This is addressed in the Star Fleet Medical Reference Manual, considered a canon source of information about the physiology of aliens.
HEART AND LUNGS
The Vulcan heart beats at the astounding rate of 242 bests per minute.
The average blood pressure is 90 systolic, and 40 diastolic. This
phenomenon is explained in part by the extremely dilated blood vessels
of Vulcans. Large diameter blood vessels are an additional aid in
cooling the body, allowing for greater cooling surface.
The Vulcan heart is located where one would expect to find the Terran
liver, leaving room for the somewhat larger Vulcan lung assembly. In
consequence, the cartilage that normally protects the Terran heart
extends an extra 3.5 cm downward in a Vulcan in order to protect this
vital organ.