Overview of myocardial infarction
Chronic myocardial infarction is a pathologic condition that occurs 8 weeks after the onset of acute myocardial infarction.
The onset of symptoms such as panic, chest tightness, breathlessness, etc. when triggered by exertion or emotional stress.
History of acute myocardial infarction associated with triggers such as exertion, emotion and diet.
Drug therapy to prevent recurrence of myocardial infarction, and surgery if necessary.
Definition
Myocardial infarction is defined as an acute myocardial infarction that has occurred for more than 8 weeks.
There are pathologic Q waves on the ECG, with or without clinical symptoms, specifically related to the severity of ischemia [1].
There is imaging evidence of a zone of loss of viable myocardium, where myocardial thinning and hypocontractile function are present to the exclusion of other causes.
Staging
According to the location of necrotic myocardium, it can be categorized as old anterior wall, high lateral wall, lateral wall, and inferior wall myocardial infarction.
Chronic anterior myocardial infarction
Old myocardial infarction mainly occurs in the anterior wall of the left ventricle, usually supplied by the left anterior descending branch, and the electrocardiogram suggests that the ST-segment elevation in leads V1-V6.
The patient had a previous history of acute myocardial infarction.
Old high lateral wall myocardial infarction
Old high lateral wall myocardial infarction is defined as a high lateral wall myocardial infarction that has occurred for more than one month as an old lesion, and the site of thrombus occlusion can be the anterior descending branch or its branch diagonal branch.
An old lateral wall myocardial infarction is defined as the location of the lesion in which the infarction occurred, on the side of the ventricle.
Old inferior wall myocardial infarction
An old inferior wall myocardial infarction is characterized by ischemic necrosis of the myocardium of the right ventricle, usually supplied by the right coronary artery.
The ECG may show pathologic Q waves of II, III, and AVF. This type of Q wave on ECG is also known as necrotic Q wave [2].
Morbidity
This disease is relatively common, and epidemiologic surveys have shown that there are about 500,000 new cases of heart attack each year in China, and the number of existing heart attack patients has exceeded 2 million, and the number of patients with old myocardial infarction is also increasing year by year [1].
Causes
Causes of the disease
This disease occurs after a certain period of time after acute myocardial infarction, regardless of whether stenting or bypass surgery is performed or not, and some patients may not seek medical attention due to enduring chest pain or not perceiving significant chest pain without prompt treatment.
As to why there are no obvious chest pain symptoms there may be the following reasons.
The site of stenosis is a distal thin vessel with a mild degree of stenosis, or has developed its own collateral circulation, resulting in less severe myocardial ischemia.
The patient’s own nociceptive threshold is high and the pain is not felt significantly.
Patients with diabetes mellitus and other diseases have autonomic neuropathy, which in turn leads to pain insensitivity.
Symptoms
Main Symptoms
There are no obvious symptoms in old myocardial infarction in normal times, but panic, chest tightness, fatigue and other symptoms may appear after physical labor, and chest tightness, chest pain, profuse sweating, dyspnea and other symptoms may appear in acute attack.
Chest pain
Mainly in the anterior chest, the pain is often oppressive, dull or constrictive and usually appears after physical labor.
Chest tightness
Something is pressing on the chest and there is not enough air. Often causes accelerated breathing rate, deep breathing, sighing and other manifestations.
Panic
A rapid, slow or irregular heartbeat accompanied by an uncomfortable sensation in the heart area.
Heavy sweating
Heavy sweating can occur due to over-excitement of the sympathetic nerves.
Difficulty in breathing
Feeling of lack of air, labored breathing, need to breathe hard. Breathing may require opening the mouth and lifting the shoulders, or sitting and breathing may feel slightly more comfortable [3].
Complications
Heart failure.
Abbreviated as heart failure, old myocardial infarction leads to impaired pumping function of the heart, and cardiac output cannot meet the basic metabolic needs of systemic tissues, which is mainly manifested as dyspnea, activity limitation, and fluid retention.
Myocardial infarction
Recurrence of old myocardial infarction is possible, and patients may experience severe chest pain, chest tightness, and dyspnea.
Consultation
Department of Medicine
Cardiovascular Medicine
When chest pain, chest tightness, panic, sweating, fatigue, dizziness occur, it is recommended to consult a doctor promptly.
Emergency Department
When there is fainting, dyspnea, severe chest pain, it is recommended to consult a doctor promptly.
Preparation for medical treatment
Preparation for medical consultation: registration, preparation of information, common problems
Tips for seeking medical treatment
Be accompanied by family members and friends and avoid strenuous walking.
It is better to go to the doctor early in the morning on an empty stomach.
Preparation Checklist
Symptom list
Pay particular attention to the time of onset of symptoms, special manifestations, etc.
Is there any symptom of chest pain present? How long has it lasted?
Is there a trigger for the chest pain?
Are there any symptoms such as dyspnea, chest tightness, etc.? What are the specific manifestations?
Medical History Checklist
Any previous history of acute myocardial infarction?
Any history of coronary heart disease?
Any history of diabetes mellitus, hyperlipidemia, hypertension?
Any immediate family members with coronary heart disease or myocardial infarction?
What tests and treatments have been done in the past and what are the results?
Checklist
Test results in the past six months, which can be brought to the doctor’s office
Such as electrocardiogram, cardiac ultrasound examination report.
Medication list
Medication in the last 3 months, if any box or package, you can bring it with you to the doctor’s office
Antiplatelet drugs: aspirin, clopidogrel, etc.
Angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists: valsartan, chlorosartan, etc.
Beta receptor antagonists: atenolol, metoprolol, etc.
Diagnosis
Diagnosis is based on
Medical history
The patient has a history of acute myocardial infarction, hyperlipidemia, hypertension, diabetes mellitus, etc.
Clinical manifestations
Symptoms
Angina pectoris is the most common symptom of old myocardial infarction, and the patient may have repeated symptoms of exertional chest tightness or chest pain in daily life.
Patients with old myocardial infarction may have enlarged heart and reduced ejection fraction, resulting in dyspnea, shortness of breath, fatigue, and other symptoms.
Arrhythmias, such as frequent premature ventricular beats or ventricular tachycardia, can also occur, with symptoms such as palpitations, panic attacks, and chest tightness. In some cases, ventricular tachycardia is severe enough to cause blackouts or fainting.
Physical signs
In the presence of heart failure, there may be swelling of the lower extremities or the whole body.
Laboratory Tests
Serum markers of myocardial necrosis
Myocardial necrosis markers consist of two main categories: cardiac enzymes and cardiac troponin.
Myocardial necrosis markers can be used to determine the presence of acute myocardial infarction, and to initially understand the extent of myocardial necrosis and the prognosis of myocardial necrosis.
Blood Tests
Blood routine mainly detects the quality and quantity of tangible cells in the blood such as white blood cells, red blood cells and platelets, as well as morphological changes.
The purpose is to determine whether there is anemia, platelet function and other conditions, so as to facilitate the follow-up treatment.
It is important to note that the day before the blood collection, do not eat too greasy, high protein food, and avoid drinking alcohol. Alcohol content in the blood will directly affect the test results. During blood collection, patients should relax to avoid vasoconstriction caused by fear, which will increase the difficulty of blood collection.
Blood biochemistry
Blood biochemistry tests include blood glucose, blood lipids, liver and kidney functions.
The purpose of the examination is to understand the function of organs, assess the liver and kidney function, electrolytes and other conditions.
It is important to keep an empty stomach during the test and take care of your health. If you have a cold or fever, do not go for the test, otherwise the test results will be inaccurate, and try to take the test in the morning for a better diagnosis.
Blood gas analysis
Blood gas analysis is an analytical technique in which the acid-base balance and respiratory and oxidative functions are judged by directly measuring the three indicators of blood acidity and alkalinity (pH), partial pressure of oxygen (PO2), and partial pressure of carbon dioxide (PCO2) through the use of blood gas analyzers, and then using formulas to calculate the other indicators.
The purpose is to visually check for the presence of hypoxemia, hypercapnia, acidosis, and ionic disorders.
Electrocardiogram
The purpose is to assist in the diagnosis of acute myocardial infarction, clear localization, estimation of the evolution of the disease and prognosis. The patient should be calm and emotionally stable during the re-examination, and should not be overworked or exercised before the examination. The examination should be as relaxed as possible to ensure the quality of the examination.
Imaging examination
Coronary angiography
The purpose of this examination is to visually examine the coronary vessels (the vessels that caused the current disease) and other blood vessel stenosis.
Based on the results, the need for interventional procedures is determined.
Differential Diagnosis
Variant angina pectoris
Similarities: The nature of the pain during the attack is similar.
Differences: angina attacks are more frequent, each attack lasts for a shorter period of time, usually less than 15 minutes, and is not accompanied by fever, increase in white blood cells, increase in erythrocyte sedimentation rate or increase in serum cardiac enzymes; there is an increase in white blood cells during an attack of old myocardial infarction.
Acute pericarditis
Similarity: Both diseases may cause chest tightness and chest pain.
Differences
Acute pericarditis is usually caused by viral or bacterial infections, while old myocardial infarction is usually caused by a history of acute myocardial infarction, and is associated with factors such as fatigue, emotional stress, and diet.
Currently, the diagnostic criteria for acute pericarditis include the presence of pericardial friction, characteristic chest pain, suggestive electrocardiographic changes, and new or worsening pericardial effusion, two of which can be diagnosed as acute pericarditis.
Acute myocardial infarction
● Similarities: both have chest pain and chest tightness.
● Differences
Acute myocardial infarction is characterized by acute myocardial injury and necrosis, whereas old myocardial infarction is characterized by no acute myocardial injury or necrosis.
The treatment of acute myocardial infarction is different. Acute myocardial infarction often requires emergency interventional surgery to open the blocked coronary artery in time to save the surviving myocardium, while old myocardial infarction does not require emergency surgery.
Treatment
The principle of treatment: follow-up observation and drug treatment, for the reappearance of myocardial ischemia patients, the need for emergency treatment.
Treatment purpose: to restore myocardial perfusion and symptomatic supportive treatment as soon as possible, to avoid the emergence of life-threatening serious conditions, and to avoid reoccurrence of myocardial infarction [4].
Drug treatment
Dilation of coronary arteries
Dilating the coronary arteries, improving the blood supply to the heart, relieving symptoms, and maintaining the normal function of cardiomyocytes.
Such as isosorbide nitrate, isosorbide mononitrate, nitroglycerin and so on.
Adverse effects include hypotension, headache, head swelling. Blood pressure must be monitored.
Drugs to reduce myocardial oxygen consumption
By controlling the heart rate and lowering the blood pressure, the burden on the heart is reduced and the consumption of oxygen by the heart muscle is reduced.
Commonly used drugs include e.g. metoprolol, bisoprolol, atenolol.
Use with caution in cases of low blood pressure, slow heart rate, and acute cardiac insufficiency.
Antithrombotic drugs
Inhibit the formation of blood clots and avoid further increase of blood clots.
Commonly used antiplatelet agents such as aspirin, clopidogrel, tegretol, and anticoagulants such as heparin and low molecular weight heparin.
Lipid-regulating drugs
Regulate blood lipids by lowering total cholesterol, LDL cholesterol, etc. to slow down the progression of the disease.
Commonly used drugs include statins (e.g., simvastatin, atorvastatin), fibrates (e.g., fenofibrate), ezetimibe, PCSK9 inhibitors (e.g., eloxacinumab), and so on.
Adverse reactions include hepatic impairment, rhabdomyolysis, and gastrointestinal upset.
Other drugs
Calcium channel blockers, such as diltiazem and verapamil, can prevent the extent of myocardial infarction and improve prognosis.
Angiotensin-converting enzyme inhibitors (ACEI) such as captopril and enalapril can help myocardial remodeling during the recovery period and reduce the incidence of heart failure, thus reducing mortality. Angiotensin II receptor antagonists (ARBs) such as valsartan and chlorosartan are available for those who cannot tolerate ACEIs [5].
Surgical treatment
Percutaneous coronary intervention (PCI)
The therapeutic balloon and stent are delivered to the diseased blood vessel through a blood vessel at the root of the wrist or thigh to dilate the blood vessel, maintain blood flow to the vessel, and ensure blood supply to the tissues.
Specific treatments include balloon angioplasty and stenting.
Coronary artery bypass grafting
Coronary artery bypass grafting is required when the disease is severe and the patency of the blood vessels and blood supply to the heart muscle cannot be improved by other treatments.
Coronary artery bypass grafting is a procedure in which a section of blood vessel is extracted from a healthy part of the body and connected directly from a large vessel to a normal blood vessel in the remote part of the diseased area, bypassing the diseased area to ensure blood supply to the tissues and maintain normal function of the organs [6].
Prognosis
Cured
Untreated
With the progression of the disease, the patient’s symptoms may gradually aggravate, and even recurrent acute myocardial infarction, heart failure and sudden death may occur, seriously affecting normal life and jeopardizing life and health.
After treatment
As the myocardium is necrotic, the disease cannot be completely cured, but it can try to restore the vitality of the non-necrotic myocardium, relieve the symptoms and avoid recurrence of myocardial infarction.
Hazardous
Patients with obsolete myocardial infarction will have panic, chest tightness and fatigue after physical labor, which will affect normal work and life.
Obsolete myocardial infarction may lead to serious complications such as heart failure if not treated in time, which may lead to death in severe cases [7].
Daily
Daily management
Dietary management
Pay attention to a low-salt, low-fat diet and a healthy diet structure that includes fruits, vegetables, grains, fish, and low-fat or skim milk products.
Minimize food containing saturated fat and trans fat, such as animal offal, fried food, and western desserts [8].
Life management
Physical exercise should be carried out in moderation to improve body resistance and reduce the risk of disease.
Stop smoking and limit alcohol, control blood pressure, blood lipid and blood sugar.
Exercise appropriately and keep a happy mood.
Psychological support
It is necessary to provide psychological counseling and health education for patients [9].
Disease monitoring
The disease may recur, and if symptoms such as chest pain, chest tightness, profuse sweating, and dyspnea recur in daily life, timely medical attention is needed.
Blood pressure is monitored and recorded daily.
Follow-up review
Importance of follow-up: Regular follow-up helps to detect recurrence and disease progression in time.
When to follow up: During and after treatment, regular hospital checkups are needed.
Tests to be done during follow-up: Since each patient’s condition is different, please follow the doctor’s instructions for the tests.
Prevention
Actively treat hypertension, diabetes mellitus, dyslipidemia and other diseases, strictly follow the doctor’s instructions for regular use of medication, regular review.
People who are prone to mental stress should combine work and rest, actively seek the help of family members or psychologists, relax moderately, and relieve tension.
Middle-aged and elderly people as well as post-menopausal women, and patients with similar diseases in their families should have regular medical checkups and seek timely medical attention if there is any abnormality.
Adopt good living habits: pay attention to light diet, balanced diet, maintain regular work and rest habits, moderate physical exercise, ensure adequate nutrition, improve body resistance, reduce the risk of disease [10].