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.
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? 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. After the shock is delivered, the energy for each subsequent shock is automatically selected based on the energy level configured on the set-up. Use the Energy Select button to choose the energy level delivered during the cardioversion. These can be grouped as patient characteristics such as body habitus, device characteristics including paddle size, waveform morphology and iatrogenic factors including administration of medications and ventilator support.
Electric shocks used in cardioversion and defibrillation are quantified by the amount of energy delivered. While this allows for the standardization of shocks delivered, it is important to understand that the determinant of an adequate shock is not the energy itself but the amount of electrical current that travels across the heart depolarizing the myocardium.
This resistance, termed as thoracic impedance, is determined by the electrode-to-skin interface, electrode pressure, body habitus and the phase of ventilation.
If the patient has not converted and a second shock is indicated, you will again need to push the SYNC button, as the machine will default to defibrillation mode. Follow the procedure detailed above. In some instances, it may be necessary to make a few adjustments if something is not working as it should during a cardioversion.
For example, a marker may not appear above the QRS complex because the machine is not sensing it. If this occurs, adjusting the amplitude or gain is advised. Meticulous procedural technique to maximize electrical cardioversion success is, therefore, imperative as evidenced by efforts to identify optimal electrode placement, initial energy settings, and modifiable chest wall electrode interface characteristics. Although synchronized cardioversions are often performed without complications, they can occur.
Cardiac complications can include hypotension and dysrhythmia, including ventricular fibrillation or asystole. In some cases, a patient may not be adequately breathing on their own and may need to be manually ventilated.
Becoming Familiar with Synchronized Cardioversion Between , and , American patients suffer in-hospital cardiac arrest with attempted cardiopulmonary resuscitation each year.
Synchronized Cardioversion vs. Defibrillation Synchronized cardioversion involves the delivery of a low-energy shock which is timed or synchronized to be delivered at a specific point in the QRS complex see the image below. Society HR. Accessed January 15, Pacemakers and implantable cardioverter—defibrillators: Essentials for clinicians.
May 12, Major risks of cardioversion include:. Dislodged blood clots. Some people who have irregular heartbeats have blood clots in their hearts. Electric cardioversion can cause these blood clots to move to other parts of your body. This can cause life-threatening complications, such as a stroke or a blood clot traveling to your lungs. If necessary, your doctor may prescribe blood-thinning medications before the procedure or will check for blood clots in your heart before cardioversion.
Cardioversion can be done during pregnancy, but it's recommended that the baby's heartbeat be monitored during the procedure. Cardioversion procedures are usually scheduled in advance. However, if your symptoms are severe, you may need to have cardioversion in an emergency setting. You typically can't eat or drink anything for about eight hours before your procedure.
Your doctor will tell you whether to take any of your regular medications before your procedure. If you do take medications before your procedure, sip only enough water to swallow your pills. Before cardioversion, you may have a procedure called a transesophageal echocardiogram to check for blood clots in your heart. Blood clots can break free by cardioversion, causing life-threatening complications. Your doctor will decide whether you need a transesophageal echocardiogram before cardioversion.
If your doctor finds blood clots, your cardioversion procedure will be delayed for three to four weeks. During that time, you'll take blood-thinning medications to reduce your risk of complications.
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