Franco Pessana

Gender Differences in Wall Shear-Mediated Brachial Artery Vasoconstriction and Vasodilation

OBJECTIVESnWe sought to investigate wall shear rate (WSR) and brachial artery diameter (BAD) changes simultaneously and to determine whether any gender differences exist in arterial reactivity.nnnBACKGROUNDnWall shear rate/stress and arterial reactivity are rarely assessed at the same time. Furthermore, flow-mediated vasoconstriction has received less attention than flow-mediated vasodilation in humans.nnnMETHODSnA new noninvasive evaluation of WSR in the brachial artery, using multigated, pulsed Doppler velocimeter and a double-transducer probe moved and fixed by a robotic system, was developed.nnnRESULTSnThe validity of the system was tested in vitro with calibrated tubes and showed a high correlation (r = 0.98, p < 0.001). In 10 men and 10 women of similar age, induction of low and high shear rates by forearm occlusion produced significant vasoconstriction and vasodilation, respectively. The time lag for maximal BAD changes was 3 min for vasoconstriction and 1 min for vasodilation. A greater half-time for vasodilation (96 +/- 6 for men and 86 +/- 12 s for women) than for shear rate (31 +/- 5 s for men and 34 +/- 4 s for women) was observed after discontinuation of occlusion. Relative BAD was correlated with WSR changes, showing a significantly higher slope in women than in men (p < 0.01). Moreover, a larger normalized arterial diameter per shear rate was observed for vasoconstriction (p < 0.01) and vasodilation (p < 0.01) in women than in men.nnnCONCLUSIONSnShear-mediated arterial vasodilation and vasoconstriction were more pronounced in women than in men, suggesting different gender-related sensitivity in the regulation of large-artery vascular tone.

Juxtaaortic counterpulsation: comparison with intraaortic counterpulsation in an animal model of acute heart failure.

This study was designed to compare the effects of juxtaaortic balloon counterpulsation (JABC), performed in ascending aorta and the aortic arch, with those yielded by intraaortic balloon counterpulsation (IABC) in descending aorta, in experimental animals during induced cardiac failure.JABC was achieved with a manufactured Dacron prosthesis and a balloon pump placed between the prosthesis and the wrapped aorta.JABC resulted in a significant increase of cardiac output (from 2.33 ± 0.82 to 2.61 ± 1.12 L/min, p < 0.05), cardiac index (from 0.071 ± 0.025 to 0.080 ± 0.033 L/min/kg, p < 0.05) and diastolic pressure augmentation evaluated through diastolic and systolic areas beneath the aortic pressure curve (DABAC/SABAC) index (from 0.94 ± 0.21 to 1.10 ± 0.33, p < 0.01). End diastolic aortic pressure showed a significant decrease with JABC (from 31.90 ± 7.09 to 27.83 ± 9.72 mm Hg, p < 0.05). A close association between percentage of DABAC/SABAC increases obtained with IABC and JABC was observed (r2 = 0.67; p < 0.001).Counterpulsation obtained by a juxtaaortic catheter placed in the arch and the ascending wrapped aorta results in an effective hemodynamic improvement comparable with that achieved by an intraaortic catheter in open chest sheep.

Non-symmetrical double-logistic analysis of 24 hour arterial stiffness profile in normotensive and hypertensive subjects

Objectives: Mechanisms underlying the circadian profile of cardiovascular events (CE) are not totally understood. Whether circadian changes in arterial stiffness (AS) could be related to the circadian profile of CE remains to be investigated. As yet, there is no accepted way to measure circadian profiles or nocturnal-related and/or morning-related changes in cardiovascular variables. The aim of this study was to characterize the circadian pattern and day-night and night-day changes of AS in untreated hypertensive (HG) and healthy subjects (NG), using a recently developed non-symmetrical six-parameter double-logistic model. Methods: Seven hypertensive and seven normotensive subjects underwent 24 hour ambulatory recordings of blood pressure (BP), heart rate (HR) and aorto-brachial pulse transit time (PTTAB) and pulse transit velocity index (PTVAB). PTTAB and PTVAB are inversely and directly related to AS, respectively. The circadian profile and transitional periods (day-night and night-day) were analyzed using a model described by a six-parameter double logistic equation. Conclusions: The model was adequate to characterize the circadian pattern of AS. We provide the first evidence that AS in humans follows an asymmetric circadian pattern and that this differs between NG and HG. In both NG and HG, AS had a circadian profile, with the highest levels in the night. HG showed larger levels of AS, larger BP variations and rate of change and minor changes in AS during transitional periods.

Upgrading BME studies in Buenos Aires, Argentine. Favaloro University

The Favaloro University initiated the academic path in biomedical sciences in Buenos Aires, Argentina. As a very promising area, the biomedical world offers the integration between several domains, complementing medicine with engineering topics. The profile of the graduated students proved to be very versatile, allowing their instantaneous incorporation to the competitive market in this vast field. The university strategy is to concentrate basic science in the first 3 years and add the specific biological/medical concepts in the last 2 years. The students achieve a bachelor degree that integrates their knowledge in basic sciences. Afterwards, they attend a professional 2 year cycle, choosing between biomedical, physics and medical computing branches. The results proved to be effective in terms of professional and academic quality, market insertion and even the creation of promising seeds for future enterprises

Subclinical atherosclerosis modeling: Integration of coronary artery calcium score to framingham equation

Medical prevention consists to identify as soon as possible apparently healthy individuals who develop a disease and to engage them for active preventive treatment. Several cross-sectional studies of general populations or high cardiovascular risk have shown that coronary calcium score (coronary artery calcium, CAC) was positively associated with traditional risk factors (hypertension, dyslipidemia, diabetes, and smoking) and some new risk factors (fibrinogen). In this work, we first calculated, among 618 men, the risk of 10-years cardiovascular heart disease (CHD) according to the Framingham risk model, and then we calculated the probability that the CAC score of an individual falls in all four CAC categories (0, 1-100, 101-400 and > 400). We obtained risk factors adjusted relative risk (RR) estimates from a meta-analysis comparing the risk of coronary heart disease in individuals with CAC scores of 1-100 (RR = 3D 1.7), 101 - 400 (RR = 3D 3.0) and> 400 (RR = 3D 4.3) with the risk of a person with a CAC score zero. The new model for the risk of CHD for each CAC score category were then calculated assuming an average 1-year risk of CHD and risk assessment of the four CAC score categories, weighted by the probability that scores fall into each category. The combination of modeling the CCA with the modeling of conventional risk factors allows obtaining a remarkable predictive value that can improve the assessment of overall risk Framingham through the reclassification of the risk of CHD to an extent which may be clinically important.

Adaptive Filtering of the Arterial Wall. Frequency Response and Dynamical Parameters. Clinical Evaluation

Adaptive identification systems focus on dynamical approaches based on the observed data from an experiment and/or clinical data. These systems establish a relationship between an input (arterial or vein instantaneous pressure) and an output (instantaneous arterial or vein diameter). Several dynamics relationships and applications can be established because of this adaptive identification as an arterial dynamic range (frequency response), biomechanical behavior of cryopreserved arteries, regional differences in veins as artery substitution, role of vascular smooth muscle in human hypertension and time invariance in the biomechanics of wall arteries. The aim of this review is to summarize some of those relevant results obtained from adaptive filter identification in cardiovascular dynamics research and clinical evaluation.

Flow behavior and applicability of models for different hemodynamic states

Arterial behavior analysis requires an accurate and dynamic knowledge of the stimuli and reactions involved. Belonging parameters quantification is performed by a data acquisition process and the application of existing models. However, it turns essentially to analyze the adjustment degree of the aforementioned models in terms of the arterial tree. Blood flow behavior as well as wall shear rate and the arterial compliance are anatomic location dependent. The main objective of the present work is to analyze the existing functional relationships between arterial wall and blood flow, in a particular place (brachial artery), in order to asses the specific model applicability, in cases such Poiseuille or Womersley models. In addition, due to the characteristic of the study, gender differential dynamic responses will be evaluated.