MRI-detected brain lesions in AF patients without further stroke risk factors undergoing ablation - a retrospective analysis of prospective studies.

BACKGROUND: Atrial fibrillation (AF) without other stroke risk factors is assumed to have a low annual stroke risk comparable to patients without AF. Therefore, current clinical guidelines do not recommend oral anticoagulation for stroke prevention of AF in patients without stroke risk factors. We analyzed brain magnetic resonance imaging (MRI) imaging to estimate the rate of clinically inapparent ("silent") ischemic brain lesions in these patients. METHODS: We pooled individual patient-level data from three prospective studies comprising stroke-free patients with symptomatic AF. All study patients underwent brain MRI within 24-48 h before planned left atrial catheter ablation. MRIs were analyzed by a neuroradiologist blinded to clinical data. RESULTS: In total, 175 patients (median age 60 (IQR 54-67) years, 32% female, median CHA2DS2-VASc = 1 (IQR 0-2), 33% persistent AF) were included. In AF patients without or with at least one stroke risk factor, at least one silent ischemic brain lesion was observed in 4 (8%) out of 48 and 10 (8%) out of 127 patients, respectively (p > 0.99). Presence of silent ischemic brain lesions was related to age (p = 0.03) but not to AF pattern (p = 0.77). At least one cerebral microbleed was detected in 5 (13%) out of 30 AF patients without stroke risk factors and 25 (25%) out of 108 AF patients with stroke risk factors (p = 0.2). Presence of cerebral microbleeds was related to male sex (p = 0.04) or peripheral artery occlusive disease (p = 0.03). CONCLUSION: In patients with symptomatic AF scheduled for ablation, brain MRI detected silent ischemic brain lesions in approximately one in 12 patients, and microbleeds in one in 5 patients. The prevalence of silent ischemic brain lesions did not differ in AF patients with or without further stroke risk factors.

Wire- and needle potentials facilitating transseptal puncture.

BACKGROUND: Transseptal puncture for left heart interventions became a routine procedure guided by fluoroscopy and echocardiography. The use of intracardiac potentials derived from the sheath-transseptal-needle/guidewire-combination may provide helpful information to increase safety of this procedure. METHODS AND RESULTS: We recorded the intracardiac potentials from the sheath-transseptal-needle/guidewire-combination during the transseptal puncture procedure in 31 consecutive patients (mean age 67.2±8.2years; 21 in sinus rhythm, 10 in atrial fibrillation) designated for ablation of atrial fibrillation by the Cryo-balloon ® technique (Medtronic, Minnesota, USA). The EP-Navigator ® 3-D-image integration tool (Philips Healthcare, Hamburg, Germany) was used for visualization of the device position in relation to the cardiac structures. Typical and reproducible potentials could be derived in all patients for the different device localizations at transseptal puncture procedure. Especially the transition from the muscular interatrial septum into the fossa ovalis could be easily depicted by the changes of both morphology and magnitude of the atrial signal (6.1±2.3mV in sinus rhythm [SR]/3.5±0.9mV in atrial fibrillation [AF] at the muscular interatrial septum and 0.5±0.2mV in SR/0.5±0.1mV in AF in the fossa ovalis). CONCLUSIONS: The crucial steps of a transseptal procedure can be verified by typical changes (morphology and amplitude) of the intracardiac signals derived from the sheath-transseptal-needle/guidewire-combination in patients with sinus rhythm as well as in atrial fibrillation.

3 Tesla MRI-detected brain lesions after pulmonary vein isolation for atrial fibrillation: results of the MACPAF study.

BACKGROUND: Left atrial catheter ablation (LACA) is an established therapeutic approach to abolish symptomatic atrial fibrillation (AF). OBJECTIVE: Based on the prospective MACPAF study (clinicaltrials.gov NCT01061931) we report the rate of ischemic brain lesions postablation and their impact on cognitive function. METHODS: Patients with symptomatic paroxysmal AF were randomized to LACA using the Arctic Front® or the HD Mesh Ablator® catheter. All patients underwent brain MRI at 3 Tesla, neurological, and neuropsychological examinations within 48 hours prior and after the ablation procedure. RESULTS: There was no clinically evident stroke in 37 patients (mean age 62.4 ± 8.4 years; 41% female; median CHADS2 score 1 [IQR 0-2]) after LACA but high-resolution diffusion-weighted imaging (DWI) detected new ischemic lesions in 15 (41%) patients after LACA. Four (27%) of the HD Mesh Ablator® patients and 11 (50%) of the Arctic Front® patients suffered a silent ischemic lesion (P = 0.19). In these 15 patients, there was a nonsignificant trend toward lower cardiac ejection fraction (P = 0.07) and AF episodes during LACA (P = 0.09), while activated clotting time levels, number of energy applications, periprocedural electrocardioversion or CHADS(2) score had no impact. Lesion volumes varied from 5 to 150 mm(3) and 1 to 5 lesions were detected per patient. However, acute brain lesions had no effect on cognitive performance immediately after LACA. Of the DWI lesions postablation 82% were not detectable on FLAIR images 6-9 months postablation. CONCLUSIONS: According to 3 Tesla high-resolution DWI, ischemic brain lesions after LACA were common but not associated with impaired cognitive function after the ablation procedure.

Clinical efficacy and safety of an implantable cardioverter-defibrillator lead with a floating atrial sensing dipole.

BACKGROUND: The concept of a single-lead implantable cardioverter-defibrillator (ICD), with a floating dipole, has been proven safe and functional. METHODS AND RESULTS: The studied active-fixation, steroid-eluting lead (Linox(smart) S DX, BIOTRONIK SE & Co KG, Berlin, Germany) is one French thinner than its predecessor and coated with lubricious SilGlide to improve lead handling. A dedicated ICD device has a self-adaptive atrial input stage including a fourfold amplifier. The amplification, filtering, and adapted atrial input stage are located in the Lumax 540 VR-T DX (BIOTRONIK). The Linox(smart) S DX ICD lead delivers only the signal. The lead was evaluated during implantation; at predischarge; and 1-, 3-, and 6-month follow-up examinations. The primary endpoint (efficacy) was the rate of appropriate atrial sensing tests. The secondary endpoint (safety) was freedom from lead-related invasive reinterventions. Both safety and efficacy were expected to be significantly higher than 90%. The study enrolled 116 patients at 25 clinical sites. Skin-to-skin operation time was 52.4 ± 26.2 minutes. The investigators graded lead insertion as "easy" in 87% of patients. Mean P-wave amplitudes (preamplified) varied from 5.0 to 6.1 mV in different body positions. Both primary and secondary endpoints were met, as 93.8% (364/388; P = 0.005) of specific sensing tests indicated appropriate atrial sensing, and 94.8% (110/116; P = 0.048) of patients were free from reinterventions (lead dislodgement). Analysis of arrhythmia episodes stored in ICDs and elective 24-hour Holter electrocardiogram tests raised no concerns about lead functionality. CONCLUSION: The studied ICD lead with a floating atrial sensing dipole met the predefined safety expectation and demonstrated appropriate atrial sensing performance.

Mesh ablator vs. cryoballoon pulmonary vein ablation of symptomatic paroxysmal atrial fibrillation: results of the MACPAF study.

AIMS: Catheter ablation of the pulmonary veins (PVs) is a promising therapeutic approach for symptomatic atrial fibrillation (AF). The prospective randomized single-centre study 'Mesh Ablator versus Cryoballoon Pulmonary Vein Ablation of Symptomatic Paroxysmal Atrial Fibrillation' (MACPAF; clinicaltrials.gov NCT01061931) compared the efficacy and safety of two balloon-based PV ablation systems. METHODS AND RESULTS: Thirty-two patients underwent PV ablation for symptomatic paroxysmal AF using the Arctic Front® or the HD Mesh Ablator® catheter according to study protocol. The primary endpoint was complete PV isolation (PVI) at the end of the ablation procedure, determined by exit block after achieving entrance block. Long-term follow-up data are not included in this publication. Patients' mean age was 61.7 ± 8.9 years, 43.2% were female, and median CHA2DS2-VASc score was 2.0. In the intention-to-treat analysis, the rate of the primary endpoint was 56.5% in patients randomized to the Arctic Front® and 9.5% in patients randomized to the HD Mesh Ablator® catheter (P = 0.001). In the per-protocol analysis, complete PVI was achieved in 13 (76.5%) of 17 Arctic Front® patients but in none of the 15 HD Mesh Ablator® patients (P < 0.0001). There were one major and two minor complications in each study arm but no clinically evident stroke. Post-procedural AF recurrence was detected within hospital stay in two (11.8%) Arctic Front® patients and in seven (46.7%) HD Mesh Ablator® patients (P = 0.049). CONCLUSION: The MACPAF study revealed a superiority of the Arctic Front® catheter concerning complete PVI. Owing to the insufficient efficacy of the HD Mesh Ablator® catheter, the safety board decided to stop MACPAF prematurely.

Blood pressure variability as sign of autonomic imbalance in patients with idiopathic dilated cardiomyopathy.

BACKGROUND: The problem of identifying idiopathic dilated cardiomyopathy (IDC) patients who are at risk of sudden death is still unsolved. The presence of autonomic imbalance in patients with IDC might predict sudden death and tachyarrhythmic events. The aim of this study was to analyze the suitability of blood pressure variability (BPV) compared to heart rate variability (HRV) for noninvasive risk stratification in IDC patients. METHODS: Continuous noninvasive blood pressure and high-resolution electrocardiogram were recorded from 91 IDC patients for 30 minutes. During a median follow-up period of 28 months (range: [17-38] months), 14 patients died due to sudden death or necessary resuscitation due to a life-threatening arrhythmia. HRV and BPV analyses were performed in time domain, frequency domain, and nonlinear dynamics. Using the Mann-Whitney U test and Cox regression, we estimated the accuracy of clinical and nonclinical parameters in discriminating high-risk from low-risk patients. RESULTS: Dynamics of blood pressure regulation was significantly changed in high-risk patients, indicating an increased BPV. BPV indexes from nonlinear symbolic dynamics revealed significant univariate (sensitivity: 85.7%; specificity 77.9%; area under receiver-operator characteristics [ROC] curve: 87.8%) differences. In an optimum multivariate set consisting of two clinical indexes (left ventricular end-diastolic diameter, New York Heart Association) and one nonlinear index (symbolic dynamics), highly significant differences between low- and high-risk IDC groups were estimated (sensitivity of 92.9%, specificity of 86.5%, and area under ROC curve of 95.3%). CONCLUSION: Diastolic BPV indexes, especially those from symbolic dynamics, appear to be useful for risk stratification of sudden death in patients with IDC.

Comparison of skin adhesive and absorbable intracutaneous suture for the implantation of cardiac rhythm devices.

AIMS: Wound healing is a major determent in the post-surgical course of patients (pts) after pacemaker (PM) and implantable cardioverter defibrillator (ICD) implantation. Insufficient closure may lead to serious complications with pocket infections leading to the device's explantation as the worst case scenario. In addition to the different types of suture and suture clips, a novel topical skin adhesive containing 2-octyl-cyanoacrylate is commercially available. METHODS AND RESULTS: Over a period of 18 months, we prospectively assigned all cases of PM, ICD, and loop recorder implants either to skin adhesive (Group 1) or to absorbable intracutaneous polydioxanon suture (Group 2). Data were analysed with respect to operation time, wound infections, and healing disorders. One hundred and eighty-three pts were randomized into Group 1 [71 PMs, 60 ICD, 15 cardiac resynchronization therapy (CRT), 11 loop recorders, and 26 generator replacements]. One hundred and eighty-five pts were assigned to Group 2 (62 PMs, 70 ICD, 30 CRT, 7 loop recorders, and 16 generator replacements). There were no differences regarding sex, diabetes, renal insufficiency, corticosteroid therapy, oral anticoagulants, and acetylsalicylic asa/clopidogrel (P = n.s.). For the significantly higher amount of CRT devices (P < 0.05) in Group 2, the procedure times are given for surgeries except CRT. It was 49.1 ± 27.7 min for Group 1 and 53.4 ± 31.9 min for Group 2 (P = n.s.). Adverse events as insufficient closure, major and minor bleeding, pocket haematoma, erythema, incrustation, dehiscence, keloid, and explantation due to infection occurred significantly more often in the adhesive group (P = 0.02). The greatest impact on this result had early adverse events as insufficient closure, wound incrustation, and inflammation (9.3 vs. 6.0%; P = 0.02). We did not find any difference in long-term adverse events, infections in particular (2.7 vs. 1.6%; P = 0.47). CONCLUSION: This study shows no benefit using skin adhesive in comparison to absorbable intracutaneous suture regarding surgery times for the implantation of cardiac rhythm devices. The rate of early adverse events after wound closure is higher after skin adhesive but no difference in long-term adverse events occurred.

Stroke risk associated with balloon based catheter ablation for atrial fibrillation: Rationale and design of the MACPAF Study.

BACKGROUND: Catheter ablation of the pulmonary veins has become accepted as a standard therapeutic approach for symptomatic paroxysmal atrial fibrillation (AF). However, there is some evidence for an ablation associated (silent) stroke risk, lowering the hope to limit the stroke risk by restoration of rhythm over rate control in AF. The purpose of the prospective randomized single-center study "Mesh Ablator versus Cryoballoon Pulmonary Vein Ablation of Symptomatic Paroxysmal Atrial Fibrillation" (MACPAF) is to compare the efficacy and safety of two balloon based pulmonary vein ablation systems in patients with symptomatic paroxysmal AF. METHODS/DESIGN: Patients are randomized 1:1 for the Arctic Front(R) or the HD Mesh Ablator(R) catheter for left atrial catheter ablation (LACA). The predefined endpoints will be assessed by brain magnetic resonance imaging (MRI), neuro(psycho)logical tests and a subcutaneously implanted reveal recorder for AF detection. According to statistics 108 patients will be enrolled. DISCUSSION: Findings from the MACPAF trial will help to balance the benefits and risks of LACA for symptomatic paroxysmal AF. Using serial brain MRIs might help to identify patients at risk for LACA-associated cerebral thromboembolism. Potential limitations of the study are the single-center design, the existence of a variety of LACA-catheters, the missing placebo-group and the impossibility to assess the primary endpoint in a blinded fashion. TRIAL REGISTRATION: clinicaltrials.gov NCT01061931.

Impact of atrial fibrillation burden on cognitive function after left atrial ablation - Results of the MACPAF study.

Atrial fibrillation (AF) is associated with cognitive decline and dementia irrespective of AF-related ischemic stroke. We investigated whether AF burden after ablation in patients with symptomatic paroxysmal AF has an impact on cognitive function. After enrolment to the prospective MACPAF study, study patients received an insertable loop recorder (ILR) and underwent serial neurological/cognitive assessment. To compare cognitive function, the delta of baseline and six months test results (Δpre/post) and a score to assess overall cognitive performance were computed. Thirty patients (median age 65 years (IQR 57-69), 40% female) were divided into groups according to median AF burden (<0.5% vs. ≥0.5%) after ablation. Overall cognitive performance did not differ in patients with an AF burden < 0.5% (median 120% [IQR 100-150]) vs. ≥0.5% (median 120% [IQR 100-160]) within six months after ablation (p = 0.74). Comparing Δpre/post, patients with an AF burden ≥ 0.5% showed significantly better results in the digit-span backwards test (median + 1 [IQR 0 - +2 points]) compared to patients with an AF burden < 0.5% (median 0 [IQR -1-+1]) six months after ablation (p = 0.03). In patients with an AF burden < 0.5%, there was a statistical trend towards better results in the RAVLT test (median + 3 [IQR 0-+4]; p = 0.08) and the ROC test (median + 3 [IQR -1-+5; p = 0.07) compared to patients with an AF burden ≥ 0.5% (median -1 [IQR -3-+2] words and median -1 [IQR -5-+2] points, respectively). Therefore, AF burden had no significant impact on cognitive performance within six months after ablation. Clinical Trial Registration: clinicaltrials.gov NCT01061931.

Cardiac Autonomic Dysfunction and Incidence of de novo Atrial Fibrillation: Heart Rate Variability vs. Heart Rate Complexity.

BACKGROUND: The REACT DX registry evaluates standard therapies to episodes of long-lasting atrial tachyarrhythmias and assesses the quality of sensing and stability of the lead and the implantable cardioverter-defibrillator (ICD) (BIOTRONIK Lumax VR-T DX and successors) over at least a 1-year follow-up period. OBJECTIVE: To study the association between the risk of de novo device-detected atrial fibrillation (AF), the autonomic perturbations before the onset of paroxysmal AF and a 7-days heart rate variability (7dHRV) 1 month after ICD implantation. METHODS: The registry consists of 234 patients implanted with an ICD, including 10 with de novo long-lasting atrial tachyarrhythmias with no prior history of AF. The patients were matched via the propensity-score methodology as well as for properties directly influencing the ECGs recorded using GE CardioMem CM 3000. Heart rate variability (HRV) analysis was performed using standard parameters from time- and frequency-domains, and from non-linear dynamics. RESULTS: No linear HRV was associated with an increased risk of AF (p = n.s.). The only significant approach was derived from symbolic dynamics with the parameter "forbidden words" which distinguished both groups on all 7 days of measurements (p < 0.05), thereby quantifying the heart rate complexity (HRC) as drastically lower in the de novo AF group. CONCLUSION: Cardiac autonomic dysfunction denoted by low HRC may be associated with higher AF incidence. For patients with mild to moderate heart failure, standard HRV parameters are not appropriate to quantify cardiac autonomic perturbations before the onset of AF. Further studies are needed to determine the individual risk for AF that would enable interventions to restore autonomic balance in the general population.

Potential role of home monitoring to reduce inappropriate shocks in implantable cardioverter-defibrillator patients due to lead failure.

AIMS: Lead dysfunctions in implantable cardioverter-defibrillator (ICD) patients can lead to inappropriate shocks or even complete loss of function of the device. Home monitoring (HM) systems are capable of daily data transmissions regarding the device and the lead integrity as well as information concerning anti-arrhythmic therapies. We therefore analysed the data from the Biotronik HM system whether it enables physicians to react quickly on serious ICD malfunctions and to avoid inappropriate shocks. METHODS AND RESULTS: Fifty-four patients who had to undergo resurgery due to malfunctions of the ICD lead were included. Eleven of them were on HM interrogating the device every night at 3 am. If any adverse event was detected, a fax alert was sent to the clinic and the patients were asked for in-hospital ICD interrogation. The rate of inappropriate shocks and symptomatic pacemaker inhibition due to oversensing was compared with the 43 patients without remote surveillance. HM sent alert messages in 91% of all incidents. All lead failures became obvious because of oversensing of high frequency artefacts. Only in 18%, changes in the pacing impedance were noticed, in all cases preceded by oversensing. Eighty per cent of the patients were asymptomatic at the first onset of oversensing. Only one patient suffered an inappropriate shock as first manifestation of lead failure. Compared with the patients without HM, inappropriate shocks occurred in 27.3% in the HM group vs. 46.5% (P = n.s.). This trend gains statistical significance, if the compound endpoint of symptomatic lead failure consisting of inappropriate shocks and symptomatic pacemaker inhibition due to oversensing is focused: 27.3% event in the HM group vs. 53.4% in the group without HM (P = 0.04). Event messages were despatched in a mean of 54 days after the last ICD interrogation and 56 days before next scheduled visit. Thus, 56 days of reaction time are gained to avoid adverse events. CONCLUSION: In 91% of all lead-related ICD complications, the diagnosis could be established correctly by an alert of the HM system. Mostly, the first incident sent was oversensing of artefacts, falsely detected as ventricular fibrillation-the VF zone. The automatic HM surveillance system enables physicians to detect severe lead problems early and to react quickly; thus, it might have a potential to avoid inappropriate shocks due to lead failure and T-wave oversensing.

Detection of patients with coronary artery disease using cardiac magnetic field mapping at rest.

We studied the use of cardiac magnetic field mapping to detect patients with CAD without subjecting them to stress. Fifty-nine healthy control subjects and 101 patients with CAD without previous MI were included. The optimal positions for detecting CAD were located in the left superior parasternal and in the inferior midsternal area. Values for ST slope, ST shift, T peak amplitude, ST-T integral, and magnetic field map orientation differed significantly between the 2 groups. Three parameters together in a multivariate analysis yielded a sensitivity of 84% and a specificity of 83% in distinguishing patients with CAD from control subjects. We suggest that cardiac magnetic field mapping is a promising technique to identify patients with CAD.

Loop Recorder Detected High Rate of Atrial Fibrillation Recurrence after a Single Balloon- or Basket-Based Ablation of Paroxysmal Atrial Fibrillation: Results of the MACPAF Study.

PURPOSE: Pulmonary vein isolation (PVI) is an established approach to treat symptomatic non-permanent atrial fibrillation (AF). Detecting AF recurrence after PVI is important, if discontinuation of oral anticoagulation after ablation is considered. METHODS: Patients with symptomatic paroxysmal AF were enrolled in the prospective randomized mesh ablator vs. cryoballoon pulmonary vein (PV) ablation of symptomatic paroxysmal AF study, comparing efficacy and safety of the HD Mesh Ablator® (C.R. Bard, Lowell, MA, USA) and the Arctic Front® (Medtronic, Minneapolis, MN, USA) catheter. Rhythm status post-PVI was closely monitored for 1 year using the implantable loop recorder (ILR) Reveal XT® (Medtronic Minneapolis, MN, USA). RESULTS: The study was terminated after the first interim analysis due to the inability of the HD Mesh Ablator® to achieve the predefined primary study endpoint, an exit block of all PVs. After a 90-day blanking period, 23 (62.2%) out of 37 study patients (median 63.0 years; 41% females) had at least one episode of AF. AF recurrence was associated with AF episodes during the blanking period {hazard ratios (HR) 5.10 [95% confidence interval (CI) 1.21-21.4]; p = 0.038}, and a common left-sided PV ostium [HR 4.17 (95%CI 1.48-11.8); p = 0.039] but not with catheter type, age, gender, cardiovascular risk profile, or left atrial volume. There was a trend toward AF recurrence in patients without complete PVI of all PV (p = 0.095). Overall, 337 (59.4%) out of 566 ILR-detected episodes represented AF. Comparing patients with AF recurrence to those without, there was no difference in cognitive performance 6 months post-ablation. CONCLUSION: Using an ILR, in more than 60% of all patients with paroxysmal AF, a recurrence of AF was detected within 12 months after ablation. In patients with a common PV ostium, the first generation balloon-based catheter is obviously less effective. CLINICAL TRIALS: http://Clinicaltrials.gov NCT01061931.

Large-scale dimension densities for heart rate variability analysis.

In this work, we reanalyze the heart rate variability (HRV) data from the 2002 Computers in Cardiology (CiC) Challenge using the concept of large-scale dimension densities and additionally apply this technique to data of healthy persons and of patients with cardiac diseases. The large-scale dimension density (LASDID) is estimated from the time series using a normalized Grassberger-Procaccia algorithm, which leads to a suitable correction of systematic errors produced by boundary effects in the rather large scales of a system. This way, it is possible to analyze rather short, nonstationary, and unfiltered data, such as HRV. Moreover, this method allows us to analyze short parts of the data and to look for differences between day and night. The circadian changes in the dimension density enable us to distinguish almost completely between real data and computer-generated data from the CiC 2002 challenge using only one parameter. In the second part we analyzed the data of 15 patients with atrial fibrillation (AF), 15 patients with congestive heart failure (CHF), 15 elderly healthy subjects (EH), as well as 18 young and healthy persons (YH). With our method we are able to separate completely the AF (rho (mu/ls) = 0.97 +/- 0.02) group from the others and, especially during daytime, the CHF patients show significant differences from the young and elderly healthy volunteers (CHF, 0.65 +/- 0.13; EH, 0.54 +/- 0.05; YH, 0.57 +/- 0.05; p < 0.05 for both comparisons). Moreover, for the CHF patients we find no circadian changes in rho (mu/ls) (day, 0.65 +/- 0.13; night, 0.66 +/- 0.12; n.s.) in contrast to healthy controls (day, 0.54 +/- 0.05; night, 0.61 +/- 0.05; p=0.002). Correlation analysis showed no statistical significant relation between standard HRV and circadian LASDID, demonstrating a possibly independent application of our method for clinical risk stratification.

Nonlinear additive autoregressive model-based analysis of short-term heart rate variability.

In this contribution we test the hypothesis that nonlinear additive autoregressive model-based data analysis improves the diagnostic ability based on short-term heart rate variability. For this purpose, a nonlinear regression approach, namely, the maximal correlation method is applied to the data of 37 patients with dilated cardiomyopathy as well as of 37 age- and sex-matched healthy subjects. We find that this approach is a powerful tool in discriminating both groups and promising for further model-based analyses.

Normalized correlation dimension for heart rate variability analysis.

In this paper we use the concept of large-scale dimension densities to analyze heart rate variability data. This method uses a normalized Grassberger-Procaccia algorithm and estimates the dimension in the rather large scales of the system. This enables us to analyze very short data. First we re-analyze data from the CIC 2002 challenge and can completely distinguish between real data and computer-generated data using only one parameter. We then analyze unfiltered data for 15 patients with atrial fibrillation (AF), 15 patients with congestive heart failure (CHF), 15 elderly healthy subjects, and 18 young healthy subjects. This method can completely separate the AF group from the other groups and the CHF patients show significant differences compared to the young and elderly healthy volunteers. Furthermore, differences are evident in the dimensionality between day and night for healthy persons, but not for the CHF patients. Finally, the results are compared to standard heart rate variability parameters.

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.

Heart rate variability before the onset of ventricular tachycardia: differences between slow and fast arrhythmias.

BACKGROUND: We tested whether or not heart rate variability (HRV) changes can serve as early signs of ventricular tachycardia (VT) and predict slow and fast VT in patients with an implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: We studied the ICD stored 1000 beat-to-beat intervals before the onset of VT (131 episodes) and during a control time without VT (74 series) in 63 chronic heart failure ICD patients. Standard HRV parameters as well as two nonlinear parameters, namely 'Polvar10' from symbolic dynamics and the finite time growth rates 'Fitgra9' were calculated. Comparing the control and the VT series, no linear HRV parameter showed a significant difference. The nonlinear parameters detected a significant increase in short phases with low variability before the onset of VT (for time series with less than 10% ectopy, P<0.05). Subdividing VT into fast (cycle length 270 ms) events, we found that the onset of slow VT was characterized by a significant increase in heart rate, whereas fast VT was triggered during decreased heart rates, compared to the control series. CONCLUSIONS: Our data may permit the development of automatic ICD algorithms based on nonlinear dynamic HRV parameters to predict VT before it starts. Furthermore, they may facilitate improved prevention strategies.

Recurrence-plot-based measures of complexity and their application to heart-rate-variability data.

The knowledge of transitions between regular, laminar or chaotic behaviors is essential to understand the underlying mechanisms behind complex systems. While several linear approaches are often insufficient to describe such processes, there are several nonlinear methods that, however, require rather long time observations. To overcome these difficulties, we propose measures of complexity based on vertical structures in recurrence plots and apply them to the logistic map as well as to heart-rate-variability data. For the logistic map these measures enable us not only to detect transitions between chaotic and periodic states, but also to identify laminar states, i.e., chaos-chaos transitions. The traditional recurrence quantification analysis fails to detect the latter transitions. Applying our measures to the heart-rate-variability data, we are able to detect and quantify the laminar phases before a life-threatening cardiac arrhythmia occurs thereby facilitating a prediction of such an event. Our findings could be of importance for the therapy of malignant cardiac arrhythmias.

Short-term heart rate turbulence analysis versus variability and baroreceptor sensitivity in patients with dilated cardiomyopathy.

New methods for the analysis of arrhythmias and their hemodynamic consequences have been applied in risk stratification, in particular to patients after myocardial infarction. This study investigates the suitability of short-term heart rate turbulence (HRT) analysis in comparison to heart rate and blood pressure variability as well as baroreceptor sensitivity analyses to characterise the regulatory differences between patients with dilated cardiomyopathy (DCM) and healthy controls. In this study, 30 minutes data of non-invasive continuous blood pressure and ECGs of 37 DCM patients and 167 controls measured under standard resting conditions were analysed. The results show highly significant differences between DCM patients and controls in heart rate and blood pressure variability as well as in baroreceptor sensitivity parameters. Applying a combined heart rate-blood pressure trigger, ventricular premature beats were detected in 24.3% (9) of the DCM patients and 11.3% (19) of the controls. This fact demonstrates the limited applicability of short-term HRT analyses. However, the HRT parameters showed significant differences in this subgroup with ventricular premature beats (turbulence onset: DCM: 1.80+/-2.72, controls: - 4.34+/-3.10, p<0.001; turbulence slope: DCM: 6.75+/-5.50, controls: 21.30+/-17.72, p=0.021). Considering all (including HRT) parameters in the subgroup with ventricular beats, a discrimination rate between DCM patients and controls of 88.0% was obtained (max. 6 parameters). The corresponding value obtained for the total group was 86.3% (without HRT parameters). Comparable classification rates and high correlations between heart rate turbulence and variability and baroreflex parameters point to a more universal applicability of the latter methods.