Chronic effects of arterial balloon dilatation on internal mammary artery endothelial function

BACKGROUND

Manipulation for harvesting of the internal mammary artery (IMA) for coronary artery bypass grafting has been shown to acutely impair endothelium-dependent, but not endothelium-independent contractions and relaxations. Recently the use of a novel arterial balloon catheter to dilate the IMA has shown an increased IMA flow while preserving endothelial cell integrity and function acutely. This study examines the chronic effects on endothelial function of IMA segments subjected to arterial balloon catheter dilatation in comparison to either no manipulation (control), luminal dilatation with papaverine, or temporary occlusion with soft or hard jaw in a porcine model.

METHODS

Porcine IMAs were harvested one month after instrumentation. Ten IMA segments in each group were obtained and placed in organ chambers under isometric tension. Maximal endothelium-dependent contractions with arachidonic acid and relaxations with acetylcholine, and endothelium-independent contractions with norepinephrine and relaxations with sodium nitroprusside were measured.

RESULTS

Endothelium-dependent contractions and relaxations were significantly impaired after hard jaw occlusion one month after IMA manipulation compared to control, long balloon, fibrous jaw, and papaverine groups. Endothelium-independent contractions and relaxations of IMA smooth muscle were unaffected at one month after manipulation.

CONCLUSION

We conclude that arterial long balloon dilatation is not detrimental to endothelial cell function chronically and is therefore an effective and atraumatic method to relieve IMA spasm before coronary bypass grafting.

Arterial balloon catheter: a new atraumatic device for dilating arterial grafts

BACKGROUND

Harvesting of the internal mammary artery (IMA) for use in myocardial revascularization may result in spasm, which can impair early graft flow. Hydrostatic and mechanical dilatation can exert an intraluminal shear force, causing denudation of the IMA endothelium. A new long balloon dilatation technique (LB) has been developed to mechanically increase IMA diameter and flow without exerting any shear force on the endothelium.

METHODS

Vascular rings of porcine IMA were divided into four groups: no manipulation (control), metal dilators (MD), short balloon (SB), or LB intraluminal dilation. In situ flows after dilation and percentage of intact endothelium after silver nitrate staining were determined. Endothelium-dependent contractions with arachidonic acid, relaxations with acetylcholine, endothelium-independent contractions with norepinephrine, and relaxation with sodium nitroprusside were recorded in organ chamber experiments.

RESULTS

Increases in IMA flows were similar in all dilated groups. Endothelium-independent contractions and relaxations of IMA smooth muscle were unaffected by any type of mechanical dilation. However, endothelium-dependent contractions and relaxations were significantly impaired after MD and SB but preserved after LB dilation compared with control. Silver nitrate staining showed a greater preservation of the endothelial coverage after LB dilation.

CONCLUSIONS

IMA dilatation with the novel arterial LB catheter increases IMA flow and preserves endothelial cell integrity, making it an effective and atraumatic method to relieve IMA spasm before use for coronary artery bypass grafting.

Effects of occlusion devices for minimally invasive coronary artery bypass surgery on coronary endothelial function of atherosclerotic arteries

BACKGROUND

During minimally invasive coronary artery bypass grafting surgery, technical devices are required to obtain an optimal operative field. However, these devices can cause lesions to the endothelium. Previous studies of the effect of devices on coronary endothelial function have been performed on normal coronary arteries. Balloon denudation is followed by regeneration of the endothelium, which is dysfunctional and by intimal hyperplasia resembling atherosclerosis. The Anastaflo (Baxter, Mississauga, Ontario, Canada) shunt is a surgical device used during the performance of coronary anastomoses that allows a continuous flow inside the artery during the surgery.

METHODS

We compared the effects of three commonly used techniques on endothelial function: 1) using the Anastaflo shunt, 2) using Retract-o-tape (Genzyme, Cambridge, MA) silicone air cushion snaring, and 3) using a bulldog clamp on arteries submitted to balloon denudation 30 days prior to the surgical experiment on an in vivo model of beating heart off-pump coronary artery bypass (OPCAB). Balloon denudation was performed on the left anterior descending artery and on the right coronary artery. The devices were applied for 15 minutes on porcine epicardial coronary arteries, on the beating heart, after median sternotomy. Denuded control rings were taken at the site of denudation on which no devices were applied while non-denuded control rings were taken from the left circumflex artery. The endothelial function of control and instrumented arterial rings was studied in organ chambers filled with a modified Krebs-Ringer bicarbonate solution. After contraction to prostaglandin F(2)alpha, endothelium-dependent relaxation to serotonin (an agonist coupled to Gi-proteins) and bradykinin (a non-Gi-protein coupled agonist) were compared in the shunting group, the snaring group, the clamping group, and in controls.

RESULTS

There was a significant decrease in the relaxations to serotonin and bradykinin in the denuded control group compared with the non-denuded control group, confirming that balloon denudation caused an endothelial dysfunction. However, there was no significant difference between the denuded control group and the hemostatic device groups (shunting, snaring and clamping) in the relaxation to serotonin.

CONCLUSION

These results suggest that hemostatic devices used for OPCAB do not cause any greater injury in atherosclerotic coronary arteries already harbouring an endothelial dysfunction. The effects on platelet aggregation, intimal dissection, and plaque rupture remain to be determined.

Improved preservation of coronary endothelial function with Celsior compared with blood and crystalloid solutions in heart transplantation

BACKGROUND

Endothelial injury from preservation solutions has been implicated in acute coronary vasospasm and pathologic activation of the endothelium, which can contribute to the development of graft coronary vasculopathy after heart transplantation. Preservation solutions with a powerful antioxidant capacity may decrease the occurrence of these complications.

MATERIALS AND METHODS

This study was designed to evaluate the effect of Celsior (an anti-oxidant solution specifically designed for cardiac preservation) in a model of heart preservation (4 hours at 4 degrees C to reproduce the situation encountered in clinical heart transplantation) compared two commonly used cardioplegic and preservation strategies on coronary endothelial function. Endothelium-dependent relaxation of normal porcine epicardial coronary arteries to serotonin (5-HT, an agonist that activates 5-HT(1d) receptors coupled to Gi proteins) and bradykinin (BK, which activates B2 receptors coupled to Gq proteins) was studied in standard organ chamber experiments in the following groups: a control group was submitted to immediate excision without cardioplegia and preserved in saline solution (0.9% NaCl) for 4 hours (Group 1); two groups had cardioplegia induced with a crystalloid solution and were stored for 4 hours in saline (Group 2) or 4 hours in Celsior solution (Group 3); and two groups had cardioplegia induced with normothermic blood cardioplegia and were stored for 4 hours in the saline (Group 4), or 4 hours in Celsior solution (Group 5). Finally, two groups underwent cardioplegia with Celsior and were stored for 4 hours in saline (Group 6), or 4 hours in the Celsior solution (Group 7). All cardioplegia solutions were at 4 degrees C (except blood cardioplegia at 37 degrees C) and all preservations solutions were at 4 degrees C.

RESULTS

Endothelium-dependent relaxations to serotonin were significantly decreased in all groups except the Celsior + Celsior group compared with the control group. There were no significant differences in relaxation to bradykinin except in one group. Use of the Celsior solution for induction of cardioplegia and storage better preserved endothelium-dependent G-protein-mediated relaxation compared with the other arrest and preservation strategies.

CONCLUSIONS

The observed effect may be associated with an improvement in both short- and long-term outcome in heart transplantation, especially because these alterations may be further compounded by reperfusion.

Effects on coronary endothelial function of the Cohn stabilizer for beating heart bypass operations

BACKGROUND

The effects of different stabilizing methods for minimally invasive beating heart coronary artery bypass grafts (CABG) on coronary endothelial function are unknown.

METHODS

We compared the effects on endothelial function of the Cohn stabilizer (used with proximal snaring by Retract-o-tape silicone air cushion) and a coronary shunt (CTS flow coil shunt) on an in vivo model of beating heart CABG. The two techniques were applied for 15 minutes on porcine epicardial coronary arteries. Control rings were taken from the same coronary artery. Endothelial function of control and instrumented arterial rings was studied in organ chamber experiments. Evaluation of endothelial coverage was performed with silver nitrate staining.

RESULTS

Endothelium-dependent relaxation to serotonin and bradykinin was significantly decreased in the shunt group compared to control, Cohn stabilizer, and snare groups. There were no significant differences in the endothelium-independent relaxation to sodium nitroprusside between groups.

CONCLUSIONS

Greater endothelium-dependent relaxation with the Cohn stabilizer suggests better preservation of endothelial coverage at the site of application and reduced propensity for coronary spasm and later development of intimal hyperplasia.

Parental support: effects of a mass-media intervention

Although face-to-face parental support programs have been shown to improve parents' knowledge, attitudes and behaviour, such interventions are relatively costly to administer. This article reports the findings of a quasi-experimental evaluation of a relatively less costly, mass-media intervention: an age-paced newsletter for new parents. Readership and effectiveness of the newsletter were assessed after three years of distribution. Evaluation participants were 453 randomly selected fathers and mothers of three-year-olds, of which 193 were newsletter recipients and 260 were nonrecipients. Results showed that readership and satisfaction were high. Modest effects were found among mothers in the experimental group on knowledge and perception of existing community resources. Experimental mothers also tended to display greater knowledge of child development. No significant effects of the newsletter were found for fathers. The discussion centres on the potential for this type of intervention strategy to optimize existing investment in public family support programs.

{Evaluation after three years of early intervention for parental support}

This article reports the findings of a quasi-experimental evaluation of a newsletter for new parents which was adapted to the age of their children. Satisfaction with and the effectiveness of the intervention after three years of distribution were assessed. As in a previous evaluation undertaken after one year, the newsletter enjoyed widespread readership in the experimental families and among their friends and relatives. Compared to this previous evaluation, similar but stronger effects on aspects of the parental role were found, although these were confined to mothers. Mothers in the experimental group displayed greater knowledge of family support resources and had more favourable attitudes toward them than mothers in the comparison group. They also tended to display greater knowledge of child development. The discussion centres on the study's implications for research and the advisability of broadening this form of intervention.

Do nasal mast cells release histamine on stimulation with substance P in allergic rhinitis?

The effects of nasal administration of increasing doses of exogenous substance P have been studied in patients with allergic rhinitis treated with placebo or with the H1 antagonist cetirizine (10 mg twice daily for 3 days). Responses to substance P were assessed by posterior rhinomanometry (measuring nasal airway resistance) and by measure of histamine, protein and albumin production and cell recovery in nasal lavage fluids before and after challenge. Substance P induced a dose-dependent increase in nasal airway resistance which was similar after treatment with either cetirizine or placebo (maximal increase in nasal airway resistance was 4.2-fold greater than the baseline with the placebo and 4.7-fold greater than the baseline with cetirizine). No histamine release was observed. Similar increases in protein and albumin production were observed after stimulation with substance P along with the placebo (protein: from 0.35 +/- 0.11 to 3.31 +/- 0.62 mg and albumin: from 0.09 +/- 0.04 to 2.08 +/- 0.39 mg) and when combined with cetirizine treatment (proteins: from 0.42 +/- 0.09 to 3.62 +/- 0.77 and albumin: from 0.17 +/- 0.04 to 2.19 +/- 0.51 mg). After stimulation with substance P, percentages of neutrophils recovered in nasal fluids increased from 26.2 +/- 11.5 to 54.5 +/- 9.5 with the placebo and from 35.5 +/- 11.0 to 53.6 +/- 9.5 with cetirizine. Eosinophils were inconsistently found after substance P stimulation during both treatments. In conclusion, nasal response to substance P is not modified by cetirizine which suggests that the effect of substance P is not secondary to histamine release in the nose in man.

[Attention behavior of infants and modulation of maternal language]

Language spoken to infants has several peculiarities that are also found in other cultures. In this study we have examined the specific relationships between some infant's behaviours and the prosodic modulations of maternal speech in a face to face interaction. 14 mothers with their four month-old infant were observed in a laboratory setting in order to obtain a corpus of 2100 maternal words. There is a variation of maternal speech prosody that depends upon the attentional behaviours of the infant. When the infant is interacting (the gaze is directed towards the mother with a neutral or positive expression, joint gaze), the mother has a tendency to produce longer utterances with a more variable fundamental frequency than that observed when the infant is not interacting (looking elsewhere or alternating). There is also a larger occurrence of complex and bell-shaped curves during the infant's positive and joint gazes. The infant appears to be an active partner in mother-infant verbal exchange.