Cardiac CT Basics - ECG - Being Prepared for CT Cardiac Scanning

Do you know that apart from dose modulation, the ECG signal is the most important factor to consider in a cardiac CT angio when applying the right dose to a patient, an incorrect ECG signal may result in excessive dose and or poor image quality. Here are two examples of an incorrect ECG signal and a correct ECG signal. A correct ECG signal consists of clearly defined high are waves and a correctly defined our peak. The are peaks are appropriately detected when on top of the arpik ablu dot appears. In conclusion it is very important to know how to get a good ECG signal. It is also very important to be aware of possible challenges that may cause trouble. For this purpose, the learning goals of this movie are. Firstly, you will learn more about an ECG. What happens behind the scenes? How are the different parts of the heart and their activities related to the ECG curve? Secondly, you will learn the basics of the leadwire ECG system. Why is the correct placement of electrodes so important? Thirdly, you will learn about the challenges regarding the ECG signal and how to avoid them. What are the reasons why you may get a weak missing or wrong ECG signal? The ECG. An Electro cardio Gram ECG records electrical activity of the heart using electrodes placed on the skin. Specialized heart muscle cells generate electrical impulses. The Seeno 8 real node or SA node is the pacemaker where the electrical impulses generated. The impulse travels from the SA node through the internodal pathways to the atrioventricular node, or the AV node. This electrical impulse results in the P wave on the ECG signal. The AV node is responsible for conduction of the impulse from the Atria to the ventricles. The impulse is delayed slightly at this point to allow complete emptying of the Atria before the ventricles contract. The impulse continues through the AV bundle or bundle of his and down the left and right bundle branches of the Purkinje fibers. The Purkinje fibers conduct the impulse to all parts of the ventricles, causing contraction, and is visualized by the QRS complex of the ECG. As the signal passes out of the ventricles, they start to relax and recover the half circular shaped T wave on the ECG marks this relaxation. This cycle repeats with every heartbeat. For the ECG signal, the are waves are important. A good ECG signal has clearly defined high are waves. In summary, each wave or segment of the ECG signal corresponds to a certain event of the cardiac electrical cycle. The lead wire ECG system. The four leadwire ECG system provides electrocardiographic data from the frontal plane of the heart. Four electrodes are placed on the patient while the patient's arms are raised above the head. The first electrode labeled RA for right arm is affixed three fingers below the middle clavicle, on the right shoulder. The next electrode, labeled LA for left arm, is affixed three fingers below the middle clavicle on the left shoulder. The third electrode labeled LL for left leg is affixed below the 12th rib. A fourth electrode labeled RL for right leg is affixed below the 12th rib. The electrode RL is used as a ground reference point on the body. The three electrodes are ALA&LL. Form the ain't ovans triangle. Each side of the equilateral triangle represents one of the limb leads and can be seen as cardiac vector. An electric potential difference can be measured between two electrodes, lead 1, two or three. The axis of the lead one ranges from right arm to the left arm. The negative electrode is located on the right arm. The positive electrode on the left arm, so that the electrical stimulation runs from right to left. The axis of the lead two extends from the right arm to the left leg. The negative electrode is located on the right arm. The positive electrode on the left leg, the axis of lead three extends from the left arm to the left leg. The negative electrode is located on the left arm. The positive electrode on the left leg. This lead system provides 3 views of the heart locating the positive electrode is crucial to determining which area of the heart is viewed electrically. Metaphorically, the positive electrode serves as a mini video camera aimed at the heart in the direction of the negative electrode. These leads and their corresponding electrodes do not sit right on the heart. Rather, their vantage points offer a surface frontal view of the heart lead. One provides a left lateral view of the heart from the left ventricle to the left atrium. Perhaps the lead most chosen for cardiac monitoring lead to is an inferior lead viewing the apex of the heart between left and right ventricle. Lead three also provides an inferior view from right and left ventricles. Together, the three leads are able to simultaneously monitor multiple regions of the heart. As you can see, accurate placement of the ECG electrodes ensures consistent ECG readings. Inaccurate placement may result in duplication of some readings, while other areas may not be represented at all. Challenges of the ECG. Electrodes are positioned in the correct way. You should get a strong ECG signal. However, there are some reasons why you may get a week missing or even a wrong ECG signal. The three main challenges are skin preparation, electrode to patient contact. ECG signal. Now you will learn how to mitigate these challenges to ensure you get a high quality ECG signal. Skin preparation. Skin is a poor conductor of electricity. Any electronic noise may cause artifacts when the ECG signal is weak. When the skin is properly prepared, its conductivity is increased. Thus, the ECG signal is stronger than the noise and artifacts become in visibly small. Consequently, proper skin preparation is vital for a good ECG signal. Skin preparation. Instruct the patient to refrain from using body lotion which can disturb the transmission of the electrical signal to the electrode. Prepare the skin for application of electrodes by clipping or shaving her from electrode sites. Since excessive hair prevents good electrode contact. Clipping is preferred for hygienic reasons. Cleaning electrode sites thoroughly with water. You may use non alcoholic wipes. Alcohol may only be used on particularly greasy skin. Alcohol dries out the skin and may diminish electrical flow. However, it does remove grease. Dry the skin with moderate pressure to increase capillary blood flow to the tissues. Use a skin prep pad or medical sandpaper, for example. 3M2236 Red Dot trace prep. This removes dead skin cells, which allows electrical signals to travel to the electrodes and reduces artifact. Using an abrasive has been documented to reduce skin resistance and artifact with just one stroke of proper preparation tool. Peeling gel may be used as an alternative. Electrode to patient contact. Electrodes are placed on the patient's skin, thus incorrectly selecting and applying electrodes results in a noisy and disturbed ECG signal. Quality of electrodes. Old or dry electrodes do not transmit strong ECG signals. Always keep the electrodes in their original packaging in order to prevent them from drying out. Check the expiration date on the packages. Never use expired electrodes. Always use wet gel electrodes, for example, 2700 clear trace 2. Only wet gel electrodes are suitable for short term ECG needed at aceti. Use your hand to check that the gel on the electrode is wet. Never use electrode gel that has dried out. Do not use the same electrode twice. As soon as an electrode is removed from the patient skin, dispose of it and use a new electrode electrode application. Proper electrode application can help maximize ECG signal quality when possible and where appropriate explained the electrode application procedure to the patient to decrease anxiety and aid relaxation, ensure that the patient's arms are raised above the head, apply each electrode by pressing around the entire edge of the electrode. When positioning ECG electrodes avoid bonefro turban, sisin scar tissue, as these can interfere with. Impulse transmission avoid positioning electrodes in the scan field. Patients movement to reduce muscle tremor in patient movement. Attempt to warm a shivering patient or make them feel more comfortable in a reclined position. Use the knee roll below the knees of the patient for better comfort. Movement of electrodes. Once attached, electrodes should not move in anyway. Check electrodes periodically or if necessary. If an electrode moves easily, the electrode connection is too loose and may need to be changed. Tape down the lead wire about 3 to 4 inches or 10 centimeters away from the electrode, with slack in the wire to prevent it from pulling on the electrode. Defective ECG cables or lead wires. Avoid using cable extensions either at the patient side or table side. Always use the grounding cable delivered with the injector or scan table. Check that the electrode cable is clean and not damaged. Avoid loops in the ECG cable. High impedance. The Siemens CT scanners which are used for cardiac indicate signal strength and impedance on the gantry display. If the measured impedance of an electrode is too high, the gantry displays a triangle in yellow or red. In this case, remove the corresponding electrode. Re prepare skin with medical sandpaper and apply a new electrode. The impedance measurement can be repeated by pressing the channel button for more than two seconds. Apply a little ultrasound gel under the electrode. When the impedance is still too high. ECG signal. If a smooth noiseless signal is not displayed on the gantry monitor, or if error messages appear, the reason for poor ECG signal may be due to one of the following. ECG signal strength. The signal strength should be at least three bars. Apply a new electrode. If the signal strength indicator has less than two bars, it is important to select a suitable lead that shows the largest amplitude and cleanest signal so that a clearly defined our peak can be accurately detected. Electrical or static interference. It is difficult to deal with electrical interference. Sometimes it's challenging to filter without compromising the ECG complex due to its similarity to the ECG signal frequency. Therefore, it is best to monitor away from other equipment, including cell phones, and ensure cable and lead wires do not cross the power cables of other equipment or vent tubing. Use paper tissue without any plastic coating to cover the table. Give the patient cotton clothing or let the patients wear their own cotton clothes. Freshly washed clothing, especially synthetic materials, may cause static charge. Ask the patient to remove their shoes. Ensure that the radiographer is wearing shoes that are anti static. Room conditions everything on the table should be flat and secured. Cocoon the patient. Place overhanging parts such as clothing or sheets under the patient as they can easily interfere with the moving and static table parts removed. The paper roll Holder, as it often makes a mechanical connection between the moving and static parts of the table. Remove all objects from the table that are not required. Summary to summarize for a cardiac CT angio, a good ECG signal is very important and relate to dose scan duration and the right moment to scan. Therefore you need to be aware of the challenges skin preparation electrode to patient contact and ECG signal. In conclusion, it is important that you wipe the skin area multiple times with gentle pressure and a skin prep pad. Use wet gel electrodes and apply them at the correct locations. Have a look at the impedance of the electrodes, which is measured for every electrode by the scanner. The impedance measurement can be repeated by pressing the channel button for more than two seconds. Choose the ECG channel with strongest signal to ensure a good ECG signal.

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