Vico Baier

Heart Rate Variability, Blood Pressure Variability, and Baroreflex Sensitivity in Overtrained Athletes

Objective:To assess the effects of abruptly intensified physical training on cardiovascular control. Design:Retrospective longitudinal study. Setting:Research laboratory. Participants:Ten healthy athletes (5 men and 5 women) from track and field as well as triathlon. Interventions:A 2-week training camp, including daily stepwise increasing cycling tests, running of 40 minutes, and additional cycling of 60 minutes. Main Outcome Measurements:Time and frequency domain parameters of resting heart rate and blood pressure variability (HRV and BPV) and baroreflex sensitivity (BRS), before, during, and after the training camp. Results:We found significantly reduced HRV during the training camp (mean beat-to-beat interval: 1042 [937 to 1194] ms vs. 933 [832 to 1103] ms vs. 1055 [947 to 1183] ms, P < 0.01; root-mean-square of beat-to-beat interval differences: 68 [52 to 95] ms vs. 52 [38 to 71] ms vs. 61 [48 to 78] ms, P < 0.05). Further, BRS was significantly reduced: 25.2 (20.4 to 40.4) ms/mmHg vs. 17.0 (12.9 to 25.7) ms/mmHg vs. 25.7 (18.8 to 29.1) ms/mmHg, P < 0.05. These effects disappeared at a large degree after 3 to 4 days of recovery. Conclusion:Abruptly intensified physical training results in an altered autonomic cardiovascular activity towards parasympathetic inhibition and sympathetic activation that can be monitored by means of HRV and BRS analyses and might provide useful markers to avoid the overtraining syndrome.

Postextrasystolic regulation patterns of blood pressure and heart rate in patients with idiopathic dilated cardiomyopathy

Assessment of fluctuations in heart rate (HR) following a premature ventricular complex (PVC) is valuable for identifying patients at high risk of sudden cardiac death. We hypothesised that postextrasystolic potentiation is the main determinant of the regulation patterns of blood pressure (BP) and HR following a PVC. Twelve patients with idiopathic dilated cardiomyopathy (IDC) and 13 control subjects with single PVCs (comparable coupling intervals) were investigated. Non‐invasive finger arterial BP and ECGs were analysed. Regulation patterns following a single PVC were quantified using the indices postextrasystolic amplitude potentiation (PEAP) and maximum turbulence slope of five consecutive mean BP values (MBP‐TS), and compared with the HR turbulence parameters turbulence slope (HR‐TS) and turbulence onset (HR‐TO). PEAP was significantly higher in IDC patients compared to controls (48.7 ± 32.6 vs. 9.8 ± 5.4 %, P < 0.01), whereas MBP‐TS was lower (0.97 ± 0.60 vs. 2.07 ± 1.04 mmHg BBI−1 (BBI, beat‐to‐beat interval), P < 0.05), as was HR‐TS (8.46 ± 7.90 vs. 30.73 ± 22.90 ms BBI−1, P < 0.01). HR‐TO was significantly higher in IDC patients (−0.56 ± 2.19 vs.−5.52 ± 4.13 %, P < 0.01). In addition, the regulation patterns of BP and HR following a single PVC differed significantly between IDC patients and controls. Specifically, we observed pronounced PEAPs in IDC patients. The baroreflex response initiated by the low pressure amplitude of the PVC was suppressed in IDC patients due to the augmented potentiation of the first postextrasystolic blood pressure. Furthermore, IDC patients displayed impressive postextrasystolic pulsus alternans phenomena, whereas healthy subjects exhibited a typical baroreflex pattern. The pulsus alternans phenomenon seems to be triggered by a PVC.

Short- and long-term joint symbolic dynamics of heart rate and blood pressure in dilated cardiomyopathy

Autonomic cardiovascular control involves complex interactions of heart rate and blood pressure. In patients with dilated cardiomyopathy (DCM), this control is impaired and parameters for its quantification might be of prognostic importance. In this paper, we introduce methods based on joint symbolic dynamics (JSD) for the enhanced analysis of heart rate and blood pressure interactions. To assess the coarse-grained dynamics beat-to-beat changes of heart rate and blood pressure are encoded in symbol strings. Subsequently, the distribution properties of short symbol sequences (words) as well as the scaling properties of the whole symbol string are assessed. The comparison of joint symbolic heart rate and blood pressure dynamics in DCM (n=75) with those in healthy controls (n=75) showed significant changes. Both, the distribution of words and the scaling properties indicate a loss in heart rate dynamics associated with blood pressure regulation in DCM. In conclusion, the analyses of short- and long-term JSDs provide insights into complex physiological heart rate and blood pressure interactions and furthermore reveal patho-physiological cardiovascular control in DCM.

Smelling Renal Dysfunction via Electronic Nose

The human body odor plays an important role in social communication in various situations, like the olfactory identification of partners and relatives as well as in parents–child interactions. In patients with renal dysfunction the compound of sweat and volatile gases is changed because of the limited ability for removing metabolic products from the blood. The regulation of electrolyte composition and acid–base balance are also altered so that the body odor of these patients may be significantly influenced by these disorders. We show the ability of an electronic nose to detect changes in the human body odor in consequence of renal dysfunction by reducing multivariate sensor signals with principal component analysis to its first and second principal odor component (POC). All healthy subjects could clearly be distinguished from patients with renal failure using quadratic discriminant analysis, whereas a correct classification of 95.2% (98.4% using 1st–3rd POC) of patients between end stage renal failure and chronic renal failure was found. This methodology of analyzing human body odor may also provide new approaches for investigating symptoms of renal failure and for diagnosing other diseases of internal or cutaneous origin.

ESTIMATING THE COMPLEXITY OF HEART RATE FLUCTUATIONS — AN APPROACH BASED ON COMPRESSION ENTROPY

Heart rate exhibits spontaneous fluctuations that are mainly modulated by control loops within the autonomic nervous system. Assessing the dynamics of heart rate fluctuations can provide valuable information about regulatory processes and patho-physiological behavior. In this paper heart rate fluctuations and its entropy are assessed using an algorithmic information theoretic concept applying a data compressor. First, the beat-to-beat fluctuations of heart rate are binary coded for decreases and increases, respectively. Subsequently, those symbol sequences are compressed using the LZ77 algorithm. The ratio of the length of the compressed sequences to the original length is used as an estimate of entropy. We investigated the compressibility of heart rate fluctuations in athletes before, during, and after a training camp. Heart rate time series were obtained from ECGs recorded over 30 minutes under supine resting conditions. We found a significant entropy reduction during the training camp, reflecting the effects of physical fatigue. In conclusion, the compression entropy seems to be a suitable approach to assess the complexity of heart rate fluctuations.

Kardiorespiratorische Desynchronisation nach akutem Myokardinfarkt

The prognosis of cardiac diseases can be estimated from the variability of regulation parameters of the cardiovascular system. Changes in the variability of a regulation parameter causes disturbances in the synchronisation of interacting control loops. Conclusions about the severity of the underlying functional impairment can be drawn from these disturbances. This study investigates the synchronisation of the control loops of the heart rate and respiration (cardiorespiratory synchronisation, CRS) after acute myocardial infarction.    We investigated 43 patients after myocardial infarction and 27 healthy controls. To quantify the CRS the synchronisation in phase of respiration and heart rate was assessed. The heart rate variability (HRV) was also assessed. Patients after myocardial infarction have a significantly reduced HRV and CRS. There is a non-linear relationship between HRV and CRS. Patients with left ventricular enlargement and reduced left ventricular ejection fraction (≤45%) significantly differed from the other infarct patients and controls in CRS but not in HRV. They had a marked degree of cardiorespiratory desynchronisation and were identified by a threshold value.    CRS is a measure of the interaction of respiration control and heart rate control. After myocardial infarction, a reduction of the HRV can be observed. The desynchronisation of the control loops of respiration and heart rate especially appears in large infarcts. This can be quantitatively assessed by the method presented. Die Variabilität von Regulationsgrößen des Herz-Kreislauf-Systems erlaubt Aussagen über die Prognose kardialer Erkrankungen. Die veränderte Variabilität einer Regulationsgröße führt zu Störungen in der Synchronisation interagierender Regelkreise. Die Quantifizierung dieser Störungen könnte Rückschlüsse auf die Schwere der zugrunde liegenden funktionellen Beeinträchtigung erlauben. Diese Studie untersucht die Synchronisation der Regelkreise von Herzfrequenz und Atmung (kardiorespiratorische Synchronisation, CRS) nach akutem Myokardinfarkt.    Es wurden 43 Patienten nach Myokardinfarkt und 27 Gesunde untersucht. Zur Quantifizierung der CRS wurde die Phasensynchronisation von Atemfrequenz und Herzfrequenz beurteilt. Ebenfalls wurden die Parameter der Herzfrequenzvariabilität (HRV) untersucht. Patienten nach Myokardinfarkt haben eine signifikant reduzierte HRV und CRS. Zwischen HRV und CRS besteht eine nichtlineare Abhängigkeit. Infarktpatienten mit linksventrikulärer Dilatation und eingeschränkter linksventrikulärer Pumpfunktion (EF≤45%) unterschieden sich in dieser Studie in der CRS, nicht aber in der HRV von den übrigen Infarktpatienten und Gesunden. Sie hatten eine ausgeprägte kardiorespiratorische Desynchronisation und konnten durch einen Schwellwert identifiziert werden.    Die CRS erfasst die Interaktionen von Herzfrequenz- und Atemregulation. Nach Myokardinfarkt kommt es zu einer Reduktion der HRV. Eine Desynchronisation der Regelkreise von Atmung und Herzfrequenz tritt offenbar insbesondere bei ausgedehnteren Myokardinfarkten ein. Dies kann mit der vorgestellten Methode quantifiziert werden.

Hidden Markov models based on symbolic dynamics for statistical modeling of cardiovascular control in hypertensive pregnancy disorders

Discrete hidden Markov models (HMMs) were applied to classify pregnancy disorders. The observation sequence was generated by transforming RR and systolic blood pressure time series using symbolic dynamics. Time series were recorded from 15 women with pregnancy-induced hypertension, 34 with preeclampsia and 41 controls beyond 30th gestational week. HMMs with five to ten hidden states were found to be sufficient to characterize different blood pressure variability, whereas significant classification in RR-based HMMs was found using fifteen hidden states. Pregnancy disorders preeclampsia and pregnancy induced hypertension revealed different patho-physiological autonomous regulation supposing different etiology of both disorders.

Alternans of blood pressure and heart rate in dilated cardiomyopathy.

LEDER, U., et al.: Alternans of Blood Pressure and Heart Rate in Dilated Cardiomyopathy. Impaired myocardial performance is known to be associated with electrical and mechanical beat‐to‐beat alternans phenomena. The alternans in blood pressure and heart rate and their interdependency in idiopathic dilated cardiomyopathy (IDC) were studied. The arterial blood pressure and the electrocardiograph (ECG) were continuously recorded in 22 patients suffering from IDC (age 49 ± 13 years, ejection fraction 0.33 ± 0.13, left ventricular diameter of 67 ± 8 mm) and in 21 healthy controls (age 52 ± 15 years). The beat‐to‐beat variations of the interbeat intervals (IBI) and of the blood pressure amplitudes (AMP) were measured. An alternans beat was defined as a beat preceded and followed by beats that had higher or lower values in the respective modality. The percentages of singular and repetitive alternans patterns, and the interdependency of the alternans patterns in AMP and IBI were assessed. The study found significantly more singular and repetitive alternans patterns in the IDC group compared to the control group both in the analysis of AMP and IBI (singular alternans in IBI: 55 ± 11 vs 47 ± 7%, P < 0.01; singular alternans in AMP: 61 ± 15 vs 45 ± 6%, P < 0.01; triple alternans in IBI: 29 ± 18 vs 16 ± 9%, P < 0.01; triple alternans in AMP: 34 ± 24 vs 12 ± 7%, P < 0.01). The amplitudes of the AMP alternans patterns were higher in IDC compared to controls (9 ± 7 vs 4 ± 2% of AMP, P = 0.01) whereas they did not differ in IBI. The correlation analysis revealed a significant interdependency of the alternans pattern in IBI and AMP in 18 of 22 IDC patients and in 12 of 21 controls (r = 0.50 ± 0.21 [IDC]; r = 0.26 ± 0.05 [controls]). The slope of the linear regression (ΔAMP vs ΔIBI) was steeper in the IDC group compared to the control group (62 ± 50 vs 20 ± 22 mmHg/s, P < 0.01). The percentages of alternans patterns appearing in IBI and AMP were positively correlated to the left ventricular diameter (r = 0.70 in the IBI, and r = 0.30 in the AMP). The blood pressure amplitude and the heart rate did not differ between the two groups. Patients suffering from IDC have a higher prevalence, stability, amplitude, and interdependency of alternans patterns in IBI and AMP compared to the control group. The amount of alternans patterns indicates the stage of disease. The alternans analysis may have impact on the functional assessment of patients suffering from heart failure.

Altered Autonomic Cardiac Control Predicts Restenosis After Percutaneous Coronary Intervention

Background: Early and late restenosis in up to 30% remains a major problem for long‐term success after percutaneous coronary intervention (PCI). Compared to bare metal stents, the use of drug‐eluting stents reduces restenosis below 10%, but implant coasts have to be considered. In restenosis noninvasive testing lacks diagnostic power. We applied a new approach to identify patients with a high risk for restenosis after PCI by combining heart rate (HR) and blood pressure variability (BPV) analyses.

LONG-TERM CORRELATIONS AND FRACTAL DIMENSION OF BEAT-TO-BEAT BLOOD PRESSURE DYNAMICS

Arterial blood pressure is modulated by several physiological regulatory processes. The analysis of beat-to-beat blood pressure dynamics provides information about cardiovascular control and patho-physiological conditions. In this paper we investigated the long-term correlations and fractal dimension of systolic blood pressure time series applying detrended fluctuation analysis (DFA) and Higuchis algorithm (HFD). Thirty-minute blood pressure recordings in 25 patients with dilated cardiomyopathy (DCM) and 27 healthy controls (CON) were analyzed. The DFA and HFD revealed multifractal features in the blood pressure dynamics of CON as well as of DCM. At small scales, DFA and HFD of CON were significantly different from those of CON, reflecting patho-physiological changes. In conclusion, scaling analysis of blood pressure dynamics might lead to an enhanced assessment of autonomic cardiovascular control in patients with DCM.