Cardiac/Vascular Nurse Exam Secrets Study Guide (26 page)

Artificial pacemakers

Artificial pacemakers provide electrical stimulation to the cardiac muscle when the heart is not able to keep up with the demands of the body. This occurs when the intrinsic heart rate is not able to provide enough cardiac output. The artificial pacemaker is made up of a pulse generator, unipolar or bipolar lead and is implanted in the right atrium or ventricle in contact with the cardiac walls.

The types of pacemakers include permanent pacemakers and temporary pacemakers. Temporary pace makers include transvenous pacing, transcutaneous pacing, epicardial pacing, and transthoracic pacing. Other types of pacing include single chamber pacing, dual chamber pacing, rate modulating pacing, atrial overdrive pacing, and anti-tachycardia pacing.

Indications of permanent and temporary pacemakers

Permanent pacing is indicated for third-degree atrioventricular block, second-degree atrioventricular block with symptomatic bradycardia, intermittent third-degree atrioventricular block, type II second-degree atrioventricular block, sinus node dysfunction with symptomatic bradycardia or third-degree heart block, symptomatic chronotropic incompetence, persistent second-degree atrioventricular block with bilateral bundle branch, or third-degree atrioventricular block, transient advanced second or third-degree infranodal atrioventricular block and associated bundle block, ventricular tachycardia, recurrent syncope caused by carotid sinus stimulation, and symptomatic recurrent supraventricular tachycardia.

Temporary pacing is indicated for symptomatic bradycardia after acute myocardial infarction or associated hyperkalemia and/or drug toxicity, prior to permanent pacing, bradycardia nonresponsive to atropine or isoproterenol, bifascicular bundle block, alternating bundle branch block associated with acute myocardial infarction, transient right bundle block, and post-cardiovascular surgery to address bradycardia.

In transvenous pacing, vascular access is gained by percutaneous puncture of the internal jugular, subclavian, antecubital or femoral vein. Access can also be gained by venous cutdown in an antecubital vein. A bipolar, transvenous pacing lead is usually placed and maintained.

Transcutaneous pacing requires a nonsurgical approach where electrodes are attached to the anterior and posterior chest walls and connected to an external generator. This approach is typically used during emergency situations.

In epicardial pacing, surgery is done to attach leads to the atria and/or ventricle. The other end of the lead is connected externally to a generator.

In transthoracic pacing, a long needle is used to thread a lead to the right ventricle, which is then connected to an external generator. This approach is reserved for emergency situations.

Contraindications and complications of permanent and temporary pacemakers

Contraindications for implantation of pacemakers include first-degree atrioventricular block, asymptomatic second-degree atrioventricular block, transient atrioventricular block, atrioventricular block due to interior wall myocardial infarction, asymptomatic sinus node dysfunction, and suppression of ventricular tachycardia.

Complications associated with pacemaker implantation can vary depending on whether permanent or temporary pacing is being used. Complications associated with permanent pacing include pneumothorax, hemothorax, inadvertent entry into an artery, perforation of cardiac tissue or vein, damage to cardiac valve, inadequate or improper connection to leads, pain or infection in pacemaker pocket, migration of pacemaker, intravascular thrombus, bradycardia, tachycardia, endocarditis, and manual disruption of pacing.

Complications associated with temporary pacing include malfunction of the pacing system, ventricular tachycardia, thromboembolism, endocarditis, infection, phlebitis, failure to capture or sense properly, pneumothorax, hemothorax, perforation of atria, ventricle, or cardiac tissue/vessels and cardiac tamponade.

Single chamber pacing, rate modulated pacing, atrial overdrive pacing and anti-tachycardia pacing

Single chamber pacing involves either the atrium or ventricle being paced, but not both chambers in combination. However, dual chamber pacing involves both the atria and ventricles to be paced together.

Rate modulated pacing involves the pacing of the atria and ventricles based on physiological stress with increased heart rate. This type of pacing uses sensors to modulate pacing. Upon muscle or body movement, the sensor responds and modulates pacing.

Atrial overdrive pacing is a technique used to treat atrial flutter and tachycardia by providing atrial pacing rates of 200 to 500 impulses per minute.

Anti-tachycardia pacing is a technique that sends impulses to the heart to disrupt tachycardia. This approach can be used with implantable cardioverter defibrillators.

Generic pacemaker code

Pacemakers are classified using a 5-position code, which describes the different types of pacemakers and their function. Position one (I) indicates the chamber or chambers being paced. Position two (II) indicates the chamber or chambers being sensed. Position three (III) indicates the device’s response to sensing. Position four (IV) indicates the programmability and rate of modulation function. Position five (V) is only used for tachycardia functions.

Each position, I through V, has addition subsets to describe the function taking place. For example, for position III, response to sensing, O=none, T=triggered, I=Inhibited and D=dual (triggered and inhibited). In positions I and II, there will be an A (atrial), V (ventricle), or D (dual) for the chamber(s) paced and sensed.

Operating settings for pacemakers

Operational settings for pacemakers are described based on rate, output, and sensitivity. Rate is defined as the number of times per minute that the pacemaker will fire when the patient’s rate goes below that of the set rate. Output is described as the intensity of the electrical stimulus used to depolarize the cardiac tissue. Sensitivity is defined as the ability of a pacemaker to sense the patient’s intrinsic heart rate. The sensitivity of the pacemaker increases as the number decreases.

The operational settings vary based on the type of pacemaker and whether it is for permanent pacing or temporary pacing.

Follow-up required post-permanent and temporary pacemaker placement

Patients should be instructed to follow-up with their practicing clinician 1 week post permanent pacemaker placement and then follow-up every 3 to 6 months to check programming and settings of the device. Elderly patients should be checked on a regular basis for risk of infection, heart sounds, and cardiac risk factors. Patients at risk for other cardiovascular complications should be monitored on a regular basis.

Some patients may be followed via telephone for pacemaker battery status with trans-telephonic monitoring. This method of monitoring sends a telephone transmission of a rhythm strip that allows the pacemaker battery status to be measured.

Role of practicing clinician pre-, during, and post-temporary pacemaker implantation

Practicing clinicians need to understand how the pacemaker works in terms of operational settings as well as programming to be able to intervene if a problem arises.

Prior to temporary pacemaker placement, a sterile environment needs to be established. A clean insertion site needs to be established to prevent infection. Guidelines for care of central venous catheters and dressing should be followed for this procedure.

Post-temporary pacemaker placement and daily iodine cleaning of areas where leads exit the body needs to be performed. Electrical safety is necessary in the care of these patients. Practicing clinicians should always wear gloves when handling pacing and/or wiring, insulate exposed metal ends of pacing leads, keep dressing dry, and make sure all other electrical equipment in the room is grounded.

Role of the practicing clinician pre-, during, and post-permanent pacemaker implantation

Practicing clinicians need to understand how the pacemaker works in terms of operational settings as well as programming to be able to intervene if a problem arises.

Prior to permanent pacemaker implantation, practicing clinicians should take patient’s medical history, perform a physical examination, and evaluate a patient’s overall health. Patients should be screened for drug-drug interactions, allergies, vital signs such as heart rate and blood pressure and cardiovascular blood indicators such as potassium levels, prothrombin time, hematocrit, and creatinine levels. Patients should also undergo electrocardiogram and echocardiogram prior to procedure. Additionally, they should take prophylactic antibiotic therapy.

Post permanent pacemaker implantation, practicing clinicians should perform an electrocardiogram, echocardiogram, perform a physical assessment, monitor peripheral blood flow and look for swelling and evaluate cardiac pain. Hospital protocols for aftercare should be followed. Prior to patient release, practicing clinicians should perform additional physical assessment such as assess patient’s heart sounds and laboratory tests such as hematocrit, potassium levels, creatinine levels, and cardiac enzymes. Chest X-ray should also be performed pre and post pacemaker placement.

Implantable cardioverter defibrillator

Implantable cardiac defibrillators are used to treat life-threatening irregular heartbeat. They are small devices implanted in the chest or abdomen to control heart rate and cardiovascular function. The device consists of a pulse generator and lead system, which is available for pacing, sensing and shocking.

The implantation of cardiac defibrillator is very similar to that of permanent pacemakers. The transvenous lead system is inserted into the right ventricle and then connected to pulse generator. Also, a patch is connected from the ventricle to the pulse generator. However, some systems may have more than 1 lead and more than 1 patch.

Implantable cardiac defibrillators are capable of defibrillation, cardioversion, anti-tachycardia pacing, and anti-bradycardia pacing.

Implantable cardiac defibrillators are indicated for cardiac arrest due to ventricular fibrillation or ventricular tachycardia, sustained ventricular tachycardia, undetermined syncope or fainting, nonsustained and inducible ventricular tachycardia due to coronary heart disease, left ventricular dysfunction or previous myocardial infarction, hypertrophic cardiomyopathy with high risk for sudden death, and prolonged QT syndrome.

Contraindications associated with implantable cardiac defibrillators include myocardial ischemia, electrolyte abnormalities, terminal illness with short life expectancy, and ventricular tachycardia or ventricular fibrillation due to dysrhythmia.

Patients should be instructed to follow-up with their practicing clinician 1 week post implantable defibrillator placement and then follow-up every 3 to 6 months to check programming and settings of the device. Practicing clinicians should assess stored data and provide any treated episodes of dysrhythmia. Elderly patients should be checked on a regular basis for risk of infection, heart sounds, and cardiac risk factors. Other patients at risk for cardiovascular complications should be monitored on a regular basis.

Chest x-rays should be should be done annually to evaluate the implantable cardioverter. If the implantable defibrillator discharges, the patient should notify the provider. Emergency services should be contacted if the device discharges multiple times and/or the patient feels ill.

Practicing clinicians need to understand how the implantable defibrillator works in terms of operational settings as well as programming to be able to intervene if a problem arises.

Prior to implantable defibrillator placement, practicing clinicians should take the patient’s medical history, perform a physical examination, and evaluate the patient’s overall health. Patients should be screened for drug-drug interactions, allergies, vital signs such as heart rate and blood pressure and cardiovascular blood indicators such as potassium levels, prothrombin time, hematocrit, and creatinine levels. Patients should also undergo electrocardiogram and echocardiogram prior to procedure. Additionally, they should take prophylactic antibiotic therapy.

Post implantable defibrillator placement, practicing clinicians should perform an electrocardiogram, echocardiogram, perform a physical assessment, monitor peripheral blood flow and look for swelling and evaluate cardiac pain. Hospital protocols for aftercare should be followed. Prior to patient release, practicing clinicians should perform additional physical assessment such as assess the patient’s heart sounds and laboratory tests such as hematocrit, potassium levels, creatinine levels, and cardiac enzymes. Chest X-ray should also be performed pre and post implantable defibrillator placement to assess for pneumothorax.

Coronary artery bypass graft surgery

Coronary artery bypass graft surgery is a procedure that uses a vessel graft to treat ischemic areas of cardiac tissue. Surgical revascularization uses vessel grafts including internal mammary artery, saphenous vein graft, gastroepiploic artery, and radial artery.

The procedure is performed under general anesthesia and requires opening of the sternum and putting the patient on cardiopulmonary bypass while the procedure is being completed. During the procedure, the cardiac muscle is arrested using a pharmacologic agent and hypothermia.

The procedure can also be performed minimally invasively as well as without the assistance of cardiopulmonary bypass.