eTable 2.

Observed differences between humans and baboons that may impact cardiovascular modeling

Observation	Human	Baboon	Consequence
Liver	Right sided	Transverse	Precludes retroflexed gastric TEE views or subxiphoid needle approaches
Cardiac orientation	Normal = levocardia	Normal = levocardia	Base of Apex alignment and orientation within the chest is similar to human and not transversely situated as in four-legged food stock animals
Right ventricle wall thickness	“Normal”	Thinner	Less myocardial reserve; poorly tolerates distention, infundibular incisions, or acutely increased afterloads; may be useful for Fontan modeling
Left ventricle muscle mass	“Normal”	Thicker with essentially concentric hypertrophy as compared to human	Diastolic stiffness. Narrow left ventricular outflow tract; optimized cardioplegia strategies required
Right coronary ostia	Typically smaller than left main	Miniscule	Smallest coronary perfusion cannulae (1mm) cannot cannulate
Splanchnic venous reserve	Limited	Large blood volume for autotransfusion via autonomic reflexes	Careful weaning from cardiopulmonary bypass with surgeon and TEE chamber volume monitoring to avoid acute cardiac distention. Avoid “light” anesthesia. After CPB, transfuse pump blood residual slowly
Arterial wall thickness	Large lumen to wall thickness ratio	Very thick and stiff and hyper - vasoconstrictive	Peripheral arterial cannulation precluded; not likely a good species for transvascular catheter methods; enhanced fight/flight responses; older baboons develop hypertension and presbycardia
Body mass	Evolves with age from upper body to lower body dominant	Upper body dominant	BSA calculations should be based on formulae that assume less contribution from lower body mass (eg, Haycock Formula) when normalizing measurement to BSA (eg, indexing EOA of valves)
Demeanor	Age dependent calm	Aggressive potentially bellicose	All interventions under sedation/anesthesia; perioperative management and husbandry by experts with proper caging, socialization procedures, management techniques, etc. required

Note: Regional Primate Centers are supported by NIH Comparative Medicine Programs (formally in the National Center for Research Resources) and tasked with optimizing breeding, experimental modeling, availability, medical knowledge for many Old and New World species for use in biomedical research; we found it preferable to travel as a team and operate onsite at the Texas Biomedical Research Institute where subhuman primate veterinary medicine and husbandry are optimized. However, this adds to the additional limitation of expense.