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Moreillon B, Krumm B, Saugy JJ, Saugy M, Botrè F, Vesin JM, Faiss R. Prediction of plasma volume and total hemoglobin mass with machine learning. Physiol Rep 2023; 11:e15834. [PMID: 37828664 PMCID: PMC10570407 DOI: 10.14814/phy2.15834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 09/12/2023] [Accepted: 09/12/2023] [Indexed: 10/14/2023] Open
Abstract
Hemoglobin concentration ([Hb]) is used for the clinical diagnosis of anemia, and in sports as a marker of blood doping. [Hb] is however subject to significant variations mainly due to shifts in plasma volume (PV). This study proposes a newly developed model able to accurately predict total hemoglobin mass (Hbmass) and PV from a single complete blood count (CBC) and anthropometric variables in healthy subject. Seven hundred and sixty-nine CBC coupled to measures of Hbmass and PV using a CO-rebreathing method were used with a machine learning tool to calculate an estimation model. The predictive model resulted in a root mean square error of 33.2 g and 35.6 g for Hbmass, and 179 mL and 244 mL for PV, in women and men, respectively. Measured and predicted data were significantly correlated (p < 0.001) with a coefficient of determination (R2 ) ranging from 0.76 to 0.90 for Hbmass and PV, in both women and men. The Bland-Altman bias was on average 0.23 for Hbmass and 4.15 for PV. We herewith present a model with a robust prediction potential for Hbmass and PV. Such model would be relevant in providing complementary data in contexts such as the epidemiology of anemia or the individual monitoring of [Hb] in anti-doping.
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Affiliation(s)
- B. Moreillon
- Research and Expertise in anti‐Doping Sciences (REDs), Institute of Sport SciencesUniversity of LausanneLausanneSwitzerland
- Union Cycliste InternationaleWorld Cycling CentreAigleSwitzerland
| | - B. Krumm
- Research and Expertise in anti‐Doping Sciences (REDs), Institute of Sport SciencesUniversity of LausanneLausanneSwitzerland
| | - J. J. Saugy
- Research and Expertise in anti‐Doping Sciences (REDs), Institute of Sport SciencesUniversity of LausanneLausanneSwitzerland
| | - M. Saugy
- Research and Expertise in anti‐Doping Sciences (REDs), Institute of Sport SciencesUniversity of LausanneLausanneSwitzerland
| | - F. Botrè
- Research and Expertise in anti‐Doping Sciences (REDs), Institute of Sport SciencesUniversity of LausanneLausanneSwitzerland
- Laboratorio AntidopingFederazione Medico Sportiva ItalianaRomeItaly
| | - J. M. Vesin
- Signal Processing Laboratory 2Swiss Federal Institute of TechnologyLausanneSwitzerland
| | - R. Faiss
- Research and Expertise in anti‐Doping Sciences (REDs), Institute of Sport SciencesUniversity of LausanneLausanneSwitzerland
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2
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Schlageter V, Badertscher P, Krisai P, Spies F, Luca A, Osswald S, Vesin JM, Kuehne M, Sticherling C, Knecht S. An automatic single beat algorithm to discriminate farfield from nearfield bipolar voltage electrograms from the pulmonary veins. Europace 2022. [DOI: 10.1093/europace/euac053.564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Public hospital(s). Main funding source(s): “Stiftung für Herzschrittmacher und Elektrophysiologie” Basel, Switzerland
Background
Confirmation of pulmonary vein (PV) isolation (PVI) during ablation of atrial fibrillation can be challenging due to superimposition of nearfield (NF) PV and farfield (FF) atrial bipolar voltage electrograms (BVE).
Purpose
To develop an automatic algorithm allowing to discriminate PV nearfield (PV-NF) from atrial farfield (atrial-FF) BVE from a circular mapping catheter during cryoballoon (CB) PVI based on a single-heartbeat analysis.
Methods
BVEs from a decapolar inner-lumen diagnostic catheter (Achieve, Medtronic) during CB PVI were manually classified as PV-NF, atrial-FF and combined FF-NF signal based on the characteristics and disappearance of the PV signal during isolation (Figure, upper row). BVE power spectra were computed using the fast Fourier transform (FFT) and the automatic classification of PV-NF, atrial-FF and combined FF-NF signals was performed using the power in different frequency bands (Figure, lower row). Support vector machine classifier was used to identify PV-NF BVE due to its highest predictive accuracy for the two classes PV-NF+ (PV-NF only and combined FF-NF) and PV-NF- (atrial-FF only). Validation of the approach was performed by comparison of a subset of 80 random samples, which were classified in addition by five experienced electrophysiologists.
Results
We analysed a dataset of 355 BVEs from 57 patients. The examples were balanced between the two classes PV-NF+ and PV-NF-. The mean duration (95% CI) of the BVE was 58 ms (26 to 86), 70 ms (50 to 100) and 94 ms (71 to 139) for PV NF, atrial-FF and combined FF-NF, respectively. The overall balanced accuracy including BVE from all PVs was 82.7% (95% CI: 80.3% to 85.1%). The analysis on individual PVs showed an accuracy of 96.6%, 85.2%, 80.8%, and 76.9% for the right inferior, right superior, left inferior and left superior PV, respectively. Validation of the algorithm in the subset of 80 patients showed a comparable accuracy, sensitivity and specificity in PV-NF detection between the automatic algorithm and the experienced electrophysiologists (82.8%, 89.2%, and 76.3%, compared to 85.2%, 91.9%, and 78.5%, respectively).
Conclusion
A reliable automatic based classification algorithm to identify PV-NF BVE could be developed based on a single-beat analysis. Real-time applications as well as using other electrode configurations may improve local signal interpretation.
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Affiliation(s)
- V Schlageter
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - P Badertscher
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - P Krisai
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - F Spies
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - A Luca
- Swiss Federal Institute of Technology of Lausanne, Applied Signal Processing Group, Lausanne, Switzerland
| | - S Osswald
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - JM Vesin
- Swiss Federal Institute of Technology of Lausanne, Applied Signal Processing Group, Lausanne, Switzerland
| | - M Kuehne
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - C Sticherling
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
| | - S Knecht
- University Hospital Basel, Department of Cardiology, Basel, Switzerland
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3
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Pithon A, Luca A, Buttu A, Vesin JM, Roten L, Kuhne M, Spiess F, Knecht S, Sticherling C, Park CI, Pascale P, Le Bloa M, Herrera C, Pruvot E. P979Persistent atrial fibrillation terminated within the left atrium without recurrence at follow-up demonstrates a gradual intracardiac organization during stepwise ablation. Eur Heart J 2019. [DOI: 10.1093/eurheartj/ehz747.0572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Introduction
We previously reported that patients (pts) with recurrence (Rec) after stepwise catheter ablation (step-CA) of persistent atrial fibrillation (pAF) exhibit high bi-atrial intracardiac dominant frequencies (DF) values before ablation, indicative of a severe bi-atrial electro-anatomical remodeling.
Purpose
Herein, we hypothesized that a gradual decrease in DF values during step-CA is associated with pAF termination and maintenance of sinus rhythm (SR) on the long term.
Method
In 40 consecutive pts (61±8 yo, sustained AF duration 19±11 months), pulmonary vein isolation (PVI) and left atrium (LA) ablation were performed until pAF termination or cardioversion. 10-sec intracardiac electrograms (EGMs) epochs were recorded before ablation (BL), during PVI and during complex fractionated atrial electrograms (CFAEs) and linear ablation (post_PVI) in the right atrial (RAA) and left atrial (LAA) appendages and in the coronary sinus (CS). DF was defined as the highest peak within the [3–15] Hz EGM spectrum. Rec was defined as any atrial arrhythmia lasting >30 sec during follow-up (FU).
Results
pAF was terminated within the LA in 70% (28/40, LT) of the pts, while 30% (12/40, NLT) were not. After a mean FU of 34±14 months, all NLT pts had a Rec, while LT pts presented a Rec in 71% (20/28, LT_rec) and remained in SR in 29% (8/28, LT_norec). Figure 1 shows: 1) a gradient in DF values measured in the LAA (panel A), RAA (panel B) and CS (panel C) with the highest values in NLT pts (red), intermediate values in LT_rec pts (yellow) and lowest DF values in LT_norec pts (green); 2) all three groups displayed a gradual intracardiac organization during LA ablation as shown by decreasing DF values (p<0.05, BL vs post_PVI), but the LT_norec pts (green) exhibited the highest relative changes in DF from BL (p<0.05, LT_norec vs NLT, Δ range: −5.31 to −9.69%).
Figure 1. Effect of ablation on DF
Conclusion
Low DF values before ablation and gradual intracardiac organization until pAF termination are associated with maintenance of SR on the long term.
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Affiliation(s)
- A Pithon
- University Hospital Centre Vaudois (CHUV), Service of Cardiology, Lausanne, Switzerland
| | - A Luca
- University Hospital Centre Vaudois (CHUV), Service of Cardiology, Lausanne, Switzerland
| | - A Buttu
- Swiss Federal Institute of Technology of Lausanne, ASPG, Lausanne, Switzerland
| | - J M Vesin
- Swiss Federal Institute of Technology of Lausanne, ASPG, Lausanne, Switzerland
| | - L Roten
- Bern University Hospital, Service of Cardiology, Bern, Switzerland
| | - M Kuhne
- University Hospital Basel, Service of Cardiology, Basel, Switzerland
| | - F Spiess
- University Hospital Basel, Service of Cardiology, Basel, Switzerland
| | - S Knecht
- University Hospital Basel, Service of Cardiology, Basel, Switzerland
| | - C Sticherling
- University Hospital Basel, Service of Cardiology, Basel, Switzerland
| | - C I Park
- La Tour Hospital, Department of Cardiology, Geneva, Switzerland
| | - P Pascale
- University Hospital Centre Vaudois (CHUV), Service of Cardiology, Lausanne, Switzerland
| | - M Le Bloa
- University Hospital Centre Vaudois (CHUV), Service of Cardiology, Lausanne, Switzerland
| | - C Herrera
- University Hospital Centre Vaudois (CHUV), Service of Cardiology, Lausanne, Switzerland
| | - E Pruvot
- University Hospital Centre Vaudois (CHUV), Service of Cardiology, Lausanne, Switzerland
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Chik WWB, Robinson D, Malchano Z, Allison J, Saadat V, Kovoor P, Thomas SP, Thiagalingam A, Bulava A, Hanis J, Osmera O, Rehouskova K, Sitek D, Novotny A, Aldhoon B, Wichterle D, Peichl P, Cihak R, Kautzner J, Le Heuzey JY, Breithardt G, Camm AJ, Crijns HJ, Dorian P, Kowey PR, Naditch-Brule L, Prystowsky EN, Baruteau AE, Behaghel A, Chatel S, Mabo P, Schott JJ, Daubert JC, Le Marec H, Probst V, Regoli F, Nucifora G, Faletra F, Pasotti E, Pedrazzini G, Moccetti T, Auricchio A, Szili-Torok T, Ujvari B, Bauernfeind T, Domburg RT, Balk A, Jordaens L, Simoons M, Caliskan K, Uldry L, Van Zaen J, Kappenberger L, Vesin JM, Ferreira Santos L, Pereira T, Rodrigues B, Machado J, Castedo S, Henriques C, Matos A, Oliveira Santos J, Van Zaen J, Uldry L, Buttu A, Kappenberger L, Vesin JM. Hot topics: arrhythmias. Europace 2011. [DOI: 10.1093/europace/eur221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Dang L, Virag N, Ihara Z, Jacquemet V, Vesin JM, Schlaepfer J, Ruchat P, Kappenberger L. Evaluation of ablation patterns using a biophysical model of atrial fibrillation. Ann Biomed Eng 2005; 33:465-74. [PMID: 15909652 DOI: 10.1007/s10439-005-2502-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. Surgical/Radiofrequency (RF) ablation is a therapeutic procedure that consists of creating lines of conduction block to interrupt AF. The present study evaluated 13 different ablation patterns by means of a biophysical model of the human atria. In this model, ablation lines were abruptly applied transmurally during simulated sustained AF, and success rate, time to AF termination and average beat-to-beat interval were documented. The gold standard Cox's Maze III procedure was taken as reference. The effectiveness of twelve less invasive patterns was compared to it. In some of these incomplete lines (entailing a gap) were simulated. Finally, the computer simulations were compared to clinical data. The results show that the model reproduces observations made in vivo: (1) the Maze III is the most efficient ablation procedure; (2) less invasive patterns should include lines in both right and left atrium; (3) incomplete ablation lines between the pulmonary veins and the mitral valve annulus lead to uncommon flutter; (4) computer simulations of incomplete lines are consistent with clinical results of non-transumural RF ablation. Biophysical modeling may therefore be considered as a useful tool for understanding the mechanisms underlying AF therapies.
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Affiliation(s)
- L Dang
- Signal Processing Institute, Swiss Federal Institute of Technology, Lausanne, Switzerland. lam.dang2epfl.ch
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6
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Devuyst G, Darbellay GA, Vesin JM, Kemény V, Ritter M, Droste DW, Molina C, Serena J, Sztajzel R, Ruchat P, Lucchesi C, Dietler G, Ringelstein EB, Despland PA, Bogousslavsky J. Automatic classification of HITS into artifacts or solid or gaseous emboli by a wavelet representation combined with dual-gate TCD. Stroke 2001; 32:2803-9. [PMID: 11739977 DOI: 10.1161/hs1201.099714] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Transcranial Doppler (TCD) can detect high-intensity transient signals (HITS) in the cerebral circulation. HITS may correspond to artifacts or solid or gaseous emboli. The aim of this study was to develop an offline automated Doppler system allowing the classification of HITS. METHODS We studied 600 HITS in vivo, including 200 artifacts from normal subjects, 200 solid emboli from patients with symptomatic internal carotid artery stenosis, and 200 gaseous emboli in stroke patients with patent foramen ovale. The study was 2-fold, each part involving 300 HITS (100 of each type). The first 300 HITS (learning set) were used to construct an automated classification algorithm. The remaining 300 HITS (validation set) were used to check the validity of this algorithm. To classify HITS, we combined dual-gate TCD with a wavelet representation and compared it with the current "gold standard," the human experts. RESULTS A combination of the peak frequency of HITS and the time delay makes it possible to separate artifacts from emboli. On the validation set, we achieved a sensitivity of 97%, a specificity of 98%, a positive predictive value (PPV) of 99%, and a negative predictive value (NPV) of 94%. To distinguish between solid and gaseous emboli, where positive refers now to the solid emboli, we used the peak frequency, the relative power, and the envelope symmetry of HITS. On the validation set, we achieved a sensitivity of 89%, a specificity of 86%, a conditional PPV of 89%, and a conditional NPV of 89%. CONCLUSIONS An automated wavelet representation combined with dual-gate TCD can reliably reject artifacts from emboli. From a clinical standpoint, however, this approach has only a fair accuracy in differentiating between solid and gaseous emboli.
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Affiliation(s)
- G Devuyst
- Department of Neurology, CHUV, the Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne, Geneva, Switzerland.
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7
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Blanc O, Virag N, Vesin JM, Kappenberger L. A computer model of human atria with reasonable computation load and realistic anatomical properties. IEEE Trans Biomed Eng 2001; 48:1229-37. [PMID: 11686622 DOI: 10.1109/10.959315] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Atrial fibrillation is the most frequent arrhythmia, provoking discomfort, heart failure and arterial embolisms. The aim of this work is to develop a simplified anatomical computer model of human atria for the study of atrial arrhythmias and the understanding of electrical propagation mechanisms. With the model we propose, up to 40 s of real-time propagation have been simulated on a single-processor computer. The size and the electrophysiological properties of the simulated atria are within realistic values and information about anatomy has been taken into account in a three-dimensional structure. Besides normal sinus beat, pathological phenomena such as flutter and fibrillation have been induced using a programmed stimulation protocol. One important observation in our model is that atrial arrhythmias are a combination of functional and anatomical reentries and that the geometry plays an important role. This virtual atrium can reproduce electrophysiological observations made in humans but with the advantage of showing in great detail how arrhythmias are initiated and sustained. Such details are difficult or impossible to study in humans. This model will serve us as a tool to evaluate the impact of new therapeutic strategies and to improve them.
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Affiliation(s)
- O Blanc
- Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne
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8
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Grüter R, Egger O, Vesin JM, Kunt M. Rank-order polynomial subband decomposition for medical image compression. IEEE Trans Med Imaging 2000; 19:1044-1052. [PMID: 11131494 DOI: 10.1109/42.887619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this paper, the problem of progressive lossless image coding is addressed. A nonlinear decomposition for progressive lossless compression is presented. The decomposition into subbands is called rank-order polynomial decomposition (ROPD) according to the polynomial prediction models used. The decomposition method presented here is a further development and generalization of the morphological subband decomposition (MSD) introduced earlier by the same research group. It is shown that ROPD provides similar or slightly better results than the compared coding schemes such as the codec based on set partitioning in hierarchical trees (SPIHT) and the codec based on wavelet/trellis-coded quantization (WTCQ). Our proposed method highly outperforms the standard JPEG. The proposed lossless compression scheme has the functionality of having a completely embedded bit stream, which allows for data browsing. It is shown that the ROPD has a better lossless rate than the MSD but it has also a much better browsing quality when only a part of the bit stream is decompressed. Finally, the possibility of hybrid lossy/lossless compression is presented using ultrasound images. As with other compression algorithms, considerable gain can be obtained if only the regions of interest are compressed losslessly.
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Affiliation(s)
- R Grüter
- Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne
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9
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Abstract
Detection of clinically silent circulating microemboli within cerebral arteries by transcranial Doppler ultrasound (US) is now being widely investigated in the hope of identifying patients at increased risk for stroke. However, the widespread application of embolus detection is still limited in clinical practice because current transcranial Doppler systems have not the required sensitivity and specificity to analyze microembolic signals, particularly to distinguish between gaseous, or solid brain emboli and artefacts. In this work, we proposed to investigate the potential of a new approach for the analysis of microembolic signals via the so-called matching pursuit, which is closely related to wavelet transform and is not subject to the same limitations as the fast Fourier transform. Our preliminary results clearly indicate that matching pursuit is well suited to this task.
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Affiliation(s)
- G Devuyst
- CHUV, Department of Neurology, Lausanne, Switzerland.
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10
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Pruvot E, Thonet G, Vesin JM, van-Melle G, Seidl K, Schmidinger H, Brachmann J, Jung W, Hoffmann E, Tavernier R, Block M, Podczeck A, Fromer M. Heart rate dynamics at the onset of ventricular tachyarrhythmias as retrieved from implantable cardioverter-defibrillators in patients with coronary artery disease. Circulation 2000; 101:2398-404. [PMID: 10821817 DOI: 10.1161/01.cir.101.20.2398] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The recent availability of implantable cardioverter-defibrillators (ICDs) that record 1024 R-R intervals preceding a ventricular tachyarrhythmia (VTA) provides a unique opportunity to analyze heart rate variability (HRV) before the onset of VTA. METHODS AND RESULTS Fifty-eight post-myocardial infarction patients with an implanted ICD for recurrent VTA provided 2 sets of 98 heart rate recordings in sinus rhythm: (1) before a VTA and (2) during control conditions. Three subgroups were considered according to the antiarrhythmic (AA) drug regimen. A state of sympathoexcitation was suggested by the significant reduction in HRV before VTA onset compared with control conditions. beta-Blockers and dl-sotalol enhanced HRV in control recordings; nevertheless, HRV declined before VTA independent of AA drugs. A gradual increase in heart rate and decrease in sinus arrhythmia at VTA onset were specific findings of patients who received dl-sotalol. CONCLUSIONS The peculiar heart rate dynamics observed before VTA onset are suggestive of a state of sympathoexcitation that is independent of AA drugs.
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Affiliation(s)
- E Pruvot
- Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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11
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Vetter R, Virag N, Vesin JM, Celka P, Scherrer U. Observer of autonomic cardiac outflow based on blind source separation of ECG parameters. IEEE Trans Biomed Eng 2000; 47:578-82. [PMID: 10851800 DOI: 10.1109/10.841328] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We present a novel method which provides an observer of the autonomic cardiac outflow using heartbeat intervals (RR) and QT intervals. The model of the observer is inferred from qualitative physiological knowledge. It consists in a problem of blind source separation of noisy mixtures which is resolved by a simple and robust algorithm. The robustness of the algorithm has been assessed by numerical simulations in adverse noisy environments. In clinical applications, we have validated the observer on subjects exposed to experimental conditions known to elicit sympathetic or parasympathetic response.
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Affiliation(s)
- R Vetter
- Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne, Switzerland
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12
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Vetter R, Vesin JM, Celka P, Scherrer U. Observer of the human cardiac sympathetic nerve activity using noncausal blind source separation. IEEE Trans Biomed Eng 1999; 46:322-30. [PMID: 10097467 DOI: 10.1109/10.748985] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We present a novel method for the blind reconstruction of the cardiac sympathetic nerve activity (CSNA) in the low-frequency (LF) band (0.04-0.15 Hz) using only heart rate and arterial blood pressure. The originality of the method consists in the application of blind source separation techniques to obtain an observer of CSNA. We show how this observer can be deduced from a linear model of the cardiovascular system by introduction of the fundamental assumptions about the independence of the cardiac sympathetic an parasympathetic outflow. In cardiovascular applications, the reliability of the observer has been assessed by verification of the fundamental assumption for the given data. A primer qualitative validation has been performed using the muscle sympathetic nerve activity as an indirect indicator of CSNA. Very satisfying and promising results have been obtained. Moreover, we have performed quantitative validations of the observer in various experimental conditions known to elicit selectively cardiac sympathetic or parasympathetic response. The experimental conditions include a supine-to-60 degrees tilt test, indirect sympathetic stimulation/inhibition by medication, and sympathetic stimulation by isometric handgrip. We show that the observer allows to highlight changing levels of the cardiac sympathetic activity in the LF band in all these experimental conditions.
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Affiliation(s)
- R Vetter
- Swiss Federal Institute of Technology, Laboratiore du traitement des signaux, EPFL, Lausanne, Switzerland.
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13
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Celka P, Vetter R, Vesin JM, Pruvot E, Scherrer U. Exponential-type distribution of human muscle sympathetic nerve activity results in an automatic quantification method. Comput Biol Med 1998; 28:627-37. [PMID: 9878975 DOI: 10.1016/s0010-4825(98)00014-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A new burst counting method based on a subject invariant characteristic demonstrates the limits of the actual automatic based methods. The exponential behaviour of the counted bursts in function of a variable threshold highlights a scaling property of the muscle sympathetic nerve activity. From experimental single unit recording results, we deduce the exponential-type (gamma) distribution of instantaneous spiking frequency within multi-unit recordings. We show that integrated muscle sympathetic nerve discharges must be gamma distributed with parameters proportional to the number of neurons in the recording pool and to the integration window width.
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Affiliation(s)
- P Celka
- Department of Electrical Engineering, Swiss Federal Institute of Technology, Lausanne, Switzerland.
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14
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Abstract
Modern computer power allows development of models of the heart that may be helpful for the understanding of arrhythmia mechanisms if, based on realistic physiological parameters, such models can display phenomena difficult to study in nature. Therefore, a two-dimensional model of the cardiac tissue has been implemented, where the modeling of each cell is based on membrane ionic channels (Beeler-Reuter and Luo-Rudy models). In addition, an ECG was computed based on the ionic currents simulated. This model allows us to observe the propagation of the action potentials Vm across the cardiac tissue, the evolution of Vm for any of the cardiac cells, and the underlying ionic currents. The computation of the ECG makes it possible to relate this information with an often-used diagnostic tool. Simulations of normal and pathological phenomena such as functional and anatomic reentry have been performed. Our simulation results show that the applied computer model based on ionic currents seems accurate and realistic when compared with biological models and offers a new approach to study the origin, prevention, and termination of arrhythmias.
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Affiliation(s)
- N Virag
- Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne, Switzerland
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15
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Schroeter P, Vesin JM, Langenberger T, Meuli R. Robust parameter estimation of intensity distributions for brain magnetic resonance images. IEEE Trans Med Imaging 1998; 17:172-186. [PMID: 9688150 DOI: 10.1109/42.700730] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This paper presents two new methods for robust parameter estimation of mixtures in the context of magnetic resonance (MR) data segmentation. The head is constituted of different types of tissue that can be modeled by a finite mixture of multivariate Gaussian distributions. Our goal is to estimate accurately the statistics of desired tissues in presence of other ones of lesser interest. These latter can be considered as outliers and can severely bias the estimates of the former. For this purpose, we introduce a first method, which is an extension of the expectation-maximization (EM) algorithm, that estimates parameters of Gaussian mixtures but incorporates an outlier rejection scheme which allows to compute the properties of the desired tissues in presence of atypical data. The second method is based on genetic algorithms and is well suited for estimating the parameters of mixtures of different kind of distributions. We use this property by adding a uniform distribution to the Gaussian mixture for modeling the outliers. The proposed genetic algorithm can efficiently estimate the parameters of this extended mixture for various initial settings. Also, by changing the minimization criterion, estimates of the parameters can be obtained by histogram fitting which considerably reduces the computational cost. Experiments on synthetic and real MR data show that accurate estimates of the gray and white matters parameters are computed.
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Affiliation(s)
- P Schroeter
- Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne.
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Vetter R, Celka P, Vesin JM, Thonet G, Pruvot E, Fromer M, Scherrer U, Bernardi L. Subband modeling of the human cardiovascular system: new insights into cardiovascular regulation. Ann Biomed Eng 1998; 26:293-307. [PMID: 9525769 DOI: 10.1114/1.57] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We present a new approach to cardiovascular analysis based on a well-known signal processing technique, namely, the frequency subband decomposition. The subbands are chosen in accordance with physiological standards: (1) 0-0.04 Hz, (2) 0.04-0.15 Hz, (3) 0.15-0.4 Hz. It is shown that such a pre-processing drastically improves the accuracy of the analysis and introduces a new direction in the understanding of the relationships between cardiovascular signals.
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Affiliation(s)
- R Vetter
- Department of Electrical Engineering, Swiss Federal Institute of Technology, Lausanne
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Abstract
In this prospective study, the autonomic modulation of the sinus node of 12 patients (mean age 28 +/- 7 years) suffering from vasovagal syncope (VVS) was compared to that of 11 sex and age matched control patients (mean age 32 +/- 4 years) by analysis of heart rate variability. Spectral indices (low frequency power [Plf], high frequency power [Phf], total power [Pt], sympathovagal balance [LF/HF]) and temporal indices, the mean of all coupling intervals between normal beats (mRR), the standard deviation about the mean (sdRR), the percentage of adjacent R to R intervals differing by more than 50 msec (pNN50), and the root mean square of variations in successive R to R intervals (rMSSD) were compared at baseline and during head-up tilt between and within groups. Baseline results were similar in both groups. During tilt testing, comparison of results between groups revealed only significantly higher sdRR and rMSSD and lower LF/HF ratio in VVS patients. Within VVS patients, comparison of temporal and spectral analysis between baseline and tilt showed a significant increase of most indices (Plf, Phf, Pt, sdRR, and rMSSD) but a comparable LF/HF ratio; in contrast, control patients exhibited only a significant increase of LF/HF ratio. In conclusion, VVS patients who developed vasovagal syncope during head-up tilt demonstrated a nonreciprocal modulation of the sinus node by the autonomic nervous system indicative of a pronounced physiological sympathetic surge along with a paradoxical vagal input to the cardiovascular system.
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Affiliation(s)
- E Pruvot
- Division of Cardiology, C.H.U.V., Vaud, Switzerland
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