Participants and procedure
The study was embedded within a lecture on structural heart disease in the Cardiology curriculum for first-year medical students at Western University. The participants had competed 5 months of medical school on topics unrelated to Cardiology prior to the study.
We utilized a single-blind randomized controlled trial design. Students were randomized using a random number generator.
Both lectures were designed around the same objectives: describe and classify normal heart sounds, abnormal heart sounds and cardiac murmurs. Ten structural lesions (aortic stenosis, atrial septal defect, hypertrophic cardiomyopathy, tricuspid regurgitation, ventricular septal defect, mitral regurgitation, mitral valve prolapse, aortic regurgitation, mitral stenosis and pericardial rub) were described.
The lectures contained the same number of slides (81 slides) with the same average number of words per slide (21 words). Both lectures were given in a standard 1 hour lecture time frame in lecture halls used in the undergraduate medical curriculum at Western University. The lectures were given simultaneously by two different lecturers.
Both lectures began with a review of the physiology of normal heart sounds, followed by a discussion of abnormal heart sounds.
To ensure that no group was significantly disadvantaged prior to the course examination, both lectures were repeated immediately following data collection.
The details of each lesion were listed in succession. The lecturer outlined the character, radiation, extra sounds, and palpable findings for each murmur.
A junior faculty member who had provided this lecture in previous years delivered the lecture.
The schema-based lecture presented the same introduction. Murmurs were presented according to timing and location using an adaptation of a published schema (Fig. 1; ). For example, when systolic murmurs at the base of the heart were described, a differential diagnosis of aortic stenosis, atrial septal defect and hypertrophic cardiomyopathy was presented. The lecturer then explained the pathophysiology and associated findings that would allow differentiation between the differential provided.
The lecture was given by a junior lecturer who had used this schema in previous research studies .
Immediately following the lecture, participants completed a cognitive load assessment about the lecture and a four-item test assessing diagnostic performance.
The cognitive load assessment was based on a previously validated tool  to assess the subcomponents of cognitive load. Each subcomponent consisted of 3–4 individual questions on a 10-point scale. Subcomponent scores were added to arrive at a score for intrinsic (maximum 30 points), extraneous (maximum 30 points) and germane (maximum 40 points) cognitive load.
The four written multiple-choice questions were generated by three experts in cardiac auscultation. The questions provided details of the cardiac physical exam. Participants provided the diagnosis without the aid of any instructional materials.
Three weeks following the study date, participants rated the lecturers on a 7-point scale (1 = below expectations, 4 = average, 7 = outstanding).
Independent t-tests were performed to compare the cognitive load assessments and written questions. Lecturer ratings were compared with a paired t-test.
Ethics approval was granted by the Western University Research Ethics Board.