Controversies in Oral Antiplatelet Therapy in Patients Undergoing Aortocoronary Bypass Surgery

Variation in Practice Regarding Pretreatment With Dual Antiplatelet Therapy for Patients With Non-ST Elevation Myocardial Infarction

BACKGROUND

Despite guideline recommendations, a significant number of patients with non-ST elevation myocardial infarction (NSTEMI) do not receive dual antiplatelet therapy (DAPT) before angiography "pretreatment." While there may be valid clinical reasons to not pretreat, such as concern for bleeding or multivessel disease warranting coronary artery bypass graft surgery, the degree of variability and factors associated with DAPT pretreatment are unknown.

METHODS AND RESULTS

From the multicenter TRIUMPH registry, 1632 NSTEMI patients were not taking DAPT on admission and were included in the study cohort. Among the study patients, only 22% patients received DAPT pretreatment. A multivariable logistic regression model showed that race other than white or black (odds ratio [OR] 0.41, 95% CI 0.21-0.83), hemoglobin level (OR 1.18, 95% CI 1.08-1.29), patients' bleeding risk (assessed with NCDR CathPCI Bleeding Risk Score) (OR 0.85, 95% CI 0.74-0.99), and severe left ventricular dysfunction (OR 0.3, 95% CI 0.13-0.65) were the main predictors of pretreatment with DAPT, whereas likelihood of needing coronary artery bypass graft surgery (GRACE prediction model) was not (OR 1.09, 95% CI 0.88-1.35). Median ORs were calculated to assess variability of receiving DAPT pretreatment across sites after adjustment for patient characteristics. Receiving DAPT pretreatment varied substantially across sites (range 0-100%, mean OR 3.94, P<0.0001).

CONCLUSIONS

While deviating from guideline-recommended DAPT pretreatment in patients with NSTEMI was associated with patient factors (eg, bleeding risk), marked variation was present across sites after accounting for patient-level characteristics. This suggests that site-level interventions are needed to improve concordance with current guidelines.

Adenosine diphosphate-induced single-platelet count aggregation and bleeding in clopidogrel-treated patients undergoing coronary artery bypass grafting

OBJECTIVES

To investigate the association between adenosine diphosphate (ADP)-induced platelet aggregation measured by single-platelet count testing and postoperative blood loss in clopidogrel-treated patients with acute coronary syndromes undergoing coronary artery bypass grafting (CABG).

DESIGN

Prospective observational study.

SETTING

Clinical study in one cardiac surgery center.

PARTICIPANTS

Eighty-eight patients treated with clopidogrel (300-600 mg loading dose followed by 75 mg daily) within 7 days before CABG.

INTERVENTIONS

Platelet function was assessed preoperatively by single-platelet count ADP-induced platelet aggregation. Postoperative blood loss and transfusion requirements were recorded.

MEASUREMENTS AND MAIN RESULTS

There was no significant association between ADP-induced platelet aggregation and blood loss 12 hours postoperatively (estimate -7.51; 95% confidence interval [CI]: -16.9-1.9; p = 0.12). ADP-induced platelet aggregation was associated significantly with the number of platelet concentrates administered within 24 hours after surgery (incidence rate ratio [IRR] 0.95; 95% CI: 0.92-0.98; p<0.01), but not to the number of packed red blood cells (IRR 0.98; 95% CI: 0.95-1.01; p = 0.14).

CONCLUSIONS

Preoperative ADP-induced platelet aggregation measured by single-platelet count testing in clopidogrel-treated patients with acute coronary syndromes undergoing CABG was not associated with postoperative blood loss or packed red blood cells transfused, but was associated significantly with number of platelet concentrates administered during the initial 24 postoperative hours.

Does Dual Antiplatelet Therapy Affect Blood Loss and Transfusion Requirements in Robotic-Assisted Coronary Artery Surgery?

Objective

Patients who present for coronary surgery often receive preoperative dual antiplatelet therapy with aspirin and a thienopyridine derivative (clopidogrel or prasugrel), especially after a recent acute coronary syndrome. Studies have shown that patients on aspirin and clopidogrel are at increased risk for perioperative bleeding and related events. We sought to examine the impact of dual antiplatelet therapy on bleeding and transfusion requirements in patients undergoing robotic-assisted minimally invasive coronary artery bypass grafting.

Methods

From January 2010 to November 2011, a total of 110 patients underwent robotic-assisted off-pump coronary surgery at our institution. All patients underwent robotic-assisted harvest of the left internal mammary artery from the chest wall. Some patients then underwent direct coronary anastomosis to the left anterior descending coronary artery via a left minithoracotomy, whereas others had a complete robotic endoscopic procedure within the closed chest. The patients were divided into two groups for outcome analysis on the basis of preoperative antiplatelet therapy: group 1 (either aspirin alone or no antiplatelet agents at all; n = 53) and group 2 (aspirin plus clopidogrel or prasugrel; n = 57).

Results

Perioperative chest tube drainage was not significantly different between the patient groups, irrespective of the preoperative antiplatelet agents used. Transfusion requirements and other morbidities were also similar in both groups of patients.

Conclusions

Preoperative dual antiplatelet therapy does not result in significantly increased bleeding or perioperative transfusion requirements. If clinically indicated, it is reasonable to continue preoperative combination antiplatelet therapy in patients undergoing robotic-assisted coronary surgery.

Antiplatelet drugs: mechanisms and risks of bleeding following cardiac operations

Preoperative antiplatelet drug use is common in patients undergoing coronary artery bypass grafting (CABG). The impact of these drugs on bleeding and blood transfusion varies. We hypothesize that review of available evidence regarding drug-related bleeding risk, underlying mechanisms of platelet dysfunction, and variations in patient response to antiplatelet drugs will aid surgeons as they assess preoperative risk and attempt to limit perioperative bleeding. The purpose of this review is to (1) examine the role that antiplatelet drugs play in excessive postoperative blood transfusion, (2) identify possible mechanisms to explain patient response to antiplatelet drugs, and (3) formulate a strategy to limit excessive blood product usage in these patients. We reviewed available published evidence regarding bleeding risk in patients taking preoperative antiplatelet drugs. In addition, we summarized our previous research into mechanisms of antiplatelet drug-related platelet dysfunction. Aspirin users have a slight but significant increase in blood product usage after CABG (0.5 U of nonautologous blood per treated patient). Platelet adenosine diphosphate (ADP) receptor inhibitors are more potent antiplatelet drugs than aspirin but have a half-life similar to aspirin, around 5 to 10 days. The American Heart Association/American College of Cardiology and the Society of Thoracic Surgeons guidelines recommend discontinuation, if possible, of ADP inhibitors 5 to 7 days before operation because of excessive bleeding risk, whereas aspirin should be continued during the entire perioperative period in most patients. Individual variability in response to aspirin and other antiplatelet drugs is common with both hyper- and hyporesponsiveness seen in 5 to 25% of patients. Use of preoperative antiplatelet drugs is a risk factor for increased perioperative bleeding and blood transfusion. Point-of-care tests can identify patients at high risk for perioperative bleeding and blood transfusion, although these tests have limitations. Available evidence suggests that multiple blood conservation techniques benefit high-risk patients taking antiplatelet drugs before operation. Guidelines for patients who take aspirin and/or thienopyridines before cardiac procedures include some or all of the following: (1) preoperative identification of high-risk patients using point-of-care testing; (2) withdrawal of aspirin or other antiplatelet drugs for a few days and delay of operation in patients at high risk for bleeding if clinical circumstances permit; (3) selective perioperative use of evidence-based blood conservation interventions (e.g., short-course erythropoietin, off-pump procedures, and use of intraoperative blood conservation techniques), especially in high-risk patients; and (4) platelet transfusions if clinical bleeding occurs.

Management of the clotting system: a European perspective

PURPOSE OF REVIEW

Coagulation management remains a challenge for anesthesiologists involved in cardiovascular surgery as the population undergoing surgery becomes older and presents with more comorbidities. These patients are frequently treated with one or more agents that directly affect coagulation. This review will discuss what is known and the treatments available to manage coagulation in the perioperative setting of cardiac surgery.

RECENT FINDINGS

New antithrombotics will be discussed as well as their proposed substitution in the preoperative period. The review will also describe the different products available in Europe for the treatment of bleeding and coagulopathy. Finally, the use of new monitoring devices will be discussed.

SUMMARY

The introduction of new drugs with different mechanisms of action adds to the complexity of coagulation management during cardiovascular surgery. Monitoring needs to be developed and improved, especially for evaluating platelet function.

Platelet function measurement-based strategy to reduce bleeding and waiting time in clopidogrel-treated patients undergoing coronary artery bypass graft surgery: the timing based on platelet function strategy to reduce clopidogrel-associated bleeding related to CABG (TARGET-CABG) study

BACKGROUND

Aspirin and clopidogrel therapy is associated with a variable bleeding risk in patients undergoing coronary artery bypass graft surgery (CABG). We evaluated the role of platelet function testing in clopidogrel-treated patients undergoing CABG.

METHODS AND RESULTS

One hundred eighty patients on background aspirin with/without clopidogrel therapy undergoing elective first time isolated on-pump CABG were enrolled in a prospective single-center, nonrandomized, unblinded investigation (Timing Based on Platelet Function Strategy to Reduce Clopidogrel-Associated Bleeding Related to CABG [TARGET-CABG] study) between September 2008 and January 2011. Clopidogrel responsiveness (ADP-induced platelet-fibrin clot strength [MA(ADP)]) was determined by thrombelastography; CABG was done within 1 day, 3-5 days, and >5 days in patients with an MA(ADP) >50 mm, 35-50 mm, and <35 mm, respectively. The primary end point was 24-hour chest tube drainage and key secondary end point was total number of transfused red blood cells. Equivalence was defined as ≤25% difference between groups. ANCOVA was used to adjust for confounders. Mean 24-hour chest tube drainage in clopidogrel-treated patients was 93% (95% confidence interval, 81-107%) of the amount observed in clopidogrel-naive patients, and the total amount of red blood cells transfused did not differ between groups (1.80 U versus 2.08 U, respectively, P=0.540). The total waiting period in clopidogrel-treated patients was 233 days (mean, 2.7 days per patient).

CONCLUSIONS

A strategy based on preoperative platelet function testing to determine the timing of CABG in clopidogrel-treated patients was associated with the same amount of bleeding observed in clopidogrel-naive patients and ≈50% shorter waiting time than recommended in the current guidelines.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00857155.

Coronary artery bypass graft surgery in acute coronary syndrome: incidence, cost impact, and acute clopidogrel interruption

BACKGROUND

Guidelines stipulate that clopidogrel should be interrupted ≥ 5 days prior to elective coronary artery bypass graft (CABG) surgery to reduce the risk of bleeding unless the need for revascularization and/or the net benefit of the clopidogrel outweighs the potential risks of bleeding. This study describes real-world patterns of acute clopidogrel use, CABG surgery, and inpatient costs among patients with acute coronary syndrome (ACS).

METHODS

The study used the MarketScan® Commercial, Medicare Supplemental, and Hospital Drug databases, comprising health care data for > 63 million individuals in the United States. Acute coronary syndrome episodes, defined as hospitalizations for ACS (primary International Classification of Diseases, Ninth Revision, Clinical Modification codes 410.xx, 411.1x) occurring between January 1, 2005 and June 30, 2009, were identified from patients aged ≥ 18 years. Outcomes included cost of and length of stay (LOS) for ACS episodes and, among patients experiencing ACS episodes treated with acute clopidogrel administration followed by CABG surgery, the duration of clopidogrel interruption prior to CABG surgery. Analyses were descriptive.

RESULTS

A total of 160 168 ACS episodes were identified, and the mean patient age was 63.5 years. Coronary artery bypass graft surgery episodes comprised 9.3% (14 896 of 160 168) of all ACS episodes. The mean LOS was 9.8 (standard deviation [SD], 6.8) days per CABG surgery episode, and mean inpatient costs were $71 140 (SD, $68 012) per CABG surgery episode. Among patients experiencing ACS episodes with inpatient drug data and to whom acute clopidogrel was administered followed by CABG surgery (n = 8101), the mean duration of clopidogrel interruption was 3.3 (SD, 2.6) days, and the majority (62.1%) of these patients underwent surgery within 1 to 3 days after their last acute clopidogrel dose. The mean incremental increase in inpatient costs associated with 1 extra LOS day was $1991.

CONCLUSION

Coronary artery bypass graft surgery is used relatively infrequently among patients who experience ACS episodes. When CABG surgery is performed in a real-world setting, the majority or procedures are performed < 5 days after the last acute clopidogrel dose. However, among patients for whom urgent CABG surgery is not indicated, withholding CABG surgery to allow for clopidogrel interruption may only minimally affect inpatient costs and must be considered in the broader context of patient management.

Earlier recovery of platelet function after discontinuation of treatment with ticagrelor compared with clopidogrel in patients with high antiplatelet responses

BACKGROUND

The rate of recovery of platelet function after discontinuation of P2Y(12) inhibitors depends on the reversibility of the antiplatelet effect and the extent of the on-treatment response. P2Y(12) inhibition increases the bleeding risk in patients requiring surgery.

OBJECTIVES

To evaluate recovery of platelet function after discontinuation of ticagrelor vs. clopidogrel in stable coronary artery disease (CAD) patients with high levels of platelet inhibition (HPI) during the ONSET/OFFSET study.

METHODS

Patients received aspirin 75-100 mg per day and either ticagrelor 90 mg twice-daily or clopidogrel 75 mg daily for 6 weeks. This subanalysis included patients with HPI after the last dose of maintenance therapy, defined as: inhibition of platelet aggregation (IPA) > 75% 4 h post-dose (ADP 20 μm, final extent); < 120 P2Y(12) reaction units 8 h post-dose (VerifyNow P2Y(12) assay); or platelet reactivity index < 50% 8 h post-dose (VASP-P assay).

RESULTS

IPA > 75% was observed in 39 out of 47 ticagrelor-treated and 17 out of 44 clopidogrel-treated patients. The rate of offset of IPA over 4-72 h was greater with ticagrelor (IPA %/hour slope: -1.11 vs. -0.67 for clopidogrel; P < 0.0001). Mean IPA was significantly lower with ticagrelor than clopidogrel between 48 and 168 h post-dose (P < 0.01). Similar findings were observed with the other assays. The average time for IPA to decline from 30% to 10% was 50.8 h with ticagrelor vs. 110.4 h with clopidogrel.

CONCLUSIONS

In patients with HPI, recovery of platelet function was more rapid after discontinuation of ticagrelor than clopidogrel leading to significantly greater platelet reactivity by 48 h after the last dose in the ticagrelor group.

2011 update to the Society of Thoracic Surgeons and the Society of Cardiovascular Anesthesiologists blood conservation clinical practice guidelines

BACKGROUND

Practice guidelines reflect published literature. Because of the ever changing literature base, it is necessary to update and revise guideline recommendations from time to time. The Society of Thoracic Surgeons recommends review and possible update of previously published guidelines at least every three years. This summary is an update of the blood conservation guideline published in 2007.

METHODS

The search methods used in the current version differ compared to the previously published guideline. Literature searches were conducted using standardized MeSH terms from the National Library of Medicine PUBMED database list of search terms. The following terms comprised the standard baseline search terms for all topics and were connected with the logical 'OR' connector--Extracorporeal circulation (MeSH number E04.292), cardiovascular surgical procedures (MeSH number E04.100), and vascular diseases (MeSH number C14.907). Use of these broad search terms allowed specific topics to be added to the search with the logical 'AND' connector.

RESULTS

In this 2011 guideline update, areas of major revision include: 1) management of dual anti-platelet therapy before operation, 2) use of drugs that augment red blood cell volume or limit blood loss, 3) use of blood derivatives including fresh frozen plasma, Factor XIII, leukoreduced red blood cells, platelet plasmapheresis, recombinant Factor VII, antithrombin III, and Factor IX concentrates, 4) changes in management of blood salvage, 5) use of minimally invasive procedures to limit perioperative bleeding and blood transfusion, 6) recommendations for blood conservation related to extracorporeal membrane oxygenation and cardiopulmonary perfusion, 7) use of topical hemostatic agents, and 8) new insights into the value of team interventions in blood management.

CONCLUSIONS

Much has changed since the previously published 2007 STS blood management guidelines and this document contains new and revised recommendations.

Early clopidogrel use in non-ST elevation acute coronary syndrome and subsequent coronary artery bypass grafting

Clopidogrel use is associated with a significant decrease in major adverse cardiac events when used in patients with non-ST elevation acute coronary syndromes (NSTE-ACS), and guidelines give a class I level of evidence A recommendation for the use of clopidogrel in these patients. The optimal timing of clopidogrel use has not been conclusively determined, but nearly all data available support early use in patients with NSTE-ACS. Despite this, clopidogrel usage is far less than expected based on current guidelines because of concern for bleeding at the time of possible subsequent coronary artery bypass grafting (CABG). Clopidogrel use has been associated with increased perioperative bleeding at the time of CABG, but data are mixed. Numerous studies have conclusively shown that this bleeding risk is confined to those patients receiving clopidogrel within 5 days of CABG. The absolute number of patients exposed to this possible bleeding risk is very small relative to the >1 million patients who present annually with NSTE-ACS and is estimated to be <0.8% of these patients. Recent data have shown that (1) holding clopidogrel for 5 days before CABG is safe in patients with NSTE-ACS and (2) clopidogrel use in patients with NSTE-ACS decreases ischemic events in patients referred for CABG compared to patients who are not given clopidogrel. These data strongly challenge the notion that clopidogrel should be withheld until it is determined if the patient will be referred for CABG.