Heart Calcium Scan
Heart calcium scan also known as Coronary Calcium Scan is what the doctor will use to look for calcium deposits in coronary arteries. Such calcium deposits can narrow arteries and thereby increase heart attack risk. The result of this scan is called Coronary Calcium Score. Heart calcium scans are non-invasive techniques to measure the amount of calcium in the walls of coronary arteries – arteries that supply heart with blood. This is an indication that they may develop coronary artery disease.
Why heart calcium scans?
These scans show a higher risk of having a heart attack or any other problems before any symptoms of heart disease become obvious. However, the American College of Cardiology does not recommend routine heart scans on people who do not exhibit any symptoms of heart disease and who do not smoke or have cardiac risk factors such as elevated cholesterol or high blood pressure.
Heart scans is useful to whom?
In those who are in intermediate heart attack risk category, a heart scan may give information about heart attack risk. Based on risk factors, having a heart attack in the next 10 years falls somewhere between 10 and 20 %. For instance, if the patient is between ages 55 and 65 years and bordering on high cholesterol or blood pressure or a smoker, then a heart scan may be considered. As there is some evidence that people with calcium scores show risk of heart disease, many would be motivated to adopt lifestyle changes, lose weight or quit smoking than those who do not undergo heart scan.
Who do not benefit from heart scans?
If a person is younger than 55 years of age and has normal cholesterol and blood pressure levels, and does not smoke, heart attack percentage is calculated less than 10 % and falls under low-risk category. Probably, in such cases, a heart scan may not reveal anything more than what the doctor already knows.
A 20 % risk or greater risk of having a heart attack in the next 10 years means at high risk. If the person is older than age 65 with high cholesterol levels and high blood pressure and does smoke, then a heart scan will not do much good because the doctor knows the risk based on risk factors and the steps to prevent a heart attack such as taking medications and making significant changes in life style. If the person has already had a heart attack or a surgical procedure, then he is at a high risk of having a heart attack and therefore a heart scan will not provide any more information on how his/her condition should be treated.
Preparing for a heart scan
It is better to visit the doctor prior to the heart scan as this can provide additional information on the heart attack risk for a doctor to consider. The examination will include:
1. A review of the medical history and the patient's family medical history.
2. A physical examination including blood pressure.
3. A risk assessment including questions about exercise and smoking habits.
4. Blood tests including cholesterol levels.
5. The doctor has to be told if a woman is pregnant. This test is not done on pregnant woman.
Other than these, there are no special preparations to have before the heart scan.
The procedure and after
A coronary calcium scan is usually done by a radiology technologist. The pictures are interpreted by a radiologist. A team of family medical practitioner, internist, cardiologist or surgeon may also review this test. Heart calcium scans takes only a few seconds and during this procedure the patient is asked to hold their breath to obtain an accurate image. The scan shows the calcium in the heart arteries by using computerized tomography (CT).
Calcium deposits show up as bright white spots on the scan. The standard imaging technique for coronary arteries uses multi slice or helical CT. In addition to calcium, such scans also reveal the presence of any narrowing of heart arteries due to coronary artery disease. After the procedure there are no special precautions and the patient should be able to drive home and continue daily activities.
If calcium score is high, it means more aggressive treatment of heart attack risk factors should be done such as life style changes or medications. The doctor may recommend more invasive tests such as coronary Angiography based on scan results. Sometimes the result of the test may not be helpful if the patient has a fast heart rate or smokes.
Heart scans such as multi slice computerized tomography and helical CT are used to see calcium in arteries. Such type of scans expose the patient to radiation. There is a slight chance of developing cancer from having coronary calcium scan. The chance is higher in those who have had many radiation. It is imperative to consult with the doctor about the amount of radiation required for this test and confirm that the test is needed. Sometimes an allergic reaction to the medication that is used during the procedure is exhibited.
The results of such scans should never be interpreted alone but should be used with information about other overall heart health and any risk factors the patient may have such as family history and high cholesterol. It is possible to have false positive results. This means that the test shows a high chance of plaque in the arteries when it is not true. Those with low chance of heart disease are most likely to have a false-positive test.
Calcium Channel Blockers
Calcium channel blockers are one of the key drugs administered in cardiovascular conditions. In most cases they are used in case of hypertension and angina.They are classified depending upon their mode of action and their chemical composition. These chemicals when induced in the body block the calcium channels in the cell membrane.
They are selected for vascular sites rather than the myocardial region. These drugs facilitate good vasodilator effects with limited electro physiological effect on the cardiac conduction system pertaining to the AV and SA nodes. Thus the negative inotropic effects do not occur in these drugs.These drugs are more selective to the cerebral arteries than the systemic arteries. Eg: Nifedepine, Amlodipine, nimodipine.
These drugs cause peripheral vasodilation with a moderate inotropic effect. Subsequently they increase the coronary vasodilation. Cardiac rate may or may not increase as it causes a slight depression in the SA or AV nodal conduction route. Eg: Verapamil.
These drugs are also associated with peripheral vasodilation causing mild inotropic effect and minimum depression in the SA / AV node conduction. They increase coronary vasodilation. They also exhibit intermediate vaso-selectivity. Eg: Diltiazem.
The elimination route for most of these drugs is through the liver. In most cases the recommended dosage is twice a day for sustained release in the body. The limitation of calcium channel blockers administration for hypertension is often related to their functionality such as vasodilation. However, because of their mechanism of action and efficacy, they do not cause conditions such as reflex tachycardia.
Calcium channel blockers are given to children who have low renin levels. The drug is given with other drugs such as beta-blockers and diuretics to attain desired results of cardiac physiology. In most cases, calcium blocker administration requires investigative tests such as blood vessel abnormalities, liver and kidney function tests.
Side effects and precautions
Calcium channel blockers are known to have some side effects since they are closely associated with vascular physiology and cardiac conduction system. Syncope and presyncope episodes followed by dizziness are commonly-noticed side effects. This happens because of the decrease in blood pressure due to reduced heart rate. Arrhythmia is another potential side effect along with gastro-esophageal reflux and nausea.
Lower extremity swelling or edema is a complication of treatment with calcium channel blockers (especially with Felodipine and Amlodipine), Thioglitazones and Minoxidil. Transient Incontinence is another symptom noticed with Calcium Channel Blocker drugs.
The most common side effects of calcium channel blockers are peripheral edema, Bradycardia, headache and constipation in some cases. The dihydropyridine agents such as Nifedipine, Nicardipine, Isradipine, Felodipine, Nisoldipine and Amlodipine, can produce symptoms of vasodilation - specifically headaches, palpitations, flushing and peripheral edema or swelling in lower extremities.
Some studies indicate that juices such as grapefruit should be avoided during the administration of calcium channel blockers as they hinder with the drug absorption and breakdown in the system. Alcohol consumption must also be avoided as it may cause damage because of hepatic involvement in the respective drug.
Calcium channel blockers are taken as second line cardiac drugs with respect to anti-hypertensive drugs and beta-blockers. However careful examination of the patient drug history is performed before recommending these drugs because some studies also imply that prolonged usage of all three drugs may increase the incidence of diabetes and the risks associated with it. Drug evaluation is essential because recent studies indicate the involvement of clarithromycin along with calcium channel blockers causing kidney damage and prolonged usage of these drugs can also cause breast cancer in women.
Cardiac Calcium Score Test
Cardiac calcium score also known as coronary artery calcium score is a unique diagnostic test to detect the incidence of coronary artery disease at an early stage. It also helps determine advanced stages of heart disease. This diagnostic test is recommended to determine the presence of calcium in the coronary artery. Coronary calcium score helps in prophylactic strategies such as administration of anti platelet therapy and cholesterol control methods respectively. Plaque is formed because of the deposition of fat in the coronary arteries. This plaque eventually get calcified leading to a condition called atherosclerosis.
Cardiac calcium score determination is based on comparison of profiles belonging to the same sex, age group and risk factor and history pertaining to coronary heart disease. The comparative parameters of the cardiac calcium scores are used to analyze the effects of the disease in relation to age and other risk factors.
Preparation for the cardiac calcium score test (CAC)
Cardiac calcium score is done by administering computer tomography technique. The procedure is non-invasive and detects the presence, location and level of calcium deposits in the coronary arteries. The patient is advised to reduce caffeine intake at least a few days prior to the test. Pregnant women are not advised to undergo this procedure.
The scores obtained are graded from 0 - 400. The patients having a CAC score of 1- 100 have mild evidence of coronary artery disease. Patients having a score of more than 100 are at moderate risk of cardiac disease and the patients having a score over 400 are at a greater risk of cardiac disease.
Bibliography / Reference
Collection of Pages - Last revised Date: December 12, 2017