#atrioventricular node

Someone laugh.

ECB is an acronym for...

E - Wave of Excitation (heartbeat)

C - Walls of atria (left and right) Contract

B - Blood flows to left + right ventricles.

Authored by Sudeb Mukherjee*

Introduction: His Bundle Pacing (HBP) is devoid of consequences of remodelling induced by Right Ventricular Apical Pacing (RVAP). Septal pacing has also been studied in several studies. Complications of heart failure, chamber dilatation and QRS prolongation are not seen in HBP and less in septal pacing. This study was done to evaluate outcomes of HBP versus Septal pacing versus RVAP in those patients requiring pacing.

Methods:

Total 100 patients with atrio ventricular block with syncope who required pacing were included in this study. 50 patients underwent RVAP, 38 patients septal pacing and 12 patients underwent His bundle pacing. Detail echocardiogram-based parameters were obtained before and post pacing 6 months. All data collected appropriately and analysed accordingly using SPSS software by 1-way ANOVA with the use of the Holm-Sidak method for pairwise multiple comparisons or by the χ2 test, as appropriate. The statistical test of main treatment effect was an adjusted F test with Kenward-Roger type adjustment of denominator degrees of freedom.

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For More Articles in Online Journal of Cardiology Research & Reports please click on https://irispublishers.com/ojcr/index.php

For More Open Access Journals in Iris Publishers please click on https://irispublishers.com/journals.php

Authored by Sudeb Mukherjee*

Introduction: His Bundle Pacing (HBP) is devoid of consequences of remodelling induced by Right Ventricular Apical Pacing (RVAP). Septal pacing has also been studied in several studies. Complications of heart failure, chamber dilatation and QRS prolongation are not seen in HBP and less in septal pacing. This study was done to evaluate outcomes of HBP versus Septal pacing versus RVAP in those patients requiring pacing.

Methods:

Total 100 patients with atrio ventricular block with syncope who required pacing were included in this study. 50 patients underwent RVAP, 38 patients septal pacing and 12 patients underwent His bundle pacing. Detail echocardiogram-based parameters were obtained before and post pacing 6 months. All data collected appropriately and analysed accordingly using SPSS software by 1-way ANOVA with the use of the Holm-Sidak method for pairwise multiple comparisons or by the χ2 test, as appropriate. The statistical test of main treatment effect was an adjusted F test with Kenward-Roger type adjustment of denominator degrees of freedom.

Read more...FullText

For More Articles in Online Journal of Cardiology Research & Reports please click on https://irispublishers.com/ojcr/index.php

For More Open Access Journals in Iris Publishers please click on https://irispublishers.com/journals.php

Genetics of Conduction Disease: Atrioventricular (AV) Conduction Disease (block): Gene Mutations – Transcription, Excitability, and Energy Homeostasis

Genetics of Conduction Disease: Atrioventricular (AV) Conduction Disease (block): Gene Mutations – Transcription, Excitability, and Energy Homeostasis

Curator: Aviva Lev-Ari, PhD, RN

UPDATED on 6/13/2013

with a CASE of  Anti-Ro Antibodies and Reversible Atrioventricular Block

N Engl J Med 2013; 368:2335-2337 June 13, 2013 DOI: 10.1056/NEJMc1300484

As an Introduction to the Genetics of Conduction

Heart Arrhythmia: Causes (Part 1)

Author:Steve

Image courtesy of Anders Pearson, Creative Commons license http://creativecommons.org/ licenses/by-nd/2.0/legalcode[/caption]

Many things can cause heart arrhythmia, including heart related conditions such as Coronary Artery Disease (CAD) and Valvular Disease, non heart related conditions such as Diabetes and Sleep Apnea, diet pills, dehydration, and gastroesophageal reflux to name a few. Associated with these conditions, the mechanisms by which an arrhythmia is created may be summarized, in general, by the following list:

Modification of the structure of the heart (thereby changing the conduction path of the electrical impulses) by

Stiffening, thickening, or enlarging of the heart tissue

Replacement of the normal healthy heart tissue with “fibro-fatty tissue”

Inflammation

Problems with the electrical conduction system of the heart (Sinoatrial Node, Atrioventricular Node, and Purkinje fibers)

Scarring of the heart tissue due to irradiation, lack of oxygen/nutrients, previous heart attack, or stress

Unknown issues (“idiopathic”)

During my research I found so many causes that I had to break this blog down into 2 parts: Part 1 will cover the heart-related conditions, and Part 2 will cover the genetic, lifestyle, diet, and non heart-related conditions/illnesses. For each heart condition, I attempted to provide the following:

A  general description

Cause(s)

Type of arrhythmia caused, and the mechanism by which the arrhythmia is caused

Treatment

A reference link for further reading

At the end of this blog I have included useful references which were not otherwise included in any text of the individual conditions.

Heart-related conditions

The following heart-related conditions are capable of causing heart arrhythmia:

A Heart attack that’s currently in progress. A heart attack may be caused by Ventricular Fibrillation (v-fib), or Coronary Artery Disease (CAD). Scarring from a previous heart attack may delay or reroute the electrical signals which control your heartbeat, causing an arrhythmia. The rerouted impulse may develop a feedback loop in the electrical path, resulting in an erratic heartbeat. http://my.clevelandclinic.org/disorders/heart_attack/hic_heart_attack.aspx http://my.clevelandclinic.org/heart/disorders/cad/mi_types.aspx

[caption id=”attachment_411″ align=”alignright” width=”150″> Cross-section image of Idopathic Cardiomyopathy, courtesy of Edwin P Ewing Jr.

Cardiomyopathy - A condition where the heart muscle is weakened and/or enlarged. http://my.clevelandclinic.org/heart/disorders/heartfailure/cardiomyopathy.aspx

Ischemic Cardiomyopathy – Caused by coronary artery disease and heart attacks. This is a common form of Cardiomyopathy.

Dilated Cardiomyopathy (DCM) - When either one or both lower chambers (ventricles) are enlarged. This makes the pumping less efficient and causes the heart to work harder. With DCM, the body retains water in the kidneys, legs, ankles, and feet. Causes of DCM may be genetic, due to Valve Disease, alcoholism, drug abuse, diabetes, viral, post pregnancy (Peripartum Cardiomyopathy), or idiopathic (unknown). Treatment includes medicine, lifestyle changes (reduction of sodium intake and exercise as prescribed by a physician), pacemakers, and potentially surgery. http://my.clevelandclinic.org/heart/disorders/heartfailure/dilated_cardiomyopathy.aspx

Non-Ischemic Cardiomyopathy- When the heart is damaged by reasons other than lack of blood flow to the heart itself. This is a less common form of Cardiomyopathy.

Restrictive Cardiomyopathy- When the walls of the left lower chamber (left ventricle) become stiff and rigid; causes improper filling of the heart cavities with blood, which can in turn cause abnormal rhythm in the upper (atria) and lower (ventricle) chambers. May lead to heart failure. May be caused by excess iron in the heart, exposure to radiation/chemotherapy, sarcoidosis, build-up abnormal proteins in the heart, or build-up of scar tissue (idiopathic). Treatment may include medications, lifestyle changes, and in severe cases a heart transplant. Recommended lifestyle changes by the Cleveland Clinic include controlling your sodium intake, and exercise as prescribed by a physician. In severe cases, a heart transplant may be required. This is a rare form of cardiomyopathy.

    Related: Infiltrative Cardiomyopathy

http://my.clevelandclinic.org/heart/disorders/heartfailure/restrictive_cardiomyopathy.aspx

Hypertrophic cardiomyopathy (HCM) - When a part of the myocardium (heart muscle) becomes thickened. The thickening could occur to the septum (separating the chambers), the apex (the bottom tip), and the right or left ventricles. When the septum thickens, the corresponding ventricle chambers narrow, causing excess pressure buildup. This may cause Mitral Valve to obstruct the blood flow to the aorta, causing blood to spill into the left atrium. As a result, the ventricle needs to work harder to pump blood to the body.

With HCM the ventricle may stiffen and have difficulty opening to receive new oxygen-rich blood from the lungs, causing the left ventricle to pump harder and less efficiently. Changes to the heart occur at the cellular level due to the thickening of the heart, where the cells become disorganized and irregular (called “disarray”). This disorganization is thought to interfere with the conduction of electrical signals through the heart, leading to arrhythmia.

Related:

Asymmetric Septal Cardiomyopathy

Familial Hypertrophic Cardiomyopathy

Hypertrophic Obstructive Cardiomyopathy

Hypertrophic Unobstructive Cardiomyopathy

http://my.clevelandclinic.org/heart/disorders/hcm/default.aspx

Arrhythmogenic Right Ventricular Dysplasia/ Cardiomyopathy (ARVD or ARVC/C)- When fibro-fatty tissue replaces healthy heart tissue in the right lower chamber (right ventricle). It is usually diagnosed in young patients (under the age of 40) and may cause Sudden Cardiac Arrest in athletes. Strong evidence suggests genetics are involved. The fibro-fatty tissue affects the electrical activity which could cause an abnormal heartbeat. There is no known curative treatment for ARVD, the goal of treatment is to prevent sustained VTs and sudden cardiac death (SCD) Common treatments are prescription medicine, radio-frequency ablation, or implanted defibrillator. This is a rare form of cardiomyopathy.

Related:

Right Ventricular Cardiomyopathy

Right Ventricular Dysplasia

http://my.clevelandclinic.org/heart/disorders/heartfailure/arvd.aspx

Dilated Cardiomyopathy (DCM) - DCM may be either Ischemic (according to the http://my.clevelandclinic.org/heart/disorders/heartfailure/ischemic_cardiomyopathy.aspx) or Non-ischemic (according to http://my.clevelandclinic.org/heart/disorders/heartfailure/dilated_cardiomyopathy.aspx). In other words the enlargement of the lower chambers may be due to ischemia (dying of the heart tissue due to lack of blood), or other reasons.

Related:

Alcoholic Cardiomyopathy

Congestive Cardiomyopathy

Diabetic Cardiomyopathy

Familial Dilated Cardiomyopathy

Peripartum Cardiomyopathy

Image of the conduction system of the heart; courtesy of Madhero88 and Angelito7, under the Creative Commons unported license 3.0

Sinus Node Dysfunction (SND) - Refers to the abnormal generation or conduction of electrical impulses in the heart. Often associated with Supraventricular Tachyarrythmias (e.g. atrial flutter and atrial fibrillation), called Tachy-Brady Syndrome. Causes are thought to be related to age (fibrosis of the heart tissue, causing changes in the conduction paths), genetic, medicinal (beta-blockers, calcium-channel blockers, digoxin, and anti-arrhythmic drugs), viral (e.g. rheumatic fever) or dysfunction in the autonomic nervous system. Sudden death due to SND is rare. Treatment includes an implanted pacemaker. http://emedicine.medscape.com/article/158064-overview#aw2aab6b2b3aa

Sick Sinus Syndrome (scarring near the sinus node) – When SND is accompanied by dizziness and fainting (syncope), it is called Sick Sinus Syndrome (SSS). Often caused by scarring in the heart. In young people, SSS may be caused by scarring due to open heart surgery. SSS may cause Sinus Bradycardia (a slow heart rate caused by the sinus node), or Tachy-Brady Syndrome. A Bradycardia may be treated with a pacemaker and medicine, while a Tachycardia may be treated with medicine or ablation. Prevention/treatment may include diet and exercise as recommended by your physician. http://www.mayoclinic.com/health/sick-sinus-syndrome/DS00930 http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001214/ http://www.texasheartinstitute.org/HIC/Topics/Cond/sicksinus.cfm

Heart Block (Conduction Block) – When the electrical impulses from the Sinus Node are partially or completely blocked.

Type 1 - Type 1 Heart Block is characterized by a slowing of the signal to the ventricles, commonly found in highly trained athletes. It may also be caused by drugs such as beta-blockers, diltiazem, verapamil, digoxin and amiodarone. Type 1 usually does not require treatment.

Type 2 – In Type 2 Heart Block, the electrical impulse from the Sinus Node goes slower and slower until the heart skips a beat. The impulse may not reach the lower portions of the ventricles at all also resulting in a slower heart rate. Treatment for Type 2 Heart Block may require medicine and potentially a pacemaker.

Type 3 – In Type 3 Heart Block, the electrical impulse from the Sinus Node does not reach the ventricles at all. The heart adjusts by generating a 2nd source of electrical impulses for the lower chambers. Type 3 Heart Block results in a very slow heart rate. Causes include a highly active vagus nerve in young adults, heart disease, sarcoidosis, cardiomyopathy, heart attack, rheumatic fever, and genetics. Treatment may require medicine and potentially a pacemaker.

http://my.clevelandclinic.org/heart/disorders/electric/heart_block.aspx

Diagram of the human heart, showing the chambers (left and right atria and ventricles), valves, arteries and veins; used under the Creative Commons Attribution-ShareAlike 3.0 Unported license.

Valve Disease – Valve disease may be described as either Valvular Stenosis or Valvular Insuffiency.

If the valves do not open completely (Valvular Stenosis), this may cause thickening of the left ventricle or may cause atrial fibrillation

If the valves do not close properly (Valvular Insufficiency), the blood flows backwards (called Regurgitation), which can lead to enlargement of the left ventricle

Causes include genetics, rheumatic fever (where the antibodies cause inflammation and scarring of the valve), endocarditis (where germs enter the blood stream, attach to the valves within the heart, and cause scarring or pock holes), and unknown (idiopathic) causes. Rheumatic fever is caused by an untreated streptococcal infection, and endocarditis may be caused by dental procedures, surgery, intravenous drug use, severe infections, heart attacks, syphilis, cardiomyopathy, tumors, and some types of drugs and radiation. http://my.clevelandclinic.org/heart/disorders/valve/valve_types.aspx

Myocarditis (Inflammation of the heart) – Myocarditis is inflammation of the heart, which is primarily caused by a virus (measles, coxsackie B virus, tetanus, gonorrhea, tuberculosis). May also be caused by radiation therapy in the area of the chest (e.g. for lung or breast cancer), cocaine use, Human Immunodeficiency Virus (HIV), bacterial infections (e.g. chlamydia, streptococcus), fungal infections, and potentially certain medications. People with Myocarditis may show symptoms of Ventricular Tachycardia, due to the inflammation (changes the way the electrical impulses travel through your heart). If caused by a viral infection, Myocarditis is treated by rest and avoidance of exertion, and potentially prescription drugs. If caused by a bacterial infection, antibiotics may be prescribed, and in severe cases a heart transplant may be necessary. http://medical-dictionary.thefreedictionary.com/Inflammation+of+the+heart http://www.nlm.nih.gov/medlineplus/ency/article/000149.htm

Premature heartbeat - Can cause a long lasting arrhythmia in a person with heart disease. http://www.mayoclinic.com/health/heart-arrhythmias/DS00290/DSECTION=causes

Congenital heart disease - Many heart arrhythmias listed here may be hereditary, such as secondary cardiomyopathy, ARVD, DCM, HCM, and SND. See the definitions of these heart conditions above for more information.

Micrograph image of Coronary Artery Disease (artherosclerosis); courtesy of Nephron and used under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Coronary Artery Disease (CAD) – This is when the arteries become narrow, due to plaque, stress, high dietary fat intake, or genetics. “Chronic high-grade stenosis of the coronary arteries can induce transient ischemia which leads to the induction of a ventricular arrhythmia, which may terminate into ventricular fibrillation leading to death (source: http://en.wikipedia.org/wiki/Chronic_coronary_artery_disease). Stenosis, being a narrowing of the arteries, and ischemia, meaning lack of blood flow (and therefore oxygen and glycogen delivery) to body tissue, describes plaque buildup in the arteries of the heart. Without enough oxygen and nutrients, sections of the heart muscle may die, causing angina (chest pains) or heart attack. The scarring also may change the conductive pathways of electrical impulses in the heart. Treatment includes 3 successively higher levels, listed here from most conservative to least: a low-fat and low-salt diet, medication, and surgery. http://www.nhlbi.nih.gov/health/health-topics/topics/cad/  http://www.nhlbi.nih.gov/health/health-topics/topics/cad/signs.html

High Blood Pressure – Causes the heart chambers to pump and work harder; causes the left ventricle to become thickened (hypertrophy); may cause Cardiomyopathy of the left ventricle; may cause atrial fibrillation. The exact mechanism that links high blood pressure to ventricular arrhythmias is unknown. http://www.ncbi.nlm.nih.gov/pubmed/8299639

I am not a trained medical professional and I strongly warn anyone against using this information as a substitute for medical attention or diagnosis from a trained medical professional such as your family physician or cardiologist. If you are having palpitations or symptoms of arrhythmia, you need to get a diagnosis from a doctor. I am providing this information as part of my personal research into my own health issues, and I feel that sharing this knowledge can allow you and I to discuss our conditions with our doctors in a more intelligent manner. I take this very seriously. Don’t skip this step. Thanks.

Part 2 of this blog will include non-heart-condition related causes of heart arrhythmias, including causes due to dietary, lifestyle, and other illnesses.

Links: Mayo Clinic heart-arrhythmias Patient.co.uk Heart Arrhythmias Stanford Hospital arrhythmia causes Wikipedia Sarcoidosis Emerson Cardiovascular National Heart Lung and Blood Institute cardiomyopathy alternate names Medical Health Tests non-ischemic-cardiomyopathy Cardiac health cardiomyopathy

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