LIFE-THREATENING CARDIAC ARRYTHMIAS Raluca Tat, Adela Golea Educational objectives What you need to know What is a life-threatening arrhythmia How life-threatening arrhythmias are classified What are the signs/symptoms of hemodynamic instability What are the therapeutic options What are the indications of synchronized electrical cardioversion What are the indications of cardiac pacing What are the main indications of antiarrhythmic drugs used in the management patients with arrhythmia What is the antiarrhythmic dosing recommended for the management of patients with arrhythmia What you need to do Identify arrhythmia Identify patients with instability signs/symptoms Choose the appropriate therapeutic option for treating arrhythmia in accordance with the clinical status of the patient and the type of identified arrhythmia Definition Cardiac arrhythmia is a disturbance of the heart rate which may affect the frequency (the alteration of the succession of heartbeats), the regularity of cardiac frequency (the alteration of the ratio between atrial and ventricular rhythms) or both. These changes occur due to a disturbance of myocardial automatism, excitability and contractility, as the heart (body) is subjected to a wide range of pathological (stress) events, such as ischemia, hypoxia, acidosis, electrolyte imbalances, excessive intake of catecholamines, toxic substances etc. Classification: according to origin: sinus, atrial, junctional and ventricular according to heart rate: bradycardia (HR < 60 bpm) and tachycardia (HR > 100 bmp) according to duration: paroxysmal (sudden onset and ending), non-paroxysmal (gradual onset and ending), acute (< 3 weeks) and chronic (> 3 weeks) The correct diagnosis and early treatment of arrhythmias in critical patients may prevent cardiac arrest or the recurrence thereof following a successful resuscitation. Within these circumstances, a series of approach algorithms relating to life- threatening arrhythmias have been issued in order to help out clinicians treat emergency patients as efficiently and as securely as possible. Treatment principles The initial assessment and treatment of patients with arrhythmia must comply with the ABCDE principle and should take into account two aspects: the patient's clinical status (hemodynamically stable or unstable) and the nature of the arrhythmia. The patient's vital signs shall be monitored as soon as possible, at least one peripheral venous access site shall be prepared and specific therappy shall be initiated for all identified abnormalities: o A: open airway o B: breathing rate (BR), SpO2 o C: blood pressure (BP), ventricular rate (VR), hear rate (HR), capillary refill time (CRT) o D: AVPU score1, blood glucose level o E: toxic, environmental factors o Performing 12-lead ECG (specifies rate before treatment or retrospectively – Figure 1 and Figure 2) o The collection of biological samples and the correction of identified abnormalities (e.g. electrolyte imbalances: Mg, Figure 1. ECG waveforms Ca, K) and segments 1 AVPU stands for Alert, Voice, Pain, Unresponsive . The AVPU scale is a simplified Glasgow scale and is used for assessing conscience status. Figure 2. 12-lead ECG. normal RS, PQ, narrow QRS, normal T, normal QT, VR 60/min o Detailed medical history for assessing causes and contexts of arrhythmia onset Antiarrhythmic medication is slower in showing effects and less reliable than electrical cardioversion when the conversion of a life-threatening tachyarrhythmia/ hemodynamic instability clinical phenomena to sinus rhythm is attempted. For these reasons, electrical conversion therapy is usually preferred in patients with signs/symptoms of hemodynamic instability, whereas medication is reserved to patients with no hemodynamic disorder. Signs / Symptoms of hemodynamic instability: The lack or presence of signs/symptoms of hemodynamic instability indicate the most appropriate treatment option for most arrhythmias. o Shock – is characterized by pale and perspired skin, cold and wet limbs (increase of sympathetic activity), alteration of awareness (decrease of brain blood supply) and hypotension (BP < 90 mm Hg). o Syncope – temporary loss of consciousness, following a decrease in the brain's blood supply o Acute heart failure – arrhythmias decrease coronary blood supply and compromise myocardial activity. Signs and symptoms include acute pulmonary edema (left ventricular failure) and/or jugular turgescence and hepatic stasis (right ventricular failure). o Acute myocardial ischemia – occurs when the myocardial oxygen consumption is higher than the supply. It may cause angina (chest pain) or may only lead to isolated changes of the T waveform (sometimes linked to ST segment elevation myocardial infarction), highlighted by 12-lead ECG (silent ischemic lesion or acute coronary syndrome). In case of an underlying coronary or structural heart disease, myocardial ischemia increases the likeliness of severe complications, including heart arrest. Therapeutic options: Once the rhythm has been assessed and the presence/absence of signs/symptoms of hemodynamic instability have been established, the immediate treatment options are: o electrical therapy (cardioversion, pacing) o medication therapy (antiarrhythmics and other drugs) I. Tachyarrhythmias 1. Hemodynamically unstable patient If the patient is hemodynamically unstable (showing any sign/symptom of hemodynamic instability caused by cardiac arrhythmia) and the clinical condition deteriorates, the first treatment choice is synchronized electrical cardioversion. In patients with no cardiovascular conditions in their medical history, instability signs and symptoms are not present at a ventricular rate < 150 beats/minute. Conversely, patients with comorbidities and cardiac dysfunction may be symptomatic and hemodynamically unstable at lower heart rates. If conversion fails to restore normal heart rate and the patient is still unstable, 300 mg IV amiodarone may be given over 10-20 minutes and electrical cardioversion may be repeated if the arrythmia persists. The initial bolus of amiodarone may be followed by a loading dose of 900 mg of amiodarone within the first 24 hours. Repeated electrical cardioversion attempts are not indicated in recurrent atrial fibrillation paroxysmal episodes. These are mostly recommended for critical patients with arrhythmia exacerbation factors, such as sepsis and metabolic dysfunctions. In the mean time, it should be mentioned that electrical cardioversion therapy does not prevent recurrence of arhythmias. If arrhythmia recurrence periods do occur, these are treated with antiarrhythmia medication. Synchronized electrical cardioversion Electrical cardioversion is used for the conversion of atrial or ventricular tachyarrhythmias with pulse. The administered shock is synchronized with the R waveform on the ECG, and not with the T waveform (thus avoiding the relative refractory period and minimizing the risk of inducing ventricular fibrillation). Patients in an aware state require analgesia and sedation prior to the performance of syncrhonized cardioversion. In case of wide complex tachycardia (Figure 3) and atrial fibrillation (AFib, Figure 4), cardioversion is initiated with a 120-150 J biphasic energy. If the initial attempt fails, the energy is increased gradually for the next shocks. Atrial flutter (Figure 5) and paroxysmal supraventricular tachycardia (PSVT, Figure 6) are usually converted at lower energy levels, starting with biphasic 70-120 J. Figure 3. Ventricular tachycardia: wide QRS tachycardia Figure 4. Atrial fibrillation: irregular beat, no P waveform, with F waveform Figure 5. Atrial fibrillation: regular beat, no P waveform, with waveform Figure 6. Supraventricular tachycardia: tachycardia rate, QRS complexes 2. Hemodynamically stable patient Medication can be considered if the patient suffering from tachycardia is hemodynamically stable (no instability signs and symptoms) and is not clinically impaired. Assess the rate (regular/irregular) by 12-lead ECG and establish the duration of the QRS complex. If the duration of the QRS complex is > 0.12 s (3 small squares on the standard ECG paper), the tachycardia is classified as wide complex tachycardia. If the duration of the QRS complex is < 0.12 s, the tachycardia is classified as narrow complex tachycardia. All antiarrhythmic therapeutic options – vagal manoeuvres, medication-based or electrical therapy – may turn out to be pro-arrhythmics. Therefore, the deterioration of the clinical status of the patient may be due to an adverse reaction of the therapy and not necessarily to the lack of effectiveness. The use of multiple doses of various antiarrhythmic substances or of a very high dose of a single antiarrhythmic substance may lead to myocardial depression and hypotension associated with further deterioration of the cardiac rate. A cardiology check-up should be carried out before using repeated doses or combinations of antiarrhythmic drugs. a. Wide QRS tachycardia Wide complex tachycardias usually have a ventricular origin. Although this type of tachycardia may also be caused by supraventricular rhythm with aberrancy, in the case of hemodynamically unstable patients with cardiac arrest risk consider the origin of this type of wide complex tachycardia as ventricular. In hemodynamically stable patients, the next step consists of establishing whether the rhythm is regular or irregular. Wide QRS tachycardia with regular rhythm A wide complex tachycardia with regular rhythm is more likely to be a ventricular