MED213 Clinical Insights: Understanding Electrophysiology

Flashcards for vocabulary terms.

Pre-Participation Screening

Part of risk assessment and risk management based on the ACSM, screens for signs/symptoms of disease, known CV, metabolic or renal disease etc.

ACSM Screening Process

Identifies those at risk for serious acute exercise-related CV events including sudden cardiac death and myocardial infarction

Medical Clearance

Needed if the participant has known disease, signs, or symptoms suggestive of disease before participating in regular exercise. If cleared, light to moderate exercise is recommended.

Supervision Levels

Low risk - Unsupervised, Medium risk – a HCP with experience of clinical exercise testing, High Risk - a HCP with experience of clinical exercise testing BUT a trained doctor is immediately available if required o ILS-trained (at least) for administration of drugs in case of a CV event

Exercise Contraindications

Conditions where exercise should not be started: Unstable angina, Unstable heart failure, Unstable diabetes, New/uncontrolled arrhythmias, Resting tachycardia, Symptomatic hypotension etc.

Exercise Termination Criteria

Reasons to stop an exercise test: Target HR achieved, Chronotropic incompetence, Hypertensive responses, Drop in SBP, Fatigue, ECG changes (arrhythmias, ST depression), Angina, Request to stop, Equipment failure

ECG Waves

Represent depolarisation and repolarisation of the heart.

P Wave

Represents atrial depolarisation.

QRS Complex

Represents ventricular depolarisation.

T Wave

Represents ventricular repolarisation.

PR Interval

Represents the time from the beginning of atrial depolarisation to the beginning of ventricular depolarisation.

QRS Duration

Should be <0.12 s

Corrected QT duration for men

≤ 0,45 s

Corrected QT duration for women

≤ 0,47 s

Cardiac Action Potentials - Phase 0

Rapid influx of Na

Cardiac Action Potentials - Phase 1

K+ influx

Cardiac Action Potentials - Phase 2

Influx of Ca2+ balanced by K+ efflux (plateau)

Cardiac Action Potentials - Phase 3

Ca2+ channels close K + channels stay open

Cardiac Action Potentials - Phase 4

Na & Ca2+ close K+ open

Coronary Arteries

Supply blood and oxygen to the myocardial cells (cardiomyocytes).

Right Coronary Artery (RCA)

Supplies the RA, RV, SAN and AVN, and posterior LV.

Left Coronary Artery (LCA)

Splits into LAD and CA, which supplies LA and LV.

Coronary blood flow

250 ml min −1 (0.8 ml min−1 g−1 of heart muscle) = 5% of resting Q

Myocardial Ischemia

A condition in which the heart muscle doesn't receive enough blood, resulting in lack of oxygen.

Anterior STEMI (V2-V5)

Is likely to be occluded in LAD artery

Sinus Tachycardia

An elevated resting heart rate, typically above 100 bpm.

Sinus Bradycardia

A slow resting heart rate, typically below 60 bpm.

Sinus Arrhythmia

Irregular heart rhythm that is often normal.

PVC

Premature Ventricular Contractions - premature beat arising from an ectopic focus within the ventricles.

Multifocal PVC’s

originate from multiple sites

Bigeminy or Trigeminy

PVC every other beat or every third beat

Ventricular Tachycardia (VT)

More than 3 PVC’s = Ventricular Tachycardia (non-sustained)

Atrial Fibrillation (AF)

“irregularly irregular” ventricular rhythm – rapid and chaotic depolarisation within atria à erratic transmission of impulses at AV node

Wolf-Parkinson-White Syndrome

Very short PR intervals (0.08s) + 2nd A-V connection in addition to normal conduction via AV node

Delta Wave

Sooner depolarisation shown in Wolf-Parkinson-White Syndrome

Right Bundle Branch Block (RBBB)

Delayed electrical activation of RV as must be depolarised by the LBB

Left Bundle Branch Block (LBBB)

RV depolarises normally and first via RBB + Delayed electrical activation of LV as must be depolarised by the RBB with septal depolarisation from R to L

LVH = S wave depth V1 + tallest R wave height in V5-V6

35 mm

ST depression

most common and useful indication of myocardial ischemia (≥1mm)

ST Elevation

most common and useful indication of myocardial infarction (STEMI)

Congenital/genetic pathology which can cause sudden cardiac death

Hypertrophic cardiomyopathy, Arrhythmogenic ventricular cardiomyopathy, Dilated cardiomyopathy

Coronary artery disease/anomalies which can cause sudden cardiac death

Congenital coronary artery anomalies, Premature atheromatous coronary artery disease

Cardiac conduction tissue abnormalities which can cause sudden cardiac death

Wolff-Parkinson-White syndrome, Right ventricular outflow tachycardia

Ion channelopathies which can cause sudden cardiac death

Congenital long QT syndrome, Catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome

Acquired causes which can cause sudden cardiac death

Infections (myocarditis), Drugs (cocaine, amphetamine), Electrolyte disturbances (hypokalemia or hyperkalemia), Hypothermia, Hyperthermia, Trauma (commotio cordis

Normal ECG Findings in Athletes

Increased QRS voltage for LVH or RVH, Incomplete RBBB, Early repolarization/ST segment elevation etc.

Borderline ECG Findings in Athletes

Left axis deviation, Left atrial enlargement, Right axis deviation, Right atrial enlargement, Complete RBBB

Abnormal ECG Findings in Athletes

T wave inversion, ST segment depression, Pathologic Q waves, Complete LBBB, QRS ≥ 140 ms duration, Epsilon wave etc.

Unifocal PVC’s -

RV outflow

What is the RR interval?

Distance between R-waves

What is the PP interval?

Distance between P-waves