EKG, Sensitivity & Specificity, BP Wrap Up

Electrocardiogram

- A graph of the hearts electrical impulses and patterns as measured by electrodes

- versatile, immediate

Electrocardiograms are NOT __________ and NOT _____________

- NOT invasive

- NOT expensive

Electrocardiograms detect normal (or abnormal) rhythms of the heart and....(4)

• Arrhythmias

• Myocardial ischemia/infarction

• Drug toxicities

• Other cardiac abnormalities

• Electrical impulse starts at the ___________________ node of the ______ atrium

• Then a wave of _________________ occurs across the atria to the ___________________ node

• Conduction goes down the left and right ________________, and into the ____________________ system where it transmits to the ___________________

• The electrical stimulation of heart muscle cells cause __________ to enter into the cell, more calcium is released causing a __________________

• After the contraction, myocytes ________________ and get ready for the next impulse

• Electrical impulse starts at the sinoatrial (SA) node of the right atrium

• Then a wave of depolarization occurs across the atria to the atrioventricular (AV) node

• Conduction goes down the left and right bundle branches, and into the His-Purkinje system where it transmits to the ventricular myocardium

• The electrical stimulation of heart muscle cells cause calcium to enter into the cell, more calcium is released causing a contraction

• After the contraction, myocytes repolarize and get ready for the next impulse

Depolarize- _____________

Repolarize- __________

Depolarize- contract

Repolarize- relax

P wave

• Upper heart chambers

• Represents atrial depolarization or contraction of atria

PR interval

• End of the P wave to the start of the QRS complex

• Reflects how conduction is slowed through the AV node and the time delay between atrial and ventricular depolarization

QRS Complex

• Lower heart chambers

• Ventricular depolarization (or ventricular systole (contraction))

• Q wave: first downstroke

• R Wave: first upward spike

• S Wave: downward dip

T Waves

ventricle repolarizes at the beginning of ventricular diastole (relaxation)

What do boxes on the EKG strip mean?

Boxes measure time and distance

A large "big" box (5 mm) mean) =

= 0.20 seconds

A small box (1 mm)=

= 0.04 seconds

Dips and spikes are called ____________ identifying different phases of the activity of the ___________

- waves

- heart

EKG has _____ "leads" with _____ electrodes. _____ on chest, _____ at limbs

- 12 "leads"

- 10 electrodes

- 6 on chest

- 4 at limbs

QT Prolongation (or long QT syndrome)

Abnormal heart electrical system where it takes the heart longer to recharge between beats

What can QT Prolongation lead to?

a potentially life-threatening arrhythmia called torsades de pointes (pronounced torsad de pwant)

Medications may cause QT prolongation

• Antiarrhythmic: Amiodarone

• Antibiotic: Eryrthromycin, Ciprofloxacin

• Antipsychotic: Amitryptyline, citalopram

• Antihistamine: Diphenhydramine

Comparing PQRST!

Sensitivity & Specificity

If a person screened positive and is a person with the disease, it is a...

TRUE positive (TP)

If a person screened positive and is disease free, it is a...

FALSE positive (FP)

If a person screened negative and is a person with the disease, it is a....

FALSE negative (FN)

If a person screened negative and is disease free, it is a...

TRUE negative (TN)

Sensitivity focuses on...

- people who really have a disease

- True positive (+) fraction

- probability that a person who really has a certain disease screens positive (+)

- (a /a +c) X100

Specificity focuses on...

- people who do NOT have disease

- True negative fraction

- probability that a disease-free person screens negative

- (d /b + d) X 100

Positive Predictive Value (PPV)

- focuses on people who test positive

- probability that subjects with a positive screening test truly have the disease or condition

- true positive/(true positive + false positive)

- (a /a + b)X 100

Negative Predictive Value

- focuses on people who test negative

- probability that subjects with a negative screening test truly don't have the disease

- true negative/ (true negative + false negative)

- (d/d + C) X100

Sensitivity and PPV chart

Specificity and NPV chart

Sensitivity vs. PPV

Sensitivity: how many REAL cases did we catch? People who HAVE the condition, accuracy of identifying sick ppl

PPV: If it's positive, how likely is it to be true? People who TESTED POSITIVE, chance that a positive test actually means disease

Specificity vs. NPV

Specificity: How well does the test avoid false positives? People who DON'T HAVE the condition, accuracy of identifying healthy ppl

NPV: If it's negative, how likely is it correct? People who TESTED NEGATIVE, chance that a negative test actually means no disease

Auscultatory Gap & Blood Pressures: Korotkoff sounds become...

inaudible

Auscultatory Gap & Blood Pressures can lead to...

falsely LOW blood pressure

Auscultatory Gap & Blood Pressure is the reason we use what?

using palpable systolic with radial artery