Tam T. Huynh

Remodeling of an acellular collagen graft into a physiologically responsive neovessel.

Surgical treatment of vascular disease has become common, creating the need for a readily available, small-diameter vascular graft. However, the use of synthetic materials is limited to grafts larger than 5–6 mm because of the frequency of occlusion observed with smaller-diameter prosthetics. An alternative to synthetic materials would be a biomaterial that could be used in the design of a tissue-engineered graft. We demonstrate that a small-diameter (4 mm) graft constructed from a collagen biomaterial derived from the submucosa of the small intestine and type I bovine collagen has the potential to integrate into the host tissue and provide a scaffold for remodeling into a functional blood vessel. The results obtained using a rabbit arterial bypass model have shown excellent hemostasis and patency. Furthermore, within three months after implantation, the collagen grafts were remodeled into cellularized vessels that exhibited physiological activity in response to vasoactive agents.

Distal Aortic Perfusion and Cerebrospinal Fluid Drainage for Thoracoabdominal and Descending Thoracic Aortic Repair: Ten Years of Organ Protection

Objective To report the long-term results of our experience using cerebrospinal fluid drainage and distal aortic perfusion in descending thoracic and thoracoabdominal aortic repair. Summary Background Data Repair of thoracoabdominal and thoracic aortic aneurysm by the traditional clamp-and-go technique results in a massive ischemic insult to several major organ systems. Ten years ago, we began to use distal aortic perfusion and cerebrospinal fluid drainage (adjunct) to reduce end-organ ischemia. Methods Between January 1991 and February 2003, we performed 1004 thoracoabdominal or descending thoracic repairs. Adjunct was used in 741 (74%) of 1004. Multivariable data were analyzed by Cox regression. Number needed to treat was calculated as the reciprocal of the risk difference. Results Immediate neurologic deficit was 18 (2.4%) of 741 with adjunct and 18 (6.8%) of 263 without (P < 0.0009). In high-risk extent II aneurysms, the numbers were 11 (6.6%) of 167 with adjunct, and 11 (29%) of 38 without. Long-term survival was improved with adjunct (P < 0.002). The long-term survival results persisted after adjustment for age, extent II aneurysm, and preoperative renal function. Conclusion Use of adjunct over a long period of time has produced favorable results; approximately 1 neurologic deficit saved for every 20 uses of adjunct overall. In extent II aneurysms, where the effect is greatest, this increases to 1 saved per 5 uses. Adjunct is also associated with long-term survival, which is consistent with mitigation of ischemic end-organ injury. These long-term results indicate that cerebrospinal fluid drainage and distal aortic perfusion are safe and effective adjunct for reducing morbidity and mortality following thoracic and thoracoabdominal aortic repair.

Descending thoracic aortic aneurysm: Surgical approach and treatment using the adjuncts cerebrospinal fluid drainage and distal aortic perfusion

BACKGROUND Neurologic deficit (paraplegia or paraparesis) remains a significant morbidity in the repair of descending thoracic aortic aneurysm. METHODS Between February 1991 and February 2000, we operated on 182 patients for descending thoracic aortic aneurysm. For the purpose of this study-to identify the impact of the combined adjuncts distal aortic perfusion and cerebrospinal fluid (CSF) drainage on neurologic outcome-we selected the 148 of 182 nonemergent patients who had received conventional treatment (simple cross-clamping with or without adjuncts). The mean patient age was 61 years, and 49 of the 148 (33%) patients were women. Nine of the 148 patients (6%) had acute type B dissections. We compared the results of 105 of the 148 patients (71%) who received the combined adjuncts of CSF drainage and distal aortic perfusion with the remaining 43 (29%) patients who underwent repair using the simple cross-clamp with or without the addition of a single adjunct. RESULTS Overall 30-day mortality was 13 of 148 patients (8.8%). Overall early neurologic deficit was 4 of 148 (2.7%): 1 of 105 (0.9%) patients who had received distal aortic perfusion and CSF drainage, versus 3 of 43 (7%) in all other patients (p < 0.04). CONCLUSIONS In our practice the use of the combined adjuncts of CSF drainage and distal aortic perfusion has all but eliminated the incidence of immediate postoperative neurologic deficit in nonemergent patients with aneurysms of the descending thoracic aorta.

Neurologic outcome after thoracic and thoracoabdominal aortic aneurysm repair

BACKGROUND Neurologic deficit (paraparesis and paraplegia) after repair of the thoracic and thoracoabdominal aorta remains a devastating complication. The purpose of this study was to determine the effect of cerebrospinal fluid drainage and distal aortic perfusion upon neurologic outcome during repair of thoracic and thoracoabdominal aortic aneurysm (TAAA) repair. METHODS Between February 1991 and March 2000, we performed 654 repairs of the thoracic and thoracoabdominal aorta. The median age was 67 years and 420 (64%) patients were male. Forty-five cases (6.9%) were performed emergently. Distribution of TAAA was the following: extent I, 164 (25%); extent II, 165 (25%); extent III, 61 (9%); extent IV, 95 (15%); extent V, 23 (3.5%); and descending thoracic, 147 (22%). The adjuncts cerebrospinal fluid drainage and distal aortic perfusion were used in 428 cases (65%). RESULTS Thirty-day mortality was 14% (94 of 654). The in-hospital mortality was 16% (106 of 654). Early neurologic deficits occurred in 33 patients (5.0%). Overall, 14 of 428 (3.3%) neurologic deficits were observed in the adjunct group, and 19 of 226 (8.4%) in the nonadjunct group (p = 0.004). When the adjuncts were used during extent II repair, the incidence was 10 of 129 (7.8%) compared with 11 of 36 (30.6%) in the nonadjunct group (p < 0.001). Multivariate analysis demonstrated that risk factors for neurologic deficit were cerebrovascular disease and extent of TAAA (II and III) (p < 0.05). CONCLUSIONS The combined adjuncts of distal aortic perfusion and cerebrospinal fluid drainage demonstrated improved neurologic outcome with repair of thoracic and TAAAs. In extent II aneurysms, adjuncts continue to make a considerable difference in the outcome and to provide significant protection against spinal cord morbidity. Future research should focus on spinal cord protection in patients with high-risk extent II aneurysms.

Preoperative and operative predictors of delayed neurologic deficit following repair of thoracoabdominal aortic aneurysm

Abstract Purpose Delayed neurologic deficit has been recognized in recent years as a source of morbidity following thoracic and thoracoabdominal aortic repair. We wanted to find risk factors specifically significant for delayed neurologic deficit. In this initial study we looked at preoperative and operative risk factors. Methods We performed 854 thoracoabdominal aortic repairs between February 1991 and May 2001. For this study we excluded 26 patients who died before postoperative neurologic status could be evaluated and 38 who had immediate neurologic deficit on initial postoperative evaluation, leaving 790 consecutive patients. We evaluated a wide range of demographic, preoperative physiological and intraoperative data, using univariate and multivariable statistical analyses. Results Twenty-one of 790 (2.7%) patients had delayed neurologic deficit. Significant univariate predictors included preoperative renal dysfunction (odds ratio 5.9; P P P P Conclusion Preoperative renal dysfunction, acute dissection, and extent II thoracoabdominal aorta are significant predictors of delayed neurologic deficit. Previous studies have demonstrated that the use of adjuncts protects against immediate neurologic deficit. The findings of this study are consistent with the hypothesis that adjuncts reduce ischemic insult enough to prevent immediate neurologic deficit but that a period of increased spinal cord vulnerability persists several days postoperatively.

Staged repair of extensive aortic aneurysms

BACKGROUND We adopted a two-stage approach (elephant trunk procedure) in the repair of extensive aortic aneurysms in 1991, performing 241 procedures in 155 patients. METHODS Reversed elephant trunk (graft replacement of the descending thoracic aorta followed by ascending/arch replacement) was performed in 18 patients. All other patients underwent conventional staged repair. The first stage was performed in 137 patients, with 86 patients returning for the second stage. RESULTS First stage 30-day mortality was 9.5% (13 of 137). There was no second stage immediate neurologic deficit. Second stage mortality was 7.0% (6 of 86). During the interval of 31 days to 6 weeks after stage one, mortality was 10 of 124 (8%). Seven of the 10 interval deaths (70%) were due to rupture of the untreated aortic segment. The mortality rate was 32.1% (18 of 56) in the group of patients who did not return for the second stage repair. CONCLUSIONS Extensive aortic aneurysms can be repaired with acceptable morbidity and mortality using the elephant trunk technique. After stage one, prompt treatment of the remaining aneurysm is crucial to success.

Staged repair of extensive aortic aneurysms: long-term experience with the elephant trunk technique.

Objective:This paper reports our experience of a large series of elephant trunk patients accumulated over 12 years. Summary Background Data:Extensive aneurysms of the ascending/arch and descending thoracic or thoracoabdominal aorta are significant surgical problems that have potential for great morbidity. We adopted a staged approach known as the elephant trunk procedure in 1991, and we have used it with some modifications since that time. Methods:Between February 1991 and December 2003, we performed 1660 operations for ascending/arch or descending thoracic/thoracoabdominal aortic aneurysms. Of these, 321 operations were performed in 218 patients for extensive aneurysms with the elephant trunk technique. We performed 218 ascending/arch repairs and 103 descending thoracic or thoracoabdominal aortic replacements. Results:In 218 ascending/arch repairs, strokes occurred in 3 of 218 (2.7%) patients, with 1 of 187 (0.5%) in the retrograde cerebral perfusion group and 2 of 31 (6.5%) in the no-retrograde cerebral perfusion group (odds ratio 0.08, P < 0.009). Thirty-day mortality for this group was 19 of 218 (8.7%). Among 199 recovering patients after stage 1 repair, 4 of 199 (2%) died during the 30-day to 6-week interval between stages. After stage 2 repair, 0 of 103 patients experienced immediate neurologic deficit, and 10 of 103 (9.7%) died within 30 days of surgery. Actuarial survival after completed stage 2 was 71% at 5 years. Conclusion:Despite extreme underlying disease, long-term survival is excellent in patients with extensive aneurysms when both stages of repair are completed. To prevent rupture, the second stage should be completed as soon as the patients condition permits, preferably within 6 weeks.

VASCULAR ENDOTHELIAL GROWTH FACTOR RESTORES CORPOREAL SMOOTH MUSCLE FUNCTION IN VITRO

PURPOSE The therapeutic use of vasculogenic growth factors has been successfully demonstrated in models of organ ischemia. We determined whether vascular endothelial growth factor (VEGF) would reverse corporeal smooth muscle dysfunction in the hypercholesterolemic rabbit model of erectile dysfunction. MATERIALS AND METHODS A total of 36 New Zealand White rabbits were fed a normal (12) or 1% cholesterol (24) diet and treated after 6 weeks with 0.9 mg. VEGF or vehicle. At 6 weeks 24 rabbits received a single intracavernous dose and 12 received a single intravenous bolus of either drug. Ten days after injection corporeal smooth muscle function was analyzed after relaxation to acetylcholine and sodium nitroprusside using isometric tension studies. Corporeal sections were assessed for smooth muscle content with f-actin staining and VEGF expression by immunohistochemical study and enzyme-linked immunosorbent assay. RESULTS Endothelium dependent (acetylcholine) and nitric oxide mediated (sodium nitroprusside) smooth muscle relaxation were impaired in cholesterol fed animals (p = 0.021 and 0.003, respectively). Intracavernous VEGF treatment restored sodium nitroprusside mediated relaxation to normal (p = 0.015) and intravenous VEGF restored acetylcholine and sodium nitroprusside mediated relaxation (p = 0.014 and 0.018, respectively). Decreased smooth muscle content was noted in cholesterol fed animals versus normal diet controls (p = 0.008), which was not affected by VEGF treatment (p = 0.450). Corporeal endothelial cell content was increased after intracavernous but not intravenous VEGF treatment (p = 0.001 and 0.385, respectively). VEGF expression was augmented after treatment with recombinant VEGF (p <0.001). CONCLUSIONS VEGF administration variably mitigated the impairment of corporeal smooth muscle relaxation in the hypercholesterolemic rabbit model of erectile dysfunction.

Replacement of the ascending and transverse aortic arch: determinants of long-term survival.

BACKGROUND Although little has been published on the natural history of aneurysms of the ascending aorta and aortic arch, long-term prognosis of untreated aneurysms is generally poor. We reviewed our 10-year experience in the repair of the ascending aorta and aortic arch to evaluate long-term outcome. METHODS Between January 1991 and May 2001, we repaired 423 aneurysms of the ascending aorta or aortic arch using profound hypothermic circulatory arrest. Median age was 65 years. Retrograde cerebral perfusion (RCP) was used in 357 cases. Mean pump and RCP times were 139 and 33.9 minutes, respectively. Survival was ascertained by direct patient contact or by searching the social security death index. Survival was analyzed by Kaplan-Meier stratified analysis and by multivariate Cox regression. RESULTS Overall actuarial survival was 72% at 5 years and 71% at 10 years after surgery. Univariate analysis identified increasing age (p < 0.0001), chronic obstructive pulmonary disease (p < 0.014), concurrent unoperated aneurysm (p < 0.005), arch involvement (p < 0.042), pump time (p < 0.0004), concurrent aortic valve replacement (p < 0.009), and postoperative renal failure (p < 0.0002) as factors that negatively influenced survival. Multivariate analysis identified increasing age (p < 0.0001) and pump time (p < 0.0001). RCP did not have a significant independent effect on the long-term survival. CONCLUSIONS Our experience indicates that repair of the ascending aorta and aortic arch can be accomplished with good long-term survival.

Determination of cerebral blood flow dynamics during retrograde cerebral perfusion using power M-mode transcranial Doppler

BACKGROUND Retrograde cerebral perfusion (RCP) during profound hypothermic circulatory arrest has been used as an adjunct for cerebral protection for repairs of the ascending and transverse aortic arch. Transcranial Doppler ultrasound has been used to monitor cerebral blood flow during RCP with varying success. The purpose of this study was to characterize cerebral blood flow dynamics during RCP using a new mode of monitoring known as transcranial power motion-mode (M-mode) Doppler ultrasound. METHODS Data on pump-flow characteristics and patient outcomes were collected prospectively for patients undergoing ascending and transverse aortic arch repair. Retrograde cerebral perfusion during profound hypothermic circulatory arrest was used for all operations. Intraoperative cerebral blood flow dynamics were monitored and recorded using transcranial power M-mode Doppler ultrasound. RESULTS Between August 2001 and March 2002, we used transcranial power M-mode Doppler ultrasound monitoring for 40 ascending and transverse aortic arch repairs during RCP. Mean RCP time was 32.2 +/- 13.8 minutes. Mean RCP pump flow and RCP peak pressure for identification of cerebral blood flow were 0.66 +/- 0.11 L/min and 31.8 +/- 9.7 mm Hg, respectively. Retrograde cerebral blood flow during RCP was detected in 97.5% of cases (39 of 40 patients) with a mean transcranial power M-mode Doppler ultrasound flow velocity of 15.5 +/- 12.3 cm/s. In the study group, 30-day mortality was 10.0% (4 of 40 patients). The incidence of stroke was 7.6% (3 of 40 patients); the incidence of temporary neurologic deficit was 35.0% (14 of 40 patients). CONCLUSIONS Transcranial power M-mode Doppler ultrasound consistently demonstrated retrograde middle cerebral artery blood flow during RCP. Transcranial power M-mode Doppler ultrasound can provide optimal RCP with individualized settings of pump flow.