Statins in coronary bypass surgery: rationale and clinical use

Simvastatin exerts favourable effects on neointimal formation in a mouse model of vein graft

BACKGROUND

Simvastatin inhibits human saphenous vein neointima formation in human saphenous vein organ cultures. However, it is not known if simvastatin actually inhibits vein graft intima hyperplasia in vivo, and the underlying mechanisms behind that. In this study, we used a murine vein graft model to address these issues.

METHODS AND RESULTS

Vein grafting was performed among C57BL/6 J mice treated with low-dose (2 mg kg(-1)) or high-dose (20 mg kg(-1)) simvastatin or vehicle subcutaneously 72 h before and then daily after surgery. As compared to the vehicle, simvastatin dose-dependently significantly inhibited vein graft intima hyperplasia 4 weeks after surgeries. Immunohistochemistry studies suggested that vein graft neointima was mainly composed of vascular smooth muscle cells (VSMCs), and the rate of proliferating cell nuclear antigen (PCNA)-positive cells in the intima of vein grafts was significantly lower in simvastatin-treated groups than in control group. We isolated VSMC from mouse vena cava, simvastatin significantly reduced VSMC proliferation, and platelet-derived growth factor (PDGF)-induced VSMC migration in a dose-dependent manner.

CONCLUSION

Simvastatin inhibits neointima formation of mouse vein graft under normocholesterolaemic condition in vivo, the mechanisms might be associated with inhibitory effects of simvastatin on VSMC proliferation and migration.

Atorvastatin pretreatment diminishes the levels of myocardial ischemia markers early after CABG operation: an observational study

Background

Statin pretreatment has been associated with a decrease in myocardial ischemia markers after various procedures and cardiovascular events. This study examined the potential beneficial effects of preoperative atorvastatin treatment among patients undergoing on-pump CABG operation.

Methods

Twenty patients that had received atorvastatin treatment for at least 15 days prior to the operation and 20 patients who had not received any antihyperlipidemic agent prior to surgery were included in this study. CK-MB and troponin I levels were measured at baseline and 24 hours after the operation. Perioperative variables were also recorded.

Results

Twenty-four hours after the operation, troponin I and CK-MB levels were significantly lower in the atorvastatin group: for CK-MB levels, 12.9 ± 4.3 versus 18.7 ± 7.4 ng/ml, p = 0.004; for troponin I levels, 1.7 ± 0.3 versus 2.7 ± 0.7 ng/ml, p < 0.001. In addition, atorvastatin use was associated with a decrease in the duration of ICU stay.

Conclusions

Preoperative atorvastatin treatment results in significant reductions in the levels of myocardial injury markers early after on-pump CABG operation, suggesting a reduction in perioperative ischemia in this group of patients. Further studies are needed to elucidate the mechanisms of these potential benefits of statin pretreatment.

Effect of preoperative atorvastatin therapy on paraoxonase activity and oxidative stress after coronary artery bypass grafting

The aim of this study was to examine the influence of preoperative atorvastatin therapy on oxidative stress in coronary artery bypass grafting (CABG) patients. Forty patients who underwent elective CABG were enrolled into the study. Of these patients, 20 received atorvastatin (Group I) for 15 days prior to surgery and 20 patients did not use any antihyperlipidemic agents preoperatively (Group II). Serum paraoxonase 1 (PON1) and arylesterase activities, and total antioxidant status (TAS) and total oxidant status (TOS) were measured before surgery and at 1, 6 and 24 hours after the operation. Paraoxonase 1 and arylesterase activities (p<0.001) and TAS levels (p<0.001 for 1st hour and p<0.05 for 6th hour) in Group II were significantly reduced at the 1 st and 6th hours after the operation, whereas the activities of the enzymes (p<0.01) and TAS levels (p<0.05) were significantly reduced only at the 1st hour after the operation in Group I. The total oxidant status of both groups was significantly increased at the 1 st hour after operation (p<0.05 for Group I and p<0.01 for Group II). In conclusion, 15 days of preoperative atorvastatin therapy does not significantly change either the serum PON1 activity or the oxidative stress after CABG.

Perioperative statin therapy is associated with a significant and dose-dependent reduction of adverse cardiovascular outcomes after coronary artery bypass graft surgery

OBJECTIVE

The aim of this study was to determine whether perioperative statin therapy was associated with a dose-dependent decrease in adverse cardiovascular events after coronary artery bypass graft (CABG) surgery.

DESIGN

A prospective observational study.

SETTING

A cardiovascular anesthesia unit in a university hospital.

PARTICIPANTS

Four hundred eighteen consecutive patients undergoing CABG surgery between October 2004 and October 2005.

INTERVENTIONS

Patients were divided in 2 groups depending on whether their preoperative treatment included statins or not. In patients receiving statins, high- and low-dose regimens were respectively defined as a regimen recognized to induce a theoretic reduction of low-density lipoprotein cholesterol level equal to 45% (n = 87) or <45% (n = 258). In treated patients, statin therapy was maintained until the day of surgery and was restarted soon thereafter.

MEASUREMENTS AND MAIN RESULTS

The measured endpoint was adverse in-hospital cardiovascular outcomes including heart failure and/or malignant arrhythmia and/or cardiac death. Stepwise logistic regression and a multivariate analysis of propensity-matched cohort were used for analysis of the findings. After adjustment for propensity score, statin therapy was found to produce a significant reduction in cardiovascular outcomes (odds ratio = 0.56; 95% confidence interval [CI], 0.32-0.96, p < 0.05). By using multivariate analysis, the odds ratio for cardiovascular outcomes in patients receiving high-dose statins compared with those treated by low-dose statins was 0.62 (95% CI, 0.41-0.93; p < 0.05).

CONCLUSION

Statin therapy is associated with a significant and dose-dependent reduction in adverse cardiovascular events after CABG surgery. However, further randomized trials still require confirming a causal association between statins and better postoperative outcomes and evaluating the tolerance of such perioperative therapy.

Assessing cardiovascular risk factors after coronary artery bypass surgery: value of an aggressive strategy including systematic follow-up

INTRODUCTION

Coronary revascularization surgery is a palliative treatment modality which should not preclude efforts to treat atherosclerosis.

AIM

To assess ongoing cardiovascular risk factors after coronary artery bypass surgery and develop a strategy to attenuate such factors.

METHODS

108 patients requiring a coronary artery bypass were included: 2 died soon after surgery and 6 were excluded for personal reasons. 100 patients were re-admitted into hospital 7 months after surgery for risk factor assessment. Eight months later, they were re-contacted by telephone (systematic follow-up) for a re-assessment.

RESULTS

The population consisted of 77 men with an average age of 64+/-11 years. Prior to the operation, the known risk factors were: smoking 34%; HBP 61%; cholesterol 47%; diabetes 30%; obesity 25%. During their hospital stay six months after the procedure: 91% of the patients had at least one lipid metabolism abnormality. New-onset diabetes was diagnosed in 5%. Blood pressure was uncontrolled in 18% and 10% were still smoking. Patients tended to be putting on weight and 55% engaged in little or no physical activity. Systematic follow-up: lipid metabolism had normalized in 70% of the patients. Blood glucose levels were significantly lower. Blood pressure was uncontrolled in 9% and 4% were still smoking. Their weight had stabilized and 65% were engaging in moderate-to-strenuous physical activity.

CONCLUSION

Inadequate attention is paid to risk factors after coronary artery bypass surgery. A short hospital stay including a cardiovascular evaluation and education about risk factors has a positive impact on the management of atherosclerosis in the medium term.

Efficacy of alternate day dosing of atorvastatin

Atorvastatin is a synthetic inhibitor of 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor. It has a longer half life and longer duration of action than that of all other available HMG-CoA inhibitors. We evaluated the efficacy of alternate-day dosing of atorvastatin in comparison with the standard one-daily dose on total cholesterol, low and High-density lipoprotein (LDL and HDL) and triglycerides. This study is a randomized, blinded, and controlled clinical trial. Sixty-six patients with LDL cholesterol of more than 100 mg/dl were enrolled. Baseline fasting lipid profile (total cholesterol, LDL, HDL and triglyceride), liver function tests and creatine kinase were drawn. Patients were randomized to three atorvastatin dose groups. Group I received 10 mg of atorvastatin every day, group II received 20 mg of atorvastatin every day, and group III received 20 mg every other day. After 6 weeks of treatment with atorvastatin, fasting lipid profiles, liver function tests and creatine kinase concentrations were re-taken. Compliance to treatment was assessed at each visit. Of the sixty-six patients enrolled, sixty completed the study. All three regimens significantly reduced total cholesterol and LDL compared to baseline. No statistically significant difference existed between the three groups in regards to total or a percentage decrease in total cholesterol and LDL cholesterol at 6 weeks compared to baseline. All regimens were well tolerated and none of the patients showed significant elevation of liver enzyme or creatine kinase during the course of the study. In conclusions the alternate-day dosing of atorvastatin is an efficacious and safe alternate to daily dosing and yet inexpensive.

Comparison of the efficacies of five different statins on inhibition of human saphenous vein smooth muscle cell proliferation and invasion

Statins (HMG-CoA reductase inhibitors) exhibit beneficial effects on the vasculature independently of their cholesterol-lowering properties. These pleiotropic effects underlie the ability of statins to reduce intimal hyperplasia in saphenous vein (SV) bypass grafts by attenuating smooth muscle cell (SMC) invasion and proliferation. Although all statins can effectively lower cholesterol, the pleiotropic effects of individual statins may well differ. We therefore compared the concentration-dependent effects of 4 lipophilic statins (simvastatin, atorvastatin, fluvastatin, and lovastatin) and 1 hydrophilic statin (pravastatin) on the proliferation and invasion of SMC cultured from SV of 9 different patients undergoing coronary artery bypass grafting (CABG). The lipophilic statins inhibited SV-SMC proliferation over a 4-day period with an order of potency of fluvastatin > atorvastatin > simvastatin > lovastatin (IC50 range = 0.07 to 1.77 microM). Similarly, these statins also inhibited SV-SMC invasion through an artificial basement membrane barrier (fluvastatin > atorvastatin > simvastatin >> lovastatin; IC50 range = 0.92 to 26.9 microM). In contrast, the hydrophilic pravastatin had no significant effect on SV-SMC proliferation at concentrations up to 10 microM, nor did it attenuate SV-SMC invasion (up to 30 microM). Our data provide strong evidence that individual statins possess differential pleiotropic effects on SV-SMC function. This may be of clinical relevance in the selection of individual statins for the treatment of CABG patients.

CRP, IL-6 and endothelin-1 levels in patients undergoing coronary artery bypass grafting. Do preoperative inflammatory parameters predict early graft occlusion and late cardiovascular events?

BACKGROUND

Inflammation is a major contributor to atherosclerotic vascular disease. Inflammatory parameters such as C-reactive protein (CRP) and Interleukin-6 (IL-6) have been shown to be strong predictors of cardiovascular events. The association between preoperative inflammatory parameters and early graft occlusion as well as cardiovascular events after coronary artery bypass grafting (CABG) has not, however, been fully elucidated. The aims of the present study were to prospectively investigate the prognostic value of the inflammatory parameters IL-6, CRP, and endothelin (ET-1) to predict early graft occlusion as well as late cardiovascular events after CABG.

METHODS

In the present study 99 patients undergoing CABG because of stable angina pectoris due to significant coronary artery disease were prospectively included. Coronary angiography was repeated 3 months after CABG in 81 patients in order to evaluate early graft occlusion. Blood samples were collected before CABG in all patients. Patients were followed up for a median of 5 (3-7) years after CABG.

RESULTS

Twenty-five patients (31%) had one or more occluded grafts at the 3-month control coronary angiography. The patients with occluded grafts had higher preoperative CRP and IL-6 levels in plasma [CRP 2.22 (1.11-4.47) mg/L vs. 1.23 (0.71-2.27) mg/L P=0.03] and [IL-6 2.88 (1.91-5.94) pg/mL vs. 2.15 (1.54-3.14) pg/mL P=0.006]. There were 23 late cardiovascular events among the 99 patients during the follow-up. Patients experiencing late cardiovascular events had higher preoperative IL-6 levels than those without late cardiovascular events [4.13 (1.83-5.87) pg/mL vs. 2.08 (1.53-2.29) pg/mL, P=0.002] whereas CRP levels did not differ significantly between the two groups [1.5 (0.79-4.41) mg/L vs. 1.33 (0.74-2.48) mg/L, P=0.41]. Looking at IL-6, a cut off value more than 3.8 pg/ml was associated with a significant higher risk for an early graft occlusion (P=0.04) and late cardiovascular events (P=0.00003). Preoperative endothelin-1 did not predict early graft occlusions or late cardiovascular events.

CONCLUSIONS

Raised preoperative IL-6 levels are predictors of both early graft occlusion and late cardiovascular events after CABG. Elevated preoperative CRP levels can predict early graft occlusion after CABG. Endothelin did not differ between the two groups.

Pharmacologic inhibition of vein graft neointimal hyperplasia

Although arterial conduits are widely used and have improved the long-term results of coronary artery bypass grafting, vein grafts remain important additional conduits in coronary surgery. Newer studies show a saphenous vein graft patency of 60% or more at 10 years postoperatively. The pathology of vein graft disease consists of thrombosis, neointimal hyperplasia, and vein graft atherosclerosis, which limit graft longevity. Therapeutic strategies to prevent vein graft disease include external stenting, pharmacotherapy, and gene therapy. The potential benefits of a pharmacologic approach are as follows: (1) Drugs with a broad clinical experience can be used; (2) side effects of systemic application can be minimized by local therapy; and (3) no vascular injury, such as pressurizing the vein for a viral transfection approach, is necessary. The different sites for pharmacotherapy in vein graft disease are reviewed in this article.

Preoperative statin treatment is associated with reduced postoperative mortality and morbidity in patients undergoing cardiac surgery: An 8-year retrospective cohort study

BACKGROUND

Cardiac surgical procedures can be associated with significant morbidity and mortality. Recently, it has been recognized that statins might induce multiple biologic effects independent of lipid lowering that could potentially ameliorate adverse surgical outcomes. Accordingly, this study tested the central hypothesis that pretreatment with statins before cardiac surgery would reduce adverse postoperative surgical outcomes.

METHODS

Demographic and outcomes data were collected retrospectively for 3829 patients admitted for planned cardiac surgery between February 1994 and December 2002. Statin pretreatment occurred in 1044 patients who were comparable with non-statin-pretreated (n = 2785) patients with regard to sex, race, and age. Primary outcomes examined included postoperative mortality (30-day) and a composite morbidity variable.

RESULTS

The odds of experiencing 30-day mortality and morbidity were significantly less in the statin-pretreated group, with unadjusted odds ratios of 0.43 (95% confidence interval [CI], 0.28-0.66) and 0.72 (95% CI, 0.61-0.86), respectively. Risk-adjusted odds ratios for mortality and morbidity were 0.55 (95% CI, 0.32-0.93) and 0.76 (95% CI, 0.62-0.94), respectively, by using a logistic regression model and 0.51 (95% CI, 0.27-0.94) and 0.71 (95% CI, 0.55-0.92), respectively, in the propensity-matched model, demonstrating significant reductions in 30-day morbidity and mortality. In a subsample of patients undergoing valve-only surgery (n = 716), fewer valve-only patients treated with statins experienced mortality, although these results were not statistically significant (1.96% vs 7.5%).

CONCLUSIONS

These findings indicate that statin pretreatment before cardiac surgery confers a protective effect with respect to postoperative outcomes.

Influence of patient characteristics and arterial grafts on freedom from coronary reoperation

OBJECTIVE

Arteriosclerosis is a progressive disease, and many patients require repeat coronary intervention after coronary artery bypass grafting. We sought to identify patient characteristics and operative factors that predict the need for or bias toward reoperative coronary artery bypass grafting.

METHODS

From 1971 to 1998, 48,758 patients underwent primary isolated coronary artery bypass grafting, and 1000 per year were followed every 5 years (n = 26,927). A multivariable time-related analysis was performed to model freedom from coronary reoperation and to identify patient and operative variables associated with occurrence of coronary reoperation.

RESULTS

Freedoms from reoperative coronary artery bypass grafting were 99.6%, 98.4%, 93%, 82%, 72%, and 65% at 1, 5, 10, 15, 20, and 25 years, respectively. Risk of reoperation (hazard function) demonstrated a short, rapidly declining early phase, followed by a long, slow-rising late phase. Patient variables that increased the likelihood of coronary reoperation included younger age (P < .0001), higher total cholesterol (P = .0004) and triglyceride levels (P = .0005), lower high-density lipoprotein (P = .0002) level, diabetes mellitus (P < .0001), and more extensive coronary artery disease (P = .01). Increasing extent of arterial grafting performed at primary coronary artery bypass grafting decreased occurrence of coronary reoperation (P < .0001).

CONCLUSION

Patient factors associated with arteriosclerosis progression and type of bypass conduit influence the need for or bias toward repeat coronary artery bypass grafting. Aggressive patient risk-factor reduction and extensive arterial coronary revascularization at primary coronary artery bypass grafting should result in fewer coronary reoperations.

Preoperative Statin Therapy and Troponin T Predict Early Complications of Coronary Artery Surgery

BACKGROUND

Pretreatment with statins reduces early ischemic events after percutaneous coronary interventions, primarily in patients with a high level of inflammation markers. We sought to examine the association between preoperative statin therapy, systemic inflammation, and myocardial ischemia with the occurrence of early cardiac complications after coronary artery bypass grafting surgery.

METHODS

One hundred forty-one consecutive patients who underwent coronary artery bypass grafting surgery from two university tertiary hospitals were stratified according to their preoperative status of statin therapy (87 treated and 54 nontreated). Preoperative blood samples were collected for measurement of lipid parameters, C-reactive protein, interleukin-6, and troponin T. The evaluated primary endpoint was a composite of death and myocardial infarction at 30 days.

RESULTS

Patients undergoing preoperative statin therapy showed a reduced incidence of death (2.3% versus 13.0%, p = 0.012), myocardial infarction (5.7% versus 18.5%, p = 0.017), and primary combined endpoint (8.0% versus 22.2%, p = 0.017). In the multivariate model, preoperative troponin T greater than 0.01 ng/mL (odds ratio 6.85, p = 0.001) and nonstatin therapy (odds ratio 4.2, p = 0.01) predicted a higher risk of primary endpoint. Statins showed a significant interaction with troponin T status and benefited primarily those patients with positive troponin T. Among 19 patients with troponin T greater than 0.01 ng/mL, the primary endpoint occurred in all 6 nonstatin-treated patients, but it occurred in only 1 of 13 statin-treated patients (p < 0.001). Neither C-reactive protein nor interleukin-6 predicted early complications, nor did they interact with statin therapy (p = not significant).

CONCLUSIONS

Preoperative statin therapy reduces early complications and offers additional protection in patients with positive troponin T status, regardless of inflammatory markers.

The effect of bilateral internal thoracic artery grafting on survival during 20 postoperative years

BACKGROUND

To compare survival of patients receiving bilateral internal thoracic artery grafts and single internal thoracic artery grafts more than 20 postoperative years, assess magnitude of benefit, and identify predictors of benefit.

METHODS

From cohorts of 8123 patients receiving single internal thoracic artery grafts and 2001 receiving bilateral internal thoracic artery grafts during primary isolated bypass operations for multivessel coronary disease between 1971 and 1989, we identified 1152 propensity-matched pairs. Mean follow-up of survivors was 16.5 years, with 51 patients followed for 20 years or more. Hazard function methodology was used to identify risk factors for mortality, compare survival, and assess magnitude of benefit.

RESULTS

Comparison of the matched pairs showed survival of the bilateral internal thoracic artery and single internal thoracic artery groups at 7, 10, 15, and 20 years was 89% versus 87%, 81% versus 78%, 67% versus 58%, and 50% versus 37%, respectively (p < 0.0001). Divergence of bilateral internal thoracic artery and single internal thoracic artery hazard function curves continued to widen through 20 postoperative years. At 20 years, bilateral internal thoracic artery grafting was predicted to produce worse survival in 2.8% of patients, a survival advantage of less than 5% in 12.9%, greater than 10% in 52%, and greater than 15% in 7.6%. Combinations of cardiac and noncardiac descriptors were used to define higher and lower risk patient subsets. Advanced age, abnormal left ventricular function and noncardiac risk factors decreased overall survival but the incremental benefit of bilateral internal thoracic artery grafting persisted.

CONCLUSIONS

Bilateral internal thoracic artery grafting produces improved survival compared with single internal thoracic artery grafting during the second postoperative decade, and the magnitude of that benefit increases through 20 postoperative years.

Simvastatin inhibits MMP‐9 secretion from human saphenous vein smooth muscle cells by inhibiting the RhoA/ROCK pathway and reducing MMP‐9 mRNA levels

Increased matrix metalloproteinase-9 (MMP-9) expression is associated with intimal hyperplasia in saphenous vein (SV) bypass grafts. Recent evidence suggests that HMG-CoA reductase inhibitors (statins) can prevent the progression of vein graft failure. Here we investigated whether statins inhibited MMP-9 secretion from cultured human SV smooth muscle cells (SMC) and examined the underlying mechanisms. SV-SMC from different patients were exposed to phorbol ester (TPA) or PDGF-BB plus interleukin-1alpha (IL-1). MMP-9 secretion and mRNA expression were analyzed using gelatin zymography and RT-PCR, respectively. Specific signal transduction pathways were investigated by immunoblotting and pharmacological inhibition. Simvastatin reduced TPA- and PDGF/IL-1-induced MMP-9 secretion and mRNA levels, effects reversed by geranylgeranyl pyrophosphate and mimicked by inhibiting Rho geranylgeranylation or Rho-kinase (ROCK). MMP-9 secretion induced by PDGF/IL-1 was mediated via the ERK, p38 MAPK, and NFkappaB pathways, whereas that induced by TPA was mediated specifically via the ERK pathway. Simvastatin failed to inhibit activation of these signaling pathways. Moreover, simvastatin did not affect MMP-9 mRNA stability. Together these data suggest that simvastatin reduces MMP-9 secretion from human SV-SMC by inhibiting the RhoA/ROCK pathway and decreasing MMP-9 mRNA levels independently of effects on signaling pathways required for MMP-9 gene expression.