Diagnosing a heart attack early is important because with each passing minute, more heart tissue is damaged and the prognosis worsens. The doctor is strongly aware of this and has to act quickly to confirm the heart attack as early as possible and start treatment. Starting treatment late can result in complications that have high mortality.
Heart attacks in women are less obvious and more likely to be missed. Women also suffer milder attacks, which may be missed on the ECG or any other standardized tests.
Though the tests to diagnose a heart attack are the same for men and women, a blood test to detect a protein called cardiac troponin is very sensitive and specific. It helps to diagnose a heart attack in men and women, which has been missed on other tests.
However, not all patients with heart attack experience classic symptoms, which at times may be vague.
Sometimes, there may no chest pain or any other symptoms. This is called a silent heart attack. At such times, symptoms do not help much to detect a heart attack. A family history of a heart attack can make the doctor strongly suspicious.
Similarly, the presence of risk factors such as smoking, high blood pressure, diabetes, high cholesterol levels in the blood, obesity, and a sedentary lifestyle, will make your doctor want to investigate you for a heart attack.
He will, then, not lose any time with the investigations and tests to confirm the diagnosis of your heart attack.
Tests described below will help your doctor to confirm the diagnosis of a heart attack even in the case of a silent heart attack.
Tests to diagnose a heart attack
If your heart attack is suspected, you will be admitted to the hospital immediately, usually to an intensive cardiac care unit (ICCU), or directly to the cardiac catheterization lab, to confirm the diagnosis and initiate treatment.
An ECG also referred to as an EKG, is the first thing the doctor takes of the patient suspected of having a heart attack, for the simple reason that it is painless and available next to his table and takes only a couple of minutes to perform and it can immediately diagnose a heart attack most of the times.
Results are available immediately. Portable ECG machines are also available, which the doctor can carry on a visit to the patient’s residence.
Electrodes are attached to the skin of your chest, arms, and legs, and the electrical impulses of the heart are recorded, which are displayed on the monitor screen or on paper.
As ECG records the electrical activity of the heart. It shows the rate at which the heart is beating and its rhythm, whether it is regular or irregular. It also records the force and the timing of the electric impulse as it travels through each part of the heart.
Since heart muscle damaged by a heart attack does not conduct the electric impulses in a normal fashion, it shows on the printed result paper of the ECG.
Besides showing the damage caused by a heart attack, it also shows whether there are any signs of a previously missed heart attack.
However, in 20 percent of the cases, the ECG fails to detect a heart attack even though it is present.
A chest x-ray helps to see the size of the heart, whether it is normal or enlarged. It also helps to visualize the main arteries, which emerge or enter the heart.
It will help to detect the presence of any fluid in the lungs (pulmonary edema), which can be caused by coronary artery disease, heart failure, and other heart conditions.
Laboratory blood tests for enzymes
Other lab blood tests to diagnose a heart attack are done based on the fact that damage to the heart muscle due to a heart attack causes the release of certain enzymes or proteins into the blood from the heart muscle.
Blood tests that detect the presence of elevated levels of these proteins in the blood will indicate heart muscle damage. The specific proteins that are tested for include:
- Creatine kinase (CK)
- Creatine kinase-MB (CKMB)
- Cardiac troponin I or cardiac troponin T
However, some of these proteins namely CK, CKMB, and myoglobin are also found in other skeletal muscles. They are, therefore, not specific to the heart and their levels can be elevated when these other muscles are also damaged.
A new test to detect the protein cardiac troponin is more sensitive and specific to heart muscle damage since cardiac troponins are found only in the heart and not in any other muscles.
However, there is a time lag between the onset of heart muscle damage and the presence of cardiac troponins in the blood. Current guidelines recommend that the blood be tested several times for these proteins over 8 to 12 hours after the patient has been admitted to the hospital.
The absence of the above-mentioned proteins in the blood does not indicate an absence of heart disease but only an absence of heart damage. Further testing is necessary in such cases.
An echocardiogram obtained by a procedure called echocardiography or diagnostic cardiac ultrasound is a harmless test in which sound waves directed at the heart bounce off and are recorded electronically to provide detailed video images of the heart.
The sound waves are directed to the heart by a transducer, which is placed over the chest and captures the bounced sound waves.
An echocardiogram provides details of the damage suffered by the various parts of the heart including the heart’s chambers, valves, walls, and blood vessels (aorta, arteries, and veins).
It can be done during and after the heart attack to determine the damage to the heart and gauge its function of pumping blood.
Exercise stress test
An exercise stress test sometimes called a treadmill test (TMT) or just an exercise test gauges how well your heart functions during physical stress or exertion. You are made to walk on a treadmill or pedal on a stationary bike, which is connected to an ECG machine.
It is done if your ECG is normal and in the presence of a medical professional. It is not done if your ECG has confirmed a heart attack and if your symptoms are suggestive of a heart attack.
During increasing stress, your heart and the body require more oxygen and, therefore, your heart has to work harder to pump out more blood.
This test monitors the heart rate, respiratory rate, and blood pressure during different levels of physical stress.
The test helps the doctor know if the blood supply to the heart during stress is normal or reduced. It also helps to know the stress threshold of the patient – in other words, the level of exercise appropriate for the patient.
Angiogram or coronary catheterization
This imaging test helps to visualize the coronary arteries directly on x-ray and helps the doctor to know the presence and the amount of blockage in the arteries.
Procedure: A catheter, which is a long thin tube is inserted into an artery, either in your groin or the leg. It is then guided under vision on an x-ray on a video screen. This is called fluoroscopy and it helps to see the catheter as it is guided through the arteries to the desired coronary artery of the heart.
Once the catheter is in the desired position, the physician inserts a contrast dye, which is visible on the x-ray. As the dye flows through the coronary artery, images are taken, which help to see the blockage in the artery, if any.
The dye is later eliminated by the body through your urine.
Cardiac computerized tomography (Cardiac CT) or magnetic resonance imaging (Cardiac MRI)
These tests, a cardiac CT scan or a cardiac MRI helps to diagnose heart problems and also evaluate the extent of damage to the heart wall due to a heart attack. Both are non-invasive outpatient procedures.
These tests also show the inside of the heart to help fully evaluate the cardiac muscle, pulmonary veins, coronary arteries, thoracic and abdominal aorta, and a lot more.