Approach Considerations
Acute management of paroxysmal supraventricular tachycardia (PSVT) includes controlling the rate and preventing hemodynamic collapse. If the patient is hypotensive or unstable, immediate cardioversion with sedation must be performed. If the patient is stable, vagal maneuvers can be used to slow the heart rate and to convert to sinus rhythm. If vagal maneuvers are not successful, adenosine can be used in increasing doses. If adenosine does not work, atrioventricular (AV) nodal blocking agents like calcium channel blockers or beta-blockers should be used, as most patients who present with PSVT have AV nodal reentrant tachycardia (AVNRT) or AV reentrant tachycardia (AVRT). These arrhythmias depend on AV nodal conduction and therefore can be terminated by transiently blocking this conduction.
Patients with symptomatic Wolff-Parkinson-White (WPW) syndrome should not be treated with calcium channel blockers or digoxin unless the pathway is known to be of low risk (long anterograde refractory period). This is because of the potential for rapid ventricular rates should atrial fibrillation or atrial flutter occur, which can result in cardiac arrest.
Patients with preexcited atrial fibrillation should not be treated with intravenous AV nodal blocking agents, such as adenosine, beta-blockers, calcium channel blockers, and digoxin. Rather, if the patient is hemodynamically stable, intravenous procainamide should be administered. If the patient is unstable, direct current cardioversion should be performed.
Electrical cardioversion
Electrical cardioversion is the most effective method for restoring sinus rhythm. Synchronized cardioversion starting at 50J can be used immediately in patients who are hypotensive, have pulmonary edema, have chest pain with ischemia, or are otherwise unstable.
If atrial fibrillation has been present for longer than 24-48 hours, defer cardioversion until the patient has been adequately anticoagulated to prevent thromboembolic complications. [40, 36, 50, 51, 52, 53, 54, 41]
Inpatient care
Patients who require cardioversion, are unstable, and have comorbid illnesses should be admitted to the hospital. Patients who are young, healthy, and asymptomatic may be discharged and advised to have a follow-up examination with their primary physician or cardiologist. If the patient is having more frequent episodes of paroxysmal SVT and medical therapy is not successful or desired, then radiofrequency catheter ablation should be proposed.
Diet and activity
Dietary changes depend on underlying medical problems. Changes in physical activity depend on underlying cardiac problems and other comorbidities.
Consultations
A cardiologist should be consulted for patients with frequent episodes of paroxysmal SVT, syncope, and/or preexcitation syndromes. Consultation with a cardiologist should also be obtained for patients in whom medical management has failed.
An electrophysiologist should be consulted for patients considered for radiofrequency catheter ablation. Pediatric patients should be referred to a pediatric electrophysiologist.
Transfer
Patient transfer to a center with radiofrequency catheter ablation is reasonable if this therapy is planned. Alternatively, patients can be discharged home and scheduled for outpatient procedures. Exceptions include patients with syncope, profound symptoms, or preexcited atrial fibrillation or atrial flutter.
Monitoring
Patients treated medically should be monitored regularly. Patients cured with radiofrequency catheter ablation are typically seen once in a follow-up examination following the procedure, then as needed for recurrent symptoms.
Vagal Maneuvers
The first-line treatment in hemodynamically stable patients, vagal maneuvers, such as breath-holding and the Valsalva maneuver (ie, having the patient bear down as though having a bowel movement), slow conduction in the AV node and can potentially interrupt the reentrant circuit.
Carotid massage is another vagal maneuver that can slow AV nodal conduction. Massage the carotid sinus for several seconds on the nondominant cerebral hemisphere side. This maneuver is usually reserved for young patients. Due to the risk of stroke from emboli, auscultate for bruits before attempting this maneuver. Do not perform carotid massage on both sides. A Valsalva maneuver, if performed properly by the patient, can frequently avert an attack.
Short-Term Pharmacologic Management
When SVT is not terminated by vagal maneuvers, short-term management involves intravenous adenosine or calcium channel blockers. Adenosine is a short-acting drug that blocks AV node conduction; it terminates 90% of tachycardias due to AVNRT or AVRT. Adenosine does not usually terminate atrial tachycardia, although it is effective for terminating SNRT. [40, 36, 50, 55, 53, 41]
Typical adverse effects of adenosine include flushing, chest pain, and dizziness. These effects are temporary because adenosine has a very short half-life of 10-20 seconds. [54]
Other alternatives for the acute treatment of SVT include calcium channel blockers, such as verapamil and diltiazem, as well as beta-blockers, such as metoprolol or esmolol. Verapamil is a calcium channel blocker that also has AV blocking properties. It has a longer half-life than adenosine and may help to maintain sinus rhythm following the termination of SVT. It is also advantageous for controlling the ventricular rate in patients with atrial tachyarrhythmia. [9, 56, 50, 51, 10, 53, 54, 11]
In a randomized clinical trial of 92 patients with paroxysmal supraventricular tachycardia, Shaker et al found evidence that oral verapamil can decrease recurrence of paroxysmal supraventricular tachycardia after successful control with intravenous adenosine. Patients in the adenosine-only group received adenosine; patients in the adenosine/verapamil group received adenosine and then received oral verapamil immediately after conversion of the rhythm to sinus rhythm. The adenosine/verapamil group had a significantly lower recurrence rate than the adenosine-only group between 30 and 120 minutes post-treatment and thereafter. [70]
Wide-complex tachycardia
Acute management of a wide-complex tachycardia in a hemodynamically unstable patient requires immediate cardioversion, whereas in a stable patient, intravenous procainamide, propafenone, or flecainide is acceptable. Amiodarone is preferred in patients with impaired left ventricular function or in patients with heart failure or structural heart disease. [57]
Atrial fibrillation and atrial flutter
The treatment of atrial fibrillation and atrial flutter involves controlling the ventricular rate, restoring the sinus rhythm, and preventing embolic complications. The ventricular rate is controlled with calcium channel blockers, digoxin, amiodarone, and beta-blockers. The sinus rhythm may be restored with either pharmacologic agents or electrical cardioversion. Medications such as ibutilide, propafenone, and flecainide convert atrial fibrillation and atrial flutter of short duration to sinus rhythm. Since atrial fibrillation and atrial flutter increase risk of stroke or cerebrovascular accidents, anticoagulation is usually recommended. Drugs like warfarin, as well as novel oral anticoagulant agents like dabigatran, rivaroxaban, and apixaban, may be used for anticoagulation. [58, 59, 60]
Long-Term Pharmacologic Management
The choice of long-term therapy for patients with SVT depends on the type of tachyarrhythmia that is occurring and the frequency and duration of episodes, as well as the symptoms and the risks associated with the arrhythmia (eg, heart failure, sudden death). Evaluate patients on an individual basis, and tailor treatment to the best therapy for the specific tachyarrhythmia.
Patients with paroxysmal SVT may initially be treated with calcium channel blockers, digoxin, and/or beta-blockers. Class IA, IC, or III antiarrhythmic agents are used less frequently because of the success of radiofrequency catheter ablation. [40, 36, 50, 51, 52, 53, 54, 41, 61]
Radiofrequency Catheter Ablation
Prior to the advent of percutaneous radiofrequency catheter ablation, open cardiac surgical procedures were the only means of curing paroxysmal SVT. Currently, however, open surgical procedures are rarely performed, and catheter ablation is considered the first-line treatment of many recurrent symptomatic SVTs. It is generally performed using conscious sedation in an outpatient setting or with an overnight hospital stay for observation.
Catheter ablation involves focally ablating the crucial component of the arrhythmic mechanism. For example, in AVNRT, the slow pathway is ablated, which prevents the reentry cycle. The accessory pathway is targeted in patients with AVRT. Focal atrial tachycardia, atrial flutter, and, in some cases, atrial fibrillation can also be cured with ablation.
Consider catheter ablation for any patient with symptomatic paroxysmal SVT in whom long-term medical treatment is not effectively tolerated or desired. In addition, because of the risk of sudden cardiac death, perform catheter ablation on patients with symptomatic WPW syndrome. [9, 40, 10, 41, 13] The optimal management strategy for patients with asymptomatic preexcitation syndromes remains uncertain. [62, 63, 19, 9, 13]
The efficacy of catheter ablation often exceeds that of medical therapy for symptoms, recurrences requiring medical intervention, and the prevention of consequences, such as defibrillator discharges in patients with an implanted defibrillator and SVT. (A study by Mainigi et al found that SVT causes a significant number of inappropriate implantable cardioverter-defibrillator therapies and that catheter ablation is an effective strategy to avoid these inappropriate therapies. [64] ) Catheter ablation is more than 90% effective in curing paroxysmal SVT.
Complications
Potential complications of radiofrequency catheter ablation include the following:
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Hematoma
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Bleeding
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Infection
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Pseudoaneurysm
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Myocardial infarction
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Cardiac preformation
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Heart block that requires a pacemaker
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Thromboembolic complications - Including deep venous thrombosis and systemic embolism
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Cardiac tamponade
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Stroke
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Need for emergency surgery
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Radiation burn
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Increased risk of malignancy - Lifetime risk of fatal malignancy as a result of radiation exposure is low
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Death - Risk is approximately 0.1%
Bohnen et al performed a prospective study to assess the incidence and predictors of major complications from contemporary catheter ablation procedures. Major complication rates ranged between 0.8% (SVT) and 6% (ventricular tachycardia associated with structural heart disease), depending on the ablation procedure performed. The investigators reported that renal insufficiency was the only independent predictor of a major complication. [65]
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Sinus tachycardia. Note that the QRS complexes are narrow and regular. The patient's heart rate is approximately 135 bpm. P waves are normal in morphology.
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Atrial tachycardia. The patient's heart rate is 151 bpm. P waves are upright in lead V1.
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Multifocal atrial tachycardia. Note the different P-wave morphologies and irregularly irregular ventricular response.
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Atrial flutter. The patient's heart rate is approximately 135 bpm with 2:1 conduction. Note the sawtooth pattern formed by the flutter waves.
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Atrial fibrillation. The patient's ventricular rate varies from 130-168 bpm. The rhythm is irregularly irregular. P waves are not discernible.
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Atrioventricular nodal reentrant tachycardia. The patient's heart rate is approximately 146 bpm with a normal axis. Note the pseudo S waves in leads II, III, and aVF. Also note the pseudo R' waves in V1 and aVR. These deflections represent retrograde atrial activation.
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Same patient as in the previous image. The patient is in sinus rhythm following atrioventricular nodal reentrant tachycardia.
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Image A displays the slow pathway and the fast pathway, with a regular impulse being conducted through the atrioventricular node. Image B displays a premature impulse that is conducted in an anterograde manner through the slow pathway and in a retrograde manner through the fast pathway, as is seen in typical atrioventricular nodal tachycardia. Image C displays the premature impulse conducting in a retrograde manner through the pathway and the impulse reentering the pathway with anterograde conduction, which is seen commonly in patients with atypical atrioventricular nodal tachycardia.
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Wolff-Parkinson-White pattern. Note the short PR interval and slurred upstroke (delta wave) to the QRS complexes.
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The left image displays the atrioventricular node with the accessory pathway. The impulse is conducted in an anterograde manner in the atrioventricular node and in a retrograde manner in the accessory pathway. This circuit is known as orthodromic atrioventricular reentrant tachycardia and can occur in patients with concealed accessory tracts or Wolff-Parkinson-White syndrome. The right image displays the impulse being conducted in an anterograde manner through the accessory pathway and in a retrograde manner via the atrioventricular node. This type of circuit is known as antidromic atrioventricular reentrant tachycardia and occurs only in patients with Wolff-Parkinson-White syndrome. Both patterns may display retrograde P waves after the QRS complexes.
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Orthodromic atrioventricular reentrant tachycardia. This patient has Wolff-Parkinson-White syndrome.
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The left panel depicts antidromic atrioventricular reentrant tachycardia. The right panel depicts sinus rhythm in a patient with antidromic atrioventricular reentrant tachycardia. Note that the QRS complex is an exaggeration of the delta wave during sinus rhythm.
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Atrial fibrillation in a patient with Wolff-Parkinson-White syndrome. Note the extremely rapid ventricular rate and variability in QRS morphology. Several minutes later, the patient developed ventricular fibrillation.
