Nonsuper-selective venous sampling for persistent hyperparathyroidism using a systemic hypocalcemic challenge

To describe a new protocol employing an acute systemic hypocalcemic challenge (SHC) aimed at augmenting the parathyroid hormone (PTH) gradient to enable nonsuper-selective venous sampling (VS) in patients with persistent primary hyperparathyroidism (PHPT). In a retrospective study, 37 patients (39 studies20 SHC, 19 super-selective VS) who underwent VS for persistent or recurrent PHPT were examined. Study patients were pretreated with intravenous hydration, diuretics, and bicarbonate to induce temporary relative hypocalcemia and then underwent nonsuper-selective VS targeted at large vessels within the neck and chest with rapid PTH testing. The traditional VS protocol involved super-selective VS with arteriography. SHC decreased ionized calcium by 0.098 mmol/L ± 0.18 (P = .07) and increased peripheral PTH by 10.2 pg/mL (P = .58). Positive VS gradients, defined as a < 1.4-fold difference from baseline to after SHC, were detected in 95% of patients. VS findings guided successful surgery in 77% of SHC cases and 90% of super-selective VS cases; the peak gradient site was concordant with operative findings in 46% of SHC cases and 80% of super-selective VS cases. Avoidance of super-selective sampling decreased mean fluoroscopy time from 91 minutes to 33 minutes and decreased contrast material administered from 204 mL to 63 mL (both P < .0001). The SHC protocol to enable nonsuper-selective VS in patients with persistent PHPT had the same ability as super-selective VS to detect a positive (< 1.4-fold) PTH gradient, was associated with decreased accuracy in identifying the site of the adenoma compared with super-selective VS, and significantly decreased contrast material used and fluoroscopy time.