Depending upon the electrocardiographic (ECG) changes produced by the damaged heart muscle, heart attacks has been divided into two types: –

  • Q wave infarction – The necrosis (deadening) of the affected area may involve the whole thickness of the muscle wall (trans mural infarction) due to complete blockage of the coronary artery. This manifestation as Q wave as an additional finding in ECG is referred to as Q wave infarction.
  • Non-Q wave infarction – When the arterial occlusion (blockage) is incomplete or when there is spontaneous lysis (dissolution) of the offending clot, only a part of the whole thickness of muscle wall (subendocardial infarction) become┬ánecrosed (or dead). It does not cause Q wave formation in the ECG and is referred to as non Q wave infarction. In such cases the risk of repeated attacks is high.