Bradyarrhythmias and conduction disorders US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Bradyarrhythmias and conduction disorders. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Bradyarrhythmias and conduction disorders US Medical PG Question 1: A 75-year-old man presents to the emergency department after an episode of syncope while walking outside with his wife. His wife states that he suddenly appeared pale and collapsed to the ground. She says he remained unconscious for 1 minute. He says he noticed a fluttering in his chest and excessive sweating before the episode. He has type 2 diabetes mellitus, essential hypertension, and chronic stable angina. He has not started any new medications in the past few months. Vital signs reveal: temperature 37.0°C (98.6°F), blood pressure 135/72 mm Hg, and pulse 72/min. Physical examination is unremarkable. ECG shows an old bifascicular block. Echocardiogram and 24-hour Holter monitoring are normal. Which of the following is the best next step in the evaluation of this patient's condition?
- A. Cardiac enzymes
- B. Continuous loop recorder (Correct Answer)
- C. Valsalva maneuver
- D. Electroencephalography (EEG)
- E. Tilt-table test
Bradyarrhythmias and conduction disorders Explanation: ***Continuous loop recorder***
- This patient's syncope is preceded by **palpitations (fluttering in chest)** and **sweating**, suggesting a cardiac etiology, specifically a **transient arrhythmia** not captured on a standard ECG or 24-hour Holter.
- A continuous loop recorder provides prolonged monitoring (months to years), increasing the likelihood of detecting intermittent arrhythmias responsible for syncopal episodes.
*Cardiac enzymes*
- While cardiac enzymes (e.g., troponin) are crucial for evaluating **acute myocardial ischemia** or infarction, the patient presents with syncope and no new chest pain, and his stable angina suggests chronic disease rather than an acute event leading to syncope in this specific instance.
- An **ECG showing an old bifascicular block** and an **unremarkable physical exam** make an acute cardiac event less likely as the primary cause of syncope when an arrhythmia is suspected.
*Valsalva maneuver*
- The Valsalva maneuver is a diagnostic tool often used to differentiate between certain types of **tachyarrhythmias** or to evaluate for **autonomic dysfunction**, but it is not an evaluative step for a patient presenting with unexplained syncope where an arrhythmia has not yet been documented.
- It would not help in identifying the cause of intermittent syncope in a patient whose standard workup has been unremarkable, as it's a test for immediate physiological response, not prolonged cardiac rhythm monitoring.
*Electroencephalography (EEG)*
- EEG is indicated when **seizure disorder** is suspected as the cause of loss of consciousness, often characterized by tonic-clonic movements, post-ictal confusion, or focal neurologic signs, which are absent in this patient's presentation.
- The patient's pre-syncopal symptoms of **palpitations and sweating** point away from a seizure and towards a cardiac cause.
*Tilt-table test*
- A tilt-table test is used to evaluate for **vasovagal syncope** or **postural orthostatic tachycardia syndrome (POTS)**, often considered when other cardiac causes are ruled out or when syncope is typically triggered by prolonged standing.
- Given the patient's pre-syncopal **palpitations**, a **cardiac arrhythmia** remains a higher suspicion than vasovagal syncope at this stage, especially after normal echocardiogram and Holter monitoring, necessitating further arrhythmia investigation.
Bradyarrhythmias and conduction disorders US Medical PG Question 2: A 71-year-old man is brought to the emergency department by his wife because of increasing confusion, weakness, and vomiting for 1 day. He has had 5 episodes of vomiting and blurry vision; he told his wife that "everything appears in different colors." He has been unable to recall his wife's name or their address. His wife reports that his drug regimen was adjusted because of worsening tibial edema 1 week ago. He has congestive heart failure, atrial fibrillation, hypothyroidism, and osteoarthritis. Current medications include rivaroxaban, metoprolol, digoxin, levothyroxine, spironolactone, and furosemide. His temperature is 36.7°C (98°F), pulse is 56/min, and blood pressure is 98/68 mm Hg. He is confused and oriented only to person. Neurologic examination shows no focal findings. The abdomen is soft, and there is tenderness to palpation of both lower quadrants without guarding or rebound. There is 1+ pitting edema of both ankles. This patient is most likely to have which of the following ECG findings?
- A. Low QRS voltage
- B. Increased PR interval (Correct Answer)
- C. Mobitz type 2 atrioventricular block
- D. Prolonged QT interval
- E. Peaked T waves
Bradyarrhythmias and conduction disorders Explanation: ***Increased PR interval***
- The patient's symptoms (confusion, weakness, vomiting, blurry vision with "everything appears in different colors," bradycardia) are classic signs of **digoxin toxicity**. Digoxin primarily affects the **AV node**, leading to slowed conduction and thus an **increased PR interval** on ECG.
- The recent adjustment of his diuretic regimen (spironolactone and furosemide) for worsening edema suggests possible **hypokalemia** or **renal impairment**, which can precipitate digoxin toxicity even at therapeutic levels.
*Low QRS voltage*
- **Low QRS voltage** is typically associated with conditions like **pericardial effusion**, severe hypothyroidism, or diffuse myocardial disease, which are not directly suggested by the patient's acute presentation.
- While the patient has hypothyroidism, acute digoxin toxicity does not primarily cause low QRS voltage.
*Mobitz type 2 atrioventricular block*
- While digoxin toxicity can cause various arrhythmias, **Mobitz type 2 AV block** (characterized by constant PR interval before a dropped beat) usually indicates issues deeper in the His-Purkinje system.
- **First-degree AV block** (increased PR interval) and **Wenckebach (Mobitz type 1) AV block** are more common manifestations of digoxin's direct inhibitory effect on the AV node.
*Prolonged QT interval*
- A **prolonged QT interval** is associated with an increased risk of **Torsades de Pointes** and can be caused by certain antiarrhythmics (e.g., amiodarone, sotalol) or electrolyte imbalances, but it is not a direct or typical ECG finding of digoxin toxicity.
- Digoxin toxicity is more commonly associated with a **shortened QT interval** or "scooping" of the ST segment.
*Peaked T waves*
- **Peaked T waves** are a hallmark of **hyperkalemia**, an electrolyte disturbance that can cause cardiac arrhythmias and muscle weakness.
- While electrolyte imbalances can contribute to digoxin toxicity, peaked T waves themselves are not a direct consequence of digoxin.
Bradyarrhythmias and conduction disorders US Medical PG Question 3: A cardiologist is studying how a new virus that infects the heart affects the electrical conduction system of the cardiac myocytes. He decides to obtain electrocardiograms on patients with this disease in order to see how the wave patterns and durations change over time. While studying these records, he asks a medical student who is working with him to interpret the traces. Specifically, he asks her to identify the part that represents initial ventricular depolarization. Which of the following characteristics is most consistent with this feature of the electrocardiogram?
- A. Elevated in patients with full thickness ischemic injury of the heart
- B. Becomes peaked in states of hyperkalemia
- C. Becomes prominent in states of hypokalemia
- D. Normal duration defined as less than 120 milliseconds (Correct Answer)
- E. Normal duration defined as less than 200 milliseconds
Bradyarrhythmias and conduction disorders Explanation: ***Normal duration defined as less than 120 milliseconds***
- The question asks for the representation of **initial ventricular depolarization**, which corresponds to the **QRS complex** on an ECG.
- The normal duration of the **QRS complex** is typically less than **0.12 seconds (120 milliseconds)**, reflecting efficient ventricular depolarization.
*Elevated in patients with full thickness ischemic injury of the heart*
- This description refers to the **ST segment elevation** seen in **ST-segment elevation myocardial infarction (STEMI)**, which represents myocardial injury, not initial ventricular depolarization.
- While related to cardiac electrical activity, **ST segment elevation** is a consequence of injury and refers to repolarization abnormalities, not the QRS complex itself.
*Becomes peaked in states of hyperkalemia*
- **Peaked T waves** are characteristic of **hyperkalemia**, indicating altered ventricular repolarization, not ventricular depolarization.
- The T wave represents ventricular repolarization, and its morphology changes significantly with potassium imbalances.
*Becomes prominent in states of hypokalemia*
- A **prominent U wave** is sometimes observed in **hypokalemia**, which follows the T wave and is thought to represent repolarization of Purkinje fibers.
- The U wave is distinct from the QRS complex and does not represent initial ventricular depolarization.
*Normal duration defined as less than 200 milliseconds*
- A duration of less than 200 milliseconds (0.20 seconds) typically refers to the normal duration of the **PR interval**, which represents atrial depolarization and conduction through the AV node.
- The **QRS complex** (initial ventricular depolarization) has a shorter normal duration, typically less than 120 milliseconds.
Bradyarrhythmias and conduction disorders US Medical PG Question 4: In a patient with acute myocardial ischemia, which of the following cardiovascular structures is at greatest risk of damage?
- A. Pulmonary valve
- B. Cardiac conduction system (Correct Answer)
- C. Coronary artery
- D. Cardiac septum
- E. Temporal artery
Bradyarrhythmias and conduction disorders Explanation: ***Cardiac conduction system***
- The **cardiac conduction system** is highly dependent on a constant oxygen supply, and its disruption by ischemia can lead to serious **arrhythmias** and **heart blocks**.
- Ischemia in critical areas like the **AV node** (supplied by the RCA) or the **bundle branches** can severely impair the heart's electrical activity.
*Pulmonary valve*
- The **pulmonary valve** is primarily a passive structure and is generally not directly damaged by acute myocardial ischemia.
- Its function is more affected by changes in **pulmonary artery pressure** or **ventricular remodeling**, not immediate ischemic injury.
*Coronary artery*
- While **coronary artery disease (CAD)** is the *cause* of myocardial ischemia, the coronary artery itself is not the structure *damaged* in the sense of functional impairment due to lack of blood flow in acute ischemia.
- The damage occurs downstream in the **myocardium** that the artery supplies.
*Cardiac septum*
- The **cardiac septum** can be damaged by myocardial ischemia, particularly the **interventricular septum**, leading to complications like **septal rupture**.
- However, the conduction system is at *greatest* immediate risk of functional damage leading to life-threatening events due to its critical role in rhythm generation.
*Temporal artery*
- The **temporal artery** is a blood vessel located in the head, entirely separate from the heart.
- It is not involved in myocardial ischemia and is not at risk of damage from a cardiac event.
Bradyarrhythmias and conduction disorders US Medical PG Question 5: A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?
- A. "Does the diarrhea typically precede the constipation, or vice-versa?"
- B. "Is the diarrhea foul-smelling?"
- C. "Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"
- D. "Are the symptoms worse in the morning or at night?"
- E. "Can you tell me more about the symptoms you have been experiencing?" (Correct Answer)
Bradyarrhythmias and conduction disorders Explanation: ***Can you tell me more about the symptoms you have been experiencing?***
- This **open-ended question** encourages the patient to provide a **comprehensive narrative** of their symptoms, including details about onset, frequency, duration, alleviating/aggravating factors, and associated symptoms, which is crucial for diagnosis.
- In a patient presenting with vague, intermittent symptoms like alternating constipation and diarrhea, allowing them to elaborate freely can reveal important clues that might not be captured by more targeted questions.
*Does the diarrhea typically precede the constipation, or vice-versa?*
- While knowing the sequence of symptoms can be helpful in understanding the **pattern of bowel dysfunction**, it is a very specific question that might overlook other important aspects of the patient's experience.
- It prematurely narrows the focus without first obtaining a broad understanding of the patient's overall symptomatic picture.
*Is the diarrhea foul-smelling?*
- Foul-smelling diarrhea can indicate **malabsorption** or **bacterial overgrowth**, which are important to consider in some gastrointestinal conditions.
- However, this is a **specific symptom inquiry** that should follow a more general exploration of the patient's symptoms, as it may not be relevant if other crucial details are missed.
*Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life*
- Quantifying pain intensity is useful for assessing the **severity of discomfort** and monitoring changes over time.
- However, for a patient with intermittent rather than acute, severe pain, understanding the **character, location, and triggers** of the pain is often more diagnostically valuable than just a numerical rating initially.
*Are the symptoms worse in the morning or at night?*
- Diurnal variation can be relevant in certain conditions, such as inflammatory bowel diseases where nocturnal symptoms might be more concerning, or functional disorders whose symptoms might be stress-related.
- This is another **specific question** that should come after gathering a more complete initial picture of the patient's symptoms to ensure no key information is overlooked.
Bradyarrhythmias and conduction disorders US Medical PG Question 6: A 42-year-old Caucasian woman is enrolled in a randomized controlled trial to study cardiac function in the setting of several different drugs. She is started on verapamil and instructed to exercise at 50% of her VO2 max while several cardiac parameters are being measured. During this experiment, which of the following represents the relative conduction speed through the heart from fastest to slowest?
- A. Purkinje fibers > ventricles > atria > AV node
- B. Purkinje fibers > atria > ventricles > AV node (Correct Answer)
- C. Atria > Purkinje fibers > ventricles > AV node
- D. AV node > ventricles > atria > Purkinje fibers
- E. Purkinje fibers > AV node > ventricles > atria
Bradyarrhythmias and conduction disorders Explanation: ***Purkinje fibers > atria > ventricles > AV node***
- The **Purkinje fibers** have the fastest conduction velocity, ensuring rapid and synchronous ventricular depolarization.
- The **atria** conduct impulses faster than the ventricles, but slower than the Purkinje fibers, allowing for atrial contraction before ventricular systole.
*Purkinje fibers > ventricles > atria > AV node*
- This option correctly identifies the **Purkinje fibers** and **AV node** at the fastest and slowest ends, respectively, but incorrectly orders the atria and ventricles.
- While Purkinje fibers are fastest, cardiac muscle cells (atria then ventricles) conduct slower than Purkinje fibers.
*Atria > Purkinje fibers > ventricles > AV node*
- This option incorrectly places the **atria** as having the fastest conduction speed, which is not true as Purkinje fibers are significantly faster.
- It also misorders the Purkinje fibers relative to the atria in terms of speed.
*AV node > ventricles > atria > Purkinje fibers*
- This option is incorrect as it places the **AV node** as the fastest conductor and the **Purkinje fibers** as the slowest, which is the exact opposite of their actual conduction speeds.
- The AV node is known for its slow conduction to allow for ventricular filling.
*Purkinje fibers > AV node > ventricles > atria*
- This option incorrectly places the **AV node** as the second fastest conductor, and the ventricles as slower than the atria.
- The AV node is specifically designed to slow the impulse to allow for proper ventricular filling.
Bradyarrhythmias and conduction disorders US Medical PG Question 7: A 40-year-old woman comes to the physician for a 6-month history of recurrent episodes of chest pain, racing pulse, dizziness, and difficulty breathing. The episodes last up to several minutes. She also reports urinary urgency and two episodes of loss of consciousness followed by spontaneous recovery. There is no personal or family history of serious illness. She does not smoke or drink alcohol. Vitals signs are within normal limits. Cardiopulmonary examination shows no abnormalities. Holter monitoring is performed. ECG recordings during episodes of tachycardia show a QRS duration of 100 ms, regular RR-interval, and absent P waves. Which of the following is the most likely underlying cause of this patient's condition?
- A. AV node with slow and fast pathway (Correct Answer)
- B. Pre-excitation of the ventricles
- C. Mutations in genes that code for myocyte ion channels
- D. Macroreentrant rhythm in the right atria through cavotricuspid isthmus
- E. Fibrosis of the sinoatrial node and surrounding myocardium
Bradyarrhythmias and conduction disorders Explanation: ***AV node with slow and fast pathway***
- This describes **AV nodal reentrant tachycardia (AVNRT)**, a common cause of **paroxysmal supraventricular tachycardia (PSVT)**. The ECG findings of **narrow QRS (100 ms)**, regular RR-interval, and **absent P waves** (often hidden within the QRS complex) are characteristic of AVNRT.
- The patient's symptoms of recurrent chest pain, racing pulse, dizziness, and spontaneous recovery from loss of consciousness fit the episodic nature of **AVNRT**. The presence of two pathways (slow and fast) within the AV node facilitates the reentrant circuit.
*Pre-excitation of the ventricles*
- **Pre-excitation syndromes** (e.g., Wolff-Parkinson-White syndrome) involve an accessory pathway that bypasses the AV node, leading to a **delta wave** and **short PR interval** on the baseline ECG.
- While they can cause SVT, the ECG during tachycardia would typically show a **wide QRS complex** if the accessory pathway is part of the reentrant circuit (antidromic), or a narrow QRS with a visible P wave if orthodromic and the accessory pathway is used for retrograde conduction, which doesn't fully align with the absent P waves and typically *normal* QRS during tachycardia as described.
*Mutations in genes that code for myocyte ion channels*
- This refers to **channelopathies** (e.g., long QT syndrome, Brugada syndrome), which predispose to **ventricular arrhythmias** like **polymorphic ventricular tachycardia** and **ventricular fibrillation**.
- These conditions typically cause **wide QRS tachycardias** and have distinct ECG patterns (e.g., prolonged QT interval, Brugada pattern) not described here. The narrow QRS and regular rhythm point away from primary ventricular channelopathies as the cause of this specific tachycardia.
*Macroreentrant rhythm in the right atria through cavotricuspid isthmus*
- This describes **atrial flutter**, which typically presents with characteristic **"sawtooth" F waves** on ECG, representing atrial activity.
- While atrial flutter can cause recurrent episodes of rapid heart rate, the ECG description of **absent P waves** and a **narrow QRS complex** without F waves makes atrial flutter less likely.
*Fibrosis of the sinoatrial node and surrounding myocardium*
- **Sinoatrial node dysfunction (sick sinus syndrome)** can lead to bradycardia, sinus pauses, or alternating bradycardia and tachycardia (tachy-brady syndrome).
- It does not primarily cause the described paroxysmal narrow-complex tachycardia with absent P waves. The patient's symptoms are more consistent with an abrupt-onset, regular supraventricular tachycardia.
Bradyarrhythmias and conduction disorders US Medical PG Question 8: A 45-year-old man comes to the physician for a routine health maintenance examination. He feels well. He underwent appendectomy at the age of 25 years. He has a history of hypercholesterolemia that is well controlled with atorvastatin. He is an avid marathon runner and runs 8 miles per day four times a week. His father died of myocardial infarction at the age of 42 years. The patient does not smoke or drink alcohol. His vital signs are within normal limits. Cardiopulmonary examination shows no abnormalities. His abdomen is soft and nontender with a surgical scar in the right lower quadrant. Laboratory studies are within normal limits. An ECG is shown. Which of the following is the most likely diagnosis?
- A. Mobitz type II AV block
- B. First-degree AV block
- C. Mobitz type I AV block (Correct Answer)
- D. Third-degree AV block
- E. Atrial fibrillation
Bradyarrhythmias and conduction disorders Explanation: ***Mobitz type I AV block***
- The ECG shows progressive prolongation of the **PR interval** followed by a dropped QRS complex, which is characteristic of a **Mobitz type I (Wenckebach) AV block**.
- This rhythm disturbance is often benign, especially in athletes with high **vagal tone**, and does not usually require treatment.
*Mobitz type II AV block*
- **Mobitz type II AV block** is characterized by a constant PR interval before the dropped QRS complex.
- This type of block is generally more serious and indicative of a conduction disturbance below the AV node, often requiring a **pacemaker**.
*First-degree AV block*
- A **first-degree AV block** presents with a consistently prolonged PR interval (greater than 0.20 seconds) on every beat, without any dropped beats.
- In this patient's ECG, there is a dropped QRS complex after progressive PR prolongation.
*Third-degree AV block*
- **Third-degree (complete) AV block** is characterized by complete dissociation between the P waves and QRS complexes.
- There is no relationship between atrial and ventricular activity, and the ventricular rate is typically very slow and escape rhythms are observed.
*Atrial fibrillation*
- **Atrial fibrillation** is an irregularly irregular rhythm with no discernible P waves and varying R-R intervals.
- The ECG provided shows clear P waves and a regular, albeit interrupted, rhythm pattern.
Bradyarrhythmias and conduction disorders US Medical PG Question 9: A 23-year-old man comes to the emergency department because of palpitations, dizziness, and substernal chest pain for three hours. The day prior, he was at a friend’s wedding, where he consumed seven glasses of wine. The patient appears diaphoretic. His pulse is 220/min and blood pressure is 120/84 mm Hg. Based on the patient's findings on electrocardiography, the physician diagnoses atrial fibrillation with rapid ventricular response and administers verapamil for rate control. Ten minutes later, the patient is unresponsive and loses consciousness. Despite resuscitative efforts, the patient dies. Histopathologic examination of the heart at autopsy shows an accessory atrioventricular conduction pathway. Electrocardiography prior to the onset of this patient's symptoms would most likely have shown which of the following findings?
- A. Epsilon wave following the QRS complex
- B. Prolongation of the QT interval
- C. Cyclic alteration of the QRS axis
- D. Slurred upstroke of the QRS complex (Correct Answer)
- E. Positive Sokolow-Lyon index
Bradyarrhythmias and conduction disorders Explanation: ***Slurred upstroke of the QRS complex***
- The patient's presentation with **atrial fibrillation with rapid ventricular response** and subsequent collapse after verapamil administration—a calcium channel blocker—is classic for a pre-excitation syndrome like **Wolff-Parkinson-White (WPW) syndrome**.
- In WPW, an accessory pathway (bundle of Kent) bypasses the AV node, leading to a **short PR interval** and a **delta wave** (slurred upstroke of the QRS complex) on ECG during normal sinus rhythm.
*Epsilon wave following the QRS complex*
- An **epsilon wave** is characteristic of **arrhythmogenic right ventricular cardiomyopathy (ARVC)**, representing delayed depolarization of the right ventricle.
- While ARVC can cause arrhythmias, it is distinctly different from the pre-excitation syndrome described, which involves an accessory pathway.
*Prolongation of the QT interval*
- **Prolonged QT interval** is associated with an increased risk of **torsades de pointes**, a polymorphic ventricular tachycardia.
- This finding is typical of **long QT syndrome** and does not directly relate to an accessory atrioventricular conduction pathway.
*Cyclic alteration of the QRS axis*
- **Cyclic alteration of the QRS axis** or electrical alternans is seen in conditions causing swings in cardiac position, most notably **pericardial effusion with tamponade**.
- This ECG finding is unrelated to accessory pathways or the mechanisms of pre-excitation syndromes.
*Positive Sokolow-Lyon index*
- A **positive Sokolow-Lyon index** signifies **left ventricular hypertrophy (LVH)**, characterized by large QRS voltages (e.g., SV1 + RV5/V6 ≥ 35 mm).
- While LVH can be associated with various cardiac conditions, it is not a direct ECG manifestation of an accessory atrioventricular conduction pathway.
Bradyarrhythmias and conduction disorders US Medical PG Question 10: A 21-year-old woman presents with palpitations and anxiety. She had a recent outpatient ECG that was suggestive of supraventricular tachycardia, but her previous physician failed to find any underlying disease. No other significant past medical history. Her vital signs include blood pressure 102/65 mm Hg, pulse 120/min, respiratory rate 17/min, and temperature 36.5℃ (97.7℉). Electrophysiological studies reveal an atrioventricular nodal reentrant tachycardia. The patient refuses an ablation procedure so it is decided to perform synchronized cardioversion with consequent ongoing management with verapamil. Which of the following ECG features should be monitored in this patient during treatment?
- A. Amplitude and direction of the T wave
- B. Length of QRS complex
- C. Length of QT interval
- D. Length of PR interval (Correct Answer)
- E. QRS complex amplitude
Bradyarrhythmias and conduction disorders Explanation: ***Length of PR interval***
- Verapamil is a **non-dihydropyridine calcium channel blocker** that primarily acts on the **AV node** to slow conduction.
- Monitoring the **PR interval** is crucial because excessive slowing of AV nodal conduction can lead to **AV block**, which is indicated by a prolonged PR interval.
*Amplitude and direction of the T wave*
- Changes in T-wave amplitude and direction are often associated with **myocardial ischemia** or **electrolyte imbalances**, which are not the primary concerns with verapamil.
- While verapamil can affect repolarization, the most direct and common adverse effect related to its mechanism of action on the AV node is not primarily reflected in T-wave changes.
*Length of QRS complex*
- The QRS complex duration primarily reflects **ventricular depolarization** and is typically affected by medications that alter conduction through the His-Purkinje system or within the ventricles, such as antiarrhythmics like **flecainide** or **amiodarone**.
- Verapamil's main action is on the AV node, so it generally does not significantly prolong the QRS complex unless there is pre-existing conduction system disease.
*Length of QT interval*
- The QT interval represents **ventricular repolarization**, and its prolongation can lead to **Torsades de Pointes**, a life-threatening arrhythmia.
- While many antiarrhythmics can prolong the QT interval, **verapamil is not known to significantly prolong the QT interval** and is generally considered safe in this regard.
*QRS complex amplitude*
- Changes in QRS amplitude can indicate conditions like **pericardial effusion**, **cardiomyopathy**, or changes in ventricular mass.
- These are generally not direct or common side effects of verapamil therapy, which primarily focuses on AV nodal conduction.
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