The Relationship of Plasma Ionized Calcium to Cardiovascular Disease Endpoint and Family History of Hypertension

Abstract

Plasma ionized calcium and total calcium were measured on 271 individuals from 34 Utah pedigrees divided into groups defined by the method of pedigree ascertainment: 1) hypertension clusters, 2) early stroke death clusters and 3) clusters of early heart attack deaths. Normotensive individuals were also categorized by family history of hypertension. Members of stroke cluster pedigrees had higher mean plasma ionized Ca²⁺ than either hypertension pedigrees (p < 0.05) or coronary artery disease pedigrees which had the lowest concentrations (p < 0.001). Within the normotensive group, those subjects with a positive family history of hypertension exhibited significantly higher plasma ionized Ca²⁺ (2.18 ± 0.10 (S.D.) mEq/1) than individuals without a family history of hypertension (2.12 ± 0.08 mEq/1, p < 0.01). In medicated hypertensives, both ionized (p < 0.05) and total (p < 0.01) plasma calcium were higher than calcium levels in the normotensive negative family history subjects. Plasma ionized Ca²⁺ in the adult normotensives (N=134) had significant age corrected positive correlations with plasma sodium (r = 0.25, p < 0.01), potassium (r=0.29, p<0.001) and erythrocyte sodium-lithium countertransport values (r=0.20, p<0.05). These findings provide additional evidence that plasma ionized calcium concentrations may be important to help define the heterogeneity of hypertension in adult Americans.

Key Words:

• Ionized calcium
• blood pressure
• family history of hypertension
• cardiovascular disease
• stroke