Case reports have documented reversible cardiac dysfunction in the setting of severely depressed extracellular calcium concentrations. The present systematic review and meta-analyses of individual patient data were conducted to further characterize the cardiac dysfunction associated with low serum calcium levels in the clinical setting. We searched Ovid MEDLINE, Embase, PubMed databases and the Cochrane Library and the Registry of Clinical Trials from 1948 through August 2011. Studies that evaluated low serum calcium and cardiac dysfunction were identified and included for review. A total of 43 studies comprised of 47 individual cases met inclusion criteria. Univariate linear regression analysis showed a statistically significant correlation between corrected QT interval (QTc) length and corrected total serum calcium level (B = -23.19, SE = 8.04, P = 0.01), left ventricular ejection fraction and corrected total serum calcium (B = 5.16, SE = 1.29, P < 0.01) and ionized serum calcium (B = 5.48, SE = 2.04, P = 0.03). Hypocalcemia may be associated with reversible cardiac dysfunction including QTc interval prolongation and depressed left ventricular systolic function. The available evidence is very limited and does not provide a rationale for a certain threshold or a recommendation for calcium replacement. Future research is needed in this important and common metabolic disorder.