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).
judith mahood says
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).
Shouldn’t it read “if the patient is stable , and you can see a QRS-t complex use (low energy)
Jeff with admin. says
No it should not read that. For the stable patient synchronized cardioversion is not
indicated.
Synchronized cardioversion is indicated for the unstable patient who has unstable tachycardia with a pulse.
Kind regards,
Jeff
Don Marr says
How long do I wait in between increasing amplitude shocks during cardioversion? Is it 2 minutes like defibrillation?
Jeff with admin. says
When cardioverting, there should be an increase in the amplitude of the charge with each successive shock. If cardioversion fails after the first attempt then increase the shock dose in a stepwise fashion.
When cardioverting. The wait time between shocks is minimal. If cardioversion fails then an additional shock at a higher shock dose should be provided without delay.
Kind regards,
Jeff
Eric says
Why do we cardiovert v-tac with a pulse and defib v-tac without a pulse?
Jeff with admin. says
It is well established with in the literature that pulseless ventricular tachycardia has a high conversion rate when defibrillation is used. This is why it continues to be included with the left branch of the cardiac arrest algorithm and is treated with high energy unsynchronize shocks.
Cardioversion is the preferred treatment for monomorphic ventricular tachycardia with a pulse because when defibrillation is used there is a higher likelihood that the patient may be converted into ventricular fibrillation.
The preferred treatment for polymorphic ventricular tachycardia with a pulse is defibrillation. This is because it is unlikely that the defibrillator will synchronize with a ventricular tachycardia that is polymorphic in nature.
Kind regards,
Jeff
Dr. Darshika Gunawardana says
Can you use synchronized cardioversion to ventricular tachycardia
Jeff with admin. says
You can and should use synchronized cardioversion for unstable monomorphic ventricular tachycardia with pulse.
Kind regards,
Jeff
Dr; Essam Elsayed says
what about polymorphic VT either stable or unstable
Jeff with admin. says
Polymorphic ventricular tachycardia will most likely require defibrillation since it will not be possible to sync the rhythm with the defibrillator.
Kind regards, Jeff
Greg says
First…. great site… I’m very impressed and can’t imagine how it could be any better.
I have an interesting question that may not have an answer. Several years ago I was teaching our hospital our defibrillator machine during our annual review. I had the big idea that I would shock myself with our biphasic defibrillator at its lowest setting, 2 joules, to get a sense as to what we do when we shock someone. The jolt took my breath away and I remember crumpling to the floor probably more out of nerves than anything else.
When I looked up joules, I got some formula that made no sense to this layman. Is there anyway to describe how impactful defibrillating at 100 joules compared to 200 joules is to the human body? How about pacing at 50 or 100 milliamperes?
I think this is one of those questions that we never think to ask but is very important if you’re about to be on the receiving end.
Thankyou
Jeff with admin. says
As little as 10 Joules is used for the conversion of atrial fibrillation.
The dose of 2 Joules if given unsynchronized could’ve definitely thrown you into ventricular fibrillation.
The reason why it took your breath away was because your heart probably stopped beating for a second or two.
Electricity no matter the dose when given through a biphasic defibrillator travels directly through the heart.
Cardiac pacing with milliamperes is a minuscule dose compared to 2 Joules.
It would be like comparing 1 mg of epinephrine with 1 microgram.
The equations to understand the difference between Joules and amperes is over my head, but the way that the electricity goes into the body is different.
I’m glad you’re OK. That probably could have killed you if it would’ve been delivered at exactly the right time. Hopefully, if it through you into VF somebody else would’ve seen that and counter shocked you with 200 J.
Kind regards,
Jeff
Annemarie says
I have my advanced life support course coming up and I have found this very useful. I now feel more prepared. Thank you so much.
Gyang Joseph says
If a patient unconscious, breathing and pulseless, what is the best action to be taken.
Jeff with admin. says
If the patient is pulseless you should begin CPR immediately, have someone get an AED or defibrillator and follow the cardiac arrest algorithm.
A patient that is pulseless will never have normal respirations. You might see kussmaul respirations which are sporadic breathes that can occur during cardiac arrest, but you’ll never see normal respirations.
Kind regards,
Jeff
Medgirl says
If the patient is unconscious, and pulseless, the patient is not breathing. You should begin CPR immediately.
sanam gul says
i want to b part of ur conversation n these answers that u people gave all are very usefull for me in my studies…thanks to all of u
Chintha Samarawickrema says
Very good explanation of Synchronized & Unsynchronized Cardioversion! For a long time I had a hard time understanding them properly. Thank you very much, Jeff!
Aurora says
Dear sir,
I just want to ask what will happen if 1 mg of Epinephrine bolus is given to patient with a rhythm of bradycardia?
Another thing,if the rhythm is vfib and synchronized shock is given will the shock be effective? Waiting for your reply
Jeff with admin. says
If epinephrine is given to the patient with bradycardia, this will likely increase the heart rate.
A defibrillator cannot synchronize the ventricular fibrillation. An Unsynchronized shock would need to be given.
Kind regards,
Jeff
Mary Rickard says
Jeff, I always worry when it’s time to renew. This time I feel way more prepared. Great learning tool. I will definitely recommend it to others.
Dr Bijay says
Very nice explanation. Thanks
Komal says
Wonderfull explaination thank u so much …
Dr Satish. N v says
In narrow complex tachycardia. B p not recordable. Breathless. Needs sedation before cardioversion?
Shall I use synchronized cardioversion?
Jeff with admin. says
If the patient has a pulse, you would use synchronized cardioversion. If the patient is pulseless then you would use unsynchronized defibrillation. Kind regards, Jeff
Brendan` says
Narrow complex tachycardia with no pulse would be a PEA. I don’t think you would do an unsynchronized defibrillation of that. You should probably be doing CPR, epinephrine IV, and a fluid bolus…
If the patient is awake in a narrow complex tachycardia, but has an unreadable blood pressure, I don’t think they get the benefit of sedation before synchronized cardioversion. Just a sympathetic, “this is going to hurt, but it is all we can do to try and slow your heart down”.
Jeff with admin. says
Yes Brendan, you are correct. I was mistaken when I answered this question this would be considered PEA. The interventions that you listed are correct.
Thanks so much for the feedback and correction. I do appreciate it.
Kind regards,
Jeff
DR KHURSHID A BABAR says
yes ,synchronized cardioversion is used in all atrial tachy cardia,despite patient is haemodynimacally compromised
Dr; Mahassin Musa says
Yed