Progression of the culprit lesion in unstable coronary artery disease with warfarin and aspirin versus aspirin alone: preliminary study

High platelet reactivity – the challenge of prolonged anticoagulation therapy after ACSI

Despite dual antiplatelet therapy (DAPT), one-year event rates after acute coronary syndrome (ACS) vary from 9–12%. The development of novel oral anticoagulants (NOAC) without a need for monitoring has initiated renewed interest for prolonged adjunctive anticoagulation. Importantly, the cornerstone of treatment after ACS consists of long-term DAPT. In that context, the NOACs have only been tested as adjunctive therapy. Of all new agents, only rivaroxaban –in a substantially lower dose than used for atrial fibrillation– has been demonstrated to improve outcome, albeit at the cost of bleeding. In selected cases, adjunctive therapy with dose-adjusted vitamin-K antagonists (international normalized ratio [INR] 2.0–3.0) can be considered as well. These two strategies of prolonged anticoagulation can be considered in case of ‘high platelet reactivity’, i.e. in patients at high risk of recurrent thrombotic events despite DAPT. Both during admission and after discharge for ACS, the use of NOACs in doses indicated for atrial fibrillation is strictly contra-indicated in patients on DAPT. In case of post-discharge anticoagulation therapy for atrial fibrillation, patients should preferably receive vitamin-K antagonists (INR 2.0–3.0), with discontinuation of one antiplatelet agent as soon as clinically justifiable. Importantly, the impact of prolonged anticoagulation (low-dose rivaroxaban, vitamin-K antagonists) as adjunctive to DAPT after ACS has not been addressed with the most potent antiplatelet agents (prasugrel, ticagrelor) and merits further study. Despite the potential indication of prolonged oral anticoagulation as adjunctive treatment, it remains to be established whether anticoagulation therapy could also be an alternative for either aspirin or thienopyridine treatment in selected ACS patients on DAPT.

Efficacy and safety of aspirin combined with warfarin after acute coronary syndrome : A meta-analysis

A comprehensive meta-analysis was performed to investigate whether the combination of high-/low-dose of aspirin and various intensities of warfarin (W) offer greater benefit than aspirin (ASA) alone. A total of 14 randomized clinical trials (RCTs) having 26,916 patients with acute coronary syndrome (ACS) met inclusion criteria. The efficacy and safety of all outcomes which included myocardial infarction (MI), all-cause death, stroke, and bleeding were calculated. The overall outcomes analysis showed there was no significant difference in the risk of MI (relative ratio [RR] 0.959, 95 % confidence interval [CI] 0.78-1.04, P = 0.308), stroke (RR 0.789, 95 % CI 0.57-1.09, P = 0.145), and all-cause death (RR 1.007, 95 % CI 0.93-1.09, P = 0.87) between the combination group and ASA group. The subgroup analysis suggested that ASA (≤100 mg/day) plus W (mean international normalized ratio [INR] 2.0-3.0) decreased the risk rate of stroke (RR 0.660, 95 % CI 0.50-0.87, P = 0.003). There was a lower risk of MI (RR 0.605, 95 % CI 0.47-0.77, P < 0.0001) as well as stroke (RR 0.594, 95 % CI 0.45-0.79, P < 0.0001) between W (INR 2.0-3.0) combined with ASA (mean dose ≥100 mg/day) and ASA. However, the risk of major bleeding (RR 1.738, 95 % CI 1.45-2.08, P < 0.0001) and minor bleeding (RR 2.767, 95 % CI 2.12-3.61, P < 0.0001) was almost doubled in the combined groups. Compared with ASA, high-dose aspirin with moderate-intensity warfarin (INR 2.0-3.0) may better reduce the risk of MI and stroke but confer an increased risk of bleeding.

Potential role of oral anticoagulants in the treatment of patients with coronary artery disease: focus on dabigatran

The pharmacologic management of patients with high-risk coronary artery disease consists of aspirin and a P2Y12 receptor inhibitor. Chronic oral anticoagulation with warfarin is the major treatment strategy to attenuate thromboembolism or stroke in patients with deep vein thrombosis, pulmonary embolism, heart failure and atrial fibrillation. A substantial percentage of the latter group of patients have coronary artery disease and may require stenting with long-term dual antiplatelet therapy in addition to therapy with warfarin to reduce arterial ischemic events in addition to stroke. These new oral anticoagulants have been developed for long-term therapy to overcome the limitations of warfarin. Dabigatran is a direct thrombin inhibitor and its role in patients with acute coronary syndrome is being explored.

Low-dose of oral factor Xa inhibitors in patients with a recent acute coronary syndrome: a systematic review and meta-analysis of randomized trials

BACKGROUND

Recently, randomized controlled trials (RCTs) have shown that therapy with new oral activated factor X (Xa) inhibitors in acute coronary syndrome (ACS) yielded a reduction of ischemic events. However, this therapy was associated with a dose-related increase in major bleeding complications. We aimed to perform a systematic review and meta-analysis to appraise the clinical efficacy and safety of the lowest doses of oral factor Xa inhibitors compared with placebo in patients after a recent ACS.

METHODS

The primary endpoint was cardiovascular mortality. The rate of new myocardial infarction (MI) was the secondary efficacy endpoint, whereas major bleeding complications were recorded as a safety endpoint. Five RCTs were included in the meta-analysis enrolling a total of 25,643 patients.

RESULTS

There was no significant difference in mortality between patients treated with new antithrombotics compared with those receiving the standard therapy: odds ratio (OR), [95% confidence interval (CI)] = 0.97 [0.72-1.31], p = 0.86. Recurrent MI rates were decreased in the anti-Xa group: OR [95%CI] = 0.86 [0.76-0.98], p = 0.02, number needed to treat (NNT) = 189. The administration of new oral anticoagulants was associated with a strongly increased risk of major bleedings compared with the standard treatment: OR [95%CI] = 3.24 [2.29-4.59], p < 0.001, number needed to harm (NNH) = 104; similarly, intracranial bleeding rates were significantly higher in the anti-Xa arm.

CONCLUSIONS

The addition of the new oral anticoagulants on top of standard therapy in the setting of ACS results in an excessive risk of major bleedings without any clear evidence of outweighing clinical benefits.

Potential role of rivaroxaban in patients with acute coronary syndrome

Patients with acute coronary syndrome (ACS) continue to be at risk for recurrent ischemic events, despite an early invasive strategy and the use of dual antiplatelet therapy. The anticoagulant pathway remains activated for a prolonged period after ACS and, consequently, has been a target for treatment. Early studies with warfarin indicated its benefit, but the risk of bleeding and the complexities of warfarin anticoagulation resulted in little use of this strategy. Rivaroxaban, apixaban, and dabigatran are new specific inhibitors of anticoagulant factors (Xa or IIa) currently available for the prevention of thrombosis and/or thromboembolism. Thus far, studies with dabigatran and apixaban in ACS have shown no clinical benefit and bleeding has been increased. The ATLAS ACS 2-TIMI 51 trial observed the impact of rivaroxaban 2.5 mg and 5 mg twice daily in patients with recent ACS receiving current management (both early invasive strategy and dual antiplatelet therapy with aspirin and clopidogrel) over a follow-up period of over 1 year. Rivaroxaban 2.5 mg twice daily reduced cardiovascular death, myocardial infarction, or stroke by 16%, and both cardiovascular and all-cause mortality by approximately 20%. Although major bleeding increased from 0.6% to 2.1% and intracranial hemorrhage from 0.2% to 0.6%, there was no increase in fatal bleeding. The role of rivaroxaban in the management of ACS is discussed in this review. The reduction in mortality is the main finding that could lead to the use of rivaroxaban in the management of ACS in high-risk individuals with a low bleeding risk.

Low doses of acetylsalicylic acid increase risk of gastrointestinal bleeding in a meta-analysis

BACKGROUND & AIMS

We performed a meta-analysis of data from randomized trials to estimate the risk of all-cause mortality and bleeding (and especially gastrointestinal [GI] bleeding) in patients treated with low doses of acetylsalicylic acid (ASA) (75-325 mg/d), alone or in combination with other medications.

METHODS

We searched 10 electronic databases (until October 2010) and collected data on adverse events in randomized controlled studies that evaluated low doses of ASA, alone (35 trials) or in combination with anticoagulants (18 trials), clopidogrel (5 trials), or proton pump inhibitors (PPIs; 3 trials). We analyzed data using random-effects meta-analysis and meta-regression, applying Peto's odds ratio (OR) for adverse events.

RESULTS

Low doses of ASA alone decreased the risk for all-cause mortality (relative risk, 0.93, 95% confidence interval [CI], 0.87-0.99), largely because of effects in secondary prevention populations. The risk of major GI bleeding increased with low doses of ASA alone (OR, 1.55; 95% CI, 1.27-1.90), compared with inert control reagents. The risk increased when ASA was combined with clopidogrel, compared with aspirin alone (OR, 1.86; 95% CI, 1.49-2.31), anticoagulants vs low doses of ASA alone (OR, 1.93; 95% CI, 1.42-2.61), or in studies that included patients with a history of GI bleeding or of longer duration. Importantly, PPI use reduced the risk for major GI bleeding in patients given low doses of ASA (OR, 0.34; 95% CI, 0.21-0.57).

CONCLUSIONS

In a meta-analysis, low doses of ASA increased the risk for GI bleeding; risk increased with accompanying use of clopidogrel and anticoagulant therapies, but decreased in patients who took PPIs.

Rivaroxaban versus placebo in patients with acute coronary syndromes (ATLAS ACS-TIMI 46): a randomised, double-blind, phase II trial

BACKGROUND

Rivaroxaban is an oral direct factor Xa inhibitor that has been effective in prevention of venous thromboembolism in patients undergoing elective orthopaedic surgery. However, its use after acute coronary syndromes has not been investigated. In this setting, we assessed the safety and efficacy of rivaroxaban and aimed to select the most favourable dose and dosing regimen.

METHODS

In this double-blind, dose-escalation, phase II study, undertaken at 297 sites in 27 countries, 3491 patients stabilised after an acute coronary syndrome were stratified on the basis of investigator decision to use aspirin only (stratum 1, n=761) or aspirin plus a thienopyridine (stratum 2, n=2730). Participants were randomised within each strata and dose tier with a block randomisation method at 1:1:1 to receive either placebo or rivaroxaban (at doses 5-20 mg) given once daily or the same total daily dose given twice daily. The primary safety endpoint was clinically significant bleeding (TIMI major, TIMI minor, or requiring medical attention); the primary efficacy endpoint was death, myocardial infarction, stroke, or severe recurrent ischaemia requiring revascularisation during 6 months. Safety analyses included all participants who received at least one dose of study drug; efficacy analyses were by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00402597.

FINDINGS

Three patients in stratum 1 and 26 in stratum 2 never received the study drug. The risk of clinically significant bleeding with rivaroxaban versus placebo increased in a dose-dependent manner (hazard ratios [HRs] 2.21 [95% CI 1.25-3.91] for 5 mg, 3.35 [2.31-4.87] for 10 mg, 3.60 [2.32-5.58] for 15 mg, and 5.06 [3.45-7.42] for 20 mg doses; p<0.0001). Rates of the primary efficacy endpoint were 5.6% (126/2331) for rivaroxaban versus 7.0% (79/1160) for placebo (HR 0.79 [0.60-1.05], p=0.10). Rivaroxaban reduced the main secondary efficacy endpoint of death, myocardial infarction, or stroke compared with placebo (87/2331 [3.9%] vs 62/1160 [5.5%]; HR 0.69, [95% CI 0.50-0.96], p=0.0270). The most common adverse event in both groups was chest pain (248/2309 [10.7%] vs 118/1153 [10.2%]).

INTERPRETATION

The use of an oral factor Xa inhibitor in patients stabilised after an acute coronary syndrome increases bleeding in a dose-dependent manner and might reduce major ischaemic outcomes. On the basis of these observations, a phase III study of low-dose rivaroxaban as adjunctive therapy in these patients is underway.

FUNDING

Johnson & Johnson Pharmaceutical Research & Development and Bayer Healthcare AG.

Prolonged anticoagulation therapy adjunctive to aspirin after successful fibrinolysis: from early reduction in reocclusion to improved long-term clinical outcome

BACKGROUND

Long-term addition of antithrombotics (clopidogrel, anticoagulants) to aspirin has improved outcome after acute coronary syndromes. Data on the impact after fibrinolysis are scarce. In Antithrombotics in the Prevention of Reocclusion In COronary Thrombolysis-2 (APRICOT-2), adjunctive moderate-intensity coumarin (median international normalized ratio 2.6) conferred a marked reduction in 3-month reocclusion and ischemic events. Given the association between reocclusion and long-term outcome, we performed long-term clinical follow-up.

METHODS

Patients with thrombolysis in myocardial infarction (TIMI) 3 flow <48 hours after fibrinolysis for ST-elevation myocardial infarction were randomized to aspirin plus coumarin, with prolonged heparinization until the target international normalized ratio (2-3) was reached, or aspirin with standard heparinization. Three-month follow-up angiography (reocclusion rates 15% vs 28%) and long-term clinical follow-up (median 7.3 years, interquartile range 5.9-8.6 years) were performed.

RESULTS

Patients randomized to adjunctive anticoagulation (n = 123) received coumarin for a median of 280 days (113-387 days). Survival was 94% versus 88% in patients on aspirin alone (n = 128, P = .12). Infarct-free survival was 86% versus 71% (P = .01). Thrombolysis in myocardial infarction bleeding was 4% in both groups. Patients with reocclusion had impaired survival: 80% versus 94% (P < .01). In a multivariable model without reocclusion, combination therapy independently predicted survival (hazard ratio [HR] 0.36, 95% confidence interval [CI] 0.13-1.00) and infarct-free survival (HR 0.51, 95% CI 0.28-0.95). When adjusted for reocclusion, combination therapy did not predict outcome. Reocclusion independently predicted death (HR 2.56, 95% CI 1.02-6.43) and reinfarction.

CONCLUSIONS

Moderate-intensity oral anticoagulation added to aspirin improved 8-year clinical outcome after successful fibrinolysis. The beneficial effect was largely attributed to a reduction in reocclusion, which independently predicted death and reinfarction. This study provides a mechanistic rationale for prolonged adjunctive anticoagulation after fibrinolysis.

Intravascular ultrasound predictors of major adverse cardiac events in patients with unstable angina

BACKGROUND

Intravascular ultrasound (IVUS) predictors of native culprit lesion morphology for occurrence of major adverse cardiac events (MACE) have not been reported. Moreover, the published data on IVUS predictors of restenosis include patients with stable and unstable angina, although the development and progression of atherosclerosis related to unstable coronary syndrome is different from that of stable angina.

HYPOTHESIS

This study investigated whether IVUS-derived qualitative and quantitative parameters of native (preangioplastic) plaque morphologic features can predict major adverse cardiac events in patients with unstable angina.

METHODS

Clinical (age, gender, coronary risk factors), qualitative and quantitative angiographic (lesion localization, morphology, pre- and postangioplastic minimal lumen diameter, reference diameter, and percent diameter stenosis), and IVUS variables (soft/fibrocalcific plaque, calcification, presence of thrombus or plaque disruption, different types of arterial remodeling, pre- or postangioplastic minimal lumen, external elastic membrane and plaque cross-sectional area, and plaque burden of the target lesion and reference segments) were analyzed by regression analyses using the Cox model, assuming proportional hazards.

RESULTS

Of 60 consecutively enrolled patients, 21 suffered from MACE, while 39 remained event-free during the followup period. Multivariate regression analyses revealed that the presence of adaptive remodeling [p = 0.0177, risk ratio (RR) = 3.108, with 95% confidence interval (CI) = 1.371-8.289] and the preangioplastic lumen cross-sectional area (p = 0.0130, RR = 0.869, with 95% CI = 0.667-0.913) are independent predictors of MACE during follow-up, as is postangioplastic angiographic minimal lumen diameter (p = 0.0330, RR = 0.715 with 95% CI = 0.678-0.812).

CONCLUSIONS

Adaptive remodeling and preangioplastic lumen cross-sectional area determined by IVUS and postangioplastic minimal lumen diameter calculated by quantitative angiography are significant independent predictors of time-dependent MACE in patients with unstable angina.

Management strategies in unstable coronary artery disease--current problems and future directions. The UCAD Council

Unstable coronary artery disease continues to pose a major challenge to clinicians. The advent of new therapies, such as percutaneous transluminal coronary angioplasty, low-molecular-weight heparins, and glycoprotein IIb/IIIa inhibitors, provides new management options for this indication but also raises new questions with regard to optimal management. Prospective randomized trials with well-defined, long-term outcome measures and a means of identifying which patients will derive most benefit from each treatment, together with a means of rapid and clear dissemination of study results and implications, are required in order to advance the management of unstable coronary artery disease.

Adjusted Indirect Meta-Analysis of Aspirin Plus Warfarin at International Normalized Ratios 2 to 3 Versus Aspirin Plus Clopidogrel After Acute Coronary Syndromes

After acute coronary syndromes, the beneficial effect of aspirin plus clopidogrel (A+C) or aspirin plus dose-adjusted warfarin (A+W) compared with aspirin alone is well established. However, these regimens were never compared. To compare the risk-benefit profile of A+C versus A+W after acute coronary syndromes, major medical databases for randomized controlled trials comparing 1 of these combined approaches versus aspirin alone after an acute coronary syndrome (updated June 2006) were searched. Evaluated end points were major adverse events [MAEs: all-cause death, acute myocardial infarction [AMI], thromboembolic stroke, major bleeds, and overall risk of stroke [hemorrhagic or ischemic]). Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for (1) A+W versus aspirin alone, (2) A+C versus aspirin alone, and (3) A+W versus A+C using adjusted indirect meta-analysis. Thirteen studies were included, totaling 69,741 patients. Ten compared A+W versus aspirin alone and 3 compared A+C versus aspirin alone. Each combined approach yielded a significantly lower risk of MAEs, albeit an increased risk of major bleeds, compared with aspirin alone. No significant difference was found for A+W versus A+C for risk of overall MAEs, death, or AMI. However, A+W versus A+C was associated with a significantly lower risk of thromboembolic stroke (OR 0.53, 95% CI 0.31 to 0.88, number needed to treat 60) and all types of stroke (OR 0.58, 95% CI 0.35 to 0.94, p=0.038), but also with increased risk of major bleeds (OR 1.9, 95% CI 1.2 to 2.8, number needed to harm 300). In conclusion, after an acute coronary syndrome, A+W and A+C are comparable in the prevention of MAEs, death, and AMI compared with aspirin alone. Allocating 100 patients to A+W (at international normalized ratio 2 to 3) with respect to A+C could prevent 17 thromboembolic strokes while causing 3 major bleeds.

Positron autoradiography for intravascular imaging: feasibility evaluation

Approximately 70% of acute coronary artery disease is caused by unstable (vulnerable) plaques with an inflammation of the overlying cap and high lipid content. A rupturing of the inflamed cap of the plaque results in propagation of the thrombus into the lumen, blockage of the artery and acute ischaemic syndrome or sudden death. Morphological imaging such as angiography or intravascular ultrasound cannot determine inflammation status of the plaque. A radiotracer such as 18F-FDG is accumulated in vulnerable plaques due to higher metabolic activity of the inflamed cap and could be used to detect a vulnerable plaque. However, positron emission tomography (PET) cannot detect the FDG-labelled plaques because of respiratory and heart motions, small size and low activity of the plaques. Plaques can be detected using a miniature particle (positron) detector inserted into the artery. In this work, a new detector concept is investigated for intravascular imaging of the plaques. The detector consists of a storage phosphor tip bound to the end of an intravascular catheter. It can be inserted into an artery, absorb the 18F-FDG positrons from the plaques, withdrawn from the artery and read out. Length and diameter of the storage phosphor tip can be matched to the length and the diameter of the artery. Monte Carlo simulations and experimental evaluations of coronary plaque imaging with the proposed detector were performed. It was shown that the sensitivity of the storage phosphor detector to the positrons of 18F-FDG is sufficient to detect coronary plaques with 1 mm and 2 mm sizes and 590 Bq and 1180 Bq activities in the arteries with 2 mm and 3 mm diameters, respectively. An experimental study was performed using plastic tubes with 2 mm diameter filled with an FDG solution, which simulates blood. FDG spots simulating plaques were placed over the surface of the tube. A phosphor tip was inserted into the tube and imaged the plaques. Exposure time was 1 min in all simulations and experiments. Experiments showed that detecting the coronary plaques using the proposed technique is possible. The proposed technique has the potential for fast and accurate detection of vulnerable coronary and other intravascular plaques.

New anticoagulants in ischemic heart disease

Fibrinolysis is the reference treatment for most myocardial infarctions with ST-segment elevation; alternatives are angioplasty, with or without stent. The earlier fibrinolysis is performed (preferably before hospitalization), the more effective it is. It can be optimized by adjuvant antiplatelet therapy, such as aspirin, and probably by anticoagulant treatment as well. Because fibrinolytic therapy is accompanied by intensive thrombin generation and activation, immediate and continuous adjunctive simultaneous heparin therapy is recommended. The efficacy of subcutaneous low-molecular-weight heparin (LMWH) HBPM) is at least equivalent to that of intravenous unfractionated heparin (UFH), but its risk of severe (but not cerebral) hemorrhage is greater. Bolus LMWH on the other hand is associated with an increased risk of cerebral hemorrhage. Antithrombotic treatment thus appears optimal with bolus UFH at fibrinolysis and for at least 48 hours afterwards. An alternative after this bolus might be subcutaneous enoxaparin until discharge. Because the major drawback of both types of heparin is their rebound activation of thrombosis, oral anticoagulants are recommended thereafter. The combination of anticoagulant treatment + (low-dose) aspirin is not superior to aspirin alone when the target INR is below 2. Adequate anticoagulation with INRs greater than 2.0 consistently improves angiographic and clinical outcome. Bleeding (except intracerebral) is significantly increased whether the INR is greater than or less than 2.0. Other treatments are being investigated. Pentasaccharide (anti-Xa) combined with fibrinolysis seems to reduce reocclusion more effectively than UFH. Oral postinfarction treatment with ximelagatran (a thrombin inhibitor), combined with aspirin, is associated with fewer cardiovascular events than aspirin alone. More studies are needed.

Aspirin plus warfarin compared to aspirin alone after acute coronary syndromes: an updated and comprehensive meta-analysis of 25,307 patients

AIMS

In patients recovering from acute coronary syndromes (ACS) the role of oral anticoagulation (and its intensity) in addition to aspirin remains controversial. We conducted a specific meta-analysis of randomized trials comparing aspirin plus warfarin (A+W) with aspirin alone in such patients.

METHODS AND RESULTS

MEDLINE and Cochrane databases yielded 14 (of 148 potentially relevant) articles enrolling 25 307 patients. Follow-up ranged from 3 months to 5 years. Irrespective of International normalized ratio (INR), A+W did not significantly affect the risk of major adverse events (MAE: all cause death, non-fatal myocardial infarction, and non-fatal thrombo-embolic stroke) when compared with aspirin alone [OR 0.96 (0.90-1.03), P=0.30], but increased the risk of major bleeds (MB): OR 1.77 (1.47-2.13), P<0.00001. However, in studies with INR of 2-3, A+W was associated with a significant reduction of MAE [OR 0.73 (0.63-0.84), P<0.0001, number needed to treat to avoid one MAE=33], albeit at an increased risk of MB [OR 2.32 (1.63-3.29), P<0.00001; number needed to harm by causing one MB=100]. In both analyses, intracranial bleeding was not significantly increased by A+W when compared with aspirin alone.

CONCLUSION

For patients recovering from ACS, a combined strategy of A+W at INR values of 2-3 doubles the risk of MB, but is nonetheless superior to aspirin alone in preventing MAE. Whether this combined regimen is also superior to a 'double' anti-platelet strategy or to newer evolving treatments warrants further investigation.

The impact of vitamin K-dependent factor depletion by warfarin on platelet-rich thrombosis after deep arterial injury

Although the central role of thrombin in arterial thrombosis is well established, the efficacy of vitamin K-dependent factor depletion by warfarin at preventing this process has not been established. To assess the efficacy of warfarin in the prevention of arterial thrombosis, two intensities of anticoagulation were compared in a well-characterized porcine model of carotid angioplasty. For 10 days prior to angioplasty, pigs received either high-dose warfarin (n = 9), low-dose warfarin plus aspirin (n = 9), or control tablets (n = 10). Injured arteries were assessed for (111)In-platelet ( x 10(6) cm(-2)) and (125)I-fibrin(ogen) (molecules x 10(12) cm(-2)) deposition and the incidence of macroscopic thrombus. Platelet (30 +/- 7 vs. 332 +/- 137; P = 0.001) and fibrinogen (156 +/- 17 vs. 365 +/- 90; P < 0.05) deposition were significantly reduced in animals receiving high-intensity warfarin whereas low-intensity warfarin/ASA (520 +/- 240 and 1193 +/- 638) was similar to control (P =NS). At the time of angioplasty, the PT-INR and vitamin K-dependent factors varied over a broad range. The greatest reduction of platelet and fibrinogen deposition occurred as the PT-INR increased from 1.0 to 2.2. Increasing the PT-INR beyond 3.0 resulted in little, if any, incremental reduction of either platelet or fibrinogen deposition. Macroscopic thrombus was abolished at PT-INR > 2.2. Despite a broad range of vitamin K factor activities, no single factor was predictive of either platelet or fibrinogen deposition. Warfarin at PT-INR > 2.2 effectively eliminates thrombosis following deep arterial injury. Arterial thrombosis correlates poorly with any single vitamin K-dependent factor but rather appears to be a function of the entire extrinsic coagulation pathway as measured by the PT-INR.

Aspirin plus coumarin versus aspirin alone in the prevention of reocclusion after fibrinolysis for acute myocardial infarction: results of the Antithrombotics in the Prevention of Reocclusion In Coronary Thrombolysis (APRICOT)-2 Trial

BACKGROUND

Despite the use of aspirin, reocclusion of the infarct-related artery occurs in approximately 30% of patients within the first year after successful fibrinolysis, with impaired clinical outcome. This study sought to assess the impact of a prolonged anticoagulation regimen as adjunctive to aspirin in the prevention of reocclusion and recurrent ischemic events after fibrinolysis for ST-elevation myocardial infarction.

METHODS AND RESULTS

At coronary angiography <48 hours after fibrinolytic therapy, 308 patients receiving aspirin and intravenous heparin had a patent infarct-related artery (Thrombolysis In Myocardial Infarction [TIMI] grade 3 flow). They were randomly assigned to standard heparinization and continuation of aspirin alone or to a 3-month combination of aspirin with moderate-intensity coumarin, including continued heparinization until a target international normalized ratio (INR) of 2.0 to 3.0. Angiographic and clinical follow-up were assessed at 3 months. Median INR was 2.6 (25 to 75th percentiles 2.1 to 3.1). Reocclusion (< or =TIMI grade 2 flow) was observed in 15% of patients receiving aspirin and coumarin compared with 28% in those receiving aspirin alone (relative risk [RR], 0.55; 95% CI 0.33 to 0.90; P<0.02). TIMI grade 0 to 1 flow rates were 9% and 20%, respectively (RR, 0.46; 95% CI, 0.24 to 0.89; P<0.02). Survival rates free from reinfarction and revascularization were 86% and 66%, respectively (P<0.01). Bleeding (TIMI major and minor) was infrequent: 5% versus 3% (P=NS).

CONCLUSIONS

As adjunctive to aspirin, a 3-month-regimen of moderate-intensity coumarin, including heparinization until the target INR is reached, markedly reduces reocclusion and recurrent events after successful fibrinolysis. This conceptual study provides a mechanistic rationale to further investigate the role of prolonged anticoagulation after fibrinolytic therapy.

A new paradigm for plaque stabilization

The concept of plaque stabilization was developed to explain how lipid lowering could decrease adverse coronary events without a substantial reduction in the regression of atherosclerosis. Plaques were stabilized by reducing serum cholesterol leading to several favorable pathobiological changes in the vessel wall of lipid-rich plaques responsible for a majority of acute coronary events. However, this concept is limited for several reasons including that it does not incorporate strategies directed against either plaques that have already destabilized or non-lipid-rich plaques, which are the substrate for at least one third of major coronary thrombi and may or may not be stabilized by lipid lowering. For the destabilized plaque with overlying thrombus, either percutaneous intervention, long-term antithrombotic and/or anticoagulant therapy, or possibly aggressive lipid lowering stabilizes lesions by reducing subsequent thrombosis at the lesion site and, at least with lipid lowering, by improving endothelial function and possibly reducing inflammation. Short-term, in-hospital antithrombotic approaches alone with agents like the GP platelet IIb/IIIa inhibitors have not been effective in this situation. For other plaques not presently destabilized, the main goal of therapy is reducing future acute coronary events. Several classes of drugs, including ACE inhibitors, beta-blockers, and antithrombotic agents in addition to lipid-lowering agents, reduce events, and this may be attributable, at least in part, to plaque-stabilizing effects.

Oral anticoagulant therapy during and after coronary angioplasty the intensity and duration of anticoagulation are essential to reduce thrombotic complications

BACKGROUND

In the randomized Balloon Angioplasty and Anticoagulation Study (BAAS), the addition of oral anticoagulants to aspirin significantly reduced early and late events after coronary angioplasty. However, bleeding episodes were increased. The present report studied the intensity and the duration of anticoagulation as predictors of thrombotic and bleeding events.

METHODS AND RESULTS

A total of 530 patients, 34% of whom received a stent, were treated with aspirin plus coumarins. Half of the patients were randomized to angiographic follow-up. The target international normalized ratio (INR) was 2.1 to 4.8 during angioplasty and 6-month follow-up. Thrombotic events were death, myocardial infarction, target lesion revascularization, and thrombotic stroke. Bleeding complications were hemorrhagic stroke, major extracranial bleeding, and false aneurysm. "Optimal" anticoagulation was defined as an INR in the target range for at least 70% of the follow-up time. There were 17 early thrombotic events (3.2%), 7 early bleeding episodes (1.3%), and 10 false aneurysms (1.9%). The incidence rate for both early thrombotic and bleeding events was lowest in patients in the target range. A total of 61 late thrombotic events occurred (11.6%). Optimal anticoagulation was an independent predictor of late thrombotic events (relative risk, 0.33; 95% CI, 0.19 to 0.57) and was associated with a 0.21 mm (95% CI, 0.17 to 0.42) larger vessel lumen at 6 months. Late bleeding episodes (1.4%) were lowest in patients in the target range.

CONCLUSIONS

Coumarins started before coronary angioplasty with a target INR of 2.1 to 4.8 led to the lowest procedural event rate, without an increase in bleeding episodes. During follow-up, optimal anticoagulation was associated with a decrease in the incidence of late events by 67% and a significant improvement in 6-month angiographic outcome.

[Changes in the diameter of the coronary arteries in heart transplant recipients with angiographically normal vessels during five years]

INTRODUCTION

Diffuse or focal coronary artery narrowing is a frequent complication of cardiac transplantation. Coronary enlargement has also been described although it is less known. To study the changes of the coronary arteries in transplant recipients, we have performed a quantitative study throughout 5 years.

METHODS

Serial coronary angiography was performed annually in all survivors of heart transplant. Forty four patients with visually normal coronary arteries and at least 5 years of evolution were selected for this study. Quantitative measurements of the diameter of the coronary arteries were performed in each angiogram at different levels: proximal, medium and distal left anterior descending coronary artery; proximal and distal left circumflex; proximal, medium and distal right coronary artery. Changes in diameter were compared throughout the 5 years.

RESULTS

In the entire group of patients there was a small increase in the diameter of each segment. Taking each patient separately, an enlargement of the diameter of the proximal descending coronary artery was seen in 17 cases; medium descending coronary artery in 13; distal descending coronary artery in 8; proximal left circumflex in 11; distal left circumflex in 14; proximal right coronary artery in 18; medium right coronary artery in 18 and distal right coronary artery in 15. In total, 114 of 352 coronary segments (32%) underwent dilatation. Only 6 patients failed to have dilatation of any segment.

CONCLUSIONS

Enlargement of the coronary arterial diameter was seen in 32% of segments of the main coronary arteries in heart transplant recipients with angiographically normal coronary arteries during 5 years of evolution. This could be due to intimal thickening with overcompensation by an additional vessel enlargement with net lumen gain.

Anticoagulant therapy in unstable angina

The goal of anticoagulant therapy in unstable angina is to prevent progression of a subocclusive coronary thrombus to complete occlusion of the coronary artery, thereby preventing myocardial infarction and death. Although these have been many advances in therapy with anticoagulants, considerable morbidity and mortality remains. Also, although combination therapy with potent novel anticoagulants and antiplatelet agents may be an alternative strategy, this needs to be balanced against the risks of hemorrhagic complications. More precise and biologically relevant methods of monitoring anticoagulant effect, along with appropriately modified doses given in combination offers promise.

Coronary artery flow ten weeks after myocardial infarction or unstable angina: effects of combined warfarin and aspirin therapy

Forty-three patients presenting with unstable angina or myocardial infarction were randomised double blind to warfarin [target international normalised ratio (INR), 2.0 to 2.5] and aspirin (150 mg) daily or placebo plus aspirin (150 mg) daily. Coronary flow was assessed with the thrombolysis in myocardial infarction (TIMI) flow grade and corrected TIMI frame count (CTFC). Coronary artery flow was reduced (higher CTFC) at baseline in culprit arteries (mean +/-SD, 37.1+/-15.4 frames) compared to nonculprit arteries (22.5+/-6.7 frames, P<0.0001). In patients with a patent artery at follow-up, coronary flow was unchanged after ten weeks of warfarin and aspirin (-2.0+/-19.9 frames) or aspirin alone (3.8+/-10.4 frames, P = 0.20). Patients randomised to aspirin alone were more likely to progress to total occlusion [aspirin, 7 of 19 (37%) vs. warfarin and aspirin, 1 of 24 (4%); P = 0.01). Higher baseline culprit artery CTFC was also associated with an increased risk of late occlusion [+10 frames; odds ratio (OR), 1.65; 95% CI, 1.01 to 2.33]. Coronary flow remained impaired ten weeks after presentation with myocardial infarction or unstable angina. Combination warfarin and aspirin therapy did not improve flow in vessels that remained patent but did reduce the risk of progression to occlusion.

Low molecular weight heparin (dalteparin) as adjuvant treatment of thrombolysis in acute myocardial infarction--a pilot study: biochemical markers in acute coronary syndromes (BIOMACS II)

OBJECTIVES

This randomized, double blind, placebo-controlled pilot trial evaluated the effect of dalteparin as an adjuvant to thrombolysis in patients with acute myocardial infarction regarding early reperfusion, recurrent ischemia and patency at 24 h.

BACKGROUND

Low-molecular-weight heparin, given subcutaneously twice daily without monitoring, might be an attractive alternative to conventional intravenous heparin in the treatment of acute myocardial infarction.

METHODS

In 101 patients dalteparin/placebo 100 IU/kg was given just before streptokinase and a second injection 120 IU/kg after 12 h. Monitoring with continuous vector-ECG was done to obtain signs of early reperfusion and later ischemic episodes. Blood samples for myoglobin were obtained at start and after 90 min to evaluate signs of reperfusion. Coronary angiography was performed after 20-28 h to evaluate TIMI-flow in the infarct-related artery.

RESULTS

Dalteparin added to streptokinase tended to provide a higher rate of TIMI grade 3 flow in infarct-related artery compared to placebo, 68% versus 51% (p = 0.10). Dalteparin had no effects on noninvasive signs of early reperfusion. In patients with signs of early reperfusion, there seemed to be a higher rate of TIMI grade 3 flow, 74% versus 46% (myoglobin) (p = 0.04) and 73% versus 52% (vector-ECG) (p = 0.11). Ischemic episodes 6-24 h. after start of treatment were fewer in the dalteparin group, 16% versus 38% (p = 0.04).

CONCLUSIONS

When dalteparin was added as an adjuvant to streptokinase and aspirin, there were tendencies for less ECG monitoring evidence of recurrent ischemia and better patency at 24 h, warranting further study.

Long-term oral anticoagulant therapy in patients with unstable angina or suspected non-Q-wave myocardial infarction: organization to assess strategies for ischemic syndromes (OASIS) pilot study results

BACKGROUND

Patients with acute ischemic syndromes (AIS) suffer high rates of recurrent ischemic events despite aspirin treatment. Long-term therapy with oral anticoagulants in addition to aspirin may reduce this risk. We studied the effects of long-term warfarin at 2 intensities in patients with AIS without ST elevation in 2 consecutive randomized controlled studies.

METHODS AND RESULTS

In phase 1, after the cessation of 3 days of intravenous antithrombotic therapy, 309 patients were randomized to receive fixed low-dose (3 mg/d) warfarin for 6 months that produced a mean international normalized ratio (INR) of 1.5+/-0.6 or to standard therapy. Eighty-seven percent of patients received aspirin in both groups. The rates of cardiovascular (CV) death, new myocardial infarction (MI), and refractory angina at 6 months were 6.5% in the warfarin group and 3.9% in the standard therapy group (relative risk [RR], 1. 66; 95% CI, 0.62 to 4.44; P=0.31). The rates of death, new MI, and stroke were 6.5% in the warfarin group and 2.6% in the standard therapy group (RR, 2.48; 95% CI, 0.80 to 7.75; P=0.10). The overall rate of rehospitalization for unstable angina was 21% and did not differ significantly between the groups. Four patients in the warfarin group (2.6%) and none in the control group experienced a major bleed (RR, 2.48; 95% CI, 0.80 to 7.75), and there was a significant excess of minor bleeds in the warfarin group (14.2% versus 2.6%; RR, 5.46; 95% CI, 1.93 to 15.5; P=0.001). In phase 2, the protocol was modified, and 197 patients were randomized <48 hours from the onset of symptoms to receive warfarin at an adjusted dose that produced a mean INR of 2.3+/-0.6 or standard therapy for 3 months. Eighty-five percent received aspirin in both groups. The rates of CV death, new MI, and refractory angina at 3 months were 5. 1% in the warfarin group and 12.1% in the standard group (RR, 0.42; 95% CI, 0.15 to 1.15; P=0.08). The rates of all death, new MI, and stroke were 5.1% in the warfarin group and 13.1% in the standard therapy group (RR, 0.39; 95% CI, 0.14 to 1.05; P=0.05). Significantly fewer patients were rehospitalized for unstable angina in the warfarin group than in the control group (7.1% and 17.2%, respectively; RR, 0.42; 95% CI, 0.18 to 0.96; P=0.03). Two patients in the warfarin group and 1 in the control group experienced a major bleed, and there was a significant excess of minor bleeds in the warfarin group (28.6% versus 12.1%; RR, 2.36; 95% CI, 1.37 to 4.36; P=0.004).

CONCLUSIONS

Long-term treatment with moderate-intensity warfarin (INR, 2.0 to 2.5) plus aspirin but not low-intensity warfarin (INR, 1.5) plus aspirin appears to reduce the rate of recurrent ischemic events in patients with AIS without ST elevation.

Mechanisms of arterial thrombosis: foundation for therapy

Intravascular thrombus often occurs when the rupture or fissure of an atherosclerotic plaque exposes procoagulant elements lying below the plaque surface. This process of plaque rupture is the result both of passive mechanical forces and an active cell-mediated mechanism. Recently a number of investigators have developed imaging technologies based on magnetic resonance to characterize atherosclerotic lesions or the use of radioactively labeled platelets to dynamically visualize clot formation and lysis in vivo. These methods may permit early detection of developing thrombus, improve selection of treatment, and allow direct monitoring of the progression of antithrombotic therapy.