###HUMAN: What is the number of patients diagnosed with rheumatic heart failure (congestive) who have a delta abnormal lab test?, ###ASSISTANT: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE diagnoses.long_title = "Rheumatic heart failure (congestive)" AND lab.flag = "delta"