Why sync cardioversion

Electrical current or shocks delivered to the chest to terminate ventricular fibrillation VF was first reported in the s. The delivery of an electrical shock results in simultaneous depolarization of the myocardium making the heart refractory to the ongoing disordered electrical activity. This allows for the interruption of the underlying malignant rhythm and reestablishment of the normal electrical rhythm of the heart.

In the case of tachyarrhythmias where the rhythm is organized and the patients have a palpable pulse, an electrical shock is given as a synchronized cardioversion. Cardioversion refers to the delivery of an electrical shock that is timed to the peak of the R wave on the EKG.

This synchronization ensures that the electrical stimulation occurs only during the refractory period of the cardiac cycle minimizing the risk of iatrogenic arrhythmias. The literature on cardioversion can be confusing as many alternate terms such as external cardioversion, synchronized cardioversion, DC cardioversion, and transthoracic DC cardioversion are used interchangeably. Traditionally monophasic waveform cardioverters were used until the introduction of biphasic waveform cardioversion in the mids.

Increasingly more cardioverters in the ICU are biphasic. Biphasic waveform cardioversion is safe and as equally effective as monophasic cardioversion, using much lower energy with reduced post-shock complications such as cardiac dysfunction, dysrhythmias, and skin burns. Other unstable tachyarrhythmias with intact pulses where cardioversion has been demonstrated to be effective include atrial flutter, atrial ventricular nodal reentrant tachycardia AVNRT , atrial ventricular reentrant tachycardia AVRT with pre-excitation pathways and monomorphic regular ventricular tachycardia.

These are fatal arrhythmias that require prompt recognition and early correction by administration of electrical shock. In these circumstances, defibrillation therapy would take precedence over all other treatments being provided to the ICU patient except when providing the initial cycles of CPR prior to shock delivery per ACLS protocol or establishing an adequate airway when hypoxemia due to an inadequate airway is causing the arrhythmia.

The parameters for defining an unstable arrhythmia as mentioned in the advanced cardiovascular life support guidelines includes any arrhythmia that is causing hypotension, altered mental status, signs of shock, ischemic chest discomfort or acute heart failure. However, ICU patients are frequently admitted with similar symptoms as part of their primary critical illness.

In such situations, unstable supraventricular tachyarrhythmias benefit from individualized therapy such as inotrope and vasopressor support, antiarrhythmic medications or mechanical ventilation and not necessarily electrical cardioversion as the first treatment. The presence of multi-organ failure, concomitant sympathetic and neurohumoral surges, arrhythmogenic drugs and invasive surgical therapies modulate the pathways for arrhythmia generation as well as their response to conventional therapies.

The use of vasopressors and inotropes present a challenge to the control of tachyarrhythmias that requires titrating the dose and duration of these therapies, avoiding more arrhythmogenic agents such as dobutamine or dopamine. Recognizing the need for prompt source control in septic patients, controlling electrolyte disturbances in diabetic ketoacidosis, minimizing autonomic fluctuation following a subarachnoid bleed, and closely monitoring and managing pain, anxiety, agitation, oxygenation, and delirium are some examples of addressing the primary illness which can aid in stabilizing cardiac issues.

While successful, post cardioversion tachyarrhythmias tend to recur in patients with sepsis and multiorgan failure. Furthermore the delivery of successive electrical shocks in these patients may be very poorly tolerated as compared to other patient populations. It is thus for the intensivist to make judicious utilization of cardioversion therapy understanding all the benefits and risks involved.

Patients with AF of more than seven days duration, dilated atria on echocardiogram, or heart failure also have an increased risk of recurrence after cardioversion. Narrow complex tachycardias include atrial flutter, atrioventricular nonreentrant tachycardia AVNRT , atrioventricular reciprocating tachycardia AVRT and junctional tachycardia. These rhythms tend to occur in a paroxysmal manner often converting back and forth on their own.

Hemodynamic instability or persistent and symptomatic SVT despite medical therapy IV beta-blocker, calcium channel blocker, or adenosine administration is an indication for urgent cardioversion.

Synchronized cardioversion can be performed in unstable patients with a regular monomorphic VT in the presence of a pulse.

Patients with irregular or polymorphic VT should however be managed with defibrillation. It is important to note that synchronization of the electrical discharge with the QRS complex in monomorphic VT may be very challenging to achieve. Thus, patients who present with signs of clinical instability such as hypotension, chest pain, acute pulmonary edema, heart failure, and change in mental status, should receive urgent unsynchronized defibrillation if attempts at synchronization are unsuccessful.

Although improved survival has been linked to early defibrillation in VF, recent guidelines by the American Heart Association AHA emphasize the importance of immediate high quality chest compressions during cardiac arrest before attempting defibrillation even in the setting of VF or pulseless VT arrest.

See Table 92—1 for the initial energy requirements commonly used during cardioversion using monophasic and biphasic waveform cardioverters. In patients with AF causing hemodynamic compromise, start synchronized cardioversion at Joules J using a biphasic defibrillator and increase up to J during the subsequent shocks.

Unstable atrial flutter or paroxysmal supraventricular tachycardia PSVT require much lower energy and cardioversion may be initiated at 50 J biphasic J monophasic initially, then J if unsuccessful. If it fails to terminate the SVT, a higher follow-up shock of J J monophasic may be delivered. Monomorphic VT with a pulse is treated with synchronized cardioversion with initial J biphasic J monophasic , and escalation of energy to J biphasic J monophasic with each successive shock until sinus rhythm is achieved.

Delivering an initial J J monophasic defibrillation shock is usually sufficient to terminate VF or pulseless VT. If unsuccessful, energy can be escalated to J J monophasic for subsequent shocks. In the case of polymorphic VT with pulse, defibrillation with similar energy settings to J biphasic are used as with pulseless VT.

Delivering shocks can be painful, traumatic and may cause great anxiety in conscious patients receiving synchronized cardioversion or defibrillation. Short acting sedatives such as midazolam 0. In patients who have a secured airway eg, endotracheal intubation and are more hemodynamically stable, propofol eg, 0.

Only in the presence of experienced personnel eg, anesthesiologist, intensivist , propofol can also be administered in smaller doses in nonintubated patients. In the elderly, administering lower doses of sedatives at less frequent intervals and at slower rates may be appropriate. The survival rate goes down 2. It allows for a shorter analysis time and quicker delivery of electric shocks. The positioning of the electrodes on the thorax determines the transthoracic pathway and the flow of current delivered during cardioversion and defibrillation.

Currently, there are two conventional positions accepted for electrode placement: the anterolateral and anteroposterior orientation [ Figures 92—1 A and 1 B ].

In the anterolateral position, a first electrode is placed on the right edge of the sternum along the second or third intercostal space ICS , while the second electrode is placed laterally on the left at the level of fourth or fifth ICS along the mid-axillary line. In the anteroposterior position, the first paddle is placed as above and the second paddle is placed on the back between the tip of the scapula and the spine.

The anteroposterior placement of the electrodes is preferred in patients with implantable cardioverter-defibrillator devices ICDs to avoid shunting of energy and damage to the implantable device. The electrodes should be maintained in contact with the skin using either conductive gel with paddles or by using self-adhesive pads instead.

In the case of pads, care should be taken to ensure that they are well secured. This may be particularly difficult in the patient with excess hair or sweat. The electrode pads are then connected to the cardioverter through a wire with a plastic adaptor usually colored as indicated in Figure 92—2. Each cardioverter is provided with disposable electrode pads designed for that model.

Placement of the pads in an A anterolateral configuration and B anteroposterior configuration. Attach cables to ensure tight connection between electrode pads and the cardioverter. In cases such as in VF or pulseless VT, CPR should not be delayed and should be initiated immediately while preparing for defibrillation. The AHA Guidelines for cardiopulmonary resuscitation CPR and emergency cardiovascular care ECC recommends high quality CPR to be initiated for at least 90 to seconds while the defibrillator pads and electrodes are being applied and before first defibrillation is attempted.

It is believed that during VF, the myocardium is being depleted of oxygen and energy and that delivering CPR during this crucial period will provide the needed oxygen and energy, as well as increase the likelihood of terminating VF during defibrillation and rapid return of spontaneous circulation.

Electrolyte imbalances such as hypocalcemia, hypokalemia and hypomagnesemia should also be corrected to improve successful cardioversion. The following are basic steps for using the cardioverter:. Most defibrillator brands are multifunctional and can be used as an automated external defibrillator AED , manual defibrillator, external pacer or for ECG monitoring.

Make sure that the device is set to defibrillator mode. Once connected, the monitor will display the ECG tracing and the heart rate. The device automatically returns to asynchronous mode after each synchronized discharge. A charge tone indicates that the charge is complete to the selected energy level Figure 92—4. Here is a study Biphasic defibrillation significantly decreases the energy level necessary for successful defibrillation, decreasing the risk of burns and myocardial damage.

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.

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?

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. 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. In monomorphic and polymorphic vt which one should be treated with synchronised cardioversion? And why? Monomorphic ventricular tachycardia is treated with synchronized cardioversion.

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. 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? 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. 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.

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. This means that the shock may fall randomly anywhere within the cardiac cycle QRS complex.