Overview #
- Definitions
- “Supraventricular Tachycardia” (SVT) by definition refers to any tachycardia that does not originate in the ventricular tissue.
- However, in practice, SVT most commonly refers to a specific type of tachycardia, Atrioventricular Nodal Reentrant Tachycardia (AVNRT), which has the typical ECG findings that are taught in medical school.
- For the purpose of this guideline, if a patient has a narrow-complex tachycardia, which isn’t one of the following:
- Sinus Tachycardia
- Atrial Fibrillation
- Atrial Flutter
Then it can be considered an SVT and investigated/managed in the same way.
- Prioritisation
- Immediate – Call a MET call
- Key points
- While the high HR can be alarming, most SVT is well tolerated by patients. However, immediate attention is required to confirm the diagnosis and rule out more sinister rhythms
- Vagal manoeuvres are quick, easy and safe to try – even if the diagnosis is unclear. They can also help differentiate true SVT from mimicking conditions
- Adenosine is generally the mainstay of treatment. DC cardioversion is rarely required
- Nonetheless, the management of any arrhythmia with haemodynamic instability, acute heart failure or syncope is immediate cardioversion
Triage #
While SVT is only a rare cause of cardiac arrest, it can precipitate adverse features especially in at-risk groups (eg. PHx of heart disease) and should be attended to promptly.
Immediate Attention
In most cases, episodes of SVT will have a heart rate within MET call criteria, and should require immediate attention
Within 30 min
Any new tachycardia (HR > 120) that has been detected (either on routine observations or clinical examination) should have an ECG performed and reviewed in order to identify the type of tachycardia
Escalation
Arrhythmias of any kind can be very overwhelming to deal with, and often involve the use of medications that aren’t prescribed often on the wards (eg. adenosine, IV beta blockers, etc.)
Have a very low threshold to escalate to a MET Call
Causes #
In general, the pathogenesis of tachyarrhythmias involves underlying structural changes to the heart, and a precipitant that triggers an episode
However, it should be noted that generally SVTs are NOT associated with structural heart disease, and are often reasonably benign
Underlying Factors:
- No other underlying heart disease*
- Structural Heart Disease (valvular, cardiomyopathy, etc.)
- Ischaemic Heart Disease
- Chronic HTN
- Previous Heart Surgery/Ablation Therapy
Precipitants:
- No clear precipitant*
- Electrolyte Imbalances (especially K+ and Mg2+)
- Anaemia
- Hypoxia
- Hyperthyroidism
- Medications
- Acute Coronary Syndrome (ACS)
- Alcohol, Tobacco and Illicit Drugs
- Pregnancy
- Stress (Physiological, Emotional)
* SVTs commonly occur in healthy individuals, and with no clear precipitant
Clinical features #
Any patient with the following symptoms might have an arrhythmia, and an ECG should attempt to be captured during the episode of symptoms:
- Palpitations – in 98%†
- Dizziness – in 78%†
- Dyspnea – in 47%†
- Chest pain – in 38%†
- Syncope – in 16%†
† These percentages are representative of symptoms in AVNRT (3)
The most common symptom is palpitations – and patients with SVTs often experience a rapid onset and later, a sudden termination
Syncope is uncommon and usually only present with HR > 170, or underlying heart disease. (3). Syncope associated with tachycardia is more concerning for Ventricular Tachycardias
Diagnosis #
AVNRT:
The typical ECG findings include: (2)
- Narrow§ QRS Complex
- HR > 120 and Regular
- P waves not visible (often buried within QRS complexes)
(6)
§ While AVNRT can be wide-complex in the presence of a Bundle Branch Block, as a general rule, any wide-complex tachycardia should be TREATED AS VENTRICULAR TACHYCARDIA$ unless directed otherwise
Other Forms of SVT:
- Narrow QRS Complex
- HR > 120 and Regular
- P waves appear abnormal (eg. short, peaked, inverted) but not consistent with Atrial Flutter
(7)
Differential Diagnosis #
The following are common patterns to rule out as they have different management:
Sinus Tachycardia
- Narrow QRS Complex
- HR >120 and Regular
- Normal P waves
Sinus Tachycardia (ST) can be difficult to differentiate from SVT – When the HR is >140 the P-waves may get buried in the preceding T-wave, and the ECG appears similar. In such cases, vagal maneuvers (detailed below) may help differentiate the two (4)
ST is crucial to rule out, as it is generally a physiological response to another illness and is used by the body as a coping mechanism. Slowing down ST with medication can be harmful to the patient (4)
NOTE: ST is highly unlikely if HR > 150}}
Atrial Flutter
- Narrow QRS Complex
- HR > 120 (often HR = 150) and Regular
- Flutter waves
(8)
Atrial Flutter may mimic SVTs at fast heart rates, as characteristic flutter waves may not be visible. A HR very close to 150 is often a clue to Atrial Flutter, and as above, vagal maneuvers should also be performed
Atrial Fibrillation #
- Narrow QRS Complex
- HR is irregularly, irregular
- No visible p-waves and fluctuating baseline
(9)
The key distinguishing feature of Atrial Fibrillation (AF) is its irregularly, irregular rhythm. However, at very fast heart rhythms it can almost appear regular. Again, vagal maneuvers will help in this scenario
Other RhythmsWith the 3x mimics above ruled out, any other narrow-complex, regular tachycardias can be safely treated with the management algorithms below. (1)
Investigations #
Initial Investigations
| Investigation | Significance |
| ECG | A 12-lead ECG is necessary to correctly diagnose the rhythm (and identify any other relevant ECG changes) |
| VBG | A VBG can give quick information about potential precipitants (eg. hyperkalaemia, lactate indicating stress, etc.) |
Further Investigations
| Investigation | Significance |
| FBE | Identify anaemia or infection as precipitants |
| UEC, CMP | Replace any electrolytes. K+ and Mg2+ are of particular importance |
| CRP | Can be considered depending on clinical picture |
| Troponin | ACS is an uncommon precipitant of SVTs. Often tachycardia causes rate-related ischaemia which will prompt a small troponin rise (rather than an underlying ACS) |
| bHCG# | Pregnancy can precipitate SVT |
| CXR# | Consider if patient has chest pain (as part of standard chest pain protocols) |
Management – with adverse features #
In all patients with SVT and adverse features, there should be an immediate MET call, and the following should be prepared for: (5)
| 1st Line | Immediate Synchronized DC CardioversionAttempt up to 3 times |
| 2nd Line | Amiodarone 300mg IV, over 10-20 minutesThen, repeat synchronized DC Cardioversion |
Adverse features are defined as any of the following:
- Shock
- Syncope
- New signs of Heart Failure
- Signs of Myocardial Ischaemia
If unsure, the safest option is to get senior help.
While preparations for DC Cardioversion are in progress, the below management options can be attempted.
Management – no adverse features #
In the stable patient, there is a clear stepwise approach: (5)
| 1st line | Vagal Manoeuvre |
| 2nd line | Adenosine 6mg IV stat If no response, Adenosine 12mg IV statIf still no response, Adenosine 12mg IV statContraindication – Severe Asthma |
| 3rd Line# | IV Beta Blockers (eg. Metoprolol IV 2.5 – 5mg, every 10 minutes, to maximum 15mg)or IV Calcium Channel Blockers |
Vagal Maneuvers
These include the following:
- Valsalva Maneuver – The easiest way for patients to perform this is by blowing against a closed syringe
- Standard Valsalva Manoeuvre: With the patient in a semi-recumbent position, ask them to blow into a 10mL syringe for 15 seconds. The patient needs to blow with enough force to move the plunger
- Modified Valsalva Manoeuvre: Perform the above manoeuvre. Immediately after, simultaneously lie the patient supine and raise the patient’s legs to 45 degrees. Hold this position for 15 seconds.
(This was found to increase the success of the manoeuvre up to 43% from 17% in one RCT. Please see the video attached to the bottom of the reference (10))
- Carotid Sinus Massage – Best avoided in the elderly as there is a theoretical risk of stroke/TIA if patient has carotid sinus atherosclerosis
As mentioned above, Vagal Maneuvers are useful even if the exact rhythm is unclear, as they may (transiently) slow down the heart rate and hence help unmask the true rhythm
Adenosine
Adenosine is administered via rapid push, with the following considerations:
- Ensure this is supervised by a senior clinician (eg. a Registrar)
- Ensure the patient has continuous ECG monitoring and defibrillator pads on in case of any complications
- Patients should be warned of ‘face flushing’ and a ‘doom-like’ feeling after administration
IV Beta Blockers/Calcium Channel BlockersOnly with the guidance of senior clinicians
Management – follow up #
After the acute event, it is important to review the investigations from earlier and address any reversible risk factors. This will hopefully prevent any further episodes of SVT
It is reasonable to refer all patients with SVT to cardiology for outpatient follow-up. Patients with recurring symptoms might benefit from further investigations, and/or chronic management
References #
(1) Prutkin JM. Overview of the acute management of tachyarrhythmias. In: Hoekstra J, Calkins H, Dardas TF, editors. UpToDate. [Internet]. Waltham (MA): UpToDate Inc; 2017. [updated 2020 Jan 3; cited 2021 Sep 16]. Available from: https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias
(2) Ganz LI. Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation. In: Knight BP, Goldberger AL, Hoekstra J, Dardas TF, editors. UpToDate. [Internet]. Waltham (MA): UpToDate Inc; 2017. [updated 2020 Jan 17; cited 2021 Sep 16]. Available from: https://www.uptodate.com/contents/narrow-qrs-complex-tachycardias-clinical-manifestations-diagnosis-and-evaluation
(3) Knight BP. Atrioventricular nodal reentrant tachycardia. In: Link MS, Yeon SB, editors. UpToDate. [Internet]. Waltham (MA): UpToDate Inc; 2017. [updated 2020 Oct 26; cited 2021 Sep 16]. Available from: https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia
(4) Homoud MK. Sinus tachycardia: Evaluation and management. In: Piccini J, Yeon SB, editors. UpToDate. [Internet]. Waltham (MA): UpToDate Inc; 2017. [updated 2020 Mar 12; cited 2021 Sep 16]. Available from: https://www.uptodate.com/contents/sinus-tachycardia-evaluation-and-management
(5) Australian Resuscitation Council. Guideline 11.9: Managing Acute Dysrhythmias [Internet]. Australia: ARC; 2009 [cited 2021 Sep 16]. Available from: https://resus.org.au/guidelines/
(6) Health and Willness. Vagal Maneuvers: How to Stop your Patient’s SVT [Internet]. [place unknown]: Health and Willness; 2021 [update 2021 Mar 15; cited 2021 Sep 16]. Available from: https://healthandwillness.org/vagal-maneuvers-for-svt/
(7) LITFL. Supraventricular Tachycardia (SVT) [Internet]. [place unknown]: LITFL; 2021 [update 2021 Mar 8; cited 2021 Sep 16]. Available from: https://litfl.com/supraventricular-tachycardia-svt-ecg-library/
(8) PracticalClinicalSkills. Sinus Tachycardia | Reference Guide [Internet]. Westborough, MA: Clinical Skills Education; 2021 [cited 2021 Sep 16]. Available from: https://www.practicalclinicalskills.com/ekg-reference-details/2/sinus-tachycardia
(9) PracticalClinicalSkills. Atrial Fibrillation | Reference Guide [Internet]. Westborough, MA: Clinical Skills Education; 2021 [cited 2021 Sep 16]. Available from: https://www.practicalclinicalskills.com/ekg-reference-details/11/atrial-fibrillation
(10) Appelboam A, Reuben A, Mann C, Gagg J, Ewings P, Barton A et al. Postural modification to the standard Valsalva manoeuvre for emergency treatment of supraventricular tachycardias (REVERT): a randomised controlled trial. The Lancet [Internet]. 2015 [cited 11 October 2021];386(10005):1747-1753. Available from: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)61485-4/fulltext
Contributors
Reviewing Consultant/Senior Registrar
Dr Daniel Shell
Dr Anita Ng
