Cardiac surgery in the presence of chronic internal carotid artery occlusion.

The aim was to evaluate the incidence of stroke in the setting of cardiac surgery with or without hemodynamically relevant asymptomatic carotid stenosis contralateral to the occlusion. We designed a historical cohorts study, focused on patients with unilateral totally occluded internal carotid arteries who were referred for any cardiac surgery at our center. Isolated unilateral occlusions were assigned to group 1 (n = 60), and those with a contralateral stenosis grade ≥ 60% were included in group 2 (n = 51). A total of 111 patients operated in our center from 1997 to 2016 were included. Patients in group 2 had an asymptomatic contralateral internal carotid artery stenosis with a mean stenosis grade of 71 ± 20%. Simultaneous carotid endarterectomy (CEA) was performed in 22 patients from group 2. The overall mortality was 8/111 (7.2%). Carotid-associated mortality was not observed, whereas an overall stroke incidence of 8/111 (7.2%) was detected. The group-related outcome showed comparable results for mortality (group 1: 4/60 (6.7%) vs. group 2: 4/51 (7.8%); p = 1.0). Regarding stroke incidence, group 2 had a higher incidence of overall strokes (2/60 (3.3%) vs. 6/51 (11.8%); p = 0.14) with more contralateral (0/60 (0%) vs. 2/51 (3.9%); p = 0.209) and ipsilateral strokes (2/60 (3.3%) vs. 4/51 (7.8%); p = 0.411). Stroke rate peaked in patients with simultaneous carotid and cardiac surgery (n = 22; 18.2%; p = 0.048). Performing simultaneous CEA during cardiac surgery in the presence of a contralateral occlusion may promote stroke. Asymptomatic contralateral carotid stenosis is a risk factor for stroke in patients with carotid occlusion prior to cardiac surgery.

Regional and directional compliance of the healthy aorta: an ex vivo study in a porcine model.

OBJECTIVES: To gain differential knowledge about the physiological compliance and wall strength of the different regions of the aorta, including the ascending aorta, arch and descending aorta in both the circumferential and longitudinal directions, and to generate a hypothesis on the pathophysiological mechanisms that lead to Type A aortic dissection. METHODS: Fresh tissue specimens from 22 ex vivo porcine aortas were analysed on a tensile tester. Regional and directional compliance, failure stress and failure strain were recorded. RESULTS: Aortic compliance appeared as a linear function of the natural logarithm (ln) of wall stress. Compliance significantly decreased along the length of the aorta. In the ascending aorta, longitudinal compliance significantly (P = 0.003) exceeded circumferential compliance, and the outer curvature was more compliant than the inner curvature (P = 0.03). In the descending aorta, this relationship is reversed: the circumferential compliance exceeded the longitudinal compliance, and the outer aspect was more compliant (P = 0.003). The median circumferential failure stress of all aortic segments was in the range of 2000-2750 kPa, whereas the longitudinal failure stress in the ascending aorta and the arch had values of 750-1000 kPa, which were significantly lower (P < 0.05). Surprisingly, the longitudinal failure stress of the inner aspect of the descending aorta was extraordinarily high (2000 kPa). Failure strain, similar to compliance, was highest in the ascending aorta and decreased along the aorta. CONCLUSION: The aorta appears to be a complex organ with distinct regional and directional differences in compliance and wall strength that is designed to effectively absorb the kinetic energy of cardiac systole and to cushion the momentum of systolic impact. Under normotensive conditions and a preconditioned physiological morphology, the aortic wall works in the steep part of the logarithmic strain-stress function; under hypertensive conditions and pathological morphology, the wall reacts in an non-compliant manner. The high longitudinal compliance and low failure stress of the ascending aorta and subsequent pathological changes may be the main determinants of the recurrent patho-anatomy of Type A aortic dissection.

Ascending aortic elongation and the risk of dissection.

OBJECTIVES: Unlike aneurysm formation, the role of ascending aortic elongation in the pathogenesis of Type A aortic dissection (TAD) is largely unclear. We investigated the morphology of healthy, dissected and predissection aortas with a focus on ascending aortic length. METHODS: We retrospectively compared clinical and computer tomography angiography (CTA) data from TAD patients (n = 130), patients who developed a TAD in the further clinical course (preTAD, n = 16) and healthy control patients who received a CTA for non-aortic emergencies (n = 165). The length of the ascending aorta was defined as the distance between the sinotubular junction (STJ) and the brachiocephalic trunk (BCT) at the central line, the outer and inner curvature as well as the direct distance in the frontal and sagittal planes. Additionally, the aortic diameters were analysed. RESULTS: In the healthy controls, we found a positive correlation of age with the aortic diameter (r = 0.57) and aortic length (r = 0.42). The correlation of the respective parameters with the body size was negligible (r < 0.2). The median ascending aortic diameter at the height of the pulmonary artery in TAD (50 mm) was significantly (P < 0.001) larger compared with the respective diameter of the healthy aortas (34 mm). The diameter of the preTAD aortas (40 mm) was also significantly larger compared with the healthy controls. These proportions were similar in all the aortic diameters. The midline length of the healthy ascending aortas was 71 mm. In the preTAD and TAD aortas, the same values were 81 mm and 92 mm, respectively (both P < 0.001). We evaluated the linear distance between the STJ and the BCT in the frontal plane as an easy-to-measure parameter of aortic length. In the TAD aortas (108 mm) and preTAD aortas (97 mm), this distance was significantly longer compared with the healthy aortas (84 mm). CONCLUSIONS: Aortic diameter might not be an optimal parameter to predict dissection. Most aortas dissect at diameters below 55 mm. Both the TAD and preTAD aortas were elongated compared with the healthy controls. Thus, aortic elongation may play a role in the pathogenesis of and may be a risk factor for TAD.

Identification of Predictive Early Biomarkers for Sterile-SIRS after Cardiovascular Surgery.

Systemic inflammatory response syndrome (SIRS) is a common complication after cardiovascular surgery that in severe cases can lead to multiple organ dysfunction syndrome and even death. We therefore set out to identify reliable early biomarkers for SIRS in a prospective small patient study for timely intervention. 21 Patients scheduled for planned cardiovascular surgery were recruited in the study, monitored for signs of SIRS and blood samples were taken to investigate biomarkers at pre-assigned time points: day of admission, start of surgery, end of surgery, days 1, 2, 3, 5 and 8 post surgery. Stored plasma and cryopreserved blood samples were analyzed for cytokine expression (IL1ß, IL2, IL6, IL8, IL10, TNFα, IFNγ), other pro-inflammatory markers (sCD163, sTREM-1, ESM-1) and response to endotoxin. Acute phase proteins CRP, PCT and pro-inflammatory cytokines IL6 and IL8 were significantly increased (p<0.001) at the end of surgery in all patients but could not distinguish between groups. Normalization of samples revealed significant increases in IL1ß changes (p<0.05) and decreased responses to endotoxin (p<0.01) in the SIRS group at the end of surgery. Soluble TREM-1 plasma concentrations were significantly increased in patients with SIRS (p<0.01). This small scale patient study could show that common sepsis markers PCT, CRP, IL6 and TNFα had low predictive value for early diagnosis of SIRS after cardiovascular surgery. A combination of normalized IL1ß plasma levels, responses to endotoxin and soluble TREM-1 plasma concentrations at the end of surgery are predictive markers of SIRS development in this small scale study and could act as an indicator for starting early therapeutic interventions.

Elastic properties of the young aorta: ex vivo perfusion experiments in a porcine model.

OBJECTIVES: To investigate the regional and directional compliance/distensibility of the healthy aorta. METHODS: Complete fresh porcine aortas (n = 11) were perfused ex vivo under defined haemodynamic parameters using a custom-made pulse duplicator. Both circumferential and longitudinal compliance were measured optically. RESULTS: The pulse duplicator was able to perfuse the entire aorta with arbitrary haemodynamic parameters, generating a physiological pulse curve. Aortic compliance is pressure dependent, as we observed a linear relationship between pressure and distension in the range of 5-200 mmHg; however, above 200 mmHg, the porcine aorta behaved in an inelastic manner. Circumferential compliance was highest in the ascending aorta (24%/100 mmHg) but significantly (P < 0.05) decreased in both the arch (18%/100 mmHg) and the descending aorta (15%/100 mmHg). Longitudinal compliance was highest in the ascending aorta and clearly exceeded circumferential compliance. Compliance was significantly (P < 0.05) higher in the outer curvatures of the ascending aorta and the aortic arch compared with the compliance of the inner curvature at these locations (30%/100 vs 23%/100 mmHg in the ascending aorta and 20%/100 vs 9%/100 mmHg in the arch, respectively). CONCLUSIONS: Longitudinal compliance of the ascending aorta, particularly the outer curvature, is predominantly responsible for the 'Windkessel effect'. Pathological changes such as elongation and pronounced angulation of the ascending aorta increase stress on the outer curvature and may be important factors in the development of aortic dissection.