 In a person with an underlying heart condition like coronary artery disease, heart valve problem, arrhythmias or high blood pressure, the heart doesn't get enough blood (i.e. not enough oxygen to the heart muscles). 
In a person with an underlying heart condition like coronary artery disease , heart valve problem , arrhythmias or high blood pressure , the heart does n't get enough blood ( i.e. not enough oxygen to the heart muscles ) .