Haem oxygenase-1 plays a central role in NNK-mediated lung carcinogenesis

The tobacco-specific nitrosamine, 4-(N-methyl-N-nitrosoamino)-1-(3-pyridyl)-1-butanone (NNK), is a potent lung cancer inducer. However, how NNK induces lung cancer is still largely unknown. Haem oxygenase (HO)-1 was evaluated in 30 pairs of lung cancer tumour samples and matched nontumour tissues from patients with a history of cigarette smoking. Expression of HO-1, p21(Cip1/Waf1/Cid1) (p21), B-cell lymphoma (Bcl)-2 family members, mitogen-activated protein kinase and nuclear factor (NF)-kappaB was also studied in lung cancer cells treated with NNK. The levels of HO-1 and p21 were significantly increased in lung tumour tissues. There was a positive relationship between these two proteins in the tumour. NNK stimulated lung cell proliferation and elevated the levels of HO-1, p21, inhibitor of apoptosis protein (c-IAP)2 and Bcl-2, but downregulated Bad. These effects of NNK were blocked by zinc protoporphyrin-XII, an HO-1 inhibitor. The NNK-mediated expression of HO-1 was governed by NF-kappaB and extracellular signal-regulated kinase 1/2, since blocking either of these prevented the stimulatory effect of NNK on HO-1, as well as molecules downstream of HO-1, such as p21, c-IAP2, Bcl-2 and Bad. In conclusion, haem oxygenase-1 plays a central role in NNK-mediated cell proliferation by promoting the expression of p21(Cip1/Waf1/Cid1), inhibitor of apoptosis protein 2 and B-cell lymphoma-2 but inhibiting the activity of Bad. Nuclear factor-kappaB and extracellular signal-regulated kinase 1/2 function upstream of haem oxygenase-1. Therefore, haem oxygenase-1 is likely to be a potential target in the treatment of smoking-related lung cancer.

Repair of aortic valve prolapse: experience with 44 patients*1

OBJECTIVES

In regurgitant tricuspid aortic valves, cusp prolapse may be isolated or associated with dilatation of the proximal aorta. Newly appearing cusp prolapse can also appear after an aortic valve sparing operation (AVSO) and be responsible for residual aortic regurgitation. In this report, we describe our experience in repairing prolapsing aortic cusps in 44 patients with aortic regurgitation.

METHODS

Between 1996 and 2003, 260 patients had aortic valve repair or valve sparing procedures in our department. All patients had peri-operative TEE. Prolapse of one or more of the aortic cusps was identified by TEE and confirmed by careful surgical inspection before and after valve sparing surgery. Forty-four patients with cusp prolapse were identified. Fifteen had an isolated prolapse, with a normal root (group I), 18 had cusp prolapse associated with dilatation of the proximal aorta (group IIa), and 11 had a newly appearing prolapse after AVSO (group IIb). Correction of the prolapsing cusp was achieved by either free edge plication, triangular resection or resuspension with PTFE. This procedure was associated with an aortic annuloplasty in group I, and with AVSO in groups II and III.

RESULTS

Post-operative TEE showed AR trivial or grade I regurgitation. At a mean of 23 months follow-up, one patient with recurrent regurgitation required an aortic valve replacement with a homograft. All remaining patients were in NYHA class I or II. Echocardiography confirmed the durability of the valve repair.

CONCLUSIONS

Among the common causes of aortic regurgitation, isolated cusp prolapse is frequent and is amenable to surgical repair with excellent mid-term results. In particular, in patents who are potential candidates for AVSO, identification and correction of an associated prolapse, either pre-existing or secondary to the AVSO procedure, may further extend the indications for this technique, increase its success rates and improve its long-term outcome.

Clinical and angiographic outcome of different surgical strategies of bilateral internal mammary artery grafting

Long-term survival, relief of angina, and prevention of myocardial infarction after coronary revascularization are related to the preoperative status of the patient, progression of coronary artery atherosclerosis, and the patency of the conduits used. The increased use of the internal mammary artery for coronary grafting depends upon the accumulation of data on superior late patency compared with venous conduits. These data have supported the simultaneous use of both left and right internal mammary arteries with reported improved late survival. However, controversy still surrounds the clinical and angiographic outcomes of some of the surgical strategies of bilateral internal mammary artery grafting. This review examines a range of surgical strategies of bilateral internal mammary artery grafting and their mid- and long-term clinical and angiographic outcomes. From the available data, careful preoperative selection of patients is paramount. Clinical and angiographic outcome of bilateral internal mammary grafting is superior to single internal mammary grafting with supplemental vein grafts when pedicled, sequential, or free aorto-coronary internal mammary artery is used. Further studies are needed to evaluate the midterm and long-term clinical and angiographic outcomes of complex strategies such as Y or T procedures.

Off-pump coronary operations can be safely taught to cardiothoracic trainees

BACKGROUND

Off-pump coronary artery bypass (OPCAB) operations are evolving rapidly and becoming established in many cardiothoracic centers. For the technique to be widely applicable, teaching methods must be developed for surgical trainees. Early and midterm clinical outcomes of OPCAB performed at our institution by trainees as first operators under supervision were compared to those obtained in patients operated on by consultants.

METHODS

Analysis was undertaken on data prospectively inserted in the Patient Analysis & Tracking System. Of the 559 OPCAB operations performed between January 1997 and May 2000, 124 (22%) were carried out by a supervised trainee and 435 (78%) by a consultant.

RESULTS

There was no difference in age, sex, angina class, New York Heart Association functional class, or operative priority and extent of coronary artery disease in the two groups. More patients operated on by consultants had a history of congestive heart failure requiring medical therapy, significantly lower ejection fraction, and higher Parsonnet score compared with patients operated on by trainees. Early and midterm clinical results, in terms of morbidity and mortality, were similar in patients operated on by trainees or by consultants.

CONCLUSIONS

Our data show no differences in early and midterm clinical outcome for patients undergoing OPCAB operations performed either by consultants or by trainees under supervision. The improvements in exposure and stabilization techniques, as well as the use of intracoronary shunts, have made it possible and safe to teach trainees off-pump multivessel coronary artery revascularization.

Prevention of spinal cord ischaemia during descending thoracic and thoracoabdominal aortic surgery

Surgery of the descending and thoracoabdominal aorta has been associated with post-operative paraparesis or paraplegia. Different strategies, which can be operative or non-operative, have been developed to minimise the incidence of neurological complications after aortic surgery. This review serves to summarise the current practice of spinal cord protection during surgery of the descending thoracoabdominal aortic surgery. The pathophysiology of spinal cord ischaemia will also be explained. The incidence of spinal cord ischaemia and subsequent neurological complications was associated with (1) the duration and severity of ischaemia, (2) failure to establish spinal cord supply and (3) reperfusion injury. The blood supply of the spinal cord has been extensively studied and the significance of the artery of Adamkiewicz (ASA) being recognised. This helps us to understand the pathophysiology of spinal cord ischaemia during descending and thoracoabdominal aortic operation. Techniques of monitoring of spinal cord function using evoked potential have been developed. Preoperative identification of ASA facilitates the identification of critical intercostal vessels for reimplantation, resulting in re-establishment of spinal cord blood flow. Different surgical techniques have been developed to reduce the duration of ischaemia and this includes the latest transluminal techniques. Severity of ischaemia can be minimised by the use of CSF drainage, hypothermia, partial bypass and the use of adjunctive pharmacological therapy. Reperfusion injury can be reduced with the use of anti-oxidant therapy. The aetiology of neurological complications after descending and thoracoabdominal aortic surgery has been well described and attempts have been made to minimise this incidence based on our knowledge of the pathophysiology of spinal cord ischaemia. However, our understanding of the development and prevention of these complications require further investigation in the clinical setting before surgery on descending and thoracoabdominal aorta to be performed with negligible occurrence of these disabling neurological problems.

Reconstruction of the ascending aorta and aortic root: experience in 45 consecutive patients

BACKGROUND

Patients with aneurysms of the ascending aorta or aortic root may have associated aortic insufficiency (AI). We reviewed our experience with aortic root remodeling and reconstruction of the sino-tubular junction.

METHODS

Forty-five patients were operated on between July 1995 and September 1998. Transesophageal echocardiography showed AI grade III or IV in 15 patients. Twenty-seven patients had replacement of all three sinuses, 10 of one or two sinuses. Reconstruction of the sino-tubular junction alone was performed in 8 patients.

RESULTS

There was one death at 28 days. Perioperative transesophageal echocardiography showed no or discrete AI in all patients. There has been one aortic valve replacement at day 4 postoperatively for cusp repair failure. Transesophageal echocardiography in 40 patients at a mean time of 12.5 months showed no progression of AI in 38 patients, and a grade II in 2. Clinical follow-up averaged 14.5 months. There have been three late, not procedure-related deaths. Thirty-six patients are in New York Heart Association functional class I. There have been no cases of endocarditis.

CONCLUSIONS

Aortic remodeling is successful in eliminating AI in patients with aortic root disease with minimal mortality and morbidity. Early echocardiography (1 year) has shown no progression of AI in 95% of cases.

Predictors of atrial fibrillation after conventional and beating heart coronary surgery: A prospective, randomized study

BACKGROUND

Atrial fibrillation (AF) increases the morbidity of CABG. The pathophysiology is uncertain, and its prevention remains suboptimal. This prospective, randomized study was designed to define the role of cardiopulmonary bypass (CPB) and cardioplegic arrest in the pathogenesis of this complication.

METHODS AND RESULTS

Two hundred patients were prospectively randomized to (1) on-pump conventional surgery [(100 patients, 79 men, mean age 63 (40 to 77) years)] with normothermic CPB and cardioplegic arrest of the heart or (2) off-pump surgery [(100 patients, 82 men, mean age 63 (38 to 86) years)] on the beating heart. Heart rate and rhythm were continuously monitored with an automated arrhythmia detector during the first 72 hours after surgery. Thereafter, routine clinical observation was performed and continuous monitoring restarted in the case of arrhythmia. The association of perioperative factors with AF was investigated by univariate analysis. Significant variables were then included into a stepwise logistic regression model to ascertain their independent influence on the occurrence of AF. There were no significant baseline differences between groups. Thirty-nine patients in the on-pump group and 8 patients in the off-pump group had postoperative sustained AF (P:=0.001). Univariate analysis showed that CPB inclusive of cardioplegic arrest, postoperative inotropic support, intubation time, chest infection, and hospital length of stay were predictors of AF (all P:<0.05). However, stepwise multivariate regression analysis identified CPB inclusive of cardioplegic arrest as the only independent predictor of postoperative AF (OR 7.4; CI 3.4 to 17.9).

CONCLUSIONS

CPB inclusive of cardioplegic arrest is the main independent predictor of postoperative AF in patients undergoing coronary revascularization.

Inflammatory response after coronary revascularization with or without cardiopulmonary bypass

BACKGROUND

We sought to investigate the effect of multiple coronary artery bypass grafting (CABG) with or without cardiopulmonary bypass (CPB) on the perioperative inflammatory response.

METHODS

Sixty patients undergoing CABG were randomly assigned to one of two groups: (A) on pump with conventional CPB and cardioplegic arrest, and (B) off pump on the beating heart. Serum samples were collected for estimation of neutrophil elastase, interleukin 8 (IL-8), C3a, and C5a preoperatively and at 1, 4, 12, and 24 hours postoperatively. Furthermore, white blood cell (WBC), neutrophil, and monocyte counts were carried out preoperatively and at 1, 12, 36 and 60 hours postoperatively. Overall incidence of infection and perioperative clinical outcome were also recorded.

RESULTS

The groups were similar in terms of age, weight, gender ratio, extent of coronary disease, left ventricular function, and number of grafts per patient. Neutrophil elastase concentration peaked early after CPB in the on-pump group, with a decline with time. Repeated-measures analysis of variance between groups and comparisons at each time point (modified Bonferroni) showed elastase concentrations were significantly higher in the on-pump than the off-pump group (both p < 0.0001). IL-8 increased significantly after surgery in the on-pump group, with no decline during the observation period (p = 0.01 vs off pump). C3a and C5a rose early after surgery in both groups when compared with baseline values. Postoperative WBC, neutrophil, and monocyte counts were significantly higher in the on-pump than the off-pump group (p < 0.01). Finally, the incidence of postoperative overall infections was significantly higher in the on-pump group (p < 0.0001 vs off pump).

CONCLUSIONS

CABG on the beating heart is associated with a significant reduction in inflammatory response and postoperative infection when compared with conventional revascularization with CPB and cardioplegic arrest.

Serum S-100 protein release and neuropsychologic outcome during coronary revascularization on the beating heart: a prospective randomized study

OBJECTIVES

Our purpose was to establish whether coronary revascularization on the beating heart without cardiopulmonary bypass is less harmful to the brain than conventional surgery with cardiopulmonary bypass as indicated by measures of cognitive function or by changes in serum concentrations of S-100 protein, a recognized biochemical marker of cerebral injury.

METHODS

We conducted a prospective randomized trial in which the assessors of the outcome measures were blind to the treatment received. Sixty patients without known neurologic abnormality, undergoing coronary revascularization, were prospectively randomized to 1 of 2 groups: (1) cardiopulmonary bypass (32 degrees C-34 degrees C) and cardioplegic arrest (on pump) with intermittent antegrade warm blood cardioplegia or (2) surgery on the beating heart (off pump). Neuropsychologic performance was assessed before and 12 weeks after the operation. Serum S-100 protein concentration was measured at intervals up to 24 hours after the operation.

RESULTS

The groups had similar preoperative characteristics. There were no deaths or major neurologic complications in either group, nor was there any difference between groups in the chosen index of neurologic deterioration. Serum S-100 protein concentrations were higher in the on-pump group at 30 minutes, but any such difference between groups had disappeared 4 hours later. The extent of the changes in S-100 protein was unrelated to the index of neuropsychologic deterioration.

CONCLUSIONS

The changes in S-100 protein concentration suggest that the brain and/or blood-brain barrier may be more adversely affected during coronary artery surgery with cardiopulmonary bypass than during surgery on the beating heart, but that this may not be reflected in detectable neuropsychologic deterioration at 12 weeks.

Economic outcome of off-pump coronary artery bypass surgery: a prospective randomized study

BACKGROUND

Emphasis on cost containment in coronary artery bypass surgery is becoming increasingly important in modern hospital management. The revival of interest in off-pump (beating heart) coronary artery bypass surgery may influence the economic outcome. This study examines these effects.

METHODS

Two hundred patients undergoing first-time coronary artery bypass surgery were prospectively randomized to either conventional cardiopulmonary bypass and cardioplegic arrest or off-pump surgery. Variable and fixed direct costs were obtained for each group during operative and postoperative care. The data were analyzed using parametric methods.

RESULTS

There was no difference between the groups with respect to pre- and intraoperative patient variables. Off-pump surgery was significantly less costly than conventional on-pump surgery with respect to operating materials, bed occupancy, and transfusion requirements (total mean cost per patient: on pump, $3,731.6+/-1,169.7 vs off-pump, $2,615.13+/-953.6; p < 0.001). Morbidity was significantly higher in the on-pump group, which was reflected in an increased cost.

CONCLUSIONS

Off-pump revascularization offers a safe, cost-effective alternative to conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest.

On-pump versus off-pump coronary revascularization: evaluation of renal function

BACKGROUND

Coronary revascularization with cardiopulmonary bypass has the potential risk of renal dysfunction related to the nonphysiologic nature of cardiopulmonary bypass. Recently, there has been a revival of interest in performing myocardial revascularization on the beating heart and we investigated whether this prevents renal compromise.

METHODS

A prospective, randomized, controlled trial was performed in 50 patients (45 males, mean age 61+/-3.7 years) undergoing elective coronary artery bypass grafting. Patients were randomly assigned to conventional revascularization with cardiopulmonary bypass (on pump) or beating heart revascularization (off pump). Glomerular and tubular function were assessed up to 48 hours postoperatively.

RESULTS

There were no deaths, myocardial infarctions or acute renal failure in either group. Glomerular filtration as assessed by creatinine clearance and the urinary microalbumin/creatinine ratio was significantly worse in the on pump group (p < 0.0004 and 0.0083, respectively). Renal tubular function was also impaired in the on pump group as assessed by increased N-acetyl glucosaminidase activity (p < 0.0272).

CONCLUSIONS

These results suggest that off pump coronary revascularization offers a superior renal protection when compared with conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest in first time coronary bypass patients.

Recycling of arterial grafts during reoperative coronary artery operations

BACKGROUND

To overcome problems of lack of conduit and to maximize the number of arterial anastomoses in coronary reoperations we reused previously placed arterial grafts.

METHODS

Sixteen patients were identified from February 1994 to July 1997. Mean age was 62.8 years (range, 44 to 75 years). Fifteen (94%) were in Canadian Cardiovascular Society angina class III or IV. The mean interval from primary to secondary operation was 8.5 years (range, 3 to 12 years). Eleven patients had a patent internal mammary artery graft used as the recipient for a proximal Y anastomosis. In 3 cases an arterial graft was reimplanted distally on the same coronary vessel and in 2 onto different coronary vessels. One patient had a combination of these techniques. Five patients required venous conduit.

RESULTS

There were no deaths. Mean length of intensive care stay was 69 hours (range, 24 to 144) and mean hospital stay was 14 days (range, 10 to 28 days). All patients were discharged home. Follow-up averages 13 months (range, 2 to 43 months). Twelve patients (75%) are now in Canadian Cardiovascular Society angina class I and 3 (19%) in class II.

CONCLUSIONS

Reusing arterial conduits during coronary reoperations is possible with minimal in-hospital morbidity and satisfactory results in terms of freedom from angina. Using these techniques can help overcome the problems of inadequate conduit and maximize the number of arterial anastomoses that can be made per patient.

Biomaterials and cardiovascular devices

In the field of cardiovascular surgery there is presently a lack of biomaterials possessing essential characteristics of the native tissue or organ which is to be replaced. This paper describes various biomaterials that have been introduced into the circulatory system and the complex reactions that subsequently occur. The risk of infection is also discussed as well as prevention and treatment regimes that can be used. Examples of future biomaterial development are outlined in an attempt to achieve biocompatibility.

Use of the right gastroepiploic artery as a coronary artery bypass graft in 307 patients

From October 1988 to October 1995 the right gastroepiploic artery was used as a conduit for coronary surgery in 307 patients. Their average age was 56.5 years (range 25-75) and 274 patients (89%) were male. Twenty-six cases (8.5%) were re-operations and 58 patients (19%) were operated upon on an urgent or semi-urgent basis. Target coronary vessels were the right coronary artery and its branches in 280 cases (91.4%), the circumflex artery in 25 cases (8%) and the left anterior descending artery in two cases. The right gastroepiploic artery was used as an in situ graft in 303 cases (98.7%) and as a free graft in 4 (1.3%). A total of 291 patients (94.8%) also received at least one mammary artery graft: both mammary arteries were used in 167 patients (54.4%). An average of 3.6 distal anastomoses were made per patient, three of them with arterial grafts. Eleven (3.2%) right gastroepiploic artery grafts were doubled with saphenous vein intraoperatively because of persistent myocardial ischemia. In-hospital mortality was 1.6% (five patients). Perioperative myocardial infarction occurred in twelve patients (3.9%). Follow-up now averages 26 months (range 6-88). There have been five late deaths (1.6%). A total of 265 (89.2%) patients are angina free. Of the total, 145 patients have been investigated with a maximal-stress test coupled with scintigraphy: residual myocardial ischemia was found in 10 patients, right gastroepiploic artery was related in three. Ninety-six patients have undergone angiographic restudy at a mean of 12 months (range 8-88) postoperatively. Patency of the right gastroepiploic artery grafts was 91.8%. This study confirms that the right gastroepiploic artery can be used as a conduit for coronary artery bypass surgery with minimal mortality or morbidity. Mid-term patency rates and clinical outcome are encouraging.

The lima success story--whither other arterial grafts--are vein grafts obsolete?

The long-term benefit of myocardial revascularisation depends largely upon the continued patency of bypass grafts, but the long-term patency of vein grafts is poor. To improve the results of myocardial revascularisation, either measures to increase the patency of saphenous vein grafts or alternative conduits are required. Use of the left internal mammary artery as a graft is known to increase survival, and this has prompted wider use of other arterial grafts in the expectation that they will further enhance the long-term results of coronary artery bypass. This policy is based upon sound theory, but convincing evidence that it improves survival is lacking. Meanwhile, advances in the understanding of the pathology of vein graft occlusion have given rise to new methods of increasing vein graft patency. While these techniques are, as yet, only experimental, if translated into clinical practice, the places of arterial and venous grafts may require further assessment.

Arterial and venous conduits for coronary artery bypass. A current review

Poor long-term patency of saphenous vein grafts limits the long-term success of the coronary artery bypass operation. If this is to be improved, either measures that increase the patency of saphenous vein grafts or alternative conduits are required. The benefits of using the left internal mammary artery as a pedicled graft to the left anterior descending coronary artery have prompted increasing use of arterial grafts to further improve outcome. Concurrently advances in the understanding of the pathological processes underlying saphenous vein graft occlusion raise the possibility of improving vein graft patency. In this paper we review the problem of vein graft occlusion and possible solutions, the theoretical benefits of arterial grafts and the clinical results associated with their use.

The cerebral function monitor (CFM) is a useful addition to a bilateral carotid artery, vein graft model

Following human coronary artery bypass surgery, vein graft occlusion is a major cause of morbidity and mortality. An agent is required which will reduce the incidence of early graft thrombosis without causing systemic bleeding. To assess the efficacy of such agents a suitable experimental vein-graft model is required. A porcine, unilateral saphenous vein-carotid artery bypass graft model has been described previously, although to assess the effect of locally applied anticoagulant drugs, insertion of grafts bilaterally would be advantageous, allowing treated and control grafts to be implanted in the same animal which would then act as its own control. Pigs are reported as having an excellent collateral cerebral circulation and hence in theory, would be suitable animals to use as a bilateral carotid vein-graft model. This paper describes the occurrence of serious neurological complications during the development of such a model and suggests that by using a cerebral function monitor, detection of critical reductions in cerebral perfusion can be made early and remedial action take.

Changes in "inflammatory" mediators and total body water during extra-corporeal membrane oxygenation (ECMO). A preliminary study

We studied six patients (5 paediatric, 1 neonate) treated with ECMO to quantify changes in inflammatory mediators (neutrophil elastase (NE), free radical activity (FR), interleukin 8 (IL8)) and total body water (TBW). Blood samples were taken before instigation of ECMO, 4, 12, 24 hours post-ECMO and daily for six days. FR activity was quantified using the oxidised IgG FI/UV ration. NE and IL8 levels were measured by ELISA. TBW was assessed by electrical bioimpedance. Statistical analysis was made using repeated measures analysis of variance and modified t-test where appropriate. Results are presented as mean +/- standard error of the mean. FR activity increased 4 hours after instigation of ECMO (IgG FI/UV 32.1 +/- 3.2 from 24.1 +/- 3.0 p = 0.005) and remained elevated. NE also increased by 4 hours (94.8 micrograms/L +/- 8.9 to 678 micrograms/L +/- 153.4, p = 0.005) but returned to pre-ECMO values by day 6. IL8 levels rose after ECMO (from 98 pg/ml +/- 39, to 24 pg/ml +/- 117.4) although no statistical difference was noted over time due to the large variation between subjects (p = 0.009). TBW (% pre-ECMO body weight) fell by 24 hours (from 118.6 +/- 12.6 to 96.5 +/- 8.2 p = 0.0004). This study demonstrated that ECMO stimulates an 'inflammatory' response to extracorporeal perfusion (increased FR, NE) but despite this, results in a reduction in total body water. The complex relationship between the inflammatory response to prolonged extracorporeal perfusion and its effect on tissue oedema merits further investigation.

Quality of life following infragenicular bypass and lower limb amputation

AIMS

To objectively assess the quality of life after femorodistal bypass and compare this to quality of life achieved following primary limb amputation.

DESIGN

Retrospective review.

SETTING

Leicester Royal Infirmary, U.K., 1988-1993.

METHODS

A self-assessment postal questionnaire containing scales measuring emotional disorder, social functioning and mobility was sent to 112 patients who had previously undergone femorodistal bypass (n = 86) or primary limb amputation (n = 26).

RESULTS

Further analysis demonstrated that a secondary procedure (PTA or graft revision) to maintain graft patency did not adversely affect quality of life. Additionally, patients undergoing secondary amputation after graft failure had an identical quality of life to those undergoing primary amputation.

CONCLUSIONS

These data illustrate that the quality of life after successful femorodistal bypass is higher than after primary or secondary amputation. To attain the maximum quality of life in patients with critical ischaemia, femorodistal bypass should be performed wherever feasible.

Effect of intraluminal application of tissue-type plasminogen activator on the fibrinolytic activity of experimental vein grafts

OBJECTIVE

The aim was to quantify the effect of intraluminally applied tissue-type plasminogen activator (tPA) on the fibrinolytic activity of experimental vein grafts and assess the effect of pretreatment of the vein on early platelet and thrombus formation using histological techniques.

METHODS

A pig model of bilateral saphenous venin-carotid artery grafts was used. In each animal one side of the neck was grafted using vein distended to 230 mm Hg and pretreated with tPA (1 mg.ml-1) for a period of 15 min before grafting (treated graft). The perfused in situ for 2 h after implantation and before analysis. Changes in local fibrinolytic activity were quantified using fibrin plate techniques and specific chromogenic assays for tPA and urokinase (uPA) in tissue extract (n = 6 animals). Histological assessment was made using light and scanning microscopy (n = 4 animals).

RESULTS

Surgical preparation and distention significantly reduced the fibrinolytic activity of pig saphenous vein in terms of areas of lysis produced on fibrin plates (P < 0.05), tPA activity (P < 0.05), and uPA activity (P < 0.05). Pretreatment of distended vein with tPA before grafting significantly enhanced its fibrinolytic activity after 2 h perfusion compared to control (untreated) grafts, as assessed by areas of lysis on fibrin plates (P < 0.05) and specific tPA activity (P < 0.05). Treated grafts also showed qualitatively less platelet and thrombus formation on histological examination.

CONCLUSIONS

Pretreatment of surgically harvested vein by intraluminal application of tPA before grafting enhances its fibrinolytic activity after exposure to 2 h perfusion in vivo. This technique requires further investigation to validate its potential as a means of providing local anticoagulation to veins implanted as arterial grafts thereby reducing the incidence of early graft thrombosis.

Changes in vessel wall plasminogen activator activity and smooth muscle cell proliferation and activation after arterial injury

OBJECTIVES

The aim was to examine changes in vessel wall fibrinolytic activity following angioplasty and to assess any relationship to changes in smooth muscle cell proliferation and activation.

METHODS

Balloon angioplasty was performed to the iliac arteries of New Zealand White rabbits and vessel wall changes assessed at 2 h, 1 d, 7 d, 14 d, and 1 month postprocedure. Tissue-type (tPA) and urokinase-type (uPA) plasminogen activator activity was assessed using chromogenic substrate assays, while smooth muscle cell proliferation and activation was monitored using expression of proliferating cell nuclear antigen (PCNA) and of basic fibroblast growth factor (bFGF) respectively.

RESULTS

Intimal thickening progressively increased up to 1 month. uPA activity increased at 2 h [1.94(SEM 0.19) v 1.59(0.05) U.mg-1 tissue for control vessels, P = 0.03], remained increased at 24 h, but by 7 d had decreased to below control levels and remained low. In contrast, tPA activity fell significantly at 2 h [0.9(0.3) v 1.96(0.13) micrograms.mg-1 tissue for control vessels, P = 0.03], remained low at 24 h, but by 7 d had reverted back to control levels [2.19(0.39) micrograms.mg-1]. PCNA positivity of the media increased at day 1, reached maximum on day 7 [16.9(5.1)% positively staining cells] before returning to baseline by 1 month. PCNA positivity of the intima first evident at day 7 [0.7(0.3)%], reached a maximum at day 14 [4.1(0.4)%]. bFGF expression increased early at 2 h [mean(SE) positively staining cells: 15.7(5.3)% v 11.2(4.8)% for control vessels] and continued to increase, reaching a maximum in the media at day 7 [59(8.6)%] and in the intima at day 14 [57.5(5.7)%].

CONCLUSIONS

Balloon injury produced an initial fall in tPA and rise in uPA activity. tPA increased back to control levels by 7 d, while uPA fell to below control levels at 7 d and 1 month. This would be compatible with a mechanism whereby acute injury suppressed tPA and upregulated uPA activity, with increased tPA activity acting as a marker for vessel repair.