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.

The effects of hypothyroidism on the mechanical properties and histomorphological structure of the thoracic aorta.

This experimental study investigates the effects of hypothyroidism on the descending thoracic aorta. Hypothyroidism was induced in 20 male Wistar rats by administering 0.05% of 6-n propyl 2-thiouracil (PTU) in their drinking water for 8 weeks. Euthyroid rats were used as controls. Animals were sacrificed and longitudinal strips of the descending aorta were subjected to various preselected levels of stress in a uniaxial tensile-testing device. Analysis of stress-strain, elastic modulus-strain curves disclosed significant differences between groups, indicative of stiffer aortas in hypothyroid animals at the upper physiologic and higher levels of pressure. Remodeling of the aortic wall of hypothyroid animals revealed significant histological changes. The thoracic aorta of hypothyroid rats compared with that of euthyroid ones became stiffer at high strains, including the upper physiologic range, loosing part of its distensibility. Hypothyroidism was also associated with diameter enlargement and substantial lengthening of the aorta.

Hypothyroidism and the aorta. evidence of increased oxidative DNA damage to the aorta of hypothyroid rats.

BACKGROUND: Although it has been suggested that the hypometabolic state is associated with a decrease in oxidative stress, literature data are controversial, revealing an individuality of oxidant status in relation to tissue properties and responsiveness. Hypothyroidism has profound direct and indirect actions on the vascular system, inducing characteristic hemodynamic changes while the aorta represents an important determinant of vascular performance. This study aims to examine the oxidant status on the aorta in chronic experimental hypothyroidism. MATERIALS AND METHODS: Chronic hypothyroidism was successfully induced in 20 male Wistar rats by administration of 0.05% 6-n-propyl 2-thiouracil in their drinking water for 8 weeks. Age-matched euthyroid rats were used as controls. Lipid peroxidation in the serum was determined by the end-product malondialdehyde (MDA). Oxidative damage to genomic DNA of aortic tissue and serum was investigated by measuring 8-oxo-dG, one of the base modifications produced in DNA by the reaction of reactive oxygen species. Serum lipids measurement was performed. RESULTS: A hypothyroid state was confirmed by levels of serum thyroid hormones, lipidemic profile, clinical examination, pathological findings and cardiovascular hemodynamics parameters. Hypothyroidism was associated with a significant increase in lipid peroxidation. (MDA 1.44 +/-0.93 vs 0.64 +/- 0.53 nmol/l, p < 0 .01). Levels of 8-oxo-dG on the aortic ring, expressing the oxidant damage on genomic DNA and in the serum, were observed to be significantly raised in the hypothyroid group compared to controls (8-oxodG(serum) 29.22 +/- 17.78 vs. 17.56 +/- 4.44 ng/ml, p < 0.01; 8-oxo-dG(aorta)11.58 +/- 2.70 vs. 4.09 +/- 1.27 ng/ml, p < 0. 001). A statistical correlation between measurements of 8-oxo-dG in the aorta and serum was found (correlation coefficient = 0.36, p < 0.05). A hyperlipidemic profile in hypothyroid animals was revealed. CONCLUSION: Vascular oxidative stress seems to play a pivotal role in the evolution of vascular pathology. Hypothyroidism was associated with increased DNA oxidative damage to the aorta. Hypercholesterolemia and an increase in mean arterial pressure associated with hypothyroidism may have a contributive role in the accumulation of damage in nuclear DNA of the vascular wall. 8-Oxo-dG is one of the mutagenic base modifications produced in DNA. Although clinical studies in other tissues have indicated a direct correlation between in vivo 8-oxo-dG formation and pathological processes, its role on the vascular wall needs further investigation.

Thorough clinical investigation of low cardiac output syndrome after subxiphoid pericardiostomy.

The paradoxical hemodynamic response after surgical or catheter pericardial drainage for cardiac tamponade is an infrequent complication. This case report describes this occasional ominous consequence of surgical pericardial decompression and suggests possible physiological explanations of rapidly progressive heart failure and death.

The mechanical performance and histomorphological structure of the descending aorta in hyperthyroidism.

Thyroid hormones decrease systemic vascular resistance by directly affecting vascular smooth muscle relaxation. There is limited literature about their effect on the mechanical performance of the aortic wall. Therefore, the authors determined the influence of hyperthyroidism on the mechanical properties and histomorphological structure of the descending thoracic aorta in rats. Severe hyperthyroidism was induced in 20 male Wistar rats by administering L-thyroxine (T(4)) in their drinking water for 8 weeks; age-matched normal euthyroid rats acted as controls. Animals were sacrificed, and the mechanical and histomorphometrical characteristics of the descending thoracic aorta were studied. The aortic wall of hyperthyroid rats was stiffer than that of euthyroid animals at the upper physiologic levels of stress or strain (p < 0.05) but less stiff at the lower physiologic and lower levels (p < 0.05). The aorta of hyperthyroid animals compared with that of euthyroid ones showed an increase of the internal and external diameters (p < 0.05), the media area (p < 0.05), the number of smooth muscle cell nuclei (p < 0.05), and the collagen density (p < 0.05) and a decrease in the elastin laminae thickness (p < 0.001) and elastin density (p < 0.001). In hyperthyroid rats, the aortic wall was stiffer at the upper physiologic and higher levels of stress and strain. These changes correlated with microstructural changes of the aortic wall. The coexistence of hyperthyroidism with disease states or clinical conditions that predispose to increased arterial pressure may be associated with increased arterial stiffness and have undesirable consequences on the mechanical performance of the thoracic aorta and hemodynamic homeostasis. These changes could lead to an increased risk for developing vascular complications.

Hyperthyroidism is associated with increased aortic oxidative DNA damage in a rat model.

BACKGROUND: Hyperthyroidism is associated with increased oxidative stress and oxygen free radical production. Oxygen free radicals are implicated in several signalling pathways leading to vascular pathology. The present study evaluates the extent of aortic oxidative stress in experimental hyperthyroidism. MATERIALS AND METHODS: Chronic hyperthyroidism was induced in 20 male Wistar rats; another 20 animals served as controls. Oxidative damage to lipids and genomic DNA was assessed by measuring serum and aortic wall 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) levels (a mutagenic marker of oxidative DNA damage), as well as serum ceruloplasmin, malondialdehyde (MDA) and lipids. RESULTS: Hyperthyroid animals had significantly higher values of serum ceruloplasmin (11.27+/-1.16 vs. 9.58+/-1.17 mg/dl), MDA (5.34+/-1.32 vs. 0.64+/-0.53 nmol/ml) and 8-oxo-dG (33.91+/-9.63 vs. 17.56+/-4.44 ng/ml) compared with controls (p<0.001 for all associations). Aortic 8-oxo-dG levels were elevated in the thyrotoxic compared with the control group (13.01+/-2.38 vs. 4.09+/-1.27 ng/ml, respectively; p<0.001). 8-Oxo-dG measurements in aortic rings and in serum were positively correlated in the hyperthyroid rats (Pearson's correlation coefficient =0.66; p=0.007). CONCLUSION: Hyperthyroidism is associated with increased oxidative stress in the aortic wall. The animal model we describe has provided some preliminary data regarding the effect of hyperthyroidism on the vascular system. Verification of our results and further exploration of our animal model may help determine the association between oxidative DNA damage with functional changes of the vascular wall, such as endothelial function and vascular nitric oxide signalling.

Post-vagotomy mechanical characteristics and structure of the thoracic aortic wall.

This study assessed the long-term effect of vagotomy on the structure and passive mechanical characteristics of the thoracic aorta under a wide range of stresses in vitro. Eight healthy Landrace pigs underwent bilateral vagotomy distal to the origin of the recurrent laryngeal nerve, and 10 pigs were sham-operated. Three months post-surgery, the aorta was excised and specimens from the ascending aorta, arch, and descending thoracic aorta were subjected to histomorphometrical evaluation and uniaxial tensile-testing until failure. Elastic modulus-stress data were plotted and submitted to regression analysis. Structural remodeling after vagotomy was characterized as vascular growth in the ascending aorta and arch, and as thinning in the descending thoracic aorta. In the aortic segments of vagotomized animals, the area density of elastin and collagen was increased, but smooth muscle density was decreased. Similar differences in regression parameters and failure strength between groups were found in all aortic segments, indicating that the vessel wall was stiffer and stronger in vagotomized animals. In the clinical setting, disease states or drugs blocking the regulatory role of the vagi nerves on the aortic wall may have undesirable consequences on the mechanical performance of the thoracic aorta, and therefore on hemodynamic homeostasis.

Topographic anatomy of bronchial arteries in the pig: a corrosion cast study.

The anatomy of porcine bronchial circulation has not been fully described. The purpose of this study was to investigate the extrapulmonary topographic anatomy of bronchial arteries in pig. Ten pigs weighing 15-25 kg were studied. Between one and four bronchial arteries were found in each pig. The bronchoesophageal artery (BEA), tracheobronchial artery (TBA), inferior bronchial artery (IBA) and accessory bronchial artery (ABA) were present in 10/10, 8/10, 6/10 and 2/10 animals, respectively. The trunk of BEA had a diameter of about 3 mm, a length of 1-7 mm, and originated from the anterior and medial aspect of the descending thoracic aorta at the level between the 2nd and 4th thoracic vertebrae (T2-T4) in all animals. The extrapulmonary topographic anatomy of bronchial arteries in pigs exhibits similarities to that of humans. BEA is the main blood supplier of the porcine tracheobronchial tree with a relatively constant location of origin and a sufficient size for anastomosis. These characteristics render BEA the ideal vessel for bronchial revascularization in pigs.

Cervical mediastinoscopy and anterior mediastinotomy in superior vena cava obstruction.

STUDY OBJECTIVES: There is general agreement regarding the diagnostic efficacy of cervical mediastinoscopy (CMDS) and anterior mediastinotomy (AMDT) on patients with superior vena cava obstruction (SVCO), but controversy exists concerning the safety of these two diagnostic methods on that particular subset of patients. The purpose of the present study is to evaluate the safety and diagnostic efficacy of CMDS and AMDT in patients with SVCO. MATERIALS AND METHODS: During the last 28 years, 39 consecutive patients with SVCO underwent biopsy of mediastinal lesions by CMDS (n = 18) or AMDT (n = 19) or both these techniques (n = 2). The medical records of all patients were reviewed, and demographic data, operative notes, perioperative complications, outcome, and histologic diagnoses were examined. The findings were compared with those of 367 patients without SVCO who underwent biopsy of mediastinal lesions during the same period of time. An up-to-date English-language literature search was performed. RESULTS: The sensitivity of CMDS and/or AMDT in detecting malignancies in 39 patients with SVCO was 97.4%, specificity was 100%, and diagnostic accuracy was 97.4%. There was no in-hospital mortality, while morbidity consisted of five major complications and one minor complication, including two major hemorrhages and two airway obstructions. These patients, compared to those without SVCO, showed significantly higher postoperative morbidity (p < 0.001) and had a higher rate of malignancy (p < 0.001). Among 280 patients of the literature review, major hemorrhage was recorded in eight cases and airway obstruction in none. CONCLUSIONS: CMDS and AMDT are effective methods to establish a histologic diagnosis in patients with SVCO. Although their mortality is negligible, they are accompanied by a significantly higher morbidity compared to patients without SVCO. Airway obstruction is a life-threatening complication that can occur in these patients. In our series, patients with SVCO had a higher rate of malignancy compared to patients without SVCO.

Prognostic factors in thymic epithelial tumors undergoing complete resection.

BACKGROUND: The prognostic factors in thymic epithelial tumors (TET) are investigated within a 27-year period in 104 patients submitted to surgical and pathologic complete resection of TET with a mean age of 53 +/- 14.6 years and a male to female ratio of 0.73. METHODS: The medical records of all patients were reviewed and six variables that could affect the short-term and long-term survival were entered into a Cox regression model. Follow-up was obtained from medical records and telephone contacts up to September 2004 or until the patient's death. RESULTS: Overall 5-year and 10-year survival was 83% and 78%, respectively. Univariate Cox regression analysis showed that long survival was affected by the age of the patient at the time of operation, the response of myasthenia gravis to the operation, the tumor recurrence, the histologic type according to the World Health Organization (WHO) classification, and the Masaoka stage. Multivariate analysis revealed that recurrence of the tumor (p = 0.001), Masaoka stages II or III (p < 0.001), elder age of the patient at the time of operation (p = 0.045), and presence of the WHO histologic types B2 or B3 (p = 0.05) were bad prognostic factors. CONCLUSIONS: Recurrence of the tumor, the Masaoka staging, the WHO histologic type, and the age of the patient at the time of operation were the most important prognosticators for patients with TET submitted to complete resection of their tumor.

Myoplasty versus omentoplasty in the surgical treatment of hydatidosis of the liver dome.

BACKGROUND AND AIMS: Even though surgery is the mainstay in the management of hydatid disease of the liver, controversies still exist about the preferred operating technique. This study was conducted to evaluate myoplasty versus omentoplasty for the surgical treatment of hepatic dome hydatidosis. PATIENTS AND METHODS: Sixty-two patients with a hydatid cyst located over the right superior-posterior part of the liver or a cyst adherent to the right hemidiaphragm were classified into two groups according to the type of surgical approach. Group A comprised 50 patients who had undergone thoracoabdominal, right subcostal, or right paramedian incision. Group B comprised 12 patients who had undergone posterior-lateral thoracotomy. Twenty-four patients with a right thoracoabdominal incision underwent partial excision of the cyst with omentoplasty (18 patients), external drainage (four patients), and marsupialization (two patients). RESULTS: Twenty-six patients with a right subcostal or paramedian incision underwent partial resection of the cyst with omentoplasty (15 patients), external drainage (eight patients), and combination of procedures (three patients). Twelve patients that had undergone a right thoracotomy underwent partial excision of the cyst wall with myoplasty of the right hemidiaphragm. Surgical approaches such as thoracoabdominal, right subcostal, or paramedian incision were associated with higher morbidity rate than thoracotomy alone (P < 0.03). In addition, patients with myoplasty of the right hemidiaphragm were associated with a lower morbidity rate than those with omentoplasty (P < 0.02). Five patients had recurrent disease and were reoperated upon. Partial cystectomy and myoplasty of the right hemidiaphragm was performed with excellent results. CONCLUSIONS: These results suggest that a thoracic approach, with myoplasty of the right hemidiaphragm and high-vacuum drainage, might produce low complication and recurrence rates and the best clinical results. Consequently, it is a promising procedure that requires more application and evaluation.

AIDS-related cardiac tamponade: is surgical drainage justified?

In order to evaluate the usefulness of surgical drainage in the treatment of patients with acquired immunodeficiency syndrome (AIDS)-related cardiac tamponade, we reviewed our experience with subxiphoid pericardiostomy on 5 consequent such patients. One patient died in the immediate postoperative period and the remaining 4 died within 21 weeks after the operation. Similar results have been reported by other authors who found that surgical drainage has no diagnostic or therapeutic benefit over pericardiocentesis in this particular group of patients. Based on our limited experience and the data of the literature, we feel that surgical drainage cannot be justified as the primary method of treatment of AIDS-related cardiac tamponade.

Pedicled myocutaneous and muscle flaps in the management of complicated cardiothoracic problems.

The purpose of this study was to review our experience with the management of patients with complicated cardiothoracic problems by the use of pedicled myocutaneous or muscle flaps, and discuss the various methods of reconstruction. Over the last 11 years, we have treated 54 patients with complicated cardiothoracic problems by reconstruction with pedicled myocutaneous or muscle flaps. The underlying causes were chest wall tumours (n = 13), radionecrosis of the chest wall (n = 12), deep or chronic sternal infections (n = 25), and bronchopleural fistulas (n = 4). The most commonly used muscles for reconstruction were pectoralis major and the rectus abdominis. Our results compare favourably with those reported elsewhere. We conclude that although the use of pedicled myocutaneous or muscle flaps is not free of complications, it is an effective and reliable method for the management of patients with complicated cardiothoracic problems.

Surgical treatment of esophageal perforation.

BACKGROUND/AIMS: In spite of the progress made during the last few decades, esophageal perforation continues to carry a serious prognosis. The aim of this study is to present our experience with surgical treatment of esophageal perforation. METHODOLOGY: Eight patients with esophageal perforation were submitted to surgical treatment with varying time intervals between the perforation and the operation. The surgical technique was individualized according to the location of the perforation and the severity of the local inflammatory and necrotic findings. Follow-up data was obtained by follow-up examination or telephone contact with the family doctors. The medical records were reviewed. The cause, the location and the clinical manifestations of perforation, the underlying esophageal disease, the imaging techniques and other examinations which were used to establish diagnosis, the time interval between the perforation and the operation, the surgical techniques, the outcome, the complications, the duration of postoperative hospitalization, and the late results were analyzed. RESULTS: The perforation was due to iatrogenic injury in 6 of 8 patients. Underlying esophageal disease was present in 4 patients. The mean time interval between the perforation and the operation was 4.3 days. Primary repair was attempted in 5 patients, exclusion-diversion of the esophagus in 2 and thorough drainage in 1 patient. There was no mortality. Primary closure was achieved in 80% of the patients in whom primary repair was attempted. Seven out of 8 patients were alive 46-150 (mean, 99.12) months after the operation. CONCLUSIONS: Surgery is the treatment of choice for patients with esophageal perforation including those seen more than 24 hours after the onset of symptoms. The chosen surgical technique depends on the location of perforation and the severity of local inflammatory and necrotic findings.

Risk factors affecting the survival of patients with pericardial effusion submitted to subxiphoid pericardiostomy.

STUDY OBJECTIVES: Surgical subxiphoid drainage of the pericardial cavity has been established as a safe and effective method of treatment of pericardial effusion; however, the risk factors affecting survival of these patients have not been clarified. The aim of this study was to investigate the risk factors affecting the short-term and long-term survival of patients with pericardial effusion submitted to subxiphoid pericardiostomy. DESIGN: Retrospective study. PATIENTS: The records of all patients who underwent subxiphoid pericardiostomy for treatment of pericardial effusion from January 1991 to December 2001 were reviewed. According to underlying pathology the patients were classified into four groups: (1) hematologic malignancies (n = 17); (2) other malignant diseases (n = 29); (3) AIDS (n = 5); and (4) other benign diseases (n = 53). Multivariate Cox regression analysis was used to test the relationship of short-term and long-term survival to age, sex, cardiac tamponade, pericardial malignant invasion, postoperative low cardiac output syndrome (PLCOS), and underlying pathology. RESULTS: There were 104 patients (59 men) with a mean age of 53.6 years (range, 13 to 85 years). Follow-up was complete in 99 patients (95.2%) for a mean of 23.9 months (range, 0 to 92 months). Overall 30-day mortality was 16.3%, while operation-related mortality was 4.8%. The underlying disease was the main risk factor for short-term and long-term survival (p < 0.00001), while PLCOS was a major predictor of early mortality (p = 0.029). Patients with AIDS showed the worst prognosis. On the contrary, patients with hematologic malignancies presented significantly longer survival compared to all other patients with malignant diseases (p < 0.05). CONCLUSIONS: The underlying disease was the main risk factor for short-term and long-term survival, while PLCOS was a major predictor of early mortality. The prognosis of AIDS patients with pericardial effusion was grave; therefore, surgical intervention in such patients should be reevaluated. Patients with hematologic malignancies had significantly longer survival compared to all other patients with malignant diseases.

Diaphragm myoplasty in the prevention of complications after surgery of hydatid disease of the liver.

A variety of techniques have been used for surgical treatment of hepatic hydatid cysts. The objective of this study is to describe the technique of diaphragm myoplasty, and to present our experience in the treatment of selected patients with hydatid disease of the liver by means of this alternative surgical technique. The technique combines a diaphragm myoplasty with a wide partial cystectomy performed through a right thoracophrenotomy incision. The medical records of the patients with hydatid disease of the liver who were submitted to surgical treatment with this technique were reviewed. The clinical manifestations, laboratory examinations, operative notes, and postoperative results were analyzed. Eight consecutive patients with hepatic hydatid cyst were operated on. The cyst was located in the posterior-superior aspect of the right hepatic lobe in all patients. Five patients suffered from recurrence of a previously operated hepatic hydatid cyst, and two patients suffered from complications of their disease. There was no in-hospital mortality or morbidity. The early and late postoperative results compare favorably with the results of other investigators. The alternative surgical technique for treatment of selected patients with hepatic hydatid disease is indicated for patients with a cyst located in the posterior-superior aspect of the right hepatic lobe, especially if there is a recurrence of the disease after a previous surgery or involvement of the diaphragm and/or the intrathoracic organs. The technique provides easy and safe access to the cyst and carries most of the advantages of omentoplasty.