Mixed Deck — All CRAT Topics Flashcards

Which of the following ECG findings is the defining characteristic of Second-Degree AV Block, Mobitz I (Wenckebach)?

Answer: Progressive lengthening of the PR interval until a QRS complex is dropped.

The hallmark of Second-Degree AV Block, Mobitz I (Wenckebach) is the progressive prolongation of the PR interval over several beats, culminating in a P wave that is not followed by a QRS complex (a dropped beat). [2, 6, 18] After the dropped beat, the cycle typically repeats.

Which of these is a method that can be used to calculate the ventricular rate of a cardiac rhythm when the R-R is regular?

Answer: Divide the number of large boxes between 2 R waves into 300

Explanation: To calculate the ventricular rate when the R-R intervals are regular, divide 300 by the number of large boxes between two consecutive R waves on the ECG strip. This method provides an estimate of the heart rate in beats per minute (bpm).

When a patient with a pacemaker is receiving electrocautery during surgery, which pacemaker problem can occur?

Answer: Oversensing of electrocautery current causing pacemaker inhibition

Electrosurgical (Bovie) current can be sensed by the pacemaker as cardiac activity (oversensing), inhibiting pacing output — dangerous in pacemaker-dependent patients who may develop bradycardia or asystole.

An ECG shows a QRS of 0.14 sec with broad notched R waves in I, aVL, V5–V6 and a broad QS in V1. What is the most likely diagnosis?

Answer: Left bundle branch block

Broad notched R waves in lateral leads (I, aVL, V5–V6) combined with a QS pattern in V1 and a QRS ≥0.12 seconds are the hallmark features of left bundle branch block.

Why should the defibrillator be kept readily accessible near monitored patients in the cardiac care unit?

Answer: Life-threatening arrhythmias such as VF or pulseless VT can occur without warning and require immediate defibrillation

Immediate defibrillation within the first minutes of VF is the most critical determinant of survival, so defibrillators must be immediately available in monitored care settings.

Procainamide's primary antiarrhythmic mechanism is:

Answer: Blocking fast sodium channels to slow conduction

Procainamide is a Class IA sodium channel blocker that slows intraventricular conduction and prolongs the refractory period.

A CRAT notices on a patient's monitor that the pacemaker intermittently stops firing, causing long pauses, especially when the patient moves their arm or coughs. The technician suspects the pacemaker is incorrectly identifying muscle artifact as cardiac signals. This malfunction is known as:

Answer: Oversensing

Oversensing is when the pacemaker incorrectly interprets non-cardiac electrical signals (like skeletal muscle artifact, T-waves, or EMI) as intrinsic cardiac activity. This misinterpretation inhibits the pacemaker from delivering a pacing stimulus when it's actually needed, potentially leading to pauses or syncope. [1, 5, 6]

A patient with a DDD pacemaker has an underlying sinus bradycardia. The ECG shows a pacing spike immediately followed by a P wave, which is then followed by a second pacing spike and a wide QRS complex. This pattern repeats consistently. What is the correct interpretation?

Answer: AV sequential pacing

This pattern represents normal AV sequential pacing in a dual-chamber (DDD) pacemaker. The first spike paces the atrium because the intrinsic rate is too slow. The pacemaker then waits for a programmed AV delay. If an intrinsic QRS does not appear within that time, the pacemaker delivers a second stimulus to pace the ventricle. This ensures both atrial and ventricular contraction are synchronized. [2, 11, 13]

Which waveform represents ventricular repolarization on an ECG strip?

Answer: T wave

Explanation: The T wave on an ECG represents ventricular repolarization, which is the phase of the cardiac cycle when the ventricles reset their electrical state in preparation for the next contraction.

Magnesium sulfate is the treatment of choice for:

Answer: Torsades de Pointes

IV magnesium sulfate is the first-line treatment for Torsades de Pointes because it stabilizes the cardiac membrane and shortens the QT interval.

In right bundle branch block, a wide, slurred S wave is characteristically seen in which leads?

Answer: I, aVL, V5, and V6

The terminal slurred S wave in leads I, aVL, V5, and V6 represents the delayed right ventricular depolarization force traveling away from these left-sided lateral leads in RBBB.

Atropine is administered in cardiac emergencies primarily to treat:

Answer: Symptomatic bradycardia

Atropine blocks vagal (parasympathetic) tone to increase heart rate and is the first-line drug for symptomatic bradycardia per ACLS guidelines.

Mobitz type I (Wenckebach) second-degree AV block is best described by which pattern?

Answer: Progressive PR lengthening until a QRS is dropped, then the cycle resets

Wenckebach is characterized by progressive PR interval lengthening with each beat until one P wave is not conducted (dropped QRS), after which the cycle resets.

When performing a 12-lead ECG, the RL (right leg) electrode serves primarily which purpose?

Answer: Electrical ground/reference to reduce common-mode noise

The right leg electrode serves as the ground electrode, providing a common reference point that helps the ECG machine cancel out common-mode electrical noise affecting all leads equally.

Synchronized cardioversion is indicated for which of the following rhythms?

Answer: Unstable supraventricular tachycardia with a pulse

Synchronized cardioversion delivers a shock timed to the R wave and is used for unstable tachyarrhythmias with a pulse, avoiding accidental delivery during the T wave.

A patient's ECG shows a P wave in every beat, upright in lead II, with a constant PR interval of 220 ms and a rate of 72 bpm. What is the correct interpretation?

Answer: Normal sinus rhythm with first-degree AV block

Rate is 72 bpm (normal sinus range), P waves are upright in II (sinus origin), and PR interval is 220 ms — above the 200 ms upper limit — indicating first-degree AV block superimposed on otherwise normal sinus rhythm.

A rhythm strip shows an upright P wave before every QRS complex, a regular R-R interval, a ventricular rate of 72 bpm, a PR interval of 0.16 seconds, and a QRS duration of 0.08 seconds. How would this rhythm be interpreted?

Answer: Normal Sinus Rhythm

This rhythm meets all the criteria for Normal Sinus Rhythm: a heart rate between 60-100 bpm, a regular rhythm, a P wave preceding every QRS complex, a constant PR interval between 0.12-0.20 seconds, and a QRS duration less than 0.12 seconds.

A reentrant arrhythmia requires which three conditions to be established and maintained?

Answer: A closed circuit pathway, unidirectional block in one limb, and slow conduction in the other limb allowing recovery

Reentry requires an anatomical or functional circuit with two pathways, unidirectional block in one pathway (impulse cannot go forward but can conduct backward), and slow enough conduction in the alternate pathway that the blocked pathway recovers and can be re-excited.

Which of the following ECG characteristics is the most definitive feature of Ventricular Fibrillation (VF)?

Answer: Chaotic, disorganized electrical activity with no identifiable P, QRS, or T waves.

Ventricular Fibrillation is defined by its chaotic and disorganized nature. On the ECG, there are no discernible waves (P, QRS, T); instead, the baseline is wavy and chaotic, reflecting the quivering, uncoordinated contraction of the ventricles.

A characteristic of a third-degree AVB is:

Answer: The conduction of the atrial impulse failing to reach the ventricle

Explanation: In third-degree atrioventricular block (AVB), also known as complete heart block, the atrial electrical impulses fail to conduct to the ventricles. This results in an independent rhythm between the atria and ventricles, leading to the characteristic dissociation between P waves and QRS complexes on an ECG.