An old myocardial infarction usually refers to a myocardial infarction that occurs six months after an acute myocardial infarction and may lead to angina pectoris, arrhythmias, and formation of ventricular wall tumors, and therefore has the potential to be dangerous. 1. Old myocardial infarction may be characterized by an attack of angina that worsens suddenly. The pain is accompanied by nausea and vomiting, profuse sweating or marked bradycardia. 2. Chronic myocardial infarction can also cause cardiac arrhythmias such as atrial and ventricular premature beats, conduction block, etc., and may lead to myocardial hypertrophy until heart failure. 3. If the infarction area is too large, or the blocked blood vessels are not unblocked in time, ventricular wall tumor may also be formed, affecting the normal diastolic and contractile function of the heart. Preventive measures include not lifting heavy objects or overworking, adjusting emotions and relaxing mood, exercising appropriately but not excessively, not bathing on a full stomach or under hunger, and paying attention to climate change. Do not panic if you have the above symptoms, immediately bed rest, keep quiet, sublingual nitroglycerin at the same time to call the emergency number. Specific treatment should follow the doctor’s advice.