Background

To validate the predictability of reentrant circuit isthmus locations without ventricular tachycardia (VT) induction during high-definition mapping, we used computer methods to analyse sinus rhythm activation in experiments where isthmus location was subsequently verified by mapping reentrant VT circuits.

Method

In 21 experiments using a canine postinfarction model, bipolar electrograms were obtained from 196-312 recordings with 4mm spacing in the epicardial border zone during sinus rhythm and during VT. From computerized electrical activation maps of the reentrant circuit, areas of conduction block were determined and the isthmus was localized. A linear regression was computed at three different locations about the reentry isthmus using sinus rhythm electrogram activation data. From the regression analysis, the uniformity, a measure of the constancy at which the wavefront propagates, and the activation gradient, a measure that may approximate wavefront speed, were computed. The purpose was to test the hypothesis that the isthmus locates in a region of slow uniform activation bounded by areas of electrical discontinuity.

Results

Based on the regression parameters, sinus rhythm activation along the isthmus near its exit proceeded uniformly (mean r²= 0.95±0.05) and with a low magnitude gradient (mean 0.37±0.10mm/ms). Perpendicular to the isthmus long-axis across its boundaries, the activation wavefront propagated much less uniformly (mean r²= 0.76±0.24) although of similar gradient (mean 0.38±0.23mm/ms). In the opposite direction from the exit, at the isthmus entrance, there was also less uniformity (mean r²= 0.80±0.22) but a larger magnitude gradient (mean 0.50±0.25mm/ms). A theoretical ablation line drawn perpendicular to the last sinus rhythm activation site along the isthmus long-axis was predicted to prevent VT reinduction. Anatomical conduction block occurred in 7/21 experiments, but comprised only small portions of the isthmus lateral boundaries; thus detection of sinus rhythm conduction block alone was insufficient to entirely define the VT isthmus.

Conclusions

Uniform activation with a low magnitude gradient during sinus rhythm is present at the VT isthmus exit location but there is less uniformity across the isthmus lateral boundaries and at isthmus entrance locations. These factors may be useful to verify any proposed VT isthmus location, reducing the need for VT induction to ablate the isthmus. Measured computerized values similar to those determined herein could therefore be assistive to sharpen specificity when applying sinus rhythm mapping to localize EP catheter ablation sites.

中文翻译：

---

窦性心律期间缓慢均匀的电激活是心肌梗死实验模型中折返性 VT 峡部位置和方向的指标。

背景

为了验证在高清映射期间没有室性心动过速 (VT) 诱导的折返环路峡部位置的可预测性，我们使用计算机方法分析实验中的窦性心律激活，随后通过映射折返 VT 环路验证峡部位置。

方法

在使用犬梗死后模型的 21 项实验中，在窦性心律和 VT 期间，从 196-312 次心外膜边界区以 4mm 间距记录获得双极电图。根据折返电路的计算机化电激活图，确定传导阻滞区域并定位峡部。使用窦性心律电描记图激活数据在折返峡部的三个不同位置计算线性回归。根据回归分析，计算了均匀性（波前传播的恒定性度量）和激活梯度（可能近似波前速度的度量）。目的是检验地峡位于由电不连续区域界定的缓慢均匀激活区域的假设。

结果

根据回归参数，沿着峡部出口附近的窦性节律激活均匀进行（平均 r ² = 0.95±0.05）并且具有低幅度梯度（平均 0.37±0.10mm/ms）。垂直于跨过其边界的峡部长轴，激活波前的传播不太均匀（平均 r ² = 0.76±0.24），尽管具有相似的梯度（平均 0.38±0.23mm/ms）。在出口的相反方向，在地峡入口处，均匀性也较差（平均 r ²= 0.80±0.22)，但幅度梯度较大（平均 0.50±0.25mm/ms）。沿着峡部长轴垂直于最后一个窦性心律激活部位绘制的理论消融线被预测可以防止 VT 再诱发。解剖传导阻滞发生在 7/21 实验中，但仅包括峡部横向边界的一小部分；因此，仅检测窦性心律传导阻滞不足以完全定义 VT 峡部。

结论

在窦性心律期间，在 VT 峡部出口位置存在具有低幅度梯度的均匀激活，但在峡部横向边界和峡部入口位置存在较少的均匀性。这些因素可能有助于验证任何建议的 VT 峡部位置，从而减少对 VT 感应以消融峡部的需要。因此，在应用窦性心律映射定位 EP 导管消融部位时，与此处确定的那些相似的计算机化测量值可能有助于提高特异性。