Kuchar D L, Thorburn C W, Sammel N L
Aust N Z J Med. 1985 Dec;15(6):697-703.
The cause of syncope is often not determined, despite extensive investigations, yet it is important to identify the high risk group who may be in danger of sudden death due to ventricular arrhythmias. Recent studies have shown that the signal averaged electrocardiogram (SA ECG) can identify low amplitude signals in the terminal portion of the QRS and ST segment (late potentials) recorded from the body surface, which represent areas of delayed conduction in small areas of diseased myocardium in patients with ventricular tachycardia (VT). Sixty-five consecutive patients presenting to hospital with syncope were prospectively evaluated to determine a cause of syncope; this included quantitative analysis of the terminal QRS complex using SA ECG. A cardiac cause of syncope was assigned to 49% of patients, a non-cardiac cause to 20%, and no cause was found in the remaining 31%. Initial history and physical examination established a diagnosis in 14% of patients. A prior history of heart disease was an important indicator to a cardiac cause for syncope. Continuous electrocardiographic monitoring was diagnostic in 23% and the yield for electrophysiological testing (in a selected subgroup) was 40%. Ancillary cardiac and neurological investigations were of little diagnostic value, although they were useful in defining the severity and extent of clinically suspected conditions. SA ECG identified a late potential in 11 of 13 patients with VT, but was normal in all except three of the remaining patients who were not considered to have VT (sensitivity 85%, specificity 94%). We conclude that high frequency analysis of the signal averaged ECG is a reliable non-invasive indicator of syncope due to VT.
尽管进行了广泛的调查，但晕厥的病因往往仍无法确定，然而，识别出可能因室性心律失常而有猝死风险的高危人群很重要。最近的研究表明，信号平均心电图（SA ECG）可以识别从体表记录到的QRS波群和ST段末端部分的低振幅信号（晚电位），这些信号代表室性心动过速（VT）患者病变心肌小区域的传导延迟区域。对连续65例因晕厥入院的患者进行前瞻性评估以确定晕厥病因；这包括使用SA ECG对QRS波群末端进行定量分析。49%的患者晕厥病因被判定为心脏性，20%为非心脏性，其余31%未发现病因。初始病史和体格检查确诊了14%患者的病因。心脏病既往史是晕厥心脏性病因的重要指标。连续心电图监测确诊率为23%，电生理检查（在选定的亚组中）确诊率为40%。辅助性心脏和神经学检查诊断价值不大，尽管它们有助于明确临床疑似疾病的严重程度和范围。SA ECG在13例VT患者中的11例中识别出晚电位，但在其余未被认为患有VT的患者中，除3例异常外均正常（敏感性85%，特异性94%）。我们得出结论，信号平均心电图的高频分析是VT所致晕厥的可靠非侵入性指标。
