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Clinical Applications by Donnell J. Creel Webvision. Donnell J. Creel. Introduction. Electrophysiological testing of patients with retinal disease began in clinical departments in the late nineteen forties. Images/discrete-wavelet-transform-a-signal-processing-approach-1st-edition-pd.jpg' alt='An Introduction To Wavelets Pdf' title='An Introduction To Wavelets Pdf' />MIT Mathematics courses available online and for free. Stupid Spherical Harmonics SH Tricks Peter Pike Sloan. Microsoft Corporation. Abstract. This paper is a companion to a GDC 2008 Lecture with the same title. Email markrainsun atgmail dotcom Here are some listed. PDFA Brief Introduction To Fluid Mechanics, 5th Edition INSTRUCTOR SOLUTIONS MANUAL. Yamaha Xvz 1300 Xvz13tf Royal Star Service Repair Manual Pdf 1999 Onwards Document about Yamaha Xvz 1300 Xvz13tf Royal Star Service Repair Manual. An Introduction To Wavelets Pdf' title='An Introduction To Wavelets Pdf' />Under the influence of the Swedish pioneers, Holmgren 1. Granit 1. 93. 3, the electroretinogram was being dissected into component parts and early intraretinal electrode studies were beginning to tell which cells or cell layers gave rise to the various components. A detailed discussion of the electroretinogram, or ERG as it is commonly abbreviated, is found in the accompanying chapter by Ido Perlman. A little after the introduction of the ERG as a test of the state of the patients retina, another diagnostic test called the electrooculogram EOG was introduced to the clinic Arden et al., 1. The EOG had advantages over the ERG in that electrodes did not touch the surface of the eye. The changes in the standing potential across the eyeball were recorded by skin electrodes during simple eye movements and after exposure to periods of light and dark. Over the years ERG recording techniques have become progressively more sophisticated in the clinical setting. With the advent of perimetry, optical coherence tomography OCT and pattern ERG techniques, more precise mapping of dysfunctional areas of the retina is now possible. The most recent advance in ERG technology is the multifocal electroretinogram mf. ERG. The mf. ERG provides a detailed assessment of the health of the central retina. Where the previous chapter The electroretinogram ERG, Ido Perlman presents the basic science behind the waveforms and components of the massed ERG response, in this chapter the intention is to show the clinical use of the various electrophysiological tests. The chapter is based on experience in the ERG clinic of the Moran Eye Center. The electroretinogram ERG. The global or full field electroretinogram ERG is a mass electrical response of the retina to photic stimulation. The ERG is a test used worldwide to assess the status of the retina in eye diseases in human patients and in laboratory animals used as models of retinal disease. The basic method of recording the electrical response known as the global or full field ERG is by stimulating the eye with a bright light source such as a flash produced by LEDs or a strobe lamp. The flash of light elicits a biphasic waveform recordable at the cornea similar to that illustrated below Fig 1. The two components that are most often measured are the a and b waves. The a wave is the first large negative component, followed by the b wave which is corneal positive and usually larger in amplitude. Fig. 1 The biphasic waveform of the typical normal patient. An Early Receptor Potential ERP is a very fast biphasic wave appearing in the first 2 milliseconds following a bright flash, prior to the a wave, reflecting the earliest chemical responses to light in the receptor outer segments Figure 1a. Approximately 7. The ERP latency is less than 1 microsecond. Due to photovoltaic effects ERPs are best recorded using no metal such as with cotton wick contact shown in Fig 4. The ERP is difficult to record and is not commonly used clinically. Wordperfect Office 12 Crack. Fig. Early receptor potential occurring in first two milliseconds prior to a wave. Figure 1b depicts a concocted ERG of all components if one would stimulate the retina with a long light pulse producing an off response. Fig. 1b. Hypothetical ERG showing all components if stimulus included a long pulse of light. Two principal measures of the ERG waveform are taken 1 The amplitude a from the baseline to the negative trough of the a wave, and the amplitude of the b wave measured from the trough of the a wave to the following peak of the b wave and 2 the time t from flash onset to the trough of the a wave and the time t from flash onset to the peak of the b wave Fig. These times are referred to as implicit times in the jargon of electroretinography. Fig. 2 Amplitude and implicit time measurements of the ERG waveform. The a wave, sometimes called the late receptor potential, reflects the general physiological health of the photoreceptors in the outer retina. In contrast, the b wave reflects the health of the inner layers of the retina, including the ON bipolar cells and the Muller cells Miller and Dowling, 1. Two other waveforms that are sometimes recorded in the clinic are the c wave originating in the pigment epithelium Marmor and Hock, 1. OFF bipolar cells see Figure 3. Later we shall discuss some wavelets that occur on the rising phase of the b wave known as oscillitatory potentials OPs. OPs are thought to reflect activity in amacrine cells Fig. Fig. 3 Cartoon of the retina to show where the major components of the ERG originate. The ERG of a normal full term infant looks similar to a mature ERG. A normal ERG in a newborn infant can be small amplitude the first couple of months. The ERG attains peak amplitude in adolescence and slowly declines in amplitude throughout life Weleber, 1. After age 5. 5 6. ERG declines even more. Implicit times slow gradually from adolescence through old age as well. Below are two figures illustrating how the b wave attenuates in amplitude with age and slows in its implicit time Fig. There is considerable variation among individuals but the linear regression line in each figure indicates the trend of aging affects on the ERG. Fig. 3a Scatter plot of b waves amplitudes and latencies with age with regression lines to show the aging effects. ERG recording electrodes. The ERG can be recorded several ways. The pupil is usually dilated. Shin Koihime Musou Otome Ryouran Sangokushi Engi Yahoo. There are a number of corneal ERG electrodes that are in common use. Some are speculum structures Fig. Some versions use carbon, wire or gold foil to record electrical activity. There are also cotton wick electrodes Fig. Fig. 4 Speculum or Burian type electrodes used to record the human ERGThere are yet other simpler ERG recording devices Fig. Mylar tape that can be inserted between the lower lid and scleracornea. Most electrodes are monopolar, i. Some are bipolar with the reference electrodes built into a metal surface on a speculum. Fig. 5 Other simple types of electrode used to record the human ERGEach of these electrodes record large voltage responses directly from the cornea or sclera and each have advantages and disadvantages. We use Burian speculum electrodes when possible. Sizes are available down to a size that fits in the eye of most full term babies. When the eye is too small for speculum recording electrodes we use the ERG Jet type most of the time. When the eye is very small such as in some microphthalmic eyes or cases of trauma to tissue surrounding the eye, we use ERG Jet, DTL silver thread or Arden gold foil. The ERG can also be recorded using skin electrodes placed just above and below the eye, or below the eye and next to the lateral canthus. Since skin electrodes are not in direct contact with the eye there is significant attenuation in amplitude of the ERG, so a number of individual responses to flash stimulation are usually averaged by computer. Pictured in Figure 6 is a comparison of bright white flash ERGs recorded from the same person using three types of recording devices and an averaged ERG from skin electrodes. Fig. 6 Typical ERGs as recorded with different electrodes. If electrodes are to be reused, they should be sterilized with a solution that neutralizes prion transmitted diseases such as Creutzfeldt Jakob disease CJD. ACCAHAESC Guidelines for the Management of Patients With Atrial Fibrillation Executive Summary A Report of the American College of CardiologyAmerican Heart Association Task Force on Practice Guidelines and the European Society of Cardiology CommitteeThe major issues in management of patients with AF are related to the arrhythmia itself and to prevention of thromboembolism. In patients with persistent AF, there are fundamentally 2 ways to manage the dysrhythmia to restore and maintain sinus rhythm or to allow AF to continue and ensure that the ventricular rate is controlled. A. Rhythm Control vs Heart Rate Control. Reasons for restoration and maintenance of sinus rhythm in patients with AF include relief of symptoms, prevention of embolism, and avoidance of cardiomyopathy. B. Cardioversion. Basis for Cardioversion of AFCardioversion is often performed electively to restore sinus rhythm in patients with persistent AF. The need for cardioversion can be immediate, however, when the arrhythmia is the main factor responsible for acute HF, hypotension, or worsening of angina pectoris in a patient with CAD. Nevertheless, cardioversion carries a risk of thromboembolism unless anticoagulation prophylaxis is initiated before the procedure, and this risk appears to be greatest when the arrhythmia has been present more than 4. Methods of Cardioversion. Cardioversion can be achieved by means of drugs or electrical shocks. Drugs were commonly used before electrical cardioversion became a standard procedure. The development of new drugs has increased the popularity of pharmacological cardioversion, although some disadvantages persist, including the risk of drug induced torsade de pointes ventricular tachycardia or other serious arrhythmias. Pharmacological cardioversion is still less effective than electrical cardioversion, but the latter requires conscious sedation or anesthesia, whereas the former does not. The risk of thromboembolism or stroke does not differ between pharmacological and electrical cardioversion. Thus, recommendations for anticoagulation are the same for both methods. C. Pharmacological Cardioversion. Pharmacological cardioversion appears to be most effective when initiated within 7 days after the onset of AF 8. Most such patients have paroxysmal AF, a first documented episode of AF, or an unknown pattern of AF at the time of treatment. See Section III, Classification. A large proportion of patients with recent onset AF experience spontaneous cardioversion within 2. This is less likely to occur when AF has persisted for more than 7 days. The relative efficacy of various drugs differs for pharmacological cardioversion of AF and atrial flutter, yet many studies of drug therapy for AF have included patients with atrial flutter. The dose, route, and rapidity of administration influence efficacy. Reference is made to the Vaughan Williams classification of antiarrhythmic drugs 9. Table 2. A summary of recommendations is presented in Tables 1. Section IX B, Recommendations for Pharmacological and Electrical Cardioversion of AF, Tables 1. Although clinical use of the antiarrhythmic drugs listed has been approved by regulatory agencies, therapeutic use for AF has not been mentioned or approved in all cases in each country. The recommendations given in this document do not necessarily adhere to governmental regulations and labeling requirements. Table 2. 61. 35. Vaughan Williams Classification of Antiarrhythmic Drug Actions. A frequent issue related to pharmacological cardioversion is whether the antiarrhythmic drug should be started in the hospital or on an outpatient basis. The major concern is the potential for serious adverse effects, including torsade de pointes ventricular tachycardia. With the exception of those involving low dose oral amiodarone 9. D. Electrical Cardioversion. Direct current cardioversion involves an electrical shock synchronized with the intrinsic activity of the heart. This ensures that electrical stimulation does not occur during the vulnerable phase of the cardiac cycle 9. Successful cardioversion of AF depends on the nature of the underlying heart disease and the current density delivered to the atrial myocardium. The latter, in turn, depends on the voltage of the defibrillator capacitor, the output waveform, the size and position of the electrode paddles, and transthoracic impedance. In a randomized controlled study of 3. The energy requirement was lower and overall success was greater with the anterior posterior configuration 8. Cardioversion is performed with the patient having fasted and under adequate anesthesia. Short acting anesthetic agents are preferred, because cardioversion patients are well suited to day care and should recover rapidly after the procedure 9. An initial shock of 1. J is often too low, and an initial energy of 2. J or greater is recommended for electrical cardioversion of AF. Devices that deliver current with a biphasic waveform appear to achieve cardioversion at lower energy levels than those that use a monophasic waveform. The primary success rate as measured 3 days after cardioversion in 1. Only 2. 3 of the patients remained in sinus rhythm after 1 year and 1. For patients who relapsed again, a third cardioversion resulted in sinus rhythm in 5. Thus, sinus rhythm can be restored in a substantial proportion of patients by direct current cardioversion, but the rate of relapse is high unless antiarrhythmic drug therapy is given concomitantly. Cardioversion of patients with implanted pacemaker and defibrillator devices is safe when appropriate precautions are taken. The device should be interrogated immediately before and after cardioversion to verify appropriate function. The paddles used for external cardioversion should be positioned as distant as possible from the device, preferably in the anterior posterior configuration. The risks of electrical cardioversion are mainly related to embolic events and cardiac arrhythmias. Thromboembolic events have been reported in 1 to 7 of patients who did not receive anticoagulation before cardioversion 1. Various brief arrhythmias might arise, especially ventricular and supraventricular premature beats, bradycardia, and short periods of sinus arrest 1. Ventricular tachycardia and fibrillation can be precipitated in patients with hypokalemia or digitalis intoxication 1. A slow ventricular response to AF in the absence of drugs that slow AV nodal conduction can indicate conduction defect. The patient should be evaluated before cardioversion with these issues in mind to avoid symptomatic bradycardia 1. Transient ST segment elevation can appear on the ECG after cardioversion 1. MB can rise even without apparent myocardial damage. Prophylactic drug therapy to prevent early recurrence of AF should be considered individually for each patient. Should relapse particularly early relapse occur, antiarrhythmic therapy is recommended in conjunction with the second attempt. Further cardioversion is of limited value. In highly symptomatic patients, infrequently repeated cardioversion can be an acceptable approach. E. Maintenance of Sinus Rhythm. Pharmacological Therapy to Prevent Recurrence of AFMaintenance of sinus rhythm is relevant in patients with paroxysmal AF in whom episodes terminate spontaneously and persistent AF in whom electrical or pharmacological cardioversion is necessary to restore sinus rhythm.