Gaisbo« ck syndrome (polycythemia and hypertension) revisited: Results from the national inpatient sample database

Background: Polycythemia is characterized by increased blood viscosity and a chronic inflammatory state possibly giving rise to excessive thromboembolic events and hypertensive cardiovascular disease. We aimed to study the relationship between polycythemia and cardiac risk factors using a large national registry. Methods: Patients more than 18 years with a diagnosis of polycythemia were identified from the National Inpatient Sample 2009-2010 database using International Classification of Diseases; Ninth Edition (ICD-9) code 238.4. Demographics, cardiac risk factors, and cardiovascular events were identified. Results: Polycythemia was present in 0.1% (n¼37922) of hospital-discharged patients. Patients with polycythemia had a significantly increased prevalence of all cardiac risk factors and events, except for diabetes mellitus and chronic kidney disease. Hypertension was more prevalent in polycythemia compared to controls (61 vs. 46%; P<0.0001). After adjusting for age, sex, race, diabetes mellitus, hyperlipidemia, tobacco use, obesity, coronary artery disease, heart failure, and chronic kidney disease, polycythemia was still a determinant of hypertension [1.37 (1.28-1.45); P<0.001]. Conclusion: Polycythemia had high prevalence of all cardiac risk factors and was independently associated with increased prevalence of hypertension even after adjusting. Our findings from the National Inpatient Sample provide an epidemiological correlate of Gaisböck's original observation of the association of polycythemia and hypertension more than a century ago.