Can you tell me if on an ecg, what does a "persistent s-wave ( v5-v6 )" and mean?

Depends: A small S wave in these leads is usually normal. A prominent S-wave may be seen in patients with right sided overload conditions, such as pulmonary disease. A large S wave in V1 and lead I when the QRS is wide is seen in right bundle branch block (RBBB). In rare cases, a person with dextrocardia may be diagnosed by ECG with one feature being a persistent s-wave in V5-V6. Review with your doctor.

Ecg: Persistent S wave in the lateral precordium doesn't have any particular evil important, it is often a normal finding. Occasionally it can be seen with pathologic conditions but there are generally other associated findings.