{"id":9628,"date":"2021-12-28T17:54:54","date_gmt":"2021-12-28T15:54:54","guid":{"rendered":"https:\/\/meddists.com\/learn\/clinical\/internal-medicine\/cardiology\/bradycardias-cardiac-conduction-system-disease-syncope\/"},"modified":"2022-01-02T23:51:22","modified_gmt":"2022-01-02T21:51:22","slug":"bradycardias-cardiac-conduction-system-disease-syncope","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/clinical\/internal-medicine\/cardiology\/bradycardias-cardiac-conduction-system-disease-syncope\/","title":{"rendered":"Bradycardias: cardiac conduction system disease. Syncope"},"content":{"rendered":"<span class=\"block-heading\" id=\"header_1\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Bradycardias<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">Bradycardia is defined as a heart rate of below 60BPM in adults.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They can be classified based on the QRS complex (narrow or wide), presence and morphology of P waves, and the relationship between the P waves and QRS complexes.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>By itself, bradycardia shows no increased risk for mortality<\/li><li>In patients with syncope or weakness, atropine can be used to reduce the vagal tone, and a pacemaker therapy can be a permenant solution.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Types<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<ul class=\"wp-block-list\"><li>Sinus bradycardia<\/li><li>SA pause and arrest<\/li><li>SA block<\/li><li>Sick sinus syndrome<\/li><li>AV block<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Sinus bradycardia<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<ul class=\"wp-block-list\"><li>Regularly sinus rhythm but below 60BPM; clinically important when &lt;45BPM.<\/li><li>Physiological in many cases, can be seen during deep sleep and in athletes.<\/li><li>Other causes include ischemia, antiarrhythmic drugs, increased vagal tone, and sick sinus syndrome.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">SA pause and arrest<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<ul class=\"wp-block-list\"><li>Irregular sinus rhythm; <strong>some impulses fail to generate<\/strong>, leading to a period of time without any beats.<\/li><li>Sinus pause refers to under 2 seconds, while sinus arrest is over 2 seconds without any beats.<\/li><li>Most commonly caused due to increased vagal tone.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">SA block<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<ul class=\"wp-block-list\"><li>Irregular sinus rhythm; <strong>some impulses are blocked or are conducted with a delay<\/strong>.<\/li><li>Divided into first, second, and third degree:<ul><li>First degree has a delay in the conduction (not seen on ECG).<\/li><li>Second degree has two types: <ul><li>Type I: gradual lengthening followed by a drop.<\/li><li>Type II: intermittent dropped beats. The following beats appear exactly where they should.<\/li><\/ul><\/li><\/ul><\/li><li>Can be idiopathic, or due to ischemia, or sick sinus syndrome, <\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_6\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Sick sinus syndrome<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_6\">\n\n\n<p class=\"wp-block-paragraph\">SA node dysfunction due to degeneration, ischemia, drugs, or cardiomyopathy.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Appears mostly in the elderly<\/li><li>Can manifest as sinus bradycardia, SA block, and paroxysmal tachycardia.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_7\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">AV block<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_7\">\n\n\n<ul class=\"wp-block-list\"><li><strong>First degree<\/strong><ul><li>Prolonged conduction within the AV node<\/li><li>The PR interval is prolonged (>0.2s or 5 small squares)<\/li><li>Does not require treatment<\/li><\/ul><\/li><li><strong>Second degree<\/strong><ul><li>Mobitz type I (Wenkebach)<ul><li>Progressive prolongation or the PR interval leading to a &#8220;dropped&#8221; beat, followed by a &#8220;reset&#8221; of the PR length.<\/li><li>AV nodal dysfunction<\/li><li>Does not require treatment<\/li><\/ul><\/li><li>Mobitz type II<ul><li>P waves fail to conduct (P wave followed by a missing QRS complex)<\/li><li>His-Purkinje dysfunction<\/li><li>May progress to 3rd degree AV block<\/li><li>Requires pacemaker therapy<\/li><\/ul><\/li><\/ul><\/li><li><strong>Third degree<\/strong><ul><li>Complete dissociation of the P waves and QRS complexes<\/li><li>Junctional (narrow)\/ventricular (broad) escape rhythm<\/li><li>AV nodal dysfunction<\/li><li>Requires pacemaker therapy<\/li><\/ul><\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_8\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Syncope<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_8\">\n\n\n<p class=\"wp-block-paragraph\">Syncope is the transient loss of conciousnes due to an acute decrease in the cerebral bloodflow, often due to an abrupt drop in systemic blood pressure.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Usually appears with prodromal symptoms (tunnel vission, ear ringing, nausea), except for cardiac syncope which is sudden.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_9\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Causes<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_9\">\n\n\n<ul class=\"wp-block-list\"><li><strong>Vasovagal sycope<\/strong> (most common)<ul><li>Due to enhanced parasympathetic activity that leads to bradycardia and vasodilation<\/li><li>Usually in young patients<\/li><li>Treated by leg elevation and beta-blockers if recurrent<\/li><\/ul><\/li><li><strong>Cardiac<\/strong><ul><li>Arrhythmias (bradyrhythmias, VT, rapid SVT), and acute heart failure<\/li><li>Worst prognosis<\/li><\/ul><\/li><li><strong>Orthostatic hypotension<\/strong><ul><li>Reduced intravascular volume\/vasopressor response<\/li><li>Common in the elderly, diabetics, patients on vasodilators, and diuretics<\/li><li>Treated by fluid and electrolyte intake<\/li><\/ul><\/li><li><strong>Cerebrovascular disease<\/strong> (rare)<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_10\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Diagnosis<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_10\">\n\n\n<p class=\"wp-block-paragraph\">Diagnosis is aimed to determine the cause and isolate cardiac patients:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Thorough history taking<\/li><li>Physical examination<\/li><li>ECG<\/li><li>Additional:<ul><li>Blood tests<\/li><\/ul><ul><li>Eechocardiography<\/li><li>EEG<\/li><li>Tilt-table examination<\/li><li>Holter ECG<\/li><li>EP studies<\/li><\/ul><\/li><\/ul>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Bradycardias<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Types<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Sinus bradycardia<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">SA pause and arrest<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">SA block<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Sick sinus syndrome<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">AV block<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Syncope<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Causes<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Diagnosis<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Bradycardias Bradycardia is defined as a heart rate of below 60BPM in adults. They can be classified based on the QRS complex (narrow or wide), presence and morphology of P waves, and the relationship between the P waves and QRS complexes. By itself, bradycardia shows no increased risk for mortality In patients with syncope or [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":410,"menu_order":17,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-9628","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Bradycardias: cardiac conduction system disease. 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