In the treating of scar-related ventricular tachycardia（VT）, the goal is to identify the VT circuit and ablate critical slow conduction areas when their hemodynamics are stable. However, if the VT is hemodynamically intolerated, the focus shifts to identifying and ablating the substrate. Among available techniques, pace-mapping is particularly useful, as it helps identify the origin of ventricular arrhythmias and pinpoint abnormal conduction pathways, thereby aiding in the identification of VT substrates. This technique has been widely employed since the early stages of catheter ablation. However, with technological advancements such as three-dimensional mapping systems, it has become evident that VT conduction circuits exhibit three-dimensional characteristics, and there is a relationship between these circuits and delayed conduction properties in substrate mapping. Therefore, it is crucial to utilize mapping systems to visualize and comprehend the VT circuit in three dimensions during catheter treatment. This review provides an overview of the basic knowledge and clinical applications of the pace-mapping method, its limitations, and our findings on estimating three-dimensional VT circuits based on abrupt changes in the pace-mapping waveform caused by conduction delays and barriers within the VT circuit. In addition, we discuss recent insights into the pace-mapping method based on the latest studies.

【Objective】To investigate time series variation and upper limits of ST values in pediatric electrocardiograms through automatic measurement for each lead. 【Methods】The subjects were 100 patients who visited the pediatric cardiology outpatient clinic at our hospital from 2004 to 2023. The patients ranged in age from 1 month to 12 years, with examination intervals from 2 to 436 days. ST values were defined as ST-mid. Measurements were taken twice for each patient, and the absolute difference between the two ST values was considered the ST variation. 【Results】No significant correlation was found between ST variation and examination interval in any of the leads. When comparing three age groups （1-11 months, 1-3 years, and 4-12 years）, ST variation was small in all age groups, with the 4-12 years group showing particularly small variation in limb leads and V6 lead （p=0.001 to 0.01）. The upper limit of variation, represented by the 95th percentile value, was less than 100μV in most age groups and leads, indicating sufficiently small variation. 【Conclusion】In pediatric patients, considering the upper limit of ST value variation for each age and lead allows for the assessment of ST abnormalities over time.

The case was a 63-year-old male admitted to the hospital for a cardiopulmonary arrest in year X-3. Following his resuscitation, an emergency percutaneous coronary intervention was performed on the right coronary artery（RCA）（#3）. In year X, atrial tachycardia（AT）was detected, and initiating a rate control therapy proved ineffective. Following consultation with the patient, he elected to undergo catheter ablation. During the electrophysiological study, an AT with a cycle length of 234 ms was induced. The 3D mapping system revealed an isthmus-dependent figure-of-eight reentrant AT on the left atrial posterior wall（LAPW）with a low voltage area（LVA）. The post-pacing interval near the exit site exceeded the tachycardia cycle length by 6 ms. Ablating that site during the AT terminated the arrhythmia. When investigating the cause of the LVA on the LAPW, in the X-2-year coronary angiography it was found that the LA branch originated from the RCA supplying the LVZ. The X-year cardiac synchronous coronary angiography CT scan revealed that the branch had disappeared, even though other coronary artery branches of a similar size were still present. Based on those findings, we hypothesized that an atrial infarction occurred due to decreased coronary blood flow during the cardiac arrest or the progression of atherosclerosis, serving as one of the contributing factors to the formation of the LVA on the LAPW.

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