Long-term anticoagulation with recombinant hirudin in a patient on left ventricular assist device support

Heparin-induced thrombocytopenia in patients with ventricular assist devices: are new prevention strategies required?

Heparin-induced thrombocytopenia (HIT) is caused by platelet-activating antiplatelet factor 4/heparin antibodies. However, clinical HIT (thrombocytopenia or thrombosis, or both) develops in only a minority of patients who form antibodies. It is difficult to distinguish HIT from non-HIT thrombocytopenia in patients after ventricular assist device (VAD) implantation. Further, the risks of heparin-induced immunization and clinical HIT approach 65% and 10%, respectively, in this patient population, with a particularly high risk of cerebrovascular ischemia/infarction. Given the apparent high risk of HIT and its complications, and the diagnostic challenges, we suggest that the VAD patient population be evaluated using alternative, nonheparin agents for routine postimplantation anticoagulation.

Cerebrovascular accidents in patients with a ventricular assist device

OBJECTIVE

A cerebrovascular accident is a devastating adverse event in a patient with a ventricular assist device. The goal was to clarify the risk factors for cerebrovascular accident.

METHODS

Prospectively collected data, including medical history, ventricular assist device type, white blood cell count, thrombelastogram, and infection, were reviewed retrospectively in 124 patients.

RESULTS

Thirty-one patients (25%) had 48 cerebrovascular accidents. The mean ventricular assist device support period was 228 and 89 days in patients with and without cerebrovascular accidents, respectively (P < .0001). Sixty-six percent of cerebrovascular accidents occurred within 4 months after implantation. Actuarial freedom from cerebrovascular accident at 6 months was 75%, 64%, 63%, and 33% with the HeartMate device (Thoratec Corp, Pleasanton, Calif), Thoratec biventricular ventricular assist device (Thoratec Corp), Thoratec left ventricular assist device (Thoratec), and Novacor device (WorldHeart, Oakland, Calif), respectively. Twenty cerebrovascular accidents (42%) occurred in patients with infections. The mean white blood cell count at the cerebrovascular accident was greater than the normal range in patients with infection (12,900/mm3) and without infection (9500/mm3). The mean maximum amplitude of the thrombelastogram in the presence of infection (63.6 mm) was higher than that in the absence of infection (60.7 mm) (P = .0309).

CONCLUSIONS

The risk of cerebrovascular accident increases with a longer ventricular assist device support period. Infection may activate platelet function and predispose the patient to a cerebrovascular accident. An elevation of the white blood cell count may also exacerbate the risk of cerebrovascular accident even in patients without infection. Selection of device type, prevention of infection, and meticulous control of anticoagulation are key to preventing cerebrovascular accident.

Heparin-Induced Thrombocytopenia Complicating Support by the Berlin Heart

Since 1992, miniaturized pulsatile air-driven ventricular assist devices (VADs), "Berlin Heart," have been used at many institutions (36 cases in North America in 19 different institutions) for pediatric use. Heparin-induced thrombocytopenia (HIT II) is a significant complication rarely reported in the setting of adult VAD support; no similar report exists concerning pediatric VAD support. We report on a 13-month-old, 8.1 kg girl who required LVAD support for cardiogenic shock of unclear etiology. The patient had a history of multiple surgical repairs for correction of complex congenital heart disease consisting of a series of left heart obstructive lesions (Shone's complex). Despite aggressive ventilatory and inotropic support, the patient continued to deteriorate and subsequently required extracorporeal life support. After 7 days of conventional venoarterial extracorporeal membrane oxygenation, a 10 ml Berlin Heart VAD was implanted. After implantation, the patient developed persistent low-grade fever of unclear etiology, gradual thrombocytopenia, and deterioration of renal function. On postimplant day 10, the pump required replacement because of concerns about an inlet valve thrombus; the explanted device demonstrated a nearly occlusive clot not appreciable from external inspection. Simultaneously, HIT II was diagnosed as a result of hematology workup for persistent thrombocytopenia. We discuss the unique challenges posed by HIT II complicating pediatric VAD support and in relation to the heparin coating of the device.