Pre-excited RR intervals during atrial fibrillation in the Wolff-Parkinson-White syndrome: Influence of the atrioventricular node refractory period

AbstractThe ventricular rate and percent of pre-excited QRS complexes during atrial fibrillation were compared in two groups of patients with the Wolff-Parkinson-White syndrome. Group A consisted of 22 patients whose anterograde effective refractory period of the accessory pathway was longer than that of the atrioventricular (AV) node. Group B consisted of 23 patients in whom this relation was reversed. No patient had organic heart disease.Both groups had a similar effective refractory period of the accessory pathway (288 ± 37 vs. 280 ± 26 ms), whereas that of the AV node was shorter in group A than group B (242 ± 25 vs. 285 ± 27 ms, p = 0.0001). Patients in group A had a lower percent of pre-excited QRS complexes during atrial fibrillation (39 ± 43% vs. 93 ± 20%, p = 0.0001). In the 21 patients whose refractory period was measured, the difference was plotted against the percent of pre-excited QRS complexes; there was a significant correlation between the two (r = −0.83, p < 0.001).In patients in whom pre-excited RR intervals were present, the pre-excited RR intervals were compared between the two groups. Both groups had similar effective refractory periods of the accessory pathway (265 ± 22 vs. 280 ± 27 ms) and ventricle (200 ± 17 vs. 211 ± 26 ms). The effective refractory period of the AV node was shorter in group A (248 ± 22 vs. 285 ± 28 ms, p = 0.0005). The shortest pre-excited RR interval did not show any difference (244 ± 37 vs. 265 ± 41 ms). However, both the average (328 ± 39 vs. 397 ± 56 ms, p = 0.001) and longest (495 ± 109 vs. 666 ± 205 ms, p = 0.02) pre-excited RR intervals were shorter in group A.These data suggest that interaction between the refractory periods of the AV node and accessory pathway contributes to the percent of pre-excited QRS complexes. The effective refractory period of the AV node also indirectly contributes to the duration of pre-excited RR intervals. This contribution is greatest when RR intervals are long

Effect of Propranolol on Ventricular Rate During Atrial Fibrillation in the Wolff-Parkinson-White Syndrome

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74695/1/j.1540-8159.1987.tb04511.x.pd

Radiofrequency catheter ablation in infants and children

Background: Diagnosis and treatment of paediatric arrhythmias remain challenging. Antiarrhythmic - drugs beta-blockers, class Ic and class III drugs, were the only treatment available for many years. Radiofrequency catheter ablation (RFCA) was introduced for adult patients in 1981 and has been used for children since 1989. Questions remain regarding the efficacy and safety in paediatrics.Method: A retrospective analysis of patient records, 12 years and younger, at Leuven University Hospital, from January 2011 - July 2015 was performed.Results: From January 2011 - July 2015, 51 ablations were performed in 44 patients ≤12 years of age. Mean age was 7 years (range 3 weeks - 12 years), 11 (21.5%) ≤2 years; mean weight 16.5kg (range 3.4 - 56kg); average screening time 33.5min (SD } 22.7). Echocardiography was normal in 32 (72.7%) of patients. All cases were done under general anaesthesia. Diagnosis at electrophysiological study: Atrioventricular reentry tachycardia in 26 (50.9%), atrial ectopic tachycardia in 7 (13.7%), intra-atrial reentry tachycardia in 5 (9.8%), atrioventricular nodal reentry tachycardia in 11 (21.6%) and ventricular tachycardia in 2 (3.9%). RFCA was successful in 44 (86.3%) with recurrence rate of 13.7%. No signifi cant complications were noted.Conclusion: RFCA can be performed safely and effectively in even the very young. Recurrence and complication rates are similar to those reported in adults. RFCA should be the treatment of choice in selected paediatric patients

The Wolff- Parkinson-White and related syndromes : an electrocardiographic appraisal

This is an electrocardiological study, based on electrocardiographic analysis of new cases as well as on a review of some features, hitherto unrecognized or not stressed, in subjects with these disorders, that may help throw more light on them. In six cases studied personally using intracardiac electrography - the technique of His bundle electrography - the contribution and relevance of this method will be analysed, and the results compared with the conclusions drawn from other contemporary work in this field. Thus, the clinical presentation of the cases, and of these syndromes, receives secondary attention, and more detailed analysis only when appropriate to substantiate the main burdens of the thesis. These case reports appear separately in Section c. The mechanism of production of arrhythmias is becoming much better understood, and some of the diagnostic measures that are discussed in this work provide a clearer picture of their genesis. It is not proposed to embark upon a detailed consideration of anti-arrhythmic therapy in these syndromes, but the general principles will be discussed, and special reference will also be made to some new developments in this field

Sudden death in patients without structural heart disease

AbstractSudden unexpected cardiac death generally occurs in persons with known or previously unrecognized heart disease. However, it has become evident that it occurs often enough in patients without any identifiable structural abnormality to warrant the cardiologist's attention. Mostly, it concerns young, active, and otherwise healthy individuals. This paper focuses on various categories of patients with life-threatening events considered to have occurred on a solely “electrical” basis. Currently, several entities are recognized with distinct electrophysiological abnormalities, including Wolff-Parkinson-White syndrome, long QT syndrome, the Brugada syndrome, short-coupled torsade de pointes, and catecholamine-induced polymorphic ventricular tachyarrhythmia. The remaining patients without such distinct abnormalities are categorized as having idiopathic ventricular fibrillation. Although mechanical cardiac function may seem normal, such patients might have certain discrete anatomic abnormalities, unidentifiable with current investigational tools. Possibly in the future, with development of newer and more sophisticated tools (magnetic resonance imaging, positron emission tomography, genetic testing), some or all cases of idiopathic ventricular fibrillation must be redefined as having specific genetic and/or anatomic bases. All patients successfully resuscitated from cardiac arrest due to ventricular tachyarrhythmia without clear precipitating factors (acute myocardial infarction, severe electrolyte or metabolic disturbances) are at high risk of recurrences. Long-term prophylactic therapy is indicated. Contrasting with older belief, survivors of idiopathic ventricular fibrillation are now also considered high-risk patients. The implantable cardioverter-defibrillator appears to be the safest and most effective therapy

Subthreshold Stimulation of the Human Heart

The effects of long duration subthreshold conditioning stimuli on refractory periods in the human heart have been studied in patients undergoing clinical electrophysiological studies. It has been shown that unipolar cathodal stimuli produce inhibition (lengthening of efifective refractory period), and unipolar anodal stimuli can produce either summation (shortening of effective refractory period) or inhibition, in both atrial and ventricular myocardium. Long duration conditioning stimuli produce much greater changes in refractory period than those shown in previous studies using short duration stimuli. Inhibitory effects can be produced 20 - 50 ms after the end of a subthreshold stimulus. Stimuli of shorter duration (20 ms or less) must have a greater amplitude to produce the same degree of inhibition as longer duration stimuli. The mechanism of the effect is uncertain, but may be related to sodium channel activation or inactivation by subthreshold electrical current. The spatial effects of subthreshold stimuli are very limited, inhibitory effects not being demonstrable 1 mm or more away from the site of delivery of the subthreshold pulses. Attempts to terminate reentrant arrhythmias were made using subthreshold pulses. Despite optimal mapping techniques, it was not possible to terminate any cases of atrioventricular reentrant tachycardia, atrioventricular nodal reentrant tachycardia or ventricular tachycardia using long duration cathodal conditioning stimuli. Higher amplitude pulses occasionally terminated the tachycardia, but only as a result of local capture. Thus it is likely that the spatial limitations of subthreshold stimuli preclude their routine use in the termination of tachycardias. Furthermore, the use of subthreshold stimulation as a mapping tool to identify suitable sites for catheter ablation for ventricular or supraventricular tachycardia seems to be impractical

Mechanisms of Paroxysmal Supraventricular Tachycardias according to Age and Gender

Background and Objectives：Age and gender are known to influence the mechanisms of paroxysmal supraventricular tachycardia (PSVT), but large scale data regarding this subject is limited. In addition, data regarding the mechanisms of PSVT in the Korean population is limited. In this study, we sought to investigate the different mechanisms of PSVT according to age and gender in Korean patients. Subjects and Methods：Database of 3,176 patients diagnosed with PSVT excluded atrial flutter or atrial fibrillation and referred for electrophysiologic study from 1986 to 2004 was retrospectively analyzed. The mechanisms of PSVT were classified as: WPW syndrome (WPW), atrioventricular reentrant tachycardia (AVRT) due to a concealed bypass tract (CBT), atrioventricular nodal reentrant tachycardia (AVNRT), atrial tachycardia (AT). Results：The mean age was 40.7±16.0 (1-90) and 53.3% of the patients were male. The mean age of females was significantly higher than males. (43.0±16.1 vs. 38.6±15.6, p<0.001) Overall, the dominant mechanism of tachycardia was AVRT at 62.6% (WPW: 31.1%, CBT: 31.5%), compared to AVNRT at 34.1 and AT at 3.1%. This was mainly due to the predominance of AVRT (74.2%; WPW: 38.1%, CBT: 361%) in male. The mechanisms of PSVT differed according to gender with 63.2% (1257/1988) of AVRT patients being males where as 64.6% (700/1084) of the AVNRT patients were females. The distribution of PSVT mechanisms differed according to gender. In males, the proportions of AVNRT : CBT : WPW were 22.7 : 36.1 : 38.1%, whereas in females the proportion was 47.2 : 26.3 : 23.0%. Age had a significant influence upon the mechanism of PSVT in both genders with an increasing proportion of AVNRT and a decreasing proportion of AVRT in the older age groups. AVRT was the dominant mechanism of PSVT in all age groups for males, where as AVNRT was the dominant mechanism of PSVT for females over 50 years of age. Conclusion：The mechanism of PSVT differs significantly according to age and gender. This may be due to the increased degeneration of accessory pathway with age and difference in the conduction properties of the accessory pathway according to gender. In Koreans, the overall dominant mechanism of PSVT was AVRT mainly due to it a greater male population.ope