instruction: how many patients whose diagnoses long title is paroxysmal ventricular tachycardia and drug type is main?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE diagnoses.long_title = "Paroxysmal ventricular tachycardia" AND prescriptions.drug_type = "MAIN"