No. Heart attack means damage to a region of the heart muscle due to loss of blood supply, usually due to blockage of a coronary artery. Cardiac arrest means stopping of the heart which is mostly due to abnormality in the electrical activity of the heart. But a heart attack can cause a cardiac arrest, though heart attack is not the only cause of a cardiac arrest. Cardiac arrest can occur due to other causes like electrical disorders of the heart which itself may be due to inherited heart rhythm disorders, abnormalities in the blood electrolytes, toxins etc.