instruction: give me the number of patients whose procedure long title is initial insertion of transvenous leads [electrodes] into atrium and ventricle and lab test fluid is joint fluid?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN procedures ON demographic.hadm_id = procedures.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE procedures.long_title = "Initial insertion of transvenous leads [electrodes] into atrium and ventricle" AND lab.fluid = "Joint Fluid"