instruction: how many patients were diagnosed with av block - complete heart block during the same hospital encounter until 2104 after having been previously diagnosed with congestive heart failure?
response: SELECT COUNT(DISTINCT t1.uniquepid) FROM (SELECT patient.uniquepid, diagnosis.diagnosistime, patient.patienthealthsystemstayid FROM diagnosis JOIN patient ON diagnosis.patientunitstayid = patient.patientunitstayid WHERE diagnosis.diagnosisname = 'av block - complete heart block' AND STRFTIME('%y', diagnosis.diagnosistime) <= '2104') AS t1 JOIN (SELECT patient.uniquepid, diagnosis.diagnosistime, patient.patienthealthsystemstayid FROM diagnosis JOIN patient ON diagnosis.patientunitstayid = patient.patientunitstayid WHERE diagnosis.diagnosisname = 'congestive heart failure' AND STRFTIME('%y', diagnosis.diagnosistime) <= '2104') AS t2 WHERE t1.diagnosistime < t2.diagnosistime AND t1.patienthealthsystemstayid = t2.patienthealthsystemstayid