A 10 Year Retrospective Analysis of Carotid Stenosis in Patients with Polycythemia Vera or Essential Thrombocythemia

Patients with polycythemia vera (PV) or essential thrombocythemia (ET) are at an increased risk for thrombotic events. The pathophysiology of hyperviscosity, leukocyte-induced endothelial damage, and the over-expression of JAK2 and STAT5 genes contributing to the development of atherothrombosis is poorly understood. As such, the goal of our study was to retrospectively examine carotid stenosis severity in patients with PV or ET and to determine if carotid stenosis is associated with thrombotic events in this patient group.

We examined patients in a ten year period (2004 to 2014) who were under the care of a hematologist at our tertiary care-teaching hospital for either PV or ET, and, having one or more carotid duplex. Patients having diagnoses of secondary polycythemia or secondary thrombocytosis were excluded. Data obtained from patient charts included demographics, cardiovascular risk factors, thrombotic events, platelet and hematocrit levels, medications, and carotid stenosis severity. Clinically significant carotid stenosis was defined as >50 % stenosis. We compared patients with carotid stenosis to those without stenosis using Fisher exact tests.

Of the 31 patients meeting study inclusion, only 9 (29%) presented with clinically significant carotid stenosis with 1 (3%) patient having increasing carotid stenosis severity during the study period. Elevated cell counts did not correlate with carotid stenosis. Elevated hematocrit levels of >45% or elevated platelet counts >400x 10⁹/L, had no stasticial difference in the incidence of carotid stenosis versus no stenosis (50% vs. 18%, P = 0.16) and (63% vs. 64%, P = 1.00) respectively. There was no difference between the two groups with the use of either anti-platelet therapy (P = 0.68) or cytoreduction medications (P = 1.00) at the time of duplex.

A total of 21 patients had 1 or more thrombotic event during the 10 year period. A total 35 thrombotic events occurred, with the distribution of events being 29% deep venous thrombosis, 28% stroke, 23% transient ischemia attack (TIA), 11% myocardial infarction, 3% peripheral arterial thrombosis, 3% pulmonary embolism and 3% retinal artery or vein occlusion. Rates of thrombotic events were comparable between ET and PV patients, with 10 of 15 patients with PV, 10 of 15 patients with ET and 1 patient with ET + PV experiencing a thrombotic event (P = 0.75). Carotid stenosis did not associate with increased rates of stroke or other thrombotic events. Stroke/TIA after duplex occurred in 22% of patients with carotid stenosis versus 9% of patients with no carotid stenosis (P = 0.56). Likewise, the rate of all thrombotic events after duplex was similar in patients with and without carotid stenosis (33% and 41%, respectively, P = 1.00).

Two patients received carotid revascularization during the study period. Carotid endarterectomy appeared to be successful in one asymptomatic patient who presented with severe bilateral internal carotid artery stenosis. The other patient who received angioplasty for fibromuscular dysplasia and found to have carotid stenosis of <30% stenosis, later required neurological consults months post procedure due to TIA like symptoms. Thus, in this patient’s case, the underlying cause of the recurring symptoms may have been related to ET.

This preliminarily study suggests that carotid stenosis may not predict thrombotic events in patients with ET or PV. Furthermore, patients with suspected carotid stenosis and/or presenting with stroke and having sustained elevated platelet/hematocrit levels may need to be evaluated for an underlying hematological disorder.