This study is the first, to our knowledge, to demonstrate that HD increases QTc dispersion if a low-calcium (dCa++1.25) dialysate is used. This indicates that the use of low-calcium dialysate may predispose HD patients to ventricular arrhythmias and that perhaps it should be avoided, at least when treating patients with pre-existing cardiac disease.

Objective: Our aim was to study the effect of primary hyperparathyroidism (PHPT) and parathyroidectomy (PTX) on left ventricular (LV) wall thicknesses and systolic and diastolic function. Methods: Fifteen patients with untreated PHPT were evaluated by applying Doppler and digitized M-mode echocardiography before and 2–3 months after PTX. Fifteen age- and sex-matched healthy controls were also examined echocardiographically. Results: Prior to PTX, interventricular septal thickness (IVST), LV mass (LVM), aortic root dimension and left atrium dimension were greater and LV fractional shortening was slightly decreased in patients as compared to controls. Significantly increased LV peak late diastolic velocity (A_max) and isovolumic relaxation time, and a slightly decreased ratio of peak early to peak late diastolic velocities (E/A_max) in the patients indicated impairment of LV diastolic function in hyperparathyroidism. PTX reduced serum total Ca from 2.79 ± 0.13 to 2.39 ± 0.09 mmol/l (p < 0.001) and tended to reduce IVST [10.6 ± 2.1 vs. 10.4 ± 2.0 mm; not significant (n.s.)], LV posterior wall thickness (9.6 ± 2.0 vs. 9.2 ± 1.0 mm, n.s.) and LVM (250 ± 102 vs. 213 ± 42 g; n.s.). Before PTX, there was a significant correlation between serum total Ca and LVM (r = 0.63, p < 0.05), and the PTX-induced change in serum total calcium correlated with the change in LVM (r = 0.59, p < 0.05). PTX induced no significant changes in LV systolic or diastolic function during the follow-up of 2–3 months. Conclusions: The present findings indicate that PHPT induces LV hypertrophy, slight impairment of LV systolic function and significant impairment of LV diastolic function, which are not substantially improved after TX and 2–3 months of normocalcemia.

HD with high-calcium (dCa++1. 75 mmol/liter) dialysate impairs LV relaxation when compared with lower calcium dialysate (dCa++1.25 and dCa++1.5 mmol/liter) treatments.

This 8-week study investigated the effects of increasing dietary Ca2+ content from 1.0% to 3.0% and hypercalcemia induced by oral 1alpha-OH vitamin D3 (1OH-D3, 1.2 microg/kg), on arterial tone in NaCl-hypertensive rats. The high-Ca2+ diet completely prevented the increase in blood pressure induced by the 6.0% NaCl chow, while plasma total Ca2+ and body weight were not different from controls. The 1OH-D3 treatment moderately elevated plasma total Ca2+ and attenuated the NaCl-induced rise in blood pressure, but also impaired weight gain. The tone of isolated mesenteric arterial rings was examined at the end of study. The endothelium-independent relaxations to nitroprusside, isoproterenol, and cromakalim were impaired in NaCl-hypertension. Experiments with NG-nitro-l-arginine methyl ester and tetraethylammonium in vitro suggested that both the nitric oxide- and hyperpolarization-mediated components of endothelium-dependent relaxation to acetylcholine were reduced in NaCl-hypertensive rats. All of the impaired relaxations in NaCl hypertension were normalized by concomitant Ca2+ supplementation. The 1OH-D3 treatment did not affect vascular relaxation, but it attenuated maximal contractile responses induced by norepinephrine and KCl by more than 50%. The reduced vasoconstrictor responses could not be explained by increased apoptosis in the vessel wall, but calcification may have played a role, since moderate signs of medial or adventitial calcification were observed in the aortic preparations after the 1OH-D3 treatment. In conclusion, a high-Ca2+ diet, which did not cause hypercalcemia, normalized blood pressure and endothelium-dependent and endothelium-independent vasorelaxation in NaCl-hypertensive rats. In contrast, chronic hypercalcemia induced by 1OH-D3 was associated with moderately lowered blood pressure, possibly because of reduced vasoconstrictor responses in arterial smooth muscle.