Aging and cardiovascular complexity: effect of the length of RR tachograms

As we age, our hearts undergo changes that result in a reduction in complexity of physiological interactions between different control mechanisms. This results in a potential risk of cardiovascular diseases which are the number one cause of death globally. Since cardiac signals are nonstationary and nonlinear in nature, complexity measures are better suited to handle such data. In this study, three complexity measures are used, namely Lempel–Ziv complexity (LZ), Sample Entropy (SampEn) and Effort-To-Compress (ETC). We determined the minimum length of RR tachogram required for characterizing complexity of healthy young and healthy old hearts. All the three measures indicated significantly lower complexity values for older subjects than younger ones. However, the minimum length of heart-beat interval data needed differs for the three measures, with LZ and ETC needing as low as 10 samples, whereas SampEn requires at least 80 samples. Our study indicates that complexity measures such as LZ and ETC are good candidates for the analysis of cardiovascular dynamics since they are able to work with very short RR tachograms

Reconstituted High-Density Lipoprotein Shortens Cardiac Repolarization

Objectives We hypothesize that increasing high-density lipoprotein cholesterol (HDL-C) shortens cardiac repolarization. Background HDL-C is inversely associated with sudden death. The relation between HDL-C and repolarization of the heart is unexplored. Methods HDL-C was elevated with reconstituted high-density lipoprotein (rHDL). Cardiac repolarization was studied by recording cardiac transmembrane potentials with the patch clamp technique from isolated rabbit cardiomyocytes that were superfused with rHDL. Infusions with rHDL (40 mg/kg body weight) were performed in dyslipidemic patients and healthy volunteers. Electrocardiograms were recorded to assess cardiac repolarization before and 24 h after infusion with rHDL. Results rHDL as well as purified human apolipoprotein AI shortened repolarization of isolated rabbit cardiomyocytes by similar to 25% (p <0.05). rHDL infusion shortened the heart rate-corrected QT interval on surface electrocardiograms in all participants (p <0.001). Conclusions rHDL shortens cardiac repolarization. These data provide evidence for a novel mechanism of HDL infusion that may contribute to reduction of sudden cardiac death. (J Am Coll Cardiol 2011;58:40-4) (C) 2011 by the American College of Cardiology Foundatio

A framework for the atrial fibrillation prediction in electrophysiological studies

Background and objective Cardiac arrhythmias are disorders in terms of speed or rhythm in the heart's electrical system. Atrial fibrillation (AFib) is the most common sustained arrhythmia that affects a large number of persons. Electrophysiologic study (EPS) procedures are used to study fibrillation in patients; they consist of inducing a controlled fibrillation in surgical room to analyze electrical heart reactions or to decide for implanting medical devices (i.e., pacemaker). Nevertheless, the spontaneous induction may generate an undesired AFib, which may induce risk for patient and thus a critical issue for physicians. We study the unexpected AFib onset, aiming to identify signal patterns occurring in time interval preceding an event of spontaneous (i.e., not inducted) fibrillation. Profiling such signal patterns allowed to design and implement an AFib prediction algorithm able to early identify a spontaneous fibrillation. The objective is to increase the reliability of EPS procedures. Methods We gathered data signals collected by a General Electric Healthcare's CardioLab electrophysiology recording system (i.e., a polygraph). We extracted superficial and intracavitary cardiac signals regarding 50 different patients studied at the University Magna Graecia Cardiology Department. By studying waveform (i.e., amplitude and energy) of intracavitary signals before the onset of the arrhythmia, we were able to define patterns related to AFib onsets that are side effects of an inducted fibrillation. Results A framework for atrial fibrillation prediction during electrophysiological studies has been developed. It includes a prediction algorithm to alert an upcoming AFib onset. Tests have been performed on an intracavitary cardiac signals data set, related to patients studied in electrophysiological room. Also, results have been validated by the clinicians, proving that the framework can be useful in case of integration with the polygraph, helping physicians in managing and controlling of patient status during EPS