Altered ionized magnesium and calcium in patients with primary pulmonary hypertension

Purpose: Primary pulmonary hypertension (PPH) patients exhibit impaired vasodilatation and often severe vasoconstriction of the pulmonary arteries. Animal models suggest that magnesium and calcium may play a crucial role. In this study we compared ionized Mg (Mgi) and Ca (Cai) in PPH patients to healthy controls and correlated ion levels with hemodynamic responses in PPH patients after intravenous adenosine. Methods: Arterial blood samples were collected before and after adenosine infusion in 11 patients (3 males, 8 females, 40±4 years old) with PPH undergoing a cardiac catheterization. Baseline Pulmonary artery systolic pressure and pulmonary vascular resistance (PVR) ranged from 70-142 mmHs and 712-1800 dynes-s-cm-⁵. Ionized Mg and Ca were determined with ion selective electrodes. Total Mg, Ca and albumin were simultaneously measure on all samples. Control values were obtained from plasma of 11 age matched, healthy volunteers. mM/L (mean±SE) Group N Mg_i Total Mg Ca_i Ca_i/Mg_i 1. control 11 .61±.01 .84±.04 1.23±.02 2.02±.06 2. All 11 .53*±.01 .78±.02 1.24+.01 2.35*±.1 3. low Mg 5 .48∞±.01 .74±.04 1.24±.01 2.56∞±.1 *P<0.001 group 1 vs 2, ∞P<.01 group 3 vs 1&2. Conclusions: All PPH patients had a significantly lower Mgi when compared to healthy controls. Change in PVR in group 2 was 26% vs 20% in group 3. The 5 patients with the lowest Mg_i and highest Ca_i/Mg_i ratio had the smallest change in PVR. Clinical Implications: These data display a basic derangement in Mg and Ca metabolism in patients with PPH that could help explain drug responses (ie. Ca channel blockers) and lead to new therapeutic strategies.