Palpitations: MCCQE1 Preparation Guide

Introduction

Palpitations are defined as an unpleasant awareness of the forceful, rapid, or irregular beating of the heart. It is a common presenting complaint in Canadian primary care and emergency departments. For the MCCQE1, candidates must demonstrate a structured approach to differentiate between cardiac (arrhythmic/structural), psychiatric, and metabolic etiologies.

Etiology and Differential Diagnosis

The differential diagnosis for palpitations is broad. A useful framework for MCCQE1 preparation is to categorize by system.

Clinical Evaluation

History Taking

A detailed history is the most important tool for diagnosis. Use the OPQRST mnemonic tailored for palpitations.

• Onset: Sudden (SVT) vs. Gradual (Sinus Tach).
• Provocation/Palliation: Exercise (Ischemia/HOCM), Position changes (Orthostatic), Post-prandial (Vagal).
• Quality: “Flip-flopping” (PVCs/PACs), “Fluttering” (AF), “Pounding in neck” (Cannon A waves in AVNRT).
• Radiation: Not applicable, but ask about chest pain radiation.
• Severity: Impact on daily life.
• Timing: Duration and frequency.

Red Flags (Must Rule Out)

Physical Examination

Perform a focused exam looking for signs of structural heart disease or systemic causes.

• Vitals: Pulse (rate, rhythm), BP (check for orthostasis), O2 saturation.
• Neck: JVP (elevated in HF), Cannon A waves (AV dissociation), Thyroid enlargement/bruit.
• Cardiac:
  • Displaced PMI (Cardiomyopathy).
  • Murmurs (HOCM: systolic crescendo-decrescendo increases with Valsalva; MVP: mid-systolic click).
• Respiratory: Crackles (Heart Failure).
• Extremities: Edema, tremor (Hyperthyroidism), track marks (Drug use).

Diagnostic Approach

For the MCCQE1, knowing the correct order of investigations is crucial. Follow this algorithm:

Canadian Guidelines & Management

Atrial Fibrillation (CCS Guidelines)

The Canadian Cardiovascular Society (CCS) guidelines are high-yield for the MCCQE1.

• “CCS Algorithm” for AF:
  1. Assess Thromboembolic Risk: Use CHADS-65 (Canadian modification of CHADS2-Vasc).
     • Age ≥ 65 OR History of Stroke/TIA OR Hypertension, Diabetes, or HF?
     • If Yes -> Oral Anticoagulation (DOACs preferred over Warfarin unless mechanical valve/severe mitral stenosis).
  2. Symptom Management: Rate control (Beta-blockers, CCBs) vs. Rhythm control (Cardioversion, Anti-arrhythmics, Ablation).

Driving Restrictions (CMA Driver’s Guide)

In Canada, physicians have a duty to report medical conditions that affect driving.

• Syncope + Palpitations: Private driving is generally suspended until the cause is identified and treated.
• Ventricular Tachycardia: Strict restrictions apply depending on underlying cause and treatment efficacy.

Key Points to Remember for MCCQE1

• Most common cause: In primary care, the most common causes are psychiatric (anxiety) or benign ectopy (PVCs/PACs), but cardiac causes must be ruled out.
• Vagal maneuvers: Valsalva or carotid massage can terminate SVT (AVNRT).
• Adenosine: The first-line drug for stable narrow-complex tachycardia (SVT) unresponsive to vagal maneuvers.
• Unstable patient: If a patient with palpitations is hypotensive, has chest pain, or altered mental status -> Synchronized Cardioversion.
• Thyroid: Always check TSH in new-onset Atrial Fibrillation.

Common Abbreviations

AF    : Atrial Fibrillation
SVT   : Supraventricular Tachycardia
WPW   : Wolff-Parkinson-White Syndrome
HOCM  : Hypertrophic Obstructive Cardiomyopathy
PVC   : Premature Ventricular Contraction
CCS   : Canadian Cardiovascular Society
CHADS : Congestive HF, Hypertension, Age, Diabetes, Stroke

Sample Question

Clinical Scenario

A 55-year-old female presents to the emergency department with a 2-hour history of rapid heart palpitations, shortness of breath, and lightheadedness. She has no significant past medical history. Vitals:

• Heart Rate: 160 bpm (regular)
• Blood Pressure: 85/50 mmHg
• Respiratory Rate: 24/min
• O2 Saturation: 92% on room air

Physical examination reveals cool extremities and bibasilar crackles. An ECG monitor shows a regular, narrow-complex tachycardia. Vagal maneuvers have been attempted without success.

Which one of the following is the most appropriate immediate management step?

Options

• A. Intravenous adenosine 6 mg push
• B. Intravenous metoprolol 5 mg push
• C. Synchronized electrical cardioversion
• D. Intravenous amiodarone infusion
• E. Defibrillation (unsynchronized)

Explanation

The correct answer is:

• C. Synchronized electrical cardioversion

Detailed Analysis

This question tests the management of unstable tachyarrhythmias, a critical concept for the MCCQE1 and ACLS protocols.

1. Identify Stability: The patient is unstable. Signs of instability include:

   • Hypotension (BP 85/50)
   • Signs of shock (cool extremities)
   • Signs of heart failure (bibasilar crackles, hypoxia)
   • Altered mental status (lightheadedness is a precursor, though not fully altered yet, the hypotension dictates action).

2. Rhythm Identification: The patient has a regular, narrow-complex tachycardia (likely SVT or Atrial Flutter).

3. Management Decision:

   • Stable SVT: Vagal maneuvers -> Adenosine -> Beta-blockers/CCBs.
   • Unstable Tachycardia (with a pulse): Synchronized Cardioversion.
   • Pulseless VT/VF: Defibrillation (Unsynchronized).

• Why C is correct: According to ACLS guidelines, unstable patients with a pulse and tachyarrhythmia require immediate synchronized cardioversion.
• Why A is incorrect: Adenosine is the treatment of choice for stable SVT. While it can be considered while preparing for cardioversion, it should not delay cardioversion in a hypotensive patient with signs of shock/failure.
• Why B is incorrect: Beta-blockers (metoprolol) can further lower blood pressure and worsen heart failure in an unstable patient.
• Why D is incorrect: Amiodarone is used for rhythm control but is slower acting and not the immediate treatment for instability.
• Why E is incorrect: Unsynchronized cardioversion (defibrillation) is used for cardiac arrest (VF or pulseless VT). Using it on a patient with a pulse and an organized rhythm can induce VF (R-on-T phenomenon).

References

1. Canadian Cardiovascular Society (CCS). (2020). CCS Guidelines for the Management of Atrial Fibrillation. Retrieved from ccs.ca 
2. Medical Council of Canada. (n.d.). Objectives for the Qualifying Examination Part I: Palpitations.
3. Canadian Medical Association. (2019). CMA Driver’s Guide: Determining Medical Fitness to Operate Motor Vehicles. 9th Edition.
4. UpToDate. (2023). Evaluation of palpitations in adults.
5. Toronto Notes. (2023). Cardiology: Approach to Arrhythmias.