Complexity of the dynamic QT variability and RR variability in patients with acute anterior wall myocardial...

QT and RR intervals' fluctuations are implicated in the development of malignant arrhythmias. Recent research has quantified repolarization lability using stochastic and linear methods. However, QT-RR intervals are nonlinearly coupled. To this end, QT and RR intervals were extracted from twenty four patients with acute myocardial infarction (AMI) and 13 controls, and a measure of local dimensional complexity (pointwise correlation dimension, PD2) was calculated. PD2 of QT intervals was significantly higher for the patients than for controls (4.83 +/- 0.81 versus 3.40 +/- 0.76, P =.0001), and vice versa for RR intervals (2.51 +/- 0.62 versus 2.91 +/- 0.42, P =.028). The RR and QT measures of complexity were highly correlated only among controls (r = 0.769, P =.0021). Our results support the presence of autonomic abnormalities during infarction and might complement existing tools for assessment of increased risk for sudden death after AMI.