Pacing and heart blocks Flashcards
Which of the following is most likely to cause a first‐degree AV block?
A. Myocardial ischemia
B. Increased vagal tone, as seen in athletes
C. Severe electrolyte imbalance
D. Structural heart disease exclusively
Answer: B
Rationale: First‐degree AV block can be seen in healthy individuals, particularly athletes, due to high vagal tone. It is not necessarily associated with structural disease
In Mobitz type I (Wenckebach) second‐degree AV block, what EKG pattern is characteristic?
A. A constant PR interval with intermittent dropped beats
B. Progressive prolongation of the PR interval until a beat is dropped
C. Complete dissociation between P waves and QRS complexes
D. Wide QRS complexes with fixed PR intervals
Answer: B
Rationale: Wenckebach is characterized by progressive lengthening of the PR interval until a beat is dropped, often benign and reversible.
Which clinical situation is most concerning for progression from a first-degree block to a higher-degree block?
A. In a healthy athlete with high vagal tone
B. In a patient with an acute myocardial infarction
C. In a patient taking a low dose of beta blockers
D. In a patient with well-controlled hypertension
Answer: B
Rationale: In the setting of acute myocardial infarction, conduction disturbances can worsen and progress to higher-degree blocks, posing a risk to life
How does Mobitz type II second-degree AV block differ from Mobitz type I on an EKG?
A. It has progressively lengthening PR intervals
B. The PR intervals remain constant for conducted beats with sudden dropped beats
C. It is always associated with a wide QRS complex
D. It is characterized by atrial fibrillation
Answer: B
Rationale: In Mobitz type II, the PR interval is constant among conducted beats, with unexpected dropped beats, which is more likely to progress to complete heart block.
Which dysrhythmia is most likely to compromise cardiac output and “kill your patient” if untreated?
A. First-degree AV block
B. Mobitz type I second-degree AV block
C. Third-degree (complete) AV block
D. Occasional premature atrial contractions
Answer: C
Rationale: Complete (third-degree) AV block causes AV dissociation and often results in a slow escape rhythm that may lead to hemodynamic instability, shock, and death if not managed.
What is the typical management for an asymptomatic patient with a first-degree AV block?
A. Immediate pacemaker implantation
B. Observation and management of underlying causes
C. Administration of atropine
D. Synchronized cardioversion
Answer: B
Rationale: Asymptomatic first-degree AV block is generally benign and requires no treatment beyond monitoring and addressing any underlying conditions.
Which of the following is a common cause of heart block that may be iatrogenic (“what will harm your patient”) if not recognized?
A. Digitalis toxicity
B. Hyperkalemia
C. Excessive exercise
D. Hypothyroidism
Answer: A
Rationale: Digitalis toxicity can precipitate various degrees of heart block and should be recognized promptly to avoid harm.
In third-degree AV block, what describes the relationship between atrial and ventricular activity?
A. The atria and ventricles contract in synchrony
B. The ventricles are paced by the SA node
C. The atria and ventricles are completely dissociated
D. The PR interval is consistently prolonged
Answer: C
Rationale: In complete heart block, there is total dissociation between atrial and ventricular rhythms, which can severely compromise cardiac output.
Which of the following patients is most likely to require a permanent pacemaker?
A. A patient with first-degree AV block and no symptoms
B. A patient with Mobitz type I AV block that is asymptomatic
C. A patient with symptomatic third-degree AV block
D. A patient with occasional PACs
Answer: C
Rationale: Symptomatic complete heart block that leads to decreased cardiac output typically requires permanent pacing.
What does “sensing” in a pacemaker system refer to?
A. The ability of the pacemaker to deliver electrical stimuli
B. The pacemaker’s capacity to detect intrinsic cardiac electrical activity
C. The conversion of electrical energy into mechanical contraction
D. The adjustment of pacing rate according to metabolic demand.
Answer: B
Rationale: Sensing is the pacemaker’s function to detect the patient’s intrinsic cardiac signals, preventing unnecessary pacing
Which of the following pacemaker modes indicates that the device paces and senses in the ventricle, with pacing inhibited by intrinsic ventricular activity?
A. VVI
B. AAI
C. DDD
D. VOO
Answer: A
Rationale: In VVI mode, the pacemaker paces the ventricle and senses ventricular activity; if an intrinsic beat is sensed, pacing is inhibited.
What is “capture” in the context of pacemaker function?
A. The pacemaker’s ability to sense intrinsic beats
B. The successful depolarization of the myocardium following a pacemaker stimulus
C. The process of increasing the pacing threshold
D. The inhibition of pacing due to oversensing
Answer: B
Rationale: Capture refers to the myocardium’s successful response (depolarization) following a pacemaker’s electrical stimulus.
Which complication of pacemaker therapy involves a pacer spike without subsequent cardiac depolarization?
A. Oversensing
B. Failure to capture
C. Failure to sense
D. Asynchronous pacing
Answer: B
Rationale: Failure to capture occurs when a pacemaker spike does not result in myocardial depolarization, potentially leading to bradycardia and inadequate cardiac output
What is the hallmark electrocardiographic finding in first‐degree AV block?
A. Dropped QRS complexes
B. Progressive PR prolongation with a dropped beat
C. A consistent PR interval longer than 0.20 seconds
D. Complete dissociation between P waves and QRS complexes
Answer: C
Rationale: First‐degree AV block is defined by a prolonged, yet consistent, PR interval (>0.20 seconds) with 1:1 conduction, and is usually benign.
Oversensing by a pacemaker can lead to which of the following complications?
A. Inappropriate inhibition of pacing
B. Excessive pacing causing tachycardia
C. Improved battery longevity
D. Increased atrial kick
.
Answer: A
Rationale: Oversensing results in the pacemaker detecting extraneous signals as intrinsic beats, causing it to inappropriately withhold necessary pacing, which can lead to dangerous bradycardia
In a patient with third-degree AV block and a ventricular escape rhythm at 35 bpm, which immediate complication is most concerning?
A. Hypertension
B. Adequate cardiac output
C. Inadequate perfusion leading to syncope or shock
D. Enhanced exercise tolerance
Answer: C
Rationale: A slow ventricular escape rhythm (20–40 bpm) can lead to insufficient cardiac output, resulting in syncope, shock, and ultimately death if not managed.
Which factor is most likely to precipitate progression of a first-degree AV block to a higher-degree block?
A. Mild dehydration
B. Acute myocardial infarction
C. Routine exercise
D. Controlled hyperthyroidism
Answer: B
Rationale: Acute MI can damage conduction tissue, potentially worsening a first-degree block into a higher-degree block, which can be life-threatening
A patient on beta blockers for hypertension develops a new first-degree AV block. The appropriate initial management is to:
A. Increase the beta blocker dose
B. Discontinue beta blockers immediately
C. Monitor and assess for symptoms, addressing any underlying issues
D. Implant a pacemaker.
Answer: C
Rationale: Asymptomatic first-degree AV block is usually benign; management is conservative, focusing on monitoring and addressing any reversible causes
In pacemaker-dependent patients, which complication can “kill your patient” if not detected promptly?
A. Failure to sense, leading to unnecessary pacing
B. Failure to capture, resulting in loss of effective cardiac pacing
C. Oversensing minor electrical noise
D. Slight battery voltage fluctuation.
Answer: B
Rationale: Failure to capture (i.e., when the pacemaker spike does not result in a myocardial contraction) can lead to dangerous bradycardia and hemodynamic collapse
When interrogating a pacemaker, which finding indicates “oversensing”?
A. Regular pacer spikes with appropriate QRS complexes
B. Frequent pacer inhibition despite the absence of intrinsic rhythm
C. Constant pacing at a fixed rate
D. A sudden increase in battery voltage
Answer: B
Rationale: Oversensing occurs when the device detects extraneous signals and inappropriately withholds pacing, potentially leading to bradycardia.
A patient with third-degree AV block is found to have a narrow QRS escape rhythm at 50 bpm. This is most consistent with:
A. A ventricular escape rhythm
B. A junctional escape rhythm
C. Sinus rhythm with conduction delay
D. Accelerated idioventricular rhythm.
Answer: B
Rationale:
A narrow QRS in third-degree block suggests that the escape rhythm originates from the AV junction, which typically produces a rate between 40 and 60 bpm
Which pacemaker mode is generally preferred for a patient with sinus node dysfunction to maintain AV synchrony and optimize cardiac output?
A. VVI
B. AAI
C. DDD
D. VOO
Answer: C
Rationale: Dual-chamber (DDD) pacing preserves AV synchrony, maintaining the atrial contribution (“atrial kick”) to ventricular filling, which is especially beneficial in sinus node dysfunction.
In a patient with suspected pacemaker failure, which clinical sign would be most concerning?
A. Occasional premature beats
B. Pacemaker spikes on the monitor without subsequent capture
C. Stable heart rate with consistent capture
D. Mild fatigue
Answer: B
Rationale: Pacemaker spikes without capture indicate failure of the myocardium to respond to the electrical stimulus, leading to inadequate heart rates and potential hemodynamic compromise.
Which reversible cause of heart block should be promptly corrected to avoid progression of dysrhythmia?
A. Digitalis toxicity
B. Well-controlled hyperlipidemia
C. Mild dehydration
D. History of migraine headaches
Answer: A
Rationale: Digitalis toxicity can precipitate or worsen heart block; correcting the toxicity can reverse the conduction abnormality and prevent further complications.
What is the significance of an “escape rhythm” in the setting of third-degree AV block?
A. It indicates complete failure of the cardiac conduction system
B. It is a compensatory mechanism that maintains minimal cardiac output
C. It guarantees normal cardiac output
D. It only occurs in pediatric patients
Answer: B
Rationale: An escape rhythm is the heart’s protective mechanism to maintain a minimal ventricular rate in complete block, although it may be insufficient to support full cardiac output.
Which of the following is a common cause of iatrogenic heart block?
A. Excessive exercise
B. Beta-blocker or calcium channel blocker overuse
C. Overhydration
D. High salt intake
Answer: B
Rationale: Overuse or high doses of AV nodal blocking agents (beta-blockers, calcium channel blockers) can lead to iatrogenic heart block.
In pacemaker programming, what does the “VVI” mode indicate?
A. The pacemaker paces the atrium and senses in the ventricle
B. The pacemaker paces and senses in the ventricle, inhibiting pacing when intrinsic beats occur
C. The pacemaker paces both atrium and ventricle, and is rate-adaptive
D. The pacemaker is turned off
Answer: B
Rationale: In VVI mode, the device is set to pace and sense in the ventricle; if an intrinsic ventricular beat is sensed, pacing is inhibited
Which of the following best describes “asynchronous pacing” (e.g., VOO mode)?
A. The pacemaker senses and inhibits pacing as needed
B. The pacemaker paces without sensing intrinsic cardiac activity
C. The pacemaker alternates between atrial and ventricular pacing
D. The pacemaker adjusts the pacing rate based on patient activity].
Answer: B
Rationale: In asynchronous pacing (VOO mode), the pacemaker delivers fixed pacing pulses without sensing the patient’s intrinsic rhythm, which can be dangerous if intrinsic beats occur
What is the potential harm (“what will harm your patient”) of using an asynchronous pacemaker mode (e.g., VOO) in a patient with intrinsic conduction?
A. It improves synchronization of cardiac output
B. It may result in R-on-T phenomena, inducing malignant arrhythmias
C. It optimizes atrioventricular synchrony
D. It prolongs the battery life of the pacemaker
Answer: B
Rationale: Asynchronous pacing can deliver a pacing stimulus during a vulnerable period (R-on-T), increasing the risk of triggering ventricular arrhythmias.
In evaluating a patient with a pacemaker, why is it important to assess the pacemaker’s “capture” function?
A. To ensure the device is properly detecting intrinsic beats
B. To confirm that each pacing stimulus results in myocardial depolarization
C. To measure the battery voltage
D. To evaluate the patient’s cholesterol levels
.
Answer: B
Rationale: Assessing capture ensures that each pacemaker output produces an effective contraction; loss of capture can lead to dangerous bradycardia
Which of the following is a common long-term complication in pacemaker patients that could “harm your patient” if unaddressed?
A. Lead fracture or dislodgement
B. Improved heart rate variability
C. Increased exercise tolerance
D. Reduced risk of arrhythmias.
Answer: A
Rationale: Lead fracture or dislodgement can result in failure to sense or capture, leading to inadequate pacing and potential hemodynamic compromise
Which intervention is recommended for a patient with symptomatic third-degree AV block who does not respond to atropine?
A. Observation only
B. Transvenous pacemaker insertion
C. Increase beta-blocker dosage
D. Administer adenosine
Answer: B
Rationale: Symptomatic complete heart block unresponsive to atropine requires pacing support, often through transvenous pacemaker insertion.
In the context of heart blocks, which finding on an EKG is “really common” in an otherwise healthy individual (e.g., athletes)?
A. Third-degree AV block
B. First-degree AV block with a mildly prolonged PR interval
C. Mobitz type II second-degree AV block
D. Complete AV dissociation
Answer: B
Rationale: First-degree AV block with a slightly prolonged PR interval is commonly seen in healthy, well-conditioned individuals (e.g., athletes) due to increased vagal tone.
What role does “rate-adaptive” pacing play in patient management?
A. It automatically adjusts the pacing rate based on sensed activity, improving cardiac output during exercise
B. It delivers a fixed rate regardless of activity level
C. It only paces the atrium
D. It is used to slow the heart rate in tachyarrhythmias
Answer: A
Rationale: Rate-adaptive pacing adjusts the pacing rate in response to the patient’s activity level, ensuring appropriate cardiac output during varying levels of demand.
Which of the following statements best explains the potential danger of Mobitz type II second-degree AV block?
A. It is usually benign and does not progress
B. It often progresses to complete (third-degree) AV block
C. It is always associated with a wide QRS
D. It only occurs in athletes
Answer: B
Rationale: Mobitz type II block is concerning because it can progress to complete heart block, which can be life-threatening due to severe bradycardia and loss of AV synchrony.
