Acute thrombosis in both atria during left atrial appendage occlusion: Case report on heparin resistance

Heart rhythm disorders can sometimes turn a steady beat into a chaotic flutter, a condition known as atrial fibrillation. When the upper chambers of the heart quiver instead of squeezing, blood can pool and form clots, which may travel to the brain and cause a stroke. For many patients, the standard defense against this danger is daily medication to thin the blood. However, some individuals face a difficult choice: they are at high risk for both severe bleeding and future strokes, making long-term blood-thinning medication a precarious balance. For these people, doctors have developed a way to physically seal off a small, pouch-like structure in the heart called the left atrial appendage, which is the most common place where these dangerous clots form. This procedure, known as left atrial appendage occlusion, involves threading a tiny device through a vein to plug the pouch from the inside. While this offers a lifeline for those navigating high risks of both bleeding and clots, the procedure itself carries risks, including the rare but terrifying possibility that a clot could form on the device or inside the heart while the doctors are working.

A team of doctors at The People's Hospital of Leshan recently documented a striking instance of this rare complication in a seventy-year-old woman. The patient had a history of high blood pressure and had already suffered two strokes, placing her at very high risk for a third. Because she faced significant risks from both bleeding and clotting, and because a one-stop procedure to treat her heart rhythm and seal the pouch was not covered by the healthcare system, the medical team decided to proceed with the occlusion procedure to protect her brain. The plan was straightforward: enter the heart, seal the pouch, and leave. However, as the doctors guided a catheter through the heart and prepared to release the sealing device, they saw something alarming on their ultrasound monitor. Floating in the upper chambers of the heart were new clots, attached to the device and the walls of the heart, appearing almost instantly after the procedure began.

The medical team immediately realized that the standard medication used to prevent clotting during such operations, heparin, was not working for this patient. This condition, known as heparin resistance, means the body does not respond to the drug as expected, leaving the blood dangerously prone to clotting even while the medication is being administered. In this specific case, the doctors had given a significant amount of heparin, yet the blood's ability to clot remained unchecked. The ultrasound showed the clots forming in both the left and right sides of the heart, a sign that the patient's entire system was in a state of heightened clotting risk, likely worsened by the physical manipulation of the heart during the procedure.

Recognizing the danger, the doctors stopped the procedure and withdrew their instruments to prevent the clots from breaking loose and traveling to the brain. They measured the time it took for the patient's blood to clot, a test called the activated clotting time, which came back far too low despite the high dose of heparin. They tried adding more heparin and even attempted to use a different type of drug called tirofiban, but neither worked to dissolve the clots or improve the blood's response. The team then made a critical switch, replacing the ineffective drugs with a different class of medication called bivalirudin, which works by a different mechanism to stop clotting. This change proved successful. By the next day, follow-up imaging showed that the clot in the right side of the heart had disappeared, and the clot in the left side had broken up and moved safely into the left ventricular outflow tract, where it continued to dissolve.

Over the following week, the patient remained stable, and repeat scans confirmed that all the clots had completely vanished without causing any new blockages or strokes. The doctors then adjusted her long-term medication plan to include a different blood thinner and a platelet inhibitor to keep her safe after the device was fully settled. A month later, a final check showed the sealing device was firmly in place with no leaks and no new clots. This case highlights that while the procedure to seal the heart is a vital option for high-risk patients, the body's reaction to the drugs used during the operation can be unpredictable. The doctors' ability to quickly identify that the standard drug was failing and to switch to an alternative treatment prevented a potentially catastrophic outcome, demonstrating that careful monitoring and readiness to change course are essential when working inside the human heart.