This study investigated the effects of dobutamine on left ventriculoarterial (VA) coupling and me... more This study investigated the effects of dobutamine on left ventriculoarterial (VA) coupling and mechanical efficiency in acutely ischemic pigs. Experiments were performed in 12 pigs in which vascular properties, including peripheral resistance (R2), compliance (C), and arterial elastance (Ea), were estimated with a windkessel model, and left ventricular (LV) function by the slope (Ees) of the end-systolic pressure-volume relationship (ESPVR) and stroke work (SW). VA coupling was defined as Ees/Ea, and mechanical efficiency as SW/pressure-volume area (PVA). In all animals, the left anterior descending coronary artery was ligated after basal measures. The animals were then randomly divided into 2 groups: group CTRL (n = 6) was followed for 180 minutes without other intervention, whereas group DOBU (n = 6) was infused with dobutamine (5 microg x kg(-1) x min(-1)) starting after T60 measures. Coronary occlusion induced a rightward shift of ESPVR and a decrease in Ees from 3.67 +/- 0.33 to 1.92 +/- 0.20 mm Hg x mL(-1), while Ea changed from 3.33 +/- 0.56 to 4.65 +/- 0.29 mm Hg x mL, R2 from 1.72 +/- 0.30 to 2.38 +/- 0.16 mm Hg x s x mL(-1), and C from 0.78 +/- 0.16 to 0.46 +/- 0.08 mL x mm Hg(-1). This altered VA coupling from 1.22 +/- 0.11 to 0.44 +/- 0.07. SW decreased from 4056 +/- 223 to 2372 +/- 122 mm Hg x mL, and PVA and SW/PVA decreased from 5575 +/- 514 to 4830 +/- 317 mm Hg x mL, and from 0.76 +/- 0.04 to 0.49 +/- 0.03, respectively. In group DOBU, dobutamine restored Ees and the position of ESPVR to baseline values, while Ea decreased to 3.39 +/- 0.34 mm Hg x mL(-1) because of an R2 decrease to 1.60 +/- 0.24 mm Hg x s x mL(-1). VA coupling was restored. SW and PVA increased to 3833 +/- 180 mm Hg x mL and to 7498 +/- 442 mm Hg x mL, respectively, while SW/PVA was unchanged. In ischemic pigs, dobutamine restored VA coupling through an increase in LV contractility and decrease in arterial elastance as a result of peripheral vasodilatation. However, myocardial oxygen consumption was increased, and mechanical efficiency impaired.
Computer Methods and Programs in Biomedicine, 2013
Located between the left atrium and the left ventricle, the mitral valve controls flow between th... more Located between the left atrium and the left ventricle, the mitral valve controls flow between these two cardiac chambers. Mitral valve dysfunction is a major cause of cardiac dysfunction and its dynamics are little known. A simple non-linear rotational spring model is developed and implemented to capture the dynamics of the mitral valve. A measured pressure difference curve was used as the input into the model, which represents an applied torque to the anatomical valve chords. A range of mechanical model hysteresis states were investigated to find a model that best matches reported animal data of chord movement during a heartbeat. The study is limited by the use of one dataset found in the literature due to the highly invasive nature of getting this data. However, results clearly highlight fundamental physiological issues, such as the damping and chord stiffness changing within one cardiac cycle, that would be directly represented in any mitral valve model and affect behaviour in dysfunction. Very good correlation was achieved between modeled and experimental valve angle with 1-10% absolute error in the best case, indicating good promise for future simulation of cardiac valvular dysfunction, such as mitral regurgitation or stenosis. In particular, the model provides a pathway to capturing these dysfunctions in terms of modeled stiffness or elastance that can be directly related to anatomical, structural defects and dysfunction.
ABSTRACT Since platelet aggregation is implicated in many pathological situations such as myocard... more ABSTRACT Since platelet aggregation is implicated in many pathological situations such as myocardial infarction, stroke, unstable angina and coronary artery disease, potent and safe antiplatelet agents would be useful for treating and preventing these diseases. Exposure of glycoprotein (GP)IIb/IIIa is the final common pathway leading to platelet activation and aggregate formation. Thus, the development of agents acting on this complex is an active area of research. Indeed, three GPIIb/IIIa antagonists are currently marketed but can only be intravenously administrated. Therefore, efforts are made to discover orally-active agents of this class, in order to use them for treatment of chronic disease or prevention of cardiovascular events. Although some clinical evaluation of orally-active compounds gave disappointing and discouraging results, research is still conducted to find compounds characterised by a better binding profile. This review describes 16 patents on new GPIIb/IIIa antagonists and more than 40 molecules characterised by strong activity against GPIIb/IIIa.
Optimal delivery of health care is a common goal of individual physicians, professional organizat... more Optimal delivery of health care is a common goal of individual physicians, professional organizations, hospital structures and governmental authorities. A growing concern has emerged from the public, media and third payer organizations concerning the quality of care and the amount of resources spending. In the United States, large databases, guidelines and performance evaluation have been elaborated by medical societies, particularly in the area of cardiac surgery. These tools are useful for improvement of patients' care, resources distribution, pay for performance and public and practitioners' awareness. The evaluation of quality is based on composite models combining structure, process and outcome indices. However, pitfalls such as patients' selection, and risk avoidance in order to improve results must been prevented by adjustment of the treated populations' risk factors by specific scores. The Belgian Health authorities have built a structure directed at delivery...
Bulletin et mémoires de l'Académie royale de médecine de Belgique, 2002
We quantified systemic ventriculo-arterial coupling in the pressure-volume (PV) plane, using a mo... more We quantified systemic ventriculo-arterial coupling in the pressure-volume (PV) plane, using a model of elastic chambers of the cardio-vascular system. In such a model, the ratio between left ventricular (LV) end-systolic elastance, and effective arterial elastance measures the coupling between the heart and the systemic vasculature, and the effects of cardiac diseases and of vasoactive agents on the coupling relationship can be independently evaluated in vivo. Furthermore, the analysis in the PV plane gives insights into LV mechanical efficiency, defined by the ratio between stroke work and pressure-volume area. Our results demonstrating that an augmentation of aortic compliance decreases the energetic cost of LV ejection should be considered when replacing the thoracic aorta by an artificial prosthesis. The homeometric autoregulation, suggesting a mechanism by which the heart can maintain a constant stroke volume, in the face of increased afterload, without using the Starling mech...
We evaluated prognostic factors in 34 patients discharged from hospital after surgical resection ... more We evaluated prognostic factors in 34 patients discharged from hospital after surgical resection for oesophageal squamous cell carcinoma. There were 22 males and 12 females; mean age was 59.3 years (range 42-77 years). Preoperative neoadjuvant treatment consisted in chemotherapy alone in three patients and in combined radiochemotherapy in 14. Digestive continuity was restored with a gastric transplant in 26 patients and a colonic graft in 8. Surgery was curative in 28 patients and palliative in 6. There were three stage I, 14 stage II, 13 stage III, and 4 stage IV diseases. In 19 patients the lymph nodes were invaded. The tumour was well differentiated in 17 patients, moderately in 9, and poorly in 8. Follow-up ranged from 2 to 100 months. Overall median postoperative survival was 21 months. By univariate analysis, factors influencing survival were curative surgery (p = 0.04), stage (p = 0.006), and nodal involvement (p = 0.0003). Nodal involvement was an independent prognostic fact...
This study investigated the effects of dobutamine on left ventriculoarterial (VA) coupling and me... more This study investigated the effects of dobutamine on left ventriculoarterial (VA) coupling and mechanical efficiency in acutely ischemic pigs. Experiments were performed in 12 pigs in which vascular properties, including peripheral resistance (R2), compliance (C), and arterial elastance (Ea), were estimated with a windkessel model, and left ventricular (LV) function by the slope (Ees) of the end-systolic pressure-volume relationship (ESPVR) and stroke work (SW). VA coupling was defined as Ees/Ea, and mechanical efficiency as SW/pressure-volume area (PVA). In all animals, the left anterior descending coronary artery was ligated after basal measures. The animals were then randomly divided into 2 groups: group CTRL (n = 6) was followed for 180 minutes without other intervention, whereas group DOBU (n = 6) was infused with dobutamine (5 microg x kg(-1) x min(-1)) starting after T60 measures. Coronary occlusion induced a rightward shift of ESPVR and a decrease in Ees from 3.67 +/- 0.33 to 1.92 +/- 0.20 mm Hg x mL(-1), while Ea changed from 3.33 +/- 0.56 to 4.65 +/- 0.29 mm Hg x mL, R2 from 1.72 +/- 0.30 to 2.38 +/- 0.16 mm Hg x s x mL(-1), and C from 0.78 +/- 0.16 to 0.46 +/- 0.08 mL x mm Hg(-1). This altered VA coupling from 1.22 +/- 0.11 to 0.44 +/- 0.07. SW decreased from 4056 +/- 223 to 2372 +/- 122 mm Hg x mL, and PVA and SW/PVA decreased from 5575 +/- 514 to 4830 +/- 317 mm Hg x mL, and from 0.76 +/- 0.04 to 0.49 +/- 0.03, respectively. In group DOBU, dobutamine restored Ees and the position of ESPVR to baseline values, while Ea decreased to 3.39 +/- 0.34 mm Hg x mL(-1) because of an R2 decrease to 1.60 +/- 0.24 mm Hg x s x mL(-1). VA coupling was restored. SW and PVA increased to 3833 +/- 180 mm Hg x mL and to 7498 +/- 442 mm Hg x mL, respectively, while SW/PVA was unchanged. In ischemic pigs, dobutamine restored VA coupling through an increase in LV contractility and decrease in arterial elastance as a result of peripheral vasodilatation. However, myocardial oxygen consumption was increased, and mechanical efficiency impaired.
Computer Methods and Programs in Biomedicine, 2013
Located between the left atrium and the left ventricle, the mitral valve controls flow between th... more Located between the left atrium and the left ventricle, the mitral valve controls flow between these two cardiac chambers. Mitral valve dysfunction is a major cause of cardiac dysfunction and its dynamics are little known. A simple non-linear rotational spring model is developed and implemented to capture the dynamics of the mitral valve. A measured pressure difference curve was used as the input into the model, which represents an applied torque to the anatomical valve chords. A range of mechanical model hysteresis states were investigated to find a model that best matches reported animal data of chord movement during a heartbeat. The study is limited by the use of one dataset found in the literature due to the highly invasive nature of getting this data. However, results clearly highlight fundamental physiological issues, such as the damping and chord stiffness changing within one cardiac cycle, that would be directly represented in any mitral valve model and affect behaviour in dysfunction. Very good correlation was achieved between modeled and experimental valve angle with 1-10% absolute error in the best case, indicating good promise for future simulation of cardiac valvular dysfunction, such as mitral regurgitation or stenosis. In particular, the model provides a pathway to capturing these dysfunctions in terms of modeled stiffness or elastance that can be directly related to anatomical, structural defects and dysfunction.
ABSTRACT Since platelet aggregation is implicated in many pathological situations such as myocard... more ABSTRACT Since platelet aggregation is implicated in many pathological situations such as myocardial infarction, stroke, unstable angina and coronary artery disease, potent and safe antiplatelet agents would be useful for treating and preventing these diseases. Exposure of glycoprotein (GP)IIb/IIIa is the final common pathway leading to platelet activation and aggregate formation. Thus, the development of agents acting on this complex is an active area of research. Indeed, three GPIIb/IIIa antagonists are currently marketed but can only be intravenously administrated. Therefore, efforts are made to discover orally-active agents of this class, in order to use them for treatment of chronic disease or prevention of cardiovascular events. Although some clinical evaluation of orally-active compounds gave disappointing and discouraging results, research is still conducted to find compounds characterised by a better binding profile. This review describes 16 patents on new GPIIb/IIIa antagonists and more than 40 molecules characterised by strong activity against GPIIb/IIIa.
Optimal delivery of health care is a common goal of individual physicians, professional organizat... more Optimal delivery of health care is a common goal of individual physicians, professional organizations, hospital structures and governmental authorities. A growing concern has emerged from the public, media and third payer organizations concerning the quality of care and the amount of resources spending. In the United States, large databases, guidelines and performance evaluation have been elaborated by medical societies, particularly in the area of cardiac surgery. These tools are useful for improvement of patients' care, resources distribution, pay for performance and public and practitioners' awareness. The evaluation of quality is based on composite models combining structure, process and outcome indices. However, pitfalls such as patients' selection, and risk avoidance in order to improve results must been prevented by adjustment of the treated populations' risk factors by specific scores. The Belgian Health authorities have built a structure directed at delivery...
Bulletin et mémoires de l'Académie royale de médecine de Belgique, 2002
We quantified systemic ventriculo-arterial coupling in the pressure-volume (PV) plane, using a mo... more We quantified systemic ventriculo-arterial coupling in the pressure-volume (PV) plane, using a model of elastic chambers of the cardio-vascular system. In such a model, the ratio between left ventricular (LV) end-systolic elastance, and effective arterial elastance measures the coupling between the heart and the systemic vasculature, and the effects of cardiac diseases and of vasoactive agents on the coupling relationship can be independently evaluated in vivo. Furthermore, the analysis in the PV plane gives insights into LV mechanical efficiency, defined by the ratio between stroke work and pressure-volume area. Our results demonstrating that an augmentation of aortic compliance decreases the energetic cost of LV ejection should be considered when replacing the thoracic aorta by an artificial prosthesis. The homeometric autoregulation, suggesting a mechanism by which the heart can maintain a constant stroke volume, in the face of increased afterload, without using the Starling mech...
We evaluated prognostic factors in 34 patients discharged from hospital after surgical resection ... more We evaluated prognostic factors in 34 patients discharged from hospital after surgical resection for oesophageal squamous cell carcinoma. There were 22 males and 12 females; mean age was 59.3 years (range 42-77 years). Preoperative neoadjuvant treatment consisted in chemotherapy alone in three patients and in combined radiochemotherapy in 14. Digestive continuity was restored with a gastric transplant in 26 patients and a colonic graft in 8. Surgery was curative in 28 patients and palliative in 6. There were three stage I, 14 stage II, 13 stage III, and 4 stage IV diseases. In 19 patients the lymph nodes were invaded. The tumour was well differentiated in 17 patients, moderately in 9, and poorly in 8. Follow-up ranged from 2 to 100 months. Overall median postoperative survival was 21 months. By univariate analysis, factors influencing survival were curative surgery (p = 0.04), stage (p = 0.006), and nodal involvement (p = 0.0003). Nodal involvement was an independent prognostic fact...
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