Asystole is the absence of detectable electrical activity in the heart’s ventricles. On an ECG or monitor, it is commonly described as a “flatline,” although artifacts can mimic it. Clinically, Asystole is most often discussed as a cardiac arrest rhythm in emergency and inpatient settings. It is also used as a term in ECG interpretation, telemetry monitoring, and resuscitation documentation.

Pause is a temporary gap between heartbeats seen on an electrocardiogram (ECG) or rhythm monitor. It describes a moment when the heart’s electrical system does not produce or conduct a beat as expected. Clinicians most often discuss Pause when evaluating symptoms like fainting, dizziness, or unexplained fatigue. Pause is also a term used in reports from Holter monitors, telemetry, and implanted rhythm recorders.

Atrial Ectopy is a term for extra heartbeats that start in the atria (the heart’s upper chambers). It most often refers to premature atrial contractions (PACs), sometimes called atrial premature beats. It is commonly discussed on ECGs, Holter monitors, event monitors, and wearable rhythm recordings. It can be an incidental finding or a clue that helps explain symptoms like palpitations.

Ventricular Ectopy means extra heartbeats that start in the ventricles, the heart’s lower pumping chambers. These beats occur outside the normal rhythm pathway and may feel like a “skip” or “thump.” It is a common finding on ECGs and heart monitors in clinics, emergency departments, and hospitals. Clinicians use the term when describing premature ventricular beats and related patterns.

Narrow Complex Tachycardia is a fast heart rhythm with a “narrow” QRS complex on an ECG. In plain terms, it usually means the heartbeat is rapid but is still using the heart’s normal ventricular conduction pathways. It is most often discussed when evaluating supraventricular tachycardias (rhythms that start above the ventricles). Clinicians use it as an ECG description that guides diagnosis and next-step testing.

Wide Complex Tachycardia is a fast heart rhythm with a “wide” QRS complex on an electrocardiogram (ECG). “Wide” usually means the ventricles (the heart’s main pumping chambers) are being activated more slowly than normal. It is a common ECG description used in emergency care, cardiology clinics, and inpatient units. Because some causes can be serious, it is treated as an important clinical finding rather than a single diagnosis.

LBBB stands for **left bundle branch block**. It is an **electrical conduction abnormality** seen on an electrocardiogram (ECG/EKG). It means the heart’s usual electrical signal reaches the **left ventricle later than expected**. LBBB is commonly discussed in cardiology when interpreting ECGs and evaluating heart function.

Left Bundle Branch Block is an electrical conduction pattern seen on an electrocardiogram (ECG/EKG). It means the heart’s left-sided conduction pathway is delayed or blocked, so the ventricles activate out of sync. It is commonly discussed when evaluating symptoms, heart structure, and heart function. It can also affect how clinicians interpret other ECG findings.

RBBB is an abbreviation for **right bundle branch block**. It describes a **pattern on an electrocardiogram (ECG/EKG)** showing slowed electrical conduction through the right side of the heart’s wiring system. RBBB can be found in people with or without heart disease. It is commonly discussed in ECG reports, emergency evaluations, and cardiology clinic visits.

Right Bundle Branch Block is an electrocardiogram (ECG) finding that reflects slowed or blocked electrical conduction in the heart’s right bundle branch. It means the right ventricle is activated later than usual, so the ECG pattern changes in predictable ways. It is commonly discussed in routine ECG interpretation, emergency evaluations, and pre-operative cardiac assessments.

Bundle Branch Block is a finding that describes slowed or blocked electrical conduction in part of the heart’s wiring system. It is most often identified on an electrocardiogram (ECG/EKG). It can occur on the right side (right bundle) or left side (left bundle) of the conduction system. Clinicians use it as a clue to underlying heart conditions and to interpret symptoms and test results.

Complete Heart Block is a heart rhythm condition where electrical signals from the top chambers do not reliably reach the bottom chambers. It is also called third-degree atrioventricular (AV) block. It can cause a slow heartbeat, dizziness, fainting, or no symptoms at all. Clinicians most commonly identify it on an electrocardiogram (ECG) and use the diagnosis to guide monitoring and treatment planning.

Third-Degree AV Block is a heart rhythm condition where electrical signals from the atria do not reach the ventricles. It is also called “complete heart block.” Because the ventricles then rely on a slower backup rhythm, the pulse can be very slow or unstable. The term is commonly used in ECG interpretation, emergency care, inpatient cardiology, and pacemaker decision-making.

Mobitz II is a specific type of second-degree atrioventricular (AV) block, meaning some electrical signals from the atria do not reach the ventricles. It is recognized on an electrocardiogram (ECG/EKG) when beats are “dropped” without the usual gradual warning pattern. Mobitz II is commonly used as a diagnostic term in cardiology, emergency care, and inpatient telemetry monitoring.

Mobitz I is a type of second-degree atrioventricular (AV) block, meaning some atrial electrical signals do not reach the ventricles. It is also called *Wenckebach* and is recognized by a characteristic pattern on an electrocardiogram (ECG/EKG). In plain terms, the heart’s “wiring” pauses intermittently, usually at the AV node, causing an occasional missed beat. Clinicians most often use the term Mobitz I when interpreting ECGs, telemetry monitoring, or ambulatory rhythm recordings.

Second-Degree AV Block is a heart rhythm condition where some electrical signals from the atria do not reach the ventricles. It can cause “dropped” heartbeats because ventricular beats are intermittently missing. It is most commonly recognized on an electrocardiogram (ECG/EKG) or heart rhythm monitor. Clinicians use the term to describe a specific pattern of slowed or interrupted conduction through the AV (atrioventricular) pathway.

First-Degree AV Block is an electrocardiogram (ECG) finding where electrical conduction from the atria to the ventricles is delayed. In plain terms, the heart’s “wiring signal” still gets through, but it takes longer than usual. It is most commonly identified on a routine ECG in clinics, emergency departments, and pre-operative evaluations. Clinicians use it as a descriptive rhythm diagnosis that can help guide context-specific evaluation.

Sinus Node Dysfunction is a problem with the heart’s natural pacemaker, the sinus node. It can cause the heart rate to be too slow, to pause, or to alternate between slow and fast rhythms. It is commonly discussed when evaluating symptoms like fainting, fatigue, or unexplained dizziness. It is also a frequent topic in decisions about heart rhythm monitoring and pacemaker therapy.

Sick Sinus Syndrome is a group of heart rhythm problems caused by malfunction of the sinus node, the heart’s usual natural pacemaker. It commonly leads to heart rates that are too slow, pause unexpectedly, or alternate between slow and fast rhythms. In clinical practice, it is used as a diagnostic term to explain symptoms such as fainting, dizziness, or fatigue linked to rhythm disturbances. It is discussed in cardiology clinics, emergency settings, and electrophysiology (heart rhythm) evaluations.

Sinus Tachycardia is a faster-than-usual heart rate that starts from the heart’s normal pacemaker. It reflects a normal electrical pathway, but with quicker signaling than expected for the situation. It is commonly identified on an electrocardiogram (ECG/EKG) during symptom evaluation or vital-sign checks. It can be a normal response to stress or a clue to an underlying medical condition.