How is the heart uniquely suited to its function?
It is a robust, reliable pump.
Curious question, as ALL of the bodies organs are "uniquely suited" to their functions.
The core function of the heart is to provide continuous and consistent blood flow through the circulatory system. Its "uniqueness" is the extremely consistent and automatic rate of pumping - controlled by demands on the body from exertion or disease.
It does not control blood pressure, but maintains the required blood flow despite restrictions (which DO add stress to the heart muscles). It is a simple two-chamber pump that maintains pressure and volumetric flow in one direction.