Distal Aortic Segments Research Articles

Type A aortic dissection with arch entry tear: Surgical experience in 104 patients over a 12-year period

ObjectiveTo evaluate the efficacy of the frozen elephant trunk (FET) and total arch replacement (TAR) technique (FET + TAR) in the management of type A aortic dissection (TAAD) with arch entry tear. MethodsClinical outcomes were analyzed for 104 TAAD patients with arch entry tear undergoing FET + TAR at 4.7 ± 3.5 days from symptom onset and compared with 728 TAAD patients with entry tears in elsewhere. The mean patient age was 49.3 ± 9.3 years, compared with 45.6 ± 10.8 years in other TAAD patients (P < .001). There were 84 men (80.8%). Hypertension was seen in 84.6% (88/104). ResultsOperative mortality was 8.6% (9/104). Spinal cord injury occurred in 3 cases (2.9%), stroke in 2 (1.9%), renal failure in 4 (3.8%) and limb ischemia in 2 (1.9%). Follow-up was 100% (95/95) at mean 5.6 ± 2.6 years (range 1.3-11.6). Late death occurred in 2 cases (1.9%). Survival and freedom from late adverse events were 89.2% (95% confidence interval [CI], 81.3%-93.9%) and 85.0% (95% CI, 76.3%-90.8%) at 8 years, respectively. Both the stented and unstented distal aortic segments showed significant trends of false lumen shrinkage and true lumen expansion over time (P < .001). Of the 65 CT scans at mean 4.6 ± 2.9 years postoperatively, the false lumen was completely obliterated in 63. Risk factors for arch entry tear were hypertension (odds ratio [OR], 2.091; 95% CI, 1.186-3.687; P = .011) and age (OR, 1.025; 95% CI, 1.002-1.048; P = .032). ConclusionsTAAD with arch entry tear was treated safely and durably by FET + TAR. Although patients with arch entry tear were somewhat older than other patients, operative mortality was not substantially higher despite their older age and arch location of entry tear. These results argue favorably for the use of the FET + TAR technique in the management of TAAD patients with arch entry tears.

Blunt traumatic aortic rupture of the proximal ascending aorta repaired by resection and direct anastomosis

Traumatic aortic injury represents 15% of motor vehicle related deaths with death occurring at the scene in 85% of the cases. Aortic disruptions usually occur at the isthmus in a transverse fashion with all three of the aortic layers being involved. Herein, we report the case of a 68-year old man with no prior medical history who was struck by a vehicle while riding his bicycle. The ruptured segment of aorta was resected circumferentially and interrupted horizontal mattress pledgeted prolene sutures were used to ensure full thickness aortic integrity of the proximal and distal aortic segments. The aorta was closed with a single-layer technique using 4/0 prolene suture. There were no postoperative complications and patient was discharged on Day 44. The case here discussed demonstrates a rare presentation of blunt aortic injury. The proximal ascending aorta is an unusual site of transection following blunt trauma with few reports in the literature. We were able to repair the aorta with direct suture, thus avoiding the use of artificial material.

Staged hybrid approach using proximal thoracic endovascular aneurysm repair and distal open repair for the treatment of extensive thoracoabdominal aortic aneurysms

Repair of patients with extent I and II thoracoabdominal aortic aneurysms (TAAAs) is associated with significant morbidity and mortality, whereas repair of more distal extent III and IV TAAAs has a lower risk of paraplegia and death. Therefore, we describe an approach using thoracic endovascular aneurysm repair (TEVAR) as the index operation to convert extent I and II TAAAs to extent III and IV TAAAs amenable to subsequent open aortic repair to minimize patient risk. Between July 2007 and March 2012, 10 staged hybrid operations were performed to treat one extent I and nine extent II TAAAs. Aortic aneurysm pathology included five chronic type B dissections, three acute type B dissections, and two penetrating aortic ulcers. Initially, the proximal descending thoracic aorta was repaired with TEVAR for coverage of the most proximal fenestration or penetrating ulcer, with seven elective and three emergent repairs. Interval open distal aortic replacement was performed in a short-term planned setting or for progressive dilation of the distal aortic segment. In the open repair, the proximal end of the graft was sewn directly to the distal end of the TEVAR and outer wall of the aorta. Average patient age was 48 years, and 60% were men. Risk factors included hypertension (80%), current tobacco use (50%), and Marfan syndrome (30%). Complications after TEVAR included type IA (n=1) and type II (n=3) endoleaks, pleural effusions (n=3), and acute kidney injury (n=1). Three patients required endovascular reinterventions. In patients with dissection, persistent filling of the false lumen was common and associated with distal thoracic aortic dilation. Complications of open repair included acute kidney injury in two patients, but no cardiac, pulmonary, or neurologic morbidity. Median time between TEVAR and open repair was 14 weeks. Most importantly, no deaths or neurologic deficits occurred after either procedure during a median follow-up of 35 weeks. A staged hybrid approach to extensive TAAAs combining proximal TEVAR, followed by interval open distal TAAA repair, is safe and appears to be an effective alternative to traditional open repair. This approach may decrease the significant morbidity associated with single-stage open extent I and II TAAA repairs and may be applicable to multiple TAAA etiologies.

Long-term implications of emergency versus elective proximal aortic surgery in patients with Marfan syndrome in the Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions Consortium Registry

Patients with Marfan syndrome with aortic root aneurysms undergo elective aortic root replacement to avoid the life-threatening outcomes of aortic dissection and emergency repair. The long-term implications of failed aortic surveillance leading to acute dissection and emergency repair are poorly defined. We compared the long-term clinical courses of patients with Marfan syndrome who survive emergency versus elective proximal aortic surgery. The Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions Registry is a National Institutes of Health-funded multicenter database and biorepository that enrolls patients with genetically triggered thoracic aortic aneurysms. Of the 635 patients with Marfan syndrome enrolled as of March 2011, 194 had undergone proximal aortic replacement. Patients were grouped according to emergency (n = 47) or elective (n = 147) status at the time of surgery. Patients in the emergency group were more likely to have incomplete proximal aortic resection; 83% of emergency procedures included aortic root replacement, compared with 95% of elective procedures. At long-term follow-up (mean, >6 years), the emergency group had a higher incidence of chronic dissection of the distal aorta and significantly larger diameters in distal aortic segments than elective patients. Patients in the emergency group had undergone more operations (1.31 vs 1.11 procedures/patient; P = .01) and had lower activity scores on a health-related quality of life survey. For patients with Marfan syndrome, failed aortic surveillance and consequent emergency dissection repair have important long-term implications with regard to the status of the distal aorta, need for multiple procedures, and quality of life. These findings emphasize the importance of aortic surveillance and timely elective aortic root aneurysm repair for patients with Marfan syndrome.

Parsing Aortic Aneurysms

See related article, pages 574–581 Aortic aneurysms are progressive enlargements of the aorta that can lead to life-threatening degenerative changes in the structure of the artery wall including medial dissections and wall rupture. The abdominal aorta is the most common site of aneurysm formation, yet the ascending thoracic aorta can also exhibit aneurysmal expansion with potentially dire outcomes. Ascending aortic aneurysms are frequently associated with connective tissue diseases such as Marfan's syndrome, a disorder of the extracellular matrix protein fibrillin-1.1 Mouse models carrying hypomorphic mutations in fibrillin-1 also develop aortic dilations associated with macrophage infiltration, elastin fragmentation, and enhanced transforming growth factor (TGF)β signaling in the artery wall.2 Aortic aneurysms in fibrillin-1 hypomorphic mice can be prevented by treatment with either anti-TGFβ neutralizing antibodies or with the angiotensin II (Ang II) type 1 (AT1) receptor antagonist losartan.3 Indeed, chronic infusion of Ang II into apoE −/− mice is an effective experimental model to induce aortic aneurysm formation and to study the molecular pathways underlying its pathogenesis.4 Ang II signals through 2 types of angiotensin receptors, AT1 and AT2.5 AT2 receptors have been shown to elicit antiproliferative responses in vascular smooth muscle cells (SMCs), possibly by antagonism of signaling through AT1 receptors.5 In mice, the AT1 receptor exists as 2 subtypes, AT1a and AT1b, and both receptor subtypes are expressed in the artery wall. The receptor that mediates angiotensin-induced contractile responses in vascular smooth muscle is predominantly the AT1b subtype.6 The AT1 receptor subtype that mediates aortic aneurysm formation has been unknown. In a study that appears in this issue of Circulation Research , Rateri et al used a series of mouse models to genetically dissect the process of Ang II–induced aneurysm …

Invited commentary

In the current manuscript, the authors present data demonstrating an association between dilated aortic root (DAR) and concomitant increased distal aortic segment diameters. The pattern of more diffuse disease being associated with tricuspid aortic valve, as opposed to bicuspid aortic valve (BAV), is somewhat surprising, but likely highlights one of the limitations of this analysis in that it represents a small sample size – only 19 patients had BAV. Certainly a larger population study could demonstrate a stronger association. Another weakness of this study is that it represents a single snapshot in time. While DAR is associated with concurrent increased distal aortic diameters, it is unclear as to what the natural history of this association will be. Will further segments of the aorta degenerate, and will areas that are dilated, but not aneurysmal, become so over time? The authors suggest that it may be necessary to screen patients with DAR for abdominal aortic aneurysm (AAA). Perhaps with more data obtained over time we may find it is necessary to continue to monitor the entire aorta of these patients as they age. The data presented supports the concept that aortic aneurysmal disease (AAD) is associated with a diffuse aortic pathology. The population is aging and patients are surviving longer after surgery for aneurysmal disease. It is becoming increasingly apparent that patients with AAD at one location may develop subsequent aneurysmal degeneration at sites either contiguous with, or remote from, the site of initial pathology. This suggests that patients with AAD have an inherently abnormal aorta that is at risk for further aneurysmal degeneration. Data from the current manuscript lend further support to this hypothesis. Knowing this, future surgical approaches to patients with AAD may need to be viewed as palliative and no longer curative. Operative plans may need to be developed realizing that radiologically normal appearing aortic segments are actually at risk for subsequent degeneration and ultimate failure of that repair. We have an increasing understanding of the molecular mechanisms that contribute to AAD. We lack significant knowledge, however, on what baseline abnormalities place certain aortas at risk for future aneurysmal degeneration, particularly in patients without a known connective tissue disorder. In addition, we have a poor understanding of what events trigger the process of aortic degeneration. It is this fundamental knowledge deficit that hinders our ability to better explain the correlations outlined in the current manuscript, or that explain the development of subsequent aneurysmal degeneration that we are identifying in our patients. We must continue to focus efforts on improving our understanding of the genetic and molecular events associated with AAD. This is accomplished through population studies, genetic analyses, and translational and basic research evaluating the mechanisms of aneurysm formation. Only with this knowledge will we better identify patients at risk for further aneurysmal degeneration, or develop technologies to assess in vivo aortic integrity to assure adequate long-term repair and survival from AAD. Dilated aortic root is related to a global aortic dilating diathesisJournal of Vascular SurgeryVol. 52Issue 4PreviewThe purpose of this study was to analyze the association between the dilatation of the aortic root and the diameters of the rest of the aorta and to identify some related factors that could be used to identify patients at higher risk of presenting with an aortic aneurysm. Full-Text PDF Open Archive

Arquitetura da parede vascular de segmentos torácico e abdominais da aorta de macaco prego (Cebus apella)

O segmento torácico da aorta em macaco prego apresentou na túnica íntima uma lâmina elástica interna evidente, estando também presente em todos os segmentos aórticos abdominais analisados nesta espécie. A túnica média aórtica, ao nível torácico, mostrou uma quantidade média de 23,12 lâminas elásticas, tendo disposição circular e oblíqua em relação à luz vascular, e a túnica adventícia apareceu formada por fibras colágenas, dispostas irregularmente entre uma quantidade relativamente menor de fibras elásticas e de fibras musculares lisas. A túnica média do segmento abdominal aórtico, neste primata, observada ao nível supra-renal, apresentou em média 19,12 lâminas elásticas que apareceram relativamente desorganizadas e fragmentadas. Ao nível aórtico infra-renal, foram evidenciadas, na túnica média 11,75 lâminas elásticas, em média, e próximo da emissão das artérias ilíacas comuns a túnica média aórtica tinha cerca de 8,37 lâminas elásticas, as quais estavam entremeadas por fibras musculares lisas e por fibras colágenas que aparentavam aumentar a sua concentração próximo à adventícia. A lâmina elástica externa só foi visível no segmento abdominal aórtico mais distal, ou seja, próximo da emissão das artérias ilíacas comuns.

Predictors for aneurismal formation

Predictors for aneurismal formation

Impact of aortic dimensions and pulse pressure on late aneurysm formation in operated type A aortic dissection. A magnetic resonance imaging study

Patients operated on for type A aortic dissection remain at risk of long-term aneurysm development, the main cause for late death. The aim of this study was to identify early predictors for aneurysm formation at three-years after surgery. A study group of 70 consecutive patients (52 +/- 10 years-old, 41 male), operated on for aortic dissection with replacement of the ascending segment, was evaluated prospectively for three-years. In order to detect aneurysm formation, the dimension of residual distal aortic segments was obtained soon after surgery and then annually for three years using cardiovascular magnetic resonance. During follow-up (38 +/- 2.6 months), aneurysm was found in 25 patients (35%) involving residual segments. Larger initial dimension of segments, higher pulse pressure, lower distensibility of residual segments and the presence of a residual flap were univariately associated with aneurysm. Multivariate analysis identified the initial dimension (mm) of the descending thoracic aorta (OR 1.47, 95%CI: [1.19-1.82]) and pulse pressure (OR 1.43,95%CI: [1.10-1.86]) as independent variables for aneurysm formation. A risk score using pulse pressure and descending thoracic dimension was constructed. Patients with <or=24 points had no late aneurysm formation, while those with a score >or=45 yielded 100% of aneurysm frequency. Type A aortic dissection treated by graft interposition is associated with a high risk of aneurysm formation. Early post-operative pulse pressure and the descending thoracic aortic dimension were independent variables and seem to be the main predictors for the outcome.

The Reversed Elephant Trunk Technique Used for Treatment of Complex Aneurysms of the Entire Thoracic Aorta

A preferred technique for the staged treatment of patients with aneurysms involving the entire thoracic aorta is the elephant trunk technique, with replacement of the proximal (ascending and transverse aortic arch) aorta as the initial procedure. Some patients, however, need to have the distal aortic segments (descending and thoracoabdominal aorta) addressed during the first operation. We evaluated outcomes in a series of patients who underwent distal aortic replacement first using the reversed elephant trunk technique. Thirty-eight patients underwent first-stage graft repair of the descending thoracic (n = 3) or thoracoabdominal (n = 35) aorta using the reversed elephant trunk technique. Twelve patients (32%) ultimately underwent second-stage aortic arch replacement after a mean interval of 3.9 months (range, 1.6-14 months). The operative mortality for the initial procedure was 16% (6/38 patients). One patient had a stroke (3%) and 1 patient developed paraparesis (3%). In the interval between the 2 procedures, there were 4 late deaths (4/32; 13%), 1 due to respiratory failure and 3 due to unknown causes. After the 12 completion procedures, there was 1 in-hospital death (8%) and there were no strokes. Five-year survival for the overall group was 51.3 +/- 10.8%. Surgical treatment of aneurysms involving the entire thoracic aorta remains challenging and is associated with substantial morbidity and mortality. The reversed elephant trunk technique facilitates staged repair in patients who require distal aortic replacement during the first operation.

Increased blood flow causes coordinated upregulation of arterial eNOS and biosynthesis of tetrahydrobiopterin

Shear stress, imposed on the vascular endothelium by circulating blood, critically sustains vascular synthesis of nitric oxide (NO). Endothelial NO synthase (eNOS) activity is determined by heat shock protein 90 (HSP90), caveolin-1, and the cofactor tetrahydrobiopterin (BH4). To determine whether increased blood flow concomitantly upregulates eNOS and GTP cyclohydrolase I (GTPCH I, the rate-limiting enzyme in BH4 biosynthesis), an aortocaval fistula model in the rat was employed wherein aortic blood flow is enhanced proximal but decreased distal to the fistula. Eight weeks after the creation of the aortocaval fistula, the proximal and distal aortic segments were harvested; sham-operated rats served as controls. Vasomotor function was assessed by isometric force recording. Expression of eNOS, HSP90, caveolin-1, Akt, phosphorylated eNOS (eNOS-Ser1177), and GTPCH I were determined by Western blot analysis. Biosynthesis of BH4 and GTPCH-I activity was examined by HPLC. In the aortic segments exposed to increased flow, contractions to KCl and phenylephrine were reduced, whereas endothelium-dependent relaxations were not affected compared with sham-operated or aortic segments with reduced blood flow. Expression of eNOS, caveolin-1, phosphorylated Akt, and eNOS-Ser1177 was enhanced in aortas exposed to increased blood flow. High flow augmented levels of cGMP and BH4 and increased expression of GTPCH I. In aggregate, these findings provide the first demonstration in vivo that coordinated vascular upregulation of eNOS, and GTPCH I accompanies increased blood flow. This induction of GTPCH I increases BH4 production, thereby optimizing the generation of NO by eNOS and thus the adaptive, vasorelaxant response required in sustaining increased blood flow.

Aortic Root Anomalies of the Neck Presenting in Adults. Review of the Literature with Three Case Reports

Aortic Root Anomalies of the Neck Presenting in Adults. Review of the Literature with Three Case Reports

Chest radiography for the diagnosis of acute aortic syndrome

Purpose We sought to assess the diagnostic accuracy of routine chest radiography for the acute aortic syndrome (dissection, intramural hematoma, penetrating ulcer, or nondissecting aneurysm). Methods During a 6-year period, 216 patients (143 men, 73 women; mean [± SD] age, 58 ± 17 years) underwent chest radiography for suspected acute aortic syndrome. Chest films were re-evaluated blindly for aortic disease, based on an overall impression using standard criteria such as widening of the aortic contour and mediastinal shadow. Findings were matched to tomographic images, anatomical inspection, or both, as the criterion standard; aortic disease was confirmed in 109 (50%) of the patients. Results Chest radiography had a sensitivity of 64% (70/109) and a specificity of 86% (92/107) for aortic disease. Sensitivity was 67% (38/57) for overt aortic dissection, 61% (22/36) for nondissecting aneurysm, and 63% (10/16) for intramural hemorrhage or penetrating ulcer. However, sensitivity was lower for pathology confined to the proximal aorta (47% [21/45]) than for disease involving distal aortic segments (77% [49/64]). A receiver operating characteristic curve analysis of aortic diameters failed to identify a threshold for the diagnosis of aortic disease. Conclusion Chest radiography is of limited value for diagnosing the acute aortic syndrome, particularly for conditions confined to the ascending aorta. Since a definitive diagnosis is required in any patient with clinically suspected acute aortic syndrome, routine chest radiography should be replaced by tomographic aortic imaging.

Is the bentall procedure for ascending aorta or aortic valve replacement the best approach for long-term event-free survival?

Background This retrospective analysis of a selected series of Bentall procedures may be useful in evaluating the results of valve-sparing operations, an increasingly popular alternative for replacement of the ascending aorta and aortic valve. Methods One hundred forty-two elective patients younger than 65 years without concomitant procedures who underwent replacement of the thoracic aorta and aortic valve between 1989 and 2000 were studied; 85% were men, and the median age was 46 years (range, 13 to 64 years). Degenerative disease of the aorta was the most common cause requiring operation (86%, including 46% with a bicuspid aortic valve); 8% had chronic dissection, and 6% had atherosclerotic aneurysms. The ascending aorta was replaced in 94 patients (66%); 45 patients (32%) underwent hemiarch replacement, and in 3 patients (2%) the total arch was replaced. A mechanical valve was used in 88%, and a biologic valve, in 12%. Results There were no intraoperative deaths. Two patients had a stroke postoperatively, one of which was fatal. Complications during follow-up included 2 cases of endocarditis, 1 peripheral thromboembolic event, and 10 instances of significant bleeding (requiring hospitalization or transfusion). Surgery for distal aortic segments was performed in 4 patients, but no patient required reoperation in the proximal aorta. Kaplan-Meier curves show overall survival is 0.95 (95% confidence intervals, 0.9 to 0.99) at 5 years and 0.93 (95% confidence intervals, 0.86 to 0.99) at 8 years, and event-free survival is 0.85 (95% confidence intervals, 0.78 to 0.92) at 5 years and 0.78 (95% confidence intervals, 0.68 to 0.88) at 8 years. Conclusions The button Bentall procedure can be performed with excellent short-term and long-term results in relatively uncomplicated elective patients in whom aortic valve disease is combined with dilatation of the ascending aorta. Results of this traditional operation are the standard against which the long-term outcome of newer approaches, such as valve-sparing operations, should be compared.

Regional differences in phorbol 12-myristate 13-acetate stimulation of PDGF production in the normal canine aorta

Objective: Platelet-derived growth factor (PDGF) is a potent smooth muscle cell mitogen implicated in the development of intimal hyperplasia and atherosclerosis. A regional variation in canine aortic production of PDGF (greater in the distal than in the proximal aorta) was demonstrated previously in organ culture. The response of aortic segments in organ culture, as well as of aortic endothelial cells and smooth muscle cells, to stimulators of PDGF secretion—phorbol 12-myristate 13-acetate (PMA) and thrombin—was assessed to elucidate whether these regional variations were due to intrinsic differences in the abilities of cells to produce PDGF. Methods: Proximal and distal aortic segments were removed from 10 dogs and placed in organ culture, then treated with PMA or thrombin for 72 hours. PDGF in the conditioned media was measured by radioreceptor assay. Results: PDGF production in the distal, unstimulated aorta was 2.5-fold higher than that in the proximal aorta (P <.05). Treatment of the proximal aorta with 10 nmol/L and 100 nmol/L PMA increased PDGF production twofold and threefold, respectively, whereas no increase with PMA treatment was seen in the distal aorta. After thrombin treatment, no increase in PDGF production was noted in the proximal aorta and only a minimal increase was noted in the distal aorta. Endothelial cells and smooth muscle cells (n = 6) were cultured from four aortic segments (ascending thoracic, descending thoracic, abdominal, and infrarenal) and treated with PMA. PDGF production by unstimulated endothelial cells from the infrarenal aorta was 2.5-fold higher (P <.01) than that from the ascending thoracic aorta. With PMA treatment, PDGF secretion increased in endothelial cells from all segments, the greatest percentage increase being observed in the proximal segments. Thrombin also increased PDGF release from endothelial cells, but with no regional variation. Unstimulated smooth muscle cells did not exhibit regional variation in PDGF production and did not increase PDGF secretion after treatment with PMA or thrombin. Conclusions: These findings suggest that endothelial cells in the aorta may have a differential capacity to produce PDGF in response to stimulants, reflecting intrinsic differences in endothelial cells from the proximal aorta versus the distal aorta, and this may account in part for the propensity of the distal aorta to develop atherosclerosis. (J Vasc Surg 2000;32:584-92.)

Hemodynamic monitoring during left atriofemoral bypass for resection of a postductal aortic isthmus stenosis: Current role of intraoperative transesophageal echocardiography

Hemodynamic monitoring during left atriofemoral bypass for resection of a postductal aortic isthmus stenosis: Current role of intraoperative transesophageal echocardiography

Acute infectious mitroaortic endocarditis in association with acute aortic dissection. Surgical management of an unusual combination of diseases

A 58-year-old man with acute mitral and aortic endocarditis suffered an acute ascending aortic dissection. The patient had a double valve replacement, combined with replacement of the ascending aorta with a Dacron graft and sealing and closure of the proximal and distal aortic segments with surgical glue. Six months after the operation the patient is doing well with normal function of both valve prostheses and aortic vascular graft.

Guanine nucleotide-binding proteins in aortic smooth muscle from hypertensive rats.

To explore the hypothesis that altered vascular muscle signal transduction may underlie some of the vascular changes observed in hypertensive models, we measured expression of GTP-binding protein (G protein) alpha-subunits, Gs, G(i), and Gq, in aortic muscle of reduced renal mass and sham-operated rats and proximal and distal aortic segments from rats with interrenal aortic coarctation (IR-AC). G protein expression was measured by immunoblot analysis. When we probed aortic muscle membrane with G(i) and Gq alpha-subunit antibodies, we identified 41- and 42-kD immunoreactive proteins, respectively. Three immunoreactive bands specific to Gs alpha-subunit antibody were resolved. Immunoreactive blot densities were compared. In aortic muscle membrane of reduced renal mass rats (blood pressure, 148 +/- 7 mm Hg), we found significantly reduced Gs and G(i) blot densities compared with sham-operated controls (blood pressure, 99 +/- 12 mm Hg). There were no differences in Gq blot densities between reduced renal mass and control rats. Gs and G(i) blot densities were significantly lower in IR-AC proximal aortic segments (carotid pressure, 165 +/- 5 mm Hg) and distal aortic segments (femoral pressure, 121 +/- 4 mm Hg) than in aortas of sham-operated controls. In contrast, Gq expression was significantly increased in the high-pressure proximal aortic segments compared with low-pressure distal aortic segments from IR-AC rats. Thus, altered G protein expression occurs in aortic muscle from nongenetic rat models of hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Reoperations after operation on the thoracic aorta: Etiology, surgical techniques, and prevention

Recurrent aortic aneurysms, persistent or new dissection, new onset of valvular and coronary artery disease, graft infection, and prosthetic endocarditis are not rare after thoracic aortic operations; they can be difficult to diagnose and represent a formidable surgical challenge. Between 1977 and 1991, 876 operations were performed on the thoracic aorta in our institution: 340 in dissections, 299 in true aneurysms, 150 for aortic remodeling and external wall support during aortic valve replacement, and 87 for miscellaneous causes. During the same period, there were 193 additional reoperations. Vascular reoperations on abdominal aorta and peripheral arteries accounted for 73 cases and are not further discussed in this study. The reasons for reoperation (n = 130) in 120 patients were: failure of biologic valves (n = 23); aneurysm recurrence in a proximal or distal aortic segment (n = 21); pseudoaneurysm formation at suture lines (n = 13); new dissection or dilatation involving ascending aorta (n = 11), aortic arch (n = 13), and descending aorta (n = 10); aneurysm after aortic remodeling (n = 13); new onset of valvular disease (n = 5); and new onset of coronary disease (n = 5). Infected aortic graft and prosthetic endocarditis accounted for 10 reoperations, and a planned two-staged procedure was performed in 6 patients. Omitting the failed biologic valves, reoperations were performed on the aortic segment previously operated on in 69.3% of the cases and on other thoracic segments in 30.7%. Overall hospital mortality rate after reoperation was 5.8%. A significant decrease in operative mortality was observed in the most recent period (3.0% between 1989 and 1991). Reoperations are technically demanding, and some of them are preventable; therefore (1) graft inclusion technique should be abandoned in ascending aortic operation due to formation of false aneurysms; (2) in patients with Marfan syndrome, complete repair of the diseased aorta should be attempted during the initial operation; (3) aortic arch dissection should be repaired definitively during the first operation in low-risk patients; (4) biological valves should be avoided in aneurysm operations; and (5) homograft replacement is the treatment of choice in prosthetic endocarditis or in infected composite graft after an aortic valve or ascending aortic operation.

A Ca(2+)-dependent K+ current is enhanced in arterial membranes of hypertensive rats.

This study was designed to investigate the role and regulation of arterial membrane K+ channels in hypertension. Aortic segments from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were suspended for isometric tension recording. In other experiments, proximal aortic segments (PS) (exposed to high pressure) and distal aortic segments (DS) (exposed to lower pressure) were removed from surgically coarcted Sprague-Dawley rats and similarly prepared. Aortas from SHR and PS dose-dependently contracted to the K+ channel blocker tetraethylammonium (TEA) (0.1-10 mM), and this contraction was abolished by preincubation with 0.1 microM nifedipine. In contrast, the same concentrations of TEA did not contract either WKY or DS aortas. Since block of K+ channels by TEA had a different effect on aortic segments exposed to high versus low blood pressure, we compared whole-cell K+ currents in isolated vascular cells from the same aortas. The reversal potentials of depolarization-induced outward currents in WKY, SHR, DS, and PS aortic cells showed a Nernst relation to external K+ concentration indicative of selective K+ permeability. TEA (1 and 10 mM) was equipotent in blocking these K+ currents in patch-clamped cells from all aortic preparations, suggesting that the lack of TEA-induced contractions in WKY and DS aortas was not due to an absence of TEA-sensitive K+ channels in these arterial membranes. However, when the Ca2+ ionophore A23187 (10 microM) was used to increase the level of cytosolic Ca2+ in patch-clamped cells, the K+ current density in SHR and PS aortic cells was twofold or more higher than in WKY and DS cells.(ABSTRACT TRUNCATED AT 250 WORDS)