Supraventricular tachycardia (SVT) is an arrhythmia initiated above the ventricles, at or above the atrioventricular (AV) node. This cardiac rhythm occurs due to improper electrical conduction within the heart that disrupts the coordination of heartbeats. Early beats occur within the atria of the heart due to improperly functioning electrical connections, resulting in a rapid heart rate such that the heart does not have enough time to fill the atria with blood before contraction of the atria. This can lead to the patient feeling dizziness or lightheadedness because the brain is not receiving adequate oxygen or blood. The onset of this dysrhythmia is typically sudden, and may be prompted by emotional or physical stress.
Supraventricular tachycardia may occur intermittently, and an individual may experience regular heart rates between episodes. Occurrences of supraventricular tachycardia may last from seconds to days in duration. This arrhythmia affects individuals differently - some people live their lives without a need for treatment options or restrictions, whereas others require medication, lifestyle changes, or procedures to manage or terminate the rapid heart rate or associated symptoms. Supraventricular tachycardia is generally not considered life-threatening unless an individual has existing cardiac conditions or damage to the heart; some patients with an extreme case may experience cardiac arrest or lose consciousness. If frequent episodes of supraventricular tachycardia occur over time and go untreated, the heart may become weakened, contributing to the development of heart failure.
Symptom severity tends to be associated with the duration of time that supraventricular tachycardia takes place. Signs or symptoms that may present with SVT include:
Potential causes of supraventricular tachycardia include:
Care of the conscious patient should be initiated using the Advanced Cardiovascular Life Support (ACLS) Primary Assessment. Components of this assessment include evaluating the patient’s airway, breathing, circulation, disability, and potential exposure. Actions the healthcare provider can take to care for a conscious patient are outlined in the ACLS Primary Assessment, where assessment findings guide appropriate measures of care. Examples of actions to take include managing the patient’s airway and supplying supplemental oxygen if needed, determining the patient’s cardiac rhythm, obtaining intravenous (IV) access, initiating defibrillation or cardioversion, and monitoring vital signs. Additionally, any potential neurological deficits need to be identified. Clothing should be removed to complete a visual assessment of the patient, searching for medical alert identification or possible bleeding, trauma, or burns. After the ACLS Primary Assessment has been completed, the healthcare provider should perform the ACLS Secondary Assessment. H’s and T’s should be evaluated for potential causes of the patient’s clinical condition, a focused medical history will be completed, and a differential diagnosis should be established.
The patient’s clinical condition and cardiac rhythm will indicate which ACLS algorithm should be followed at this stage of care. An adult patient with a pulse experiencing tachycardia (such as supraventricular tachycardia) will require guided care under the ACLS Adult Tachycardia With a Pulse Algorithm. The pathway through the algorithm is dependent on whether the patient is considered stable or unstable. A patient with stable tachycardia has an increased heart rate of more than 100 beats per minute without symptoms of hemodynamic instability, and the systems within the body are not compromised or working to compensate due to an increased heart rate. Unstable tachycardia occurs when the patient is experiencing uncoordinated cardiac contractions and a significantly rapid heart rate (often greater than or equal to 150 beats per minute), such that the patient develops symptoms and experiences hemodynamic instability due to decreased cardiac output. When a patient is experiencing unstable tachycardia, it is critical to act quickly when evaluating and managing the patient’s condition to prevent the patient from deteriorating clinically. As described above, patients experiencing supraventricular tachycardia may be symptomatic or asymptomatic. But it is important to remember that a patient with tachycardia who is considered stable may actually be declining, clinically speaking, and be in the process of becoming unstable. It is essential as an ACLS provider to be able to identify the type of tachycardia and then follow through with appropriate interventions, not only to provide optimal care for the patient, but also to contribute to the best potential patient outcome.
The initial steps a healthcare provider should take in caring for a conscious adult patient with a pulse are to complete the ACLS Primary and Secondary Assessments, as described above. If it has been determined that the cardiac rhythm is identified as supraventricular tachycardia, the healthcare provider should evaluate whether the patient is experiencing symptoms that are contributing to hemodynamic instability, which would be indicative that the patient is unstable. Examples of symptoms exhibited in an unstable patient may include hypotension, ischemic chest pain, altered mental status, or shock. In determining that the adult patient is unstable, symptomatic, and is experiencing tachycardia (with a rhythm such as supraventricular tachycardia), the ACLS Adult Tachycardia With a Pulse Algorithm should be followed for guidance on evaluation and management of the patient. Synchronized cardioversion and sedation would be indicated in this algorithm for a symptomatic patient experiencing persistent tachyarrhythmia, such as supraventricular tachycardia.
If a patient is experiencing symptomatic tachycardia with a heart rate of 150 beats per minute or more and is considered symptomatically and hemodynamically unstable, they are a candidate for cardioversion. However, patients may be symptomatic at heart rates less than 150 beats per minute, most notably if they have pre-existing cardiovascular disease or other potential risk factors or contributing causes as discussed above. Therefore, the healthcare provider must understand when cardioversion should be used, the medications indicated for cardioversion, how to properly prepare the patient for cardioversion, and how to utilize the cardioverter.
The ACLS Electrical Cardioversion Algorithm provides guidance for healthcare providers performing cardioversion. A symptomatic and unstable patient with a heart rate of 150 beats per minute or more, with a cardiac rhythm such as supraventricular tachycardia, warrants synchronized cardioversion. Synchronized cardioversion coordinates shock delivery to the patient, where the device analyzes the patient’s cardiac rhythm in order to deliver a shock that is synchronized with the R wave in the QRS complex. This coordinated delivery can result in a delay before the cardioverter delivers the shock, due to the time needed for the device to analyze the patient’s cardiac rhythm.
Before performing cardioversion, the healthcare provider should ensure the patient has IV access and equipment is at the ready for suctioning, intubation, and measuring oxygen saturation. Contingent on the severity of the patient’s symptoms and how hemodynamically unstable they may be, sedation medication should be administered before initiating cardioversion. If all elements are in place, synchronized cardioversion should then be conducted. Recommendations specific to the cardioverter being utilized should be followed when determining appropriate settings for energy levels during shock delivery. If the patient’s cardiac rhythm remains unchanged following cardioversion, the healthcare provider or team should re-evaluate any potential underlying causes contributing to the patient’s condition. The energy level should then be increased for the next attempt at cardioversion.
If the patient with supraventricular tachycardia is symptomatic and unstable, and the ECG reading indicates a regular, narrow, QRS complex (as is common with supraventricular tachycardia), adenosine can be used in addition to synchronized cardioversion. Six milligrams of adenosine should be administered intravenously as an initial dose. If a second dose of adenosine is needed, 12 mg of adenosine may be administered intravenously. Each dose of adenosine should be given rapidly (as it is intended as a means of pharmacologic or chemical cardioversion) and followed by a normal saline flush.
Within the ACLS Adult Tachycardia With a Pulse Algorithm, if the patient experiencing supraventricular tachycardia is stable, has a regular rhythm, and does not have a wide QRS complex (greater than or equal to 0.12 seconds), vagal maneuvers can be initiated as a first step. If vagal maneuvers do not revert the rhythm, adenosine may be rapidly administered (if the rhythm is regular) at 6 mg intravenously for an initial dose and 12 mg for a second dose (if needed). A normal saline flush should follow each dose of adenosine. Medications such as a beta blocker or calcium channel blocker may also be considered. If the patient with supraventricular tachycardia is stable and has a wide QRS complex (greater than or equal to 0.12 seconds), adenosine may be considered if the patient has both a regular and monomorphic cardiac rhythm. Alternatively, antiarrhythmic medications such as procainamide, amiodarone, or sotalol may be administered via IV infusion.
Patients experiencing supraventricular tachycardia should be transferred to a higher level of care for further evaluation and management.
What Is Paroxysmal Supraventricular Tachycardia?
Paroxysmal supraventricular tachycardia is considered an intermittent supraventricular tachycardia that occurs at random, with a heart rate of 150-220 beats per minute. Paroxysmal supraventricular tachycardia is another name for supraventricular tachycardia.
What Are Vagal Maneuvers and How Are They Utilized in Managing Supraventricular Tachycardia?
Vagal maneuvers are utilized in stable patients with supraventricular tachycardia, and can be considered part of a management plan for patients with chronic recurrent supraventricular tachycardia. The Valsalva maneuver is an example of a vagal maneuver intended to stimulate the parasympathetic nervous system. This results in a slowing of the development of an impulse at the sinus node of the heart, which then reduces the speed of conduction at the AV node, extending the refractory period at the AV node, and decreasing the force of ventricular contractions. The Valsalva maneuver is completed by a patient modifying their breathing, where they exhale against the glottis, holding this for 10-15 seconds. The patient can do this by bearing down as if they were to have a bowel movement, blowing through a straw or syringe, or applying cold water or ice packs to their face.
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