Dental MCQ
Rhythm reading · Cardio & Respiratory · INBDE Patient Cases

ECG Basics INBDE Patient Cases

By Dr. Isaac Sun, DDS

8 ADA INBDE-format patient cases on ecg basics. Each case is a shared patient box (chief complaint, history, medications, allergies, exam) followed by linked multiple-choice questions with full distractor explanations. Practice the way the real exam is structured.

8 patient cases40 linked questionsADA INBDE formatFull distractor explanations

Eight ADA INBDE-format patient cases on ECG and rhythm reading in the dental setting: a pacemaker patient and electromagnetic interference from electrosurgery, symptomatic bradycardia from high-grade AV block, ventricular fibrillation arrest managed with an AED and CPR, supraventricular tachycardia with a vagal maneuver, QT prolongation and the macrolide antibiotic interaction (torsades de pointes), newly discovered atrial fibrillation and stroke risk, an implantable cardioverter-defibrillator with inappropriate-shock risk, and anxiety-driven sinus tachycardia. Topics include the P-QRS-T waves, the PR and QT intervals, the SA and AV nodes and His-Purkinje conduction, shockable versus non-shockable arrest rhythms, defibrillation versus cardioversion, and chair-side rhythm recognition.

Case Coverage Map
What each case is testing
Patient with a pacemaker before a cleaning:
Pacemaker indications, electromagnetic interference from electrosurgery, precautions, anticoagulation.
Near-fainting with a very slow pulse:
Symptomatic bradycardia, high-grade AV block, low cardiac output, urgent referral, pacemaker.
Collapse and cardiac arrest in the office:
Ventricular fibrillation, AED, shockable vs non-shockable rhythms, CPR and defibrillation, EMS.
Sudden racing, regular heartbeat:
Supraventricular tachycardia, regular vs irregularly irregular, vagal maneuver, holding epinephrine.
Choosing an antibiotic with a QT-prolonging drug:
QT prolongation and torsades, macrolide interaction, amoxicillin choice, medication reconciliation.
Irregular pulse discovered at a cleaning:
Newly found atrial fibrillation, stroke risk, referral, treating safely while arranging follow-up.
Patient with an implanted defibrillator before surgery:
ICD function, interference and inappropriate shocks, electrosurgery avoidance, anticoagulation.
Pounding heart and nerves during an extraction:
Sinus tachycardia, sympathetic beta-1 drive, benign vs dangerous rhythm, pain and anxiety control.
Patient case: Patient with a pacemaker before a cleaning
0 of 5 answered, 0 correct
Patient
Male, 78 years old
Chief Complaint
"I have a pacemaker, is your equipment safe for me?" he asks.
Background and/or Patient History
  • Presented for scaling and a crown preparation
  • Permanent pacemaker placed two years ago for complete heart block
  • Feels well, no dizziness or palpitations
  • Carries a pacemaker identification card
Allergies
NKDA
Medications
  • Apixaban
  • Metoprolol
Current Findings
  • Regular pulse at 70 bpm
  • BP 134/80
  • No syncope or shortness of breath
  • No acute distress
  1. Question 1
    Easy
    His pacemaker was most likely placed to treat:
  2. Question 2
    Moderate
    The main concern with some dental equipment is:
  3. Question 3
    Moderate
    Which instrument is the most likely source of electromagnetic interference?
  4. Question 4
    Moderate
    A reasonable precaution is to:
  5. Question 5
    Hard
    His apixaban means that for the extraction you should:

Reset this case?

This clears your answers for this patient case only.

Patient case: Near-fainting with a very slow pulse
0 of 5 answered, 0 correct
Patient
Female, 72 years old
Chief Complaint
"I keep feeling like I might pass out," she says during the exam.
Background and/or Patient History
  • Presented for a denture adjustment
  • Several near-fainting episodes over the past week
  • Feels her heartbeat is very slow
  • No chest pain
Allergies
NKDA
Medications
  • None reported
Current Findings
  • Regular pulse at 38 bpm
  • BP 96/60
  • Lightheaded when sitting up
  • Alert and oriented
  1. Question 1
    Easy
    Her pulse of 38 bpm is best described as:
  2. Question 2
    Moderate
    Near-syncope with a very slow rate suggests the heart is not maintaining adequate:
  3. Question 3
    Moderate
    A common cause of a dangerously slow rate is:
  4. Question 4
    Moderate
    The most appropriate action is to:
  5. Question 5
    Easy
    Definitive treatment for symptomatic high-grade AV block is often:

Reset this case?

This clears your answers for this patient case only.

Patient case: Cardiac arrest in the dental chair
0 of 5 answered, 0 correct
Patient
Male, 64 years old
Chief Complaint
"My chest is really tight," he said during the extraction, then slumped in the chair.
Background and/or Patient History
  • Presented for a surgical extraction
  • Reported chest pressure mid-procedure, then became unresponsive in the chair
  • Not breathing normally; no pulse detected
  • History of coronary artery disease
Allergies
Unknown
Medications
  • Aspirin
  • Atorvastatin
Current Findings
  • Unresponsive, no pulse
  • Automated external defibrillator (AED) attached
  • AED analysis: ventricular fibrillation
  • Office emergency team activated
  1. Question 1
    Easy
    The AED rhythm, ventricular fibrillation, is:
  2. Question 2
    Easy
    The immediate priority is to:
  3. Question 3
    Moderate
    In ventricular fibrillation, the ventricles:
  4. Question 4
    Moderate
    Which rhythm would NOT be treated with a defibrillation shock?
  5. Question 5
    Easy
    While the team works, the dentist should also:

Reset this case?

This clears your answers for this patient case only.

Patient case: Sudden racing, regular heartbeat
0 of 5 answered, 0 correct
Patient
Female, 29 years old
Chief Complaint
"My heart just started racing out of nowhere," she says.
Background and/or Patient History
  • Presented for a routine filling
  • Sudden onset of a rapid, regular pounding heartbeat
  • Mildly short of breath and anxious
  • Has had brief similar episodes before
Allergies
NKDA
Medications
  • None
Current Findings
  • Rapid regular pulse around 180 bpm
  • BP 118/74
  • Alert, no chest pain
  • No facial swelling or wheeze
  1. Question 1
    Moderate
    A sudden regular narrow-complex rate near 180 bpm most likely represents:
  2. Question 2
    Moderate
    Unlike atrial fibrillation, her rhythm is:
  3. Question 3
    Moderate
    A reasonable first step in this stable patient is to:
  4. Question 4
    Moderate
    You should activate EMS if she develops:
  5. Question 5
    Hard
    Regarding local anesthetic during this episode, the best choice is to:

Reset this case?

This clears your answers for this patient case only.

Patient case: Choosing an antibiotic with a QT-prolonging medication
0 of 5 answered, 0 correct
Patient
Female, 58 years old
Chief Complaint
"I have a dental infection and need an antibiotic," she says.
Background and/or Patient History
  • Presented with a localized odontogenic infection
  • Takes a medication known to prolong the QT interval
  • You are considering an oral antibiotic
  • No drug allergies reported
Allergies
NKDA
Medications
  • Citalopram (a QT-prolonging antidepressant)
Current Findings
  • Localized swelling near tooth #19
  • Pulse 78, BP 126/80
  • Afebrile, no airway compromise
  • Otherwise well
  1. Question 1
    Moderate
    A prolonged QT interval increases the risk of:
  2. Question 2
    Hard
    Which commonly prescribed dental antibiotic class can further prolong the QT?
  3. Question 3
    Moderate
    The safest antibiotic choice here is generally:
  4. Question 4
    Moderate
    QT prolongation reflects delayed ventricular:
  5. Question 5
    Easy
    Before prescribing, the best practice is to:

Reset this case?

This clears your answers for this patient case only.

Patient case: Irregular pulse discovered at a cleaning
0 of 5 answered, 0 correct
Patient
Male, 68 years old
Chief Complaint
"I didn't know my pulse was irregular," he says when you mention it.
Background and/or Patient History
  • Presented for a routine cleaning
  • No known heart rhythm problem
  • Occasional palpitations he had ignored
  • No chest pain or fainting
Allergies
NKDA
Medications
  • Amlodipine for blood pressure
Current Findings
  • Irregularly irregular pulse
  • Rate about 96 bpm
  • BP 138/86
  • No acute distress
  1. Question 1
    Easy
    An irregularly irregular pulse with no pattern suggests:
  2. Question 2
    Moderate
    The main danger of undiagnosed atrial fibrillation is:
  3. Question 3
    Moderate
    The most appropriate step is to:
  4. Question 4
    Moderate
    In atrial fibrillation, the atria:
  5. Question 5
    Moderate
    A routine cleaning today is:

Reset this case?

This clears your answers for this patient case only.

Patient case: Patient with an implanted defibrillator before surgery
0 of 5 answered, 0 correct
Patient
Male, 66 years old
Chief Complaint
"I have a defibrillator implanted," he notes in his history.
Background and/or Patient History
  • Presented for a surgical extraction
  • Has an implantable cardioverter-defibrillator (ICD) for a prior ventricular arrhythmia
  • Stable, no recent shocks
  • Asks whether surgery is safe
Allergies
NKDA
Medications
  • Metoprolol
  • Apixaban
Current Findings
  • Regular pulse at 64 bpm
  • BP 128/78
  • ICD identification card present
  • No distress
  1. Question 1
    Easy
    An ICD is designed to:
  2. Question 2
    Moderate
    Electromagnetic interference from electrosurgery could:
  3. Question 3
    Moderate
    A reasonable precaution is to:
  4. Question 4
    Moderate
    His apixaban affects the extraction mainly by:
  5. Question 5
    Hard
    Compared with a pacemaker, an ICD adds the concern of:

Reset this case?

This clears your answers for this patient case only.

Patient case: Pounding heart and nerves during an extraction
0 of 5 answered, 0 correct
Patient
Male, 41 years old
Chief Complaint
"My heart is pounding and I'm really nervous," he says during the extraction.
Background and/or Patient History
  • Presented for extraction of a painful molar
  • Very anxious, poor sleep and several coffees this morning
  • Received local anesthetic with epinephrine
  • No history of heart rhythm problems
Allergies
NKDA
Medications
  • None
Current Findings
  • Regular pulse at 108 bpm
  • BP 138/84
  • Alert and visibly anxious
  • No wheeze or swelling
  1. Question 1
    Easy
    A regular rate of 108 bpm here is:
  2. Question 2
    Moderate
    The most likely contributors are:
  3. Question 3
    Moderate
    These factors raise heart rate mainly through:
  4. Question 4
    Moderate
    The best initial approach is to:
  5. Question 5
    Moderate
    Compared with a dangerous arrhythmia, sinus tachycardia from anxiety is:

Reset this case?

This clears your answers for this patient case only.

Keep studying
ECG Basics core recall

Refresh the anatomy facts these cases depend on: nerve numbers, foramina, functions, and lesion findings.

← Back to ECG Basics