“The Heart is a House”: A Heuristic for Generating Cardiac Differential Diagnoses

BACKGROUND: Differential diagnosis (DDx) is a core clinical reasoning skill that all medical students and physicians must acquire and develop. Metamemory techniques (MMTs), including mnemonic devices and other heuristics, are frequently taught to students as a means of enhancing DDx generation. The Heart is A House (HIAH), an MMT that works by prompting students to think about cardiac disease in terms of four structural subsystems, can be used to facilitate the generation of cardiac differentials, but its efficacy has not been studied. METHODS: In a 3-hour DDx workshop, second-year medical students were given a brief case vignette of a patient with chest pain and dyspnea and asked to generate initial differential diagnoses before and after learning HIAH. Descriptive statistics and paired T-tests were used to compare the sizes of cardiac-only and total differentials pre-/post-HIAH. Cardiac diagnoses were classified according to the structural categories described by HIAH, and Simpson's Diversity Index (SDI) was used to evaluate the effect of HIAH on the variety of cardiac diagnoses produced. RESULTS: All students in the course (N = 111) submitted pre-post differential lists. The mean number of diagnoses included in their differentials did not change significantly after exposure to HIAH (7.98 vs. 8.71, P = .09). However, the number of potentially correct cardiac diagnoses increased from 1.79 to 4.75 (P < .0001), and the variety of structure/function cardiac categories considered by students increased more than twofold (from an SDI of 0.16 to 0.4, P < .0001). These increases were accompanied by a small increase in incorrect diagnoses ( + 2.47%, P = .0003) and a larger decrease in potentially correct noncardiac diagnoses (−41.88%, P < .0001). CONCLUSION: The use of HIAH was associated with an increase in the size and variety of cardiac differentials. This increase may have come at the cost of a reduced noncardiac differential. Educators may find HIAH useful for guiding students as they reason through cases involving potential cardiac etiologies. As with all heuristics, care must be exercised to avoid introducing unwanted bias.