What Is a Good Resting Heart Beat
The electrical system of the heart is critical to how it functions. It determines heart rate (how fast the heart is beating) and also coordinates and organizes the beating of the heart muscles, so that the heart works efficiently with each heartbeat.
Abnormalities in the heart's electrical system can cause heart rate to be too fast or too slow or entirely disrupt the normal functioning of the heart—even if the heart's muscles and valves themselves are entirely normal.
Talking about the cardiac electrical system and abnormal heart rhythms can be very confusing. When we talk about heart disease, many people think of blocked coronary arteries that can result in a heart attack or the need for bypass surgery. Yet, problems with the electrical system may occur even if your heart muscle is normal.
It's helpful to picture your heart as a house and the cardiac electrical system as the wiring that provides power throughout the structure. It's possible to have problems related to faulty wiring even if the building itself is completely normal. Likewise, your heart could be normal but an electrical problem may occur causing an abnormal heart rhythm.
Heart disease can lead to abnormalities in your heart's electrical system, much as a house damaged in a tornado or flood might have problems with the electrical system. In fact, damage to the electrical system of the heart is often the cause of sudden death with a heart attack, even if the damage to the heart caused by the heart attack is only mild or moderate. This is one of the reasons behind performing CPR and having access to defibrillators. If the heart rhythm can be restored, some of these heart attacks (and other causes of arrhythmias) are survivable.
Let's take a look at how the cardiac electrical system works to make your heart beat, as well as medical conditions which can affect your pulse.
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Introduction to the Cardiac Electrical Signal
The heart generates its own electrical signal (also called an electrical impulse), which can be recorded by placing electrodes on the chest. This is called an electrocardiogram (ECG, or EKG).
The cardiac electrical signal controls the heartbeat in two ways. First, since each electrical impulse generates one heartbeat, the number of electrical impulses determines the heart rate. And second, as the electrical signal "spreads" across the heart, it triggers the heart muscle to contract in the correct sequence, thus coordinating each heartbeat and assuring that the heart works as efficiently as possible.
The heart's electrical signal is produced by a tiny structure known as the sinus node, which is located in the upper portion of the right atrium. (The anatomy of the heart's chambers and valves includes two atria at the top of the heart with two ventricles at the bottom.)
From the sinus node, the electrical signal spreads across the right atrium and the left atrium (the top two chambers of the heart), causing both atria to contract, and to push their load of blood into the right and left ventricles (the bottom two chambers of the heart). The electrical signal then passes through the AV node to the ventricles, where it causes the ventricles to contract in turn.
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The Cardiac Electrical Signal Passes to the Ventricles
Figure 4: The specialized AV conduction system consists of the AV node (AVN), the "His bundle," and the right and left bundle branches (RBB and LBB). The AV node conducts the electrical impulse to the His bundle (pronounced "hiss"). The His bundle passes the signal to the right and left bundle branches. The right and left bundle branches, in turn, send the electrical impulse to the right and left ventricles, respectively. The figure also shows that the LBB itself splits into the left anterior fascicle (LAF) and the left posterior fascicle (LPF).
Because the impulse travels only very slowly through the AV node, there is a pause in the electrical activity on the ECG, referred to as the PR interval. (The PR interval is illustrated on the ECG in Figure 3.) This "pause" in the action allows the atria to contract fully, emptying their blood into the ventricles before the ventricles begin to contract.
Problems anywhere along this route can cause abnormalities in the ECG (and heart rhythm).
AV block (heart block) is one of the two major causes of a low heart rate (bradycardia). There are different degrees, with third-degree heart block the most severe and usually requiring a pacemaker.
Bundle branch block occurs in either the right bundle branch or left bundle branch, with those in the left bundle branch usually most serious. Bundle branch blocks may occur for no apparent reason but often occur when the heart is damaged due to a heart attack or other cardiac conditions.
A left bundle branch block from a heart attack is an important cause of sudden cardiac death.
What Is a Good Resting Heart Beat
Source: https://www.verywellhealth.com/cardiac-electrical-system-how-the-heart-beats-1746299
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