Perioperative diltiazem or nitroglycerin in on-pump coronary artery bypass: A systematic review and network meta-analysis

Consensus statement-graft treatment in cardiovascular bypass graft surgery

Coronary artery bypass grafting (CABG) is and continues to be the preferred revascularization strategy in patients with multivessel disease. Graft selection has been shown to influence the outcomes following CABG. During the last almost 60 years saphenous vein grafts (SVG) together with the internal mammary artery have become the standard of care for patients undergoing CABG surgery. While there is little doubt about the benefits, the patency rates are constantly under debate. Despite its acknowledged limitations in terms of long-term patency due to intimal hyperplasia, the saphenous vein is still the most often used graft. Although reendothelialization occurs early postoperatively, the process of intimal hyperplasia remains irreversible. This is due in part to the persistence of high shear forces, the chronic localized inflammatory response, and the partial dysfunctionality of the regenerated endothelium. "No-Touch" harvesting techniques, specific storage solutions, pressure controlled graft flushing and external stenting are important and established methods aiming to overcome the process of intimal hyperplasia at different time levels. Still despite the known evidence these methods are not standard everywhere. The use of arterial grafts is another strategy to address the inferior SVG patency rates and to perform CABG with total arterial revascularization. Composite grafting, pharmacological agents as well as latest minimal invasive techniques aim in the same direction. To give guide and set standards all graft related topics for CABG are presented in this expert opinion document on graft treatment.

Perioperative cardiac risk reduction in non cardiac surgery

For patients undergoing nonemergent noncardiac surgery, care must be taken to identify patients at increased risk of major adverse cardiovascular events, as these remain a significant source of perioperative morbidity and mortality. Identification of at-risk patients requires careful attention to risk factors including assessment of functional status, medical comorbidities, and a medication assessment. After identification, to minimize perioperative cardiac risk, care should be taken through a combination of appropriate medication management, close monitoring for cardiovascular ischemic events, and optimization of pre-existing medical conditions. There are multiple society guidelines that aim to mitigate risk of cardiovascular morbidity and mortality in patients undergoing nonemergent noncardiac surgery. However, the rapid evolution of medical literature often creates gaps between the existing evidence and best practice recommendations. In this review, we aim to reconcile the recommendations made in the guidelines from the major cardiovascular and anesthesiology societies from the USA, Canada, and Europe, and to provide updated recommendations based on new evidence.

Role of magnesium alone or in combination with diltiazem and/or amiodarone in prevention of atrial fibrillation following off-pump coronary artery bypass grafting

Objectives

In this study the authors have tried to examine the role of magnesium alone or in combination with diltiazem and / or amiodarone in prevention of atrial fibrillation (AF) following off-pump coronary artery bypass grafting (CABG).

Background

AF after CABG is common and contributes to morbidity and mortality. Various pharmacological preventive measures including magnesium, amiodarone, diltiazem, and combination therapy among others have been tried to lower the incidence of AF. Most of the studies have been performed in patients undergoing conventional on-pump CABG. In this uncontrolled trial, efficacy of magnesium alone or in combination with amiodarone and / or diltiazem has been studied in patients undergoing off-pump CABG.

Methods

One hundred and fifty patients undergoing off-pump CABG were divided into 3 groups, Group M (n=21) received intraoperative magnesium infusion at 30mg/ kg over 1 hour after midline sternotomy; Group MD (n=78) received magnesium infusion in similar manner with diltiazem infusion at 0.05 μg/kg/hr throughout the intraoperative period; Group AMD (n=51) received preoperative oral amiodarone at a dose of 200 mg three times a day for 3 days followed by 200 mg twice daily for another 3 days followed by 200 mg once daily till the day of surgery along with magnesium and diltiazem infusion as in other groups. AF lasting more than 10 min or requiring medical intervention was considered as AF.

Results

The overall incidence of postoperative AF was 12.6% with 11.7% in group AMD, 19% in group M, and 11.5% in group MD, which was not statistically significant.

Conclusions

It is concluded that the use of amiodarone and/or diltiazem in addition to magnesium did not result in additional benefit of lowering the incidence of AF.

Protective or Inhibitory Effect of Pharmacological Therapy on Cardiac Ischemic Preconditioning: A Literature Review

Ischemic preconditioning (IP) is an innate phenomenon, triggered by brief, non-lethal cycles of ischemia/reperfusion applied to a tissue or organ that confers tolerance to a subsequent more prolonged ischemic event. Once started, it can reduce the severity of myocardial ischemia associated with some clinical situations, such as percutaneous coronary intervention (PCI) and intermittent aortic clamping during coronary artery bypass graft surgery (CABG). Although the mechanisms underlying IP have not been completely elucidated, several studies have shown that this phenomenon involves the participation of cell triggers, intracellular signaling pathways, and end-effectors. Understanding this mechanism enables the development of preconditioning mimetic agents. It is known that a range of medications that activate the signaling cascades at different cellular levels can interfere with both the stimulation and the blockade of IP. Investigations of signaling pathways underlying ischemic conditioning have identified a number of therapeutic targets for pharmacological manipulation. This review aims to present and discuss the effects of several medications on myocardial IP.

Perioperative diltiazem therapy was not associated with improved perioperative and long-term outcomes in patients undergoing on-pump coronary artery bypass grafting

Background

Diltiazem has been used during the perioperative period in patients undergoing coronary artery bypass grafting (CABG) to prevent arterial graft spasm. However, its long-term outcome effects remain unclear.

Methods

Patient records obtained from the Society of Thoracic Surgeons and the Geisinger Clinic electronic health records between October 2008 and October 2018 were screened. Adult patients who had isolated CABG with cardiopulmonary bypass were included. Cohorts of patients who received diltiazem (DILT) and those who did not (non-DILT) were matched by propensity scores based on age, gender, surgical year, Society of Thoracic Surgeons mortality and morbidity scores, and number of arterial grafts. Incidence rate ratios (IRRs) were estimated for DILT vs non-DILT on short-term adverse outcomes. Long-term survival over time was compared between DILT vs non-DILT using Kaplan-Meier curves.

Results

Among the 1004 patients included in the analyses, IRRs for the DILT group relative to the non-DILT group were: 30-day all-cause mortality, IRR: 2.33, 95% confidence interval (CI): 0.91-5.96, P=0.07; postoperative myocardial ischaemia, IRR: 1.10, 95% CI: 0.60-2.02, P=0.75; new onset atrial fibrillation, IRR: 1.06, 95% CI: 0.78-1.43, P=0.73; stroke/transient ischaemic attack, IRR: 0.76, 95% CI: 0.17-3.38, P=0.71. For long-term survival, Kaplan-Meier curves stratified by diltiazem revealed no differences in survival rates between DILT and non-DILT groups.

Conclusion

For patients undergoing on-pump CABG, perioperative diltiazem therapy did not show significant short- or long-term outcome advantages over those who did not receive diltiazem.

Effects of inorganic nitrate on ischaemia-reperfusion injury after coronary artery bypass surgery

Background

Nitric oxide (NO) is an important signalling molecule in the cardiovascular system with protective properties in ischaemia–reperfusion injury. Inorganic nitrate, an oxidation product of endogenous NO production and a constituent in our diet, can be recycled back to bioactive NO. We investigated if preoperative administration of inorganic nitrate could reduce troponin T release and other plasma markers of injury to the heart, liver, kidney, and brain in patients undergoing cardiac surgery.

Methods

This single-centre, randomised, double-blind, placebo-controlled trial included 82 patients undergoing coronary artery bypass surgery with cardiopulmonary bypass. Oral sodium nitrate (700 mg×2) or placebo (NaCl) were administered before surgery. Biomarkers of ischaemia–reperfusion injury and plasma nitrate and nitrite were collected before and up to 72 h after surgery. Troponin T release was our predefined primary endpoint and biomarkers of renal, liver, and brain injury were secondary endpoints.

Results

Plasma concentrations of nitrate and nitrite were elevated in nitrate-treated patients compared with placebo. The 72-h release of troponin T did not differ between groups. Other plasma biomarkers of organ injury were also similar between groups. Blood loss was not a predefined outcome parameter, but perioperative bleeding was 18% less in nitrate-treated patients compared with controls.

Conclusion

Preoperative administration of inorganic nitrate did not influence troponin T release or other plasma biomarkers of organ injury in cardiac surgery.

Clinical trial registration

NCT01348971.

Perioperative Cardiac Risk Reduction in Noncardiac Surgery

Major adverse cardiovascular events are a significant source of morbidity and mortality in the perioperative setting, estimated to occur in approximately 5% of patients undergoing nonemergent noncardiac surgery. To minimize the incidence and impact of these events, careful attention must be paid to preoperative cardiovascular assessment to identify patients at high risk of cardiovascular complications. Once identified, cardiovascular risk reduction is achieved through optimization of medical conditions, appropriate management of medication, and careful monitoring to allow for early identification of-and intervention for-any new conditions that would increase the risk of adverse cardiovascular outcomes. The major cardiovascular and anesthesiology societies in the United States, Europe, and Canada have published guidelines for perioperative management of patients undergoing noncardiac surgery. However, since publication of these guidelines, there has been a practice-changing evolution in the medical literature. In this review, we attempt to reconcile the recommendations made in these 3 comprehensive guidelines, while updating recommendations, based on new evidence, when available.

Different vasoreactivity of arterial bypass grafts versus native coronary arteries in response to acetylcholine

BACKGROUND

Coronary angiography is often performed in patients with recurrent angina after successful coronary artery bypass grafting (CABG) in search of the progression of atherosclerosis. However, in many of these patients, no relevant stenosis can be detected. We speculate that coronary spasm may be associated with angina in these patients.

METHODS

From 2307 patients with unobstructed coronaries who underwent intracoronary acetylcholine spasm provocation testing (ACh-test) between 2012 and 2016, 54 consecutive patients who fulfilled the following inclusion criteria were included in this cohort study: previous left internal thoracic artery (LITA) bypass on the left anterior descending (LAD) coronary artery, ongoing/recurrent angina pectoris, no significant (< 50%) coronary artery or bypass stenosis. In all participants, the ACh-test was performed via the LITA bypass.

RESULTS

In 14 patients (26%) the ACh-test elicited epicardial spasm of the LAD distal to the anastomosis (≥ 90% diameter reduction with reproduction of the patient's symptoms and ischemic ECG shifts). Microvascular spasm (reproduction of symptoms and ischemic ECG-changes but no epicardial spasm) was seen in 30 patients (55%). The ACh-test was normal in the remaining 10 patients (19%). ACh-testing did not elicit any relevant vasoconstriction in the LITA bypasses in contrast to the LAD on quantitative coronary analyses (4.89 ± 7.36% vs. 52.43 ± 36.07%, p < 0.01).

CONCLUSION

Epicardial and microvascular coronary artery spasm are frequent findings in patients with ongoing or recurrent angina after CABG but no relevant stenosis. Vasoreactivity to acetylcholine is markedly different between LITA bypasses and native LAD arteries with vasoconstriction almost exclusively occurring in the LAD.