OBJECTIVES: To evaluate operational definitions for cardiac events related to QT prolongation, such as paroxysmal ventricular tachycardia, ventricular fibrillation and flutter, cardiac arrest, and sudden cardiac death, in retrospective studies using administrative databases. METHODS: Using PubMed, we searched for studies that retrospectively identified cardiac events related to QT prolongation in administrative or claims databases and were published between January 2000 and September 2014. Selection for full-text review was based on a preliminary review of titles and abstracts.  RESULTS: Our initial search yielded 988 articles from which five were selected for inclusion after full-text review. Case report, clinical trial, congenital long QT syndrome, cardiac event not related to QT prolongation, and electrocardiography utilization are reasons for exclusion. Seven additional articles were identified from the references of these articles. The twelve included articles consist of four cohort studies (33%), three case-control studies (25%), three validation studies (25%), and two descriptive studies (17%). Nine studies (75%) utilized databases from the United States, five (42%) of which used Medicaid data, and three (25%) used European data. The most common operation definitions for cardiac events related to QT prolongation were primary discharge diagnosis of long QT-related cardiac events (75%) and sudden cardiac death (25%). The most common administrative codes utilized were ICD-9 (83%) and ICD-10 (17%). The most frequently utilized ICD-9 diagnosis code was 427.x (100%, cardiac dysrhythmias, ICD-10: I47-49), followed by 426.x (33%, conduction disorders, ICD-10: I44-45), and 798.x (33%, sudden death, cause unknown, ICD-10: R96). Six studies (50%) reviewed medical records to validate the diagnosis codes. Positive predictive values ranged from 77-94% when defining cardiac events related to QT prolongation using ICD-9 codes 426.x or 427.x. CONCLUSIONS: In administrative databases, ICD-9 codes 426.x and 427.x as the principle discharge diagnosis or underlying cause of death are commonly used to identify cardiac events related to QT prolongation.