Bioimpedance analysis (BIA) is a commonly used method to estimate body composition by sending a low-level electrical current through the body. Manufacturers have traditionally recommended that patients with implanted cardiac devices like pacemakers, implantable cardioverter defibrillators (ICDs), or cardiac resynchronisation therapy devices (CRT-Ds) avoid BIA due to concerns about potential interference. However, a small study published in 2012 evaluated 20 patients with heart failure who had either an ICD or CRT-D device implanted. The researchers performed BIA on these patients while monitoring their devices in real time. They found no evidence of any interference from the BIA, including no telemetry disruption, no oversensing on the device leads, and no symptoms experienced by the patients. While this study suggests BIA may be safe in patients with certain cardiac implants, the researchers noted that further confirmatory studies with larger patient groups are still needed. As always, it's best to consult your doctor or cardiac electrophysiologist before undergoing any procedures or tests if you have an implanted cardiac device.