The Effects of Cycle Length on Cardiac Refractory Periods in Man

Denes, Pablo; Wu, Delon; Dhingra, Ramesh C.; Pietras, Raymond J.; Rosen, Kenneth M.

doi:10.1161/01.cir.49.1.32

Cited by 378 publications

(98 citation statements)

References 6 publications

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“…These excessively shortened RP mean that right ventricular myocardial cells are able to be reactivated sometimes less than 130 ms after the preceding activation. This could be the consequence of very fast repolarization because of the mutated ionic currents involved, especially after previous short cycle lengths, which are known to physiologically decrease refractoriness in myocardial tissues 22, 24…”

Section: Discussionmentioning

confidence: 99%

Shortening of the Short Refractory Periods in Short QT Syndrome

Rollin

Gandjbakhch

Giustetto

et al. 2017

JAHA

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BackgroundDiagnosis of short QT syndrome (SQTS) remains difficult in case of borderline QT values as often found in normal populations. Whether some shortening of refractory periods (RP) may help in differentiating SQTS from normal subjects is unknown.Methods and ResultsAtrial and right ventricular RP at the apex and right ventricular outflow tract as determined during standard electrophysiological study were compared between 16 SQTS patients (QTc 324±24 ms) and 15 controls with similar clinical characteristics (QTc 417±32 ms). Atrial RP were significantly shorter in SQTS compared with controls at 600‐ and 500‐ms basic cycle lengths. Baseline ventricular RP were significantly shorter in SQTS patients than in controls, both at the apex and right ventricular outflow tract and for any cycle length. Differences remained significant for RP of any subsequent extrastimulus at any cycle length and any pacing site. A cut‐off value of baseline RP <200 ms at the right ventricular outflow tract either at 600‐ or 500‐ms cycle length had a sensitivity of 86% and a specificity of 100% for the diagnosis of SQTS.ConclusionsPatients with SQTS have shorter ventricular RP than controls, both at baseline during various cycle lengths and after premature extrastimuli. A cut‐off value of 200 ms at the right ventricular outflow tract during 600‐ and 500‐ms basic cycle length may help in detecting true SQTS from normal subjects with borderline QT values.

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Section: Discussionmentioning

confidence: 99%

Shortening of the Short Refractory Periods in Short QT Syndrome

Rollin

Gandjbakhch

Giustetto

et al. 2017

JAHA

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“…During these studies, patients were isolated and all equipment was grounded at equipotential. The following protocol for electrical stimulation was performed: (1) incremental atrial pacing to achieve the antegrade AV nodal Wenckebach cycle; (2) antegrade refractory periods using atrial basic drive of eight beats (A1A,), followed by premature atrial stimulation (A2); (3) (table I) The control CL that produced VA block was 364.6 ± 87.9 msec before PA. After PA, VA conduction was abolished in five of 13 cases (patients 2, 6, 7, 11 HV-50 fig. 3).…”

Section: Methodsmentioning

confidence: 99%

Procainamide and retrograde atrioventricular nodal conduction in man.

Shenasa¹,

Gilbert²,

Schmidt³

et al. 1982

Circulation

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SUMMARY Recent studies that show a depressant effect of procainamide (PA) on retrograde conduction in patients with atrioventricular (AV) nodal reentrant tachycardia (RT) have suggested possible incorporation of AV nodal bypass tracts. Electrophysiologic effects of i.v. PA, 10 mg/kg, on retrograde AV nodal conduction were examined in 13 patients without RT, demonstrable AV nodal refractory period curves, or accessory pathways. Ventriculoatrial (VA) conduction was recorded before and after PA using intracardiac electrograms, incremental ventricular pacing and extrastimulation. With incremental pacing during the control, VA block occurred at a mean cycle length (CL) of 364.6 ± 87.9 msec. After PA, VA conduction was abolished in five of 13 patients due to onset ages 53-82 years (mean + SD 66.2 ± 9.9 years), were studied because of recurrent ventricular arrhythmias, dizziness or syncope. Eight patients had arteriosclerotic heart disease and five had no clinically detectable heart disease. Ten had normal intraventricular conduction and three had right bundle branch block. Four patients had ventricular premature complexes and one patient had an old inferior myocardial infarction.Patients gave informed, signed consent for the study.Right-heart catheterization was performed in a nonsedated, postabsorptive state. With the patients under local anesthesia, quadripolar electrode catheters were percutaneously introduced through the femoral and antecubital veins and positioned under fluoroscopic guidance across the tricuspid valve near the AV junction to permit recording of the His bundle potential. The catheters were also advanced to the high right atrium and the right ventricle to permit recordings and electrical stimulation as previously described.3The intracardiac electrograms (filtered at 30-500Hz) and three sufrace lead ECGs (usually leads I, II, and V,) and a time line were simultaneously displayed on a multichannel oscilloscope (Electronics for Medicine VR-12) and recorded on a magnetic tape (Honeywell model 96). Recordings were reproduced on photographic paper at 100 or 150 mm/sec. Electrical stimulation was performed using a digital stimulator (DTU; Bloom Associated, Ltd.). During these studies, patients were isolated and all equipment was grounded at equipotential. The following protocol for electrical stimulation was performed:(1) incremental atrial pacing to achieve the antegrade AV nodal Wenckebach cycle; (2) antegrade refractory periods using atrial basic drive of eight beats (A1A,), followed by premature atrial stimulation (A2); (3) incremental ventricular pacing to achieve ventriculoatrial (VA) block; and (4)

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“…The AV nodal effective refractory period was defined as the longest A,-Ai interval at which Ai was not conducted to the His bundle. 14 …”

Section: Methodsmentioning

confidence: 99%

Quantification of human atrioventricular nodal concealed conduction utilizing S1S2S3 stimulation.

Wu¹,

Denes²,

Dhingra³

et al. 1976

Circulation Research

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SUMMARY We studied antegrade concealed conduction of alrial extrastimuli (A 2 ) that blocked in the atrioventricular (AV) node in eight subjects, using a third extrastimulus (A 3 ), coupled at decreasing coupling intervals to A 2 . Three A,-A 2 intervals were tested in each subject: late (just shorter than AV nodal effective refractory period), CONCEALED conduction is defined as the effect of a partially penetrating impulse on conduction of a subsequent impulse. 1 Common examples of concealed conduction include the P-R prolongation that follows blocked interpolated premature atrial or ventricular contractions. 2 " 4 In both cases, concealed conduction usually is in the atrioventricular (AV) node. 58 It has been suggested that the depth of penetration is related to the timing of the blocked premature impulse. 3 -"• '" For example, with antegrade concealed conduction of blocked atrial premature impulses, one might expect deep penetration of a late impulse with a marked effect on subsequent impulse conduction and superficial penetration of a very early impulse with minimal or no effect on subsequent conduction.In the present study we have attempted to quantify concealed conduction of antegrade blocked premature atrial contractions, using His bundle recording and extrastimulus techniques. We were specifically interested in how the timing of blocked atrial impulses affected the conduction of subsequent impulses. MethodsEight subjects were studied during diagnostic electrophysiological study for suspected sinus node or intraventricular conduction disease. To be included in this study, subjects had to show AV conduction limited to the AV node and a zone of coupling intervals of at least 50 msec separating the AV nodal effective refractory period and the atrial functional refractory period. In addition, the AV nodal conduction curves during the control state had to be continuous (not discontinuous, as in the case of dual AV nodal pathways) and stable."-12 The study group consisted of six males and two females, between 48 and 75 years in age. Five had suspected sinus node dysfunction, and three had intraventricular conduction defects. All eight showed intact AV conduction during sinus rhythm, two (cases 1 and 2) had prolonged A-H interval (normal = 54-130 msec) and five (cases 1, 3, 5, 7, and 8) had a prolonged AV nodal effective refractory period (normal = 235-380 msec) during sinus rhythm. Electrophysiological studies were performed in the postabsorptive, nonsedated state. Cardiac medications were discontinued at least 72 hours prior to the study. Informed written consent was obtained from each subject. A tripolar electrode catheter was placed across the tricuspid valve percutaneously via the femoral vein for His bundle recording; 13 a second, quadripolar, electrode catheter was positioned at the high lateral right atrium percutaneously via the other femoral vein. The distal two electrodes were used for atrial stimulation, and the proximal two electrodes were used to record high right atrial electrograms. Multiple el...

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The Effects of Cycle Length on Cardiac Refractory Periods in Man

Cited by 378 publications

References 6 publications

Shortening of the Short Refractory Periods in Short QT Syndrome

Shortening of the Short Refractory Periods in Short QT Syndrome

Procainamide and retrograde atrioventricular nodal conduction in man.

Quantification of human atrioventricular nodal concealed conduction utilizing S1S2S3 stimulation.

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