Ventricular Arrhythmias and Bundle-Branch Block

Vocabulary flashcards covering key terms, ECG criteria, and definitions regarding ventricular arrhythmias and bundle-branch blocks from NURS 235.

Ventricular Arrhythmias

Cardiac rhythms originating below the bundle of His in a pacemaker site within the right or left ventricle, characterized by impulse conduction through muscle fibers, wide QRS complexes ($\ge 0.12\text{ seconds}$), ST segment and T wave changes sloped opposite to the QRS deflection, and absent P waves.

Bundle-Branch Block (BBB)

A conduction block located within the ventricles causing asynchronous ventricular depolarization, characterized by a wide QRS complex ($\ge 0.12\text{ seconds}$) often featuring a notched R wave, while usually maintaining an underlying sinus rhythm with normal P waves and PR intervals ($0.12\text{ to }0.20\text{ seconds}$).

Premature Ventricular Contraction (PVC)

A premature ectopic impulse originating below the bundle of His in the ventricles resulting from enhanced automaticity, reentry, or triggered activity, producing a wide QRS complex ($\ge 0.12\text{ seconds}$) and usually followed by a compensatory pause.

Bigeminal PVCs

A repetitive pattern of premature ventricular contractions in which a PVC occurs every second beat.

Trigeminal PVCs

A repetitive pattern of premature ventricular contractions in which a PVC occurs every third beat.

Quadrigeminal PVCs

A repetitive pattern of premature ventricular contractions in which a PVC occurs every fourth beat.

Couplet of PVCs

Two premature ventricular contractions occurring consecutively in a row.

Unifocal PVCs

Premature ventricular contractions that originate from a single ectopic focus in the ventricles and appear identical in shape on an ECG.

Multifocal PVCs

Premature ventricular contractions that originate from different ectopic sites in the ventricles and display varying morphologies on an ECG.

R-on-T PVC

A premature ventricular contraction that occurs during ventricular repolarization, falling directly on the preceding T wave.

Ventricular Escape Beat

An ectopic ventricular impulse that occurs late following a pause in the underlying rhythm rather than prematurely, serving as a protective mechanism.

Idioventricular Rhythm (IVR)

A slow ventricular rhythm originating in a ventricular pacemaker site at a rate of $30\text{ to }40\,\text{bpm}$ or less, featuring a regular rhythm, absent P waves, non-measurable PR intervals, and wide QRS complexes ($\ge 0.12\text{ seconds}$).

Agonal Rhythm

An idioventricular rhythm with a rate below $20\,\text{bpm}$ characterized by irregular, wide, and indistinguishable QRS complexes, commonly known as a 'dying heart' rhythm.

Accelerated Idioventricular Rhythm (AIVR)

A ventricular rhythm originating in an ectopic ventricular pacemaker site at a rate of $50\text{ to }100\,\text{bpm}$, featuring absent P waves and wide QRS complexes ($\ge 0.12\text{ seconds}$).

Ventricular Tachycardia (VT)

A rapid rhythm originating from an ectopic focus in the ventricles at a rate of $140\text{ to }250\,\text{bpm}$, featuring a regular or slightly irregular rhythm, absent associated P waves, and wide QRS complexes ($\ge 0.12\text{ seconds}$).

Ventricular Flutter

A rapid ventricular rhythm occurring when ventricular tachycardia accelerates to a rate greater than $250\,\text{bpm}$.

Non-sustained VT

A brief run or burst of ventricular tachycardia that lasts for less than $30\text{ seconds}$.

Sustained VT

A life-threatening ventricular tachycardia episode lasting longer than $30\text{ seconds}$, capable of degenerating into ventricular fibrillation or asystole.

Torsade de Pointes

A specific type of polymorphic ventricular tachycardia in which the QRS complexes change polarity as they twist around the isoelectric line, strongly associated with prolonged QT intervals and electrolyte imbalances.

Ventricular Fibrillation (VF)

A chaotic, irregular cardiac rhythm caused by rapid, erratic electrical impulses in the ventricles, resulting in no effective myocardial contraction, absent QRS complexes, and no pulse.

Coarse VF

A form of ventricular fibrillation characterized by larger wavy deflections, indicating recent onset and a higher likelihood of successful defibrillation.

Fine VF

A form of ventricular fibrillation characterized by small, low-amplitude waves resembling asystole, indicating later onset requiring CPR and medication prior to defibrillation.

Ventricular Standstill (Asystole)

The complete absence of ventricular electrical activity, presenting on an ECG as a flat line or as sinus P waves without QRS complexes.

Pulseless Electrical Activity (PEA)

A clinical situation where an organized electrical rhythm is visible on the cardiac monitor, but no palpable peripheral pulse is present.

H's and T's

A clinical mnemonic representing reversible underlying causes of cardiac arrest: Hypovolemia, Hypoxia, Hydrogen ions (acidosis), Hypothermia, Hypo/hyperkalemia, Hypoglycemia, Toxins, Tamponade (cardiac), Tension pneumothorax, and Thrombosis.