From the Guidelines
Heparin infusion is recommended for patients with mechanical heart valves who require anticoagulation but need to temporarily discontinue warfarin, with a standard protocol involving a bolus dose and continuous infusion to maintain a therapeutic range of an activated partial thromboplastin time (aPTT) of 1.5-2.5 times the control value or an anti-Xa level of 0.3-0.7 units/mL, as supported by the 2017 AHA/ACC guideline update 1.
The decision to use heparin bridging therapy should be individualized, taking into account the trade-offs between thrombosis and bleeding, particularly in patients with mechanical heart valves who are at higher risk of thromboembolic events 1. Key considerations include the type of mechanical valve, presence of additional risk factors such as atrial fibrillation, previous thromboembolism, or hypercoagulable conditions, and the patient's overall clinical context.
Some important points to consider when initiating heparin therapy for patients with mechanical heart valves include:
- Starting with a bolus dose of 80 units/kg followed by a continuous infusion at 18 units/kg/hour
- Monitoring aPTT 6 hours after initiation and adjusting the infusion rate accordingly to maintain the target therapeutic range
- Overlapping heparin with warfarin for at least 48 hours and until the INR reaches the therapeutic range when transitioning back to warfarin therapy
- Maintaining strict anticoagulation to minimize the risk of thromboembolism, which is critical for patients with mechanical heart valves 1.
It is also crucial to monitor patients for signs of bleeding or thrombosis throughout the heparin therapy period and to adjust the treatment plan as needed to balance the risks and benefits of anticoagulation therapy 1.
From the Research
Heparin Drip for Mechanical Heart Valve Patients
- The appropriate heparin drip for a patient with a mechanical heart valve can be initiated with an intravenous bolus of 80 U/kg bodyweight, and an infusion of 18 U/kg/h, with the activated thromboplastin time targeted at 60-80 s 2.
- An alternative to intravenous heparin is subcutaneous low-molecular weight heparin (LMWH), which is prescribed in a mg/kg dose 2.
- Studies have shown that LMWH can be used as a bridging anticoagulation therapy in patients with mechanical heart valves on long-term oral anticoagulants, with similar major adverse event rates and major bleeds compared to unfractionated heparin (UFH) 3, 4, 5.
- The choice of heparin drip may depend on the individual patient's characteristics, such as the type and position of the mechanical heart valve, as well as the presence of other risk factors for stroke or bleeding 2, 6.
Key Considerations
- The American College of Chest Physicians recommends anticoagulation with Warfarin at an INR range of 2-3 for patients with a bileaflet mechanical valve in the aortic position, and an INR of 2.5-3.5 for patients with a mechanical valve in the mitral position 2.
- Patients with mechanical heart valves require life-long anticoagulation, and the use of heparin drip should be carefully managed to minimize the risk of thromboembolic events and bleeding complications 3, 6, 4, 5.
- The efficacy and safety of LMWH compared to UFH have been demonstrated in several studies, with LMWH showing improved efficiency and safety, as well as reduced duration of hospitalization and improved patient quality of life 4, 5.