”Malignant” arrhythmias are mainly ventricular arrhythmias, such as sustained ventricular tachycardia (ventricular tachycardia), ventricular fibrillation (ventricular fibrillation) and some non-sustained ventricular tachycardia, but also include some supraventricular arrhythmias that affect hemodynamics. In recent years, many guidelines on the management of arrhythmias have been introduced or updated.
The management of malignant arrhythmias is an important task for the emergency physician, and as an emergency physician, it is important to understand the unique nature of the emergency determination of malignant arrhythmias. Patients seen in the emergency room are often in critical condition, and physicians do not have sufficient time to take a detailed history and complete relevant tests; even if the situation permits, the available history is very limited, and emergency physicians do not have ample time to consult or wait for a consultation. So, when a patient with an arrhythmia comes to the emergency room, what are the principles of management that should be followed?
Determination of malignant arrhythmias
Determining hemodynamic status is the first priority
The 2005 cardiopulmonary resuscitation guidelines state that the treatment of emergency patients does not require a clear diagnosis or a perfect procedure, but rather emphasizes the need to be “fast”.
When a patient enters the emergency room, the physician’s first task is to determine the patient’s hemodynamic status after the initial examination. If the patient is unconscious, has cardiogenic cerebral ischemia, and the electrocardiogram indicates tachyarrhythmia, there is no room for any evaluation and the arrhythmia must be terminated immediately, often with electrical resuscitation.
In conscious patients, the hemodynamic situation should also be evaluated. Hemodynamic instability is defined as the presence of significant signs of heart failure, severe chest pain, hypotension, and shock. In this case, electrical resuscitation must also be considered immediately, even before 12-lead cardiography is recommended to clarify the nature of the arrhythmia.
Only in hemodynamically stable patients is 12-lead ECG recommended to further clarify the diagnosis.
History and electrocardiogram acquisition
1. Follow up the medical history
If the patient’s condition permits, the physician should pay special attention to collecting information about the arrhythmia, such as whether there have been similar episodes in the past, the diagnoses considered, and the measures of effective treatment, in addition to questioning the patient about his or her disease. If the patient is able to provide records of previous consultations, this will be of great help in the clinical workup. It is important to note that clinical management should not be delayed by waiting for the collection of previous medical history data.
2.Electrocardiogram acquisition
For patients with relatively stable hemodynamics, electrocardiogram is an important examination method. In emergency situations, there are special requirements for ECG diagnosis.
Monomorphic wide QRS tachycardia For monomorphic wide QRS tachycardia, although there are various diagnostic methods (such as the Brugada four-step method), the application of these methods in the emergency setting is limited. It is impossible to ask all emergency physicians to master these very difficult steps, and the diagnosis made by the physician is not 100% correct.
In the emergency setting, the most important thing to look for in a wide QRS-wave tachycardia is evidence of ventricular atrial separation. If evidence of atrial separation can be found, the tachycardia is definitely ventricular. If it is difficult to distinguish (this situation is common), then do not waste time and effort to identify, directly diagnosed as “wide QRS tachycardia” can be. Of course, the nature of the QRS wave can be further determined according to whether it is neat or not. However, the diagnosis of “wide QRS tachycardia” is allowed because in the current CPR guidelines, it is treated according to the same principles, regardless of the mechanism.
For polymorphic wide QRS tachycardia, an important step is to determine the presence or absence of QT interval prolongation. A prolonged QT interval, especially with the typical interval-dependent phenomenon, is a tip-twisting ventricular tachycardia, otherwise it is a general polymorphic ventricular tachycardia. The differentiation between the two is very important because the treatment is completely different.
These two conditions are very easy to confuse clinically. In cases of suspected torsional ventricular tachycardia, the cause must be further determined. In addition to congenital long QT syndrome in some patients, most patients have acquired long QT syndrome.
In these patients, it is important to understand the various possible causes of QT prolongation, especially the presence of pharmacological long QT, and the drugs involved are not only antiarrhythmics, but include almost all systemic therapeutic agents, such as certain antibiotics, antihistamines and antidepressants. Methods exist for risk stratification of these patients and QT monitoring is advocated to prevent the development of torsional ventricular tachycardia. Polymorphic ventricular tachycardia without QT prolongation mostly has causative factors, such as ischemia, heart failure, and hypoxia.
Diagnostic and treatment strategies
Remove the cause and treat the original disease
The emergency treatment strategy for malignant arrhythmias is now well defined. Because of its recurrent nature, measures can be taken to terminate the attack, but in order to prevent recurrence, the causative factors must be removed and the primary disease treated as soon as possible.
For example, in patients with acute coronary syndrome combined with severe heart failure, ventricular fibrillation or ventricular tachycardia, the arrhythmia can be controlled with the establishment of myocardial reperfusion and improvement of cardiac function.
Removal of triggers Some triggers can directly cause arrhythmias, such as electrolyte disturbances (especially hypokalemia) or antiarrhythmic drugs that trigger torsional ventricular tachycardia, and should be corrected.
Treatment of the primary cause Emphasis is placed on the treatment of the primary cause of the malignant arrhythmia following evidence-based medical evidence. In the acute phase of myocardial infarction, in addition to the management of arrhythmias that can affect hemodynamics, hemodynamic reconstruction and the use of angiotensin-converting enzyme inhibitors, antiplatelet agents, statins and β-blockers are required to radically reduce the occurrence of malignant arrhythmias.
For malignant arrhythmias themselves, termination of the attack is often the necessary and most urgent step. Sometimes the arrhythmia can cause severe hemodynamic disturbances, such as ventricular fibrillation or pulseless ventricular tachycardia, because the primary disease is not diagnosed or managed quickly enough.
Change in clinical management thinking
In order to reflect the efficiency of emergency management, there has been a marked change in the current thinking about the management of malignant arrhythmias.
The main changes include.
① Recommending cardiopulmonary resuscitation (CPR) and defibrillation as the preferred treatment modality;
②The electrical resuscitation of ventricular fibrillation and pulseless ventricular tachycardia has been changed from a gradual increase of power for 3 consecutive times to a maximum of power for 1 time;
(3) The importance of drug therapy (including epinephrine and antiarrhythmic drugs) was placed in the second position, and the timing of drug administration was no longer specified.
The above changes in thinking gained consensus among experts, although there was no more evidence-based medical evidence.
Drug therapy
In ventricular fibrillation or pulseless ventricular tachycardia with unsuccessful defibrillation, amiodarone should be preferred after epinephrine; meanwhile, lidocaine, which is known to clinicians (although its efficacy has not been confirmed by more studies), has relatively few side effects and remains as an optional drug after amiodarone, to be used when amiodarone is not available or when its use is contraindicated.
Magnesium is used only as a treatment for torsional ventricular tachycardia. Hemodynamically stable wide QRS tachycardia may also be a malignant arrhythmia, and the drug of choice is amiodarone, procainamide or sotalol, or direct electrical cardioversion.
Amiodarone can be used in a variety of arrhythmic situations, but the method of administration varies. In CPR situations, a rapid intravenous infusion of 300 mg is recommended, and intravenous drip maintenance is not required while circulation has not been restored. In contrast, for wide QRS tachycardia, 150 mg dilution should be given as a slow infusion, after which intravenous maintenance is mostly required.
In the management of torsional ventricular tachycardia due to long QT, the primary treatment is to discontinue the drug that prolongs QT. In the case of complicated medications, the spirit of “pursuing the problem” should be pursued until possible drugs are identified, and if not, all drugs that may cause arrhythmia and are not necessary should be discontinued. Magnesium and potassium supplementation is the basic treatment. Pacemakers can be used in patients with concomitant bradycardia, and antiarrhythmic drugs are not recommended. For general polymorphic ventricular tachycardia, it is important to remove the possible causes, such as ischemia, hypoxia, and acute heart failure, on the basis of which antiarrhythmic drugs can be used appropriately.
Guideline recommendations
The European guidelines on atrial fibrillation published this year clearly state that two important goals in the management of emergency atrial fibrillation are the prevention of thromboembolism and the maintenance of hemodynamic stability. In patients with hemodynamically altered AF, ventricular rate control should be considered first, and if it is not effective and the patient remains symptomatic, cardioversion should be considered. For patients with hemodynamically unstable AF, electrical resuscitation therapy is recommended, and only patients who are stable and still have symptoms after ventricular rate control should be considered for drug diversion therapy.