[Role of spectral turbulence analysis of ECG in predicting risk of arrhythmia after myocardial infarction]

Abstract

Background: Spectral turbulence analysis (STA) of the signal-averaged electrocardiogram (SAECG) is a recently described frequency-domain analysis evaluating the changes in the wave front velocity in the QRS complex as a whole. In this study we prospectively assessed the role of STA in predicting arrhythmic events [(EA): ventricular tachycardia, ventricular fibrillation and sudden death] relative to ejection fraction (EF), complex ventricular arrhythmias (CVA) on Holter monitoring and site of myocardial infarction (MI) in 266 patients (pts) (209 M; 57 F; mean age 62.3 +/- 10.3)-14 with bundle branch block-surviving an acute MI.

Methods: SAECG was recorded in all pts 13 +/- 3 days after MI. STA was performed by using a PC software implementing the algorithm proposed by Kelen. The conventional parameters of STA (inter-slice correlation mean, inter-slice correlation SD, low-slice correlation ratio and spectral entropy) were calculated separately for each orthogonal lead (X, Y and Z) and their average (X + Y + Z). Ejection fraction was assessed in 241 pts and Holter recordings were analyzed in 195 pts 13 +/- 4 and 13 +/- 5 days after MI, respectively.

Results: During a mean follow-up of 13 +/- 10 months, there were 20 (7.5%) AE: 9 pts had sustained ventricular tachycardia, two had cardiac arrest due to ventricular fibrillation and 9 died suddenly. In 41% of pts STA was abnormal. STA sensitivity was 65%, specificity 61%, positive predictive value 12%, negative predictive value 96%, relative risk (RR) 2.67 (95% confidence bounds = 1.1-6.48; p = 0.023). Sensitivity, specificity, positive predictive value and RR for EF and CVA were 65, 78, 21%, 6.5 and 64, 66, 10%, 3.4, respectively. Abnormal STA was present in 46% of pts with anterior MI and in 42% of pts with inferior MI (ns). Sensitivity, specificity and RR were 88, 58% and 7.95 (p = 0.015) for anterior MI and 50, 59% and 1.41 (p = ns) for inferior MI.

Conclusion: The value of STA of the SAECG is poor when performed two weeks after MI. STA theoretical advantages over time-domain analysis of the SAECG were not verified in our study.