EKG stands for electrocardiogram. It is a test that records the electrical activity of the heart over a period of time.

The P wave reflects atrial depolarization, which is the electrical activation of the atria. It is the first wave seen in a normal EKG tracing.

The QRS complex represents the rapid depolarization of the ventricles, which leads to ventricular contraction. It is a critical component in assessing ventricular function.

The T wave reflects the process of ventricular repolarization after the contraction of the ventricles. It shows the recovery phase of the ventricular muscle.

The ST segment is the flat section of the EKG that follows the QRS complex and precedes the T wave. It represents the time interval when the ventricles are in a depolarized, uniform state.

A prolonged PR interval indicates slowed conduction between the atria and the ventricles, a hallmark of first-degree AV block. This condition, while sometimes benign, can provide clues about underlying conduction issues.

A widened QRS complex suggests a delay or abnormal conduction in the ventricles, often seen in conditions like bundle branch blocks. This abnormality indicates that the normal, rapid propagation of the electrical impulse is altered.

Peaked T waves are a classic indicator of hyperkalemia. High levels of potassium alter the repolarization process, producing the distinctive tall, sharp T waves seen on an EKG.

ST segment elevation is a key finding in the EKG of a patient experiencing an acute myocardial infarction. It signifies injury to the myocardium and is used to guide urgent treatment decisions.

Atrial fibrillation is marked by an irregularly irregular rhythm and the absence of consistent P waves. These features make it distinguishable from other arrhythmias and are critical for proper diagnosis and management.

Atrial flutter typically presents with a saw-tooth pattern on the EKG, representing rapid, regular atrial contractions. This pattern helps differentiate it from other supraventricular tachyarrhythmias.

The normal QRS complex duration ranges from 60 to 100 milliseconds, indicating rapid and coordinated ventricular depolarization. Values outside this range suggest underlying conduction abnormalities.

Lead II is preferred for examining P wave morphology because its electrical axis aligns well with atrial depolarization. This makes it useful in assessing atrial rhythm and conduction.

Mobitz Type I (Wenckebach) block is identified by a progressive increase in the PR interval until a beat is dropped. This cyclical pattern is a defining feature of the condition.

Sinus arrhythmia is a normal, physiological variation in heart rate, often seen with breathing. It is commonly observed in young, healthy individuals and is not typically indicative of pathology.

A pathological Q wave is a sign of previous myocardial infarction, indicating that myocardial tissue has been replaced by scar tissue. Its presence confirms irreversible damage and an area of infarction.

Reentrant tachycardia is caused by a looping electrical impulse that re-excites the heart tissue via alternate pathways. This mechanism is key in many supraventricular and ventricular tachycardias.

Assessing the heart's electrical axis provides insights into the direction of depolarization, which can uncover underlying issues like chamber enlargement or conduction block. Deviations from the normal axis may suggest structural or electrical abnormalities.

Hypocalcemia leads to a prolonged QT interval due to a delay in ventricular repolarization. This change on the EKG is an important indicator of low calcium levels and can predispose to arrhythmias.

The described chaotic and irregular activity with absent QRS complexes is characteristic of ventricular fibrillation, a life-threatening emergency. Immediate defibrillation is required to restore an effective rhythm and prevent cardiac arrest.