Juan Manuel Camus

Adventitia-dependent mechanical properties of brachiocephalic ovine arteries in in vivo and in vitro studies

Aim:  An adventitia dependent regulation of the vascular smooth muscle tone has been described. However, if the adventitia plays an active role on arterial wall biomechanical behaviour and functions remains to be established. Our aim was to characterize the influence of adventitia on arterial wall mechanical properties and the arterial conduit and buffer functions.

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.

Effects of intra-aortic counterpulsation on aortic wall energetics and damping: in vivo experiments.

Intra-aortic balloon pumping (IABP) could modify the arterial biomechanics; however, its effects on arterial wall properties have not been fully explored. This dynamical study was designed to characterize the pressure-dependent and smooth muscle-dependent effects of IABP on aortic wall energetics in an in vivo animal model. Intra-aortic balloon pumping (1:2) was performed in six anesthetized sheep in which aortic pressure and diameter signals were measured in basal, augmented (during balloon inflation), and assisted (postaugmented) beats. Energy dissipation values in augmented and assisted beats were significantly higher than those observed in basal state (p < 0.05). Assisted beats showed a significant increase of wall damping with respect to basal and augmented beats (p < 0.05). Intra-aortic balloon pumping resulted in a significant increase of pulse wave velocity (p < 0.05) in augmented beats with respect to basal state (6.3 ± 0.8 vs. 5.2 ± 0.5 m·s−1); whereas values observed in assisted beats were significantly (p < 0.05) lower than those observed in augmented beats (4.9 ± 0.5 vs. 6.3 ± 0.8 m·s−1). Our findings show that IABP determined the pressure and smooth muscle-dependent changes in arterial wall energetics and damping properties in this animal model.

La adventicia reduce la poscarga dinámica ventricular izquierda mediante mecanismos dependientes de la activación muscular lisa

Introduccion y objetivos. Las propiedades viscoelasticas y geometricas arteriales determinan la poscarga dinamica ventricular. Factores vasoactivos producidos en la adventicia modulan el tono arterial. Resta por establecer si la adventicia participa en la determinacion del valor de poscarga dinamica. El objetivo de este estudio fue caracterizar el papel de la adventicia en la determinacion de la poscarga dinamica mediante mecanismos dependientes del musculo liso. Metodos. La presion, el diametro y el flujo se midieron en troncos braquiocefalicos ovinos antes y despues de extraerles la adventicia, en estudios in vivo con reactividad muscular intacta (n = 8) e in vitro con reactividad muscular abolida (n = 8). Las arterias se estudiaron en condiciones hemodinamicas similares. La poscarga dinamica se caracterizo mediante la respuesta elastica y viscosa arterial, el trabajo elastico y viscoso, la impedancia caracteristica arterial y la velocidad de propagacion del pulso. Comparar los estudios in vivo e in vitro permitio caracterizar los cambios en la activacion dependientes del musculo. Resultados. Solo in vivo la extraccion de la adventicia determino una reduccion del diametro (desde 17,32 ± 2,02 hasta 15,46 ± 1,28 mm) e incrementos en las respuestas elastica (desde 7,21 ± 1,39 hasta 15,59 ± 3,00 106 dinas · cm-2) y viscosa (desde 5,16 ± 2,04 hasta 9,87 ± 2,00 105 dinas · cm-2), en los trabajos elastico (desde 6,15 ± 1,08 hasta 9,20 ± 0,76 x 10-2 J/m2) y viscoso (desde 11,61 ± 2,25 hasta 15,20 ± 2,37 x 10-3 J/m2), en la impedancia arterial (desde 223,97 ± 136,11 hasta 396,33 ± 182,27 dinas · s · cm-3) y velocidad de propagacion (desde 397,70 ± 31,21 hasta 598,78 ± 28,04 cm · s-1) (p < 0,05). El menor diametro y los aumentos en las respuestas elastica y viscosa evidenciaron la activacion muscular. Conclusiones. La adventicia participaria en el control de la poscarga dinamica ventricular mediante mecanismos dependientes del tono muscular

The Adventitia Reduces Left Ventricular Dynamic Afterload Via Smooth Muscle Activation-Dependent Mechanisms

INTRODUCTION AND OBJECTIVES Ventricular dynamic afterload depends on arterial viscoelastic and geometric properties. Vasoactive factors produced in the adventitia modulate arterial tone. However, it is still not known whether the adventitia is involved in determining the magnitude of the dynamic afterload. The aim of this study was to investigate the role played by the adventitia, via smooth muscle-dependent mechanisms, in determining dynamic afterload. METHODS The diameter, pressure and flow in brachiocephalic trunks from sheep were measured before and after removal of the adventitia, both in vivo with muscular reactivity preserved (n=8) and in vitro with muscular reactivity abolished (n=8). All studies were performed under similar hemodynamic conditions. Dynamic afterload was determined from elastic and viscous arterial responses, elastic and viscous work, arterial characteristic impedance, and pulse wave velocity. Comparison of in vivo and in vitro findings enabled smooth muscle-dependent changes to be evaluated. RESULTS Only in vivo, did removal of the adventitia lead to a reduction in vessel diameter (17.32 [2.02] vs 15.46 [1.28] mm) and to increases in elastic (7.21 [1.39] vs 15.59 [3.00] x 10(6) dyn.cm(-2)) and viscous (5.16 [2.04] vs 9.87 [2.00] x 10(5) dyn.s.cm(-2)) arterial responses, elastic (6.15 [1.08] vs 9.20 [0.76] x 10(-2) J/m2) and viscous work (11.61 [2.25] vs 15.20 [2.37] x 10(-3) J/m2), impedance (223.97 [136.11] vs 396.33 [182.27] dyn x s x cm(-3)), and pulse wave velocity (397.70 [31.21] vs 598.78 [28.04] cm.s(-1)) (P<.05). The reduction in diameter and the increases in elastic and viscous responses are evidence of muscular activation. CONCLUSIONS The adventitia may contribute to the control of ventricular dynamic afterload by means of mechanisms dependent on muscular tone.