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间歇性预激表现为δ波消失,P-R 间期正常,其发病率在心电图(ECG)异常的预激(WPW)综合征患者中为25～75%。在体表 ECG 上,WPW 综合征的 QRS 波群是由正常房室传导系统以及附加通道引起的心室激动融合而成。影响其体表 ECG 的因素主要有四个:(1)附加通道的位置,(2)房内传导时间,(3)附加通道的传导时间,(4)房室结-浦氏系统的传导时间。因此,预激的程度和 QRS 波群的形态取决于附加通道(而不是房室传导系统)传导所引起的除极心肌的相对数量。当一个系统对另一系统的传导时间发生相对改变时,融合的 QRS 波群形态便产生变化。因此即使附加通道有功能时,亦可不出现心室预激的 ECG 证据。
Intermittent pre-excitation showed a loss of δ wave and a normal P-R interval with a prevalence of 25-75% in patients with preeclamptic (WPW) syndromes with abnormal electrocardiogram (ECG). On the body surface ECG, the QRS complex of WPW syndrome is a combination of ventricular activation resulting from the normal atrioventricular conduction system and additional channels. There are mainly four factors affecting the body surface ECG: (1) the location of the additional channel, (2) the conduction time in the room, (3) the conduction time of the additional channel, and (4) the conduction time . Thus, the magnitude of the pre-excitation and the morphology of the QRS complex depend on the relative amount of de-polar myocardium caused by the conduction of additional channels (rather than the atrioventricular conduction system). When one system changes the conduction time of another system relatively, the morphology of the fused QRS complex changes. Therefore, ECG evidence of ventricular pre-excitation may not appear even if the additional channel is functional.