1. Which phase of the cardiac cycle does this picture show
Which phase of the cardiac cycle does this picture show? How can you be sure?

2. Think about it…
What do you suspect happens to the coronary blood vessels as the heart goes through the cardiac cycle?
What would happen to them during systole?
What would happen to them during diastole?

3. Coronary Blood Vessels
Feed the cardiac muscle with oxygen rich blood
The coronary vessels branch off of the base of the aorta
Only fill with blood when the pressure inside of the aorta is low and the blood flows back towards the heart

4. What happens to a heart if it can’t get enough oxygen?
HEART ATTACK

5. Why?

7. Intrinsic Conduction System of the Heart

8. Heart Beat Control… Why Necessary?
Cardiac muscle cells contract spontaneously  do not require a stimulus from the nervous system to contract
Atrial cells contract 60x/min.
Ventricular cells contract 20-40x/min.
heart needs a control system to coordinate pumping  heart would be inefficient w/o it

9. Heart Regulation 2 systems regulate heart activity:
Autonomic nervous system: increases and decreases heart rate
Discussed in nervous system
*Intrinsic conduction system (AKA nodal system):
Special heart tissue  cross between muscle & nervous tissue
Sets rhythm for heart
Causes controlled contraction (depolarization) from atria to ventricles

10. How Does Heart Contract?
Sinoatrial (SA) node in the right atrium sends an electrical signal to the atria
*causes atria to contract together
SA node = pacemaker

11. How Does Heart Contract?
2. After the signal to contract travels through the atria it goes to the atrioventricular (AV) node
(Allows mini pause in signal so atria can finish contracting)

12. How Does Heart Contract?
3. AV node releases signal to atrioventricular (AV) bundle aka bundle of His
Right & left bundle branches
Purkinje fibers

13. How Does Heart Contract?
4. As electrical signal spreads through the Purkinje fibers contraction begins in apex and travels toward the atria
Pushes blood into the aorta and to body

14. Conduction System Video
Aligns electrical system with an EKG
General animation of electrical conduction system

15. Practice
Using your index cards and NO notes, show how the electrical impulse is carried through the heart starting with the “pacemaker”.
When you have finished and have been checked, use a piece of chalk to draw where atrial and ventricular contraction occur.

16. EKG/ ECG
Electrocardiogram is a way to measure the electrical activity in the heart
Shows
How fast your heart is beating
Whether the rhythm of your heartbeat is steady or irregular
The strength and timing of electrical signals as they pass through each part of your heart

17. Reading EKG’s
P wave = SA node firing = happens immediately before atria contract
QRS complex = AV node firing = happens immediately before ventricles contract
T wave = ventricles preparing for another impulse

18. Sample 1. Identify the P, Q, R, S, and T waves.
2. Look to the left of each QRS and identify the P wave. Is the P wave present (+) or absent (-): ______
3. Is there a 1:1 ratio of P waves to QRS waves? ____________ …so is this regular or not? __________
4. What is the rate of the heart? ______________
5. Diagnosis/Conclusions: __________________________________________________________

19. The heart’s rate is more rapid than normal (over 100 beats/min)
Tachycardia
The heart’s rate is more rapid than normal (over 100 beats/min)
vi. Other lethal and nonlethal arrhythmias may follow AMI.
(a) Premature ventricular contractions (PVCs), or extra beats in the ventricle, are lethal if they occur in the damaged ventricle but harmless if they occur in the nondamaged ventricle.
(b) Tachycardia is rapid beating of the heart, 100 beats/min or more.
(c) Bradycardia is unusually slow beating of the heart, 60 beats/min or less.
(d) Ventricular tachycardia (VT) is rapid heart rhythm, usually 150 to 200 beats/min.

20. Bradycardia
vi. Other lethal and nonlethal arrhythmias may follow AMI.
(a) Premature ventricular contractions (PVCs), or extra beats in the ventricle, are lethal if they occur in the damaged ventricle but harmless if they occur in the nondamaged ventricle.
(b) Tachycardia is rapid beating of the heart, 100 beats/min or more.
(c) Bradycardia is unusually slow beating of the heart, 60 beats/min or less.
(d) Ventricular tachycardia (VT) is rapid heart rhythm, usually 150 to 200 beats/min.
The heart rate is significantly lower than normal (less than 60 beats/min)

21. Atrial Fibrillation Atria contract more often than the ventricles
One of these things is not like the other!
Atria contract more often than the ventricles

22. Sinus Arrest Sleepin’ on the job
SA node fails to fire and the heart doesn’t beat.
Sleepin’ on the job

23. Fibrillation The heart is not beating in a coordinated manner
vi. Other lethal and nonlethal arrhythmias may follow AMI.
(a) Premature ventricular contractions (PVCs), or extra beats in the ventricle, are lethal if they occur in the damaged ventricle but harmless if they occur in the nondamaged ventricle.
(b) Tachycardia is rapid beating of the heart, 100 beats/min or more.
(c) Bradycardia is unusually slow beating of the heart, 60 beats/min or less.
(d) Ventricular tachycardia (VT) is rapid heart rhythm, usually 150 to 200 beats/min.
The heart is not beating in a coordinated manner
Muscle cells are contracting but are not in synch  inefficient pumping of blood
Can lead to cardiac arrest

24. Asystole There is no electrical activity in heart (no contraction)
Cannot be revived!
5. Other considerations in using AEDs
a. Not all patients in cardiac arrest require electrical shock.
b. All patients in cardiac arrest should be analyzed with an AED; some do not have shockable rhythms.
c. Asystole (flatline) indicates that no electrical activity remains.
d. Pulseless electrical activity usually refers to a state of cardiac arrest despite an organized electrical complex.

25. More Practice
Add the P, Q, R, and S cards to the index cards to show which actions of the electrical system create the types waves seen on an EKG
Try to do this without your notes!