Aspirin responsiveness safely lowers perioperative cardiovascular risk

Antiplatelet Resistance in Coronary Artery Bypass Grafting: A Systematic Review

Background

This systematic review examines the occurrence and implications of resistance to primary antiplatelet agents, aspirin and clopidogrel, often utilised in patients undergoing coronary artery bypass grafting (CABG), alongside the methodologies for assessment of such resistance.

Methods

An extensive literature search across various databases such as PubMed, MEDLINE via Ovid, Embase, and Cochrane CENTRAL until May 2024 was conducted to identify studies evaluating antiplatelet resistance in on-pump and off-pump CABG patients. Following quality assessment, only high-quality studies were incorporated into this review.

Results

This review included 19 studies with 3,915 patients, four of which were randomised controlled trials and 15 were observational studies. Aspirin resistance incidence ranged from 11.0% to 51.5%, while clopidogrel resistance was 22%. Antiplatelet resistance, assessed through a wide variety of methods, was associated with a 13 times increase in the risk of vein graft occlusion and increased rates of mortality, myocardial infarction, and target vessel revascularisation in the case of clopidogrel resistance. The effect of cardiopulmonary bypass on antiplatelet resistance remains ambiguous.

Conclusion

The academic literature lacks a standardised definition for antiplatelet resistance. Assessment methodologies greatly vary, leading to noninterchangeable outcomes. While aspirin resistance has a conflicting overall significant impact on adverse outcomes, clopidogrel resistance correlates with poorer clinical outcomes.

Factors associated with symptomatic postoperative myocardial infarction after endovascular aneurysm repair

OBJECTIVE

Endovascular aneurysm repair (EVAR) has now become the most common operation to treat abdominal aortic aneurysms (AAAs). One of the perceived benefits of EVAR over open AAA repair is reduced incidence of perioperative cardiac complications and mortality. The purpose of this study was to determine risk factors associated with postoperative myocardial infarction (POMI) in patients who have undergone EVAR.

METHODS

Data were obtained from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database for the years 2012 to 2015 in the Participant Use Data File. All patients in the database who underwent EVAR during this time were identified. These patients were then divided into two groups: those with POMI and those without. Bivariate analysis was done for preoperative, intraoperative, and postoperative risk factors, followed by multivariable analysis to determine associations of independent variables with POMI. A risk prediction model for POMI was created to accurately predict incidence of POMI after EVAR.

RESULTS

A total of 7702 patients (81.3% male, 18.7% female) were identified who underwent EVAR from 2011 to 2015. Of these patients, 110 (1.4%) had POMI and 7592 (98.6%) did not. Several risk factors were related to an increased risk of POMI, including dependent functional health status, need for lower extremity revascularization, longer operation time, and ruptured AAA (P < .05, all).On multivariable analysis, the following factors were found to have significant associations with POMI: return to operating room (odds ratio [OR], 1.84; confidence interval [CI], 1.10-3.09; P = .020), ruptured AAA (OR, 1.87; CI, 1.18-2.95; P = .008), pneumonia (OR, 1.94; CI, 1.01-3.73; P = .048), age >80 years (compared with <70 years; OR, 2.30; CI, 1.36-3.86; P = .002), unplanned intubation (OR, 4.07; CI, 2.31-7.18; P < .001), and length of hospital stay >6 days (OR, 8.43; CI, 4.75-14.94; P < .001). The risk prediction model showed that in the presence of all these risk factors, the incidence of POMI was 58.3%. The incidence of cardiac arrest and death was significantly higher for patients with POMI compared with patients without POMI (cardiac arrest, 11.9% vs 1.3%; death, 10.2% vs 1.1%).

CONCLUSIONS

In patients who undergo EVAR, the risk of POMI is increased for those who are older, who present with a ruptured AAA, who have pneumonia, who have unplanned intubation, and who have prolonged hospital stay. Patients who suffer from POMI have higher risk of having cardiac arrest and death.

Incidence of Myocardial Infarction After High-Risk Vascular Operations in Adults

Importance

Advances in perioperative cardiac management and an increase in the number of endovascular procedures have made significant contributions to patients and postoperative myocardial infarction (POMI) risk following high-risk vascular procedures. Whether these changes have translated into real-world improvements in POMI incidence remain unknown.

Objective

To examine the temporal trends of myocardial infarction (MI) following high-risk vascular procedures.

Design, Setting, and Participants

A retrospective cohort study was performed using data collected from January 1, 2005, to December 31, 2013, in the American College of Surgeons National Surgery Quality Improvement Program database, to which participating hospitals across the United States report their preoperative, operative, and 30-day outcome data. A total of 90 303 adults who underwent a high-risk vascular procedure-open aortic surgery or infrainguinal bypass-during the study period were identified. Patients were divided into cohorts based on their year of operation, and their baseline cardiac risk factors and incidence of POMI were compared. Cases from 2005 to 2014 in the database were eligible for inclusion if one of their Current Procedural Terminology codes matched any of the operations identified as a high-risk vascular procedure. Data analysis took place from August 1, 2016, to November 15, 2016.

Exposures

The main exposure was the year of the operation. Other variables of interest included demographics, comorbidities, and other risk factors for MI.

Main Outcomes and Measures

Primary outcome of interest was the incidence of POMI.

Results

Of the 90 303 patients included in the study, 22 836 (25.3%) had undergone open aortic surgery and 67 467 (74.7%) had had infrainguinal bypass. The open aortic cohort comprised 16 391 men (71.9%), had a mean (SD) age of 69.1 (11.5) years, and was predominantly white (18 440 patients [80.8%] self-identified as white race/ethnicity). The infrainguinal bypass cohort included 41 845 men (62.1%), had a mean (SD) age of 66.7 (11.7) years, and had 51 043 patients (75.7%) who self-identified as white race/ethnicity. During the study period, patients who underwent open aortic procedures were more likely to be classified as American Society of Anesthesiologists class IV (7426 patients [32.6%] vs 15 683 [23.3%] for the infrainguinal bypass cohort) or class V (1131 [5.0%] vs 206 [0.3%]; P < .001) and to undergo emergency procedures (4852 [21.3%] vs 4954 [7.3%]; P < .001). The open aortic procedure cohort also experienced significantly higher actual incidence of POMI (464 [3.0%] vs 1270 [1.9%]; P < .001). From 2009 to 2014, the incidence of POMI demonstrated no substantial temporal change (2.7% in 2009 to 3.1% in 2014; P = .64 for trend). Postoperative MI was consistently associated with poor prognosis, with a 3.62-fold (95% CI, 2.25-5.82) to 11.77-fold (95% CI, 6.10-22.72) increased odds of cardiac arrest and a 3.01-fold (95% CI, 2.08-4.36) to 6.66-fold (95% CI, 4.66-9.52) increased odds of mortality.

Conclusions and Relevance

The incidence of MI did not significantly decrease in the past decade and has been consistently associated with worse clinical outcomes. Further inquiry into why advanced perioperative care did not reduce cardiac complications is important to quality improvement efforts.

Effect of Frailty and Age on Platelet Aggregation and Response to Aspirin in Older Patients with Atrial Fibrillation: A Pilot Study

INTRODUCTION

Frailty is associated with changes in inflammation, coagulation, and possibly platelet function. Aspirin is still prescribed for stroke prevention in older patients with atrial fibrillation, although not recommended by current guidelines. In frail older people, it is unclear whether platelet aggregability and response to aspirin are altered. This study aims to investigate the effects of frailty and chronological age on platelet aggregability and on responses to aspirin in older patients with atrial fibrillation.

METHODS

Inpatients with atrial fibrillation aged ≥65 years were recruited from a tertiary referral hospital in Sydney, Australia. Frailty was determined using the Reported Edmonton Frail Scale. Platelet aggregation studies were performed using whole blood impedance aggregometry.

RESULTS

Data from 115 participants were analyzed (mean age 85 ± 6 years, 41% female, 52% frail). Spearman correlation coefficients found no significant associations of platelet aggregation with chronological age or with frailty score. Comparison between frail and non-frail groups showed that there was no impact of frailty status on aggregation assays amongst participants who were not taking any antiplatelet drugs. Amongst participants taking aspirin, the frail had higher adjusted arachidonic acid agonist (ASPI) test measures (AU per platelet) than the non-frail (0.11 ± 0.11 vs. 0.05 ± 0.04; p = 0.04), suggesting that in frail participants, platelet aggregation is less responsive to aspirin than in non-frail.

CONCLUSIONS

We found no effect of chronological age or frailty status on platelet aggregation amongst older patients with atrial fibrillation in this pilot study. However, frailty could be associated with reduced aspirin responsiveness among older patients with atrial fibrillation.

Reduced aspirin responsiveness as assessed by impedance aggregometry is not associated with adverse outcome after cardiac surgery in a small low-risk cohort

Reduced aspirin responsiveness (i.e. persistent high platelet reactivity in platelet function testing) might be associated with increased risk of myocardial ischemia and cardiac mortality in patients with coronary disease. However, the impact in patients undergoing coronary artery bypass grafting (CABG) is unclear. The aim of this prospective cohort study was to evaluate the predictive value of reduced aspirin responsiveness on cardiac and thromboembolic events in patients undergoing elective isolated CABG surgery with aspirin intake until at least two days before surgery. We included 304 patients in this prospective single-center cohort study. Impedance platelet aggregometry (Multiplate®) was performed directly before and on the first day after surgery. Reduced aspirin responsiveness was defined as area under the curve in ASPItest (AUCASPI) ≥300 U. The primary outcome was a composite of all-cause mortality and/or major adverse cardiac or thromboembolic events within 1 year. Reduced aspirin responsiveness was found in 13 and 24% of patients pre and postoperatively, respectively. There was no difference in the outcomes between patients with normal and reduced aspirin responsiveness in the preoperative measurement (log-rank test, p = 0.540). Multivariate analysis including logistic EuroSCORE I and postoperative troponin T levels did not show any association of reduced aspirin responsiveness with adverse outcome (hazard ratio, 0.576; (95% CI 0.128-2.585; p = 0.471). Similarly, postoperative reduced aspirin responsiveness was not associated with adverse events. To conclude, reduced aspirin responsiveness as evaluated by Multiplate® platelet function analyzer was not associated with increased incidence of major adverse cardiac and thromboembolic events and mortality after CABG surgery.

Preoperative cardiovascular evaluation in patients undergoing vascular surgery

Vascular surgery is associated with a higher incidence of perioperative cardiovascular morbidity and mortality compared with other noncardiac surgeries. Patients undergoing vascular surgery represent a higher-risk population, usually because of the presence of generalized arterial disease and multiple comorbidities. The overwhelming perioperative cardiac event is myocardial infarction. This article offers a tailored approach to preoperative cardiovascular management for patients undergoing vascular surgery. The use and limitations of well-established guidelines and clinical risk indices for patients undergoing noncardiac surgery are described as it pertains to vascular surgery in particular. Furthermore, the role and benefit of noninvasive stress testing, coronary revascularization, and medical therapy before vascular surgery are discussed.

Preoperative optimization of the vascular surgery patient

It is well known that patients who suffer from peripheral (noncardiac) vascular disease often have coexisting atherosclerotic diseases of the heart. This may leave the patients susceptible to major adverse cardiac events, including death, myocardial infarction, unstable angina, and pulmonary edema, during the perioperative time period, in addition to the many other complications they may sustain as they undergo vascular surgery procedures, regardless of whether the procedure is performed as an open or endovascular modality. As these patients are at particularly high risk, up to 16% in published studies, for postoperative cardiac complications, many proposals and algorithms for perioperative optimization have been suggested and studied in the literature. Moreover, in patients with recent coronary stents, the risk of non-cardiac surgery on adverse cardiac events is incremental in the first 6 months following stent implantation. Just as postoperative management of patients is vital to the outcome of a patient, preoperative assessment and optimization may reduce, and possibly completely alleviate, the risks of major postoperative complications, as well as assist in the decision-making process regarding the appropriate surgical and anesthetic management. This review article addresses several tools and therapies that treating physicians may employ to medically optimize a patient before they undergo noncardiac vascular surgery.