Coronary Artery Disease Prevention

Time edited：2018/05

    Coronary heart disease (CAD) also called as coronary heart disease (CHD), one of the most lethal diseases nowadays, is responsible for tens of thousands of deaths every year.

    Heart is a critical organ in the human body. It is a never resting pump, which supply oxygen and nutrients through blood vascular system to each cell of the whole body, supporting all metabolism in human body.

    But, how does our heart obtain its own oxygen and nutrition?

    The main artery leaving the left ventricle is called the aorta. At where the aorta leaves left ventricle exist a bypass called coronary artery, which then branches forming “coronary circulation” surrounding the heart and is responsible for the supply of oxygen and nutrients for cardiac muscle.

    A main risk factor for CAD is atherosclerosis. The pathogenesis of atherosclerosis is complicated including, dyslipidemia, endothelial dysfunction, inflammation, and so on^[i][ii].

    For example, dyslipidemia play a critical role in the development of atherosclerosis, which is a disease that abnormal amount of lipids in the blood. The lipids accumulate at the arterial endothelial cells, forming white plaque. If the plaque located at coronary artery, then may causing coronary artery stenosis, reducing the oxygen supply to the heart which leads to angina. When the plaque rupture and unfortunately form thrombus (blood clot), which block the blood circulation, will cause acute myocardial infarction (AMI) and even sudden death.

    Another type of angina, variant angina, on the other hand was first described by  Prinzmetal, et al^[iii], who found a clinical syndrome that manifested as rest angina associated with ST-segment elevation that promptly responded to sublingual nitrates. Later it was found out that variant angina was attributable to coronary artery spasm, accordingly also called vasospastic angina, but also demonstrated that episodes could be associated with ST-segment depression. If variant angina lasts more than 30 minutes, it can also cause acute myocardial infarction and sudden death.

I.         What are the Pathogenesis (risk factor) of Coronary artery disease?

    The major cause of CAD is coronary artery atherosclerosis, but the causes of atherosclerosis has not entirely clarified yet. Perhaps it’s the combination result of various factors. The risk factors of CAD include:

1.     age and gender (males ≥ 45 years old, female ≥ 55 years old or postmenopausal female have atherosclerosis)

2.     family history (patient’s father or brother died of heart attack before 55 years old, mother or sisters died of heart attack before 65 years old)

3.     dyslipidemia, Low density lipoprotein cholesterol (LDL-C) is too high, high density lipoprotein cholesterol (HDL-C) is too low.

4.     Hypertension

5.     Diabetes mellitus

6.     Smoking

7.     Obesity

8.     Gout.

II.         What are the clinical symptoms of coronary artery disease?

    Symptoms of Angina is caused by myocardial anoxia (lack of oxygen for heart muscle), which including:

1.     Chest discomfort, which be described as a feeling of pressure, heaviness, tightness, squeezing, burning, or pain in the chest. The severe burning pain and general pain last for 1-5 minutes, and sometimes even lasting for 15 minutes. Sometimes it will relieve itself.

2.     The feeling of pain may spread to left shoulder, anteromedial left arm all the way to the little finger and the ring finger.

3.     Pain occurs when heart burden increases (e.g. increasing physical activity, excessive mental stimulation or cold.) and would disappears when resting or after taking sublingual nitroglycerin.

4.     When the pain occurs, symptoms may include prostration, sweating, shortness of breath, anxiety, palpitation, nausea or dizziness.

    Myocardial infarction is the critical symptom of CAD. Commonly combined with frequently angina attack and aggravating angina. There are also cases with sudden myocardial infarction but without any angina history, which is the most dangerous situation causing sudden death. Symptoms of myocardial infarction include:

1.     At the time of sudden attacking, sharp pain occurr in the retrosternal area or precordium (area in the heart position of chest), and then may radiate to the left shoulder, left arm or other regions. Such pain continues and can’t be relieved with resting or sublingual nitroglycerin after more than half an hour.

2.     Short of breath, dizziness, nausea, hyperhidrosis, and weak pulse.

3.     Cold and clammy greyish, white skin.

4.     The only symptoms among 10% patients is syncope or shock.

III.         What are the Classification of coronary artery disease?

1.     Stable angina^[iv] (angina pectoris), which is also known “effort angina”. Patients’ symptoms haven’t dramatically changed for two months. (No obvious change in terms of trigger cause, frequency, duration and severity.)

2.     Unstable angina^[v]: In comparison with stable angina, it is more likely to cause myocardial infarction or sudden death, which is more harmful. Unstable angina can be classified as follows:

                        i.         Progressive angina pectoris (Rest angina):

    It is a more severe form of angina pectoris, which the frequent, onset and duration is more severe and can happens even during resting. What’s more, it cannot easy to be relieved by sublingual nitroglycerin.

                      ii.         New onset angina:

    The onset of angina was first discovered in the past month depending on the degree of exertion, and the symptoms was aggravated gradually. In the original Braunwald classification of unstable angina, new onset was defined as less than two months in duration^[vi].

                     iii.         Variant angina (vasospastic angina):

    It is caused by coronary artery spasm or associated with ST-segment depression, and its onset occurs more frequently during resting.

IV.         What are the clinical diagnosis of coronary artery disease?

    The diagnosis of CAD is mainly based on clinical symptoms.

    When the high-risk group of people (older age, multiple risk factors) have chest pain symptoms qualified as following criteria, should be highly regarded as potential patients of CAD.

                        i.         Chest pain at sternum area.

                      ii.         Chest pain radiate to lower jaw, left arm or left shoulder.

                     iii.         Feeling pressure or burning chest pain.

                     iv.         Chest pain duration is 1 to 5 minutes, no more than 15 minutes.

                       v.         Chest pain is triggered by tiredness, cold or heavy meals.

                     vi.         Chest pain is relieved by resting, having sublingual nitroglycerin after 1 to 3 minutes. 

Table 1.  Probability of angina symptoms relate to diagnosis of CAD

    Table 1 is a probability table, for example the probability of when a 60 years-old male patient having typical angina be confirmed diagnosed as CAD is 94%, as for the same aged woman, the probability is 90%. On the contrary, if a 30 years-old woman having non-angina related chest pain, the probability of confirmed CAD is less than 1%.

1.     ECG (Electrocardiography)

    Most patients with CAD have normal ECG when in normal state, thus, the possibility of CAD can not be excluded in the case of normal ECG.

    Then, what is the ECG feature of angina?  When angina occurs, there will be a temperate reversed T wave or ST segment depression. When the angina attack passes after resting or having sublingual nitroglycerin, the ECG will back to normal. In some rare cases that patients have severe ischemia (more than 15 minutes), the abnormal ECG will last longer to several days.

    On the contrary, some patients have no obvious symptoms, but with long-term abnormal ECG such as reversed T wave or ST segment depression. These patients usually are not CAD patients but may have cardiomyopathy or hypertensive cardiomyopathy. Even some normal health people with abnormal ECG for more than 30 years without any organic disease. 

    Some physicians will diagnose slight abnormal ECG discovered in physical examinations of patients as “myocardial ischemia”. If there is no connection to symptoms such as chest pain or pressure, it usually has no clinical significance. It should not be diagnosed as “myocardial ischemia” easily.

2.     Treadmill Exercise Test (ECG Exercise Test)

    The CAD diagnosis accuracy of this test is about 70%. There are certain contraindications for treadmill exercise test, including acute myocardial infarction (AMI), unstable angina, uncontrolled hypertension, heart failure, or acute cardiopulmonary disease.

3.     Myocardial Perfusion Imaging (MPI) Test

    The CAD diagnosis accuracy is also about 70%, but the accuracy of myocardial infarction diagnosis is nearly 100%.

4.     Coronary Artery Computed Tomographic Angiography (CTA)

    The CAD diagnosis accuracy of this test reaches 90% or above. Early stage atherosclerosis can be diagnosed, which can’t be diagnosed in other examinations.

5.     Dynamic ECG (Holter monitor)

               i.         Non-stopped recording ECG.

             ii.         12-lead holter: Recording painless myocardial ischemia. Compare with when chest pain occurs to see if there is S-T segment depression. So as to identify the type of chest pains.

            iii.         If there is S-T segments elevation with chest pain, it is helpful to diagnosis variant angina (vasospastic angina).

6.     Echocardiography

    A extremely crucial examination for the diagnosis of CAD.

               i.         It can exclude various types of organic heart diseases such as congenital heart disease, rheumatic heart disease or cardiomyopathy.

             ii.         Coronary heart disease angina: The echocardiography for the majority of this type of patients is normal.

            iii.         Acute myocardial infarction or old myocardial infarction (continues > 8 weeks): If there are obvious abnormal wall movements of the right or left ventricle or atria, Echocardiography can help to diagnose these two types of diseases.

V.         How to prevent coronary artery disease (Primary prevention)?

1.     Live a regularly life, don’t stay up late. Avoid reading thriller, horror novel before sleep.

2.     Stay in a good mood. Avoid getting angry, terrified, anxiety, or excessively happy.

3.     Control diet. Keep a light and digestible diet with low oil, fat, and sugar, and with adequate fresh vegetables and fruits. Have more frequently, less quantity meals a day rather than less frequently, more quantity meals a day. Avoid excessive tea or coffee.

4.     Quit smoking and alcohol. Smoking is an important risk factor for myocardial infarction and stroke. A little amount of wine or other alcohol a day is fine, but don’t overdrink alcohols.

5.     Avoid too much sudden physical activity. Do not exercise immediately after meals.

6.     Keep regular exercise based on your health condition and hobbies, such as Tai Chi, table tennis. Avoid too much burden of heart based on personal health condition.

VI.         How to prevent coronary artery disease (Primary prevention)?

    Secondary prevention is defined as patients with confirmed CAD (including those receiving stent intervention and bypass graft surgery) using medication and non-medicine intervention to delay or prevent the progress of arteriosclerosis. It is summarized below:

1.     Angiotensin converting enzyme inhibitor (ACEI) and aspirin.

2.     β-blocker and blood pressure control.

3.     Quit smoking and Lower cholesterol level.

4.     Diet and diabetes control.

5.     Exercise and education.

    The effect of aspirin is anti-platelet aggregation. The morbidity and mortality of cardiovascular disease in patients taking aspirin are significantly lower. The side effect of hematemesis is observed in 1 case per 5000 patients taking aspirin, however, 95 cases of severe cardiovascular events are prevented.

    Aspirin is contraindicated for gout patients, because it inhibit the excretion of uric acid. For gout patients and other patients who can’t tolerate aspirin due to other reasons, Plavix 75 mg qd can be prescribed.

     75 to 150 mg aspirin qd (per day) can be used as a secondary prevention of CAD, and the dose can be increased to 150 to 300 mg qd for acute myocardial infarction, acute ischemic stroke and acute attack of unstable angina.

VII.         Principle of Coronary artery disease treatment

    Treatment for acute angina

    Once angina attack happens, rest and taking sublingual nitroglycerin immediately. Usually, angina can be relieved after one or two minutes. If angina is not relieved after 5 minutes, another tablet of nitroglycerin can be taken. If it is the first time of the angina attack, visit a hospital as soon as possible regardless of relieving or not, because there is a risk of myocardial infarction when angina attack happens at the first time.

    Systemic treatment (long term treatment)

    Drug therapy

1.     Nitrate esters, including nitroglycerin, isosorbide dinitrate, Xinkang (Isosorbide Mononitrate), long-acting Xintongzhi (Isosorbide Mononitrate) or Deruining (Isosorbide Mononitrate).

2.     Statins, for plasma lipoprotein lowering, including Lipitor (Atorvastatin), Zocor (Simvastatin), and lovastatin, which can delay or prevent the progress of atherosclerosis.

3.     Anti-platelet agents, including aspirin 100~300 mg qd. Using Ticlid or Plavix instead when allergic to aspirin.

4.     Β-blockers, including Betaloc (metoprolol), Atenolol, and Concor (bisoprolol).

5.     Calcium channel blockers, which is the first choice for patients with coronary artery spasm, such as Jiubaoping [Nifedipine Extended-release Tablets(III)].

Surgical management

1.     Percutaneous coronary intervention (PCI), stents

    PCI is a cardiac catheter technology, put stents or other devices into patient’s coronary artery through the entry of femoral artery or radial artery to treat coronary stenosis.

    PCI has minimal invasiveness, promising effects, and low risk (< 1%). The rate of restenosis after treatment is 15%-30%, using bare-metal stents. The invention of drug-eluting stents (DES) further reduces the rate of restenosis, which is 3% among normal patients and 10% among patients with other complication such as diabetes mellitus, almost as effective as coronary bypass surgery.

2.     Coronary artery bypass surgery (Coronary artery bypass graft surgery, CABG)

    CABG is a surgery that takes a length of healthy blood vessel from the patients’ other body parts and then attaches it to the two ends of the coronary artery with stenosis or obstruction, allowing blood circulate through the bypass. Providing oxygen to the ischemic cardiac muscle and relieve symptoms of myocardial ischemia.

    Coronary artery bypass is a very invasive surgical procedure, but with very promising treatment outcomes, which is recommended to use in more severe CAD patients with l unprotected left main coronary artery disease, Thromboangiitis obliterans (Buerger disease) and diabetes and multivessel coronary artery disease, who are not suitable for stents.

References:

[i] Faxon DP, Fuster V, Libby P, et al. Atherosclerotic Vascular Disease Conference: Writing Group III: pathophysiology. Circulation 2004; 109:2617.

[ii] Libby P, Ridker PM, Hansson GK. Progress and challenges in translating the biology of atherosclerosis. Nature 2011; 473:317.

[iii] PRINZMETAL M, KENNAMER R, MERLISS R, et al. Angina pectoris. I. A variant form of angina pectoris; preliminary report. Am J Med 1959; 27:375.

[iv]Fihn SD, Gardin JM, Abrams J, et al. 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and management of patients with stable ischemic heart disease: a report of the American College of Cardiology Foundation/American Heart Association task force on practice guidelines, and the American College of Physicians, American Association for Thoracic Surgery, Preventive Cardiovascular Nurses Association, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation 2012; 126:e354.

[v] Patel MR, Chen AY, Peterson ED, et al. Prevalence, predictors, and outcomes of patients with non-ST-segment elevation myocardial infarction and insignificant coronary artery disease: results from the Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the ACC/AHA Guidelines (CRUSADE) initiative. Am Heart J 2006; 152:641.

[vi]Braunwald E. Unstable angina. A classification. Circulation 1989; 80:410.