Abstract
Introduction: The understanding of gross cardiac anatomy has been relatively stable over the last
80 years, reliant on well-established autopsy findings. The advent of dynamic imaging by cardiac
MRI and CT provides a window to view anatomic features in vivo, providing insights typically
masked at autopsy due to death.
Hypothesis: We hypothesize that cardiac magnetic resonance (CMR) with its high spatial and
temporal resolution allows detection of anatomic features not previously appreciated at autopsy.
Methods: Two hundred fifty-five sequential, CMR examinations were retrospectively examined
to describe the anatomic features of the LV (left ventricular) PM (papillary muscles). Specifically,
the origin of the base of the PM was delineated. The insertion of the PM was seen in 255/255
patients.
Results: In 249 out of 255 patients (97.6%), the appearance of the PM was not a uniform muscle
arising from the inner face of the LV myocardium, but was a finger-like series of long, slender
trabeculae carneae traversing >1 cm before inserting into the main body of PM challenging our
previous understanding of PM anatomy.
Conclusion: The capabilities of dynamic CMR to view cardiac features in vivo non-invasively
provides a useful tool to study cardiac anatomy. Unlike the widely accepted representation of
papillary muscles, uniformly arising from the floor of the LV, the base resolves into a ‘cypress-tree’
root-like structure with multiple thin projections before coalescing into a thick muscle head. Such
observations have far reaching clinical implications in areas such as mitral regurgitation, post-MI
remodeling and electrical transmission of the His-Purkinje system, and further work is indicated
to delineate the role of non-invasive imaging in these areas.