SA NODE DYSFUNCTION Flashcards
Which of the following is a definite indication for permanent pacemaker implantation in a patient with sinus node dysfunction (SND)?
A. Asymptomatic sinus bradycardia
B. Symptoms directly attributable to SND
C. Sinus bradycardia that resolves with medication adjustment
D. Atrial fibrillation with a controlled ventricular rate
Answer: B. Symptoms directly attributable to SND
Rationale: Permanent pacing is indicated when symptoms can be directly attributed to sinus node dysfunction. Asymptomatic bradycardia or bradycardia that improves with medication adjustments does not warrant pacemaker implantation.
Which of the following patients with sinus bradycardia would most likely benefit from permanent pacemaker implantation?
A. A 70-year-old with symptomatic sinus bradycardia but is on beta-blockers for coronary artery disease, with no alternative medication
B. A 60-year-old with asymptomatic sinus bradycardia and a resting heart rate of 48 bpm
C. A 55-year-old with sinus bradycardia who experiences mild dizziness but has no other symptoms
D. A 75-year-old with episodic palpitations due to paroxysmal atrial fibrillation, managed with rate control medications
Answer: A. A 70-year-old with symptomatic sinus bradycardia but is on beta-blockers for coronary artery disease, with no alternative medication
Rationale: Permanent pacing is indicated in patients with symptomatic sinus bradycardia when essential medications (e.g., beta-blockers) cannot be discontinued. Asymptomatic bradycardia does not require pacing.
A 68-year-old male with a history of sinus node dysfunction presents with recurrent episodes of syncope and alternating bradycardia and tachycardia. What is the most likely diagnosis?
A. Atrial flutter
B. Third-degree AV block
C. Tachy-brady syndrome
D. Ventricular tachycardia
Answer: C. Tachy-brady syndrome
Rationale: Tachy-brady syndrome is a form of sinus node dysfunction characterized by alternating bradycardia and tachycardia, often leading to syncope or palpitations. It is a common indication for permanent pacing.
Which of the following statements is true regarding the use of oral theophylline in sinus node dysfunction (SND)?
A. Theophylline is a first-line treatment for SND
B. Theophylline can be considered as a trial in patients with possible SND before deciding on permanent pacing
C. Theophylline is primarily used to slow the heart rate in tachycardia
D. Theophylline is recommended for all patients with symptomatic SND
Answer: B. Theophylline can be considered as a trial in patients with possible SND before deciding on permanent pacing
Rationale: Theophylline is not a first-line therapy but can be used as a trial in patients with uncertain SND-related symptoms to assess the potential benefit of increasing heart rate before considering permanent pacemaker implantation.
Which of the following is NOT an indication for permanent pacing in sinus node dysfunction (SND)?
A. Symptomatic chronotropic incompetence
B. Symptomatic sinus bradycardia with no alternative medication options
C. Symptoms possibly attributable to SND, without further evaluation
D. Tachy-brady syndrome
Answer: C. Symptoms possibly attributable to SND, without further evaluation
Rationale: Permanent pacing is not recommended if symptoms are only “possibly” due to SND without further assessment. In such cases, a trial of theophylline may be considered before proceeding with pacemaker implantation.
A 72-year-old male with sinus node dysfunction is found to have symptomatic sinus bradycardia that correlates with his symptoms. He is on beta-blockers for heart failure, which cannot be discontinued. What is the next best step in management?
A. Observation
B. Trial of oral theophylline
C. Permanent pacemaker implantation
D. Discontinue beta-blockers
Answer: C. Permanent pacemaker implantation
Rationale: If symptoms correlate with bradycardia and are due to required guideline-directed medical therapy (GDMT) with no alternative, permanent pacing is indicated (Class I recommendation). Discontinuing essential medications is not recommended.
A patient with sinus node dysfunction has symptoms that are uncertainly correlated with bradycardia. What is the recommended next step?
A. Observation
B. Trial of oral theophylline
C. Immediate permanent pacemaker implantation
D. Discontinue medications
Answer: B. Trial of oral theophylline
Rationale: If the correlation between symptoms and bradycardia is uncertain, a trial of oral theophylline (Class IIb recommendation) can help assess whether symptoms improve before deciding on permanent pacing.
A 65-year-old with sinus node dysfunction undergoes evaluation. His symptoms do not correlate with bradycardia, and he remains asymptomatic. What is the appropriate management?
A. Permanent pacemaker implantation
B. Oral theophylline
C. Observation
D. Dual chamber pacemaker
Answer: C. Observation
Rationale: If there is no correlation between symptoms and bradycardia, observation is appropriate (Class III: Harm). Permanent pacing is not indicated in asymptomatic patients.
A patient with symptomatic sinus node dysfunction requires permanent pacing but has infrequent pacing needs and significant comorbidities. What is the preferred pacemaker type?
A. Dual chamber pacemaker
B. Single chamber ventricular pacemaker
C. Single chamber atrial pacemaker
D. No pacemaker implantation
Answer: B. Single chamber ventricular pacemaker
Rationale: In patients who require pacing but have infrequent pacing needs and significant comorbidities, single-chamber ventricular pacing (Class IIa recommendation) is a reasonable choice.
A patient with sinus node dysfunction has a normal AV conduction system and requires permanent pacing. What is the preferred pacemaker type?
A. Single chamber ventricular pacemaker
B. Single chamber atrial pacemaker
C. Dual chamber pacemaker
D. No pacemaker implantation
Answer: C. Dual chamber pacemaker
Rationale: In patients with normal AV conduction, a dual chamber pacemaker (Class I recommendation) is preferred to preserve AV synchrony and minimize ventricular pacing.
Which of the following is a Class I indication for permanent pacemaker implantation in sinus node dysfunction (SND)?
A. Sinus bradycardia without symptoms
B. Symptomatic bradycardia directly attributable to SND
C. Asymptomatic sinus bradycardia with a heart rate of 45 beats/min
D. Bradycardia due to the use of nonessential medications
Answer: B. Symptomatic bradycardia directly attributable to SND
Rationale: Class I indications for pacing include documented symptomatic bradycardia and cases where SND-associated bradycardia is due to essential drug therapy with no alternative. Asymptomatic bradycardia and bradycardia due to nonessential drugs do not require pacing.
Which of the following is a Class IIa indication for permanent pacing in sinus node dysfunction (SND)?
A. Sinus bradycardia in an asymptomatic patient
B. SND with syncope of unexplained origin and evidence of SA node dysfunction
C. SND with symptoms that are clearly correlated with bradycardia
D. Bradycardia associated with the use of nonessential medications
Answer: B. SND with syncope of unexplained origin and evidence of SA node dysfunction
Rationale: Class IIa indications include situations where SND is suspected but not documented, such as syncope of unexplained origin in the presence of significant SA node abnormalities. Class I indications require clear symptom correlation with bradycardia.
A patient with sinus node dysfunction (SND) has a heart rate of 38 bpm but reports only mild fatigue without other significant symptoms. What is the appropriate management?
A. Permanent pacemaker implantation (Class I)
B. Permanent pacemaker implantation (Class IIa)
C. Permanent pacemaker implantation (Class IIb)
D. No pacemaker implantation
Answer: C. Permanent pacemaker implantation (Class IIb)
Rationale: Class IIb indications include mildly symptomatic individuals with persistent heart rates <40 bpm. In these cases, pacing may be considered, but it is not a strict recommendation.
Which of the following is a Class III (not indicated) scenario for permanent pacing in sinus node dysfunction (SND)?
A. Symptomatic bradycardia due to SND
B. Sinus bradycardia due to nonessential medication use
C. SND with recurrent syncope and documented SA node dysfunction
D. Symptomatic chronotropic incompetence
Answer: B. Sinus bradycardia due to nonessential medication use
Rationale: Class III indications (not recommended) include asymptomatic bradycardia and cases where bradycardia is due to the use of nonessential medications. In these scenarios, pacing is not beneficial.
Which of the following best describes sinus arrest?
A. Failure of sinus node activity to propagate to the atrium
B. Progressive conduction delay of sinus impulses before a blocked beat
C. Complete failure of impulse formation within the sinus node
D. Progressive shortening of the P-P interval before a sinus pause
Answer: C. Complete failure of impulse formation within the sinus node
Rationale: Sinus arrest occurs when the sinus node fails to generate an impulse, leading to a pause on ECG without a preceding pattern. Sinoatrial exit block (A) refers to failure of the impulse to leave the sinus node and reach the atrium. Choice (D) describes Sinoatrial Wenckebach (Mobitz I SA block).
Which of the following best characterizes tachy-brady syndrome?
A. Atrial fibrillation alternating with symptomatic bradycardia
B. Sinus bradycardia in response to carotid sinus stimulation
C. Heart rate failing to increase during exercise
D. Progressive conduction delay in the sinoatrial node
Answer: A. Atrial fibrillation alternating with symptomatic bradycardia
Rationale: Tachy-brady syndrome is a subset of sinus node dysfunction where atrial fibrillation or tachyarrhythmias alternate with symptomatic bradycardia or sinus pauses. Choice (B) describes carotid sinus hypersensitivity, choice (C) describes chronotropic incompetence, and choice (D) describes SA Wenckebach (Mobitz I SA block).
A 65-year-old man experiences exercise intolerance and inability to increase heart rate despite normal sinus rhythm at rest. His treadmill stress test shows a blunted heart rate response to exercise. What is the most likely diagnosis?
A. Tachy-brady syndrome
B. Chronotropic incompetence
C. Sinoatrial exit block
D. Carotid sinus hypersensitivity
Answer: B. Chronotropic incompetence
Rationale: Chronotropic incompetence (CI) is the inability of the sinus node to appropriately increase heart rate in response to exercise, leading to exercise intolerance. Choice (A) would involve alternating tachycardia and bradycardia, choice (C) involves impulse conduction failure at the SA node, and choice (D) typically presents with syncope due to vagal overactivity.
Which of the following is a potential cause of sinus node dysfunction (SND) due to ischemia?
A. Left anterior descending artery occlusion
B. Circumflex artery occlusion
C. Right coronary artery involvement in acute MI
D. Atrial fibrillation without structural heart disease
Answer: C. Right coronary artery involvement in acute MI
Rationale: The SA node is often supplied by the right coronary artery (RCA), and ischemia or infarction involving this vessel can lead to sinus node dysfunction. Choice (A) primarily affects the anterior wall and left ventricle, choice (B) affects the lateral wall, and choice (D) is unrelated to acute ischemia.
Which of the following statements regarding carotid sinus hypersensitivity is true?
A. It is a rare cause of sinus bradycardia
B. Pacemaker implantation is never indicated
C. It can be associated with vasovagal syncope
D. The vasodepressor response is effectively treated with pacing
Answer: C. It can be associated with vasovagal syncope
Rationale: Carotid sinus hypersensitivity is a cause of sinus bradycardia and syncope and is often related to vasovagal responses. Pacemaker implantation may be beneficial in cases with a predominant cardioinhibitory component. However, vasodepressor effects (D) are not improved by pacing.
The funny current carried by sodium (Na⁺) ions, is the primary pacemaker current responsible for the gradual depolarization of phase 4. T-type and L-type calcium currents contribute later in phase 4, but (potassium current) is responsible for repolarization (phase 3)
Which phase of the SA nodal action potential is characterized by a rapid influx of calcium (Ca²⁺) ions?
A. Phase 0
B. Phase 3
C. Phase 4
D. Resting phase
Answer: A. Phase 0
Rationale: In SA nodal cells, phase 0 (depolarization phase) is due to the inward flow of Ca²⁺ through L-type calcium channels unlike ventricular myocytes where depolarization is mediated by fast sodium (Na⁺) channels.
