Giampiero Merati, Sonia
Allibardi, Vittoria Margonato, Arsenio Veicsteinas, Michele Samaja, Bruno Caru.
Universita degli Studi di Milano, Brescia, and CNR, Italy
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As cardiac arrhythmias are often associated with poor
postischemic recovery and sudden death after infarction, the mechanisms underlying
arrhythmogenesis are receiving particular attention in experimental and clinical settings1-3. Analysis of heart rate variability (HRV) from ECG
date may be a convenient way to find out risk predictors of post-ischemic arrhythmias.
Indeed, a reduced HRV is associated with increased risk of adverse events in
post-infarcted subjects4.
There are two main factors underlying the ischemic event: reduced coronary flow and
reduced O2 supply. In an experimental model of ischemia-reperfusion free of the
endogenous and nervous determinants of arrhythmias, e.g. isolated perfused hearts, the
recovery of mechanical performance depends on flow, whilst the development of
arrhythmogenesis depends on O2 supply5. That
model appears therefore suitable for a preliminary evaluation of the possibility to
predict postischemic dysfunction from HRV analysis. The aim of this study is to examine
the relationship between the intrinsic source of HRV and the recovery of performance
following low-flow ischemia. To distinguish the separate effects of the two components of
the ischemic event on HRV and recovery, we used two groups of hearts, that were different
for the type of the insult (low-flow, normal PO2; high-flow, low PO2) at the
same total O2 supply (flow • PO2). To assess HRV as predictor of
myocardial recovery from ischemia or hypoxia, we used a non-linear dynamics analysis
(fractal dimension, FD), which appeared convenient because FD predicts arrhythmias
recurrence in patients being treated for life-threatening ventricular arrhythmias6.
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