Reversible depression in myocardial performance in dogs with experimental phosphorus deficiency

Abstract

The effects of phosphorus depletion on cardiac muscle function in six awake dogs were evaluated with surgically implanted transducers to serially measure ascending aortic root blood flow and high fidelity left ventricular pressure. After the animals recovered from surgery, phosphorus depletion was induced by feeding them a synthetic phosphorus-deficient diet plus aluminum carbonate gel for 35 days, followed by the same diet with phosphorus supplementation for 21 days. In addition to the cardiac studies, sequential measurements of phosphorus content in skeletal muscle and phosphorus in serum were obtained to ascertain the level of phosphorus depeletion. Serum inorganic phosphorus concentration (mg/100 ml) decreased from 5.1 ± 0.1 on day 0 to 0.9 ± 0.1 on day 35 (P<0.01), and total muscle phosphorus (content mmol/100 g fat-free dry weight) decreased from 28.0 ± 0.2 on day 0 to 22.6 ± 0.5 on day 35 (P < 0.01). During the period of phosphorus depletion, there was no significant change in heart rate; however, stroke volume (milliliter) and peak blood flow velocity (centimeter per second) declined from 24 ± 2 to 17 ± 2 (P<0.01) and 121 ± 12 to 98 ± 7 (P<0.01), respectively. Maximum ascending aortic blood flow acceleration (centimeter per second square) and maximum left ventricular time rate of change of pressure (mm Hg per second) also decreased from 4,630 ± 313 to 3,817 ± 346 (P<0.01) and 2,582 ± 347 to 2,120 ± 297 (P<0.01) during phosphorus depletion. After repletion all values returned to control values. These results indicate that moderate diet induced phosphorus depletion can depress myocardial performance. With repletion of phosphorus, myocardial performance improves.