Lipid-lowering therapy and coronary artery bypass graft surgery: what are the benefits?

Coronary artery bypass grafting using bilateral internal thoracic arteries in patients with diabetes and obesity: A systematic review and meta-analysis

Background

Patients with diabetes and obesity are at higher risk of adverse long-term outcomes following coronary artery bypass grafting. The use of bilateral internal thoracic arteries (BITA) can potentially offer survival benefit in higher risk patients compared to single internal thoracic artery (SITA), but BITA is not routinely used due to lack of clear evidence of efficacy and concerns over sternal wound complications.

Methods

Medline, Embase and the Cochrane Library were searched for studies comparing the efficacy and safety of BITA and SITA grafting in patients with diabetes and obesity. Meta-analysis of mortality and sternal wound complications was performed.

Results

We identified eight observational and ten propensity matched studies, and one RCT, comparing BITA and SITA which included patients with diabetes (n = 19,589); two propensity matched studies and one RCT which included patients with obesity (n = 6,972); mean follow up was 10.5 and 11.3 years respectively. Meta-analysis demonstrated a mortality reduction for BITA compared to SITA in patients with diabetes (risk ratio [RR] 0.79; 95% confidence interval [CI] 0.70-0.90; p = 0.0003). In patients with obesity there was a non-significant reduction in mortality in the BITA group (RR 0.73, 95% CI 0.47-1.12; p = 0.15). There was a significantly higher rate of sternal wound complications following BITA observed in patients with diabetes (RR 1.53, 95% CI 1.23-1.90; p = 0.0001) and obesity (RR 2.24, 95% CI 1.63-3.07; p < 0.00001).

Conclusions

BITA is associated with better long-term survival in patients with diabetes. The effects of BITA grafting in patients with obesity are uncertain. BITA is associated with higher rates of sternal wound complications compared to SITA in both patients with diabetes and obesity.

Attainment of Lipid Targets Following Coronary Artery Bypass Graft Surgery: Can We Do Better?

Objective

Patients undergoing coronary artery bypass graft (CABG) surgery remain at high cardiovascular risk; however, few studies have evaluated lipid management and attainment of lipid targets in these patients. We investigated the proportion of CABG surgery patients who attained low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol (HDL-C) targets.

Methods

Data were retrospectively obtained from patients undergoing CABG surgery at an Australian tertiary hospital between February 2015 and August 2020. The most recent lipid profile was recorded (at least 3 weeks post-operatively). We studied patients with electronically available data to ensure accuracy. Target LDL-C was defined as <1.4 (54 mg/dL) and <1.8 mmol/L (70 mg/dL), and target non-HDL-C as <2.2 (85 mg/dL) and <2.6 mmol/L (100 mg/dL), as per the 2019 and 2016 European dyslipidaemia guidelines, respectively.

Results

Follow-up lipid results were available for 484 patients (median post-operative follow-up, 483 days; interquartile range, 177.5–938.75 days). The mean age was 62.7±10.5 years and 387 (80.1%) were male. At discharge, 469 (96.9%) patients were prescribed statins, 425 (90.6%) high-intensity. Ezetimibe was prescribed for 62 (12.8%) patients and a proprotein convertase subtilisin-kexin type 9 inhibitor for 1. LDL-C levels <1.4 and <1.8 mmol/L were attained in 118 (24.4%) and 231 (47.7%) patients, respectively, and non-HDL-C levels <2.2 and <2.6 mmol/L in 140 (28.9%) and 237 (49.0%) patients, respectively.

Conclusion

The use of non-statin lipid-lowering therapies was limited, and many CABG surgery patients did not attain lipid targets despite high-intensity statins. Further studies are required to optimise lipid management in this very high-risk population.

Impact of Modifiable Risk Factors on Long-Term Outcomes after Coronary Artery Bypass Surgery

BACKGROUND

 Risk factors control and secondary prevention measures are often reported to be suboptimal in patients undergoing coronary artery bypass grafting (CABG) and may lead to worse clinical outcomes. We aimed to examine potentially modifiable risk factors in patients undergoing CABG and investigate their association with long-term coronary events.

METHODS

 Cardiovascular risk factors were recorded preoperatively in the setting of a cardiac catheterization laboratory and were analyzed in relation to long-term coronary events, defined as acute coronary syndrome (ACS) or revascularization after CABG.

RESULTS

 Study population included 1,125 patients undergoing CABG without previous revascularization. Modifiable risk factors included hypertension (71%), hyperlipidemia (67%), diabetes (42%), obesity (28%), and smoking (21%). Only 8% did not have any of the five risk factors. During the mean follow-up of 93 ± 52 months after CABG, 179 patients (16%) experienced a coronary event. Incidence rates were higher in patients with than without the presence of each of the modifiable risk factors, except obesity. Active smoking (hazard ratio [HR]: 1.51; 95% confidence interval [CI]: (1.07-2.13); p = 0.020), presence of diabetes (HR: 1.61; 95% CI: 1.18-2.18; p = 0.002), and hyperlipidemia (HR: 2.13; 95% CI: 1.45-3.14; p < 0.001) were independent predictors of future coronary events after CABG; they also displayed a progressive stepwise increment in the risk of long-term coronary events when cumulatively present.

CONCLUSIONS

 In patients undergoing CABG, diabetes, hyperlipidemia, and smoking, as documented preoperatively, were potentially modifiable risk factors that were independently and cumulatively associated with long-term risk of ACS or coronary revascularization, highlighting the importance of early identification and risk factors control for improving cardiovascular health after CABG.

Impact of lipid levels and high-intensity statins on vein graft patency after CABG: Midterm results of the ACTIVE trial

BACKGROUND

High-dose atorvastatin did not improve 1-year vein graft patency in the recent Aggressive Cholesterol Therapy to Inhibit Vein Graft Events trial. However, it remains unknown whether high-intensity statins may impact graft disease in the years that follow.

METHODS

In the trial, patients (N = 173) were randomized to receive atorvastatin 10 or 80 mg for 1 year after coronary bypass surgery (CABG). Beyond 1 year, the choice of statin was left to the patient's physician. In this study of participants who agreed to follow-up (N = 76), low-density lipoprotein (LDL) levels were measured and graft patency was assessed 3 years after surgery.

RESULTS

The rate of vein graft disease 3 years after surgery was not significantly reduced with atorvastatin 80 mg during the first postoperative year or the use of open-label high-intensity statin thereafter (p = NS). However, a trend was observed between higher LDL levels during the first postoperative year and a greater incidence of vein graft disease at 3 years (p = .12). Among patients who had LDL levels more than 90 mg/dl in the first year after CABG, 38.5% had vein graft disease at 3 years, compared to 19.0% for those with LDL levels less than 90 mg/dl (p = .15). Higher mean LDL levels during the first postoperative year were associated with a higher rate of vein disease 3 years after surgery both at the graft level (p = .03) and at the patient level (p = .03) in multivariate analysis.

CONCLUSIONS

Higher LDL levels during the first postoperative year were associated with significantly greater vein graft disease 3 years after CABG.

Post-Coronary Artery Bypass Medications in Dialysis Patients: Do We Need to Change Strategies?

BACKGROUND

Coronary artery bypass grafting (CABG) is frequently performed in patients with end-stage renal disease (ESRD) together with severe coronary artery disease, after which, patients with ESRD have higher surgical risk and poorer long-term outcomes. We report our experience in patients with ESRD who survived in CABG and identify predictors of long-term outcomes.

METHODS

We retrospectively investigated 93 consecutive patients with ESRD who survived to discharge after isolated CABG between January 2005 and December 2016 at our institution. Long-term outcomes, including all-cause mortality after discharge, readmission due to major adverse cardiac events, and reintervention, were evaluated. Predictors affecting long-term outcomes were also analyzed.

RESULTS

The rates of freedom from all-cause mortality after discharge in 1, 3, 5, and 10 years were 92.1, 81.3, 71.9, and 34.9%, respectively. The rates of freedom from readmission due to major adverse cardiac events in 1, 3, 5, and 10 years were 90.7, 79.1, 69.9, and 55.6%, respectively. The rates of freedom from reintervention in 1, 3, 5, and 10 years were 95.3, 86.5, 79.0, and 66.6%, respectively. Postoperative β-blocker and statin use significantly improved overall long-term survival (β-blocker, p = 0.013; statin, p = 0.009). After case-control matching, patients who received statins showed better long-term survival than those without statins. The comparison of long-term survival between patients with and without β-blockers showed no significant difference after matching.

CONCLUSIONS

After CABG, dialysis patients who survived to discharge had acceptable long-term overall survival. Post-CABG statin use in dialysis patients is a predictor of better long-term survival.

Outcomes of patients with and without baseline lipid-lowering therapy undergoing revascularization for left main coronary artery disease: analysis from the EXCEL trial

OBJECTIVES

There is a paucity of data on the effect of baseline lipid-lowering therapy (LLT) in patients undergoing revascularization for left main (LM) coronary artery disease (CAD). We compared outcomes for patients with LMCAD randomized to percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) according to the presence of baseline LLT in the EXCEL trial.

PATIENTS AND METHODS

The EXCEL trial randomized 1905 patients with LMCAD and SYNTAX scores up to 32 to PCI with everolimus-eluting stents versus CABG. Patients were categorized according to whether they were medically treated with LLT at baseline, and their outcomes were examined using multivariable Cox proportional hazards regression. The primary endpoint was a composite of death, stroke, or myocardial infarction at 3 years.

RESULTS

Among 1901 patients with known baseline LLT status, 1331 (70.0%) were medically treated with LLT at baseline. There were no significant differences between the PCI and CABG groups in the 3-year rates of the primary endpoint in patients with versus without baseline LLT (Pinteraction=0.62). Among patients with baseline LLT, the 3-year rate of ischemia-driven revascularization was higher after PCI compared with CABG (13.7 vs. 5.3%; adjusted hazard ratio=2.97; 95% confidence interval: 1.95-4.55; P<0.0001), in contrast to patients without baseline LLT (9.8 vs. 12.1%; adjusted hazard ratio=0.79; 95% confidence interval: 0.47-1.33; P=0.39) (Pinteraction=0.0003).

CONCLUSION

In the EXCEL trial, 3-year major adverse event rates after PCI versus CABG for LMCAD were similar and consistent in patients with and without LLT at baseline; however, revascularization during follow-up was more common after PCI compared with CABG in patients with baseline LLT, but not in those without baseline LLT.

Attainment of lipid goals and long-term mortality after coronary-artery bypass surgery

Introduction

There is paucity of data regarding lipid goal attainment after coronary-artery bypass graft surgery (CABG) and its impact on adverse outcomes. We aimed to investigate the attainment of lipid goals and the association between plasma lipid levels achieved after CABG and mortality.

Methods

Retrospective analysis of 1230 patients undergoing CABG. Mortality was examined in relation to most-recent lipid levels attained, categorized by clinically-relevant thresholds, and according to the improvement from pre-operative levels.

Results

Low-density lipoprotein cholesterol (LDL-C) < 70 mg/dL was attained by 44% of the patients. After multivariable adjustment, the hazard ratio for long-term mortality was 1.33 (95% confidence interval, 1.05–1.67) and 1.97 (1.55–2.50) for patients attaining LDL-C 70–100 mg/dL and >100 mg/dL, respectively, compared with LDL-C < 70 mg/dL. The hazard ratio was 1.42 (1.07–1.88) and 1.73 (1.33–2.23) for patients attaining high-density lipoprotein cholesterol (HDL-C) 40–50 mg/dL and <40 mg/dL, respectively, compared with HDL-C > 50 mg/dL; and 1.11 (0.85–1.45) and 4.28 (1.89–9.68) for patients with triglycerides 200–500 mg/dL and >500 mg/dL compared with triglycerides <200 mg/dL. A progressive stepwise association was seen between the cumulative status of the lipid measures achieved and long-term mortality, with the lowest risk observed in those with optimal level of all lipid measures ( p < 0.0001). Improvement in any of the lipid measures from pre-operative to latest documented levels was associated with reduced mortality.

Conclusions

Lack of attainment of optimal levels of routine lipid measures after CABG was common and associated both independently and additively with long-term mortality, emphasizing the importance of addressing plasma lipid profile as both a risk marker and a treatment target after CABG.

Quinine induced simvastatin toxicity through cytochrome inhibition - a case report

Background

Nocturnal leg cramps are painful, involuntary muscle contractions commonly seen in elderly. While mostly harmless, they can severely impair quality of life and often disrupt sleep. Adverse drug effects may be responsible for a fraction of nocturnal leg cramps but often go unrecognized, resulting in additional prescribing intended to deal with adverse effects that might be better addressed by reduction, substitution, or discontinuation of the offending agent.

Case presentation

An 87 year old female presented as outpatient in family medicine with nocturnal leg cramps which had been present for five years and increasingly burdened her quality of life. She had been using quinine 200 mg once daily for symptomatic relief but the cramps kept returning with increasing intensity. During clinical examination we found neither structural nor neurological or metabolic disorders that explained her symptoms. When doing a medication analysis, we found that she was taking a statin together with quinine. Quinine is a cytochrome P450 isoenzyme 3A4 inhibitor, the very enzyme which is involved in the metabolism of most statins. Therefore the use of both substances simultaneously increases blood levels of the statin thereby increasing the risk of side effects including symptomatic myopathy and myalgia. After discontinuing both medications, the patient was, and remained, symptom free.

Conclusion

This case report describes a possible medication interaction that has rarely been noted in literature.

Efficacy of Different Perioperative Statin Regimens on Protection Against Post-Coronary Artery Bypass Grafting Major Adverse Cardiac and Cerebral Events

OBJECTIVES

Comparing different perioperative statin regimens for the prevention of post-coronary artery bypass grafting adverse events.

DESIGN

A randomized, prospective study.

SETTING

Cardiothoracic surgical units in a government hospital.

PARTICIPANTS

The study comprised 94 patients scheduled for elective, isolated on- or off- pump coronary artery bypass grafting.

INTERVENTIONS

Patients were assigned randomly to 1 of the following 3 treatment groups: group I (80 mg of atorvastatin/day for 2 days preoperatively), group II (40 mg of atorvastatin/day for 5-9 days preoperatively), or group III (80 mg of atorvastatin/day for 5-9 days preoperatively). The same preoperative doses were restarted postoperatively and continued for 1 month.

MEASUREMENTS AND MAIN RESULTS

Cardiac troponin I, creatine kinase, and C-reactive protein (CRP) levels were assayed preoperatively; at 8, 24, and 48 hours postoperatively; and at discharge. CRP levels at 24 hours (p = 0.045) and 48 hours (p = 0.009) were significantly lower in group III compared with the other 2 groups. However, troponin I levels at 8 hours (p = 0.011) and 48 hours (p = 0.025) after surgery were significantly lower in group II compared with group III. The incidence of postoperative major adverse cardiac and cerebrovascular events was assessed, and there was no significant difference among the 3 groups.

CONCLUSION

The 3 regimens did not result in any significant difference in outcomes, but only simple trends. The higher-dose regimen resulted in a significant reduction in the CRP level. Thus, more studies are needed to confirm the benefit of higher-dose statins for the protection from post-coronary artery bypass grafting adverse events.

Feasibility study for removing calcified material using a planar rectangular ultrasound transducer

BACKGROUND

The aim of the proposed study was to conduct a feasibility study using a flat rectangular (3 mm × 10 mm) MRI compatible transducer operating at 5.3 MHz for destroying calcified material in an in vitro model. The proposed method can be used in the future for treating atherosclerosis plaques of the coronary, carotid or peripheral arteries.

METHODS

The system was tested initially on calcium rods. Another test was performed in a hydroxyapatite-polylactide model.

RESULTS

A parametric study was performed where the mass of calcified material removed was studied as a function of intensity, pulse repetition frequency (PRF), duty factor (DF) and presence of bubbles.

CONCLUSIONS

The amount of calcified material removed is directly related to the intensity, PRF and DF. It was found that the presence of bubbles accelerates the removal of calcified material. In order to ensure that pure mechanical mode ultrasound was used, the protocols were designed so that the temperature does not exceed 1 °C.

Bilateral internal mammary artery grafting in obese: outcomes, concerns and controversies

Obese patients are generally considered unsuitable to receive bilateral internal mammary arteries (BIMA) during coronary artery bypass grafting (CABG) due to the perceived vulnerability to sternal wound infection and lack of evidence supporting long-term survival benefit. However, no consistent evidence currently discourages the use of BIMA in obese patients. The present review questions the common perception that obesity unacceptably increases the risk of sternal wound complications in patients receiving BIMA grafting. Moreover, the use of skeletonization harvesting technique is expected to further minimize such a risk. Our institutional experience confirmed that BIMA grafting is a safe strategy which does not increase operative mortality and does not significantly affect the incidence of sternal wound complications. On the other hand, a long term benefit in terms of overall survival and freedom from repeat revascularization from the use of BIMA was found.

Atorvastatin regulates apoptosis in chronically ischemic myocardium

BACKGROUND

We previously demonstrated that atorvastatin upregulates proangiogenic proteins and increases arteriolar density in ischemic myocardium. Despite this, there was a lack of collateral-dependent perfusion, possibly related to apoptosis. We utilized a swine model of metabolic syndrome and chronic myocardial ischemia to investigate the effects of atorvastatin on apoptosis.

MATERIALS AND METHODS

Sixteen Ossabaw miniswine were fed a high-cholesterol diet for 14 weeks then underwent surgical placement of an ameroid constrictor to their circumflex artery inducing chronic ischemia. Eight pigs additionally received supplemental atorvastatin (1.5 mg/kg daily). Myocardium was harvested six months later for western blotting and TUNEL staining.

RESULTS

Animals supplemented with atorvastatin had significant increases in markers associated with apoptosis including p-38, BAX, and caspase 3 (p < 0.05). Atorvastatin supplementation also resulted in significant increases in expression of cell survival proteins Bcl-2 and P-ERK and an overall decrease in apoptosis demonstrated by TUNEL staining (p < 0.05).

CONCLUSIONS

Atorvastatin acts on multiple pathways and its effects on angiogenesis remain unclear. Although there is increased expression in several markers of apoptosis, key anti-apoptotic proteins were also upregulated with an overall decrease in apoptosis. Further investigation of these pathways may provide insight into the role of statins on myocardial protection after ischemia.

Why is the mammary artery so special and what protects it from atherosclerosis?

The internal mammary artery (IMA) grafts have been associated with long-term patency and improved survival as compared to saphenous vein grafts (SVGs). Early failure of IMA is attributed to poor surgical technique and less with thrombosis. Similarly, bypass surgery especially with the use of IMA has also been shown to be superior at 1-year as well as over five years compared to percutaneous procedures, including the use of drug-eluting stents for the treatment of coronary artery disease. The superiority of IMAs over SVGs can be attributed to its striking resistance to the development of atherosclerosis. Structurally its endothelial layer shows fewer fenestrations, lower intercellular junction permeability, greater anti-thrombotic molecules such as heparin sulfate and tissue plasminogen activator, and higher endothelial nitric oxide production, which are some of the unique ways that make the IMA impervious to the transfer of lipoproteins, which are responsible for the development of atherosclerosis. A better comprehension of the molecular resistance to the generation of adhesion molecules that are involved in the transfer of inflammatory cells into the arterial wall that also induce smooth muscle cell proliferation is needed. This basic understanding is crucial to championing the use of IMA as the first line of defense for the treatment of coronary artery disease.

The statin-iron nexus: anti-inflammatory intervention for arterial disease prevention

OBJECTIVES

We postulated the existence of a statin-iron nexus by which statins improve cardiovascular disease outcomes at least partially by countering proinflammatory effects of excess iron stores.

METHODS

Using data from a clinical trial of iron (ferritin) reduction in advanced peripheral arterial disease, the Iron and Atherosclerosis Study, we compared effects of ferritin levels versus high-density lipoprotein to low-density lipoprotein ratios (both were randomization variables) on clinical outcomes in participants receiving and not receiving statins.

RESULTS

Statins increased high-density lipoprotein to low-density lipoprotein ratios and reduced ferritin levels by noninteracting mechanisms. Improved clinical outcomes were associated with lower ferritin levels but not with improved lipid status.

CONCLUSIONS

There are commonalities between the clinical benefits of statins and the maintenance of physiologic iron levels. Iron reduction may be a safe and low-cost alternative to statins.

Simvastatin inhibits the additive activation of ERK1/2 and proliferation of rat vascular smooth muscle cells induced by combined mechanical stress and oxLDL through LOX-1 pathway

Vein grafts interposed into arteries are susceptible to the development of atherosclerosis due to rapid increases in blood pressure. This process is accelerated in patients with hyperlipidemia. The molecular mechanism underlying this process is unknown. In this study, quiescent rat vascular smooth muscle cells (VSMCs) were treated in vitro with mechanical stretch stress (10% elongation) with and without oxLDL (25 μg/ml) in the presence and absence of simvastatin (2.5 μmol/L). The results demonstrate that stretch stress and oxLDL can each induce activation of ERK1/2 and Ki-67 expression in VSMCs, but the peak levels of ERK activation and Ki-67 expression were observed in groups subjected to both stretch stress and oxLDL. Simvastatin was found to inhibit increased ERK activation and Ki-67 expression in VSMCs subjected to stretch stress with or without oxLDL. Mechanically, simvastatin was also found to inhibit increased expression of LOX-1 (a receptor of oxLDL) in VSMCs subjected to stretch stress with or without oxLDL. Knockdown of LOX-1 via small interfering RNAs (siRNA-LOX-1) resulted in obvious inhibition of ERK activation in VSMCs subjected to stretch stress with and without oxLDL. These results suggest that combined stretch stress and oxLDL can additively promote the activation of ERK1/2 leading to accelerated proliferation of VSMCs (e.g. increased Ki-67 expression) via LOX-1 signal pathway. This was found to be partially inhibited by simvastatin. These results may provide important data for the treatment and prevention of hypertension with or without hyperlipidemia.