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Query: UMLS:C0728731 (prematurity)
 7,134 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Patterns of ventriculoatrial conduction have been used to distinguish retrograde conduction over an accessory atrioventricular pathway from that over the normal atrioventricular conduction system. Ventriculoatrial conduction at a constant interval during incremental ventricular pacing and during progressive prematurity of ventricular extrastimuli has been considered characteristic of conduction over an accessory pathway. We describe three patients with the Wolff-Parkinson-White syndrome who had progressive or sudden increments in ventriculoatrial conduction over an accessory pathway during fixed-rate ventricular pacing or during introduction of ventricular extrastimuli. Such properties have been considered characteristic of conduction over the normal atrioventricular conduction system. We conclude that retrograde conduction over accessory pathways may resemble conduction over the normal atrioventricular conduction system.
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PMID:Atypical patterns of retrograde conduction over accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome. 49 75

To study the pathway of tachycardia in patients with the Wolff-Parkinson-White (WPW) syndrome and reciprocal tachycardias, results from intracavitary recordings and atrial and ventricular stimulation were reviewed in 71 patients with the WPW syndrome and 54 patients without pre-excitation. In all patients a reproducible tachycardia could be initated and terminated by appropriately timed electrical stimuli. The following findings were accepted as suggesting the participation of an accessory pathway in the tachycardia circuit: 1) no increase in ventriculo-atrial conduction (V-A C) time following ventricular stimuli given with increasing prematurity; 2) activation of right or left atrium (depending upon the location of the atrial end of the accessory pathway) prior to activation of atrium in the His bundle lead; 3) slowing of tachycardia following bundle branch block to the ventricle in which the accessory pathway inserts; 4) V-A C time of early stimuli on the ventricle during the tachycardia equal to or less than the V-A c time following QRS complexes during tachycardia; 5) inability to initiate tachycardia or slowing of tachycardia following the administration of drugs affecting the accessory pathway. Accepted as suggestive for atrioventricular (A-V) nodal re-entry were the following factors: 1) activation of atrium following initiation of tachycardia by a single atrial premature beat after activation of the bundle of His but before or simultaneous with ventricular activation in first and subsequent beats of tachycardia; 2) initiation of tachycardia following a gradual increase in V-A C time with the appearance of a His bundle electrogram in between the premature beat and retrograde atrial activation; 3) gradual increase in V-A C time with the appearance of a His bundle electrogram following ventricular premature beats given with increasing prematurity; 4) two-to-one block distal to the A-V node or His bundle with persistance of tachycardia. If only positive findings were accepted, 51 patients of the WPW group used their accessory pathway during tachycardia. In eight patients re-entry was confined to the A-V node. In the remaining 12 patients the mechanism was not clear. Of the patients not showing pre-excitation in A-V direction, 47 patients seemed to have their re-entry circuit in the A-V node, five patients used an accessory pathway in V-A direction, and in two patients the pathway of tachycardia could not be identified.
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PMID:The role of an accessory atrioventricular pathway in reciprocal tachycardia. Observations in patients with and without the Wolff-Parkinson-White syndrome. 113 22

To elucidate the mechanical consequences of ventricular pre-excitation in patients with the W,W syndrome, electrical and mechanical events in the ventricles during anomalous pathway conduction and normal atrioventricular conduction were examined mechanocardiographically in 11 cases of Group A and 19 cases of Group B, in whom anomalous pathway conduction was stopped by procaine amide, resulting in normalization of conduction. Eight healthy persons were employed as a control group. In the control group, procaine amide had no significant effect on the mechanocardiographic values. In the WPW syndrome, significant prolongation of the P-X, P-J, P-T, P-C, P-I, P-Ao, and P-II intervals was induced by the drug. From the results of statistical analyses of measured values, it would appear that mechanical events in the ventricles were accelerated by ventricular pre-excitation but the extent of acceleration of the former was less than the extent of prematurity of the latter. The anomalous ventricular pre-excitation occurred earlier in cases of Group B than in those of Group A, while initiation of ventricular contraction, atrioventricular valve closure, and aortic vlave opening were accelerated more in Group A. In one case of Group B, electrical phenomena could not be related to mechanical events.
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PMID:Wolff-Parkinson-White syndrome: mechanocardiographic study on the mechanical consequences of ventricular pre-excitation. 113 37

The timing of entrainment onset has been shown to correlate with the conduction time to critical elements of a tachycardia circuit in a pacemaker model of reentrant ventricular tachycardia (VT). The utility of this method in evaluating clinical reentrant tachycardias was therefore evaluated in 24 patients with symptomatic Wolff-Parkinson-White syndrome and single bypass tracts (left free wall in 17, posteroseptal in 5, anteroseptal in 1, and right free wall in 1). Right ventricular apex (RVA) pacing during orthodromic atrioventricular reentrant tachycardia (oAVRT) at 10-70 msec less than tachycardia cycle length demonstrated concealed entrainment of the tachycardia in all patients studied. An entrainment index (EI), defined as the minimal prematurity of the ventricular stimulus that first resulted in atrial reset, was calculated from multiple entrainments in each patient. The EI was 121 +/- 25, 83 +/- 19, and 55 msec for left free wall, septal, and right free-wall bypass tracts, respectively (P = 0.004 for difference between left free wall and septal). A corrected EI, derived by subtracting the amount of atrial reset from the EI, gave values of 108 +/- 22 and 71 +/- 17 msec for left free wall and septal bypass tracts (P = 0.001). These values were compared to the preexcitation index (PI) by linear regression analysis in these patients. The PI correlated closely with both the EI and the corrected EI (r = 0.90 and 0.93, respectively), but the PI could only be derived in 12/17 (71%) left free-wall tachycardias versus the EI in 17/17 (100%) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Entrainment onset in atrioventricular reciprocating tachycardia: value in bypass tract localization and relationship to the preexcitation index. 170 97

Infranodal conduction delay is an uncommon mechanism of initiation of circus movement tachycardia in the Wolff-Parkinson-White syndrome. A patient with a concealed left free wall atrioventricular accessory pathway who underwent electrophysiological study is presented. During atrial extrastimulus testing, a pattern of alternating bundle branch block was observed and was most marked after the administration of intravenous procainamide. Conversion from right bundle branch block to left bundle branch block was reproducibly associated with the initiation of circus movement tachycardia utilizing the normal conducting system antegradely and the accessory pathway retrogradely. Initiation of tachycardia was critically related to the increase in the HV interval associated with left bundle branch block. Of interest, conduction in the right bundle branch became progressively slower as the prematurity of the atrial extrastimulus increased, whereas conduction time through the left bundle branch remained fixed prior to block. Implications of these findings are discussed. To our knowledge, this is the first report of alternating bundle branch block during atrial extrastimulus testing as a mode of initiation of circus movement tachycardia in the Wolff-Parkinson-White syndrome.
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PMID:An unusual mechanism of initiation of circus movement tachycardia in a patient with concealed Wolff-Parkinson-White syndrome. 619 3

We studied the limiting factor for the initiation of reentrant tachycardia in 14 patients with concealed Wolff-Parkinson-White syndrome by comparing atrial refractoriness and echo times. When relatively late atrial premature beats (A2) were not accompanied by an atrial echo (Ae), the echo times were estimated from the antegrade A2-V2 conduction time of A2, since the retrograde conduction time via the accessory pathway remained constant regardless of the degree of prematurity. Thus, A2-Ae curves including the minimal echo time and the longest A2-Ae without Ae could be drawn in all patients. Then the curve was compared with the atrial effective refractory periods and the functional refractory periods of A2 in each patient. Atrial refractoriness which might limit the occurrence of an Ae is not that of basic beats (A1) but that of premature beats (A2). In all patients the atrial effective refractory periods of A2 were much shorter than the minimal echo time and the longest A2-Ae without Ae, suggesting that the atrial effective refractory period is not responsible for limiting the initiation of an Ae. Also in 13 of 14 patients, the atrial functional refractory periods were shorter than the minimal echo time and the longest A2-Ae without Ae. In one patient, the atrial functional refractory period was sandwiched between the minimal echo time and the longest A2-Ae without Ae suggesting the atrial functional refractory period of Ae might be responsible for limiting the occurrence of an Ae in this patient.
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PMID:Limiting factor for the initiation of reentrant tachycardia in concealed Wolff-Parkinson-White syndrome. 686 5

Methylxanthine use in the treatment of apnea of prematurity is well documented. This drug is avoided in patients with aberrant pathways of conduction such as Wolff-Parkinson-White syndrome. In theory, methylxanthines enhance precipitation and exacerbation of tachyarrhythmias to which these patients are predisposed. This article reports a case of Wolff-Parkinson-White syndrome in a preterm neonate with severe apneic episodes in which methylxanthines were used. However, no adverse effects on cardiac rate or rhythm were encountered.
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PMID:Impact of theophylline use in Wolff-Parkinson-White syndrome. 876 28