Patient-specific modelling of the cardiovascular system – application to septic shock with a minimal data set,

in World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany (2010)

Mitral valve dynamics in a closed-loop model of the cardiovascular system

Poster (2009, December 17)

A cardiovascular and circulatory system (CVS) model has been validated in silico, and in several animal model studies. It accounts for valve dynamics by means of Heaviside function to simulate “open on ... [more ▼]

A cardiovascular and circulatory system (CVS) model has been validated in silico, and in several animal model studies. It accounts for valve dynamics by means of Heaviside function to simulate “open on pressure, close on flow” law. Thus, it does not consider the real time scale of the valve aperture and thus doesn’t fully capture valve dysfunction. This research couples the CVS model with a model describing the progressive aperture of the mitral valve. [less ▲]

Le couplage ventriculoartériel : du concept aux applications cliniques

in Réanimation (2009), 18(3), 201-206

L’interaction entre le ventricule et le réseau vasculaire est un déterminant majeur de la performance cardiaque globale, particulièrement en présence d’une insuffisance ventriculaire préalable ... [more ▼]

L’interaction entre le ventricule et le réseau vasculaire est un déterminant majeur de la performance cardiaque globale, particulièrement en présence d’une insuffisance ventriculaire préalable. L’évaluation du couplage ventriculoartériel grâce à la mesure de l’élastance ventriculaire, comme reflet de la contractilité et de l’élastance artérielle, en tant qu’indice de post-charge, permet de quantifier cette interaction. Des travaux récents illustrent l’intérêt clinique de ce concept. Jusqu’à présent, son utilisation restait toutefois marginale en raison de la nécessité de recourir à des mesures invasives et complexes. Le développement des techniques d’imagerie non invasive et de traitement des signaux permet actuellement d’envisager l’utilisation de ce concept en pratique clinique courante. [less ▲]

Unique parameter identification for model-based cardiac diagnosis in critical care

in IFAC Proceedings Volumes (IFAC-PapersOnline) (2009), 7(PART 1), 169-174

Lumped parameter approaches for modeling the cardiovascular system typically have many parameters of which many are not identifiable. The conventional approach is to only identify a small subset of ... [more ▼]

Lumped parameter approaches for modeling the cardiovascular system typically have many parameters of which many are not identifiable. The conventional approach is to only identify a small subset of parameters to match measured data, and to set the remaining parameters at population values. These values are often based on animal data or the "average human" response. The problem, is that setting many parameters at nominal fixed values, may introduce dynamics that are not present in a specific patient. As parameter numbers and model complexity increase, more clinical data is required for validation and the model limitations are harder to quantify. This paper considers the modeling and the parameter identification simultaneously, and creates models that are one to one with the measurements. That is, every input parameter into the model is uniquely optimized to capture the clinical data and no parameters are set at population values. The result is a geometrical characterization of a previously developed six chamber heart model, and a completely patient specific approach to cardiac diagnosis in critical care. In addition, simplified sub-structures of the six chamber model are created to provide very fast and accurate parameter identification from arbitrary starting points and with no prior knowledge on the parameters. Furthermore, by utilizing continuous information from the arterial/pulmonary pressure waveforms and the end-diastolic time, it is shown that only the stroke volumes of the ventricles are required for adequate cardiac diagnosis. This reduced data set is more practical for an intensive care unit as the maximum and minimum volumes are no longer needed, which was a requirement in prior work. The simplified models can also act as a bridge to identifying more sophisticated cardiac models, by providing a generating set of waveforms that the complex models can match to. Most importantly, this approach does not have any predefined assumptions on patient dynamics other than the basic model structure, and is thus suitable for improving cardiovascular management in critical care by optimizing therapy for individual patients. © 2009 IFAC. [less ▲]

Robust parameter identification for model-based cardiac diagnosis in critical care

in Proceedings of the 6th IFAC Symposium on Modeling and Control in Biomedical Systems (MCBMS09) (2009)

Model-based therapeutics for the cardiovascular system - a clinical focus

in 6th IFAC Symposium on Modeling and Control in Biomedical Systems (MCBMS09) (2009)

Guideline for resuscitation in cardiac arrest after cardiac surgery.

in European Journal of Cardio - Thoracic Surgery (2009), 36(1), 3-28

The Clinical Guidelines Committee of the European Association for Cardio-Thoracic Surgery provides this professional view on resuscitation in cardiac arrest after cardiac surgery. This document was ... [more ▼]

The Clinical Guidelines Committee of the European Association for Cardio-Thoracic Surgery provides this professional view on resuscitation in cardiac arrest after cardiac surgery. This document was created using a multimodal methodology for evidence generation including the extrapolation of existing guidelines from the International Liaison Committee on Resuscitation where possible, our own structured literature reviews on issues particular to cardiac surgery, an international survey on resuscitation hosted by CTSNet and manikin simulations of potential protocols. This protocol differs from existing generic guidelines in a number of areas, the most import of which are the following: successful treatment of cardiac arrest after cardiac surgery is a multi-practitioner activity with six key roles that should be allocated and rehearsed on a regular basis; in ventricular fibrillation, three sequential attempts at defibrillation (where immediately available) should precede external cardiac massage; in asystole or extreme bradycardia, pacing (where immediately available) should precede external cardiac massage; where the above measures fail, and in pulseless electrical activity, early resternotomy is advocated; adrenaline should not be routinely given; protocols for excluding reversible airway and breathing complications and for safe emergency resternotomy are given. This guideline is subject to continuous informal review, and when new evidence becomes available. [less ▲]

Haemodynamic properties of a distal Y-shaped arterial autograft bypass-flap in a porcine model: changes from elastic to viscoelastic mechanical behaviour?

in European Journal of Vascular and Endovascular Surgery (2009), 37(1), 85-6

Effective arterial elastance as an index of pulmonary vascular load.

in American Journal of Physiology - Heart and Circulatory Physiology (2008), 294(6), 2736-42

The aim of this study was to test whether the simple ratio of right ventricular (RV) end-systolic pressure (Pes) to stroke volume (SV), known as the effective arterial elastance (Ea), provides a valid ... [more ▼]

The aim of this study was to test whether the simple ratio of right ventricular (RV) end-systolic pressure (Pes) to stroke volume (SV), known as the effective arterial elastance (Ea), provides a valid assessment of pulmonary arterial load in case of pulmonary embolism- or endotoxin-induced pulmonary hypertension. Ventricular pressure-volume (PV) data (obtained with conductance catheters) and invasive pulmonary arterial pressure and flow waveforms were simultaneously recorded in two groups of six pure Pietran pigs, submitted either to pulmonary embolism (group A) or endotoxic shock (group B). Measurements were obtained at baseline and each 30 min after injection of autologous blood clots (0.3 g/kg) in the superior vena cava in group A and after endotoxin infusion in group B. Two methods of calculation of pulmonary arterial load were compared. On one hand, Ea provided by using three-element windkessel model (WK) of the pulmonary arterial system [Ea(WK)] was referred to as standard computation. On the other hand, similar to the systemic circulation, Ea was assessed as the ratio of RV Pes to SV [Ea(PV) = Pes/SV]. In both groups, although the correlation between Ea(PV) and Ea(WK) was excellent over a broad range of altered conditions, Ea(PV) systematically overestimated Ea(WK). This offset disappeared when left atrial pressure (Pla) was incorporated into Ea [Ea * (PV) = (Pes - Pla)/SV]. Thus Ea * (PV), defined as the ratio of RV Pes minus Pla to SV, provides a convenient, useful, and simple method to assess the pulmonary arterial load and its impact on the RV function. [less ▲]

Open surgery for abdominal aortic aneurysm or aorto-iliac occlusive disease--clinical and ultrasonographic long-term results.

in Acta Chirurgica Belgica (2008), 108(4), 393-9

OBJECTIVE: To determine postoperative and long-term outcome and assess the relevance of abdominal ultrasound (US) after surgery for abdominal aortic aneurysm (AAA) or aortoiliac occlusive disease (AIOD ... [more ▼]

OBJECTIVE: To determine postoperative and long-term outcome and assess the relevance of abdominal ultrasound (US) after surgery for abdominal aortic aneurysm (AAA) or aortoiliac occlusive disease (AIOD). METHODS: Records of 1704 consecutive patients having graft implantation from 1988 to 2000, either for AAA (n = 1144) or for AIOD (n = 560), were reviewed. In 2006, follow-up was 9180 patients-years for the AAA group and 5450 patients-years for the AIOD group. Among 1006 alive patients, 377 were invited randomly for US and clinical examination. RESULTS: Hospital death occurred in 99 patients (8.6%) of the AAA group (53% in ruptured and 2% in elective AAA), and in 18 patients of the AIOD group (3.2%). There were 581 late deaths, including eight due to prosthesis infection, one to pseudo-aneurysm rupture, and one to graft thrombosis (0.6% graft-related mortality). Prosthesis thrombosis occurred in 32 patients (26 in AIOD group, p < 0.001), and graft infection in 26 (17 in AAA group, p < 0.01). Pseudoaneurysms developed in 90 patients (68 in AIOD group, p < 0.001), including eight at the proximal aortic, one at the distal aortic, two at the iliac and 79 at the femoral anastomosis. In the AAA group only, surgery was required for a new thoraco-abdominal and pararenal aneurysm in eight and four patients, respectively, while US evidenced a 26-35 and a 36-50 mm supraanastomotic aortic dilatation in 65 (32%) and in 14 (7%) patients, at a mean follow-up of 10.5 and 9.3 years, respectively. CONCLUSION: Long-term results are good after open surgery for AAA or AIOD. Prosthesis infection and anastomotic pseudo-aneurysm are the main causes of graft-related mortality and morbidity, respectively. Because of high incidence of asymptomatic supraanastomotic aortic dilatation, all patients with a history of AAA repair should have regular abdominal US. [less ▲]