Clot-Buster Keeps Heart Devices Humming

"This is such a simple solution to a very serious problem for heart failure patients who receive left ventricular assist devices (LVADs)," says lead author Markus Rothenburger, M.D., a resident in cardiovascular surgery at University Hospital in Muenster, Germany.

An LVAD is a mechanical pump-type device surgically implanted to maintain the pumping ability of a heart that can't effectively work on its own. Clot-busting drugs, also known as thrombolytic therapy, dissolve blood clots that impair blood flow. Most LVADs are based on a pulsatile blood flow. It has been reported that up to 47 percent of all patients with a pulsatile LVAD develop clotting complications, according to the report.

The recently introduced MicroMed DeBakey VAD, the device used in this study, differs from other LVADs in that it generates a continuous blood flow rather than a pulsing one. Their advantage over similar devices is smaller size, which seems to have reduced the incidence of thromboembolism and infections. It is also quieter.

Thromboembolism is a blood clot that moves through the blood stream before blocking an artery. "Despite these advances, its axial pump seems to be associated with a higher risk for clot formation, which then might cause device malfunction and peripheral thromboembolism," Rothenburger says.

"Our study shows that this serious complication can be treated effectively with intravenous administration of rt-PA. Exchange of the device, in most cases, is not necessary," he says.

The researchers followed 22 patients, 20 men and two women, with the MicroMed DeBakey VAD, finding that the pump flow was critically reduced in eight patients. In seven cases, the pump worked harder, which indicates clot formation inside the device. In one case, the demand on the pump was very low, indicating that a clot was in the opening of the device.

No emergency surgical device exchange was necessary after receiving rt-PA. No severe bleeding complications occurred, which can be a side effect of thrombolytic therapy. Four patients did have nose bleeds for three days. All patients were discharged from intensive care immediately after discontinuing rt-PA. Six patients went on to successful heart transplantation and two died on LVAD support because of multiorgan failure.

"Thrombolytic therapy with rt-PA is an effective and easily applicable treatment for clot formation inside the MicroMed DeBakey VAD," says Rothenburger.

Other co-authors are D. Hammel, M.D.; C. Schmidt, M.D.; T.D.T. Tjan, M.D.; D. Bocker, M.D.; H.H. Scheld, M.D.; and C. Schmid, M.D.