Learning Objectives
By the end of this section, you will be able to:
- Discuss the anatomical and physiological functions of the cardiac electrical system
- Discuss and compare pathophysiology, clinical manifestations, and nursing care of bradycardic and tachycardic dysrhythmias
- Discuss and compare pathophysiology, clinical manifestations, and nursing care of ectopic beats
- Discuss and compare pathophysiology, clinical manifestations, and nursing care of heart blocks
- Discuss and compare pathophysiology, clinical manifestations, and nursing care of atrial fibrillation and atrial flutter
- Discuss and compare pathophysiology, clinical manifestations, and nursing care of ventricular tachycardia and ventricular fibrillation
- Discuss and compare pathophysiology, clinical manifestations, and nursing care of asystole
- Evaluate the nursing care of the patient with dysrhythmia
Cardiac myocytes require coronary perfusion for contractility. Concepts for disturbances in cardiac rhythms centralize around the ability of cardiac myocytes to conduct electricity, which assist the atrial and ventricular contraction. If there is a defect in the cardiac electrical conduction system, it leads to contractility problems. Figure 12.4 summarizes the conduction system of the heart.
When a patient has dysrhythmia, the normal cardiac conduction process is interrupted. Two mechanisms are occurring and not in synchronicity. As the right and left ventricles fill with blood, the atria contract to inject blood into those respective ventricular chambers (diastole). Once the ventricles are adequately filled, the tricuspid and mitral valves open, the semilunar valves close, and blood is pushed from the ventricles into the lungs and systemic circulation (systole). Continuous cardiac telemetry analysis was not introduced into the acute care setting until the 1960s, reserved for higher levels of care such as intensive care units (Chen et al., 2018). With this advancement in technology, close monitoring of patients experiencing dysrhythmias was more possible. However, to fully understand dysrhythmia identification, intervention, and nursing care, the nurse needs to understand rhythm analysis.
Rhythm Interpretation
The normal sinus rhythm, or the rhythm that originates from the sinus node and describes the characteristic rhythm in the healthy human heart, includes several features (Figure 12.5). The first small, round hill observed is called the P wave. The P wave represents electrical depolarization, or the channeled travel of electricity, in the atria, whereas the QRS complex, a jagged triangular shape, represents electrical current traveling through the ventricle. An atrial depolarization is represented by the interval between the P wave and the R wave in the QRS complex; this is a measurement of the time needed for electricity to travel from the atria to the ventricles. Normal criteria for the PR interval are 0.16 to 0.20 seconds. A ventricular depolarization is the measurement of the time electricity travels through the ventricles to conduct a ventricular contraction and is represented by the QRS complex. It is shorter in duration compared to the PR interval, less than 0.12 seconds. Figure 12.5 summarizes these times.
To capture measurements of these electrical travel times, a nurse may use calipers to measure the distance between the P wave and the R wave or the space in the QRS complex (Figure 12.6). However, the most common method used is measuring boxes in a telemetry strip. It is important to note that in each large box are five small boxes. Each small box represents 0.04 seconds, and each large box represents 0.20 seconds.
In addition to normal measurements for the PR and size of the QRS complexes, regularity and rate must be established. A 6-second strip is required to determine these features. The nurse must “march out” with calipers or by tracing the P-to-P waves to evaluate regularity, or whether beats are occurring at regular intervals. One comparison would be the regular tempo of music: is it regular and is the beat predictable? The same applies to cardiac conduction. If there is regularity between the P-to-P waves and R-to-R waves, this is deemed a regular rhythm.
The second measurement is the heart rate, which normally falls between 60-100 beats per minute (bpm) (Table 12.1). The fastest method to obtain heart rate is to count the number of QRS complexes in a 6-second strip and multiply that number by ten. For instance, if the nurse counts seven QRS complexes in a 6-second strip, the ventricular rate is approximately 70 beats a minute. For a more accurate assessment of heart rate, the nurse can count the number of large or small boxes occurring between the R-to-R complexes if regularity has been established. Once the number of small boxes or large boxes have been determined, the constant used for division is 300 seconds ÷ number of large boxes or 1500 seconds ÷ number of small boxes. For instance, if the nurse counts 20 small boxes from the R-to-R interval, 1500 seconds ÷ 20 small boxes will yield a heart rate of 75 beats.
| Cardiac Rhythm Component | Description | Normal Interval |
|---|---|---|
| P wave duration | Time for atrial depolarization | 0.06–0.12 seconds |
| PR interval | Time from the start of atrial depolarization to the start of ventricular depolarization | 0.12–0.20 seconds |
| QRS duration | Time for ventricular depolarization | 0.06–0.10 seconds Greater than 0.12 seconds is considered abnormal and “wide” |
| QT interval | Time from the start of ventricular depolarization to the end of ventricular repolarization | 0.36–0.44 seconds |
| ST segment | Period between the end of ventricular depolarization and the start of ventricular repolarization | Typically isoelectric (flat) |
| T wave duration | Time for ventricular repolarization | Variable; typically follows the ST segment |
| RR interval | Time between successive R-wave peaks | Variable; dependent on heart rate |
| Heart rate (HR) | Derived from RR interval; the number of beats per minute | 60-100 beats per minute (BPM) |
Clinical Safety and Procedures (QSEN)
Safety: Telemetry Monitoring
Definition: Reducing the risk of patient harm through effective system and individual action.
Knowledge: Identify the benefits and limits of safety-enhancing technologies (e.g., barcodes, Computer Provider Order Entry, medication pumps, and automatic alerts/alarms).
Skill: Effectively use technology and standardized practices that promote safety and quality. To demonstrate competence, the nurse will:
- Follow institutional practices for the use of telemetry monitoring, which may include:
- Setting and maintaining alarms per policy and order
- Using alternative devices (such as wireless monitors) for ambulation or transportation for patients unable to be removed from monitor
- Carrying a pager or device on your person to receive alerts
- Physically assessing the patient’s status and apical heart rate in response to alerts
Attitude: Understand and appreciate how standardization and reliability contribute to safety.
(QSEN Institute, n.d.)
Bradycardic and Tachycardic Dysrhythmias: Clinical Manifestations and Nursing Care
Normal heart rates are 60 to 100 beats per minute (bpm). There are normal fluctuations in heart rate, including lower heart rates with relaxation, medication, and during sleep. During peaks of productivity, exercise, or even illness, such as infection, the heart rate may increase.
Bradycardic rhythms are rates less than 60 bpm (Figure 12.7). Features of sinus bradycardia are a rate less than 60 bpm, with regular PR and QRS intervals.
Sinus bradycardia may occur due to medications, such as beta-blockers, digoxin, or opioids, or increasing vagal tone from bearing down. Patients may be asymptomatic, or report fatigue, dizziness, or weaknesses. For cues to be recognized, it is imperative for the nurse to inquire about the patient’s level of activity. In some patients, a resting heart rate of less than 60 bpm may be a clinical finding in an active runner. Nursing interventions for symptomatic patients include holding cardiac medications if pulse is less than 60 bpm (alert the provider), having the patient stay in bed as the patient may be lightheaded or dizzy, and continuing to monitor the patient. The provider may also order medications to raise the heart rate (such as atropine) or initiate transcutaneous pacing, a noninvasive procedure that uses electrical impulses to temporarily pace a patient’s heart.
Link to Learning
Atropine is an anticholinergic that can be administered intravenously to correct symptomatic bradycardia. Side effects include decreased gastric secretions, drying of mucus membranes, and increased esophageal sphincter tone. Read more about atropine at StatPearls.
In contrast, tachycardic rhythms are rates greater than 100 bpm (Figure 12.8). Features of sinus tachycardia are a rate greater than 100 bpm with regular PR and QRS intervals.
Factors contributing to tachycardia may include stress, dehydration, fever, exercise, caffeine, or illegal substances such as cocaine or stimulants. Clinical manifestations may include shortness of breath, anxiety, fluttering, flushed face, or dizziness, but the patient may also be asymptomatic. Interventions include rest, fluids, treatment of the underlying cause, medications, such as beta blockers, and monitoring hemodynamics.
Ectopic Beats: Clinical Manifestations and Nursing Care
An occasional, singular, irregular beat, also known as an ectopic beat, may originate from the atria or the ventricles (Figure 12.9). Atrial ectopic beats will cause an early, irregular occurrence of P and QRS waves; this is called a premature atrial contraction (PAC). In contrast, a premature ventricular contraction (PVC) is when a ventricular ectopic beat appears without a P wave and widens the appearance of the QRS. If there are frequently occurring ventricular beats that all look the same, they are unifocal, or uniform; if they look different, they are multifocal, or multiform.
A compensatory pause after a PVC occurs as the heart’s natural response to the early, irregular beat; this pause allows the heart to reset its rhythm and ensures that the subsequent beat falls in line with the normal rhythm, thereby helping to maintain overall cardiac rhythm stability. A non-compensatory pause following a PAC occurs because the premature beat disrupts the regular cardiac cycle, causing a brief interruption in the normal rhythm without a full reset of the heart, which results in a shorter pause before the next beat compared to a compensatory pause.
The frequency of the ectopic beat may vary. An ectopic beat occurring on every other beat is bigeminy; an ectopic beat occurring on every third beat is trigeminy. When there are more than three PVCs in a row, this is called a run of ventricular tachycardia, which is a potentially life-threatening cardiac dysrhythmia that occurs when the lower chambers of the heart beat too fast to pump well.
Ectopic beats may be triggered by drugs, caffeine, alcohol, stress, electrolyte disturbance, or certain medications. Patients may experience few to no symptoms with occasional ectopic beats. However, ectopic beats that occur more frequently will cause symptoms. Clinical manifestations include subjective complaints of dizziness, palpitations, fluttering in the chest, adjusting of heart rate, or chest pain. Nursing interventions include having the patient remain calm and do some deep breathing, administering cardiac medications/electrolyte replacement as ordered, and monitoring the patient’s vital signs. It may be necessary to check laboratory values to assess for abnormal potassium, calcium, or magnesium levels. The patient should be instructed to avoid caffeine and alcohol, as these may trigger more ectopic beats.
Read the Electronic Health Record
Laboratory Values
| Glucose | BUN | Creatinine | Sodium | Potassium | Chloride | Carbon Dioxide | Magnesium |
|---|---|---|---|---|---|---|---|
| 98 | 18 | 0.92 | 138 | 3.1 | 104 | 36 | 1.4 |
Heart Blocks: Clinical Manifestations and Nursing Care
Another commonly occurring dysrhythmia is heart block, in which there is an impulse interruption between the atria and ventricles, called an atrioventricular (AV) block, or heart block. There are three types of heart block: first-degree heart block (Figure 12.10); second-degree, further broken down into Type I and Type II; and third-degree heart block. In first-degree heart block, the PR interval is consistently greater than 0.20 seconds (Table 12.1), while QRS is normal and regular. Patients are often asymptomatic, and it is often found incidentally. First-degree heart block may be due to medications, increased vagal tone, or family heart disease. It is the nurse’s responsibility to monitor for worsening symptoms. However, most patients live with first-degree heart block without complication.
Second-degree heart block is further broken down into two parts: Type I (also known as Mobitz I or Wenckeback) and Type II (Mobitz II) (Figure 12.11). With Mobitz I second-degree heart block, the classic features are a PR interval that gets longer with each beat until a QRS is dropped, and the pattern repeats. In contrast, in Mobitz II second-degree heart block, the PR interval is constant, and some of the QRSs are blocked. This does not occur in a pattern like Mobitz I. Mobitz II heart block is more serious and can potentially lead to third-degree heart block. With Mobitz I, the patient may be asymptomatic. Other complaints, more consistently, from Mobitz II, are dizziness, fatigue, chest pain, shortness of breath, or the subjective feeling of a skipped beat. Typical causes of second-degree heart block may be medications, underlying heart disease, or an aging conduction system.
Nursing responsibilities include telemetry monitoring, trending the blood pressure, or if the patient becomes more symptomatic (for example, becomes hypotensive, complains of increased chest pain or dizziness), administering an anticholinergic such as atropine to transiently raise the heart rate. The patient may require transcutaneous pacing and be prepared for surgery for a pacemaker, a small implantable machine with a battery life of approximately ten years that recognizes when the heart rate is too fast or too slow and will pace the rhythm to a preset range (e.g., a heart rate of 60 to 70 bpm) to meet perfusion needs (Figure 12.12). Patients with pacemakers must be instructed to carry a card for passage through metal detectors and to avoid direct exposure to microwaves as these appliances can compromise the device’s battery. The presence of a pacemaker should be identified for safety with MRI.
A third-degree heart block is the most serious heart block as there is a loss of electrical impulses between the atria and the ventricles (Figure 12.13). In essence, the ventricles must beat independently to maintain cardiac output. In contrast to myocyte contractility rates in the atria, the ventricular tissue has a slower impulse control with a rate of 20 to 40 bpm. P-P and R-R intervals are variable. Atrial and ventricular rates will differ drastically. Also, the QRS interval is wide, greater than 0.12 seconds. The patient will report feeling lightheaded, dizziness, fatigue, chest pain, or may have a syncopal episode and hypotension.
Third-degree heart block requires quick intervention. Nurses must apply telemetry to the patient and prepare for transcutaneous pacing, assess oxygenation, check labs to alert the provider if there are any electrolyte shifts (potassium or magnesium), maintain bed rest, and hold antiarrhythmics/beta blockers. Patients will require a pacemaker.
Atrial Dysrhythmias: Clinical Manifestations and Nursing Care
The most common rhythm disturbances occur in the atrial tissue. A popular umbrella term utilized to discuss rhythm disturbances that occur above the ventricles is supraventricular tachycardia (SVT) (Figure 12.14). The most common forms of SVT are atrial fibrillation (AFib) and atrial flutter. AFib is an irregular, fast rhythm originating from the atria due to multiple impulses being fired. The CDC (2022) predicts that by 2030, 12.1 million people in the United States will have AFib. The telemetry qualifiers are regularly irregular, the PR interval is indeterminate due to the irregularity, and the QRS interval is less than 0.12 seconds. AFib is considered rate controlled if the rate is between 60 and 100 bpm, or rapid when rates consistently climb over 100 bpm.
An atrial flutter (A flutter) is an atrial dysrhythmia related to AFib (Figure 12.15). It is a regular but tachycardic rhythm caused by electrical re-entry in the right atrial circuity. The classic “saw tooth pattern” is one of the hallmark features. The PR interval is indeterminate, the QRS interval is less < 0.12, and it is regular. A flutter rates may be 240 to 300 bpm.
The clinical manifestations of AFib and A flutter are very similar in nature; therefore, it is difficult to isolate which dysrhythmia is occurring based on symptom presentation only. Patients will report fluttering sensations, chest pain, palpitations, and dizziness, and may experience hypotension. The faster the tachycardia, the more severe the patient’s symptoms will be.
Nurses must assess and evaluate the need for additional oxygenation support and monitor telemetry and vital signs. The patient may need to refrain from eating to prepare for cardioversion (a procedure performed by a machine or medicine that restores a normal heart rhythm when the heart is beating too fast or irregularly) or ablation (a procedure that creates scars in the heart tissue which block the abnormal electrical impulses to help the heart maintain a normal rhythm). First-line therapies lean towards pharmacological therapies, which include digoxin, beta-blockers, amiodarone (cardiac glycosides), and calcium channel blockers (CCBs). Other concurrent therapies considered are anticoagulants for atrial dysrhythmias. Patients with comorbid congestive heart failure, hypertension, age over 65, stroke and diabetes, and AFib would require anticoagulation with heparin, warfarin, or the new oral anticoagulants (NOACs).
Clinical Safety and Procedures (QSEN)
Safety: Preparing the Patient for Cardioversion
In events where the patient’s atrial dysrhythmia is non-responsive to pharmacological therapies, cardioversion is a procedure in which electricity is utilized to shock the atrial circuitry back to normal sinus rhythm. The dose of electricity varies by patient and provider preference; it may be as little as 50 joules to up to 100 to 150 joules.
- The patient must be nothing by mouth (NPO) as monitored anesthesia care (MAC) is required, and to mitigate the risk of aspiration, the patient is advised to not have any solids before the procedure.
- Prior to cardioversion, a transesophageal echocardiogram will be performed to isolate any possible blood clots that may be hiding in the atrial appendage. This diagnostic test is necessary because if there is an isolated blood clot and the patient is cardioverted, the clot can be expelled to the brain or lungs, risking a cerebrovascular accident or pulmonary embolism.
- The nurse must ensure that the transcutaneous pads are connected correctly and that the defibrillator is turned to the “cardioversion” setting. The cardioverter will synchronize the shock delivery with the patient’s QRS on their EKG rhythm. (Delivery of an unsynchronized shock risks sending the patient into cardiac arrest.)
- After the delivery of the provider-ordered electricity, the nurse will monitor the patient’s response to the cardioversion and note if the patient returned to a normal sinus rhythm.
- Post-procedure, the patient will be monitored for a period of two hours, noting hemodynamics, rhythm response, and the patient’s response to monitored anesthesia care.
Ventricular Dysrhythmias: Clinical Manifestations and Nursing Care
Ventricular disturbances are the most serious dysrhythmias and require prompt, emergent intervention. A ventricular tachycardia is when the ventricle beats rapidly at 150 to 200 bpm with wide QRS complexes (greater than 0.12 seconds) and no discernible PRs or P waves (Figure 12.16). A ventricular fibrillation is slightly faster than ventricular tachycardia with rates over 200 bpm (Figure 12.17). A classic finding in ventricular fibrillation is a chaotic baseline with no discernible QRS, PRs, or P waves. Patients with ventricular tachycardia may be able to report subjective feelings of fluttering, fatigue, and near syncope. The patient will be diaphoretic and have weak pulses. In severe cases, they can lose perfusion and have syncope. Ventricular fibrillation is considered a cardiac arrest as patients will lose consciousness and require advanced cardiac life support. Causation of these dysrhythmias can be from myocardial infarction, heart failure, electrolyte disturbance, illegal substance abuse, shock, or medications.
The nurse must act quickly when ventricular tachycardia or ventricular fibrillation is occurring and recruit assistance as outcomes of survival increase with prompt intervention. Nursing actions include performing high-quality cardiopulmonary resuscitation (CPR) for pulseless ventricular tachycardia and pulseless ventricular fibrillation, utilizing an automated external defibrillator, and providing oxygen. When a pulse is present, only other restoration methods can be used. Restoration of perfusion is a team approach and requires health professionals to provide CPR, defibrillation, and oxygen, and to administer emergency medications (e.g., epinephrine, amiodarone, calcium gluconate). Once hemodynamic stability has been achieved, nursing interventions center around patient monitoring, laboratory trending, and implementing a clinical plan dependent on the cause.
Clinical Safety and Procedures (QSEN)
Safety: Interventions with CPR and the Defibrillator for Ventricular Fibrillation
- The code team is activated per institutional policy.
- High-quality CPR with a compression rate of 100 to 120 compressions per minute (note there is a full recoil of the chest at a depth of two inches). It is of utmost importance to step out after five cycles (two minutes) of CPR as rescuers may experience fatigue. This safety “tap out” is necessary to continue high-quality CPR until the return of spontaneous circulation.
- The AED is retrieved, and pads are placed to initiate a dose of electricity. The machine will determine if a shock is advised and will prompt all rescuers to step away to avoid being shocked.
- A team member begins bagging the patient with bag valve mask of 100% oxygen.
- Medications may be administered during resuscitative efforts such as epinephrine, amiodarone, and lidocaine.
- Assess for a carotid pulse and resume CPR if no pulse is palpated.
- The longer the delay to high-quality CPR, the higher the mortality rate. To maximize outcomes, initial intervention should occur within the first three minutes of a witnessed cardiac arrest. In an acute care setting, members from the intensive care unit, emergency room, and respiratory therapy will assist in rescuing interventions. When the code team arrives, they will initiate advanced cardiovascular life-support (ACLS) following the protocol set forth by the American Heart Association.
Asystole
Lastly, there is asystole, also known as ventricular standstill, or “flatline” (Figure 12.18) (Jordan et al., 2024). Cardiac activity ceases to occur due to termination of electrical conduction. Clinical signs of asystole are determined by the rhythm showing a flat line with little to no evidence of cardiac rhythm.
The mortality of asystole is approximately 90 percent (Khosla et al., 2024), with long term complications of brain death and high-demand needs for artificial life support. Asystole is often linked to unsuccessful attempts to correct bradycardia dysrhythmias, ventricular dysrhythmias, or pulseless electrical activity (Jordan et al., 2024). Like the presentation of ventricular fibrillation, the patient will be unconscious, with no evidence of breathing, weak pulses, and a low blood pressure that is unable to support cardiac physiological demands. Nursing actions align with a team member’s roles in attempts to restore spontaneous circulation, performing high-quality CPR, administration of epinephrine, and airway protection with intubation or bag-mask ventilation. The advanced cardiovascular life-support providers will then attempt to determine the cause of the asystole by investigating the “Hs and Ts.”
Link to Learning
Advanced cardiovascular life-support providers investigate the “Hs and Ts” which are the twelve reversible causes of life-threatening dysrhythmias.
Evaluation of Nursing Care of the Patient with Dysrhythmia
Depending on the patient’s dysrhythmia, stabilization of cardiac perfusion is a key component through normalization of heart rate and blood pressure. The patient’s oxygenation will improve following stabilization of the dysrhythmia as evidenced by oxygen saturations greater than 92 percent and reduced complaints of shortness of breath. The patient’s energy level will improve as evidenced by the ability to participate in self-care activities. Lifestyle modifications (e.g., smoking cessation, altered diet, weight management) and compliance with pharmacological therapies can control or minimize the effects of dysrhythmia. The patient’s educational needs will vary depending on medical therapy and verbalized understanding of the condition, treatment, and interventions initiated (e.g., if the patient had a pacemaker).
Dysrhythmia management may pose challenges, as telemetry analysis is a skill that takes time to learn. Over time, the nurse will become more proficient and confident in the ability to identify and intervene when a dysrhythmia is observed. Acute care settings with cardiovascular specialty or medical-surgical units with a high level of care have institutional mentorship and programs to assist new nurses with skill mastery. The baseline of a strong foundational understanding of cardiovascular electrical physiology will assist the nurse with matching the dysrhythmia to symptom presentation.
Interdisciplinary Plan of Care
Roles and Responsibilities of Pertinent Team Members During Cardiac Arrest
- Respiratory therapy: Respiratory therapists assist manually ventilating patients with a bag valve mask and assisting anesthesia or the health-care provider with intubation.
- Physicians/health-care providers: Providers typically take lead roles in ordering pharmacological interventions or diagnostics during cardiac arrest.
- Nursing: Nursing roles are diverse in the administration of emergency medications, recording the events of the cardiac arrest, and performing CPR.
- Pharmacists: Pharmacists will ensure doses and frequency of pharmacological therapies are safe and alignment with Advance Cardiovascular Life Support (ACLS) algorithms.
- Chaplain/social work: Religious and social support have become more popular in extending spiritual and emotional support to the patient’s loved ones.