Ever wondered what the difference between synchronized and unsynchronized cardioversion is?
Synchronized cardioversion is a LOW ENERGY SHOCK that uses a sensor to deliver electricity that is synchronized with the peak of the QRS complex (the highest point of the R-wave). When the “sync” option is engaged on a defibrillator and the shock button pushed, there will be a delay in the shock. During this delay, the machine reads and synchronizes with the patients ECG rhythm. This occurs so that the shock can be delivered with or just after the peak of the R-wave in the patients QRS complex.
Synchronization avoids the delivery of a LOW ENERGY shock during cardiac repolarization (t-wave). If the shock occurs on the t-wave (during repolarization), there is a high likelihood that the shock can precipitate VF (Ventricular Fibrillation).
The most common indications for synchronized cardioversion are unstable atrial fibrillation, atrial flutter, atrial tachycardia, and supraventricular tachycardias. If medications fail in the stable patient with the before mentioned arrhythmias, synchronized cardioversion will most likely be indicated.
Unsynchronized cardioversion (defibrillation) is a HIGH ENERGY shock which is delivered as soon as the shock button is pushed on a defibrillator. This means that the shock may fall randomly anywhere within the cardiac cycle (QRS complex). Unsynchronized cardioversion (defibrillation) is used when there is no coordinated intrinsic electrical activity in the heart (pulseless VT/VF) or the defibrillator fails to synchronize in an unstable patient.
For cases where electrical shock is needed, if the patient is unstable, and you can see a QRS-t complex use (LOW ENERGY) synchronized cardioversion. If the patient is pulseless, or if the patient is unstable and the defibrillator will not synchronize, use (HIGH ENERGY) unsynchronized cardioversion (defibrillation).
JD says
for unstable patients with polymorphic vtach that still has pulse, do we prefer unsynchronized cardioversion?
ACLS says
Synchronization can be attempted for a few moments. If unable to synchronize, then unsynchronized cardioversion would be performed.
Kind regards,
Jeff
Jess says
What if SVT or afib is refractory to highest dose of synchronized cardioversion, do you continue to cardiovert at 360
ACLS says
If supraventricular tachycardia or atrial fibrillation is refractory to the highest dose of synchronized cardioversion, it’s important to consult with an expert. Continuing to cardiovert at 360 joules might not be the best approach, as there could be underlying causes or conditions that need to be addressed. Alternative treatments or interventions may be considered, such as medication adjustments, catheter ablation, or other specialized procedures. An expert in the field would be able to better determine next steps.
Kind regards,
Jeff
Lucas Nzobendo says
Greatefull narrations!
Patricia Baker says
It is understandable and easy format. Thanks
ACLS says
Hi Patricia,
Glad to help. I’m glad that you found it helpful. Kind regards, Jeff
B.ELKHIDER says
pt receive 2 shocks and still in v tach what is next
Zach says
If you sync cardioversion Pulsing V-Tach and the patient is still in pulsing V-Tach, what is the next action you do after you deliver your second sync cardioversion dose and the patient is still in pulsing V-tach? Do you skip the first does of epi and go straight to Amioderone?
ACLS says
You would be using the tachycardia with a pulse algorithm. Epinephrine is not given in this algorithm. Amiodarone would be the next option.
Kind regards,
Jeff
Noor Makadma says
Thanks for the very informative review.
Can you please explain briefly what is the difference between monophasic and biphasic synchronisation ?
Thanks in advance.
ACLS says
Monophasic uses direct current which passes in one direction from one paddle to the next. Biphasic defibrillation, alternates the direction of the pulses and requires less energy for the same effect.
Most biphasic defibrillators have a first shock success rate that is significantly higher than monophasic defibrillators. Roughly 20% higher success with biphasic. Here is a study
Biphasic defibrillation significantly decreases the energy level necessary for successful defibrillation, decreasing the risk of burns and myocardial damage.
Kind regards,
Jeff
Gerry Probasco says
Very informative and easily understandable been recertifying since 1989. Thanks
ACLS says
Hi Gerry,
Thanks so much! Kind regards, Jeff
Kathleen Braico MD says
I am not sure I would be able to tell atrial flutter with hi capture rate (with ventricular response >180) from SVT on an EKG, can you help me tell the difference? Thanks
ACLS says
Differentiating between atrial flutter with a rapid ventricular response and SVT can be challenging. The easiest and safest method for differentiating when the patient is stable would be to perform vagal maneuvers or administer adenosine per the AHA ACLS protocol.
When you slow the rate with vagaries maneuvers or adenosine, you will see the flutter waves if you are dealing with atrial flutter.
Without slowing and simply looking at the ekg, differentiation may often be impossible.
Kind regards, Jeff
mike says
Hey there Jeff, in regards to syncing v tach. In the midst of a cardiac arrest setting, should a pulse check be completed on seeing VT on the monitor? What are the odds of achieving ROSC with VT? Is there evidence that pulsing VT in the midst of a code is a life sustaining, perfusing rhythm, that can achieve ROSC? There has been some debate here on performing a pulse check upon seeing VT to sync the monitor if it does happen to be pulsing in the middle of a code, or rather continue with a pulseless arrest algorithm, thus limiting pulse checks to any other organized rhythms that are NOT in fact shockable. Hope this is clear enough to provide an answer.
Thanks!
ACLS says
There is ongoing debate about this issue. Typically, ventricular tachycardia will not produce an effective perfusing rhythm and so it is the opinion of most that a pulse check is not necessary if a rhythm change from a non-perfusing rhythm is ventricular tachycardia.
The debate really comes down to the determination of whether to provide an unsynchronized shock or a synchronized shock.
As a rule, Ventricular tachycardia does not produce an effective perfusing rhythm and unsynchronized cardioversion is the method of choice for treating pulseless ventricular tachycardia. In my professional opinion, it would therefore be prudent to provide a rapid unsynchronized shock. If an AED were being used, the AED would instruct to provide a shock and therefore it seems logical that this would be the preferred method of choice and the pulse check would not be necessary. Kind regards, Jeff
Nikita says
In monomorphic and polymorphic vt which one should be treated with synchronised cardioversion? And why?
ACLS says
Monomorphic ventricular tachycardia is treated with synchronized cardioversion. Synchronization avoids the delivery of a LOW ENERGY shock during cardiac repolarization (t-wave). If the shock occurs on the t-wave (during repolarization), there is a high likelihood that the shock can precipitate VF (Ventricular Fibrillation).
Kind regards,
Jeff
Ray says
Dear Jeff,
Repeating my original question as I didn’t get an answer. I will be more explicit – I contend that the only reason we still treat VT with a pulse & pulseless VT differently is that we have not changed our practice to fit in with modern defibrillators. The old defib machines (particularly the monophasic ones) used to take so long to charge up and then sync that there was too much of a delay in treating pulseless VT. That is not the case anymore.
It is well established that delivering a shock on the T-wave rather than the R-wave can cause VF. This is the basis of synchronised shocks.
Why should our ability to detect a pulse have an impact on the electrical treatment of VT?
Modern defib machines are quick to charge, have sync buttons and we can monitor the ecg through the pads. Why not use synchronisation for all patients with VT, regardless of whether a pulse can be detected?
All the best
Ray
ACLS says
I agree that our ability to detect a pulse should not impact the electrical treatment of VT. That being said, both synchronize cardioversion and defibrillation have a fairly high success rate for conversion of VT. I have not seen a good rationale for continuing with no synchronization for pulseless VT.
In these situations, a physician does have the discretion to attempt synchronization. Healthcare providers are allowed to tailor their actions using their discretion for the best outcome.
Kind regards,
Jeff
Ignacy says
Once you deliver unsynch shock to VT is there a chance for conversion to VF? If so why should we create a risk of VF not trying to synchronize the shock in any VT? Pulse has nothing to do, I presume, as you may feel the pulse while I can not… Is the patient pulseless?
Jeff with admin. says
The research and clinical data from the past 70 years indicates that the most effective intervention for pulseless ventricular tachycardia is and unsynchronized shock. This is what should be performed if no pulse is felt and a patient is unresponsive. After the unsynchronized shock, chest compressions should begin immediately. If VF is present when a rhythm check is performed after 2 min. of chest compressions you would perform an unsynchronized shocker the treatment of the VF.
Healthcare providers may tailor the interventions to best suit the scenario that is before them, and if a physician thought that synchronized cardioversion should be attempted in a pulseless state he would need to provide justification his reason. Let the weight of research and clinical data guide your interventions.
Kind regards,
Jeff
Pumlani says
When heart rate is 230 PT is unstable pulseless on peripheral, central you cannot feel properly, must I deffibrilate with unsychronised or achy?
Jeff with admin. says
If the patient is unresponsive and pulseless with a narrow complex tachycardia you would use the right branch of the cardiac arrest algorithm. Neither defibrillation North synchronize cardioversion would be indicated. (it would be very important to determine the cause in this situation.)
If the patient is unresponsive and pulseless with a wide complex tachycardia you would use the left branch of the cardiac arrest algorithm. Defibrillation would be indicated.
If the patient is not unresponsive, but unstable with a narrow complex tachycardia you would perform synchronized cardioversion.
Kind regards,
Jeff
DCW CHUNG says
Defibrillate pulseless vt but cardiovert vt with a pulse. Why the difference?
Jeff with admin. says
There are a couple of reasons for this.
First, pulseless ventricular tachycardia degenerates fairly rapidly into ventricular fibrillation and there is a high likelihood that synchronization will not be possible with pulseless ventricular tachycardia. In light of this, defibrillation is recommended over attempting synchronized cardioversion when the ventricular tachycardia is pulseless.
Second, the body of literature that is available indicates that defibrillation is quite effective for pulseless ventricular tachycardia, and therefore, defibrillation is recommended for pulseless ventricular tachycardia.
Kind regards,
Jeff
Ray says
Dear Jeff,
It is well established that delivering a shock on the T-wave rather than the R-wave can cause VF. This is the basis of synchronised shocks.
Why should our ability to detect a pulse have an impact on the electrical treatment of VT?
Modern defib machines are quick to charge, have sync buttons and we can monitor the ecg through the pads. Why not use synchronisation for all patients with VT, regardless of whether a pulse can be detected?
All the best
Ray
emergency_training_center says
Thankyou for a very informative and well written , easy to read site. I have been doing this fo rover 20 years and its great to see a different way of looking at rythms, and am glad I have still learnt a few things. Keep up the great work