Hypocalcemic myocardial dysfunction: short- and long-term improvement with calcium replacement.

The effects of short- and long-term calcium replacement on myocardial function in six asymptomatic patients (age 48 +/- 3, mean +/- SEM) with hypocalcemia complicating surgical hypoparathyroidism were studied. Cardiac output was determined by ascending aortic continuous wave Doppler assessment and was measured as minute distance. During intravenous calcium replacement at rest, ascending aortic minute distance increased from 6.75 +/- 1.10 to 9.17 +/- 1.29 m as the calcium level rose from 1.76 +/- 0.08 to 2.06 +/- 0.19 mmol/L without changes in heart rate and blood pressure (p less than 0.01). The peak velocity and acceleration of blood flow derived from Doppler measurement showed a similar rise during calcium infusion. Symptom-limited cycle ergometry was performed before and 3 months after normalization of calcium by long-term oral therapy. Although the resting cardiac output was unchanged, the maximum cardiac output at peak exercise also increased from a minute distance of 11.58 +/- 1.84 to 15.37 +/- 2.28 m (p less than 0.05), together with an increase of maximum heart rate from 136 to 149 beats/min (p less than 0.05). Exercise duration was also prolonged from 11.9 +/- 2.9 to 13.0 +/- 2.8 minutes. Thus hypocalcemia impairs cardiac performance, but this impairment is reversible with calcium replacement.