Myocardium (cardiac muscle tissue) must rhythmically contract for a lifetime. This requires a considerable amount of energy production by the cells. You would expect to see a relatively high amount of?

You would expect to see a relatively high amount of mitochondria in myocardium cells, as these organelles are responsible for producing the energy (ATP) needed for continuous contraction. Additionally, there would be an abundance of myoglobin to store oxygen and a rich supply of capillaries to ensure adequate blood flow and nutrient delivery to sustain the high metabolic demands of cardiac muscle tissue.