Transcript Document

Abnormalities of the Conduction System
Elizabeth Dugan - [email protected]
Olamide Odubogun - [email protected]
Rhythm Of The Heart
The Heart is Like an Orchestra.
It has a conducting system that is
directed by a conductor.
This conductor is the “Natural
Pacemaker” of the Heart
Conducting System:
-SA node (Primary Pacemaker)
-AV node
-Bundle of His
-Purkinje Fibers
Conducting System
•Sino-Atrial node (SA Node)
-Origination and dissemination of
electrical signals to BOTH atria
-Causes BOTH atria to contract
•Atrioventricular Node (AV Node)
-Transmits signal to ventricles by going
through interventricular septum
-Causes intentional delay, to allow atria
to complete pumping
•His Purkinje System
-Electrical signal flows through the
His-Purkinje system and causes the
ventricles to contract SIMULTANEOUSLY
Electrical Signal
SA node fires  electrical
AV Node fires  electrical signal
signal spreads through the
spreads through His-Purkinje
Right and left atria  Right and
System  Right & Left Ventricles
Left atria contract (blood moves from
atria to ventricles)
Contract (blood moves from
ventricles into aorta and pulmonary
a.)
The Electrocardiogram
(EKG or ECG)
EKG Mechanics
WHAT does an EKG measure?
•Measures electrical signals from heart.
This consists of:
•Atrial contraction - P Wave
•Ventricular contraction – QRS complex
•Ventricular Relaxation – T Wave
HOLD ON!!!!!
What about Atrial Relaxation?
HOW does it do this?
Your body is a conductor of electricity
•The electrical signal generated in the heart is
detected by the leads placed on the surface
of the body
Main EKG Waves
Atria contract
P Wave
Ventricles contract
QRS complex
Ventricles Relax
T Wave
Normal EKG
P
QRS
T
P
QRS
T
P
T
QRS
P
T
P
QRS
Normal EKG:
1. Regular Rate –heart rate of 60-100 bpm
2. Regular Rhythm – P – QRS – T – P – QRS – T – P – QRS – T - etc
3. The height of the wave – related to the mass of the muscle generating the wave
- the ventricles have more mass than the atria: P wave is smaller than QRS complex
- large ventricles (ventricular hypertrophy)  more muscle creating a stronger
signal when the ventricles contract:
taller QRS complex
Ventricular Hypertrophy (Large Ventricle)
NOTICE the very large
QRS complex in the EKG
Causes of a Large QRS Complex
Increased mass in:
1. One ventricle
2. Both ventricles
3. Portion of the ventricle
QRS
Normal EKG
ARRHYTHMIA
Ventricular Fibrillation
1. Ventricular Fibrillation – disordered electrical activity
The ventricles "flutter" rather than beat and pump little or no blood.
2. In minutes, collapse and sudden cardiac death will follow
 Medical help is needed immediately
3. Treatment - defibrillator
Hypertrophic Cardiomyopathy
-Disease of the myocardium
-Portion of the myocardium is thickened
(hypertrophied, aka, the opposite of
atrophy)
-Individual muscle fibers are disorganized
 abnormal conduction + arrhythmias
Hypertrophy is asymmetric
The interventricular septum (muscle b/w
the 2 ventricles) is usually enlarged much
more than the rest of the ventricle
The ventricle is hypertrophied
What happens to the following:
Relaxation?
ALL
Filling?
ARE
Pressure?
DECREASED!
Forward Flow?
What does all this cause?
Difficulty breathing!
Outflow Obstruction
Outflow tract
obstruction – (the
outflow tract is the path
from the LV into the
aorta)
Increased
velocity!
Normal Flow
Normal Velocity, Low Pressure
Outflow Obstruction
Fast Velocity, High Pressure
When flow is obstructed, you need to build more muscle so that you can
pump harder! This equals hypertrophy!
Mitral Regurgitation
- Narrowed outflow tract =
faster flow
- Faster flow of blood pulls
the mitral valve open
- Blood goes back into the
atria from the ventricle
during systole mitral
regurgitation
SHOW VIDEO
HOW WE FIX MITRAL REGURG?
Aortic
Valve
Regurgitation
Mitral
Valve
Left
Ventricle
HCM Symptoms
• Average age presentation : mid 20s
• Wide range symptoms/severity
• Difficulty breathing (dyspnea)
–WHY?
• Angina
–WHAT DOES ANGINA MEAN?
• Syncope (fainting)
–FROM WHAT?
–WHY WOULD FAINTING BE BENEFICIAL?
Interesting Facts
– What is the most common cause of cardiac death in
athletes?
• Hypertrophic Cardiomyopathy
– How many people does this affect?
• 1/500
– Is everyone at risk for this?
• Inherited (genetic) disorder: autosomal dominant,
know your genetics and be careful if you are a possible
carrier!
– Does everyone with HCM have the same symptoms and
outlook?
• There are different forms of the disease and some are
more severe than others  incomplete penetrance
Physical Exam
• Often are normal
• Extra heart sounds
– Fourth heart sound – this is heard before the “Lub” 
instead of “lub-dub” you here “da-lub-dub”
• Systolic Murmur
– Due to Turbulent (noisy) flow through the outflow tract (LV to Aorta)
• Systolic Murmur
– Due to regurgitation of blood through the mitral valve
HCM and Arrhythmias
Normal Myocardium :
Linear arrangement
HCM:
Disarray!
Physiology 101: Structure = Function
Thus, Abnormal Structure=…
MYOCARDIAL DISARRAY
During Vfib
-The ventricles are like
bowl of jelly
- Inefficient pump
-Muscle cells malaligned
“Myocardial Disarray”
HHOW DO YOU SOLVE
THIS PROBLEM??
1) Defribillators
e.g. ICD
2) Pacemakers
(artificial)
Implantable Cardioverter Defibrillator (ICD)
An ICD is used in patients at risk for:
1. Ventricular tachycardia (>100 bpm)
2. Ventricular fibrillation
3. Sudden cardiac death caused by
arrhythmias
An ICD is made up of two parts:
1. Pulse generator – battery plus circuits
2. One or two leads (wires)
How the ICD Works:
1. Leads monitor your heart rate
2. ventricular tachycardia or fibrillation
detected  controlled burst of impulses
(called "overdrive" pacing)
3. If that does not work, the ICD "shocks"
the heart to restore a normal rhythm.
Newer ICD devices can also work like a
pacemaker if a slow heart rate
(bradycardia) occurs.
What does it Look Like???
Pacemaker
Pacemakers are used to treat:
1. Abnormal rates
Bradycardia/ Tachycardia
2. Abnormal rhythms
Arrhythmia
Atrial fibrillation
Goals:
1. Coordinate the electrical signaling between
the upper and lower chambers of the heart
2. Coordinate the electrical signaling between
the ventricles
An ICD is like a pacemaker in some ways, but it
can use higher energy electrical pulses to treat
certain dangerous types of arrhythmia.
The End