Conduction through a Narrow Isthmus in Isolated Canine Atrial Tissue

Fuente, Domingo de la; Sasyniuk, Betty I.; Moe, Gordon K.

doi:10.1161/01.cir.44.5.803

Cited by 183 publications

(44 citation statements)

References 7 publications

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“…The safety factor of impulse propagation depends on the relation between the source (amount of current available in the propagating wave front) and the sink (structure that determines current density when the wave front arrives). [1][2][3] An abrupt increase of current load (sink) may reduce the safety factor of propagation, resulting in wave break and the formation of reentry. 14,15 PM, which creates a sudden increase of muscle thickness, increases the current sink for the incoming wave front.…”

Section: Source-sink Mismatch and The Formation Of Reentrymentioning

confidence: 99%

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Role of Papillary Muscle in the Generation and Maintenance of Reentry During Ventricular Tachycardia and Fibrillation in Isolated Swine Right Ventricle

et al. 1999

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Background-The role of papillary muscle (PM) in the generation and maintenance of reentry is unclear. Methods and Results-Computerized mapping (477 bipolar electrodes, 1.6-mm resolution) was performed in fibrillating right ventricles (RVs) of swine in vitro. During ventricular fibrillation (VF), reentrant wave fronts often transiently anchored to the PM. Tissue mass reduction was then performed in 10 RVs until VF converted to ventricular tachycardia (VT). In an additional 6 RVs, procainamide infusion converted VF to VT. Maps showed that 77% (34 of 44) of all VT episodes were associated with a single reentrant wave front anchored to the PM. Purkinje fiber potentials preceded the local myocardial activation, and these potentials were recorded mostly around the PM. When PM was trimmed to the level of endocardium (nϭ4), sustained VT was no longer inducible. Transmembrane potential recordings (nϭ5) at the PM revealed full action potential during pacing, without evidence of ischemia. Computer simulation studies confirmed the role of PM as a spiral wave anchoring site that stabilized wave conduction. Conclusions-We conclude that PM is important in the generation and maintenance of reentry during VT and VF.

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Section: Source-sink Mismatch and The Formation Of Reentrymentioning

confidence: 99%

“…[1][2][3] The papillary muscle (PM) is an electrically active tissue. For an electrical impulse to propagate from the ventricle to the PM, the electrical charge it carries (source) must excite both the ventricular muscle downstream and the PM that inserts into the ventricular tissue.…”

mentioning

confidence: 99%

Role of Papillary Muscle in the Generation and Maintenance of Reentry During Ventricular Tachycardia and Fibrillation in Isolated Swine Right Ventricle

et al. 1999

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“…Therefore, we could not define the site of conduction block as precisely as de la Fuente et al 9 were able to do in vitro.9 Also, we could not determine conduction velocity of the isthmus.…”

Section: Unipolar and Bipolar Plunge Hook Electrodes Made Frommentioning

confidence: 94%

“…1 1 0.02 (7) 0.18 ±+0.08 (9) NS Distal segment 0.13 0.03 (7) 0.12± 0.03 (9) NS Effective refractory period (msec) Proximal segment 152+6 (7) 136±4 (8) Proximal to distal 144± 12 (7) 161 + 12 (9) NS Distal to proximal 141 ± 11 (7) 161 ± 9 (9) NS (-) = not performed. length with 1: 1 conduction from the proximal to the distal segment was greater than that in the opposite direction by 30 msec or more.…”

Section: Unipolar and Bipolar Plunge Hook Electrodes Made Frommentioning

confidence: 99%

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Conduction over an isthmus of atrial myocardium in vivo: a possible model of Wolff-Parkinson-White syndrome.

Inoue¹,

Zipes²

1987

Circulation

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Antiarrhythmic drugs appear preferentially to prolong refractoriness of accessory pathways compared with atrial or ventricular muscle in patients with the Wolff-Parkinson-White syndrome. This response may be due to intrinsic properties of accessory pathways or to depressed conduction associated with a narrow strip, or isthmus, of tissue. To test the latter possibility, in 16 anesthetized dogs we surgically isolated a portion of the right atrial myocardium in the form of an ellipse (10 to 25 x 8 to 15 mm). The ellipse was connected to the body of the right atrium by a narrow isthmus (cross-sectional area [CSA] 1 to 13.5 mm2) and was perfused by the sinus node artery or its branch. Diastolic threshold (mean + SE 0.16 ± 0.05 vs 0.13 ± 0.02 mA) and effective refractory period (ERP; 144 4 vs 139 + 5 msec) were the same proximal and distal to the isthmus. In eight dogs, determination of the ERP of the isthmus was limited by the ERP of the atrial tissue proximal and distal to the isthmus, and the CSA of the isthmus in these dogs was significantly larger than that in the remaining seven dogs in which the ERP of the isthmus could be determined (7.4 + 1.4 vs 3.2 0.6 mm2, p < .05). The shortest pacing cycle length (PCL) with 1: 1 conduction from the proximal to the distal segments did not differ from that in the opposite direction in 16 dogs (154 ± 9 vs 153 + 7 msec). The CSA of the isthmus correlated inversely with the shortest PCL with 1: 1 conduction in both directions via the isthmus (r = -.84, p < .01). Vagal stimulation shortened the shortest PCL with 1: 1 conduction from the distal to the proximal segment (153 14 vs 143 + 12 msec, p < .02), but not in the opposite direction. Procainamide (10 to 20 mg/kg iv, serum concentration 8.6 + 0.8 ,ug/ml) prolonged the ERP of the proximal site from 145 ± 5 to 170 ± 5 msec (p < .001), the ERP of the distal site from 143 + 6 to 168 + 6 msec (p < .001) in 12 dogs, and the shortest PCL with 1: l conduction (proximal to distal from 149 + 8 to 204 + 17 msec, p < .001; distal to proximal from 149 + 7 to 197 + 12 msec, p < .001) in 14 dogs. After procainamide, the increase in the ERP of the isthmus in both directions was greater than the increase in the ERP of the proximal and distal atrial segments in five dogs (37 ± 7 vs 18 6 msec, p < .001). Infusion of isoproterenol (0.1 gg/kg/min) improved conduction over the isthmus, which had been depressed by procainamide in six dogs. We conclude that an isthmus of atrial tissue depresses conduction. The narrower the isthmus, the greater the depression of conduction. Procainamide lengthens the ERP of the isthmus more than it lengthens the ERP of atrial muscle. These findings may help explain the effects of antiarrhythmic drugs on accessory pathways that act as an isthmus in patients with the Wolff-Parkinson-White syndrome. Circulation 76, No. 3, 637-647, 1987. ALTHOUGH ACCESSORY PATHWAYS are thought to be composed of working myocardium,' refractoriness and conduction in them frequently are different from those in atrial or ventricu...

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