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Raised Intracranial Pressure. Upper Limb Lead reversal. Left Main Coronary artery occlusion. Left Ventricular Hypertrophy. Poor R Wave Progression. Posterior Myocardial Infarction. Right Ventricular Hypertrophy. Right Ventricular Infarction. Overdose: TCA. Ventricular Fibrillation. Ventricular Tachycardia. Diagnosis, Wenckebach Squared? P wave Q wave R wave T wave. EKG Library.
Chest Pain, acute, transient viral myositis associated with Coxsackievirus B. Epidemic Myalgia, pleurodynia. Accelerated Ventricular Rhythm, Isorhythmic AV dissociation, fusion, capture beat, interference-dissociation. Atrial Fibrillation AF.
Block: Mobitz 2 Hay. Block: Fixed Ratio. Block: High Grade. Pre-excitation Syndromes. Block: Bifascicular Block. Biventricular Hypertrophy. Dilated Cardiomyopathy. Junctional Escape Rhythm. The device shall have the capability of displaying the ECG signal in the presence of pacemaker pulses with amplitudes between 2 mV and mV, durations between 0. For pacemaker pulses having durations between 0. All pacing leads have two electrodes, with the location of the electrodes determining the polarity of the signal.
In unipolar pacing, the pacing leads consist of an electrode at the tip of a single pacing lead and the metal wall of the pacemaker housing can itself, so just one lead is inserted into the heart. The pacing artifacts caused by this mode of pacing can be several hundred millivolts at the skin surface with a width of a couple of milliseconds.
Unipolar pacing is no longer commonly used. In bipolar pacing, the heart is paced from the electrode at the tip of the pacing lead. The return electrode is a ring electrode located very close to the tip electrode. Most pacing artifacts are now created by bipolar pacing. The amplitude of the artifact can be much smaller when the detection vector does not line up directly with the pacing lead vector.maisonducalvet.com/yunquera-como-conocer-gente.php
Pin on Pacemakers-Wired4life
Most pacing pulses have very fast rising edges. The rise time measured at the pacemaker output is generally about ns. When measured at the skin surface, the rise time will be slightly slower because of the inductance and capacitance of the pacing lead. Complex devices with built-in protection, pacemakers can produce high-speed glitches that do not affect the heart but do affect pacemaker detection circuits. Figure 6 shows an example of an ideal pacing artifact.
Introduction to Pacemaker Rhythms
The positive pulse has a fast rising edge. After the pulse reaches its maximum amplitude, a capacitive droop follows, and then the trailing edge occurs. The artifact then changes polarity for the recharge portion of the pacing pulse. This recharge pulse is required so that the heart tissue is left with a net-zero charge. With a monophasic pulse, ions would build up around the electrodes, creating a dc charge that could lead to necropsy of the heart tissue. Introducing cardiac resynchronization devices adds another degree of complication in detecting and displaying pacing artifacts.
These devices pace the patient in the right atrium and both ventricles. The pulses in the two ventricles can fall close together, overlap, or occur at exactly the same time; and the left ventricle can even be paced before the right ventricle. Currently, most devices pace both ventricles at the same time, but studies have shown that adjusting the timing will benefit most patients by yielding a higher cardiac output.
Detecting and displaying both pulses separately is not always possible, and many times they will appear as a single pulse on the ECG electrodes. If both pulses occur at the same time, with the leads oriented in opposite directions, the pulses could actually cancel each other out on the skin surface. The probability of this occurring is very remote, but one can envision the appearance of two ventricle pacing artifacts on the skin surface with opposite polarities. If the two pulses were offset by a small time interval, the resulting pulse shape could be very complex.
Figure 7 shows scope traces of a cardiac resynchronization device pacing in a saline tank. This is a standard test environment for pacemaker validation; it is believed to be similar to the conductivity of the human body. The close proximity of the scope probes to the pacing leads causes the amplitudes to be much larger than what would be expected on the skin surface.
In addition, the low impedance presented by the saline solution to the ECG electrodes results in much less noise than would normally be seen in a skin surface measurement. The first pulse is the atrial, the second pulse is the right ventricle, and the third pulse is the left ventricle.
The leads were placed in the saline tank with vectors optimized to see the pulses clearly. The negative-going pulse is the pace and the positive-going pulse is the recharge. The amplitude of the atrial pulse is slightly larger than the other two pulse amplitudes because the lead was in a slightly better vector than the ventricle leads, but in actuality, all three pacing outputs in the resynchronization device were programmed to have the same amplitude and width. With real patients, the amplitudes and widths are often different for each pacemaker lead.
With this understanding of the morphology and origin of the signals of interest, we can focus on the subject of detecting a pacing artifact.
Simplified Interpretation of Pacemaker Ecgs
By their nature, it is impossible to detect all pacing artifacts and reject all possible noise sources in a cost-effective manner. Among the challenges are the number of chambers that pace detection must monitor, the interference signals encountered, and the variety of pacemakers from differing manufacturers.
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Solutions for detecting artifacts may range from hardware solutions to digital algorithms. These will all be discussed in more detail now. The pacing leads for cardiac resynchronization devices will not all have the same vector. The right atrium lead usually aligns with Lead II, but it can sometimes point straight out of the chest, so a Vx vector may be needed to see it.
The right ventricle lead is usually placed at the apex of the right ventricle, so it usually aligns well with Lead II. The left ventricle pacing lead, threaded through the coronary sinus, is actually on the outside of the left ventricle. This lead usually aligns with Lead II but may have a V-axis orientation. The pacing leads of implantable defibrillators and resynchronization devices are sometimes placed in areas of the heart that have not had an infarction.
Placing them around infarcts is the main reason that this system uses three vectors and requires a high-performance pacing-artifact detection function. One of the major noise sources is the H-field telemetry scheme used by most implantable heart devices.
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Other sources of noise include transthoracic impedance measurements for respiration, electric cautery, and conducted noises from other medical devices connected to the patient. To further complicate the problem of acquiring pacing artifacts, each pacemaker manufacturer uses a different telemetry scheme. In some cases, a single manufacturer may use many different telemetry systems for different implantable device models.