Cardiovascular Accidents and Increased Hemoglobin: Secondary Erythrocytosis Compared to Primary Polycythemia Vera
Authors: Galeas Jose Nahun , Tegla Cosmin , Sukrithan Vineeth , Verma Amit , Goel Swati 
Published: November 2019

Abstract
Background
Risk of cardiovascular accident (CVA) is much higher in patients with Polycythemia Vera (PV) compared to age matched general population. It is a widely established fact that CVA is a major cause of morbidity and mortality in patients with PV. At the same time, scientific literature is lacking in data about patients with secondary erythrocytosis and CVA. This is a novel study in an effort to elucidate patient characteristics in CVA patients with secondary erythrocytosis compared to PV.
Patients and Methods
Patients >=18 years of age seen at a Montefiore outpatient clinic and/or inpatient setting from 1998 to 2014 with a diagnosis of CVA and polycythemia, either primary or secondary, were included in this study. This was done with the help of Clinical Looking Glass software after obtaining Institutional Review Board approval. The diagnoses of Primary polycythemia and secondary erythrocytosis were confirmed by evaluating each medical record in detail. After confirming diagnosis, further evaluation and data collection including different lab values like WBC, Hg, platelets, MCV, RDW and albumin was done by in depth analysis of electronic medical records. Baseline characteristics were compared using two sample tests of proportions and Student t-Tests.
Results
Total of 53 patients with CVA and polycythemia were identified. Out of these 53 patients, 28 (53%) patients had PV and 25 (47%) patients had secondary erythrocytosis. Average age of patients with PV and CVA was 65 years whereas the average age for secondary erythrocytosis and CVA was 60 years. Younger average age of patients with CVA and secondary erythrocytosis can be attributed to the patients with Congenital Heart disease in this cohort which constituted about 16% of this population. Other causes of secondary erythrocytosis were COPD, Obstructive Sleep apnea, heart failure and use of Erythropoietin Stimulating agents in end stage renal disease patients. Male to female ratio was same in both groups with a value of 1.3. About half of the patients in the PV group were white whereas about half of the patients in the secondary erythrocytosis group were of Hispanic origin. As expected, WBC and platelet counts were significantly higher in PV versus secondary erythrocytosis group. The average highest hemoglobin values were significantly lower in PV patients (17.7 g/dl) compared to the patients with secondary erythrocytosis (19.4 g/dl). Low albumin values were similar in both groups. Interestingly, Red blood cell Distribution Width (RDW) values were significantly higher in PV patients compared to secondary erythrocytosis group. Table 1 depicts the demographic and laboratory characteristics of both groups of patients.
Conclusions
This study demonstrates that patients with secondary erythrocytosis are also at risk for CVA even at a younger age. Our study confirms that PV patients have much higher WBC and platelet values which are most likely contributory to the thrombogenic process in these patients besides the high hemoglobin/hematocrit. Also, high RDW is a significant predictor of disease activity in PV. We still don't know whether phlebotomizing the patients with secondary erythrocytosis will decrease their CVA risk without compromising the oxygenation of end organs. Prospective randomized trials are needed to clarify the optimal recommendations for stroke prevention in patients with secondary erythrocytosis.
Table 1. Characteristics of patients with CVA and Primary Polycythemia versus Secondary Erythrocytosis Polycythemia Vera Secondary Erythrocytosis Total ( n) 28 25 Average Age ( range) 65(20-104) 60( 25-84) M:F ratio 1.3 1.3 Race/Ethnicity Black 25% 24% Hispanic 25% 52% White 50% 24% p-value Highest WBC (k/uL) 30.2 18.9 0.02 Highest Hb (g/dL) 17.7 19.4 <0.001 Highest Platelets (k/uL) 660.7 294.6 <0.001 Lowest Albumin (g/dL) 2.9 2.8 0.87 Average RDW 24.4 19.5 0.001

Disclosures
No relevant conflicts of interest to declare.