Hemostasis, Thrombosis, Antithrombotic Therapy, and Thrombolysis in Vascular Practice

5.1Hemostasis and thrombosis mechanisms in vascular patients

Hemostasis and thrombosis in vascular practice are best understood as competing bedside risks rather than as isolated laboratory pathways. The same patient may need prevention of myocardial infarction, stroke, and major adverse limb events after lower-extremity revascularization, treatment-phase anticoagulation for venous thromboembolism, or urgent thrombus removal for limb-threatening venous disease or pulmonary embolism with hemodynamic compromise. The surgeon’s task is to identify the thrombotic syndrome, match the intensity of therapy to that syndrome, and reassess bleeding risk whenever therapy is escalated, interrupted, or combined. ESVS 2023 · ASH 2020 · VOYAGER 2020 · COMPASS 2017

The practical distinction is not “arterial versus venous” as an academic label, but whether the patient’s current problem is best treated with single antiplatelet therapy, dual antiplatelet therapy, dual-pathway inhibition, full-intensity anticoagulation, or thrombolysis. Symptomatic PAD has a prevention problem; acute DVT and PE have a treatment-phase anticoagulation problem; hemodynamically compromising PE and selected severe DVT have a rescue or thrombus-removal problem; and peri-procedural care has an interruption-and-resumption problem. Each category carries different evidence, different bleeding exposure, and different follow-up implications. ASH 2020 · ESC 2019 · ESC 2017 · VOYAGER 2020 · COMPASS 2017

In symptomatic PAD, the default vascular prevention question begins with antiplatelet therapy rather than full-intensity anticoagulation. After endovascular revascularization for PAD, dual antiplatelet therapy with a P2Y12 antagonist plus low-dose aspirin is reasonable for at least 1 to 6 months, giving the vascular surgeon a practical duration band when the operative chapter does not specify a narrower device- or lesion-specific plan. This interval should not be converted into a reflexive rule for every patient; the correct duration remains conditioned by bleeding risk, tolerance, revascularization context, and the subsequent need for other antithrombotic indications. VOYAGER 2020 · COMPASS 2017

Bleeding risk assessment begins before the incision and before the prescription. A structured bleeding history is particularly important when an inherited bleeding disorder is possible; the ISTH/SSC bleeding assessment tool provides a standardized approach and is intended to supplement, not replace, laboratory hemostasis testing. ISTH SSC bleeding 2010 In vascular patients, this distinction matters because a normal casual history can miss a lifelong bleeding phenotype, while an acquired bleeding diathesis requires additional evaluation beyond an inherited-disorder screening tool.

The language used to define bleeding also matters. Antithrombotic studies may report major bleeding by a formal endpoint definition, and the ISTH definition of major bleeding in non-surgical patients receiving antihemostatic medicinal products remains a canonical reference for interpreting those endpoints. Definition major bleeding 2005 A vascular surgeon reading a trial must therefore ask which bleeding definition was used before comparing one regimen with another, especially when a limb or cardiovascular benefit is presented beside bleeding outcomes.

Venous thrombosis requires a different mental model. Acute DVT management is framed by contemporary DVT consensus and VTE guidelines, with anticoagulation forming the foundation and thrombus removal reserved for selected circumstances. ESC 2017 The CaVenT trial provides landmark randomized comparator evidence for additional catheter-directed thrombolysis in acute iliofemoral DVT, while ATTRACT provides a later pharmacomechanical thrombolysis comparator in acute proximal DVT; neither trial should be used alone to justify routine lysis outside current guideline-based selection. ATTRACT 2017 · Long-term outcome after 2012

The safest habit for a senior trainee is to name the indication before naming the drug. “Rivaroxaban,” “aspirin,” “clopidogrel,” or “thrombolysis” are incomplete orders unless the indication, intended intensity, expected duration, and bleeding tradeoff are explicit. Low-dose rivaroxaban plus aspirin for PAD prevention is not the same as full-intensity anticoagulation for VTE, and thrombolysis for hemodynamically compromising PE is not the same decision as thrombolysis for symptomatic proximal DVT. ASH 2020 · VOYAGER 2020 · COMPASS 2017

5.2Antiplatelet and anticoagulant selection principles

Antithrombotic selection should start with the clinical syndrome and only then move to drug choice. In symptomatic PAD, single antiplatelet therapy is recommended to reduce major adverse cardiovascular events; the guideline-specified monotherapy choices include clopidogrel 75 mg daily or aspirin 75–325 mg daily. This is the starting point before considering post-intervention dual antiplatelet therapy, dual-pathway inhibition, or anticoagulation for a separate condition. ACC/AHA 2024 · VOYAGER 2020 · COMPASS 2017

Clopidogrel monotherapy has a dedicated atherosclerotic vascular disease evidence reference point. In CAPRIE, clopidogrel 75 mg once daily was compared with aspirin 325 mg once daily in 19,185 patients with atherosclerotic vascular disease, with annual ischemic stroke, myocardial infarction, or vascular death rates of 5.32% with clopidogrel versus 5.83% with aspirin, an 8.7% relative-risk reduction favoring clopidogrel. CAPRIE · 1996 The aspirin dose in CAPRIE was 325 mg, so the trial should be used as a clopidogrel-monotherapy comparator rather than as a simple statement about all contemporary aspirin dosing.

Ticagrelor should not be presumed superior to clopidogrel for symptomatic PAD monotherapy. In the symptomatic PAD population randomized in EUCLID, ticagrelor 90 mg twice daily was not superior to clopidogrel 75 mg daily for cardiovascular death, myocardial infarction, or ischemic stroke, with event rates of 10.8% versus 10.6% and similar major bleeding at 1.6% in each group. Ticagrelor versus Clopidogrel 2017 This is a useful negative trial when a trainee is tempted to escalate antiplatelet potency without a disease-specific reason.

Dual antiplatelet therapy is a time- and indication-sensitive choice, not a synonym for “more vascular protection.” After endovascular revascularization for PAD, a P2Y12 antagonist plus low-dose aspirin is reasonable for at least 1 to 6 months; outside such contexts, historical dual-antiplatelet comparisons such as CHARISMA should not be used to override contemporary PAD and revascularization guidance. Clopidogrel Aspirin 2006 The immediate bedside decision is whether the patient is in a post-procedural window where DAPT is intended to protect the treated segment, or in a chronic prevention phase where another strategy may be more appropriate. VOYAGER 2020 · COMPASS 2017

Dual-pathway inhibition is a separate construct from DAPT and from full-intensity anticoagulation. In symptomatic PAD, and after endovascular or surgical revascularization when bleeding risk is acceptable, low-dose rivaroxaban 2.5 mg twice daily combined with low-dose aspirin is effective and recommended to reduce major adverse cardiovascular events and major adverse limb events. The dose and intent are central: this is not full-intensity anticoagulation and should not be used as though it were treatment-dose therapy for atrial fibrillation or VTE. VOYAGER 2020 · COMPASS 2017

The post-revascularization evidence for this approach is clinically important because it gives the surgeon a results-based discussion with the patient. VOYAGER PAD randomized 6564 patients after lower-extremity revascularization and showed that rivaroxaban 2.5 mg twice daily plus aspirin reduced the 3-year primary limb/cardiovascular composite from 19.9% to 17.3%, with a hazard ratio of 0.85. VOYAGER 2020 Bleeding must be discussed in the same conversation: TIMI major bleeding was 2.65% versus 1.87%, while ISTH major bleeding was 5.94% versus 4.06%.

For acute VTE, anticoagulant selection is grounded in treatment-phase evidence and current guideline framing rather than in arterial prevention logic. The landmark DOAC-versus-conventional therapy trials provide the evidence family: apixaban in AMPLIFY, rivaroxaban in EINSTEIN-PE, edoxaban in Hokusai-VTE, and dabigatran in RE-COVER. AMPLIFY · 2013 · HOKUSAI 2013 · EINSTEIN 2012 · Dabigatran versus Warfarin 2009 These trials support DOAC-based VTE treatment comparators, while final drug selection still depends on the disease-specific context, including renal function, pregnancy, cancer, antiphospholipid syndrome, drug interactions, and bleeding risk.

AMPLIFY is a useful dosing and outcome reference point when discussing apixaban as a VTE treatment option. AMPLIFY · 2013 The regimen used apixaban 10 mg twice daily for early follow-up window followed by 5 mg twice daily for 6 months; recurrent symptomatic VTE or VTE-related death occurred in 2.3% with apixaban versus 2.7% with conventional therapy, meeting noninferiority, and major bleeding was lower with apixaban at 0.6% versus 1.8%. This supports the principle that VTE treatment requires treatment-dose anticoagulation with a defined phase, not PAD-dose dual-pathway inhibition.

The phase of VTE care should be stated explicitly in the operative note, discharge plan, and follow-up letter. ASH frames initial VTE management as the first 5 to 21 days after diagnosis, with primary treatment continuing anticoagulation for 3 to 6 months as the minimum treatment phase; after that, the clinical decision becomes whether to stop anticoagulation or continue secondary prevention, often indefinitely with regular reassessment. ASH 2020 This prevents the common error of treating “three months” as a universal endpoint rather than as the minimum phase after which recurrence and bleeding risks must be revisited.

5.3Thrombolysis and bleeding-risk tradeoffs

Thrombolysis is a high-consequence treatment decision and should be reserved for clinical situations where the expected thrombotic harm is immediate or substantial enough to justify bleeding exposure. In PE, ASH strongly recommends thrombolytic therapy when pulmonary embolism is accompanied by hemodynamic compromise, and the ESC acute PE guideline provides a European framework for diagnosis and management. ASH 2020 · ESC 2019 The key decision point is therefore not simply clot burden, but the presence of hemodynamic compromise and the patient’s capacity to tolerate bleeding risk.

For DVT, thrombolysis should be treated as a narrow branch rather than as routine proximal-DVT care. ASH remarks that thrombolysis is reasonable to consider for limb-threatening DVT, such as phlegmasia cerulea dolens, and for selected younger patients at low bleeding risk with symptomatic DVT involving the iliac and common femoral veins; use should be rare for DVT limited below the common femoral vein. ASH 2020 This is one of the most important selection rules for vascular trainees, because venous intervention enthusiasm can otherwise outpace the evidence.

ATTRACT is the practical trial that prevents overclaiming for pharmacomechanical thrombolysis in acute proximal DVT. ATTRACT 2017 In 692 randomized patients, pharmacomechanical thrombolysis did not reduce overall post-thrombotic syndrome from 6 to 24 months, with rates of 47% versus 48%, and it increased major bleeding within 10 days, 1.7% versus 0.3%. The trial did show less moderate-to-severe post-thrombotic syndrome, 18% versus 24%, which preserves nuance for selected patients while arguing strongly against routine use.

CaVenT remains a landmark comparator for additional catheter-directed thrombolysis in acute iliofemoral DVT and should be cited alongside ATTRACT when discussing the evidence base for venous thrombus removal. ATTRACT 2017 · Long-term outcome after 2012 Its role in this chapter is not to create an automatic iliofemoral-DVT lysis pathway, but to remind the surgeon that iliofemoral disease is the venous territory in which thrombus-removal questions have been most seriously studied.

Bleeding-risk tradeoffs must be named with the same precision as thrombotic endpoints. The ISTH major bleeding definition is central to interpreting non-surgical antithrombotic trial endpoints, while structured bleeding-history assessment with the ISTH/SSC bleeding assessment tool can identify patients in whom escalation should be reconsidered or further hemostasis evaluation is required. ISTH SSC bleeding 2010 · Definition major bleeding 2005 A patient with limb-threatening DVT or hemodynamically compromising PE may still need escalation, but the bleeding history changes consent, monitoring, and the threshold for specialist input. ASH 2020

The same tradeoff applies to non-lytic intensification. In VOYAGER PAD, the reduction in post-revascularization limb and cardiovascular events with rivaroxaban 2.5 mg twice daily plus aspirin was accompanied by more ISTH major bleeding, and in COMPASS, rivaroxaban 2.5 mg twice daily plus aspirin reduced cardiovascular death, stroke, or myocardial infarction compared with aspirin alone but increased major bleeding. VOYAGER 2020 · COMPASS 2017 These data should be presented as paired outcomes, because benefit-only explanations distort vascular decision-making.

Thrombolysis should also be contrasted with chronic prevention. A patient with symptomatic PAD generally begins with single antiplatelet therapy, dual-pathway inhibition in selected contexts, or short-course post-endovascular DAPT rather than thrombolysis. CAPRIE supports clopidogrel monotherapy as a vascular prevention comparator, and ACC/AHA PAD guidance defines when antiplatelet and low-dose rivaroxaban-plus-aspirin strategies are appropriate in PAD. VOYAGER 2020 · COMPASS 2017 · CAPRIE · 1996

A clear thrombolysis note should document the indication, the anatomic or hemodynamic reason for escalation, the bleeding assessment, the alternative of anticoagulation alone when relevant, and the expected follow-up implication. For DVT, that means distinguishing limb-threatening disease or selected iliac/common femoral disease from routine proximal DVT; for PE, it means identifying hemodynamic compromise; for PAD prevention, it means not confusing intensified prevention with thrombus lysis. ASH 2020 · ESC 2019 · ATTRACT 2017

5.4Peri-procedural interruption, reversal, and complications

Peri-procedural antithrombotic management in vascular surgery is a structured risk decision, not an administrative medication hold. The surgeon must identify the indication for the antithrombotic drug, the consequence of procedural bleeding, the consequence of thrombosis during interruption, and the plan for resumption after hemostasis is secure. PAUSE provides the contemporary peri-procedural management reference for patients with atrial fibrillation receiving apixaban, dabigatran, or rivaroxaban who undergo elective procedures or surgery. Perioperative Management Patients 2019

The first practical distinction is whether the patient is receiving a DOAC or warfarin and whether the evidence being invoked actually applies to that patient. PAUSE addresses peri-procedural DOAC management in atrial fibrillation, while BRIDGE addresses perioperative bridging versus no bridging in warfarin-treated atrial fibrillation patients undergoing elective procedures or surgery. Perioperative Bridging Anticoagulation 2015 · Perioperative Management Patients 2019 Neither should be generalized to every vascular patient without attention to the underlying indication and procedure-specific bleeding consequences.

Bridging should not be treated as a ritual response to interruption. BRIDGE is a landmark comparator for warfarin-treated atrial fibrillation, but it does not answer perioperative management for DOAC-treated patients, nor does it substitute for disease-specific decisions in patients anticoagulated for VTE, valve disease, or another high-risk indication. Perioperative Bridging Anticoagulation 2015 The vascular surgeon should therefore write “bridging indicated” only after the indication-specific thrombotic risk has been identified, not because an anticoagulant was stopped. Perioperative Management Patients 2019

Reversal and emergency management require the same discipline. When bleeding or urgent surgery disrupts the planned antithrombotic course, the immediate question is the clinical severity of bleeding and the need to restore procedural hemostasis, while the later question is when and how to return to the indication-specific regimen. The ISTH major bleeding definition helps interpret non-surgical antithrombotic bleeding endpoints, but operative bleeding decisions require clinical judgment and should not be reduced to trial terminology alone. Perioperative Management Patients 2019 · Definition major bleeding 2005

Complications after interruption usually arise from one of three failures: stopping a necessary drug without a resumption plan, adding bridging or combination therapy without a valid indication, or resuming therapy without reassessing bleeding. In PAD, full-intensity oral anticoagulation should not be used to reduce major adverse cardiovascular events or major adverse limb events in the absence of another indication, such as atrial fibrillation or VTE; this principle is especially important after a peri-procedural complication, when clinicians may be tempted to “do more” without a supported indication. VOYAGER 2020 · COMPASS 2017

Follow-up after a peri-procedural antithrombotic complication should return the patient to the original indication and current clinical state. A patient interrupted during VTE primary treatment remains within the VTE treatment framework; a patient after lower-extremity revascularization remains within PAD post-revascularization prevention; and a patient on anticoagulation for atrial fibrillation remains within that indication’s perioperative evidence base. The practical discharge question is whether the patient is back on the intended regimen, has a documented reason for delay or de-escalation, and has a reassessment point. ASH 2020 · VOYAGER 2020 · COMPASS 2017 · Perioperative Management Patients 2019

5.5Disease-specific handoffs and what not to overclaim

This chapter provides general antithrombotic principles; disease-specific chapters must determine the final procedural algorithm, anatomy-specific intervention, and longitudinal surveillance schedule. The most important global rule is to avoid using antithrombotic intensity as a substitute for indication. In PAD without another indication such as atrial fibrillation, VTE, or valve disease, full-intensity oral anticoagulation should not be used to reduce major adverse cardiovascular events or major adverse limb events. VOYAGER 2020 · COMPASS 2017

For stable atherosclerotic vascular disease, COMPASS supports selected use of dual-pathway inhibition rather than indiscriminate anticoagulation. COMPASS 2017 Rivaroxaban 2.5 mg twice daily plus aspirin 100 mg daily reduced cardiovascular death, stroke, or myocardial infarction compared with aspirin alone, 4.1% versus 5.4%, with a hazard ratio of 0.76, but increased major bleeding, 3.1% versus 1.9%, with a hazard ratio of 1.70; intracranial or fatal bleeding was not significantly increased. This result should be communicated as a tradeoff, not as a bleeding-free improvement.

The COMPASS PAD cohort gives more PAD-specific nuance. COMPASS PAD subgroup. 2018 Among 7470 patients with stable lower-extremity or carotid PAD, or CAD with low ABI, rivaroxaban 2.5 mg twice daily plus aspirin reduced cardiovascular death, myocardial infarction, or stroke compared with aspirin alone, 5% versus 7%, and reduced major adverse limb events including major amputation, 1% versus 2%. Major bleeding increased, 3% versus 2%, mainly gastrointestinal, while fatal or critical-organ bleeding was not increased in the abstract interpretation.

After lower-extremity revascularization, VOYAGER PAD provides the key post-procedural dual-pathway evidence, while ACC/AHA PAD guidance supplies the recommendation framework. VOYAGER 2020 Rivaroxaban 2.5 mg twice daily plus aspirin reduced the 3-year limb/cardiovascular composite from 19.9% to 17.3%, and the guideline recommends low-dose rivaroxaban plus low-dose aspirin after endovascular or surgical revascularization when bleeding risk is acceptable. After endovascular revascularization, DAPT with a P2Y12 antagonist plus low-dose aspirin remains reasonable for at least 1 to 6 months, so the handoff must clarify whether the patient is receiving short-course DAPT, dual-pathway inhibition, or another regimen for another indication. COMPASS 2017

For VTE, the handoff should state the phase of treatment. ASH defines initial management as the first 5 to 21 days after diagnosis and primary treatment as anticoagulation for 3 to 6 months total as the minimum treatment phase; after primary treatment, the decision becomes stopping anticoagulation versus continuing secondary prevention, typically indefinitely with regular reassessment. ASH 2020 CHEST 2021, ASH 2020, and ESC frameworks should be used for current VTE framing, while CHEST 2016 is mainly historical or comparative when explicitly needed. Antithrombotic Therapy VTE 2021 · ESC 2017 · Antithrombotic Therapy VTE 2016

DOAC trial results should be used as evidence anchors, not as substitutes for individualized treatment selection. AMPLIFY supports apixaban treatment with 10 mg twice daily for early follow-up window followed by 5 mg twice daily for 6 months; EINSTEIN-PE supports rivaroxaban as an oral comparator for symptomatic PE; Hokusai-VTE supports edoxaban for symptomatic VTE; and RE-COVER supports dabigatran after initial parenteral anticoagulation. AMPLIFY · 2013 · HOKUSAI 2013 · EINSTEIN 2012 · Dabigatran versus Warfarin 2009 The disease-specific VTE chapter must still handle special populations, contraindications, and duration beyond the primary treatment phase.

Thrombolysis handoffs require especially careful wording. It is appropriate to say that ASH strongly recommends thrombolysis for PE with hemodynamic compromise, and that thrombolysis may be considered for limb-threatening DVT or selected younger low-bleeding-risk patients with symptomatic iliac and common femoral DVT. ASH 2020 It is not appropriate to say that proximal DVT generally requires pharmacomechanical thrombolysis, because ATTRACT did not reduce overall post-thrombotic syndrome and increased early major bleeding. ESC 2019 · ATTRACT 2017

Antiplatelet handoffs should also avoid overclaiming. CAPRIE supports clopidogrel as a monotherapy comparator in atherosclerotic vascular disease; EUCLID does not support ticagrelor superiority over clopidogrel for symptomatic PAD monotherapy; and CHARISMA provides historical dual-antiplatelet comparator evidence but does not determine contemporary post-revascularization or dual-pathway decisions by itself. Ticagrelor versus Clopidogrel 2017 · Clopidogrel Aspirin 2006 · CAPRIE · 1996 This prevents a common error in vascular practice: using a familiar trial name to justify a regimen in a setting the trial does not settle.

European and North American frameworks should be treated as complementary rather than interchangeable. The ESVS antithrombotic guideline provides a vascular-surgery framework across arterial and venous vascular diseases, ACC/AHA PAD guidance defines key PAD recommendations, CHEST and ASH frame VTE treatment decisions, and ESC documents provide European DVT and PE context. ESVS 2023 · ASH 2020 The senior surgeon’s responsibility is to match the patient’s syndrome to the correct framework and to document why an antithrombotic regimen was chosen, continued, escalated, or stopped. Antithrombotic Therapy VTE 2021 · ESC 2019 · ESC 2017 · VOYAGER 2020 · COMPASS 2017