Heparin Induced Thrombocytopenia Flashcards
What are the four valves of the heart?
- Pulmonary valve–>blood flows from right ventricle to the pulmonary artery
- Tricuspid valve–>blood flows from right atrium to right ventricle
- Mitral valve–>blood flowing from left atrium to left ventricle
- Aortic valve–>blood flowing from the left ventricle to the aorta
Which two valves are commonly associated with diseases?
Mitral and aortic
Two main types of valvular heart disease
- Stenosis–>calcification and narrowing of the valve(a disease of aging)
- Regurgitation–>Blood flow backwards through valve
Aortic stenosis is the most common valvular disease
Aortic stenosis
Decreases cardiac output causing chest pain, fatigue, shortness of breath, syncope
Mitral regurgitation
Most common mitral vlave disease
This is often due to heart failure(increase blood volume and pressure in the left ventricle pushes blood backwards from the left ventricle to the left atrium)
Types of valves (Aortic and Mitral)
* Mechanical valve
1. Lasts 20-30 years
2. Risk of thromboembolism is higher
3. Requires lifelong anticoagulation w/ warfarin( INR goal 2-3{aortic} and 2.5-3.5{mitral})
* Bioprosthetic valve
1. Lasts ~10years
2. Risk of thromboembolism is lower
3. Requires ~3months of anticoagulation or antiplatelet therapy
Which valve replace has more thrombogenicity associated with it?
Mitral valve(higher risk of clotting)
- Mitral valve has mainly passive blood flow(low blood pressure)
- Aortic valve has mainly high-pressure blood flow
Heparin induced thrombocytopenia(HIT)
Prothrombic disorder associated w/ unfractionated heparin(UFH) or low molecular weight heparin(LMWH)
URH:5% of patients
LMWH: 0.5-1% of patients
Types of HIT
- Isolated HIT(HIT)–>labs are postive, but patient doesn’t have clot
- HITT–> HIT complicated by thrombosis
Risk factors for HIT
- Source of heparin–>Bovine is higher risk than porcine
- Type of heparin product used–> UFH is higher risk than LMWH
- Patient population–>Surgical patients are at higher risk than medical and obsetric patients
- Duration of exposure–>Longer exposure=higher risk
- Poute of adminsitration–>IV is higher risk than SQ
4T’s Pretest Score
- </_ 3 points–> low probability
- 4-5 points–>intermediate probability
- 6-8points–> high probability
Diagnosis of HIT
- Platelet trend decreasing while patient recieving heparin or LMWH
- Determine pre-test probability score(4T/HEP)
- If score is NOT low, STOP heparin and consider alternative anticoagulants(non-heparin) and send testing
- Recommended tests
* PF4IgG ELISA Immunoassay–> not diagnostic,detetcts heparin dependent IgG antibody, potential false positives
* Serotonin Release Asssay(SRA)–>Validation test ,detects actual pathologic response
Treatments for HIT,HITT
- 1st–> discontinue heparin and and initiate non-heparin coagulation
- 2nd(conditional)–> Selection for non-heparin anticoagulants: argatroban,bivalirudin,fondaparinux, or a direct oral anticoagulant(DOAC)
- 3rd(conditional)–>DOAC selection: rivoraxaban has the most evidence but any can be used
==>Dosing(rivoraxaban)
HIT:15mg BID until platelet count recovery(>150K) then 20mg QD
HITT: 15mg BIDx 3wks, then 20mgQD
Alternative IV coagulants
Argatroban and Bivalirudin
Similatrities:
* Direct thrombin inhibitor
* Continuous IV infusion
* Monitor hemoglobin,hematocrit,platelets
* Will elevate INR
Differences:
* Half-life–>Argatroban(39-51mins);Bivalirudin(10-24mins)
* Renal adjustments–>Argatroban(Not dialyzable);Bivalirudin(Dialyzable)
* Pearls–>Agratroban(~85% hepatobiliary elimination);Bivalirudin(~85% proteolytic elimination)
What happens if we are transitioning from DTI to Warfarin?
Transition after platelets >/-150,000; when using both adminster 5 doses of warfarin and recheck INR every 4hrs. If INR is > 4 stop argatroban, if INR is >3 stop bivalirudin
NB: if PTT baseline and INR are in range , leave drip off
if PTT baseline and INR below range restart drip
