Early one Sunday evening, the Emergency Medical Transport Services brought Fred Smith, 48 years old, to an outlying regional medical facility. Forty-five minutes earlier, he had been driving down the highway when, as he later explained, he had suddenly lost consciousness. His truck had rolled and was totaled. Amazingly, Mr. Smith suffered no injuries worse than a few bruises and lacerations. When questioned about the accident, he said that, besides “passing out,” he couldn’t remember what had happened. His lab studies were unremarkable, ETOH and drug screens were negative. During the course of the emergency triage and continued evaluation, he was diagnosed with sick sinus syndrome. Sick sinus syndrome is characterized by sinoatrial node arrest or sinoatrial exit block, resulting in a variety of cardiac arrhythmias. Symptoms range from dizziness to unconsciousness resulting from chaotic or absent atrial activity. A cardiologist decided to insert a transvenous temporary pacer, one of the three most common pacing modalities. In this case, it was applied as a temporary measure should Mr. Smith’s heartbeat slow to less than 60 beats per minute (BPM).
Transcutaneous, transvenous, and epicardial pacing may be used as temporary treatment until the heart’s conduction system recovers. If the heart’s conduction system is no longer functional, a permanent pacer may be required. This article explains the principles and uses of temporary and permanent pulse generators. 1 Recent studies suggest that certain permanent pacers may also help patients with severe to moderate heart failure by regulating the atrial and ventricular response to the patient’s activity level, encouraging stronger and more effective heart contractions. The critical care nurse’s grasp of how and when to administer cardiac pacing is important, as a code situation is not the time to learn.
KNOW WHEN TO PACE
Most patients with symptomatic bradycardia will present with symptoms of a syncopal episode, such as dizziness or light-headedness. People who faint often fall and injure their heads. 2 When Mr. Smith arrived at the ED, the nurse was probably more concerned with the trauma than with monitoring his heart rhythm.
It’s difficult to diagnose symptomatic bradycardia when the patient is sitting or lying down, but any activity, even standing, may cause one to faint. The heart rate and stroke volume are adequate when the patient is at rest but, with activity, the heart rate doesn’t increase. This decreases perfusion to the brain, which causes the patient to become light-headed, dizzy, and sometimes faint. Other manifestations of bradycardia include chest pain, shortness of breath, and a decreased level of consciousness, all of which can progress to decreased blood pressure, shock, pulmonary congestion, and congestive heart failure.
According to the American Heart Association Guidelines for 2000, cardiac pacing (including any method of heart pacing) should be used to treat symptomatic bradycardia either when it doesn’t respond to atropine or if atropine is contraindicated. The American Heart Association further recommends cardiac pacing under the following circumstances:
Hemodynamically unstable bradycardia (less than 50 BPM)
Mobitz type II second-degree atrioventricular block (atropine may precipitate a third-degree block)
Third-degree heart block
Bilateral bundle-branch block (alternating BBB or RBBB with alternating LBBB)
Left anterior fascicular block
Newly acquired or age-indeterminate LBBB
RBBB or LBBB and first-degree atrioventricular block
Pacing is also appropriate treatment in the patient with symptomatic bradycardia who has undergone a heart transplant, as atropine is not effective in denervated hearts.
There are three ways temporary pacing can be accomplished: transcutaneously, epicardially, and transvenously.
Transcutaneous pacing (TCP) is accomplished with the use of a specially designed cardiac monitor/defibrillator (or “external pacemaker”). There are many defibrillator models, so it’s important to review the equipment prior to an emergency, to be well apprised of its functions and potential. (Not all defibrillators have pacing capabilities, particularly the older units.) The TCP pacer uses patches that adhere to the patient’s chest, which prevents the patch from slipping, important as the patient may become restless or agitated with the discomfort. The patches are applied to the patient’s bare chest at the apex of the heart and directly posterior, in a sandwich-like fashion, or anterior and lateral.
Once the patches are connected to the pacing unit, turn the unit on and activate the pacing mode, indicated on the TCP. The rate starts at 60 BPM in most units. Gradually increase the milliamperes (mA) on the dial until capture is noted on the monitor, (a pacer spike followed by a wide QRS indicates ventricular capture) and there is a palpable pulse with each captured beat (see Intermittent Ventricular Capture, above).FIGURE
It’s important to remember that TCP is not a long-term therapy. It’s a transitional or adjunct treatment for temporary use until a transvenous or permanent pacer can be inserted.
The transvenous pacer is a single-chamber pacemaker used for pacing the ventricles. (It can also pace the atrium, although it is rarely applied in this way. 3) The transvenous pacer is inserted into the right internal jugular or subclavian veins, or, less frequently, into the brachial or femoral vein. With the patient under a local anesthetic, the catheter is advanced under fluoroscopy into the right atrium or ventricle, and secured to prevent or minimize tip migration.
Pacer catheters or wires are either unipolar, with the capability of pacing in one area; or bipolar, with the capability of pacing and sensing in both the atrium and the ventricle. After insertion, the wires are connected to the pulse generator (pacer box), attached to either the atrial or ventricular output, depending on catheter location. In an emergency, the ventricle is normally paced, the pulse generator is set at the rate of 80 BPM, at 20mA, and on asynchronous mode. Otherwise, check the pacer thresholds (the number of mAs required to capture the ventricle) and set at two to three times the initial capture. The rate is set according to the patient’s intrinsic rate.
Mr. Smith was placed on ventricular demand (VVI) (See chart for pacer coding) because of his bradycardiac episodes during periods of normal sinus rhythm. In checking the threshold, the rate was set at 80 BPM, ten beats above his intrinsic rate of 70 BPM, the mode was placed in asynchronous pacing, and then gradually increased until capture was obtained at 100%. Once 100% capture was obtained, the mA level was turned down until capture was lost (indicated on the monitor by a pacer spike without QRS following). The mA was turned up until 100% capture was regained: the point of threshold. Then the rate was decreased to 60 BPM, set on demand or sensitivity of 1mV, and the mAs were set two times above threshold to provide a safety margin.
Mr. Smith tolerated the procedure well. He was taken to a cardiac center, and admitted to the Coronary Care Unit (CCU) for close observation. While in the CCU, Mr. Smith’s cardiac arrhythmias continued with runs of atrial tachycardia followed by bradycardiac episodes, which are common during this phase. The cardiologist conducted electrophysiology studies (EPS), which showed no consistent inducible tachycardia. As a result, Mr. Smith had a dual-chamber DDD permanent pacer inserted that afternoon. (See Pacing Standardization, page 12.) The DDD ensures that the pacer will sense when Mr. Smith’s heartbeat falls below 60 BPM, and the DDD will take over when this occurs. The procedure is relatively simple, and Mr. Smith was able to go home the next day. In Mr. Smith’s case, the transvenous pacer was used as a transition to a permanent pacer.TABLE
Epicardial pacing is similar to transvenous pacing except for placement and the use of unipolar wires. After heart surgery for coronary artery bypass grafting (CABG), or after valve surgery (repair or replacement), the surgeon places two epicardial wires on the right atrium, and two wires on the right ventricle. The wires are brought out through the chest wall and sutured to the skin. Pacing is accomplished with the same pulse generator used in transvenous pacing. It’s important to remember that epicardial wires, if not in use, should be placed in glove tips, secured to the patient’s chest with tape, and labeled. Accidental or even purposeful removal of the wires can result in cardiac tamponade. After removal of the pacer wires, the client should be on bed rest for one hour and vital signs monitored closely (or per hospital protocol).
Permanent pacers are inserted via the left subclavian vein and advanced through the right atrium with the catheter tip secured at the apex of the right ventricle. Most permanent pacers have dual-chamber DDD capabilities, able to sense and pace both in the atrium and ventricle. The pulse generator is placed in the upper portion of the left chest and is secured under the skin, through which the outline of the pacer may be felt and sometimes seen. Again, the procedure is done with a local anesthetic and under fluoroscopy.
Nursing intervention for permanent pacers is less demanding than it is for temporary pacers. A nurse is responsible for cardiac monitoring, obtaining vital signs after the procedure, and for watching for hemorrhage or edema at the site. The patient’s left arm may be secured in a sling to prevent catheter migration. As with other pacing modalities, educating the patient and family is essential to a successful outcome.
THE BEAT GOES ON: PACEMAKERS AND HEART FAILURE
Clinical heart failure is the heart’s inability to pump enough blood to meet the body’s requirements, and DDD pacemakers have recently been used for treatment. If clinical heart failure is caused by arrhythmia, biventricular pacing may lead to improved patient outcome. 4
The New York Heart Association’s classification system for heart failure is as follows:
Research studies are underway to determine the effectiveness of DDD pacing in Class III and IV heart failure. The atrial kick of the DDD pacer accounts for 15% to 25% of cardiac output and also confers chronotropic advantages, such as stimulation of the heart rate in response to increased activity.
Nursing interventions for a patient with a DDD pacer and heart failure include:4
Monitor heart rate and rhythm, assess capture and sense of pacemaker.
Monitor patient’s vital signs to provide a baseline and note trends in a timely manner.
Assess the insertion site for bleeding. The use of a sling may be indicated.
Assess heart sounds to provide baseline. Prior to pacer insertion, patients may have S1, S2, S3, and, probably, S4 heart sounds. After the pacer is inserted and operating, abnormal heart sounds should occur less frequently.
Assess rate, ease, and regularity of respiration, lung sounds, the presence of a cough, and sputum production. This establishes baseline of the treatment’s effectiveness, and determines if the heart failure is worsening.
Assess the patient’s level of consciousness. A deterioration in status may indicate worsening oxygenation status or a decrease in cardiac output.
Assess for jugular neck vein distention, liver enlargement, and peripheral or trunk edema. Establish baseline to determine early changes and potential worsening of heart failure status.
Assess skin color, temperature, moistness, and peripheral pulses. Again, baseline data will provide information for early detection of changes in cardiac and respiratory status.
Monitor intake and output, including daily weights. Monitor hemodynamic parameters as ordered. Review labs, electrolytes and blood urea nitrogen and creatinine to assess kidney function. Monitor blood potassium to maintain a normal level, especially if the patient is taking diuretics. Monitor complete blood cell (CBC) counts, as anemia could cause cardiac and respiratory compromise.
Monitor bowel function, because strain may cause a decrease in cardiac output and a syncopal episode. A daily laxative may help in this instance.
Assess the need for antiembolism stockings, which may be necessary for the inert patient on bed rest. Teach the bedbound patient leg and foot exercises, and explain that pain and cramping in the lower legs must be reported immediately to the physician. These areas must not be massaged as it could cause a dislodging of potential thrombi.
Administer medications as ordered; oxygen therapy may be initiated depending on patient status.
Provide emotional support and instruction to the patient and his family. Give information on heart failure support groups and encourage questions.
Keep the physician updated on patient status, and report any abnormal findings immediately.
Nursing interventions for the transcutaneous pacer
Check capture by palpating the patient’s femoral pulse. Muscle innervation at the patch side may cause a pseudopulse and be mistaken for capture.
Assess perfusion by monitoring blood pressure, heart rate, and level of consciousness.
Administer sedation and analgesia as necessary for the patient’s comfort.
Maintain bed rest with close monitoring.
Educate the patient and family about the device.
Nursing interventions for transvenous pacing
Check the monitor for capture and assess vital signs. Patients with transvenous pacers may be pacer-dependent, so it’s important to monitor them closely, checking vital signs frequently.
Secure insertion site properly according to hospital protocol and evaluate it for hemorrhage, edema, or infection. The nurse should note markings on the catheter for placement. It's the physician's responsibility to manipulate the cathether.
Equip the pulse generator with a new battery for each patient.
Check thresholds at least once a shift, or per hospital protocol.
Administer sedation and analgesia as needed for insertion. Make sure the patient is on bed rest, although he may be allowed to sit up in the chair depending on acuity.
Educate patient and family about the device.