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Home    Πρόπτωση μιτροειδούς: Μελέτη της συμπεριφοράς του αυτόνομου νευρικού συστήματος και η προγνωστική σημασία της ανεπάρκειας της βαλβίδας  

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Identifier uch.med.phd//2002DIS0502
Title Πρόπτωση μιτροειδούς: Μελέτη της συμπεριφοράς του αυτόνομου νευρικού συστήματος και η προγνωστική σημασία της ανεπάρκειας της βαλβίδας
Author Ζουριδάκης, Εμμανουήλ Γ
Abstract There is evidence that autonomic nervous system abnormalities play a significant role in the pathophysiology of mitral valve prolapse syndrome. It remains, however, unclear which is the exact role of the sympathetic and parasympathetic activity and their interaction, not only in the development of patients’ symptoms but also in the modification of the myocardial electrophysiological properties and repolarization, which could lead to severe ventricular arrhythmias. Furthermore, it is still unknown, whether these electrophysiological abnormalities are related to the echocardiographic degree of prolapse and the presence of mitral regurgitation. The aim of our first study was to assess the autonomic activity in patients with mitral valve prolapse, by measuring the indexes of heart rate variability, and to investigate its relation to the patients’ symptoms. Our results showed a significant dysautonomia, which was apparent in the whole population of the mitral valve prolapse patients and was characterized by a predominance of the sympathetic tone. These abnormalities were far more profound in symptomatic patients. In our second study we sought to investigate the role of autonomic activity in the daily variation of myocardial repolarization, as assessed by QT interval measurement, in patients with mitral valve prolapse and to examine the association between QT variability and ventricular arrhythmogenesis. We found that both QT and its heart rate-corrected value varied significantly during the day and this variation was dependent on the changes of autonomic tone. Moreover, our results showed that the magnitude and quality of QT variability was significantly associated with the occurrence of complex ventricular arrhythmias. The aim of our following study was to examine the relation between the severity of prolapse and mitral leaflet thickness, and repolarization characteristics in these patients. The dispersion of QT interval and other electrocardiographic indexes, which reflect the heterogeneity of ventricular repolarization, were found significantly increased in patients with the most severe degree of prolapse compared to the milder cases. Multivariate analysis revealed that the degree of the prolapse and the anterior mitral leaflet thickness were the only factors independently associated with QT dispersion. Finally, we investigated whether isometric exercise in patients with mitral valve prolapse can induce mitral regurgitation, which is not apparent at rest, and to assess the prognostic significance of such a finding. Our results showed that a significant proportion of these patients develop mitral regurgitation during isometric exercise which may undergo undetected at rest. Moreover, we found that the rate of adverse events during follow-up was significantly higher in patients with than in those without exercise-induced mitral regurgitation. In conclusion, our findings indicate that autonomic tone abnormalities play an important role in the development of symptoms in patients with mitral valve prolapse and are also involved in the mechanisms underlying the increased ventricular arrhytmogenesis observed in this population. Furthermore, the echocardiograhic assessment of the severity of the prolapse, and the anatomic and functional characteristics of the valve, both at rest and during isometric exercise, may help to identify a subgroup of patients at high risk of future adverse events who deserve closer follow-up.
Language Greek
Issue date 2002-05-01
Collection   School/Department--School of Medicine--Department of Medicine--Doctoral theses
  Type of Work--Doctoral theses
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