The rapid heartbeat and other symptoms of supraventricular tachycardia can be extremely alarming, but the condition is typically not life-threatening
Supraventricular tachycardia (SVT) is defined as an abnormally rapid heart rhythm having an electropathologic substrate emerging above the bundle of His (atrioventricular bundle), thus causing the heart to escalate to rates higher than 100 beats per minute.1-4 Most types of SVT are triggered by a reentry mechanism that may be induced by premature atrial or ventricular ectopic beats and are classified according to the location of the reentry circuit.1-5 The accelerated heart rate can be alarming to a patient, because onset is often abrupt and, in some cases, episodes can be reoccurring and persistent.1
SVTs are one of the most frequent causes of emergency department and physician office visits.5 Although most cases of SVT are not considered to be dangerous or life threatening, frequent episodes can weaken the cardiac muscle over time, and should therefore be addressed with medical intervention to prevent further complications.1-4
The most commonly occurring forms of SVT include paroxysmal SVT (PSVT), atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reciprocating tachycardia (AVRT), and atrial tachycardia (AT).3-6 Other forms of SVT include atrial fibrillation (AF) and atrial flutter.4-6
SVTs (excluding AF, atrial flutter, and multifocal AT) affect an estimated 35 per 100,000 individuals.4,5 They occur more commonly in women than men.4-7 PSVT in the absence of structural heart disease can manifest at any age, but most often initially presents between the ages of 12 and 30 years. 4-7 AVRT is the most commonly occurring SVT among the pediatric population, accounting for an estimated 30% of cases.5,6
AVNRT is the most common form of SVT among adults, accounting for 50% to 60% of SVTs. The majority of patients with AVNRT do not have structural heart disease. This form of SVT occurs most prevalently in young healthy women, but does also occur in patients with an underlying cardiovascular condition.4 A condition known as Wolff-Parkinson-White syndrome, an inherited disorder in which an extra electrical connection is present at birth between the atria and the ventricles, may cause patients to experience SVT episodes.4-8
Risk Factors and Causes of SVT
Although SVT episodes can occur in anyone, there are certain factors that may increase an individual’s risk. Examples of these risk factors include2,7-13:
• Excessive caffeine or alcohol use
• History of tobacco use
• Illicit drug use
• Extreme psychological stress and anxiety
• Low potassium and magnesium levels
• Family history of tachycardia
• Structural abnormalities of the heart
• Adverse reactions from certain pharmacologic agents (ie, antihistamines, theophylline, cough and cold preparations, appetite suppressants )
• Certain medical conditions (eg, cardiovascular disease, long-term respiratory disease, diabetes, anemia, cancer)
Table. The 4 Most Common Types of SVTs
Type of SVT
Can occur at any age
Atrioventricular nodal reentrant tachycardia
· Most commonly occurring SVT (approximately 50% to 60%)
· Occurs more often in younger women
Atrioventricular reciprocating tachycardia
· Second most common SVT (approximately 30%)
· Occurs most often in younger women and in the pediatric patient population
· May be considered comorbid with Wolff-Parkinson-White syndrome
Atrial tachycardia (AT)
· Third most common SVT (approximately 10%)
· There are 2 types: AT and multifocal AT
· AT has 2 forms: focal and macroreentrant
· Multifocal AT occurs more often in individuals who are middle age or in individuals who have heart failure or COPD
COPD = chronic obstructive pulmonary disease; SVT = supraventricular tachycardia.
Adapted from references 4-6.
Symptoms Commonly Associated with SVT Episodes
Although some patients with SVT may not experience any symptoms, other patients present during childhood, young adulthood, or middle age with symptoms that typically have a sudden onset and termination.4-6,12 When the patient is asymptomatic or presents with few symptoms, it can cause a delay in diagnosis. 4
Results from various studies have noted that the symptoms commonly reported by patients with SVT can mimic other conditions and are sometimes mistaken for anxiety attacks or panic disorders, especially among the female patient population.14-16
The most prevalent symptom during an episode of SVT is palpitations or a sensation that the heart is beating rapidly, fluttering, or racing.12-14,17 These episodes may last for a few seconds or several hours. The other symptoms associated with SVTs include dizziness or light-headedness, chest pain, dyspnea, anxiety, palpitations including pulsations in the neck area, diaphoresis, fatigue, vision changes, and, in some rare cases, syncope.12,14,17
SVT is typically not a serious or lifethreatening condition, but medical care should be sought, especially if it is the individual’s first episode or if episodes are severe and recurring.17,18
Because SVT can be episodic, it can sometimes be misdiagnosed as anxiety or a panic disorder. For this reason, obtaining a thorough patient medical and medication history is very important in the diagnosis of SVTs and to help determine possible triggers.4-6 Besides a physical examination, an electrocardiogram may be used for diagnosis to provide clues about the type of SVT, reveal any damage to the cardiac muscle, and identify any other conduction disturbances. Physicians may also elect to use other diagnostic tools, such as an event monitor or a Holter monitor, blood work (ie, thyroid stimulating hormone levels, metabolic profile, complete blood count, cardiac enzymes), electrophysiology study, or an echocardiogram.2,4-8,18
For some patients, most or all of their SVT episodes may cease on their own; other patients require medical intervention. The management of SVT can be classified as short term (immediate/acute) or long term.4
Short-term management treatment options can involve both pharmacologic and nonpharmacologic measures. In most patients, the drug of choice for acute therapy is either adenosine or verapamil.7,18,19 The use of intravenous adenosine or the calcium channel blocker verapamil are considered safe and effective therapies for controlling SVTs.4,7,18,19
The advantages of adenosine include a rapid onset of action (typically within 10 to 25 seconds via a peripheral vein), short half-life (less than 10 seconds), and a high degree of efficacy.19 The short halflife of this agent minimizes the severity of adverse effects, which include facial flushing, chest tightness, dyspnea, and transient sinus arrest and/or atrioventricular block.19 The use of adenosine is contraindicated in those patients with sinus node dysfunction or second or third degree block and should be used with caution in patients with severe obstructive lung diseases.4,7,18,19
Verapamil’s efficacy is comparable with adenosine, but its negative inotropic effect, vasodilatory effects, and prolonged half-life make it unsuitable for patients with congestive heart failure or for those patients classified as hypotensive.4,7,18,19 Adenosine and calcium channel blockers are contraindicated for use in patients with Wolff-Parkinson-White syndrome.4,17-20
Intravenous administration of calcium channel blockers, such as diltiazem, or beta-blockers, such as esmolol, is also commonly used for short-term SVT management.4,7,17,18,20
Vagal maneuvers, a nonpharmacologic approach for short-term management, are techniques that increase vagal tone to decrease the patient’s heart rate.4 Vagal maneuvers include the Valsalva maneuver, in which one attempts to exhale forcefully through a closed airway, coughing while sitting with the upper body bent forward, and splashing ice water on the face.4-6 In some cases, vagal maneuvers are used as the initial measure to terminate SVT.4-6,17,18,20 Vagal maneuvers are often considered the first line of therapy in younger patients who are hemodynamically stable.4,18
For patients with recurring episodes of SVT, long-term therapy may be required.4-7,18,19 The long-term management of SVT is most often dependent upon the type of SVT, patient medical history, the frequency and severity of the episode.4-7,19 Long-term treatment includes surgical options or the use of pharmacologic agents.
Radiofrequency ablation (RFA) is considered a safe, effective, and cost-effective surgical procedure for preventing or suppressing SVT episodes for those patients with frequent SVT episodes and/or those who want to avoid the use of pharmacologic agents.4-6 It is also beneficial to those patients who are not responding to or who are unable to tolerate pharmacologic agents.4-7,18,19
Studies report that the RFA procedure has high efficacy rates (single procedure success, 93.2%), overall low all-cause mortality (~0.1%), and is associated with low adverse events (~2.9%). 18 Despite the reports of high success rates, this procedure is not always utilized in clinical practice.18
Pharmacologic agents commonly used in the long-term management of SVT include amiodarone, procainamide, calcium channel blockers (eg, diltiazem and verapamil), and beta-blockers (eg, metoprolol or atenolol).4-6,18 Results report that for chronic oral AV node-reentry, the use of calcium channel blockers and betaadrenergic blockers is preferred and has been shown to improve symptoms in 60% to 80% of patients.7,18
The Role of the Pharmacist
Patients who have experienced an SVT episode will probably agree that they can be alarming and unsettling. Patient counseling that focuses on how to effectively handle SVT episodes and the possible treatments and preventive strategies can have a positive impact on patients’ overall quality of life. With the right information, patients can make informed choices regarding the treatment of this condition.
Pharmacists should counsel patients on the proper use of any prescribed medications, including the proper use, potential adverse effects, contraindications associated with the selected therapy, and the importance of adherence. Patients should also be reminded to maintain routine appointments with their primary health care provider for monitoring and to not use any medications, including OTC products and herbal supplements, without first consulting their primary health care provider.
Patients can better manage SVTs by avoiding the use of tobacco, alcohol, and caffeine, decreasing stress levels by incorporating relaxation techniques into their daily routine, eating a balanced diet, and exercising regularly. Patients should be reminded to immediately seek medical attention if a SVT episode does not terminate within a few minutes after using preventive techniques or if they experience chest pains, palpitations, or episodes of syncope, or if new symptoms manifest or existing symptoms worsen. 4,20
As one of the most accessible health care professionals, pharmacists can help to ease the concerns of those patients who experience SVTs by ensuring that they are thoroughly educated about this condition. They can also reassure patients that SVTs can be managed and that they lead normal, productive lives. PT
Ms. Terrie is a clinical pharmacy writer based in Haymarket, Virginia.
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