T½ 4−24 h (affected by age, smoking, hepatic function, drug interactions, etc.) Useful if concurrent inotropic insufficiencyĪdenosine receptor antagonist and phosphodiesterase inhibitor Useful if hypotension is an issue (owing to vasoconstricting effect)ĭopamine and alpha and beta adrenoreceptor agonist T½ 3 min followed by slower elimination (t½ 10 min) Infusion 2–10 μg/min (titrate with response) May not be well tolerated over many hours because of side effects (trembling, headache, etc) Start infusion at 4 μg/min then up-/down-titrate over minutes to 1−10 μg/min based upon response CI: glaucoma, prostatism, illeusĪlpha-1, alpha-2, beta-1 and beta-2 adrenoreceptor agonist Doses <0.5 mg may paradoxically worsen bradycardia. Muscarinic acetylcholine receptor antagonistĠ.5 mg i.v. Table 2: Drugs used to increase heart rate. Pharmacological treatment for bradycardia due to drug toxicity is summarised in table 3. However, in the case of infranodal AVB III, heart rate may increase with infusion of catecholamines (e.g., isoprenaline) owing to acceleration of the automatic escape rhythm, and may therefore be of therapeutic interest despite lack of improvement in AV conduction. It should be noted that drugs that increase sinus rate may worsen infranodal block. A list of the drugs used is shown in table 2. Pharmacological therapy is most often the first line of treatment for bradycardia because it is the most readily available. 2).įullscreen Figure 2: Management of acute bradycardia according to the 2015 European Resuscitation Council guidelines. In 2015, the European Resuscitation Council published guidelines on advanced life support, which include an algorithm for the acute management of bradycardia (fig. Note the presence of conducted beats (asterisks), alternating with AVB II and junctional escape rhythm (the short PR intervals preceding the third and sixth QRS complexes are too short to have conducted). Wide QRS (however the patient may have nodal block with concomittent bundle branch block!)ĪVB = atrioventricular block BB = beta-blockers CSM = carotid sinus massageįullscreen Figure 1: Patient with misdiagnosis of AVB III. Narrow QRS (however, intra-Hissian block may result in a narrow QRS!) Improved conduction with Atropine/catecholamines Worsened conduction with atropine/catecholamines Table 1: Clues to help distinguish nodal from infranodal atrioventricular block.ĪVB II Wenckebach (may exceptionally be infranodal!) A common mistake is to misdiagnose AVB III by failing to recognise conducted P waves (fig. AVB III may occur at both nodal as well as infranodal levels, although the latter is more frequent. Nodal AVB can be distinguished from infranodal AVB by careful analysis of the electrocardiogram and by diagnostic bedside manoeuvres (table 1). –Ğffect of pharmacological treatment (isoprenaline, atropine) – Presence or absence of a documented escape rhythm – Type of bradycardia (sinus, AVB II Wenckebach vs Mobitz 2, AVB III) – Systemic repercussions of bradycardia and a low-output state (renal function, lactate, etc.) – Presence, duration and gravity of symptoms (for how long has the patient been symptomatic? Was there syncope? If yes, did it result in trauma?) Management strategies for bradycardia depend upon a number of factors, listed below: Overall, therapy for bradycardia aims to (1) avoid asystole, (2) improve haemodynamic status, or (3) avoid tachycardia (e.g., in the setting of a prolonged QT interval with torsades de pointes). Obviously, not all documented bradycardia needs treatment and, conversely, undocumented but suspected bradycardia may need backup measures to avoid asystole. Proper clinical evaluation will lead to appropriate therapeutic measures, whereas mismanagement may have a fatal outcome. Infranodal block (bundle of His or bundle branches) may lead to prolonged asystole without an escape rhythm. In general, sinus bradycardia or arrest, as well as atrioventricular block (AVB) at the nodal level, have a benign prognosis. It is important to be able to identify the mechanism of bradycardia in order to distinguish benign from life-threatening situations. Patients admitted with bradycardia may present with a variety of clinical pictures, ranging from fatigue to syncope and cardiac arrest. A University Hospital of Geneva, Switzerland b Nyon regional hospital, Switzerland
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