Ischemic heart disease
ISCHEMIC HEART DISEASE
ISCHEMIC HEART DISEASE DEFINITION
Ischaemic (or ischemic) heart disease is a disease characterized by reduced blood supply to the heart.
It is the most common cause of death in most western countries.
Ischaemia means a “reduced blood supply”.
The coronary arteries supply blood to the heart muscle and no alternative blood supply exists, so a blockage in the coronary arteries reduces the supply of blood to heart muscle.
ISCHEMIC HEART DISEASE CAUSES
- The major risk factors are smoking, diabetes mellitus and cholesterol levels.
- Those with Hypercholesterolemia have a much higher tendency to develop the disease.
- Hypertension is also a risk factor in the development of Ischemic Heart Disease
- Genetic and hereditary factors may also be responsible for the disease.
- Stress is also thought to be a risk factor.
ISCHEMIC HEART DISEASE PATHOPHYSIOLOGY
Early changes in infarction (minutes to days)
- Drop in tissue oxygen levels
- Rapid conversion from aerobic to anaerobic metabolism
o Impaired glycolysis and ATP production → impaired contractile protein function
o Systolic dysfunction – loss of synchroneous myocyte contraction → compromised cardiac output
o Diastolic dysfunction – reduced ventricular compliance (i.e. impaired relaxation) and elevation of ventricular filling pressures
- Accumulation of lactic acid and reduction in pH
- Impairment of transmembrane Na-K-ATPase due to impaired ATP production
o Increased intracellular Na → intracellular edema
o Increased extracellular K → alteration in transmembrane potential → electrical instability and susceptibility to arrhythmias
o Increased intracellular Ca → activation of degradative lipases and proteases → tissue necrosis
- Acute inflammatory response with infiltration of neutrophils leading to further tissue damage
Late changes in infarction (days to weeks)
- Resorption of irreversibly injured/dead myocytes by macrophages
o Structural weakness of ventricular wall and susceptibility to myocardial wall rupture
- Fibrous tissue deposition and scarring
- Ventricular remodeling
o Infarct expansion – thinning and dilatation of necrotic tissue without additional necrosis
Increased ventricular wall stress
Further impairment in systolic contractile function
Increased likelihood of aneurysm formation
o Remodeling of non-infarcted ventricle
Dilatation of overworked non-infarcted segments subjected to increased wall stress
Enlargement initially compensatory to increase cardiac output via Frank-Starling mechanism, but can eventually predispose to ventricular arrhythmias and lead to heart failure
ISCHEMIC HEART DISEASE SYMPTOMS
Patients with this condition often have had symptoms of angina or a heart attack. Sometimes, patients do not notice any symptoms.
Symptoms of heart failure usually develop slowly over time. Common symptoms include:
- Fatigue, weakness, faintness
- Irregular or fast pulse, or a sensation of feeling the heart beat (palpitations)
- Loss of appetite
- Shortness of breath, especially with activity
- Shortness of breath that occurs after lying down
- Swelling of feet and ankles (in adults)
- Swelling of the abdomen (in adults)
- Waking up from sleep after a couple of hours due to shortness of breath
ISCHEMIC HEART DISEASE DIAGNOSIS
An EKG is a simple, painless test that detects and records the heart’s electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through the heart.
An EKG can show signs of heart damage due to CHD and signs of a previous or current heart attack.
During stress testing, you exercise to make your heart work hard and beat fast while heart tests are done. If you can’t exercise, you may be given medicine to raise your heart rate.
When your heart is working hard and beating fast, it needs more blood and oxygen. Plaque-narrowed arteries can’t supply enough oxygen-rich blood to meet your heart’s needs.
A stress test can show possible signs and symptoms of CHD, such as:
- Abnormal changes in your heart rate or blood pressure
- Shortness of breath or chest pain
- Abnormal changes in your heart rhythm or your heart’s electrical activity
If you can’t exercise for as long as what is considered normal for someone your age, your heart may not be getting enough oxygen-rich blood. However, other factors also can prevent you from exercising long enough (for example, lung diseases, anemia, or poor general fitness).
As part of some stress tests, pictures are taken of your heart while you exercise and while you rest. These imaging stress tests can show how well blood is flowing in your heart and how well your heart pumps blood when it beats.
Echocardiography (echo) uses sound waves to create a moving picture of your heart. The picture shows the size and shape of your heart and how well your heart chambers and valves are working.
Echo also can show areas of poor blood flow to the heart, areas of heart muscle that aren’t contracting normally, and previous injury to the heart muscle caused by poor blood flow.
Chest X Ray
A chest x ray takes pictures of the organs and structures inside your chest, such as your heart, lungs, and blood vessels.
A chest x ray can reveal signs of heart failure, as well as lung disorders and other causes of symptoms not related to CHD.
Blood tests check the levels of certain fats, cholesterol, sugar, and proteins in your blood. Abnormal levels might be a sign that you’re at risk for CHD.
Coronary Angiography and Cardiac Catheterization
Your doctor may recommend coronary angiography (an-jee-OG-rah-fee) if other tests or factors show that you’re likely to have CHD. This test uses dye and special x rays to show the insides of your coronary arteries.
To get the dye into your coronary arteries, your doctor will use a procedure called cardiac catheterization (KATH-eh-ter-ih-ZA-shun).
A thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck. The tube is threaded into your coronary arteries, and the dye is released into your bloodstream.
Special x rays are taken while the dye is flowing through your coronary arteries. The dye lets your doctor study the flow of blood through your heart and blood vessels.
Cardiac catheterization usually is done in a hospital. You’re awake during the procedure. It usually causes little or no pain, although you may feel some soreness in the blood vessel where your doctor inserts the catheter.
ISCHEMIC HEART DISEASE TREATMENT
Treatment for ischemic heart disease begins with seeking medical care from your health care provider. To determine if you have ischemic heart disease, your health care provider will ask you to undergo several diagnostic tests.
Medications used to treat ischemic heart disease
Drug therapy is commonly used for treatment of ischemic heart disease and includes:
- Angiotensin-converting enzyme (ACE) inhibitors, which relax the blood vessels and lower blood pressure
- Angiotensin receptor blockers (ARBs), which lower blood pressure
- Anti-ischemic agents such as ranolazine (Ranexa)
- Antiplatelet drugs, which prevent the formation of blood clots
- Beta-blockers, which lower the heart rate
- Calcium channel blockers, which reduce workload on the heart muscle
- Nitrates, which dilate the blood vessels
- Statins, which lower cholesterol
Many different medicines are available to treat ischemic heart disease. Your health care provider will work with you to select the appropriate medications, depending on your individual condition. It is important to follow your treatment plan for ischemic heart disease precisely and to take all of the medications as instructed.
Surgical procedures used to treat ischemic heart disease
Severe symptoms that are not relieved by medication alone are treated with surgical procedures including:
- Angioplasty and stent placement (procedure to remove plaque and restore blood flow in clogged arteries)
- Coronary artery bypass graft (procedure that helps restore blood flow to the heart by routing the flow through transplanted arteries)