PTH and Heart block: Calcium deposition in the cardiac conduction system induces progressive arrhythmia and one study has shown a high percentage of second- and third-degree atrioventricular block (69%) with dialysis.6 Among the factors postulated to promote the development of metastatic calcification, both elevated calcium-phosphorus product and increased parathyroid hormone levels are possible, and exploration or removal of the parathyroid glands should be considered if heart block is present.7