Patients hate adenosine, it makes them feel like they are going to die. With diltiazem patients just feel the SVT stop.
In the podcast that goes with this post I have a recording of one of our midwives who has recurrent SVT. She was very happy afer dilitazem and I don’t think you could get adenosine into her again.
Treatment of SVT
Start with vagal manoeuvres eg get the patient to lie flat and blow into a syringe with the plunger in it, lift the patient’s legs in the air as the patient finishes their expiration. It is the rush of blood to the heart as the intrathoracic pressure drops and you lift the legs that in creases the cardiac output, stimulating the carotid stretch receptors and causes the vagal response.
Carotid sinus massage if the patient isn’t an arteriopath or say over 60.
Ice cold flannel of water in the face.
If these don’t work (all of them do work sometimes and are worth trying even though we love playing with drugs) then we go to medication.
Typically in an adult I’ll give a 20mg push of diltiazem. This can be repeated after 5 minutes if needed. The blood pressure may drop but this is almost never symptomatic.
Some backwards countries like Australia still don’t have IV diltiazem. Slow IV verapamil is a good alternative there. I use diltiazem rather than verapamil because it is the drug we are more familiar with as we use it frequently for rate control in AF.
Any antiarrhythmic, including adenosine, can cause cardiac arrest. Be ready to start CPR if this happens – treat as per PEA arrest algorithm.
Caution in a patient with heart failure or hypotension – get a senior help. Adenosine or electricity may be better options, or the patient may need preloading with IV calcium and or IV fluid.
Talk to a paediatrician before treating an SVT in a baby.
Don’t use adenosine or a calcium channel blocker (verapamil or diltiazem) to treat an irregular wide complex tachycardia as this may be Wolff-Parkinson-White Syndrome (WPW) with atrial fibriallation. Just about any drug you through at this may stop the slow pathway and just leave the fast pathway active and may lead to VF and death. Electricity is the best option for these patients.
The various terms for SVTs can be confusing.
SVT means a supraventricular tachycardia which technically includes sinus tachycardia, AF, atrial flutter and atrial reentry tachycardias + others.
In day to day use however SVT means a paroxysmal SVT with sudden, usually unprovoked, onset. It may be due to atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT) or atrial tachycardia, which is all very confusing. So we just use the term SVT.
See the table of relevant terms and definitions from the 2015 ACC/AHA/HRS guidelines at the bottom of the page.
What we call SVTs tend to be regular, narrow complex, have no P waves, sudden and spontaneous onset, rapid heart rate. Usually the patient is aware of it and they can be just be annoying or can leave the patient feeling quite faint and occassionally cause chest pain. Patients tend to be in their late teens to 30s.
Always consider could this patient have a sinus tachycardia with p waves hidden in the preceding T waves. Is this patient actually sick from something else like sepsis or rheumatic fever.
A very useful technique to sort out SVT from sinus tachycardia is to watch the monitor. An SVT will stay and the same rate +/- a few beats/minute. A sinus tachycardia will vary 10-20 beats per minute as the patient moves, holds their breath etc.
ST depression in SVT
As far as we know this has no significance – ignore it. It does not mean the patient has failed an SVT stress test.
Regular wide complex SVT
Rarely we will see patients with a prexisting bundle branch block who go into an SVT. This can be confusing. The complexes tend to have the same morphology as typical bundle branch block so a LBBB will have a wide S wave in V1 and wide tall R waves in V6 rather than fairly similar looking complexes across the ECG in VT.
If in doubt and the patient is shocked cardiovert for presumed VT.
Be nice to your patients – give diltiazem for SVTs
Song on Podcast
Zhaba by DakhaBrakha
|Supraventricular tachycardia (SVT)
||An umbrella term used to describe tachycardias (atrial and/or ventricular rates in excess of 100 bpm at rest), the mechanism of which involves tissue from the His bundle or above. These SVTs include inappropriate sinus tachycardia, AT (including focal and multifocal AT), macroreentrant AT (including typical atrial flutter), junctional tachycardia, AVNRT, and various forms of accessory pathway-mediated reentrant tachycardias. In this guideline, the term does not include AF.
|Paroxysmal supraventricular tachycardia (PSVT)
||A clinical syndrome characterized by the presence of a regular and rapid tachycardia of abrupt onset and termination. These features are characteristic of AVNRT or AVRT, and, less frequently, AT. PSVT represents a subset of SVT.
|Atrial fibrillation (AF)
||A supraventricular arrhythmia with uncoordinated atrial activation and, consequently, ineffective atrial contraction. ECG characteristics include: 1) irregular atrial activity, 2) absence of distinct P waves, and 3) irregular R-R intervals (when atrioventricular conduction is present). AF is not addressed in this document.
||Rhythm arising from the sinus node in which the rate of impulses exceeds 100 bpm.
| • Physiologic sinus tachycardia
||Appropriate increased sinus rate in response to exercise and other situations that increase sympathetic tone.
| • Inappropriate sinus tachycardia
||Sinus heart rate >100 bpm at rest, with a mean 24-h heart rate >90 bpm not due to appropriate physiological responses or primary causes such as hyperthyroidism or anemia.
|Atrial tachycardia (AT)
| • Focal AT
||An SVT arising from a localized atrial site, characterized by regular, organized atrial activity with discrete P waves and typically an isoelectric segment between P waves. At times, irregularity is seen, especially at onset (“warm-up”) and termination (“warm-down”). Atrial mapping reveals a focal point of origin.
| • Sinus node reentry tachycardia
||A specific type of focal AT that is due to microreentry arising from the sinus node complex, characterized by abrupt onset and termination, resulting in a P-wave morphology that is indistinguishable from sinus rhythm.
| • Multifocal atrial tachycardia (MAT)
||An irregular SVT characterized by ≥3 distinct P-wave morphologies and/or patterns of atrial activation at different rates. The rhythm is always irregular.
| • Cavotricuspid isthmus–dependent atrial flutter: typical
||Macroreentrant AT propagating around the tricuspid annulus, proceeding superiorly along the atrial septum, inferiorly along the right atrial wall, and through the cavotricuspid isthmus between the tricuspid valve annulus and the Eustachian valve and ridge. This activation sequence produces predominantly negative “sawtooth” flutter waves on the ECG in leads 2, 3, and aVF and a late positive deflection in V1. The atrial rate can be slower than the typical 300 bpm (cycle length 200 ms) in the presence of antiarrhythmic drugs or scarring. It is also known as “typical atrial flutter” or “cavotricuspid isthmus–dependent atrial flutter” or “counterclockwise atrial flutter.”
| • Cavotricuspid isthmus–dependent atrial flutter: reverse typical
||Macroreentrant AT that propagates around in the direction reverse that of typical atrial flutter. Flutter waves typically appear positive in the inferior leads and negative in V1. This type of atrial flutter is also referred to as “reverse typical” atrial flutter or “clockwise typical atrial flutter.”
| • Atypical or non–cavotricuspid isthmus–dependent atrial flutter
||Macroreentrant ATs that do not involve the cavotricuspid isthmus. A variety of reentrant circuits may include reentry around the mitral valve annulus or scar tissue within the left or right atrium. A variety of terms have been applied to these arrhythmias according to the re-entry circuit location, including particular forms, such as “LA flutter” and “LA macroreentrant tachycardia” or incisional atrial re-entrant tachycardia due to re-entry around surgical scars.
||A nonreentrant SVT that arises from the AV junction (including the His bundle).
|Atrioventricular nodal reentrant tachycardia (AVNRT)
||A reentrant tachycardia involving 2 functionally distinct pathways, generally referred to as “fast” and “slow” pathways. Most commonly, the fast pathway is located near the apex of Koch’s triangle, and the slow pathway inferoposterior to the compact AV node tissue. Variant pathways have been described, allowing for “slow-slow” AVNRT.
| • Typical AVNRT
||AVNRT in which a slow pathway serves as the anterograde limb of the circuit and the fast pathway serves as the retrograde limb (also called “slow-fast AVNRT”).
| • Atypical AVNRT
||AVNRT in which the fast pathway serves as the anterograde limb of the circuit and a slow pathway serves as the retrograde limb (also called “fast-slow AV node reentry”) or a slow pathway serves as the anterograde limb and a second slow pathway serves as the retrograde limb (also called “slow-slow AVNRT”).
||For the purpose of this guideline, an accessory pathway is defined as an extranodal AV pathway that connects the myocardium of the atrium to the ventricle across the AV groove. Accessory pathways can be classified by their location, type of conduction (decremental or nondecremental), and whether they are capable of conducting anterogradely, retrogradely, or in both directions. Of note, accessory pathways of other types (such as atriofascicular, nodo-fascicular, nodo-ventricular, and fasciculoventricular pathways) are uncommon and are discussed only briefly in this document (Section 7).
| • Manifest accessory pathways
||A pathway that conducts anterogradely to cause ventricular pre-excitation pattern on the ECG.
| • Concealed accessory pathway
||A pathway that conducts only retrogradely and does not affect the ECG pattern during sinus rhythm.
| • Pre-excitation pattern
||An ECG pattern reflecting the presence of a manifest accessory pathway connecting the atrium to the ventricle. Pre-excited ventricular activation over the accessory pathway competes with the anterograde conduction over the AV node and spreads from the accessory pathway insertion point in the ventricular myocardium. Depending on the relative contribution from ventricular activation by the normal AV nodal/His Purkinje system versus the manifest accessory pathway, a variable degree of pre-excitation, with its characteristic pattern of a short P-R interval with slurring of the initial upstroke of the QRS complex (delta wave), is observed. Pre-excitation can be intermittent or not easily appreciated for some pathways capable of anterograde conduction; this is usually associated with a low-risk pathway, but exceptions occur.
| • Asymptomatic pre-excitation (isolated pre-excitation)
||The abnormal pre-excitation ECG pattern in the absence of documented SVT or symptoms consistent with SVT.
| • Wolff-Parkinson-White syndrome
||Syndrome characterized by documented SVT or symptoms consistent with SVT in a patient with ventricular pre-excitation during sinus rhythm.
|Atrioventricular reentrant tachycardia (AVRT)
||A reentrant tachycardia, the electrical pathway of which requires an accessory pathway, the atrium, atrioventricular node (or second accessory pathway), and ventricle.
| • Orthodromic AVRT
||An AVRT in which the reentrant impulse uses the accessory pathway in the retrograde direction from the ventricle to the atrium, and the AV node in the anterograde direction. The QRS complex is generally narrow or may be wide because of pre-existing bundle-branch block or aberrant conduction.
| • Antidromic AVRT
||An AVRT in which the reentrant impulse uses the accessory pathway in the anterograde direction from the atrium to the ventricle, and the AV node for the retrograde direction. Occasionally, instead of the AV node, another accessory pathway can be used in the retrograde direction, which is referred to as pre-excited AVRT. The QRS complex is wide (maximally pre-excited).
|Permanent form of junctional reciprocating tachycardia (PJRT)
||A rare form of nearly incessant orthodromic AVRT involving a slowly conducting, concealed, usually posteroseptal accessory pathway.
||AF with ventricular pre-excitation caused by conduction over ≥1 accessory pathway(s).
References / further reading
Atrioventricular nodal reentrant tachycardia from EM Core Content
Verapamil for SVT from the Rage Podcast 2014
A debate on the safety of verapamil in children from the Rage Podcast 2014
Cochrane review of calcium channel blockers vs adenosine for SVT from 2007
2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia Adenosine level I evidence, calcium channel blockers level IIa only. “Intravenous beta blockers, diltiazem, or verapamil are reasonable for acute
treatment in hemodynamically stable patients with AVNRT”
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