Heart rate variability in patients with neurally mediated syncope: Tilt-table and pharmacological testing

doi:10.1016/S0022-0736(95)80023-9

$Journal of Electrocardiology Vol. 28 Supplement S e s s i o n III P o s t e r s Ventricular Response in Atrial Fibrillation is not Chaotic. J-M Gregoire MD, M-P Kestemont Phi), G Destrec. AHEI and ULB-VUB Computing Centre, Brussels, Belgium. Non linearities have been demonstrated in atrial waves and in the comportement of the AV node. Therefore, the aim of this study was to reassess ventricular response in atrial fibrillation (AF) by return maps of RR intervals which are useful tools for revealing non linearties. Material and methods. We digitized successive RR intervals from 24H-ECG recordings of 10 non treated patients with chronical AF. We constructed return maps of RR interval versus the next interval (RRn versus RRn+I) and return maps of the interval variation (DRRn versus ,,~RRn+I). RR intervals randomized according to an Erlang distribution with the same parameters as the patients were generated by a statistical package (ISML). Results. Return maps of RR intervals do not show a disceraable structure within the borders of the effective AV refractory period. All return maps of the interval variation show a trianular structure. The Erlang generated random RR intervals give similar return maps. Conclusions. We found no argument for non linearities in ventricular response to AF. This ventricular response may well be described by an Erlang distribution. ventrieular repolarization (VR). From 24-hour ambulatory ECG data (XYZ cordiguration), wc averaged selectively individual beats preceded by a stable heart rate. Averaged high-quality XYZ templates were: 1) classified according tc their mean preceding RR interval, 25 msee stcpwise and 2) analyzed by a 3D quantitative ECG software, CAVIAR, which calculated QTa and QTe inte~wals. Day and night were processed separately to evaluatethe RD in 2 Holter periods with opposite sympathovagaI balance. Results: DAY NIGHT s(QTa/RR)* 0.1624-0.07 (r2 = 0.92) O.1204-0.04 s(QTe/RR)* 0.1384-0.03 (rTM 0.97) O. 108+0.04 t p<0.05 ns (? = 0.86) "t" p<0.05 :~ slope of the regression line (r~= 0.95) p<0.05 t" paired Wilcoxen test Conclusions: the RD of the VR is modulated by a circadian trend, the diurnal slopes being higher than the nocturnal slopes. The early phase of the VR has a greater rate adaptation than its global duration, but only at day. HEART RATE VARI~ILITY IN N E U R A L L Y M E D I A T E D SYNCOPE: P H A R M A C O L O G I C A L TESTING. P~TIENTS WITH T I L T - T A B L E AND PROBLEMS IN "lrH.~EVALUATION OF THE HIGH FREQUENCY COMPONENT OF HEART RATE POWER SPECTRA IN NEWBORNS Orlow, W. A. Patzak and R. Mrowka Institute of Medical Informatics and Biometry, University Hospital CharitY, Humboldt University of Berlin, 10117 Berlin, Germany J.J. Bailey, NIH, Bethesda, Maryland, USA J.Po Moak, Childrens National Medical Ctr, Washington, D.C., USA. HRV spectra using autoregressive models (Burg method) of pseudodigitized RR interval variability functions are derived from short segments (3-5 min) of ECG data recorded on cassette; center frequencies at 0.1 Hz (LF) and at 0.25 Hz (HF) are readily resolved. Syncope unexplained by cardiovascular or CNS disease may be related to altered autonomic function (i.e. neurally mediated). S u c h patients may faint upon head-upright table-tilt testing (+TT). Five pediatric patients with history of unexplained syncope, but normal cardiac tests including ambulatory ECGs showed a +TT with marked increases of the LF on HRV spectrograms. Intravenous infusion of phenylephrine prevented +TT and markedly lowered the LF baseline and response during TT. These results suggest that infusion of an alphaagonist activates the baroreceptor, thereby decreasing sympathetic influence over heart rate, and prevents the altered autonomic state of the syncopal event from being reached. Power spectral analysis of instantaneous heart rate (IttR) is being used more and more as a tool for the assessmentof the vegetative control of the heart in in~nt& Ill compalison with the situation in adults, infants have higher heart rates (I-IR) and breathing rates (BR). Both facts require particular attention regarding the characteristics of the IHR series ff using the high frequency component (I-IF) of the 1I-I spectrum. Fi~een healthy infants were measared polygraphically from birth up to the sixth month. The INR and the respiratory signal were analysed using FFT based algorithms. From the spectrum I-IF was defined as lying between 0.2 to. 1.5 Hz. During quiet sleep clear peaks at BR can be seen in most spectra of IHR, representing the respiratory sinus arrhythmia (RSA). However, during the second half of the first month of life some infants show ~ spectra without a clear respiratory related peak or with a smaller peak located lower than the BR. The coherence spectra between respiration and IHR demonstrate iusignificam levels in the I-IF region. In these eases the BR is high and the quotient between I-IRand BR is low. The discussion of the results have to include the following points: First, ff the I-INis smaller than the double of the BR the phenomenon of cardiac aliasing occurs. Second, the iustationarity of the IHR fluctuations due to irregular breathing may result in low, widely distributed power. Third, respiration and IlK are deeoupted. The last two points can be found especially during active sleep. The study show, that the use of I-IF for the quantification of RSA is problematic during the second to fourth week of life in healthy infants. Heterogeneity of the Rate Dependence ofVentricular Repolarization from Holter ECG Data. PietTe Maison-Blanche, MD, Jocelyne Fayn, Phi), Paul Rubel, PhD,PhiIippe Coumel, MD, Paris and Lyon, France. In vitro studies have shown that different ventricle tissue types have specific eleetrophysiologie characteristics, such as a greater rate-dependence (RD) of the action potential in the epieardium than in endocardium. However, the contribution of this heterogeneity to surface ECG features is unknown. We compared in 17 young healthy volunteers (22a:3 years) the RD of the initial (QTapex, QTa) and of the global (Q-Tend, QTe) time interval indexes of the Right Bundle Branch Block, ST Segment Elevation and Sudden Death Possible Relation with Arrhythmogenic Right Ventricular Dysplasia. Guy Fontaine, Fernando Rosas Andrade, Malika Bamka, Robert Frank. Hopital Jean Rostand, Ivry, France. A new electrocardiographic syndrome has been recently identified showing a complete right bundle branch block (RBBB) pattera with S'[ segment elevation in a subgroup of patients with apparently normal hearl who could experience sudden death due to ventricular fibrillation.$

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Heart rate variability in patients with neurally mediated syncope: Tilt-table and pharmacological testing

Follow Journal of Electrocardiology , Volume 28 Elsevier – Jan 1, 1995

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Heart rate variability in patients with neurally mediated syncope: Tilt-table and pharmacological testing

Follow Journal of Electrocardiology , Volume 28 Elsevier – Jan 1, 1995

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