Hippocrates

Table of Contents

Preface

Welcome to Partow Nuclear Medicine Center. We thank you for choosing our center for your heart scan. All the personnel in this center will try hard and do their best to please you and your physician . We find it our duty to explain in a simple way how the heart scan is accomplished , and the steps patients should go through for doing it. In our instruction we have endeavored to clarify the ambiguous and worrying situations that usually occupy the patient's minds. Due consideration has also been given to their erratic questions concerning the produres. We ask you earnestly to read the instructions carefully in order to take better advantage of the available facilities and obtain accurate and reliable result.
First we will have a brief review of the normal heart structure and function, coronary artery disease and its clinical symptoms. Then, procedures for heart scan and its associated exercise test will be mentioned.

Normal Heart

The heart is a hallow muscular organ which receives the blood from the veins and propels it into the arteries. It is divided by a musculomembranous septum into two halves, right or venous and left or arterial, each of which consists of a receiving chamber (atrium) and ejecting chamber (ventricle). The heart predominantly functions as a pump. Volume of blood ejected by each ventricular contraction (Systole) normally range from 80 to 100 ml. During systole, various walls of the left ventricle move inward, and the ventricle normally shortens at least 20% along its long axis and 40% along the short axis. The heart muscle (Myocardium) is supplied by the right and left coronary arteries. The normal coronary blood flow is approximately 224 ml/min. With exercise, however both the coronary flow and cardiac output may increase 4-6 folds.

Major Risk Factors of Heart Disease

Many factors contribute to the development of coronary artery atherosclerosis (Atheroselerosis is a vascular disorder with fatty degeneration, hardening and narrowing of the arteries). Some of these risk factors are as below:

* Male sex (Women manifest cardiac symptoms about 10 years 
   later than men)
* Arterial hypertension
* Elevated cholesterol and triglyceride in the blood stream 
* Elevated sugar in the blood stream (Diabetes Mellitus) 
* Cigarette smoking
* Family history of coronary artery disease below age 55 
   Obesity
* Inactive lifestyle

Coronary Artery Disease

Today coronary artery disease is the most widespread cause of death throughout the world. Diminished supply of blood flow in the coronary circulation of the heart, reffered as Ischemic Heart Disease, is a predisposing factor for the heart attack and myocardial infarction. About one third of all heart attack victims are not aware of their disease. Ischemic heart disease can be detected in their earliest phase by Myocardial Perfusion Scan (Cardiac Scan), wich is a new, non-invasive and accurate method. Chest pain (Known as Angina Pectoris) is the visceral chest discomfort that results from transient myocardial ischemia. It is often described as a substernal discomfort or pain, perceived as a pressure, tightness or fullness sensation. It may radiate to the neck, jaw, shoulder or arm (often left arm). It is likely to occure when the coronary blood flow is less than is required, so usually induced by exercise or emotional stress and relievd by rest or with use of Nitroglycerin tablet, lasting only a few minutes. Typical angina comes on over a few seconds or minutes, lasts 5 to 15 minutes and resolves with rest or sublingual Nitroglycerin. Common precipitating factors include hurrying, climbing stairs, early morning, cold airs, sexual intercourse or after meals.

Dr. canon, professor of Harvard Medicine University states:

" Most people suppose that their hearts are working consistently but they should know that after every contraction beat, there is a definite rest for the heart. When your heart beats 70 times per minute, that is , it has just worked 9 hours from 24 hours and has rested the remaining 15 hours! Therefore, you should try to rest like your heart before feeling tired".

Myocardial Perfusion Scan(Heart Scan)

When the narrowing of a coronary is less than 50 percent of the diameter of the vessel, the effect on blood flow is general clinically insignificant. As narrowing approaches 70 percent the lesions become much more significant, particularly during exercise. So myocardial perfusion scan should be done with exercise. So myocardial perfusion scan should be done with exercise test simultaneously, which lasts about half an hour. The test is performed by bicycle or treadmill.

Patient preparation Process

The first step of your cardioscan will be accomplished with Exercise Test at the same time, as follows:

1- The patient is guided to the Injection Room.
2- An appropriate angiocathere will be attached to front side of patient's elbow (left side). This attachment is for next injection done quickly during exercise test.
3- Ten special chest leads are used to attach the wire of exercise test apparatus to different areas of your chest, around your heart. To be ensure of correct attachment and no interference and disorder in patient's electrocardiogram (ECG), removing the chest hair is necessary (for men).
4- He/She will be guided to Exercise Test Room and a cardiologist will ask about his/her heart disease background and will examine the patient. At first step, pulse, blood pressure and electrocardiogram will be measured and registered and then , they will be checked repeatedly in the next stages.
After then, the patient will stand on the treadmill for the exercise test. Treadmill of this center is a mobile and rolling elastic belt (like conveyor belt). The patient stands on it and has to walk in order to keep his/her balance. Speed and slope of the belt will increase every three minutes by some percent.

In order to have a perfect exercise, the patient should wear comfortable clothes and shoes and not have severe physical activities before exercise test. It is recommended to be empty-stomached and not smoke at least 3 hours before exercise. If the patient suffers from diabetes, he/she should be empty-stomached (after a light food) for one hour before the exercise. He/she needn't change the dose of insulin. The patient should stop the heart interferring drugs (like Propranolol) which decrease the patient's heart activity during exercise, at definite intervals before exercise and under physician prescription. (All of such drugs have been introduced in a list and presented to patients). According to patient's age, a definite limitation of exercise and maximum heart rate will be determined and the test will continue up that rate. The best and most reliable result depends on achieving the maximum predicted activity without appearing any abnormal change in patient's clinical condition or electrocardiogram (ECG).
Although the result needs to nearly 10-12 minutes exercise, whenever the patient feels who is not able to continue exercise or gets involved in some clinical symptoms like: pain in the chest, severe breathing problem, vertigo or headache, and if he/she is inclined not to continue the exercise, it will be stopped immediately with patient's request. While reaching the maximum amount of pre-determined heart rate, that is, in the last minute of exercise, the radioactive drug will be injected to patient's hand through angiocatheter.

Two Important Points:

1) Exercise Test: No need to worry about

It is emphasized that all above procedures will be accomplished under controlled conditions and by a cardiologist with a trained nuclear medicine technologist assistance and with sufficient drugs and equipment. The patient's electrocardiogram, pulse and blood pressure will be controlled and registered continuously by exercise test set. We ensure you, as soon as an abnormal change in heart beat appears and before any clinical symptoms, the test will be stopped with physician prescription or the signals received by set. In general when the patient is not able to exercise or doing exercise is harmful for him/her, injection of some special medicines is prescribed instead of exercise test.
The most famous of such medicines is Dipyridamole (Persantine), which causes to expand the coronary arteries and increases heart blood flow in several folds. By injecting of this medicine the similar physiological effects of exercise will produse in the heart, without doing and serious physical activity. As long as your heart wont return to its normal situation, you will be under control and observation of our cardiologist.

2) Radioactive Drug Injection :

No danger will threaten you
The injected radioactive drug through angiocatheter at the end of exercise test (while you are running) is a safe and harmless radioactive material. This material is normally Technetium-99m(99m Tc-MIBI),(201 TI) and sometimes, some other drugs, derivative of Tc-99m. The extrafear of radiation which is observed in some patients is not scientific. The bit radioactive material used in this step consists of very low energy gamma emitters (not containing of Alfa and Beta emissions) and also it is very weak and has short life (about few hours). The vast studies show that this material which enters the body as a safe labeling or searching agent will not have any harmful radiation or chemical hazard.
It is interesting to know that radioactive emissions normally exist in our surrounding and some scientists consider them efficient and positive. Special safety instructions (from view point of not associating with others up to 12 hours after injection) in this field, are just precautionary and used mostly about pregnant women.

Heart Imaging

It is not possible to scan the heart immediately after the exercise, because the increase in the heart activity and respiration caused by the exercise test or the injection of Dipyridamole will impair the quality of the photons taken at this time. Moreover the injected radioactive drug administered at the last moment of the exercise test for the clarity of the heart image and cleansing of the background tissue will have enough time to effect. So a delay of one or sometimes two hours before the scan is unavoidable.

Before entering the waiting room you will be served with a glass of milk. Drinking the milk, besides satisfying your hunger and restoring your energy, will cause the extraradiation to leave the liver and gall bladder and to have a clearer image of the heart.
Drinking some glasses of water and walking in the waiting room will also have an additional effect (especially for patients who have received Dipyridamole injection).
Patients who can't drink milk are advised to bring some cream or high fat yogurt with them (provided their blood triglyceride or cholesterol is not high). After the due time you will be called to the scan room, thereat, the nuclear medicine technologist will help you to lie on the bed, usually on your back, and fold your hands above your head. This will help the detecting equipment (Gamma Camera) to get as close to your heart as possible. (Gamma Camera is a medical imaging device which convert photons emitted by the drug in the patient's body into the light and thereafter into the electricity and subsequently produces an image of the organ in the body). So in this field the patient is radiant and not the imaging device. The gamma camera in this center is equipped with the advanced computed Tomography (SPECT) system. The patient's bed in this system which has a gutter shape has been designed in a way that keeps the patient stable and motionless position. In this step which lasts about twenty minutes, the body must be completely motionless. So moving, shaking the hands, coughing and even deep breathing can all impair the final cardiac images because they can cause the heart to move inside the chest and result in faulty giagnosis.

While taking images,the detector moves around a 180 degree orbit and takes a 35 second image at each 5 degree interval. On the whole, 32 images of the heart will be taken from different angles. The set will periodically stop imaging during its short time movements around the patient's chest, so slight movement of the patient in these 2-3 second intervals is permitted.
When taking images end ,the first step of your test has finished, and you are required to stay and rest until a definite time to get ready for the next step of the scan. For accurate examination of the heart condition, scanning must be accomplished in two separate phases (exercising and resting) to determine the possibility of the reversible decreased cardiac blood flow (Myocardial Ischemia) or cardiac infarction. Therefore heart scan must be performed in two separate phases and two different ways. It's worth while to mention that using of interferring heart drugs should be suspended only before the exercise phase, but not before the rest; so after the exercise test, the patient can start taking the heart drugs again under the supervision of the concerned physician . In case of constipation, you are required to inform the concerned technologist to give you some laxatives, because emptying the bowels before the scan can improve the quality of the scan.

Second Phase of the Heart Scan

For the second phase of the scan (resting phase) the patient should eat a light meal three hours before the test. (sugar, milk, butter, and other fatty foods should not be consumed) and do not eat anymore before the test begins. For those who suffer from Diabetes Mellitus a fast of one hour is enough. The rest phase which usually occurs one day after previous phase, is shorter and simpler than the first phase and is not accompanied by exercise.
First the radioactive drug is intravenously injected and after a delay of an hour and sometimes up to 2 hours (which is necessary for the clearance of the liver and gall bladder from the administered drug) heart scanning will repeat again like the previous one.

Heart Scan Report

Considering the above instructions, the scan file which will finally be given to you will consist of two independents:

1- The report about the exercise test, which is analyzed by the cardiologist and shows the heart condition and related vessels at different steps of the test, and each page indicates one of the test steps.
2- Myocardial perfusion scan report has been prepared by the nuclear medicine technologists and physicians and contains three sheets, one sheet is the scan report which contains the related changes and the diagnosis of disease typed on it by nuclear medicine physicians, and the other two sheets have the colour images of the heart. On the main sheet, different images (tomograms) of heart in the form of 3 two-rows image series (six rows on the whole) can be observed. These small images are the computerized result of previous 64 images of the heart which were taken from different angles at two 20-minute imaging stages.
This advanced technique which is called SPECT or Computerized Tomography is the renovation of a three-dimensional image, from a large number of two-dimenional ones. At the end of the scan operation and leaving of the patient, the nuclear medicine technologist spends to lot of time on the computer to renovate 3 dimensional images and to determine different dimensions and show blood flow of the heart muscle in two phases of exercise and resting. In related views of "Short Axis the", the heart horizontal cuts from top to bottom will be shown as circular pictures of the left ventricle. The circles related to upper part of the heart are shown bigger and circles of lower part will be smaller . In "Long Axis" views the heart long axis cuttings are checked from top to bottom, horizontally once (Horizontal Long Axis) and also from left to right side of this organ (Vertical Long Axis) will be analyzed vertically again. (The heart long axis images are seen as a horse shoe). The thickness of each heart cutting is about few millimeters.
Therefore, if the smallest and the most obscured angles of heart muscle involved with Ischemia (deficiency in blood flow), will be shown as "defect" in different views of scan. (The spectrum and color sequence used , are shown from minimum to maximum beside each view). Finally, in second sheet of the cardiac scan, the total of acquired images has been demonstrated in two circular (polar) maps (one for exercise phase and another for resting phase) and in two forms (one as spectrum and another as number).
The scan findings in this sheet have been determined quantitatively and completely by the apparatus. The percentage of blood flow in each part of heart muscle has been registered and calculated separately. This polar map is so-called Bull's Eye. If the result of your scan is abnormal, your physician will follow the subsequent treatment through Angiography or by other means.

Summary

Heart scan is one of the most accurate tests of heart accomplished through two phases: exercise and rest, in which quantity and quality of blood flow to coronary artries are controlled in different angles and surfaces. In this kind of imaging those weak areas in sending blood (vulnerable to heart attack) would be identified and the conditions for prevention of heart attack and timely remedy would become possible. 
Another advantage of heart scan particularly for old people or the patients with heart attack background , is to identify the remaining amount of living and intact tissues in heart muscle.
All the personnel of Partow Nuclear Medicine Center wish you health and recovery.

Bibliography

1- Alice Feinstein, symptoms- Their Causes & Cures, Rodale Press 1999
2- Ansari Mojtaba , MD., Nuclear Medicine & Heart Infarction, Medical Journal of Dard, 1:43-44. 2000
3- Fred A. Mettler, MD., Milton J.Guiberteau, MD., Essential of Nuclear Medicine Imaging , Saunders, 1999
4- William F. Ganong, Review of Medical Physiology, Lange, 1999
5- Williams & Warwick , Gray's anatomy, Churchill Livingston, 1999