Coronary blood flow (Right ventricle), true is:
Although maximum blood flow occurs during diastole in left ventricle, in right ventricle it is maximum during systole. 
Because diastole is shorter when the heart rate is high, left  ventricular  coronary flow is reduced during tachycardia. On the other hand, the pressure differential between the aorta and the right ventricle, and the differential between the aorta and the atria, are somewhat greater during systole than during diastole. Consequently, coronary flow in those parts of the heart is not appreciably reduced during systole. Flow in the right and left coronary arteries is shown in figure.
500 mL/min
Maximum during systole
Adenosine decreases it
More than skin