Adjunctive Modalities Defibrillation, Cardioversion, Pacemakers, EP Notes PDF

Acute dysrhythmias may be treated with medications or with external electrical therapy (emergency defibrillation, cardioversion, or pacing). If medications alone are ineffective in eliminating or decreasing the dysrhythmia, certain adjunctive mechanical therapies are available. The most common thera...

Acute dysrhythmias may be treated with medications or with external electrical therapy (emergency defibrillation, cardioversion, or pacing). If medications alone are ineffective in eliminating or decreasing the dysrhythmia, certain adjunctive mechanical therapies are available. The most common therapies are elective cardioversion and defibrillation for acute tachydysrhythmia, and implantable devices (pacemakers for bradycardias and ICDs for chronic tachydysrhythmias). Surgical treatments, although less common, are also available. Your clinical packet has much more information so be sure to review it. A device called a *defibrillator,* is used for both cardioversion and defibrillation. The electrical voltage required to defibrillate the heart is usually greater than that required for cardioversion and may cause more myocardial damage. Only biphasic types of defibrillators are now manufactured; these deliver an electrical charge from one paddle that then automatically redirects its charge back to the originating paddle. The electrical current may be delivered externally through the skin with the use of paddles or with conductor pads. When you get to your units, ask your nurse or clinical instructor go over this. You will find it on top of the crash cart. Locate the power button. Always turn this on first. Most defibrillators only have the pads -- you can monitor the EKG rhythm, cardiovert, and defibrillator with just the pads on the patient. The paddles or pads may be placed on the front of the chest upper right and lateral left or one pad may be placed on the left upper part of the chest and the other pad placed on the patient's back just under the left scapula. Defibrillator multifunction conductor pads contain a conductive medium and are connected to the defibrillator to allow for hands-off defibrillation. This method reduces the risk of touching the patient during the procedure and increases electrical safety. In most settings of higher acuity patients, the nurses are expected to identify shockable/paceable rhythms, but in other areas such as L&D, Med/Surg, there is the analyze button that can be pushed and this becomes an AED. The energy button increases or decreases the amount of electrical current -- this can be between 25 joules up to 360 joules (some only go to 200 joules depending on the manufacturer). The charge button will "charge" the defibrillator up to that amount of joules when you are ready to shock the patient. The lightning bolt will deliver the joules. Prior to pushing this button one needs to make sure no one is touching the patient and the BVM has been removed from the pt. Anyone touching the patient could also receive the electrical current causing them to develop a lethal dysrhythmia. The "synch" button is used in cardioversion. Electrical cardioversion involves the delivery of a "timed" electrical current synchronized to the patient's rhythm to terminate a tachycardic dysrhythmia. Both defibrillation and cardioversion are used to try to stop the abnormal electrical impulses traveling through the heart. One major difference between cardioversion and defibrillation is the timing of the delivery of electrical current. In cardioversion, the delivery of the electrical current is synchronized with the patient's electrical events; in defibrillation, the delivery of the current is immediate and unsynchronized. Cardioversion will send an electrical impulse at a specific time through the myocardium as an electrical "reboot" of the conduction system. The defibrillator is set to synchronize with the ECG on a cardiac monitor so that the electrical impulse discharges during ventricular depolarization (QRS complex). The synchronization prevents the discharge from occurring during the vulnerable period of repolarization (T wave), which could result in VT or ventricular fibrillation. The ECG monitor connected to the external defibrillator usually displays a mark or line that indicates sensing of a QRS complex. Sometimes the lead and the electrodes must be changed for the monitor to recognize the patient's QRS complex. When the synchronizer is on, no electrical current is delivered if the defibrillator does not identify a QRS complex. Therefore, it is important to ensure that the patient is connected to the monitor and to select a lead that has the most appropriate sensing of the QRS. Because there may be a short delay until recognition of the QRS, the discharge buttons of an external manual defibrillator must be held down until the shock has been delivered. In most monitors, the synchronization mode must be reactivated if the initial cardioversion was ineffective and another cardioversion is needed (the device defaults to unsynchronized defibrillation mode). It is used for tachycardic dysrhythmias electively or in emergent situations if the patient is starting to decompensate (SOB, angina, hypotension, diaphoretic). If the cardioversion is elective and the dysrhythmia such as atrial fibrillation has lasted longer than 48 hours, anticoagulation for a few weeks before cardioversion may be indicated. Digoxin is usually withheld for 48 hours before cardioversion to ensure the resumption of sinus rhythm with normal conduction. The patient is instructed not to eat or drink for at least 4 hours before the procedure. Conductor pads are positioned and the patient will receive moderate sedation IV as well as an analgesic medication or anesthesia. Respiration is then supported with supplemental oxygen delivered by a bag-valve mask device if needed with suction equipment readily available. Although patients rarely require intubation, equipment is nearby in case it is needed. The amount of voltage used varies from 50 to 360 joules, depending on the defibrillator's technology, the type and duration of the dysrhythmia, and the size and hemodynamic status of the patient. The patient may be cardioverted several times with an increase in the joules each time. Remember: the default after each shock resets the defibrillator off synch so the button must be pushed each sequential time. Always confirm the synch is on by looking at the marking on the screen of the defibrillator monitor. Indications of a successful response are conversion to sinus rhythm, adequate peripheral pulses, and adequate blood pressure. Because of the sedation, airway patency must be maintained and the patient's state of consciousness assessed. Vital signs and oxygen saturation are monitored and recorded until the patient is stable and recovered from sedation and analgesic medications or anesthesia. ECG monitoring is required during and after. Defibrillation is used in emergency situations as the treatment of choice for ventricular fibrillation and pulseless VT where the ventricles area chaotically beating and not generating a pulse with it, the most common cause of abrupt loss of cardiac function and sudden cardiac death. Defibrillation is not used for patients who are conscious or have a pulse. The energy setting for the initial and subsequent shocks using a monophasic defibrillator should be set at 360 joules. The energy setting for the initial shock using a biphasic defibrillator may be set at 150 to 200 joules, with the same or an increasing dose with subsequent shocks. The sooner defibrillation is used, the better the survival rate. Several studies have demonstrated that early defibrillation performed by lay people in a community setting can increase the survival rate. If immediate CPR is provided and defibrillation is performed within 5 minutes, more adults in ventricular fibrillation may survive with intact neurologic function. Epinephrine is given after initial unsuccessful defibrillation to make it easier to convert the arrhythmia to a normal rhythm with the next defibrillation. This medication may also increase cerebral and coronary artery blood flow. Antiarrhythmic medications such as amiodarone, lidocaine, or magnesium may be given if ventricular arrhythmia persists. This treatment with continuous CPR, medication administration, and defibrillation continues until a stable rhythm resumes or until it is determined that the patient cannot be revived. A pacemaker is an electronic device that provides electrical stimuli to the heart muscle. Pacemakers are usually used when a patient has a permanent or temporary slower-than-normal impulse formation, or a symptomatic AV or ventricular conduction disturbance. They may also be used to control some tachydysrhythmias that do not respond to medication. Biventricular (both ventricles) pacing, also called **cardiac resynchronization therapy (CRT)**, may be used to treat advanced heart failure. Pacemaker technology also may be used in an ICD. Pacemakers can be permanent or temporary. Temporary pacemakers are used to support patients until they improve or receive a permanent. Temporary pacemakers are used only in hospital settings. Pacemakers consist of two components: an electronic pulse generator and pacemaker electrodes, which are located on leads or wires. The generator contains the circuitry and batteries that determine the rate and the strength or mAs of the electrical stimulus delivered to the heart. The generator also has circuitry that can detect the intracardiac electrical activity to cause an appropriate response; this component of pacing is called sensitivity and is measured in millivolts (mV). Sensitivity is set at the level that the intracardiac electrical activity must exceed to be sensed by the device. Leads, which carry the impulse created by the generator to the heart, can be threaded by fluoroscopy through a major vein into the heart, usually the right atrium and ventricle (endocardial leads), or they can be lightly sutured onto the outside of the heart and brought through the chest wall during open heart surgery (epicardial wires). The epicardial wires are always temporary and are removed by a gentle tug a few days after surgery. The endocardial leads may be temporarily placed with catheters through a vein, usually guided by fluoroscopy. The endocardial and epicardial wires are connected to a temporary generator, which is about the size of a small paperback book. The energy source for a temporary generator is a common household battery. Monitoring for pacemaker malfunctioning and battery failure is a nursing responsibility. The endocardial leads also may be placed permanently, passed into the heart through the subclavian, axillary, or cephalic vein, and connected to a permanent generator. Most current leads have a fixation mechanism at the end of the lead that allows precise positioning and avoidance of dislodgement. The permanent generator, the size of a large book of matches, is usually implanted in a subcutaneous pocket created in the pectoral region, below the clavicle, or behind the breast. This procedure usually takes about 1 hour, and it is performed in a cardiac catheterization laboratory using a local anesthetic and moderate sedation. Leadless pacemakers, a newer type of permanent pacemaker, are 90% smaller than transvenous pacemakers. They feature a self-contained, single-unit pulse generator and electrode that is inserted transvenously directly into the right ventricle Permanent pacemaker generators are insulated to protect against body moisture and warmth and have filters that protect them from electrical interference from most household devices, motors, and appliances. Lithium cells are most commonly used; they last approximately 5 to 15 years, depending on the type of pacemaker, how it is programmed, and how often it is used. Most pacemakers have an elective replacement indicator (ERI), which is a signal that indicates when the battery is approaching depletion. The pacemaker continues to function for several months after the appearance of ERI to ensure that there is adequate time for a battery replacement. Although some batteries are rechargeable, most are not. Because the battery is permanently sealed in the pacemaker, the entire generator must be replaced. To replace a failing generator of a transvenous pacemaker, the leads are disconnected, the old generator is removed, and a new generator is reconnected to the existing leads and reimplanted in the already existing subcutaneous pocket. Sometimes the leads are also replaced. When leadless pacemaker batteries signal that they must be replaced, a new system is simply implanted and the old battery is then disabled. Battery replacement of both systems is usually performed using a local anesthetic. The patient usually can be discharged from the hospital the day of the procedure. **Transcutaneous pacing:** If a patient suddenly develops a bradycardia, is symptomatic but has a pulse, and is unresponsive to atropine, emergency pacing may be started with transcutaneous pacing, which most defibrillators are now equipped to perform. Large pacing ECG electrodes (sometimes the same conductive pads used for cardioversion and defibrillation) are placed on the patient's chest and back. The electrodes are connected to the defibrillator, which is the temporary pacemaker generator. Because the impulse must travel through the patient's skin and tissue before reaching the heart, transcutaneous pacing can cause significant discomfort (burning sensation and involuntary muscle contraction) and is intended to be used only in emergencies for short periods of time. This type of pacing necessitates hospitalization. If the patient is alert, sedation and analgesia may be given. After transcutaneous pacing, the skin under the electrode should be inspected for erythema and burns. Transcutaneous pacing is not indicated for pulseless bradycardia. Because of the sophistication and wide use of pacemakers, a universal code has been adopted to provide a means of safe communication about their function. The coding is referred to as the NASPE-BPEG code because it is sanctioned by the North American Society of Pacing and Electrophysiology and the British Pacing and Electrophysiology Group. The complete code consists of five letters; the fourth and fifth letters are used only with permanent pacemakers. - The first letter of the code identifies the chamber or chambers being paced (i.e., the chamber containing a pacing electrode). The letter characters for this code are A (atrium), V (ventricle), or D (dual, meaning both A and V). - The second letter identifies the chamber or chambers being sensed by the pacemaker generator. Information from the electrode within the chamber is sent to the generator for interpretation and action by the generator. The letter characters are A (atrium), V (ventricle), D (dual), and O (indicating that the sensing function is turned off). - The third letter of the code describes the type of response that will be made by the pacemaker to what is sensed. The letter characters used to describe this response are I (inhibited), T (triggered), D (dual---inhibited and triggered), and O (none). Inhibited response means that the response of the pacemaker is controlled by the activity of the patient's heart---that is, when the patient's heart beats, the pacemaker does not function, but when the heart does not beat, the pacemaker does function. In contrast, a triggered response means that the pacemaker responds (paces the heart) when it senses intrinsic heart activity. - The fourth letter of the code is related to a permanent generator's ability to vary the heart rate. This ability is available in most current pacemakers. The possible letters are O, indicating no rate responsiveness, or R, indicating that the generator has rate modulation (i.e., the pacemaker has the ability to automatically adjust the pacing rate from moment to moment based on parameters, such as QT interval, physical activity, acid--base changes, body temperature, rate and depth of respirations, or oxygen saturation). A pacemaker with rate-responsive ability is capable of improving cardiac output during times of increased cardiac demand, such as exercise and decreasing the incidence of atrial fibrillation. All contemporary pacemakers have some type of sensor system that enables them to provide rate-adaptive pacing. - The fifth letter of the code has two different indications: (1) that the permanent generator has multisite pacing capability with the letters A (atrium), V (ventricle), D (dual), and O (none); or (2) that the pacemaker has an antitachycardia function. - Commonly, only the first three letters are used for a pacing code. An example of an NASPE-BPEG code is DVI: - D: Both the atrium and the ventricle have a pacing electrode in place. - V: The pacemaker is sensing the activity of the ventricle only. - I: The pacemaker's stimulating effect is inhibited by ventricular activity---in other words, it does not create an impulse when the pacemaker senses that the patient's ventricle is active. The pacemaker paces the atrium and then the ventricle when no ventricular activity is sensed for a period of time (the time is individually programmed into the pacemaker for each patient). A straight vertical line usually can be seen on the ECG when pacing is initiated. The line that represents pacing is called a *pacemaker spike.* The appropriate ECG complex should immediately follow the pacing spike; therefore, a P wave should follow an atrial pacing spike and a QRS complex should follow a ventricular pacing spike. Because the impulse starts in a different place than the patient's normal rhythm, the QRS complex or P wave that responds to pacing looks different from the patient's normal ECG complex. *Capture* is a term used to denote that the appropriate complex followed the pacing spike. On the top strip you see ventricular pacing: a pacemaker spike pointed to by the arrow appears before QRS. On the bottom strip you see atrial pacing: a pacemaker spike pointed to by the arrow appears before P wave -- the P wave is inverted because the impulse did not come from the SA node. The type of pacemaker generator and the settings selected depend on the patient's dysrhythmia, underlying cardiac function, and age. Pacemakers are generally set to sense and respond to intrinsic activity, which is called *on-demand pacing*. If the pacemaker is set to pace but not to sense, it is called a *fixed* or *asynchronous pacemaker;* the pacemaker paces at a constant rate, independent of the patient's intrinsic rhythm. VVI (V, paces the ventricle; V, senses ventricular activity; I, paces only if the ventricles do not depolarize) pacing causes loss of AV synchrony and atrial kick, which may cause a decrease in cardiac output and an increase in atrial distention and venous congestion. Pacemaker syndrome, causing symptoms such as chest discomfort, shortness of breath, fatigue, activity intolerance, and orthostatic hypotension, is most common with VVI pacing. Atrial pacing and dual-chamber pacing have been found to reduce the incidence of atrial fibrillation, ventricular dysfunction, and heart failure The top strip is atrial pacing, the middle is ventricular pacing and the bottom is atrioventricular pacing. Single-chamber atrial pacing (AAI) or dual-chamber pacing (DDD) is recommended over VVI in patients with sinus node dysfunction, the most common cause of bradycardias requiring a pacemaker, and a functioning AV node. AAI pacing ensures synchrony between atrial and ventricular stimulation, as long as the patient has no conduction disturbances in the AV node. Dual-chamber pacemakers are recommended as the treatment for patients with AV conduction disturbances. You can see in the bottom Biventricular paced EKG strip there are two spikes before the QRS but there is no P wave following that first spike. The top strip below you see pacer spikes without a QRS complex -- this is failure to capture In the bottom strip you see pace spikes mixed in with the patient's own rhythm -- this is failure to sense -- the pacer is competing with the patient's own rhythm. Complications associated with pacemakers relate to their presence within the body and improper functioning. In the initial hours after a temporary or permanent pacemaker is inserted, the most common complication is dislodgment of the pacing electrode. If a temporary electrode is in place, the extremity through which the catheter has been advanced is immobilized. With a permanent pacemaker, the patient is instructed initially to restrict activity on the side of the implantation. Leadless pacemakers are associated with fewer complications than transvenous pacemakers, including fewer infections, hematomas, lead dislodgement, and lead fracture. However, they provide only single-chamber RV pacing and do not feature concomitant defibrillator capabilities, limiting their usefulness. The ECG is monitored very carefully to detect pacemaker malfunction. Improper pacemaker function can arise from failure in one or more components of the pacing system listed here. It is important to know causes and considerations for each. The following data should be noted on the patient's record: model of pacemaker, type of generator, date and time of insertion, location of pulse generator, stimulation threshold, and pacer settings. This information is important for identifying normal pacemaker function and diagnosing pacemaker malfunction. The following data should be noted on the patient's record: model of pacemaker, type of generator, date and time of insertion, location of pulse generator, stimulation threshold, and pacer settings. A patient experiencing pacemaker malfunction may develop bradycardia as well as signs and symptoms of decreased cardiac output. The degree to which these symptoms become apparent depends on the severity of the malfunction, the patient's level of dependency on the pacemaker, and the patient's underlying condition. Pacemaker malfunction is diagnosed by analyzing the ECG. Manipulating the electrodes, changing the generator's settings, or replacing the pacemaker generator and/or leads may be necessary. Inhibition of permanent pacemakers or reversion to asynchronous fixed rate pacing can occur with exposure to strong electromagnetic fields (electromagnetic interference \[EMI\]). However, pacemaker technology allows patients to safely use most household electronic appliances and devices (e.g., microwave ovens, electric tools). Gas-powered engines should be turned off before working on them. Objects that contain magnets (e.g., the earpiece of a phone, large stereo speakers, jewelry) should not be near the generator for longer than a few seconds. Patients are advised to place digital cellular phones at least 6 to 12 inches away from (or on the side opposite of) the pacemaker generator and not to carry them in a shirt pocket. Large electromagnetic fields, such as those produced by magnetic resonance imaging (MRI), radio and television transmitter towers and lines, transmission power lines (not the distribution lines that bring electricity into a home), and electrical substations may cause EMI. Patients should be cautioned to avoid such situations or to simply move farther away from the area if they experience dizziness or a feeling of rapid or irregular heartbeats (palpitations). Welding and the use of a chain saw should be avoided. If such tools are used, precautionary steps such as limiting the welding current to a 60- to 130-ampere range or using electric rather than gasoline-powered chain saws are advised. In addition, the metal of the pacemaker generator may trigger store and library antitheft devices as well as airport and building security alarms; however, these alarm systems generally do not interfere with the pacemaker function. Patients should walk through them quickly and avoid standing in or near these devices for prolonged periods of time. The handheld screening devices used in airports may interfere with the pacemaker. Patients should be advised to ask security personnel to perform a hand search instead of using the handheld screening device. Patients also should be educated to wear or carry medical identification to alert personnel to the presence of the pacemaker. Remote monitoring technology is now routinely embedded in the pacemaker so that it replaces the need for frequent in-person follow-up cardiologist visits; this is also associated with improved survival. Remote monitoring allows pertinent information, such as ECG data, to be transmitted to the primary provider at the cardiology clinic. In addition, the pacemaker rate and other data concerning pacemaker function are obtained and evaluated by the cardiologist. This simplifies the diagnosis of a failing generator, reassures the patient, and improves management when the patient is physically remote from pacemaker testing facilities Because there may be a waiting period for ICD implantation, especially those postacute MI, patients who are at risk for sudden cardiac death may be prescribed a wearable vestlike automated defibrillator, which works just like an AED in that a shock is delivered less than a minute after a life-threatening rhythm is detected. Prior to the delivery of the shock, the vest vibrates and issues an alarm to announce that a shock is imminent. The battery must be changed every day and the vest must be worn at all times, even if the patient is admitted to the hospital and placed on an ECG monitor, and removed only when showering or bathing. The **implantable cardioverter defibrillator (ICD)** is an electronic device that detects and terminates life-threatening episodes of tachycardia or fibrillation, especially those that are ventricular in origin. Patients at high risk of VT or ventricular fibrillation and who would benefit from an ICD are those who have survived sudden cardiac death syndrome, which usually is caused by ventricular fibrillation, or have experienced spontaneous, symptomatic VT not due to a reversible cause. Patients with coronary artery disease who are 40 days postacute MI with moderate to severe left ventricular dysfunction (EF [\