The low temperature may also cause the heart coronarospasm, causes the cardiac muscle ischemia oxygen deficit, may induce the angina pectoris, the heart rhythm not to be uneven.
Cardiac muscle tissue is also striped, or striated, but unlike skeletal muscle tissue, their cells are generally uninucleate, meaning that they have just one nucleus.
With your heart beating two-thirds faster than normal, before you even broke a sweat, your cardiac muscle would experience a lot of extra wear and tear.