Purpose
To determine whether a teaching strategy with ECG teaching spaced throughout the year leads to better interpretation skills than a one-class strategy. ECG interpretation is a medical Entrustable Professional Activity. Clerkship Directors in Internal Medicine (CDIM) agree on interpretation acumen’s importance (1). Despite this, interpretation skills of graduating students are poor (2,3). ECG instruction has no “gold standard”. 3rd year ECG teaching typically occurs during IM Clerkship. Spaced learning engenders better retention. We hypothesized that ECG classes spaced through 3rd year would improve interpretation skills.

Methods
Third-year student volunteers were randomized to one ECG interpretation class during IM Clerkship (control) or one class plus quarterly small-group classes (intervention). A Board-Certified Cardiologist taught all classes. An ECG test (graded 0 to 100%) developed to assess CDIM Survey ECG diagnoses was given at the beginning of and end of medical school 3rd year. The change in scores was analyzed by t-test and multiple regression with pre-test score, group, and their interaction as predictors.

Results
There was greater improvement in scores in intervention group (24.6±15.8%(SD)) versus control (7.5±15.4% p=0.003, t-test). In the regression analysis, lower pre-scores were associated with greater change in score and that effect was greater in the intervention group (interaction p=0.037). The change in score increased by 0.99 +/- 0.21% for each unit % decrement in pre-score in the intervention group compared to controls where lower pre-scores increased the improvement by only 0.36±0.27 % per unit % decrement in pre-test score. The intervention improved pre to post-change in scores more than in controls and preferentially offered greater improvement to those with low pre-test scores.

Conclusions
Spacing out ECG learning in small groups throughout 3rd year leads to improved interpretation skills at year-end; the greatest gains in skills occurred for students with lower pre-test scores.