SCOTTSDALE, Ariz. — Stun gun maker Taser International Inc. on Friday said an independent study found that its stun guns had little effect on the heart functions of humans.

Shares of Taser, which have declined since the start of the year on controversy over the safety of its products, rose 18 cents to close at $11.38 in Friday trading on the Nasdaq Stock Market, where they have traded in a 52-week range of $7.33 to $33.45.

In a pilot study of 24 volunteer human subjects, Taser said physicians “found no significant cardiac dysrhythmias” immediately after subjects were exposed to an electrical shock from one of its devices. The study evaluated changes in the volunteers’ heart behavior through monitoring activity on an electrocardiogram immediately before and after they were exposed to its Taser X26 gun, the company said.

An abstract of the study was published in a supplemental edition of Academic Emergency Medicine, and the complete study will be presented at the Society of Academic Emergency Medicine in New York starting May 22, Taser said.