How small could a detectable reentrant circuit be in a localized microreentrant tachycardia?
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ABSTRACT:
SUBMITTER: Mantovan R
PROVIDER: S-EPMC7157758 | biostudies-literature | 2020 Apr
REPOSITORIES: biostudies-literature
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How small could a detectable reentrant circuit be in a localized microreentrant tachycardia?
Mantovan Roberto R Corò Leonardo L Allocca Giuseppe G Sitta Nadir N Rivetti Luigi L Marinigh Ricarda R
HeartRhythm case reports 20200113 4
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Project description: Not available
| S-EPMC5419940 | biostudies-literature
Project description:BackgroundIn vivo description of ventricular tachycardia (VT) circuits is limited by insufficient spatiotemporal resolution. We used a novel high-resolution mapping technology to characterize the electrophysiological properties of the postinfarction reentrant VT circuit.MethodsIn 15 swine, myocardial infarction was induced by left anterior descending artery balloon occlusion. Animals were studied 6 to 8 weeks after myocardial infarction. Activation mapping of VTs was performed by using the Rhythmia mapping system. Activation time was based on a combination of bipolar and unipolar electrograms. The response to overdrive pacing from different zones of the circuit was examined.ResultsA total of 56 monomorphic VTs were induced (3.8±2.1 per animal). Among these, 21 (37.5%) were hemodynamically stable and allowed mapping of the circuit. Isthmuses were 16.4±7.2 mm long and 7.4±2.8 mm wide. Conduction velocities were slowest at the inward curvature into the isthmus entrance (0.28±0.2 m/s), slightly faster at the outward curvature exit (0.40±0.3 m/s) and nearly normal at the central isthmus (0.62±0.2 m/s). In 3 animals, 2 VT morphologies with opposite axes sharing the same isthmus were mapped. Conduction velocities within the shared isthmus were dependent on the activation vector, consistently slower at the proximal curvature. Overdrive pacing from isthmus sites determined by activation mapping was consistent with entrainment criteria for isthmus. However, dimensions of the isthmus defined by entrainment exceeded dimensions of the isthmus measured by activation mapping by 32±18%.ConclusionsIn postinfarction reentrant VT, conduction velocities are slowest at the proximal and distal curvatures. Entrainment mapping overestimates the true size of the isthmus. High-resolution activation mapping of VT may better guide ablation therapy.
| S-EPMC5072375 | biostudies-literature
Project description:BackgroundAnisotropic reentrant excitation occurs in the remodeled substrate of the epicardial border zone (EBZ) of the 5-day infarcted canine heart. Reentry is stabilized because of the formation of functional lines of block. We hypothesized that regional differences of ionic currents in cells of the EBZ form these lines of block. Therefore, we first mapped reentrant circuits of sustained tachycardias, then dispersed cells (infarct zone cells, IZs) from the central common pathway of the circuit (IZc) as well as from the other side of the line of block (outer pathway, IZo) for study.Methods and resultsWe mapped reentrant circuits in the EBZ of infarcted hearts during sustained ventricular tachycardias (>30 seconds, n=17 episodes, cycle lengths=218+/-7.9 ms). INa density was reduced in both IZc and IZo, and the kinetic properties of IZc INa were markedly altered versus IZo. Structural remodeling of the sodium channel protein Nav1.5 occurred in IZs, with cell surface localization differing from normal cells. Both IZc and IZo have similar but reduced ICaL, whereas IZc showed changes in Ca2+ current kinetics with an acceleration of current decay. Computer simulations of the 2D EBZ showed that incorporating only differences between INa in IZc and IZo prevented stability of the reentrant circuit. Incorporating only differences between ICaL in the IZc and IZo cells also prevented stability of the circuit. However, incorporating both INa and ICaL current differences stabilized the simulated reentrant circuit, and lines of block formed between the 2 distinct regions.ConclusionsDespite differences in INa and ICaL properties in cells of the center and outer pathways of a reentrant circuit, the resulting changes in effective refractory periods tend to stabilize reentry in this remodeled substrate.
| S-EPMC4289139 | biostudies-literature
Project description:BackgroundInfarct border zone (IBZ) geometry likely affects inducibility and characteristics of postinfarction reentrant ventricular tachycardia, but the connection has not been established.ObjectiveThe purpose of this study was to determine characteristics of postinfarction ventricular tachycardia in the IBZ.MethodsA geometric model describing the relationship between IBZ geometry and wavefront propagation in reentrant circuits was developed. Based on the formulation, slow conduction and block were expected to coincide with areas where IBZ thickness (T) is minimal and the local spatial gradient in thickness (DeltaT) is maximal, so that the degree of wavefront curvature rho proportional, variant DeltaT/T is maximal. Regions of fastest conduction velocity were predicted to coincide with areas of minimum DeltaT. In seven arrhythmogenic postinfarction canine heart experiments, tachycardia was induced by programmed stimulation, and activation maps were constructed from multichannel recordings. IBZ thickness was measured in excised hearts from histologic analysis or magnetic resonance imaging. Reentrant circuit properties were predicted from IBZ geometry and compared with ventricular activation maps after tachycardia induction.ResultsMean IBZ thickness was 231 +/- 140 microm at the reentry isthmus and 1440 +/- 770 microm in the outer pathway (P <0.001). Mean curvature rho was 1.63 +/- 0.45 mm(-1) at functional block line locations, 0.71 +/- 0.18 mm(-1) at isthmus entrance-exit points, and 0.33 +/- 0.13 mm(-1) in the outer reentrant circuit pathway. The mean conduction velocity about the circuit during reentrant tachycardia was 0.32 +/- 0.04 mm/ms at entrance-exit points, 0.42 +/- 0.13 mm/ms for the entire outer pathway, and 0.64 +/- 0.16 mm/ms at outer pathway regions with minimum DeltaT. Model sensitivity and specificity to detect isthmus location was 75.0% and 97.2%.ConclusionsReentrant circuit features as determined by activation mapping can be predicted on the basis of IBZ geometrical relationships.
| S-EPMC2626544 | biostudies-literature
Project description: Not available
| S-EPMC10691950 | biostudies-literature
Project description:A 78-year-old woman presented 2 years after mitral valve replacement for rheumatic mitral stenosis with cardioversion-resistant atrial tachycardia (AT). Dual-loop AT was identified by activation mapping with the Rhythmia™ system (Boston Scientific, Marlborough, MA, USA) and confirmed by entrainment-mapping; one circuit with localized re-entry turned around the scar on the posterior left atrium and the other circuit, which was macro re-entrant, turned around the left superior pulmonary vein (LSPV) using the PV-carina, the ridge beween the left atrial appendage and the LSPV, and the roof. The two wavefronts fused on the posterior wall close to the LSPV. Radiofrequency ablation of an area of slow conduction on the posterior wall changed the tachycardia to roof-dependent AT which was then terminated by completion of a roof line. <Learning objective: In this case report, we demonstrate the importance of using both conventional entrainment mapping methods and a novel ultra-high density mapping system to precisely understand the mechanism and appropriately terminate the complex atrial tachycardia in patients with prior atrial fibrillation ablation.>.
| S-EPMC6149257 | biostudies-literature
Project description:A 70-year-old man with hypertensive heart disease underwent catheter ablation of persistent atrial fibrillation. After completing the pulmonary vein isolation, atrial burst pacing induced an annular atrial tachycardia (AT). Overdrive pacing exhibited constant fusion, indicating a macroreentrant mechanism of the AT. However, the CARTO3 activation map created using the Octaray catheter (both Biosense Webster, Irvine, CA) exhibited a centrifugal spread with the earliest activation site at the 4 o'clock position of the tricuspid annulus. In contrast, the Ripple map revealed a clear reentrant circuit with its isthmus located at the 4-6 o'clock position of the tricuspid annulus. The local electrograms in these areas recorded systolic and diastolic potentials simultaneously, and the misannotation of the large far-field potentials caused this discrepant result. Handling low-amplitude complex fractionated electrograms remains a challenge in creating a precise activation mapping. The Ripple map, especially when combined with the Octaray catheter, was effective in dynamically visualizing all these electrograms and accurately delineating the reentrant circuit.
| S-EPMC11361873 | biostudies-literature
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| S-EPMC10774521 | biostudies-literature
Project description:Supraventricular tachycardia is one the most frequent cardiac arrhythmias seen in patients, with AVNRT being the most common subtype. Two subgroups of AVNRT have been reported, that of typical and atypical. "Frog Sign," long considered a classic physical exam sign, albeit rare, is associated with typical AVNRT. We present a case of a patient who presented with frog sign and ultimately was determined to have AVNRT. Knowledge of "frog" sign aids clinical diagnosis and correct treatment.
| S-EPMC8547684 | biostudies-literature
Project description: Not available
| S-EPMC6058762 | biostudies-literature