Atrioventricular Reentrant Tachycardia

Atrioventricular Reentrant Tachycardia – 21 Interesting Facts

AVRT (atrioventricular reentrant tachycardia) is a reentrant tachycardia with a circuit that consists of 2 distinct pathways: the AV (atrioventricular) conduction system and the AP (accessory pathway)
The majority of AVRT is orthodromic (narrow complex) with short RP interval (RP interval is less than half of RR interval)
5% to 10% of AVRT is antidromic tachycardia with wide (preexcited) QRS complexes and long RP interval (RP interval is greater than half of RR interval)
Diagnosis usually requires only ECG of an arrhythmia and ECG in sinus rhythm; however, EP (electrophysiologic) study is often needed to determine the precise mechanism of arrhythmia, risk of AP, and location of AP
Acute treatment of AVRT is dependent on the hemodynamic stability of the patient and the presence or absence of preexcitation during arrhythmia and on resting ECG in sinus rhythm
Hemodynamically unstable patients should undergo electrical cardioversion to restore normal sinus rhythm
Treatment of hemodynamically stable patients with acute AVRT involves a stepwise approach:
Vagal maneuvers are recommended as initial nondrug therapy
Adenosine injection is recommended as initial diagnostic and therapeutic management of regular SVT
If adenosine is ineffective, IV verapamil, diltiazem, or β-blockers are recommended in patients with orthodromic AVRT who do not have preexcitation on resting ECG
Recommend IV procainamide or ibutilide in patients in whom verapamil, diltiazem, or β-blockers are ineffective or in patients with preexcited atrial fibrillation
Electrical cardioversion is recommended in hemodynamically stable patients if medical approach is ineffective or contraindicated
V amiodarone, IV digoxin, and IV or oral β-blockers, diltiazem, and verapamil should be avoided in the acute management of patients with preexcited atrial fibrillation due to increased risk of ventricular arrhythmias
Ongoing management of AVRT
Patients with AVRT or evidence of preexcitation should be referred to a cardiac electrophysiologist for further management and risk stratification
Catheter ablation of the AP is recommended as first line treatment to prevent further episodes of AVRT or preexcited atrial fibrillation
Catheter ablation is also recommended in patients found to have asymptomatic preexcitation, those with high-risk occupations, and those found to have a high-risk AP on EP study
Oral β-blockers, diltiazem, or verapamil can be used for ongoing management of patients with orthodromic AVRT without preexcitation on their resting ECG who decline catheter ablation or are not candidates for it¹
In the absence of coronary or structural heart disease, the class IC antiarrhythmic agents, oral flecainide and propafenone, can be used in patients with AVRT and/or preexcited atrial fibrillation who decline catheter ablation or are not candidates for it¹
Oral dofetilide and sotalol can be used in those patients with AVRT and/or preexcited atrial fibrillation who have a history of coronary or structural heart disease¹
Oral amiodarone can be considered for ongoing management in those patients with AVRT and/or preexcited atrial fibrillation in whom catheter ablation and other pharmacotherapies are ineffective or contraindicated; evaluate risk versus benefit regarding potential toxicity associated with long-term use¹

Alarm Signs and Symptoms

Patients presenting with syncope should prompt further investigation, particularly in those with a history of preexcitation on ECG

Introduction

SVT (supraventricular tachycardia): any of the group of tachycardias whose mechanism involves tissue at or above the His bundle of the heart, originating at or above the AV (atrioventricular) node¹
- Includes atrial tachycardia (focal and multifocal), inappropriate sinus tachycardia, junctional tachycardia, AVNRT (atrioventricular nodal reentrant tachycardia) and AVRT (defined as follows)
AVRT (atrioventricular reentrant tachycardia), also referred to as atrioventricular reciprocating tachycardia: a form of SVT that consists of a reentrant circuit involving the normal AV conduction system and an AP (defined as follows)
AP (accessory pathway): a pathway between the atrial and ventricular myocardium that allows conduction to bypass the AV node¹
WPW (Wolff-Parkinson-White) syndrome: consists of the presence or prior documentation of a symptomatic arrhythmia along with evidence of a preexcitation pattern on ECG consistent with a manifest (ie, conducting in the anterograde direction) AP¹
- The most common type of arrhythmia associated with WPW is AVRT
  - Other, less common, arrhythmias associated with WPW include preexcited atrial fibrillation, atrial flutter, and AVNRT
- ECG findings (ie, preexcitation pattern) can be intermittent or not easily appreciated for some APs²³⁴
- WPW pattern: refers to the presence of the characteristic preexcitation pattern on ECG alone (ie, in the absence of an associated symptomatic arrhythmia)

Background Information

Figure 1. Key structures of the cardiac electrical system.Adapted from Rodriguez R et al. Anatomy of the mitral valve. In: Goldman SM et al, eds. Diagnosis and Treatment of Mitral Valve Disease. Elsevier; 2023:1-13, Figure 1.9.
Figure 2. Mechanism of atrioventricular reentrant tachycardia (orthodromic).

Normal electrical conduction in the heart starts at the sinus node in the right atrium and travels down through the AV node and His-Purkinje system to activate the ventricles (Figure 1)
The presence of an AP allows electrical impulses to bypass the normal conduction pathway and travel faster than they do over the AV node (Figure 2)
- Most APs have bidirectional conduction capabilities; however, some are capable of only retrograde conduction from the ventricle to the atrium⁵
  - A manifest AP conducts anterogradely (atrium to ventricle) during sinus rhythm and can be detected as a preexcitation pattern on the ECG:¹
    - Short PR interval
    - Slurring of the initial upstroke of the QRS complex (ie, delta wave)
  - Manifest AP have the potential to conduct very rapidly if atrial fibrillation occurs (ie, preexcited atrial fibrillation), placing patients at risk for ventricular fibrillation and SCD (sudden cardiac death)
  - A concealed AP conducts only retrogradely (ventricle to atrium) and does not alter the ECG pattern during sinus rhythm; the pathway may still support a reentrant tachycardia such as AVRT¹

Epidemiology

Orthodromic (narrow complex) AVRT represents over 90% of AVRT and approximately 20% to 30% of all sustained SVT⁶
5% to 10% of AVRT is antidromic tachycardia with wide (preexcited) QRS complexes
- Antidromic (wide complex) AVRT occurs in approximately 3% to 8% of patients with WPW syndrome⁶
The majority of patients with AVRT have structurally normal hearts, but it can be associated with congenital abnormalities⁷
- Up to 20% of patients with Ebstein anomaly have an AP, which can lead to AVRT⁷

Etiology

AVRT involves a reentrant circuit made up of an AP, the atrium, the AV node (or a second AP), and the ventricle¹ (see Figure 2)
- Orthodromic AVRT: more common form of AVRT; uses the AP as the retrograde limb of the reentrant circuit (from the ventricle to the atrium) and the AV node as the anterograde limb (atrium to ventricle); the QRS morphology on ECG is generally narrow¹
- Antidromic AVRT: less common form of AVRT; uses the AP as the anterograde limb of the reentrant circuit (from the atrium to the ventricle) and the AV node as the retrograde limb (ventricle to atrium); generally associated with a wide QRS morphology; can be difficult to distinguish from ventricular tachycardia on ECG¹

Diagnosis

Approach to Diagnosis

Figure 3. Diagnostic algorithm for narrow QRS tachycardia. – AF, atrial fibrillation; AT, atrial tachycardia; AV, atrioventricular; AVNRT, atrioventricular nodal reentrant tachycardia; AVRT, atrioventricular reentrant tachycardia; JET, junctional ectopic tachycardia; VT, ventricular tachycardia.From Brugada J et al. 2019 ESC guidelines for the management of patients with supraventricular tachycardia: the Task Force for the Management of Patients With Supraventricular Tachycardia of the European Society of Cardiology (ESC). Eur Heart J. 2020;41(5):655-720, Figure 1.

Obtain a 12-lead ECG in any patient presenting with symptoms concerning for an arrhythmia
- An ECG obtained during the time of arrhythmia can be useful to identify the type of arrhythmia and whether the AVRT is orthodromic or antidromic; however, in some cases additional diagnostic testing may be needed to identify the specific type of SVT
  - ECG will demonstrate a regular tachycardia that typically ranges from 150 to 200 beats per minute with either narrow (orthodromic AVRT) or wide (antidromic AVRT) QRS complexes
- An ECG obtained when the patient is in sinus rhythm may exhibit a preexcitation pattern consistent with the presence of a manifest AP
- A diagnostic algorithm can be used to identify orthodromic (narrow QRS) AVRT⁶ (Figure 3)
A cardiac EP (electrophysiologic) study is typically needed to determine the precise mechanism of AVRT, risk of AP, and location of AP

Workup

History

A patient with a history of AVRT may report the following symptoms:
- Palpitations
- Lightheadedness and/or dizziness
- Syncope or presyncope
- Chest pain
A history of aborted/resuscitated SCD should raise suspicion for previously undiagnosed WPW syndrome involving a high-risk AP that, in rare occurrences, can precipitate preexcited atrial fibrillation resulting in ventricular fibrillation
- Consultation with a cardiac electrophysiologist for further evaluation and management is recommended⁸⁹¹⁰¹¹
- The risk of SCD is highest during the first 2 decades of life

Physical Examination

Physical examination is usually not specific in the setting of AVRT
- Evaluate vital signs, noting the presence of tachycardia
- The large majority of patients presenting with AVRT will have normal cardiac examination findings on auscultation
During an episode of AVRT, patients may become dyspneic, diaphoretic, or hypotensive
- Evaluate for crackles on pulmonary examination consistent with pulmonary vascular congestion
If cardiomyopathy or congenital abnormalities are present, then associated physical findings may be present on examination

Laboratory Tests

Laboratory assessment will not be expected to diagnose an arrhythmia, but it may help reveal conditions that may contribute to precipitating an episode:
- CBC to evaluate for anemia
- Chemistry panel to evaluate for electrolyte derangement
- Liver function tests to evaluate for underlying liver disease
- Thyroid function tests to evaluate for thyroid disorder
- Drug screening

Imaging Studies

Obtain a transthoracic echocardiogram to evaluate cardiac structure and function and rule out structural and congenital abnormalities¹
- Left ventricular function may appear depressed during an acute episode, but it should normalize once tachycardia resolves if due solely to an arrhythmic or tachycardic mechanism, in the absence of a tachycardia-mediated cardiomyopathy

Diagnostic Procedures

Perform exercise stress testing for the following reasons:
- To reproduce an episode and document its relationship to exercise or to monitor the response to medical therapy
- To risk stratify an asymptomatic patient with a manifest AP (ie, preexcitation on ECG)
  - Abrupt loss of preexcitation during exercise testing is a sign of a low-risk AP that is not capable of maintaining rapid conduction, particularly in the context of atrial fibrillation, that may result in SCD; in addition, intermittent preexcitation on resting ECG or during ambulatory monitoring are also signs of a low-risk AP¹²¹³¹⁴¹⁵
  - Note that noninvasive tests have an approximately 90% positive predictive value and 30% negative predictive value for identifying AP with life-threatening characteristics¹²¹³¹⁵
Refer to cardiac electrophysiologist for invasive EP study to diagnose the exact mechanism of AVRT, localize the AP, and risk stratify patients for arrhythmic and life-threatening events¹⁶
- EP study can diagnose the exact mechanism of AVRT and localize the AP for treatment
- EP study can identify a high-risk AP that is capable of rapid conduction and sustained, potentially life-threatening, arrhythmias

Diagnostic Tools

Obtain a 12-lead ECG to evaluate any patient presenting with tachycardia (heart rate more than 100 beats per minute)
- AVRT can be identified on ECG as a regular tachycardia with narrow (orthodromic AVRT) or wide (antidromic AVRT) QRS complexes
  - Ventricular rate is regular and usually ranges from 150 to 250 beats per minute
  - In orthodromic AVRT, the QRS complex is narrow; inverted P waves can usually be seen in the early part of the ST-T segment, which leads to a short RP interval (RP less than half of RR interval), but not less than 90 milliseconds¹
  - In antidromic AVRT, the QRS complex is wide; inverted P waves appear later along the ST-T segment, leading to a long RP interval (RP more than half of RR interval) and a short PR interval¹
  - The RP interval will remain constant in both types of AVRT regardless of how fast the tachycardia is, as ventriculoatrial activation is linked
- A manifest AP associated with an AVRT can be identified as preexcitation on an ECG when patient is in sinus rhythm; this represents when the ventricles are depolarized in part or in whole via the AP, bypassing the AV node
  - Preexcitation can be recognized by 2 characteristic signs on the ECG:
    - Short PR interval, usually less than 0.12 seconds
    - Delta wave (slurred initiation) of the QRS complex
    - The more rapid the antegrade conduction over the AP (or slower the conduction over the AV node), the more pronounced the delta wave on the ECG
The application of vagal maneuvers followed by IV injection with adenosine may be used to reveal the underlying mechanism of SVT and identify AVRT based on the rhythm’s characteristic response (Table 1)⁶

Table 1. Differential diagnosis of responses of tachycardia to IV adenosine or vagal maneuvers.

Response	Diagnosis
No effect	• Inadequate dose/delivery • High septal VT
Gradual slowing, then acceleration	• Sinus tachycardia • AT
Sudden termination	• AVNRT • AVRT • Sinoatrial nodal reentry
Termination with a P wave	• Effectively rules out AT (therefore AVNRT or AVRT is more likely)
Persistent atrial activity with transient high-grade AV block	• Atrial flutter • Microreentrant AT

Caption: VT, ventricular tachycardia; AT, atrial tachycardia; AVNRT, atrioventricular nodal reentrant tachycardia; AVRT, atrioventricular reentrant tachycardia.

Adapted from Brugada J et al. 2019 ESC guidelines for the management of patients with supraventricular tachycardia: the Task Force for the Management of Patients With Supraventricular Tachycardia of the European Society of Cardiology (ESC). Eur Heart J. 2020;41(5):655-720, Figure 2.

Differential Diagnosis

Table 2. Differential Diagnosis: Orthodromic AVRT: Narrow complex tachycardia.

Condition	Description	Differentiated by
Atrial fibrillation	• A supraventricular arrhythmia with uncoordinated atrial activation and ineffective atrial contraction	• Irregular atrial activity • No distinct P waves • Irregular R-R intervals • In contrast, AVRT will have regular atrial and ventricular activity with visible P waves
Atrial tachycardia	• An SVT arising from a distinct atrial site (whether automatic or reentrant in mechanism)	• Regular atrial activity; can be greater than ventricular rate • Can be irregular at onset and termination period • Discrete P waves • Can have both short and long RP interval • AVRT can be difficult to distinguish from atrial tachycardia; however, AVRT should have an abrupt onset and termination, which can serve as a clue to diagnosis
Atrial flutter	• Macroreentrant atrial tachycardia that propagates around a fixed entity: • Typical, cavotricuspid isthmus–dependent flutter propagates around the tricuspid valve annulus • Atypical, non–cavotricuspid isthmus–dependent flutter propagates around other entities such as mitral valve or scar tissue in either atria	• Regular, typically fixed, atrial activity in atrial flutter • Atrial rate is greater than ventricular rate at 250 to 330 beats per minute • Sawtooth flutter waves on ECG, negative in leads II, III, aVF, in typical atrial flutter • In contrast, in AVRT, the ventricular and atrial rates should be equal and there should be discrete P waves; sawtooth flutter waves are absent
Multifocal atrial tachycardia	• Irregular SVT with multiple P wave morphologies	• Irregular atrial activity • 3 or more distinct P wave morphologies • In contrast, AVRT is a regular tachycardia with P waves of the same morphology
Typical AVNRT	• A reentrant tachycardia that involves 2 distinct pathways within the AV node with slow antegrade conduction and fast retrograde conduction	• Regular atrial activity • Short RP, less than 90 milliseconds • Inverted P waves may not be visible, usually can be seen at the tail end of the QRS complex (pseudo R wave in V₁, pseudo S wave in inferior leads) • Initiated with sudden PR prolongation after a premature atrial contraction • In contrast, the RP interval is usually more than 90 milliseconds in AVRT

Caption: AVRT, atrioventricular reentrant tachycardia; AVNRT, atrioventricular nodal reentrant tachycardia; SVT, supraventricular tachycardia; aVF, augmented vector, foot.

Data from various references.116

Treatment

Approach to Treatment

The approach to AVRT treatment depends on the presence of symptoms, risk of sudden death, and presence or absence of preexcitation on resting ECG, the latter of which may be unknown at time of first presentation depending on location of the AP
For the patient with AVRT who is hemodynamically unstable (eg, hypotension, acutely altered mental status, chest pain, acute heart failure symptoms, signs of shock), immediate DC (direct current) cardioversion is recommended as the first line of treatment¹⁶¹⁷¹⁸¹⁹²⁰
The general approach to the acute treatment of hemodynamically stable AVRT is stepwise:
- Start with vagal maneuvers, and proceed to pharmacotherapy if not successful
- Cardioversion may be performed if pharmacotherapy fails to terminate tachycardia or patient becomes hemodynamically unstable
Catheter ablation of the AP is recommended as definitive therapy for management of AVRT

Nondrug and Supportive Care

Vagal maneuvers are recommended for acute treatment in hemodynamically stable patients with orthodromic AVRT as first line treatment:¹⁶
- Vagal maneuvers should be done with the patient in supine position
- During Valsalva maneuver, the patient raises intrathoracic pressure by bearing down against a closed glottis for 10 to 30 seconds (equivalent to 30 to 40 mm Hg difference)²¹²²
- Carotid sinus massage may alternatively be performed by applying steady pressure over the right or left carotid sinus for 5 to 10 seconds,²²²³ once the absence of carotid bruit has been confirmed with auscultation
- If one vagal maneuver fails to terminate the tachycardia, switching to another maneuver may be beneficial²¹

Drug Therapy

Acute Management

In hemodynamically stable patients with acute presentation of orthodromic (narrow complex) AVRT in whom vagal maneuvers failed to terminate tachycardia, pharmacotherapy with an AV nodal blocking agent should be attempted¹
- IV adenosine is recommended as the first choice for both diagnostic and therapeutic indications in the setting of a regular SVT due to its efficacy and short half-life¹
  - IV adenosine is 90% to 95% effective for acute termination of orthodromic AVRT¹
  - Before administration, patients should be advised of possible transient symptoms, including flushing, lightheadedness, dizziness, chest pain, or near-syncope
  - Monitor with continuous 12-lead ECG during injection and for a subsequent 1 to 2 minutes
  - Avoid in patients with evidence of preexcitation on resting ECG in sinus rhythm¹
- The following is the dosing recommendation for IV adenosine¹⁶
  - Initial dose of IV adenosine is 6 mg via peripheral IV¹
  - If AVRT terminates, patients should be monitored for recurrence
    - If AVRT recurs, repeat the last effective dose of IV adenosine
    - If AVRT recurs after 3 adenosine doses, it is recommended to switch to a second line AV blocking agent
  - If tachycardia continues despite achieving AV block, this excludes an AV node–dependent mechanism of tachycardia; additional doses would not be beneficial
  - If tachycardia persists and AV block is not achieved, it is recommended to administer adenosine in sequential escalating doses: 12 mg, then 18 mg maximum, if needed⁶
    - If tachycardia persists despite the 18 mg dose, it is recommended to proceed with use of a second line AV blocking agent
- IV diltiazem, verapamil, or β-blockers may be considered for acute treatment of patients with orthodromic AVRT if vagal maneuvers and adenosine fail, provided there is no evidence of preexcitation on resting ECG during sinus rhythm¹⁶
  - IV diltiazem or verapamil effectively terminates 90% to 95% of AVRT episodes in patients without preexcitation on resting ECG²⁴²⁵²⁶²⁷
  - Avoid use of IV β-blockers in the setting of decompensated heart failure⁶
  - IV diltiazem, verapamil, and β-blockers may be considered in those patients with orthodromic AVRT and evidence of preexcitation on resting ECG if the patient’s condition does not respond to other treatment, with the following important precautions:¹
    - Should patient convert to atrial fibrillation during administration, there is a risk of rapid conduction over a manifest AP with degeneration into a malignant ventricular arrhythmia (ie, ventricular tachycardia, ventricular fibrillation); thus, clinician must be prepared to promptly perform electrical cardioversion if rhythm converts with medication administration
IV procainamide or ibutilide can be used for acute treatment of suspected antidromic (wide complex) AVRT and in patients with preexcited atrial fibrillation who are hemodynamically stable¹
- Procainamide and ibutilide slow conduction and prolong refractoriness of the AP, while having minimal effect on the AV node¹²⁸²⁹
- Consult with cardiologist or cardiac electrophysiologist regarding appropriate management
Avoid use of IV amiodarone, IV digoxin, and IV or oral β-blockers, diltiazem, and verapamil for the acute management of patients with preexcited atrial fibrillation due to risk of potential harm¹
- Administration of these medications in this setting can increase ventricular rate and enhance conduction over the AP, thus increasing the risk of life-threatening ventricular arrhythmias¹³⁰³¹³²³³³⁴³⁵

Ongoing Management

For patients with AVRT and an AP who decline or are not candidates for catheter ablation, recommend pharmacotherapy to prevent further arrhythmias and/or slow the ventricular response rate¹
- Oral β-blockers, diltiazem, or verapamil can be used for ongoing management of patients with orthodromic AVRT without preexcitation on their resting ECG¹
- In the absence of coronary or structural heart disease, the class IC antiarrhythmic agents, oral flecainide and propafenone, can be used in patients with AVRT and/or preexcited atrial fibrillation¹
  - Both agents directly slow or block conduction over the AP
  - The effectiveness of these medications reaches 85% to 90%; however, up to 60% of patients have adverse effects, and 20% of patients stop the treatment because of them²⁹³⁶³⁷³⁸³⁹⁴⁰
  - Oral dofetilide and sotalol can be used in those patients with AVRT and/or preexcited atrial fibrillation who have a history of coronary or structural heart disease¹
- Oral amiodarone may be considered for ongoing management of patients with AVRT and/or preexcited atrial fibrillation in whom catheter ablation and other pharmacotherapies are ineffective or contraindicated¹
  - Oral amiodarone therapy has β-blocking activity, can prolong AP repolarization, blocks fast sodium and slow calcium inward currents, and suppresses ectopic beats; the sum effect is slowed conduction over both the AP and AV nodes with chronic administration⁴¹
  - Long-term use of amiodarone is associated with an unfavorable adverse effect profile, which limits its use as a first line agent for ongoing management

Treatment Procedures

Synchronized DC cardioversion should be performed as follows:
- Perform for all hemodynamically unstable patients
- Among hemodynamically stable patients, DC cardioversion is recommended for those in whom acute medical therapy is ineffective or contraindicated¹
  - In hemodynamically stable patients, it should always be performed after adequate sedation or anesthesia has been achieved⁴²
Catheter ablation of the AP is recommended as definitive therapy for management of AVRT¹
- Recommend catheter ablation of the AP in patients with AVRT and preexcited atrial fibrillation¹
- Catheter ablation is recommended in asymptomatic patients with AVRT who have high-risk occupations (eg, drivers, pilots, athletes) or have a high-risk AP identified during EP study¹
- The success rate of catheter ablation of the AP is 93% to 95% and can approach 100% depending on the location of the AP, with risk of major complication of 2.8%⁴³⁴⁴

Persistent or Recurrent Disease

Recurrent arrhythmias involving the AP after ablation procedure are reported in 5% to 12% of patients⁴⁴⁴⁵
- The recurrence rate is higher with ablation of multiple pathways and AP located on the right free wall or the septum⁴⁵⁴⁶
- 50% of recurrences happen during the first 12 hours after the procedure⁴⁶
Repeat ablation usually leads to permanent elimination of AP and arrhythmias associated with it⁴⁶

Admission Criteria

Patients who are hemodynamically unstable due to AVRT should be admitted for inpatient monitoring
Patients who require IV infusions of medication should be admitted for monitoring

Follow-Up

Monitoring

In patients with history of preexcitation on ECG in sinus rhythm, monitor with routine 12-lead ECG for recurrence of preexcitation (ie, recurrence of delta wave)
Ambulatory monitoring may be needed to rule out recurrence of arrhythmias in patients with concealed AP

Complications

Catheter ablation of an AP is a relatively safe procedure with 2.8% overall risk of complications⁴³
- Major complications include:
  - AV block (0.8%) with 0.3% risk of needing a pacemaker
  - Tamponade (0.4%)
  - Stroke (0.1%)
  - Transient ischemic attack (0.2%), in the case of left-sided pathways
- Risk of procedure-related death is 0.1%⁴³

Prognosis

Prognosis of patients with AVRT is favorable, with high success rate of catheter ablation and low recurrence rate⁴³⁴⁴

Referral

Patients with AVRT or evidence of preexcitation should be referred to a cardiac electrophysiologist for further management, risk stratification and, when appropriate, catheter ablation¹

References

1.Page RL et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2016;67(13):e27-e115.