ECG criteria
- Record an ECG (preferably a continuous rhythm strip in lead II) before, during, and after the manoeuvre, continuing continuous recording throughout the recovery phase, typically for at least 30 s and longer if persistent bradycardia, pauses, or diagnostic uncertainty remain
- Effect on the sinus node: temporary slowing of sinus rhythm
- Effect on the AV node: prolongation of PQ interval, onset of Mobitz type I second-degree AV block during the manoeuvre
- In AVNRT and AVRT (where the AV node is part of the reentry circuit): abrupt termination of tachycardia and restoration of sinus rhythm ('all or none')
- In atrial flutter and most atrial tachycardias, the atrial arrhythmia usually does not terminate, but AV block increases and atrial activity (F waves, P waves) is unmasked; selected atrial tachycardias may be vagus-dependent and terminate
- In sinus tachycardia: gradual, moderate slowing without termination, followed by a return to baseline rate
- In ventricular tachycardia: ventricular rate and mechanism usually do not change; the manoeuvre does not terminate VT
- Lack of effect does not rule out AVNRT/AVRT — the manoeuvre may have been performed incorrectly
What it looks like on ECG
The effect of a vagal manoeuvre is assessed from a continuous rhythm strip recorded during the manoeuvre and crucially afterwards.
| Rhythm | Response to the manoeuvre |
|---|---|
| Sinus tachycardia | Gradual, moderate slowing of heart rate followed by a smooth return to baseline |
| AVNRT / AVRT (orthodromic) | Abrupt termination of tachycardia ('all or none') with restoration of sinus rhythm, or no effect |
| Atrial tachycardia, atrial flutter | The arrhythmia usually persists, but the degree of AV block increases, revealing P waves or flutter waves between QRS complexes; with typical flutter, sawtooth F waves are often visible in the inferior leads (II, III, aVF), whereas in atypical flutter the morphology and polarity of the waves may differ |
| Atrial fibrillation | Slowing of ventricular rate without restoration of sinus rhythm |
| Ventricular tachycardia | Ventricular rate and VT mechanism generally remain unchanged; atrial activity or the degree of AV conduction may change, but VT is not terminated |
During the Valsalva manoeuvre, the most pronounced vagal slowing and potential termination of supraventricular tachycardia often occur not during the straining phase itself, but immediately after its cessation, during the recovery phase of venous return and blood pressure (reflex bradycardia). Therefore, ECG recording should be continued after the end of the manoeuvre — this is precisely when the effect is frequently maximal.
Mechanism
Elevated pressure in the carotid sinus (mechanical during massage) or changes in intrathoracic and intra-abdominal pressure followed by baroreceptor activation (Valsalva manoeuvre) reflexively enhance vagal tone via the nucleus tractus solitarii in the medulla oblongata. Acetylcholine released from vagal nerve terminals activates muscarinic M2 receptors in the sinus node and especially the AV node, increasing potassium conductance and hyperpolarizing pacemaker cells. This slows spontaneous depolarization of the sinus node and, more importantly for terminating tachycardias, slows and temporarily blocks conduction through the AV node. If the AV node is an obligatory link in the reentry circuit (as in AVNRT and orthodromic AVRT), its block interrupts the circuit.
Types of manoeuvres
- Valsalva manoeuvre — forced expiration against a closed glottis (straining). Standardized technique: strain with an effort generating approximately 40 mmHg of pressure for 15 s in a semi-recumbent position (about 45°); then immediately place the patient flat and passively raise straightened legs to about 45° for another 15 s; after this, return the patient to the starting position and continue monitoring (the modified Valsalva manoeuvre increases the success rate of terminating AVNRT/AVRT compared to the classical approach)
- Carotid sinus massage — pressure applied to the carotid bifurcation on one side (sequentially, never bilaterally at the same time) for 5–10 s, exclusively under continuous ECG and blood pressure monitoring
- Aschner manoeuvre (ocular pressure) — a historical technique, no longer recommended in current practice due to the risk of eye injury
- Facial immersion in cold water, breath-holding — adjunctive techniques, primarily used in children
Differential diagnosis
- Sinus tachycardia: distinguished by a gradual rather than abrupt change in rate and a progressive return to baseline rhythm after the manoeuvre
- Ventricular tachycardia: rate and QRS morphology remain virtually unchanged because the AV node is not part of the tachycardia circuit
- Atrial fibrillation with rapid ventricular response: slowing of the ventricular rate without termination of the arrhythmia; irregularity persists
- True termination of tachycardia (AVNRT/AVRT) versus temporary slowing that unmasks atrial activity (atrial flutter, atrial tachycardia) — the key distinction is whether the arrhythmia itself terminates or only the degree of AV conduction changes.
Clinical significance and management
In a stable patient with regular narrow-complex tachycardia, vagal manoeuvres are the initial intervention, performed before pharmacological therapy; in irregular or wide-complex tachycardia, the evaluation algorithm and electrical/specific therapy should not be delayed. They also serve a diagnostic role: in an unclear regular narrow-complex tachycardia at a high rate, the manoeuvre unmasks atrial activity, helping to differentiate atrial flutter or atrial tachycardia from AVNRT/AVRT without the need for adenosine.
If vagal manoeuvres are ineffective in a regular narrow-complex tachycardia with hemodynamic stability, the next step is intravenous adenosine; if ineffective or contraindicated, verapamil, diltiazem, or a beta-blocker should be used in the absence of contraindications (verapamil and diltiazem are contraindicated in hypotension and decompensated heart failure). Synchronized cardioversion is indicated in the presence of hemodynamic instability. In irregular wide-complex tachycardia with suspected pre-excited AF, adenosine, verapamil, diltiazem, beta-blockers, and digoxin must not be used, and vagal manoeuvres should not be employed as treatment. Expert consultation and management of pre-excited AF are required, with immediate synchronized cardioversion if unstable.
Carotid sinus massage is performed strictly with continuous ECG and blood pressure monitoring, unilaterally, for no more than 5–10 s. It is contraindicated in known significant carotid artery stenosis, previous stroke or transient ischemic attack, or an auscultatory bruit over the carotid artery (a bruit is a reason to withhold the manoeuvre until stenosis is ruled out, not a sign that removes the risk). In patients with digitalis toxicity, recent myocardial infarction, or severe coronary artery disease, manoeuvres should be performed with caution due to the risk of profound bradycardia or asystole. Continuous ECG monitoring and readiness for resuscitation are mandatory in case of a significant pause.
Common interpretation errors
- Failing to record a continuous rhythm strip, resulting in missing the moment of tachycardia termination or unmasking of atrial activity
- Stopping the recording immediately after the manoeuvre ends, even though during the Valsalva manoeuvre the vagal effect is frequently maximal during the recovery phase following straining
- Mistaking a lack of effect for proof of ventricular origin of the tachycardia — incorrect execution technique may be the actual cause
- Confusing a temporary slowing of the ventricular response during atrial flutter with termination of the arrhythmia
- Failing to account for contraindications to carotid sinus massage (carotid bruit, recent stroke) and performing it bilaterally
1. What happens on the ECG during a vagal manoeuvre in a patient with atrial flutter?
The AV node is not part of the reentry circuit in atrial flutter, so the manoeuvre merely slows the ventricular response and unmasks atrial activity, but typically does not terminate the arrhythmia.
2. What is the mechanism underlying the termination of AVNRT by a vagal manoeuvre?
Increased vagal tone via muscarinic receptors slows AV conduction; since the AV node is part of the re-entry circuit in AVNRT, its blockade terminates the tachycardia.
3. Which contraindication limits the performance of carotid sinus massage?
If carotid sinus stenosis or a recent cerebrovascular event is suspected, carotid sinus massage can provoke neurological complications, including ischemic stroke.
Frequently asked questions
How to distinguish the effect of a vagal maneuver in AVNRT from that in atrial flutter?
In AVNRT and AVRT, tachycardia typically terminates completely and abruptly on an "all-or-none" basis, with restoration of sinus rhythm. In atrial flutter and most atrial tachycardias, the AV node is not part of the re-entry circuit, so the maneuver only enhances AV block, slowing the ventricular rate and unmasking flutter waves or P waves, while the arrhythmia itself usually persists.
Are vagal maneuvers dangerous?
The Valsalva maneuver is relatively safe in a stable patient. Carotid sinus massage can cause marked bradycardia, asystole, or neurological complications including ischemic stroke; therefore, it is not performed in significant stenosis/recent stroke or TIA, is performed unilaterally only, for no more than 5–10 s, and with mandatory ECG and BP monitoring.
What to do if a vagal maneuver fails to terminate tachycardia?
Lack of effect does not rule out AVNRT or AVRT; improper technique may be the cause. In regular narrow-complex tachycardia with hemodynamic stability, the next step is intravenous adenosine; if ineffective or contraindicated, verapamil, diltiazem (in the absence of hypotension and decompensated heart failure), or a beta-blocker. Synchronized cardioversion is indicated for instability, and in suspected pre-excited atrial fibrillation, AV nodal blockers and vagal maneuvers are not used.
Can vagal maneuvers be used in wide QRS tachycardia?
Maneuvers are used in regular narrow-complex tachycardia with hemodynamic stability. In wide-complex tachycardia of unclear origin (VT or SVT with aberrancy), maneuvers are less informative and should not delay the standard wide-complex tachycardia evaluation algorithm.
Why is it important to continue ECG recording after the Valsalva maneuver ends?
The maximum vagal effect during the Valsalva maneuver often occurs not during the strain itself, but in the recovery phase afterward, due to reflex bradycardia upon the return of venous return and blood pressure. If the recording is stopped too early, the moment of tachycardia termination may be missed.
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Related terms
More in the section "Criteria, Formulas, Algorithms"
Sources
- Hampton J.R. The ECG in Practice, 2019
- Goldberger A.L. Clinical Electrocardiography: A Simplified Approach, 2017
- ESC Guidelines for the management of patients with supraventricular tachycardia, 2019
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.