Week 2 ECG Conditions

Unstable Angina (UA)

Acute coronary syndrome involving transient myocardial ischemia without myocardial infarction. Caused by transient thrombotic vessel occlusion and vasoconstriction at a damaged plaque site. ECG: most commonly ST-segment depression and T-wave inversion.

NSTEMI

Acute coronary syndrome involving a subendocardial infarction with partial-thickness myocardial damage. ECG: ST-segment depression and T-wave inversion without ST-segment elevation.

STEMI

Acute coronary syndrome involving a transmural infarction with full-thickness myocardial damage from the endocardium to the epicardium. ECG: ST-segment elevation.

Atrial Fibrillation (AFib)

Atrial dysrhythmia caused by rapidly firing electrical potentials in the atrial myocardium, producing an atrial rate of approximately 400–600 bpm. ECG: no visible P waves, fibrillatory waves, irregularly irregular QRS/R-R intervals, and a high ventricular rate.

Atrial Flutter

Atrial dysrhythmia in which the atria contract very rapidly, usually around 300 bpm. Not every atrial impulse is conducted to the ventricles. ECG: sawtooth flutter waves, regular atrial activity, and variable ventricular response.

Premature Atrial Contraction (PAC)

Premature atrial beat caused by a depolarization originating outside the SA node. ECG: premature P wave with an abnormal shape, usually followed by a normal or near-normal QRS complex, followed by a short pause.

Premature Ventricular Contraction (PVC)

Premature ventricular beat caused by an ectopic focus in the ventricle firing before the SA node impulse reaches the ventricles. ECG: premature wide and bizarre QRS complex without a preceding P wave, followed by a compensatory pause.

Ventricular Tachycardia (VTach)

Ventricular dysrhythmia originating in the ventricles with a rapid rate, usually 120–250 bpm. ECG: rapid regular rhythm, wide and bizarre QRS complexes, and QRS complexes not associated with P waves.

Monomorphic Ventricular Tachycardia

A form of VTach in which ventricular impulses originate from the same area of myocardium. ECG: wide QRS complexes with the same shape and symmetrical morphology.

Polymorphic Ventricular Tachycardia

A form of VTach in which ventricular impulses originate from multiple areas of the myocardium. ECG: wide QRS complexes with changing or variable shapes.

Ventricular Fibrillation (VFib)

Life-threatening ventricular dysrhythmia involving chaotic and uncoordinated ventricular electrical activity, causing ineffective contraction and catastrophic loss of cardiac output. ECG: chaotic irregular activity, no recognizable P waves, QRS complexes, or T waves, and a very high rate.

First-Degree AV Block

AV conduction disorder caused by slowed conduction through the AV node, but all atrial impulses still reach the ventricles. ECG: PR interval greater than 0.20 seconds; prolonged but consistent PR interval; every P wave followed by a QRS complex.

Second-Degree AV Block

AV conduction disorder in which some atrial impulses fail to reach the ventricles. ECG: some P waves are not followed by QRS complexes.

Second-Degree AV Block – Mobitz I (Wenckebach)

Second-degree AV block in which AV conduction becomes progressively slower until an atrial impulse is blocked. ECG: PR interval progressively lengthens until a P wave is not followed by a QRS complex; a pause occurs; then the cycle repeats.

Second-Degree AV Block – Mobitz II

More serious second-degree AV block in which some atrial impulses are suddenly blocked, usually due to conduction disease below the AV node. ECG: blocked P waves with dropped QRS complexes; PR interval of conducted beats remains unchanged; QRS complexes may be widened.

Third-Degree AV Block (Complete Heart Block)

Complete AV conduction block in which no atrial impulses reach the ventricles. The atria and ventricles generate impulses independently. ECG: complete AV dissociation; P waves and QRS complexes have no relationship; atrial rate is faster than ventricular rate; ventricular rhythm is slow and regular.