Acute coronary syndrome (ACS) is a term used to denote any condition that occurs as a result of reduced blood supply to the heart muscle. The disorders range from a threatened heart attack, also known as unstable angina, to an actual heart attack, called myocardial infarction.
The blood vessels that carry blood away from the heart are known as arteries. The heart supplies oxygen-rich blood to the various parts of the body through an artery called aorta. The coronary arteries that branch off from the aorta in turn carry blood to the heart muscle. Any factor that reduces the blood flow to the heart muscle, either due to blood vessel narrowing or blockage, can lead to ACS. One of the most common causes of blood vessel narrowing is atheroma formation. Atheroma refers to deposits called plaques that develop in the wall of the arteries overtime. The plaques comprise an outer hard shell with an inner fatty core. These can impede the blood flow to the heart by narrowing the arterial lumen, that is, the cavity of the arteries. Apart from atheroma, inflammation of the coronary arteries, stab wound to the heart, cocaine abuse, migrating blood clot and surgical complications are a few other conditions causing vessel blockage. Figure 1 illustrates the chambers and different arteries supplying blood to the heart.
Chest pain that occurs as a consequence of reduced blood supply to the heart is termed as angina. Unstable angina occurs as a result of lack of blood flow to the heart muscles. However, the heart muscle is not damaged. Unlike pain with stable angina, which gets better with rest, the symptoms of unstable angina typically occur at rest. The pain persists despite taking medications. Unstable angina is thus equivalent to a threatened heart attack and must be attended to immediately.
A myocardial infarction (MI) is what is commonly known as a heart attack. This occurs as a result of clot formation subsequent to a plaque rupture. The clot can completely block the artery and cut off the blood supply to a portion of the heart muscle. Thus, if not treated at the earliest, it can lead to damage and death of the respective heart muscle. Occasionally, spasm of coronary arteries can also lead to a heart attack.
The American Heart Association recommends the following while performing a CPR:
If you are not trained in CPR, then provide about 100 chest compressions per minute until the arrival of paramedics
Another form of resuscitation that is gaining popularity is cardiocerebral resuscitation, in which recommends on continuous chest compressions without mouth-to-mouth breathing.
Risk factors of a heart attack are similar to that of any other heart disease. These are classified into modifiable and non-modifiable risk factors. Modifiable risk factors include:
Non-modifiable risk factors include:
It is important to differentiate the pain caused by ACS from the pain due to other causes. Various tests that help in appropriate diagnosis have been discussed below:
ECG is usually the first investigation performed if a heart disease is suspected. Electrodes attached to the body transmit electrical impulses, which get recorded as waves on the ECG paper. A dead heart tissue lacks electrical activity and hence an ECG can depict signs of current or previous heart attack.
An injury to the heart tissue can lead to leakage of certain enzymes of the heart, which can be detected in the blood. Hence, a blood sample is usually collected for testing the enzymes. A positive test warrants hospitalisation.
An echocardiogram is a procedure that principally uses sound waves to create a moving image of the heart. Sound waves are transmitted to the heart by a device called transducer. These waves are reflected back as electrical impulses, which eventually get converted into heart images. An echocardiogram can detect areas of damaged heart tissue.
Chest x-ray aids in determining the size and shape of the heart and the arteries.
Nuclear scans are performed using radioactive materials. These radioactive materials are injected into the blood stream and traced using special cameras as they flow to organs such as the heart and lungs. Areas with impeded or reduced flow appear as dark spots.
A CT angiogram helps in detecting any narrowing or blockage of the coronary arteries. A radioactive dye is injected and multiple images of the arteries are taken with the help of a CT scanner, which are then sent to the doctor for review.
It is an invasive procedure that can help in the diagnosis as well as treatment of an arterial block. Coronary arteries are accessed via the blood vessels (veins) in the legs, with the help of a long thin catheter. A liquid dye is injected into the coronary arteries, which then appear on the x-rays and detects any blockage. The same catheter can be used to widen the blocked area with the help of small balloons; this procedure is termed angioplasty.