There are various options, but for long periods single lead devices are often used, can't really walk around for 30 days with a 12 lead holter strapped to you..

There are various options, but for long periods single lead devices are often used, can't really walk around for 30 days with a 12 lead holter strapped to you...would make bathing rather difficult. It's possible to implant small loop recorders under the skin on the chest. These can record for months. Those are mostly useful in cases where symptoms occur infrequently.