract do not differ, (4) the inducibility of multiple ventricular tachycardia morphologies emphasizes the importance of documenting the cause of spontaneous arrhythmias with multiple electrocardiographic leads to ensure the correct interpretation of arrhythmias induced by programmed stimulation, (5) clinical or haemodynamic features cannot predict whether one or more stimulation sites will be required for induction of ventricular tachycardia. These results are important for the diagnostic evaluation and assessment of pharmacological or non-pharmacological interventions. [ABSTRACT FROM PUBLISHER]

Ventricular late potentials detected at the end of the QRS complex by the signal-averaged ECG have been shown to predict arrhythmic events after acute myocardial infarction. Spectral turbulence analysis is a novel technique for detecting abnormalities of cardiac electric activation inside the QRS complex. The purpose of this study was to combine these two analysis methods in order to increase the predictive power of the signal-averaged ECG in post-infarction patients. The study comprised a prospective series of 778 males under 66 years of age who survived the acute phase of myocardial infarction. Signal-averaged ECG recordings were performed before hospital discharge 2 to 3 weeks after infarction. The original Simson method was used for recording and analysing the time-domain signal-averaged ECG. Spectral turbulence analysis was performed using the same averaged vector magnitude QRS complexes (Del Mar Avionics). During the follow-up period of 6 months, 33 patients (4.2%) had an arrhythmic event (sustained monomorphic ventricular tachycardia in 13 cases, ventricular fibrillation in eight cases and sudden cardiac death in 12 cases). The predictive power of late potentials in the time domain, spectral turbulence analysis and their combinations were tested together with clinical variables using the Cox regression method. The combination of late potentials and a spectral turbulence analysis score (one or both abnormal) had the greatest influence on the prediction of arrhythmic events: late potentials+spectral turbulence analysis (regression coefficient B=0.75; P=0.0014), Selvester ECG score >10 (B=0.44; P=0.027), history of previous infarction (B=0.49; P=0.018) and non-sustained ventricular tachycardia during long-term ECG recording (B=0.50; P=0.035). The combination of late potentials and spectral turbulence analysis reached a sensitivity of 76%, a specificity of 63%, a positive predictive value of 8% a negative predictive value of 98%) and a total predictive accuracy of 61%. Patients with late potentials and/or abnormal spectral turbulence analysis were significantly less often free of arrhythmic events compared to patients with normal findings (92% vs 98%, P<0.0001, Breslow test). The relative risk ratio of combining late potentials+spectral turbulence analysis was 5.0 (CI 95% 2.1–11.5) for arrhythmic events. The combination of late potentials in the time domain and a spectral turbulence analysis score (one or both abnormal) is recommended for identification of patients at risk of arrhythmic events after acute myocardial infarction. Optimization of the criteria of abnormality could further improve the rather low positive predictive accuracy of the signal-averaged ECG in this setting. [ABSTRACT FROM PUBLISHER]

In 90 consecutive patients with coronary artery disease and sustained monomorphic ventricular tachycardia, who were treated with oral sotalol and underwent programmed stimulation to determine drug effectiveness, the influence of sotalol on induced ventricular tachycardia morphology was retrospectively examined. In 54 patients (60%) sotalol rendered the tachycardia non-inducible. However, contrary to drug-testing with class I antiarrhythmic agents, induction of multiple morphologies at baseline study did not predict failure of subsequent drug-testing with sotalol. In the remaining 36 patients (40%), in whom sotalol did not modify inducibility, 21 patients (i.e. a total of 23%) manifested at least one new morphology during electropharmacological testing on sotalol. This effect was independent of the degree of left ventricular dysfunction, infarct location and numbers of morphologies at baseline, but corresponded with drug-induced changes in refractoriness. This observation may be related to a proarrhythmic effect of sotalol. Slowing of ventricular tachycardia rate and changes in morphology may have implications in patients receiving implantable cardioverter-defibrillators or those undergoing ablative procedures. [ABSTRACT FROM PUBLISHER]

The role of programmed ventricular stimulation (PVS) in patients at high risk of sudden death related to idiopathic dilated cardiomyopathy (DCM) is still controversial The possible reason is that most study series have been too small or that only a few patients had documented sustained ventricular tachyarrhythmias. This study therefore, looked at PVS performed in 102 patients with DCM and documented sustained ventricular tachycardia (VT; n=63) or ventricular fibrillation (VF; n=39). Sustained VT was induced in 27 of 63 patients (43%) with documented sustained VT and in 14 of 39 patients (36%) with documented VF (ns). VF was induced in nine patients (14%) with a history of sustained VT and in seven (18%) with a history of VF (ns). At a mean follow-up of 32±15 months, sudden death occurred in 14 (14%) patients, a rate similar in both patients with documented VT and VF (ns). Incidence of sudden death at 36 months was 6% in patients with inducible sustained VT/VF compared to 29% in patients without inducible VT/VF (<0·05) A favourable drug regimen (response to drug and no intolerable side effects) was obtained by serial drug testing in 25 of all 102 patients (25%). A cardioverter defibrillator (ICD) was implanted in 32 patients, in 63% of whom discharges were observed during 18±11 months of follow-up; only one patient (3%) died suddenly. Thus, in patients with DCM, there was no relationship between documented and inducible ventricular tachzyarrhythmias, and initiation of sustained VT or VF had little prognostic value for the prediction of subsequent sudden death. Wherever antiarrhythmic drug therapy was of limited value, implantation of an ICD may improve the prognosis of these high risk patients. [ABSTRACT FROM PUBLISHER]

During the past decade, the high-resolution electrocardiogram as a non-invasive technique for the detection of ventricular late potentials has developed from an experimental method into a routinely applied non-invasive method for risk stratification of patients after myocardial infarction. Meanwhile, several approaches have been developed for the detection of ventricular late potentials including time–domain analysis, frequency–domain analysis and spectrotemporal mapping. Clinical applications are no longer limited to patients after myocardial infarction, but cover a wider spectrum of different cardiac diseases.This review focuses on some methodological aspects as well as on the results and current clinical applications of the analysis of the signal-averaged ECG in the time domain. [ABSTRACT FROM PUBLISHER]