The heart functions as a pump, but its ability to circulate blood throughout the body relies on precise electrical coordination. This synchronization creates the steady, rhythmic heartbeat people rarely think about until it fails. When the heart’s electrical system malfunctions, the resulting lack of coordination signals that the organ’s pumping action is no longer operating efficiently. The issue is a breakdown in the complex timing required for the upper and lower chambers to work together.
Defining the Heart’s Electrical System
The normal, synchronized heartbeat originates with the Sinoatrial (SA) node, located in the upper right chamber, the atrium. The SA node acts as the heart’s pacemaker, generating electrical impulses typically between 60 and 100 times per minute. The impulse rapidly spreads across the two upper chambers, causing them to contract and push blood down into the ventricles.
The signal then pauses briefly at the Atrioventricular (AV) node, situated between the atria and ventricles. This momentary hold allows the ventricles to fully fill with blood before they are signaled to contract. The impulse finally travels down the Bundle of His and through the Purkinje fibers, distributing the signal quickly across the ventricular muscle mass to ensure a unified contraction that ejects blood to the lungs and body.
The Medical Term: Arrhythmias and Dyssynchrony
The medical term for a heart that is “out of sync” is Arrhythmia. An arrhythmia represents any abnormality in the heart’s rate, rhythm, or the site where the electrical impulse originates. This is defined as any deviation from the heart’s normal sinus rhythm, the steady, predictable pattern set by the SA node.
The problem is one of timing, where the electrical signal is either generated incorrectly or conducted along the wrong pathways. While an arrhythmia describes the irregular rhythm, the term Dyssynchrony refers specifically to a lack of coordinated mechanical contraction between the heart’s chambers. Dyssynchrony often occurs when the electrical signal reaches different parts of the ventricle at different times, leading to an inefficient, twisting contraction instead of a unified squeeze.
Categorizing Irregular Heart Rhythms
Arrhythmias are classified based on the heart rate and the anatomical location where the irregular electrical activity begins. Tachycardia is a resting heart rate exceeding 100 beats per minute, which can reduce the time the ventricles have to fill with blood. Conversely, Bradycardia describes a resting heart rate that falls below 60 beats per minute, potentially failing to supply enough oxygen-rich blood to the body.
The origin of the electrical disturbance separates arrhythmias into supraventricular and ventricular types. Supraventricular arrhythmias (SVT) arise in the atria or the AV node, meaning they originate above the ventricles. The most common example is Atrial Fibrillation (AFib), where the atria quiver chaotically instead of contracting effectively, causing an irregular and often rapid pulse. Atrial Flutter is also an SVT where the atria beat rapidly but in a more organized, circular pattern.
In contrast, Ventricular arrhythmias originate within the lower chambers, the ventricles. Ventricular Tachycardia (VT) is a fast, regular rhythm that starts in the ventricles and can quickly deteriorate into Ventricular Fibrillation (VFib). VFib is a state where the ventricles merely twitch instead of pumping, leading to immediate circulatory collapse and requiring rapid defibrillation to restore a functional rhythm.
Underlying Conditions That Trigger Arrhythmias
The disruption of the heart’s electrical system results from structural damage or systemic health issues. Structural heart disease is a trigger, as conditions like a prior heart attack can leave scar tissue in the muscle, interrupting conduction pathways and creating electrical short circuits. Chronic high blood pressure can also cause the heart chambers to stiffen or enlarge, altering the muscle structure and predisposing the heart to irregular rhythms.
Heart failure also creates an environment conducive to arrhythmias by stretching the heart muscle and increasing pressure within the chambers. Electrolyte imbalances, specifically in minerals like potassium, sodium, and calcium, directly impair the function of the ion channels that control the flow of electrical current across heart cells.
Thyroid disorders, particularly an overactive thyroid (hyperthyroidism), can flood the system with hormones that overstimulate the heart, forcing the SA node to fire too quickly. External factors, such as excessive caffeine, alcohol consumption, or the use of certain cold medications containing stimulants, can also trigger temporary arrhythmias in susceptible individuals.
Conditions known as Channelopathies are inherited disorders involving genetic mutations in the ion channels of heart cells. These predispositions, such as Long QT Syndrome or Brugada syndrome, can cause sudden, life-threatening arrhythmias even in individuals with an otherwise structurally normal heart.