Copie X, Blankoff I, Fei L, Murgatroyd F D, Hnatkova K, Malik M, Camm A J
Service de cardiologie A, hôpital Broussais, Paris.
Arch Mal Coeur Vaiss. 1996 Mar;89(3):325-30.
The reproducibility of the parameters defining the presence of late potentials on the signal-averaged electrocardiogram is one of the limiting factors of the method. The authors studied the coefficients of correlation and reproducibility of these parameters in patients with coronary artery disease. In addition, they tried to determine which parameter was most often responsible for changing a diagnostic conclusion (i.e., presence or absence of late potentials). Two signal-averaged ECGs were recorded one after the other in 127 patients. The presence of late potentials was defined as the presence of a least two of the following criteria: total amplified and averaged QRS duration (tQRS) > 114 ms: duration of the last signal of under 40 microV (LAS) > 38 ms, and root mean square of the amplitude of the last 40 ms (RMS) < 20 microV. The correlation coefficients were 0.98, 0.96 and 0.94 for the duration of tQRS, LAS and RMS respectively (p < 0.0001). The coefficients of reproducibility were 7.0 ms. 7.0 ms and 16.1 microV respectively. Late potentials were present in 22% of patients. A change in diagnosis between the first and second recording was observed in 10 subjects (8% of the population). A combined change in LAS and RMS was responsible for 6 of these revised diagnoses, a change in LAS alone in 2 cases, of the RMS alone in 1 case and the tQRS alone in 1 case. In patients with coronary artery disease, the immediate reproducibility of the diagnosis of late potentials is affected by changes in LAS and RMS. The tQRS is only rarely responsible for a change in diagnosis. This study suggests that the result of the signal-averaged ECG should be interpreted with caution when the LAS or RMS are near their threshold values.
信号平均心电图上定义晚电位存在的参数的可重复性是该方法的限制因素之一。作者研究了这些参数在冠心病患者中的相关性系数和可重复性。此外，他们试图确定哪个参数最常导致诊断结论的改变（即晚电位的存在或不存在）。在127例患者中依次记录了两份信号平均心电图。晚电位的存在定义为至少满足以下两项标准：总放大平均QRS时限（tQRS）>114 ms；最后信号持续时间<40 μV（LAS）>38 ms；最后40 ms振幅的均方根（RMS）<20 μV。tQRS、LAS和RMS持续时间的相关系数分别为0.98、0.96和0.94（p<0.0001）。可重复性系数分别为7.0 ms、7.0 ms和16.1 μV。22%的患者存在晚电位。在10名受试者（占总人数的8%）中观察到首次和第二次记录之间的诊断变化。LAS和RMS的联合变化导致了其中6例诊断的改变，仅LAS改变2例，仅RMS改变1例，仅tQRS改变1例。在冠心病患者中，晚电位诊断的即时可重复性受LAS和RMS变化的影响。tQRS很少导致诊断改变。这项研究表明，当LAS或RMS接近其阈值时，信号平均心电图的结果应谨慎解释。
