Sick sinus syndrome (sinus node dysfunction), which is a common cause of bradycardia, is also discussed separately. It is very common that patients with bradycardia have a strong indication for drugs that aggravate or even cause the bradycardia in such scenarios, it is generally considered to be evidence based to implement an artificial pacemaker that will allow for drug therapy to continue. If drug side effects are believed to be the cause, it is fundamental to judge the risk of terminating drug therapy as compared with implementing an artificial pacemaker in order to be able to continue drug therapy. When in doubt whether the bradycardia is physiological, it is useful to perform a Holter ECG (ambulatory recording). The most common causes are sinus node dysfunction, side effects of medications or acute myocardial ischemia/infarction. When the bradycardia causes hemodynamic symptoms it should be treated. Note that sinus bradycardia due to ischemia located to the inferior wall of the left ventricle is typically temporary and resolves within 1–2 weeks ( sinus bradycardia due to infarction/ischemia is discussed separately).īenign (physiological) causes of bradycardia (e.g vasovagal reaction, well-trained athletes) need not be treated. Treatment of sinus bradycardia: general aspects of managementīenign causes of sinus bradycardia (SB) do not require treatment. In all other situations it is necessary to find the underlying cause and direct treatments towards it. The small q-waves in inferior leads (II, aVF, III) are not significant. Sinus bradycardia, two premature ventricular contractions, incomplete right bundle branch block and ST-segment depressions in V2-V6. As seen in the figure, there are approximately 6.5 large boxes between two R waves. Calculate the rate by dividing 300 by the number of large boxes between two cycles (e.g between two R waves). Increased intracranial pressure (manifests with sinus bradycardia and hypertension).įigure 1 shows sinus bradycardia at paper speed 25 mm/s.įigure 1.They may also induce conduction defects (e.g AV block). Side effects of drugs (notably beta blockers, digitalis, verapamil, diltiazem, amiodarone, klonidin) – These drugs affect the pacemaker cells in the sinoatrial node.Sinus Node Dysfunction (SND)– Sinus node dysfunction implies that the cells of the sinoatrial node are defect and fail to generate electrical impulses.This type of bradycardia is due to diminished automaticity (pacemaker function) in the sinoatrial node or conduction defects (e.g second-degree AV block) as a result of ischemia/infarction. Myocardial ischemia/infarction – Particularly ischemia or infarction located to the inferior wall of the left ventricle.The most important causes are as follows: There are numerous pathological conditions that cause sinus bradycardia. In all other situations, sinus bradycardia should be regarded as a pathological finding. This is also a normal finding.Ībnormal (pathological) causes of sinus bradycardia Its not uncommon to discover SB in healthy young individuals who are not well-trained.During vagal maneuvers (Valsalva maneuver, carotid sinus stimulation).During vasovagal syncope (e.g during intense emotional stress).These individuals have developed a highly efficient left ventricle, capable of generating sufficient cardiac output at low heart rates. Well-trained individuals display SB at rest due to high vagal tone.Sinus bradycardia (SB) is considered a normal finding in the following circumstances: Normal (physiological) causes of sinus bradycardia P-waves with constant morphology preceding every QRS complex.Regular rhythm with ventricular rate slower than 50 beats per minute. ![]() Sinus bradycardia fulfills the criteria for sinus rhythm but the heart rate is slower than 50 beats per minute. Sinus bradycardia: ECG, causes & management Definition of sinus bradycardia
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