Influence of mild heat and restrictive external support on functional changes in vein grafts implanted into arterial circulation. Experimental study

Introduction. Vein grafts placed in the arterial circulation undergo a set of morphological and functional changes. The aim was to investigate the effects of external mild heat combined with internal cooling and external restrictive support on vascular reactivity of the venous grafts implanted into arterial system. Material and methods. Reversed external jugular vein interposition grafting of the carotid artery on the mongrel dogs (n = 18) was performed. The experimental animals were split into three groups: H (n = 6) - grafts were exposed to mild heat and an external sleeve was placed around, S (n = 6) - grafts only with the sleeve and C (n = 6) - control group. The grafts were explanted after 3 months. The rings from all the explanted grafts as well as from jugular veins before implantation were taken and tension study was performed. Contractions to norepinephrine (NE), phenylephrine (Phe), 5-hydroxytryptamine (5-HT) and relaxation to acetylcholine (Ach), calcium ionophore A23187 (A23187) and sodium nitroprusside (SN) were assessed. Results. After pre-treatment with mild heat reaction to the maximal concentrations of NE (37.8 &plusmn; 1.9 g/mm2 before vs. l2.0 &plusmn; 1.6 g/mm2 after), Phe (20.2 &plusmn; 1.6 g/mm2 vs. 2.0 &plusmn; 0.4 g/mm2) were markedly (p < 0.001) diminished. Vein grafts before implantation were insensitive to 5-HT. Only endothelium-independent relaxation to SN was preserved in the grafts after mild heat employment, whereas Ach, A23187 did not produce any endothelium-mediated reaction. Three months after implantation markedly lower contractile responses to maximal doses of NE (1.4 &plusmn; 0.2 g/mm2, 2.1 &plusmn; 0.3 g/mm2 and 15.4 &plusmn; 1.6 g/mm2 for H, S and C respectively), and Phe (0.4 &plusmn; 0.2 g/mm2, 1.3 &plusmn; 0.2 g/mm2 and 12.3 &plusmn; 1.2 g/mm2 for H, S and C respectively) were noted. The maximal examined dose of 5-HT provoked 66.2% of the maximal reaction to NE in group H, 66.5% in group S and 53.2% in group C. The grafts in group H and S were insensitive to endothelium-dependent relaxants, but in C the maximal responses to A23187 were significantly weaker (p < 0.05) than before implantation (40.7 &plusmn; 3.8% vs. 67.4 &plusmn; 2.3%). SN-induced endothelium-independent relaxation was observed in all groups. Conclusion. Mild heat of the venous grafts functionally destroys endothelium and significantly impairs smooth muscle cells' function. Employment of mild heat combined with external support may produce venous conduits less sensitive to vasoactive chemicals including also mitogens involved in neointima formation.Introduction. Vein grafts placed in the arterial circulation undergo a set of morphological and functional changes. The aim was to investigate the effects of external mild heat combined with internal cooling and external restrictive support on vascular reactivity of the venous grafts implanted into arterial system. Material and methods. Reversed external jugular vein interposition grafting of the carotid artery on the mongrel dogs (n = 18) was performed. The experimental animals were split into three groups: H (n = 6) - grafts were exposed to mild heat and an external sleeve was placed around, S (n = 6) - grafts only with the sleeve and C (n = 6) - control group. The grafts were explanted after 3 months. The rings from all the explanted grafts as well as from jugular veins before implantation were taken and tension study was performed. Contractions to norepinephrine (NE), phenylephrine (Phe), 5-hydroxytryptamine (5-HT) and relaxation to acetylcholine (Ach), calcium ionophore A23187 (A23187) and sodium nitroprusside (SN) were assessed. Results. After pre-treatment with mild heat reaction to the maximal concentrations of NE (37.8 &plusmn; 1.9 g/mm2 before vs. l2.0 &plusmn; 1.6 g/mm2 after), Phe (20.2 &plusmn; 1.6 g/mm2 vs. 2.0 &plusmn; 0.4 g/mm2) were markedly (p < 0.001) diminished. Vein grafts before implantation were insensitive to 5-HT. Only endothelium-independent relaxation to SN was preserved in the grafts after mild heat employment, whereas Ach, A23187 did not produce any endothelium-mediated reaction. Three months after implantation markedly lower contractile responses to maximal doses of NE (1.4 &plusmn; 0.2 g/mm2, 2.1 &plusmn; 0.3 g/mm2 and 15.4 &plusmn; 1.6 g/mm2 for H, S and C respectively), and Phe (0.4 &plusmn; 0.2 g/mm2, 1.3 &plusmn; 0.2 g/mm2 and 12.3 &plusmn; 1.2 g/mm2 for H, S and C respectively) were noted. The maximal examined dose of 5-HT provoked 66.2% of the maximal reaction to NE in group H, 66.5% in group S and 53.2% in group C. The grafts in group H and S were insensitive to endothelium-dependent relaxants, but in C the maximal responses to A23187 were significantly weaker (p < 0.05) than before implantation (40.7 &plusmn; 3.8% vs. 67.4 &plusmn; 2.3%). SN-induced endothelium-independent relaxation was observed in all groups. Conclusion. Mild heat of the venous grafts functionally destroys endothelium and significantly impairs smooth muscle cells' function. Employment of mild heat combined with external support may produce venous conduits less sensitive to vasoactive chemicals including also mitogens involved in neointima formation

Does mild heat combined with external stenting prevent from intimal hyperplasia and medial thickening in the venous grafts? Experimental study

Introduction. Intimal hyperplasia and medial thickening of the venous grafts used in coronary artery bypass grafting (CABG) often leads to wall thickening and ultimately to conduit occlusion. The purpose was to investigate the effects of mild heat (85°C) followed by utilization of restrictive sleeve on histological changes of the venous grafts implanted into an arterial system. Material and methods. Reversed external jugular vein interposition grafting of the carotid artery on the mongrel dogs (n = 18) was performed. The experimental animals were split into three groups: H (n = 6) - grafts were exposed to mild heat and an external sleeve was placed around, S (n = 6) - grafts only with the sleeve and C (n = 6) - control group. The grafts were explanted after 3 months. Prior to explantation the grafts&#8217; patency was checked using flowmeter. Afterwards harvested veins were examined in light (LM), scanning (SEM) and transmission electron microscope (TEM). Cross-sectional intima (IA), media (MA) and relative intima area (RIA) for all grafts were calculated. Tissue samples from all grafts before implantation (harvested veins and veins after exposition to mild heat) were also examined. Results. Mild heat destroyed endothelial cells (ECs) and, to a lesser degree, basement membrane but did not influence IA, MA and RIA values. Medial smooth muscle cells (SMCs) located closer to the adventitia were affected by heat pretreatment. After 3 months all grafts were patent. Intimal hyperplasia was observed in group S and C, but not in H. Intimal area was markedly higher (p < 0.05) in group S (1.97 &plusmn; 0.57 mm2) and C (1.51 &plusmn; 0.77 mm2) than in H (0.38 &plusmn; 0.08 mm2). Scanning scans 3 months after implantation showed the luminal surface of all grafts was mostly covered by ECs. Smoth muscle cells were present in the intima of all grafts in group C and S, not in H. Some of them were active synthetic type SMCs with many mitochondria and well developed Golgi apparatus (TEM). The media was atrophic in group H and S, where collagen bundles were dissociated, the collagen fibers disrupted and in random orientation in the matrix. Media area was significantly higher (p < 0.05) in group C (2.64 &plusmn; 0.32 mm2) than in S (1.71 &plusmn; 0.45 mm2) and H (1.74 &plusmn; 0.48 mm2). Conclusion. Mild heat pre-treatment and external sleeving may mitigate the formation of intimal hyperplasia and reduce medial thickening after implantation in the arterial circulation.Introduction. Intimal hyperplasia and medial thickening of the venous grafts used in coronary artery bypass grafting (CABG) often leads to wall thickening and ultimately to conduit occlusion. The purpose was to investigate the effects of mild heat (85°C) followed by utilization of restrictive sleeve on histological changes of the venous grafts implanted into an arterial system. Material and methods. Reversed external jugular vein interposition grafting of the carotid artery on the mongrel dogs (n = 18) was performed. The experimental animals were split into three groups: H (n = 6) - grafts were exposed to mild heat and an external sleeve was placed around, S (n = 6) - grafts only with the sleeve and C (n = 6) - control group. The grafts were explanted after 3 months. Prior to explantation the grafts&#8217; patency was checked using flowmeter. Afterwards harvested veins were examined in light (LM), scanning (SEM) and transmission electron microscope (TEM). Cross-sectional intima (IA), media (MA) and relative intima area (RIA) for all grafts were calculated. Tissue samples from all grafts before implantation (harvested veins and veins after exposition to mild heat) were also examined. Results. Mild heat destroyed endothelial cells (ECs) and, to a lesser degree, basement membrane but did not influence IA, MA and RIA values. Medial smooth muscle cells (SMCs) located closer to the adventitia were affected by heat pretreatment. After 3 months all grafts were patent. Intimal hyperplasia was observed in group S and C, but not in H. Intimal area was markedly higher (p < 0.05) in group S (1.97 &plusmn; 0.57 mm2) and C (1.51 &plusmn; 0.77 mm2) than in H (0.38 &plusmn; 0.08 mm2). Scanning scans 3 months after implantation showed the luminal surface of all grafts was mostly covered by ECs. Smoth muscle cells were present in the intima of all grafts in group C and S, not in H. Some of them were active synthetic type SMCs with many mitochondria and well developed Golgi apparatus (TEM). The media was atrophic in group H and S, where collagen bundles were dissociated, the collagen fibers disrupted and in random orientation in the matrix. Media area was significantly higher (p < 0.05) in group C (2.64 &plusmn; 0.32 mm2) than in S (1.71 &plusmn; 0.45 mm2) and H (1.74 &plusmn; 0.48 mm2). Conclusion. Mild heat pre-treatment and external sleeving may mitigate the formation of intimal hyperplasia and reduce medial thickening after implantation in the arterial circulation

Assessment of Chest Compression Quality — a systematic review

INTRODUCTION: High-quality chest compression (CC) is a crucial factor that determines the survival of cardiac arrest patients. Adequate quality should be featured by appropriate compression rate and depth, and full chest recoil after each compression. The ranges are strictly determined in Resuscitation Guidelines. All these parameters are interdependent. Currently, there is a need to find or develop a universal index that will enable the definition and determination of the overall quality of CCs.  MATERIAL AND METHODS: A systematic review of the MEDLINE, EMBASE, COCHRANE, and GOOGLE SCHOLAR databases was performed. The authors aimed to find papers in which the quality of CC was assessed. The extracted information included measurement of the CC quality in a direct and objective manner — by analysing the depth, rate, and recoil of CC, position of the hands, duty cycle, and indirectly by evaluating chest compression fraction (CCF). Papers describing the quality of CC based on a combination of various components of the CC quality were selected for analysis.  RESULTS: In total 1604 publications were obtained. Among them, 21 articles satisfied the search criteria. In most of the papers, it was suggested that compressions should have been considered as correct when they met simultaneously all quality criteria. Only three papers presented any mathematical formula that could have been used for further comparisons.  CONCLUSIONS: Although many proposals have been developed, no single, universal, and commonly accepted indicator of resuscitation quality has been so far designed and subsequently applied. Further work on this subject is warranted and strongly recommended.

Analysis of the quality of chest compressions during resuscitation in an understaffed team — randomised crossover manikin study

INTRODUCTION: According to the chain of survival, chest compressions (CCs) are crucial in every cardiac arrest patient. It is very challenging to provide high-quality resuscitation in a two-paramedic team. The task of an automatic chest compression device (ACCD) is to relieve the rescuer and improve the quality of CCs. Its influence on the quality of the whole resuscitation as well as the survival of patients is still subject to discussion worldwide. This study aimed to assess the quality of CCs during resuscitation in a two-paramedic team using ACCD.  MATERIAL AND METHODS: This research was designed as a prospective, randomised, cross-over, high-fidelity simulation study. Fifty-two double paramedic teams took part in the research. The role of the participants was to conduct full advanced resuscitation in a human patient’s simulator. Each team provided resuscitation twice. Once with an ACCD and once using manual compressions. Chest compression quality parameters, as well as chest compression fraction (CCF), were measured.  RESULTS : Statistically significant differences were found between manual and automated compressions in: mean depth (48 ± 4 mm vs. 56 ± 3 mm, p &lt; 0.0001), mean rate (117 ± 9 mm vs. 103 ± 1 mm, p &lt; 0.0001), percentage of CC with correct depth (46 ± 25 vs. 87 ± 13, p &lt; 0.0001), rate (72 ± 22 vs. 96 ± 4, p &lt; 0.0001), and recoil (55 ± 23 vs. 89 ± 13, p &lt; 0.0001). CCF was also higher when the ACCD was used (74 ± 7% vs. 83 ± 2%, p &lt; 0.0001).  CONCLUSIONS: The use of an ACCD increases the quality of compressions by improving CCF, chest recoil, and the percentage of compressions performed with adherence to guidelines.

Asymptomatic thoracic stentgraft collapse treated conservatively

W pracy przedstawiono przypadek 58-letniego mężczyzny przyjętego do szpitala z ostrym rozwarstwieniem aorty (typ B według klasyfikacji Stanforda), który zaopatrzono stentgraftem piersiowym Cook Zenith. Trzy miesiące po zabiegu, podczas pierwszej rutynowej kontroli, przeprowadzono badanie angiografii tomografii komputerowej (CTA), w którym wykazano proksymalne zamknięcie się stentgraftu. Próba ponownego otwarcia protezy okazała się nieskuteczna. Pacjenta poinformowano o potrzebie przeprowadzenia zabiegu kardiochirurgicznego oraz o ewentualnym związanym z nim ryzyku. Chory odmówił poddania się operacji. Do tej pory, 3 lata po zdiagnozowaniu zamkniętego stentgraftu, u pacjenta nie występują żadne objawy. W systematycznie przeprowadzanych co 6&#8211;9 miesięcy kontrolnych badaniach CTA nie stwierdza się dalszego poszerzania aorty piersiowej. Acta Angiol 2010; 16, 3: 138&#8211;143We describe a case of 58-year-old male with complicated acute type B aortic dissection that was treated with a Cook Zenith thoracic stentgraft. Three months after the procedure, the first routine follow-up computed tomography angiography (CTA) revealed proximal collapse of the stentgraft. An attempt to reopen the endograft from the distal part in a retrograde manner followed by second device implantation failed. After the patient was informed about the need for an open surgical procedure and its related risk, he refused to be operated upon. Up to now, 3 years after diagnosis of stentgraft collapse, he has remained asymptomatic and in serial follow-up CTA scans carried out every 6 to 9 months no further thoracic aortic dilatation has been noted. Acta Angiol 2010; 16, 3: 138&#8211;14