Intra-individual ECG changes over 25 years: How long can elective ECGs be used as reference for acute ischemia detection?

• Published in: Journal of electrocardiology 2015-07, Vol.48 (4), p.490-497
• Main Authors: De Jongh, Marjolein C., BSc, Ter Haar, C. Cato, BSc, Man, Sumche, MD, Treskes, Roderick W., BSc, Maan, Arie C., PhD, Schalij, Martin J., MD, PhD, Swenne, Cees A., PhD
• Format: Article
• Language: English
• Subjects: Acute Disease; Adult; Aged; Aged, 80 and over; Aging - physiology; Cardiovascular; Electrocardiography - methods; Female; Heart Rate - physiology; Humans; Male; Middle Aged; Myocardial Ischemia - diagnosis; Myocardial Ischemia - physiopathology; Netherlands - epidemiology; Reference Values; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 0022-0736; 1532-8430
• DOI: 10.1016/j.jelectrocard.2015.04.007

Abstract Background The guidelines advocate, in patients with chest pain, comparison of the acute ECG with a previously made, non-ischemic ECG that serves as a reference, to corroborate the working diagnosis of acute coronary syndrome (ACS). Our approach of this serial comparison is to compute the differences between the ST vectors at the J point and 60 ms thereafter (∆ST (J + 0) , ∆ST (J + 60) ) and between the ventricular gradient (VG) vectors (∆VG). In the current study, we investigate if reference ECGs remain valid in time. Methods We studied 6 elective non-ischemic ECGs (ECG0 , ECG1 , …, ECG5 ), 5 years apart, in 88 patients. Within each patient, serial comparisons were done 1) between all successive ECGs, and 2) between each of ECG1 , ECG2 , …, ECG5 and ECG0 , computing, in addition to ∆ST (J + 0) , ∆ST (J + 60) and ∆VG, the difference in heart rates, ∆HR. Additionally, relevant clinical events and the diagnoses associated with each ECG were collected. Linear regression was used to assess trends in ∆ST (J + 0) , ∆ST (J + 60) and ∆VG; multiple linear regression was used to assess the influence of the clinical events and diagnoses on ∆ST (J + 0) , ∆ST (J + 60) and ∆VG. Results There were no trends in the differences between successive ECGs. Positive trends were seen with increasing time lapses between ECGs: ∆ST (J + 0) , ∆ST (J + 60) and ∆VG increased per year by 0.65 μV, 1.45 μV and 3.69 mV∙ms, respectively. Extrapolation to a time lapse of 0 yielded 50.92 μV, 36.63 μV and 20.91 mV∙ms for the short-term reproducibility of ∆ST (J + 0) , ∆ST (J + 60) and ∆VG, respectively. Multiple linear regression revealed that clinical variables could explain only 10%, 17% and 13% of the variability in ∆ST (J + 0) , ∆ST (J + 60) and ∆VG, respectively. Conclusion With a view on ischemia detection thresholds in the order of magnitude of 58 μV for ∆ST and 26 mV·ms for ∆VG, our study suggests that it is important to have a recent ECG available for the detection of myocardial ischemia, as an “aged” ECG may have lost its validity as a reference.