Cardioversion

Abstract

Cardioversion (CV) is a procedure consisting of 2 different applications, electrical or medical, performed to provide normal sinus rhythm in arrhythmic events. Electrical cardioversion is the preferred direct current-mediated treatment for arrhythmia without sinus rhythm when there is no response to pharmacological therapy or hemodynamic instability due to tachycardia. The difference between defibrillation and electrical cardioversion; in electrical cardioversion, direct current is given on the R or S wave in the QRS by synchronizing with electrocardiography, and in defibrillation, it is given at any moment of the cardiac cycle. Atrial fibrillation and flutter are the most common arrhythmias in which cardioversion is used. Electrical cardioversion should not be performed in patients with ventricular fibrillation, pulseless ventricular tachycardia and digital poisoning. After cardioversion, temporary ST segment elevations, thromboembolism, ventricular fibrillation, short-term bradycardia/asystole, hypotension, pulmonary edema and elevation of cardiac enzymes that do not constitute clinical significance can be observed.

1. Introduction

Cardioversion (CV) is a procedure consisting of 2 different applications, electrical or medical, performed to provide normal sinus rhythm in arrhythmic events. While medical cardioversion is preferred in stable patients and often in elective patients, electrical cardioversion is often preferred in patients who cannot get a medical response or who need an urgent CV [1, 2].

Electrical cardioversion has played an important role for the last 6 decades in the treatment of arrhythmias via direct current today. About 15 years after defibrillation, which was first performed in humans in 1947, electrical cardioversion was applied to convert AF and VT to normal sinus rhythm. Synchronized cardioversion is a procedure similar to defibrillation performed to terminate a life-threatening or hemodynamically unstable tachycardic arrhythmia. The difference between defibrillation and electrical cardioversion; in electrical cardioversion, direct current is given on the R or S wave in the QRS by synchronizing with the electrocardiography, and in defibrillation, it is given at any time of the cardiac cycle. The purpose of synchronization; the aim is to avoid the delivery of energy on the T wave, which coincides with the sensitive period of the myocardium, which may trigger VF. The appropriate approach in cardioversion is to start cardioversion with the recommended energy levels in specific arrhythmias (e.g. initial shock for atrial flutter 70–120 joule) [3, 4, 5, 6].

2. Indications

As a general rule, synchronous cardioversion is the preferred treatment for tachycardia without sinus rhythm, when there is no response to pharmacological treatment, or when hemodynamics due to tachycardia worsens. In contrast to the defibrillation used in cardiac arrest patients, emergency synchronized cardioversion is performed in patients who still have a pulse but are hemodynamically unstable. It is also used to treat hemodynamically unstable ventricular and supraventricular rhythms [3, 4].

The following are the most common indications;

• Atrial fibrillation- flutter

• Supraventricular tachycardia due to reentry

• Atrial tachycardia

• Ventricular tachycardia with pulse

Atrial fibrillation and flutter are the most common arrhythmias in which cardioversion is used. Whether rhythm control or rate control should be provided in AF patients is still a controversial issue. However, if the patient is stable and a rhythm control decision has been made, first of all, heart rate control should be provided, and then cardioversion should be planned by making appropriate preparations after anticoagulation at the effective dose and time.

In patients with AF whose duration is unknown or lasts longer than 48 hours, left atrial/appendix thrombus should be ruled out by transesophageal echocardiography before, otherwise effective anticoagulation should be performed for at least 3 weeks before the procedure, and cardioversion should be planned afterwards. Because of the time interval required for recovery of atrial mechanical functions after cardioversion, anticoagulation should be continued for at least 4 weeks even if sinus rhythm is achieved. In patients who are sure to have AF of less than 48 hours, cardioversion can be performed by applying anticoagulation before the procedure. Anticoagulants should be continued for at least 4 weeks [5, 7, 8, 9, 10].

It has been shown that biphasic devices and anteroposterior electrode positions for atrial fibrillation cardioversion are more effective with lower energy, and the recommended energy is 120–200 joules for biphasic waveforms. If it fails, the process can be repeated by increasing to higher energies. In AF patients, long duration of AF (especially longer than 1 year), increased left atrial dimensions, mitral valve disease, obesity, and chronic obstructive pulmonary disease are factors that decrease the success rate of cardioversion or increase the likelihood of recurrence. Premedication before cardioversion (with amiodarone- ibutilide), the use of a biphasic device and anteroposterior application are approaches that increase the chances of success of cardioversion [5, 8, 10].

In atrial flutter, the anticoagulant approach is the same as AF and it is recommended to start with lower energy levels, biphasic 70–120 joules, monophasic 100 joules due to a more organized arrhythmia [3, 11, 12].

Supraventricular tachyarrhythmias are often terminated with vagal maneuvers or with a medical approach. But if there is no response to them or in case of hemodynamic instability, cardioversion can be performed with a high success rate by starting with 50–100 joules. Routine anticoagulation before cardioversion is not required in SVT patients [3, 13].

In patients with stable hemodynamics, besides ventricular tachycardia with pulse, an approach with medical antiarrhythmic therapy can be planned first under close follow-up. However, emergency cardioversion should be performed in cases of hemodynamic instability, signs of heart failure, angina, and changes in mental status. Organized arrhythmias, such as monomorphic VT, are easily picked up with lower energy levels, while non-organized multiple focal arrhythmias such as polymorphic VT or VF and large myocardial arrhythmias require higher energy levels. In monomorphic VT, it is recommended to start with 100 joules with a biphasic device and 200 joules with a monophasic device, while in polymorphic VT, it is recommended to start with 150–200 joules with a biphasic device and 200–360 joules with a monophasic device. Routine anticoagulation before cardioversion is also not required in VT patients [3, 4, 5, 7].

3. Contraindications

Cardioversion should not be performed in patients with ventricular fibrillation and pulseless VT, defibrillation should definitely be performed [3].

Increased automaticity or triggered activity-induced arrhythmias, junctional tachycardia (e.g. digoxin intoxication), accelerated idioventricular rhythm, multifocal atrial tachycardia, and sinus tachycardia in cardioversion are not indicated. Even tachyarrhythmias due to endogenous catecholamine release may be aggravated after cardioversion. In digital poisoning, the excitability of the myocardium increases, and cardioversion is contraindicated, as it can cause resistant VF. However, it is not necessary to discontinue the drug before cardioversion in patients using digital who do not have clinical signs of digital toxicity. Cardioversion should also not be performed in stable AF patients who have not taken optimal anticoagulants or whose left atrial thrombus has not been ruled out with TEE [3, 5, 7, 9, 14].

4. Procedure

Preparation before cardioversion in stable patients will both increase the chances of success of the procedure, make the patient less traumatized, and reduce the likelihood of complications for the physician. Serum electrolytes should be checked before starting the procedure, and secondary causes that may exacerbate tachycardia (hyperthyroidism, anemia, etc.) should be reviewed. The recommended steps for successful cardioversion are described below (Figure 1).

• Except for unstable patients, the patient should be informed and approval should be obtained before the procedure.

• Patients should be fasted about 6–8 hours before the elective procedure.

• Resuscitation equipment must be available at the patient’s bedside.

• The airway patency of the patients, continuous ECG monitoring, and active vascular access should be absolutely checked.

• A 12-lead ECG should be seen before and after the procedure.

• Sedation with fast-onset-short-lasting drugs (such as midazolam, propofol) is recommended before elective cardioversion.

• Selection of the biphasic device, optimal use of the gel, and placement of the paddles by pressing and discharge in expiration are the factors that can increase the chance of success.

• The paddles should be placed in the appropriate localization (Figure 2. Localization 1–2 for anterolateral (apex-anterior), 3 and opposite side for anteroposterior), and the SYNCHRON key must be pressed before the procedure. If there is no response in the first shock, the process should be continued by increasing the energy level.

Figure 1.

Practical algorithm for cardioversion.

Figure 2.

Localization of paddles.

5. Complications

After cardioversion, arrhythmias that do not require treatment, short-term bradycardia/asystole (especially in antiarrhythmic users, the elderly, long-term AF patients), and ST-T changes may be observed frequently. Bradyarrhythmia that requires temporary pacemakers may develop, especially in patients with acute coronary syndrome. ST elevation lasting under 2 minutes can be monitored. Rarely, VF can also be triggered by proper cardioversion. It has been reported that embolic cerebrovascular accident develops in 1–3% of AF patients after sinus rhythm is achieved. If a healthcare worker comes into contact during the application, the healthcare worker may be affected. In addition, especially due to inappropriate technique, skin burns may be seen in the areas that come into contact directly after the current, creams for the burn can be used. Side effects, hypotension, and hypoventilation may be observed due to the sedation agent applied before the procedure. Rarely, hypotension, pulmonary edema, and elevation of cardiac enzymes that do not constitute clinical significance can be observed [1, 5, 7, 9, 15].

6. Special cases

Supraventricular tachycardia and atrial fibrillation are the most common arrhythmias in pregnancy. Electrical CV is also used as the first choice for maneuvering medically unresponsive and unstable patients. When the literature is reviewed, it can be said that cardioversion is safe for both mother and fetus during pregnancy and is the same approach as in normal adults [7, 16].

It has been reported that the frequency of complications due to electrical cardioversion performed in patients with pacemakers or ICD develops rarely. In patients who developed complications, temporary pacing or sensitivity threshold changes were often observed. In order to detect and avoid these complications, it is recommended to check the battery and lead first. Then it is recommended to program the battery’s voltage output to a higher, program it to VOO or AOO mode. The pedals should be placed 15 cm away from the generator and the direction of the paddles should be placed in the position perpendicular to the endocardial leads. A 5-minute time interval should be given between the two shock waves. Lead and pacemaker control should be performed again after CV. The threshold should be programmed as higher for at least 4–6 weeks, and then the battery and lead should be checked again. In case of a suspected problem, earlier control and intervention can be planned [5, 7, 17, 18].

7. Conclusion

Cardioversion is still a treatment method that has an important place in the treatment of arrhythmias and can be applied in emergency or elective patients. In cardioversion, from the patient selection to the appropriate energy use, from the use of gel to anticoagulant therapy, many of the above-mentioned factors affect the success and complications of cardioversion. Therefore, although it may seem simple, it is a procedure that every stage of it should be carefully followed for high success and low complication.