Finally, a clear dependence of APC from hypoxemia and hypercarbia has been found (Table 7). Previous studies suggested that such arrhythmias can be a hallmark of COPD. The well-known different prognostic meaning of VPC and APC can be regarded as a confirmation for the quite different prediction models owing to the two types of arrhythmias. 
In conclusion, our results confirm some previous studies, but within an experimental framework free from confounding factors as the use of cardioactive drugs and coexistent arrhythmogenic diseases. The demonstration of some predictability of VPC from the PFR value may be relevant to the understanding of arrhythmogenic mechanism in COPD. However, both myocardial perfusion and right ventricular kinetics should be investigated in an attempt to identify any possible correlate of left ventricular diastolic dysfunction as well as to evaluate the arrhythmogenic role potentially played by silent myocardial ischemia. Furthermore, the recently stressed evidence that mechanical dysfunction can be in itself arrhythmogenic represents an additional reason for an in-depth assessment of right ventricular kinetics. Thus, further studies are necessary to define a better predictive model as well as to understand the physiologic relationships of variables identified by the statistical analysis. birth control pills