Aprikalim a potassium adenosine triphosphate channel opener reduces neurologic injury in a rabbit model of spinal cord ischemia.

BACKGROUND: Potassium adenosine triphosphate (KATP) channel openers have been involved in the enhancement of ischemic tolerance in various tissues. The purpose of the present study is to evaluate the effects of aprikalim, a specific KATP channel opener, on spinal cord ischemic injury. METHODS: Fifty-four rabbits were randomly assigned to three groups: group 1 (n = 18, sham operation), group 2 (n = 18, 30 min of normothermic aortic cross-clamping) and group 3 (n = 18, aprikalim 100 µg/kg was administered 15 min before 30 min of normothermic aortic cross-clamping). Neurologic evaluation was performed according to the modified Tarlov scale. Six animals from each group were sacrificed at 24, 48 and 168 h postoperatively. The lumbar spinal cords were harvested and examined histologically. The motor neurons were counted and the histologic lesions were scored (0-3, 3: normal). RESULTS: Group 3 (aprikalim group) had better Tarlov scores compared to group 2 at all-time points (P < 0.025). The histologic changes were proportional to the Tarlov scores and group 3 had better functional outcome as compared to group 2 at 168 h (number of neurons: 21.2 ± 4.9 vs. 8.0 ± 2.7, P < 0.001 and histologic score: 1.67 ± 1.03 vs. 0.50 ± 0.55, P = 0.03). Although aprikalim exhibited improved effect on clinical and histologic neurologic outcome when compared to normothermic spinal cord ischemia, animals in group 3 had worse Tarlov score, reduced number of motor neurons and worse histologic score when compared to group 1 (sham operation) at 168 h (P = 0.003, P = 0.001 and P = 0.019 respectively). CONCLUSION: Aprikalim reduces the severity of spinal cord ischemic injury in a rabbit model of spinal cord ischemia.

Treatment with simvastatin inhibits the formation of abdominal aortic aneurysms in rabbits.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a common and lethal disease. AAAs are associated with atherosclerosis, chronic inflammation, and extracellular matrix degradation. The aim of this study was to determine whether treatment with simvastatin can influence the development of experimental aortic aneurysms in a rabbit model. MATERIALS AND METHODS: A total of 76 rabbits were randomized in four groups: in group I (n = 12), where the abdominal aortas were exposed to 0.9% NaCl, and in group II (n = 24), group III (n = 24) and group IV (n = 18), where the aortas were exposed to CaCl2 0.5 mol/L for 15 minutes after laparotomy. Group III received 2 mg/kg simvastatin daily starting 7 days before laparotomy, and in group IV, the daily treatment with simvastatin started 7 days after laparotomy. Animals were sacrificed at intervals of first, second, third, and fourth week to obtain measurements of aortic diameter and histological examination. Moreover, immunohistochemistry was used in order to examine the relative distribution of matrix metalloproteinases (MMPs) 2 and 9 (MMP-2 and MMP-9, respectively) and tissue inhibitor 1 of MMPs within the aortic aneurysms. RESULTS: The increase of aortic diameter in animals of group I ranged from 4.6% to 7.6%; in group II, from 41% to 85% (P < 0.001 vs. group I); in group III, from 9% to 18% (group II vs. group III, P < 0.001); and in group IV; from 36% to 38%. Moreover, aortic specimens of group II presented a statistically significant increase in MMP-2 and MMP-9 immunoexpression compared with other groups (I, III, IV) (P < 0.05 for all comparisons), with the exception of animals of group IV at the end of second week. Immunoreactivity of tissue inhibitor 1 of MMPs was not statistically different among groups II, III, and IV. CONCLUSIONS: Simvastatin may prove clinically significant in suppressing the development and expansion of AAAs and, thereby, in reducing the risk of rupture and the need for repair.

Surgical thoracic sympathectomy induces structural and biomechanical remodeling of the thoracic aorta in a porcine model.

BACKGROUND: Sympathetic innervation exerts marked effects on vascular smooth muscle cells, including a short-term homeostatic (vasoconstrictor) and a direct trophic action promoting differentiation. However, the role of sympathetic nervous system in long-term structural and functional modulation of the aortic wall is yet undefined. METHODS: Six Landrace pigs underwent bilateral thoracic sympathectomy from the stellate to T8 ganglion, whereas 10 pigs underwent sham operation. Animals were sacrificed 3 mo postoperatively. Histometrical examination was performed on specimens from the thoracic (TA) and abdominal aorta (AA) utilizing an image-processing system. A uniaxial tensile tester was utilized for biomechanical evaluation; parameters of extensibility, strength, and stiffness of aortic tissue were calculated. RESULTS: Structural aortic remodeling of sympathectomized animals was observed, including increased inner aortic diameter in TA (15.3 ± 0.4 versus 10.4 ± 0.2 mm, P < 0.001) and AA (6.7 ± 0.3 versus 5.3 ± 0.2 mm, P = 0.002), and increased wall thickness in TA (2.0 ± 0.1 versus 1.6 ± 0.1 mm, P < 0.001) but not AA. Microscopic image analysis revealed increased elastin (TA: 50.1 ± 1.1 versus 29.7% ± 0.6%, P < 0.001; AA: 20.4 ± 2.1 versus 16.3% ± 0.6%, P = 0.03) and collagen density (only in TA: 22.0 ± 0.9 versus 15.4% ± 0.5%, P < 0.001), and decreased smooth muscle density (TA: 27.6 ± 1.3 versus 54.9% ± 0.7%, P < 0.001; AA: 57.2 ± 1.5 versus 63.4% ± 0.8%, P < 0.001). Sophisticated biomechanical analysis demonstrated that following sympathectomy, TA was equally extensible but manifested augmented strength (1344 ± 73 versus 1071 ± 52 kPa, P = 0.004) and stiffness (6738 ± 478 versus 5026 ± 273 kPa, P = 0.003), in accordance with extracellular matrix protein accumulation in that region. Differences in the AA were non-significant. CONCLUSIONS: Chronic thoracic sympathetic denervation causes significant structural and biomechanical remodeling of the thoracic aorta. Possible clinical implications for patients undergoing thoracic sympathectomy or chronically treated with sympathetic blockers require further investigation.

Postoperative and long-term outcome of patients with chronic obstructive pulmonary disease undergoing coronary artery bypass grafting.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) has been conventionally associated with increased operative mortality and morbidity after coronary artery bypass grafting. Some studies, however, challenge this association. Moreover, the effect of COPD on long-term survival after coronary artery bypass grafting has not been adequately assessed. Thus, in this clinical setting, both early and late outcome require further examination. METHODS: We studied 3,760 consecutive patients who underwent isolated coronary artery bypass grafting between 1992 and 2002. The propensity for COPD was determined by logistic regression analysis, and each patient with COPD was matched with 3 patients without COPD. Matched groups were compared for early outcome and long-term survival (mean follow-up, 7.6 years). Long-term survival data were obtained from the National Death Index. RESULTS: There were 550 patients (14.6%) with COPD. Multivariate analysis showed that patients with COPD were older and sicker. However, propensity-matched groups did not differ in terms of hospital mortality or major morbidity, although COPD was associated with a slightly longer hospital stay. In contrast, COPD patients had increased long-term mortality, with a hazard ratio of 1.28 (95% confidence intervals, 1.11 to 1.47; p=0.001). Freedom from all-cause mortality at 7 years after CABG was 65% and 72% in matched patients with and without COPD, respectively (p=0.008). In patients with COPD, the hazard estimate was consistently increased up to 9 years postoperatively. CONCLUSIONS: Chronic obstructive pulmonary disease, although not an independent predictor of increased early mortality and morbidity in this series, is a continuing detrimental risk factor for long-term survival.

Differential expression of collagen type V and XI alpha-1 in human ascending thoracic aortic aneurysms.

BACKGROUND: The molecular mechanisms leading to ascending thoracic aortic aneurysms (ATAAs) remain unknown. We hypothesized that alterations in expression levels of specific fibrillar collagens occur during the aneurysmal process. METHODS: Surgical samples from ascending aortas from patients with degenerative ATAAs were subdivided by aneurysm diameter: small, 5 to 6 cm; medium, 6 to 7 cm; and large, greater than 7 cm; and compared with nonaneurysmal aortas (mean diameter, 2.3 cm). RESULTS: Histology, immunofluorescence, and electron microscopy demonstrated greater disorganization of extracellular matrix constituents in ATAAs as compared with control with an increase in collagen alpha1(XI) within regions of cystic medial degenerative lesions. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) showed collagens type V and alpha1(XI) were significantly and linearly increased in ATAAs as compared with control (p < 0.001). There was no change in the messenger ribonucleic acid (mRNA) expression levels of collagens type I and III. Western blot analysis showed collagens type I and III were significantly decreased and collagens alpha1(XI) and V were significantly increased and were linearly correlated with the size of the aneurysm (p < 0.001 for both). CONCLUSIONS: These results demonstrate that increased collagen alpha1(XI) and collagen V mRNA and protein levels are linearly correlated with the size of the aneurysm and provide a potential mechanism for the generation and progression of aneurysmal enlargement.

The impact of left ventricular hypertrophy on early and long-term survival after coronary artery bypass grafting.

BACKGROUND: Left ventricular hypertrophy (LVH) can itself contribute to increased rates of cardiovascular events. We sought to determine the impact of LVH on in-hospital and long-term mortality after coronary artery bypass grafting (CABG). METHODS: Between 1992 and 2003, 4140 consecutive patients underwent CABG. Long-term survival data (mean follow-up 7.0 years) were obtained from the National Death Index. The impact of LVH on in-hospital mortality was determined by multivariate logistic regression analysis. Patients with and without LVH were compared by Cox proportional hazard models and risk-adjusted Kaplan-Meier curves. RESULTS: There were 977 patients (23.6%) with LVH. Their mean EuroSCORE was 7.4 +/- 3.4 and there were 40 in-hospital deaths (4.1%) in this group. Multivariate logistic regression showed that patients with LVH had less elective operations, higher Canadian Cardiovascular Society Functional Class, more previous myocardial infarctions and higher percentages of 3-vessel disease, hypertension, current congestive heart failure, malignant ventricular arrhythmias, chronic obstructive pulmonary disease, calcified aorta, low ejection fraction, intravenous nitroglycerine, previous percutaneous coronary interventions and smoking. After adjustment for all available pre, intra and postoperative variables LVH was not an independent predictor for in-hospital mortality (OR 1.04, 95% CIs 0.60-1.81, P = 0.891). Risk-adjusted Kaplan-Meier survival curves showed decreased long-term survival in patients with LVH after the first 3 years (HR 1.24, 95% CIs 1.06-1.44, P = 0.006). CONCLUSIONS: Patients with LVH showed similar in-hospital mortality when compared with patients without LVH. However, LVH was a detrimental risk factor for late mortality, especially after the third postoperative year. These data suggest the need for a more frequent long-term follow-up among patients with LVH undergoing CABG.

Independent predictors for early and long-term mortality after heart valve surgery.

BACKGROUND AND AIM OF THE STUDY: Patients with heart valve surgery may have a periprocedural mortality extending up to one year after surgery. The study aim was to determine independent predictors for in-hospital and long-term mortality after heart valve surgery. METHODS: A total of 1,376 consecutive patients who underwent isolated or combined heart valve surgery at a single institution was studied. Multivariate logistic regression analysis was used to determine independent predictors for in-hospital mortality. Long-term survival data (mean follow up 5.6 years) were obtained from the National Death Index. Multivariate Cox regression analysis was used to determine independent predictors for long-term mortality. All available preoperative, intraoperative and postoperative risk factors were included in these analyses. RESULTS: The mean EuroSCORE was 6.2 +/- 3.7. There were 86 (6.3%) in-hospital and 550 (40.0%) late deaths. Eleven independent predictors were determined for in-hospital mortality, and 13 for long-term mortality. There were six common independent predictors (preoperative dialysis, total bypass time, intraoperative stroke, postoperative sepsis and/or endocarditis, renal and respiratory failure). Unique independent predictors for in-hospital mortality included intra-aortic balloon pump, preoperative endocarditis, intravenous use of nitroglycerine, bleeding requiring reoperation and gastrointestinal complications. The model for in-hospital mortality showed acceptable calibration (Lemeshow-Hosmer, p = 0.629) and excellent discriminatory ability (C statistic 0.88). Unique independent predictors for long-term mortality included age, ejection fraction, stroke prior to surgery, hemodynamic instability, chronic obstructive pulmonary disease and deep sternal wound infection. CONCLUSION: Independent predictors were determined for early and long-term mortality after heart valve surgery. The prevention of postoperative complications may be a key element for increased early and long-term survival in these patients.

Impact of early and delayed stroke on in-hospital and long-term mortality after isolated coronary artery bypass grafting.

Stroke after coronary artery bypass grafting (CABG) is an infrequent, yet devastating complication with increased morbidity and mortality. We sought to determine risk factors for early (intraoperatively to 24 hours) and delayed (>24 hours to discharge) stroke and to identify their impact on long-term mortality after CABG. We studied 4,140 consecutive patients who underwent isolated CABG from 1992 to 2003. Long-term survival data (mean follow-up 7.4 years) were obtained from the National Death Index. Independent predictors for stroke and in-hospital mortality were determined by multivariate logistic regression analysis including all available preoperative, intraoperative, and postoperative risk factors. Independent predictors for long-term mortality were determined by multivariate Cox regression analysis. One hundred two patients (2.5%) developed early stroke and 36 patients (0.9%) delayed stroke. Independent predictors for early stroke were age, recent myocardial infarction, smoking, femoral vascular disease, body mass index, reoperation for bleeding, postoperative sepsis and/or endocarditis, and respiratory failure, whereas those for delayed stroke were female gender, white race, preoperative renal failure, respiratory failure, and postoperative renal failure. Early stroke was an independent predictor for in-hospital (odds ratio 3.49, 95% confidence interval [CI] 1.56 to 7.80, p = 0.002) and long-term (hazard ratio 1.70, 95% CI 1.30 to 2.21, p <0.001) mortalities. Delayed stroke was not an independent predictor for in-hospital (odds ratio 0.90, 95% CI 0.23 to 3.51, p = 0.878) or long-term (hazard ratio 0.66, 95% CI 0.38 to 1.17, p = 0.156) mortality. In conclusion, risk factors for early in-hospital stroke differ from those of delayed in-hospital stroke after CABG. Early stroke is an independent predictor for in-hospital and long-term mortalities, suggesting the need for a more frequent follow-up and appropriate pharmacologic therapy after discharge.

Effect of N-acetyl-L-cysteine on lung ischaemia reperfusion injury in a porcine experimental model.

BACKGROUND: The purpose of the present study was to investigate the effect of N-acetyl-L-cysteine on lung ischaemia reperfusion injury. METHODS: Nineteen pigs were used. Group I (n = 5) underwent sham operation, group II (n = 7) 90-min left-lung ischaemia followed by 180-min reperfusion. In group III (n = 7) N-acetyl-l-cysteine was given (160 mg/kg) during ischaemia into the pulmonary artery. Lung-functional and haemodynamic parameters were measured; serum and lung tissue samples were obtained and analysed for interleukin-10 and tumour necrosis factor-alpha. At the end of the reperfusion bronchoalveolar lavage was carried out from the ipsilateral lung and analysis for total protein, phospholipase-A(2) and platelet-activating factor acetylhydrolase was carried out. Histological specimens were graded (0-3) for alveolar oedema, interstitial thickening and leucocyte infiltration. Statistical analysis was by means of one-way analysis of variance and Kruskal-Wallis test. RESULTS: There were no differences in haemodynamic parameters, serum and tissue interleukin-10 and tumour necrosis factor-alpha. Pulmonary compliance was decreased in groups II and III (P = 0.002 and P = 0.001, respectively) during ischaemia and reperfusion. Pulmonary vascular resistance was increased in group II (P = 0.051) during reperfusion. In group III total protein and platelet-activating factor acetylhydrolase were increased (P = 0.004 and P = 0.006, respectively) and phospholipase-A(2) was reduced (P = 0.002), indicating an indirect surfactant-protective effect. Interstitial thickening was excessive in group II (P = 0.001); however, alveolar oedema was reduced (P = 0.002) when compared with group III. CONCLUSION: N-acetyl-L-cysteine when administered directly in the pulmonary artery showed no significant change in haemodynamic and functional lung parameters during ischaemia reperfusion; it does, however, have an indirect surfactant-protective effect.

Thoracoscore predicts midterm mortality in patients undergoing thoracic surgery.

OBJECTIVE: Thoracoscore is the first multivariate model for the prediction of in-hospital mortality after general thoracic surgery. We aimed to evaluate the performance of Thoracoscore in predicting in-hospital and midterm all-cause mortality. METHODS: We retrospectively evaluated 1675 patients who underwent thoracic surgery (lung resections [n = 626], mediastinum [n = 535], pleura and pericardium [n = 268], esophagus [n = 88], chest wall [n = 90], trachea [n = 45], and other procedures [n = 23]) from October 2002 to March 2006 at a single institution. Midterm survival data (mean follow-up 25 +/- 16 months) were obtained from the National Death Index. Kaplan-Meier survival plots of the quartiles of Thoracoscore were constructed and compared with the log-rank test with adjustment for trend. RESULTS: Starting from the lower-risk to the higher-risk quartile, the in-hospital mortality rates were 0% (0/418), 1% (4/415), 2.5% (11/435), and 9.6% (54/407). Thoracoscore was a strong independent predictor for in-hospital mortality (odds ratio 1.20, 95% confidence intervals 1.15-.25; P < .001). The 2-year survivals of the Thoracoscore quartiles were 98.7% +/- 0.6%, 87.0% +/- 1.8%, 73.8% +/- 2.3%, and 54.8% +/- 2.7%, respectively (P < .0001). Thoracoscore was a strong independent predictor for midterm mortality (hazard ratio 1.12, 95% confidence intervals 1.11-1.14; P < .001). CONCLUSION: Thoracoscore is a good and useful clinical tool for preoperative prediction of in-hospital and midterm mortality among patients undergoing general thoracic surgery.