By Z. Ugrasal. University of Wisconsin-River Falls.
The key to suc- cessful and proper interpretation is to employ a systematic methodology claritin 10mg sale allergy medicine yorkie. This chapter will lead you through a step by step approach to deciphering the data pro- vided through an electrocardiogram order claritin 10 mg fast delivery allergy testing gippsland. Leads V1–V3 sit over the right heart and are referred to as the right chest leads while leads V4–V6 are considered the left chest leads buy claritin 10mg line allergy testing kit for dogs. The R-wave reflects ventricular depolarization and is the first positive (upward) deflection following the P-wave buy claritin 10mg lowest price allergy medicine plus decongestant. The S-wave represents continuation of depolarization of the ventricles which produces electrical changes away from leads in which they are seen. By convention, lower case letters may be used to denote smaller voltage waves while capital letters signify larger voltage waves. For example, qR implies a small Q-wave followed by a larger R-wave while rsR¢ signifies small R and S-waves are followed by a larger R¢-wave. In these cases, each reduced wave must be multiplied by the reducing factor to restore Fig. All deflections in the chest leads should be multiplied by two for interpretation. These volt- age standardization marks are five small squares (one large square) in width when paper speed is standard (25 mm/s) and become twice as wide, i. Machines will not change paper speed automatically, if required, it must be set by the operator. This cardiac maturation occurs gradually over 3 Electrocardiography – Approach and Interpretation 39 40 Ra-id Abdulla and D. There are five small squares in each large square, thus making the duration of one large square 0. A table of normal values is useful when determining whether a given heart rate is appropriate for an individual (Table 3. Rhythm Heart rhythm is closely associated with heart rate measurement since both are caused by a common mechanism. An abnormal P-wave axis may indicate abnormal origination of cardiac electrical impulse, such as those seen in an ectopic atrial rhythm (Fig. Sinus bradycardia is present when all the above criteria are met with the exception of a slower than expected heart rate (Fig. The direction of electrical flow is from the right upper portion of the right atrium toward the left lower portion of the atria. Depolarization of the ventricles occurs via the bundle of His and normally com- pletes within 0. Right bundle branch block is common after surgical repair of a ventricular septal defect due to damage of the right bundle branches which course in close proximity to the edge of the ventricular septal defect. Superior axis deviation is a unique finding in patients with an atrioventricular canal defect due displacement of the bundles of His as a result of the atrial and ventricular septal defects (Fig. This is due to abnormal position of con- duction pathways as they are displaced by the inlet ventricular septal defect 48 Ra-id Abdulla and D. Alteration in T wave morphology may represent abnormal repolarization due to ischemia or abnormal electrolytes. Left Atrium Left atrial enlargement leads to a larger atrial mass which requires a longer period of depolarization. In addition, the larger than normal, atrial mass causes the depolarization to occur in different directions throughout the cycle leading to a bifid or biphasic P-wave. Therefore, neonates and young children have a proportionally larger right ventricular mass (as compared to the left ventricle) than is seen in older children and adults. An enlarged right atrium will cause the P-waves to be taller than normal (>2 mm in small children and >3 mm in older children and adults. This is followed by a second R-wave (R¢) which reflects the large right ventricular mass 3 Electrocardiography – Approach and Interpretation 51 reflect right ventricular hypertrophy in older children and adults. The downward progression of the R-wave into an S-wave may be over- come by continuing right ventricular depolarization, causing a reversal in the direction of electrical charges and a second upward wave in the right chest leads, manifesting as an R¢. Right ventricular hypertrophy leads to a tall R-wave in V1 and a deep S-wave in V6 due to the enlarged right ventricular mass. Although an rSr¢ pattern is normal in young children, if the second R-wave is taller than the initial R-wave, this reflects a larger right ventricular mass than normal. The initial depolarization of the ventricles starts in the ventricular septum in the same direction as that of the right ventricular wall mass as recorded in V1 and V2 resulting in an initial R-wave deflection in these leads without a Q-wave. In patients with right ventricular hypertrophy there may be deviation of the plane of the ventricular septum leading to a small Q-wave with resultant qR pattern in V1 and V2 52 Ra-id Abdulla and D. Similar to changes leading to an rsR¢ pattern described above, the right ventricular electrical domi- nance may be significant enough to completely mask any left ventricular forces in the right chest leads, resulting in a pure R-wave configuration (Fig. The ventricular septum may deviate secondary to right ventricular hypertrophy thus acquiring an abnormal position within the chest. This will cause an initial downward deflection in the right chest leads, manifesting as a q-wave. This is followed by a prominent R-wave reflecting right ventricular hypertrophy, thus resulting in a qR pattern in the right chest leads. This qR pattern can be also seen in dextrocardia, ventricular inversion, and pectus excavatum, all due to abnormal location of ventricular septum within the chest wall (Fig. Left Ventricle The R-wave in left chest leads represents depolarization of the left ventricle. Left ventricular hypertrophy results in increased depolarization voltages and manifests as a tall R-wave in the left chest leads and a deep S-wave in the right chest leads (Fig. This is typically the result of ventricular hypertrophy or rarely, an abnormal coronary artery origin resulting in inadequate coronary perfusion and myocardial ischemia. Interestingly, the low oxygen saturation from the pulmonary artery blood (70–75%) does not lead to ischemia. It is the low pressure in the pul- monary artery (typically <1/3 systemic pressure) that causes poor perfusion of the anomalous coronary artery which leads to ischemia, followed by infarction. Patients subsequently develop a dilated cardiomyopathy due to the large areas of infarcted left ventricle. Events causing acute insufficiency of coronary blood flow due to mechanical changes not currently well understood lead to compression of the abnormally located left coro- nary artery resulting in stunning of the myocardium and manifesting as syncope or sudden death. Reid Thompson, Thea Yosowitz, and Stephen Stone Key Facts • Echocardiography is noninvasive with no known harm to patients. Imaging and interpretation by specialists outside the field of pediatric cardiology is likely to lead to errors. Introduction Echocardiography has become the primary tool of the pediatric cardiologist for diagnosing structural heart disease. It is highly accurate when performed and inter- preted in an experienced laboratory, and in most cases is sufficient for understand- ing the anatomy and most of the hemodynamic consequences of the most W. As miniaturization of ultrasound technology and price points improve, it may eventually become feasible for noncardiologists to purchase portable ultrasound devices and incorporate imaging of the heart into their physical examination. However, due to the level of expertise involved in performing and interpreting a study to rule out congenital heart disease, screening for heart disease currently is still more appropriately done by a careful history and physical examination and will likely remain so for the foreseeable future. Echocardiography in infants and children, performed to diagnose or follow con- genital or acquired heart disease that affects this age group, is technically very different from adult echocardiography and requires specific equipment and exper- tise usually not found in typical adult echocardiography laboratories. This has been recognized by accreditation agencies that have developed specific requirements for quality control of pediatric studies. In addition, children under the age of three are often too uncooperative for a complete, comprehensive echocardiography, which can take up to 30–45 min, therefore in many cases sedation is required and should only be done in a laboratory with pediatric cardiologists on-site to optimize acquisi- tion and interpretation of the study. The pediatrician is often faced with the question of when an echocardiogram should be ordered directly versus requesting a cardiologist consultation at first.
To achieve fashion and social acceptance purchase claritin 10mg with amex allergy drops cost, extreme modiﬁcation of the hair shaft is often required generic claritin 10mg online allergy testing appointment. Even typical day-to-day cosmetic regimens have a subtle buy cheap claritin 10 mg online allergy shots once a year, yet accepted buy 10mg claritin with visa allergy treatment 32, nega- tive effect on hair. There is little doubt that hair that is clean, conditioned, and manageable reﬂects positively on the owner. To achieve healthy-looking hair requires the use of surfac- tants that, over time, elute lipids and proteins from the hair. It has long been recognized that regular washing steadily elutes proteinaceous material from the endocuticle, which results in an increase in the number of holes under each cuticle cell toward the tip of the ﬁber (Fig. Regular grooming causes physical damage to the cuticle and hyper-extension of the cortex. However, routine shampooing and combing form an acceptable balance between small nega- tive changes to the ﬁber and large visual beneﬁts to both the hairstyle and the owner. Indeed, it is only with the advent of modern shampoo and conditioner formulations that the individual can achieve the desired hair appearance for the days or years that a ﬁber remains on the head. It is only when the more aggressive physical and chemical processes are conducted on the hair that the rate of damage exceeds both the durability of hair and the replacement of ﬁbers. In truth they can, by matching the cosmetic damage to the rate of growth and not exceeding the parameters. If care is not taken, the end effects are rapid hair breakage, loss of shine, tangling, and occasionally, temporary loss of hair density and length. Permanent Hair Coloring The aim of this section is to look at the changes induced in the hair ﬁber by coloring processes and not the detailed chemistry of hair coloring. However, a brief overview gives a greater understanding of how and why the fundamental structure of the ﬁber is affected. Permanent hair colors result in a change to the natural color of hair that, although subject to fading, will only be completely lost when the hair is cut or re-colored. This class of products also includes products designed to lighten, or bleach, the natural color of hair. To change the natural color of hair the following steps must occur: (i) remove or lighten the natural hair color, i. To achieve the color, low pH hydrogen peroxide (developer) is mixed with high pH dyes (tint). The acti- vated or alkaline hydrogen peroxide both bleaches melanin in the cortex and develops the new colors from the tint. In particular, blonde shades are not simply achieved by bleaching melanin and they require the formation of new dye colors to offset red and brass tones left by the incom- plete degradation of melanin. As alkaline hydrogen peroxide diffuses through the ﬁber it encounters transition metal ions that occur naturally in hair, as well as those acquired from the environment, e. Rapid degradation of peroxide forms the highly damaging and non- speciﬁc hydroxyl radical. A fundamental challenge to the colorant formulator is accessing and decolorizing mela- nin that occurs only in the cortex while minimizing damage to the rest of the ﬁber. First, alkaline peroxide must travel through the cuticle and will cause damage en route. Due to the relatively low concentration of melanin in Caucasian hair there is a greater chance that the peroxide will interact with the hair structure and damage the proteins in the cortex than that it will interact with melanin. As a result, permanent hair colors cause measurable damage to the tensile and torsional properties of the hair ﬁber. All unmodiﬁed cuticle cells are covered in a covalently bound fatty acid on the outer aspect of the cell. The fatty acid 18-methyl eicosanoic acid, termed the f-layer (4), is readily cleaved by perhydrolysis, which changes the surface of the cell from hydrophobic to hydrophilic. First, when the hair is wet the hair ﬁbers are held tightly together by ﬁlms of water. Second, many conventional silicone-based conditioners, which are typically hydrophobic in nature, fail to deposit on the hair and as a result provide little or no protection. Fortunately, the level of damage is relatively low and can be managed as is evidenced by the numerous examples of individuals with long hair who have used colorants multiple times. But it is essential for patients to understand that the hair is changed by the coloring process 24 Gummer and, while its appearance is enhanced its properties are altered. Failure of patients to increase conditioning, which will counteract these changes, will lead to rapid weathering and break- age and is often typiﬁed by trichorrhexis nodosa. The patient must be encouraged to reduce the frequency of coloring and the amount of styling, while greatly increasing the amount of conditioning. High-Lift Bleaches The peroxide blonde hair color worn by Marilyn Monroe cannot be achieved with hydrogen peroxide alone. The addition of ammonium persulphate, which is usually supplied as a pow- der, is required to completely decolorize melanin and achieve the platinum blonde effect. This process causes damage of a much higher magnitude than conventional permanent colors and hence the degree of haircare must be suitably increased. Permanent colors and high-lift bleaches are biologically aggressive treatments that are well-tolerated by the hair when utilized properly. Problems such as hair breakage and straw- like appearance can result from a lack of understanding of how the hair is changed by these processes. A patient with shoulder-length hair will require treatments once every six to eight weeks. As a result, the ends of the ﬁbers will have experienced signiﬁcantly more chemical and physical insult compared to the roots. Permanent Changes in Hair Shape Two main practices are involved in permanently changing the shape of individual ﬁbers, i. While different chemistry is used by these two processes, both have a similar clinical impact on the ﬁber. Permanent waves, generally used to increase curls, are based on alkaline ammonium thyo- glycollate. This reduces disulphide bonds in the cuticle and cortex and allows hydrogen perox- ide to reform bonds in their new position. As covalent bonds adopt new positions, the extensive network of salt bridges and hydrogen bonds do so as well. Although the process and formula- tions are quite different, it should be remembered that thyoglycollates are also the bases for effective depilatories. When used for hair removal the reductive step is left to progress further and is not neutralized by hydrogen peroxide. There are a number of recorded cases of severe hair breakage following permanent waves, no doubt caused by poor control of the reductive step. Most relaxers are used to straighten curly hair, in which case the term relaxer is something of a misnomer. In order to straighten the hair it must also be pulled straight to form its new shape, so straight hair is not a relaxed state of a curl. Relaxers or straighteners require additional tension to pull the ﬁber straight on already weak hair, and may also involve the use of hot irons resulting in hair that is particularly weak but far from relaxed. One should remember that high concentrations of sodium hydroxide are a useful tool for dissolving hair for analytical tests. Relaxers left on for too long can certainly cause widespread hair breakage close to the scalp as well as extensive scalp irritation. Both permanent waves and relaxers remove the f-layer from the ﬁber and damage inter- cellular cements. In addition, changes in the extractable proteins and amino acid proﬁles are always evident. These combined effects result in ﬁbers that are hydrophilic, of reduced tensile and torsional strength, are prone to tangling, and show an increased rate of weathering (Table 2).
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