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•Explain that the patient may be hospitalized for 24 to 48 hours to monitor his heart rhythm.
•Provide pacemaker teaching if the patient had a pacemaker inserted. (For more information about pacemaker teaching, see “What to teach the patient,” page 190.)
A look at ICDs
An implantable cardioverter-defibrillator (ICD) is an electronic device implanted in the body to provide continuous monitoring of the heart for bradycardia, ventricular tachycardia, and ventricular fibrillation. The device then administers either paced beats or shocks to treat the dangerous arrhythmia. In general, ICDs are indicated for patients for whom drug therapy, surgery, or catheter ablation has failed to prevent the arrhythmia.
The procedure for ICD insertion is similar to that of a permanent pacemaker and may be inserted in a cardiac catheterization or electrophysiology laboratory. Occasionally, a patient who requires other cardiac surgery, such as coronary artery bypass, may have the device implanted in the operating room.
What it is
An ICD consists of a programmable pulse generator and one or more leadwires. The pulse generator is a small battery-powered computer that monitors the heart’s electrical signals and delivers electrical therapy when it identifies an abnormal rhythm. The leads are insulated wires that carry the heart’s signal to the pulse generator and deliver the electrical energy from the pulse generator to the heart.
Storing and retrieving information
An ICD also stores information about the heart’s activity before, during, and after an arrhythmia, along with tracking which treatment was delivered and the outcome of that treatment. Devices also store electrograms (electrical tracings similar to ECGs). With an interrogation device, a practitioner or technician can retrieve this information to evaluate ICD function and battery status and to adjust ICD system settings.
Automatic response
Today’s advanced devices can detect a wide range of arrhythmias and automatically respond with the appropriate therapy, such as bradycardia pacing (both singleand dual-chamber), antitachycardia pacing, cardioversion, and defibrillation. ICDs that provide
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Types of ICD therapies
Implantable cardioverter-defibrillators (ICDs) can deliver a range of therapies depending on the arrhythmia detected and how the device is programmed. Therapies include antitachycardia pacing, cardioversion, defibrillation, and bradycardia pacing.
Therapy |
Description |
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Antitachycardia |
A short series of rapid, electrical pacing pulses are used to |
pacing |
interrupt ventricular tachycardia (VT) and return the heart to |
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its normal rhythm. |
Cardioversion |
A lowor high-energy shock (up to 35 joules) is timed to the |
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R wave to terminate VT and return the heart to its normal |
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rhythm. |
Defibrillation |
A high-energy shock (up to 35 joules) to the heart is used to |
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terminate ventricular fibrillation and return the heart to its |
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normal rhythm. |
Bradycardia pacing |
Electrical pacing pulses are used when the heart’s natural |
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electrical signals are too slow. ICD systems can pace one |
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ventricle (VVI pacing) of the heart at a preset rate. Some sys- |
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tems will sense and pace both chambers (DDD pacing). |
therapy for atrial arrhythmias, such as atrial fibrillation, are also available. (See Types of ICD therapies.)
How it’s programmed
When caring for a patient with an ICD, it’s important to know how the device is programmed. This information is available through a status report that can be obtained and printed when the practitioner or specially trained technician interrogates the device. This involves placing a specialized piece of equipment over the implanted pulse generator to retrieve pacing function. If the patient experiences an arrhythmia or the ICD delivers a therapy, the program information recorded helps to evaluate the functioning of the device.
Program information includes:
•type and model of the ICD
•status of the device (on or off)
A tiny computer in the ICD tracks information before, during, and after an arrhythmia.
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•detection rates
•therapies that will be delivered: bradycardia pacing, antitachycardia pacing, cardioversion, and defibrillation.
Arresting developments
Follow these guidelines if your patient experiences an arrhythmia:
•If the patient experiences cardiac arrest, initiate cardiopulmonary resuscitation (CPR) and advanced cardiac life support.
•If the ICD delivers a shock while you’re performing chest compressions, you may also feel a slight shock. Wear gloves to prevent shock.
•Externally defibrillating the patient is safe as long as the paddles aren’t placed directly over the pulse generator. The anteroposterior paddle position is preferred.
Be alert
•Watch for signs of a perforated ventricle, with resultant cardiac tamponade. Ominous signs include persistent hiccups, distant heart sounds, pulsus paradoxus, hypotension accompanied by narrow pulse pressure, increased venous pressure, distended jugular veins, cyanosis, decreased urine output, restlessness, and complaints of fullness in the chest. Report any of these signs immediately to the practitioner and prepare the patient for emergency surgery.
•Assess the area around the incision and report swelling, tenderness, drainage, redness, unusual warmth, or hematoma.
What to teach the patient
•Explain to the patient and his family why an ICD is needed, how it works, potential complications, and what they can expect. Make sure they also understand ICD terminology.
•Discuss signs and symptoms to report to the practitioner immediately.
•Advise the patient to wear a medical identification bracelet indicating ICD placement.
•Educate family members in emergency techniques (such as dialing 911 and performing CPR) in case the device fails.
•Explain that electrical or electronic devices may cause disruption of the device.
•Warn the patient to avoid placing excessive pressure over the insertion site or moving or jerking the area until the postoperative visit.
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Quick quiz
1. When using a transcutaneous temporary pacemaker, the energy level should be set at:
A.the highest milliampere setting the patient can tolerate.
B.the lowest milliampere setting that ensures capture of the myocardium.
C.a milliampere setting midway between the setting that causes capture of the myocardium and the setting at which symptoms first appear.
D.the milliampere setting that provides a heart rate of 80 beats per minute.
Answer: B. Select the lowest milliampere setting that causes capture of the myocardium. Higher energy levels will be too irritating for the patient.
2.Failure to capture is represented on the ECG as:
A.no pacemaker activity.
B.spikes where they shouldn’t be.
C.a spike on a T wave.
D.a spike without a complex.
Answer: D. A spike without a complex indicates the pacemaker’s inability to capture or stimulate the chamber.
3. The first letter in the five-letter coding system for pacemakers identifies the:
A.chamber in which the pacemaker senses intrinsic activity.
B.heart chamber being paced.
C.pacemaker’s response to the intrinsic electrical activity.
D.pacemaker’s response to a tachyarrhythmia.
Answer: B. The first letter identifies the heart chamber being paced, the second letter signifies the heart chamber that senses intrinsic activity, the third letter shows the pacemaker’s response to that activity, the fourth letter describes the rate modulation, and the fifth letter shows the location or absence of multisite pacing.
4. A patient with a biventricular pacemaker will have which lead configuration?
A.A lead in both ventricles only
B.A lead in each atria and each ventricle
C.A lead in the right atrium and each ventricle
D.A lead in both atria and the left ventricle
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Scoring
If you answered all seven questions correctly, all right! You’ve taken the lead when it comes to nonpharmacologic treatment methods.
If you answered six questions correctly, terrific! Keep up the good pace.
If you answered fewer than six questions correctly, no sweat. Go with your impulse to reread the chapter and you’re sure to do better next time.