Medtronic announced today that its latest generation of cardiac rhythm monitors is now for sale in the United States.

The Reveal XT is meant to help physicians detect and diagnose irregular heart rhythms. The device looks like a thumb drive and is implanted in the patient's chest just under the skin.

St. Jude Medical sells a similar product called the SJM Confirm, and there's a nonsurgical alternative called a Holter monitor, a first-sized machine patients carry with them for a day or two.

The implantable cardiac monitors are useful when physicans can not detect the irregular rhythms from that short-term data and want to monitor a patient over a longer period of time.

Medtronic said its Reveal XT device is the first that will help physicians monitor atrial fibrillation, a specific arrhythmia found in the upper chamber of the heart.

The Fridley-based company recently acquired two companies that make devices for treating atrial fibrillation, CryoCath and Ablation Frontiers.