4.2 Arrhythmias & Conduction Blocks

ACSM Certified Clinical Exercise Physiologist ACSM-CEP

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1 Introduction & Exam Overview

1.1 The ACSM-CEP Role, Job Definition & Scope of Practice 1.2 Exam Format, Domain Weights & Scoring 1.3 Eligibility, Study Planning & Test-Day Strategy

2 Applied Exercise Physiology & Metabolic Calculations

Bioenergetics & Energy Systems (ATP-PC, glycolytic, oxidative) Acute Cardiorespiratory & Metabolic Responses to Aerobic Exercise Responses to Resistance Exercise & Chronic Training Adaptations ACSM Metabolic Equations, METs & Interpreting VO₂ / RER / Ventilatory Threshold

3 Pathophysiology of Clinical Populations

3.1 Coronary Artery Disease, Myocardial Infarction & Revascularization (PCI/CABG) 3.2 Heart Failure, Valvular Disease & Cardiac Rhythm Disorders 3.3 Hypertension, Dyslipidemia & Peripheral Artery Disease 3.4 Pulmonary Disease: COPD, Asthma & Restrictive/Interstitial Disorders 3.5 Diabetes, Metabolic Syndrome & Obesity 3.6 Renal Disease & Musculoskeletal/Orthopedic Conditions 3.7 Neuromuscular, Neurological & Cognitive Conditions (stroke, MS, Parkinson's, SCI) 3.8 Neoplastic, Immunologic & Hematologic Disorders (cancer, HIV/AIDS, anemia)

4 Clinical ECG Interpretation

4.1 ECG Leads, Waveforms, Rate & Rhythm Determination 4.2 Arrhythmias & Conduction Blocks 4.3 Ischemia, Injury & Infarction (ST changes, exercise-induced) 4.4 Drug & Electrolyte ECG Effects; Resting/Exercise Monitoring Setup & Lead Placement

5 Pharmacology for the Clinical Exercise Physiologist

5.1 Beta-Blockers, Calcium-Channel Blockers & Nitrates 5.2 RAAS Agents, Diuretics, Antiarrhythmics, Lipid-Lowering & Antithrombotic Drugs 5.3 Bronchodilators, Corticosteroids, Insulin & Oral Antidiabetic Agents 5.4 Medication Effects on HR/BP & Exercise Response; Dose/Meal/Dialysis Timing

6 Patient Assessment (Domain I, 18%)

6.1 Medical Records, HIPAA/HITRUST, Charting & Physician Referral 6.2 Patient Interview, Medical History & Medication Reconciliation 6.3 Resting Vital Signs, Body Composition & Resting ECG 6.4 Preparticipation Health Screening & Level of Monitoring (PAR-Q+, ACSM algorithm, ACC/AHA · GOLD · ADA · AACVPR) 6.5 Assessing Patient Goals, Readiness & Psychosocial Status

7 Clinical Exercise Testing (Domain II, 18%)

Submaximal Aerobic Tests (treadmill, cycle, step, 6-minute walk) Musculoskeletal Fitness, Mobility & Balance Testing Maximal Symptom-Limited GXT: Protocols, Contraindications & ECG Prep Test Termination: Relative & Absolute Indications Interpreting & Reporting Results (ECG response, RPP, claudication, Duke Treadmill Score, VO₂/RER/AT)

8 Exercise Prescription for Clinical Populations (Domain III, 22%)

FITT-VP Principles, Progression & Prescription Foundations Ex Rx for Cardiovascular Disease (CAD, HF, HTN, PAD, post-revascularization) Ex Rx for Pulmonary Disease (COPD, asthma; breathing techniques, supplemental O2) Ex Rx for Diabetes, Metabolic Syndrome & Obesity Ex Rx for Musculoskeletal, Neuromuscular, Neoplastic & Other Conditions Communicating Intensity (THR, RPE, talk test), Monitoring & Modifying the Prescription

9 Exercise Training & Leadership (Domain IV, 24%)

9.1 Discussing the Training Plan, Clinician & Patient Expectations/Goals 9.2 Instructing & Modifying Exercise Modes (cardiorespiratory, strength/endurance, flexibility, coordination, agility) 9.3 Patient Monitoring & Supervision During Exercise (telemetry, oximetry, glucometry, ECG) 9.4 Contraindications to Training & Modifying Recommendations 9.5 Documenting Clinical Status, Reporting Adverse Events & Interdisciplinary Coordination

10 Education & Behavior Change (Domain V, 13%)

10.1 Behavioral-Health Screening & Recognizing Distress (PHQ-9, Beck, SF-36; referral) 10.2 Patient Education, Health Literacy & Disease Self-Management 10.3 Motivational Interviewing & Behavior-Change Theories (Transtheoretical, HBM, Social Cognitive, Five-A's) 10.4 Promoting Adherence, Self-Efficacy, Relapse Prevention & Social Support

11 Legal, Professional & Emergency Management (Domain VI, 5%)

11.1 Emergency Equipment, Crash Cart Inspection & Emergency Procedures 11.2 CPR/AED/BLS/ACLS, Universal Precautions & EMS Activation 11.3 Scope of Practice, Legal/Ethical Standards, Liability/Negligence, Informed Consent & Professional Organizations (ACSM/AACVPR/AHA)

4.2 Arrhythmias & Conduction Blocks

Key Takeaways Explain This Topic AI

Atrial fibrillation shows an irregularly irregular rhythm with no discernible P waves, while atrial flutter shows a regular sawtooth pattern of flutter waves

PVCs are premature, wide (over 0.12 sec) bizarre-looking QRS complexes with no preceding P wave, and three or more consecutive PVCs define ventricular tachycardia

Ventricular fibrillation is a chaotic rhythm with no organized QRS complexes and is immediately life-threatening, requiring defibrillation

Mobitz I (Wenckebach) shows progressively lengthening PR intervals until a QRS is dropped; Mobitz II shows a constant PR interval with sudden, unpredicted dropped beats and carries a higher risk of progressing to complete block

Third-degree (complete) AV block shows P waves and QRS complexes firing independently of each other with no consistent relationship

Last updated: July 2026

Arrhythmias & Conduction Blocks

Quick Answer: Arrhythmias are classified by origin (sinus, atrial, or ventricular) and by rate and regularity. Atrial fibrillation is irregularly irregular with no P waves, while ventricular tachycardia is a wide-complex run of three or more PVCs at a rate over 100 bpm. AV blocks are graded first-degree, Mobitz I, Mobitz II, and third-degree (complete) based on how the PR interval and conduction ratio behave, with Mobitz II and complete block carrying the highest clinical risk.

Building on the sinus rhythm criteria from Section 4.1, this section works through the arrhythmias and conduction abnormalities a CEP must recognize during resting and exercise ECG monitoring, since several are indications to stop a test or activate emergency response.

Sinus Node Arrhythmias

Sinus bradycardia: Normal P-QRS-T morphology and conduction, but rate under 60 bpm . Common in trained athletes at rest; concerning if symptomatic (dizziness, syncope) or if it develops abnormally during exercise.

Sinus tachycardia: Normal morphology and conduction, rate over 100 bpm . A normal response to exercise, but at rest can signal anxiety, fever, dehydration, anemia, or cardiac compromise.

Atrial Arrhythmias

Arrhythmia Key ECG Features

Premature atrial contraction (PAC) Early beat with an abnormally shaped P wave (different from sinus P waves), usually followed by a normal, narrow QRS

Atrial fibrillation (AF) No discernible, organized P waves; chaotic fibrillatory baseline; irregularly irregular R-R intervals

Atrial flutter Regular "sawtooth" flutter waves, atrial rate roughly 250-350 bpm, ventricular rate depends on the conduction ratio (commonly 2:1 or 4:1)

Supraventricular tachycardia (SVT) Narrow QRS, regular rhythm, rate typically 150-250 bpm, abrupt onset/offset, P waves often buried in the preceding T wave

New-onset AF or a rapid, uncontrolled ventricular response during exercise testing warrants prompt evaluation and is a relative indication to stop the test.

Ventricular Arrhythmias

Premature ventricular contraction (PVC): An early, wide ( over 0.12 sec ), bizarre-looking QRS with no preceding P wave, usually followed by a compensatory pause. Single, occasional PVCs are common and often benign; frequent, multifocal, paired (couplets), or runs of PVCs are more clinically significant and are relative indications to stop a graded exercise test.

Ventricular tachycardia (VT): Three or more consecutive PVCs in a row, wide QRS, rate typically over 100 bpm . Sustained VT is hemodynamically unstable and is an absolute indication to terminate exercise testing immediately and initiate emergency response.

Ventricular fibrillation (VF): A chaotic, disorganized rhythm with no identifiable P waves, QRS complexes, or T waves. There is no effective cardiac output — VF is a cardiac arrest rhythm requiring immediate defibrillation and CPR per emergency protocol (Chapter 11).

AV (Heart) Blocks

AV blocks describe a delay or interruption in conduction between the atria and ventricles, graded in four tiers:

First-degree AV block: Every P wave conducts to a QRS, but the PR interval is prolonged beyond 0.20 seconds and stays constant. Usually benign and often an incidental finding.

Second-degree, Mobitz Type I (Wenckebach): The PR interval progressively lengthens with each beat until one P wave fails to conduct (a "dropped" QRS), then the cycle repeats. Usually a benign block at the level of the AV node.

Second-degree, Mobitz Type II: The PR interval stays constant , but P waves are intermittently and unpredictably non-conducted (dropped QRS) without any preceding lengthening pattern. This block is typically located below the AV node (infranodal) and carries a higher risk of progressing to complete heart block — it is considered more clinically dangerous than Mobitz I.

Third-degree (complete) AV block: No atrial impulses reach the ventricles. P waves and QRS complexes occur independently of each other (AV dissociation), each at their own regular rate, with no fixed relationship between them. This is a medical emergency requiring prompt evaluation and often pacing.

Clinical Significance During Exercise Testing

New-onset Mobitz Type II block, third-degree AV block, or a new bundle branch block that cannot be confidently distinguished from ventricular tachycardia appearing during a graded exercise test are all relative indications to terminate the test. Because Mobitz II and complete heart block can progress abruptly to a slow ventricular escape rhythm or asystole, any patient found to have these blocks at rest should be evaluated and cleared by the supervising physician before undergoing exercise testing.

Bundle Branch Blocks

A bundle branch block delays depolarization through the right or left ventricle, widening the QRS to 0.12 seconds or greater :

Right bundle branch block (RBBB): Classic "rabbit ears" (rSR' pattern) in V1, with a wide, slurred S wave in lead I and V6.

Left bundle branch block (LBBB): Broad, monophasic R wave in leads I and V6, with absent Q waves in those leads. LBBB also distorts the ST segment and T wave in a way that obscures the ability to diagnose ischemia from standard ST-segment criteria, which is an important limitation to recognize before exercise testing a patient with known LBBB.