Apical ischemia indicates there is some vessel blockage in the apical (top) region of the left ventricle. It would be somewhat serious if there is heart wall movement impairment (hypokinesis), and/or lower than normal EF (ejection fraction: normal 55 to 75%) and that percentage represents the amount of blood pumped into circulation with each heartbeat.
Was the test discontinued before completion? The test would be discontiuned due to ekg readings, etc. or the individual's chest pain, fatgue, etc. That could indicate a heart, respiratory problem, or the individuals conditioning. The chest discomfort can be due to a respiratory problem...
Speaking to your cardiologist is the right thing to do.