Download Cardiac anatomy and physiology

CARDIAC A&P
ATRIUMS
VENTRICLES
ATRIOVENTRICULAR VALVES
SEMILUNAR VALVES
SEPTUM
PERFUSION
• RIGHT HEART
• PUMPS BLOOD THROUGH THE
PULMONARY CIRCULATION
TO THE LEFT HEART
• LEFT HEART
• PUMPS BLOOD THROUGH THE
SYSTEMIC CIRCULATION BACK
TO THE RIGHT HEART
CORONARY
CIRCULATION
• CORONARY ARTERIES
• SUPPLY BLOOD TO HEART
MUSCLE
• R&L CORONARY ARTERIES
• ARISE FROM AORTA
• HEART EXCLUSIVELY RECEIVES
•
BLOOD FROM R&L CORONARY
ARTERIES
LACK OF COLLATERAL
CIRCULATION
OXYGEN REQUIREMENTS OF THE HEART
• EVEN AT REST
•
•
THE MYOCARDIUM EXTRACTS ABOUT 70% OF THE OXYGEN FROM ITS ARTERIAL BLOOD FLOW
IN COMPARISON, THE REST OF THE BODY ONLY EXTRACTS 25% OXYGEN FROM ITS ARTERIAL
BLOOD FLOW
• DURING EXERCISE
•
•
THE EXTRACTION RATE IS EVEN HIGHER
SINCE THE HEART MUSCLE CANNOT EXTRACT MUCH ADDITIONAL OXYGEN FROM THE BLOOD
(30%), THE ONLY WAY IT CAN RECEIVE MORE OXYGEN IS THROUGH INCREASED CORONARY
BLOOD FLOW (I.E. INCREASED HEART RATE)
ECG TRACING LEAD II
• BIPOLAR LIMB LEADS: EINTHOVEN’S
TRIANGLE
• LEAD I (-) ON RIGHT ARM AND (+) ON
LEFT ARM
• LEAD II (-) ON RIGHT ARM AND (+)
ON LEFT LEG
• LEAD III (-) ON LEFT ARM AND (+) ON
LEFT LEG
• LEAD AXIS IS STRAIGHT LINE DRAWN
BETWEEN + AND 1 ELECTRODES
CARDIAC
CONDUCTION
SA NODE
Internodal bundles
AV Node
Bundle of HIS
R & L Bundle Branches
Purkinje Fibers
PACEMAKERS
WHO LEADS AND WHO FOLLOWS?
Sinoatrial
Node
AV Nodal
His
Firing Threshold
Bundle
Of His
Time
EKG
COMPONENTS
P Wave – Atrial depolarization
Duration not over 0.11 sec
Increased height/width
indicate enlarged atria
Q Wave –Ventricular septum
depolarization
May not be present in some
leads.
R Wave – Main ventricular
depolarization
S Wave – Late ventricular
depolarization
T wave – Ventricular
repolarization
SYSTEMATIC APPROACH TO INTERPRETATION
APPROACH 1
STANDARDIZED APPROACH TO EACH STRIP
•RATE (ORIGINATION)
•RHYTHM (R-R INTERVAL)
•P-WAVE (CONDUCTION RATIO)
•PR INTERVAL (< 0.12)
•QRS COMPLEX (NARROW/WIDE)
GREAT APPROACH WHEN REVIEWING PREVIOUSLY ACQUIRED DATA
Normal Sinus
Rhythm
Rate: 60-100 b/m
Sinus Bradycardia
Sinus Tachycardia
Rate: 4P & 4QRS
4 X 10 = 40 b/m
Rate: 12P & 12QRS
12 X 10 = 120 b/m
Rhythm: Consistent Rhythm: Consistent Rhythm: Consistent
R-R Interval
R-R Interval
R-R Interval
P-Wave: Upright &
Rounded (SA
initiates each beat)
P-Wave: Upright &
Rounded (SA
initiates each beat)
P-Wave: Upright &
Rounded (SA
initiates each beat)
Conduction Ratio
1:1
Conduction Ratio
1:1
Conduction Ratio
1:1
PR Interval:
<0.2sec
PR Interval:
<0.2sec
PR Interval:
<0.2sec
QRS: Narrow
QRS: Narrow
QRS: Narrow
Types of Tachycardia
Sinus Tachycardia
Supraventricular
Tachycardia (SVT)
Rate: 12P & 12QRS
12 X 10 = 120 b/m
Rate: ?P & 17QRS
17 X 10 = 170 b/m
ventricular
Rhythm: Consistent R-R
Interval
Rhythm: Consistent R-R
Interval
P-Wave: Upright & Rounded
(SA initiates each beat)
P-Wave: Can’t see any
Conduction Ratio 1:1
Conduction Ratio: ??
PR Interval: <0.2sec
PR Interval: not
measureable
QRS: Narrow
QRS: Narrow
Origin – above ventricles
IN THIS RHYTHM STRIP:
• SA NODE FIRES AT THE CORRECT
TIME FOR THE FIRST 3 BEATS
• IRRITABLE FOCUS IN THE ATRIUM
WORKS UP ENOUGH ENERGY TO FIRE
ON ITS OWN IN BEAT 4
• WHAT DO YOU THINK OF THE SHAPE
OF THE P WAVE IN BEAT 4?
DIFFERENT?
• WHAT ABOUT THE QRS? – SAME – THE
REST OF THE CONDUCTION PATHWAY
IS INTACT, AND WILL TRANSMIT THE
ENERGY ACCORDINGLY
VENTRICULAR FILLING
BEFORE WE MOVE ON….
• APPROX. 80% OF VENTRICULAR FILLING IS PASSIVE
• REMAINING 20% IS CAUSED BY ATRIAL KICK
• AFTER ATRIAL CONTRACTIONS (ATRIAL KICK) THE VENTRICLES ARE FULLY DISTENDED
WITH BLOOD
• THIS IS CALLED PRELOAD
KEY QUESTIONS: IS 80% A “GOOD” OR “DECENT” AMOUNT OF PRELOAD?
ATRIAL FLUTTER
MORE THAN ONE SITE IN ATRIUM TRYING TO DOMINATE
CONDUCTION PATHWAY
•
•
•
•
•
RATE: 5 QRS X 10 = 50, 10P X 10 = 100 (1:2 CONDUCTION
RATIO)
RHYTHM: REGULAR R-R INTERVAL
P WAVES – NOT EVERY P HAS A QRS –
UPRIGHT/ROUNDED
PR- <0.2 FOR CONDUCTIVE BEATS
QRS – NARROW
ATRIAL
FIBRILLATION
DIFFERENCE BETWEEN A-FLUTTER & A-FIB?
•
•
•
MANY SITES COMPETING – AND NONE ARE STRONG ENOUGH TO
CONSISTENTLY DRIVE THE CONDUCTION SYSTEM
WHAT DOES THIS CAUSE – QRS BECOME MUCH LESS REGULAR IN
RHYTHM
NO ATRIAL KICK – ATRIUMS ARE NOT CONTRACTING – ONLY PASSIVE
FILLING OF VENTRICLES
JUNCTIONAL
ABNORMALITIES
P-WAVE MORPHOLOGIES
•
•
•
NO P-WAVE = SIMULTANEOUS
DEPOLARIZATION OF ATRIA AND
VENTRICLES
INVERTED = ATRIA DEPOLARIZE BEFORE
VENTRICLES
INVERTED AFTER QRS = VENTRICLES
DEPOLARIZED BEFORE ATRIA
INVERTED REPRESENTS RETROGRADE
TRANSMISSION OF ENERGY
1st degree:
• ONLY problem:
LONG PR Interval
• No dropped QRS
FIRST DEGREE
AV BLOCK
ELECTRICAL ENERGY DOES NOT PROGRESS
NORMALLY FROM SA NODE THROUGH
THE AV NODE TO THE VENTRICLES
SOMETHING HAPPENS TO DELAY OR
“BLOCK” THE TRANSFER OF ENERGY
ALONG THE NORMAL CONDUCTION
PATHWAY
Main Findings: Dropped QRS
Dropped QRS = Decreased
Cardiac Output
SECOND DEGREE
AV BLOCKS
TYPE 1, MOBITZ 1, WENCKEBACH
• PR INTERVAL GRADUALLY INCREASES
UNTIL A QRS IS DROPPED
TYPE 2, MOBITZ 2, NON-WENCKEBACH
• DROPPED QRS, PR CAN BE
PROLONGED
Main Findings: WIDE QRS
No relationship between P’s and QRS
Candidate for pacemaker
THIRD DEGREE
AV BLOCK
•
•
•
•
•
•
RATE – REMEMBER THERE ARE TWO RATES
V = 3 X 10 = 30; A = 8 X 10 = 80
RHYTHM – INDEPENDENTLY EACH WAVE IS
REGULAR
P WAVES – UPRIGHT & ROUNDED, NO
RELATIONSHIP BETWEEN P & QRS (HOW DO
WE KNOW THIS…. WIDE QRS)
PR – NO PATTERN
QRS – WIDE
VENTRICULAR ABNORMALITIES (PVC)
Terms for PVC’s
Unifocal PVCs
Originate from same location, same morphology
Multifocal PVCs
Different origins, different morphology
Bigeminy
PVC in every other beat
Trigeminy
PVC in every third beat
Couplet
Two PVC’s in a row
Ventricular
Tachycardia
Three or more PVCs in a row
V-TACH
Main Findings: Decreased Cardiac Output
Extremely fast rate
V.Tach can be tolerated by some pts if
enough blood is pumped per beat
VENTRICULAR FIBRILLATION
Main Findings: NO
Cardiac Output
What is missing? QRS!
QRS = ventricular defibrillation, which =
perfusion
IMMEDIATELY LIFE-THREATENING
CLEAR
SYSTEMATIC APPROACH TO INTERP
APPROACH 2
• VENTRICULAR FIRST!
•
•
•
•
TIPS FOR EKG ANALYSIS
“BOTTOMS UP”
EASIEST TO SEE (LARGEST EKG COMPONENT)
CAN QUICKLY DIFFERENTIATE VENTRICULAR
FROM SUPRAVENTRICULAR RHYTHMS.
SIGNIFY THE MORE “LIFE-THREATENING”
RHYTHMS.
ATRIAL LAST
•
•
HARDER TO SEE, COMMONLY “MASKED” WITH
ARTIFACT.
LESS HEMODYNAMIC CONSEQUENCES TO
ATRIAL ARRHYTHMIAS.
GREAT APPROACH WHEN ASSESSING LIVE DATA
MYSTERY RHYTHM WITH ARTIFACT
What do we know?
1.
2.
3.
“Bottoms up”
Narrow QRS
• Rapid ventricular depolarization (i.e perfusion)
• Impulse source supraventricular in origin
Rhythm – Yes ( Consistent R-R intervals)
Rate 80-90
• Sinus – Probable
• Atrial – Less likely
• Junctional- Highly unlikely
MYSTERY RHYTHM WITH ARTIFACT
Normal sinus rhythm
MYSTERY EKG 2
What do we know? “Bottoms up”
Narrow or wide QRS?
1. Narrow QRS
•
Rapid ventricular depolarization
• Impulse source supraventricular in origin
Rhythm?
No – inconsistent R-R intervals
Between 90-100
Rate?
MYSTERY EKG 2
A-Fib