Flashcards in Cardiology Deck (26):
Describe the Cardiac Cycle
Diastole (Relaxation of the Heart) is the first phase. This is when ventricular filling begins.
Systole is the 2nd phase first with the Atria contracting which causes the blood in the atria to finish filling the ventricles (atrial kick). The ventricles then contract pushing blood through the pulmonary and aortic valves.
What is the Ejection Fraction?
The ratio of the amount of blood pumped out of the ventricles in a contraction. Typically about 2/3rds the total volume.
What is stroke volume?
The amount of blood ejected. Normally it is between 60-100ml's. Avg. is 70ml
What does stroke volume depend on?
Preload, Cardiac Contractility and Afterload.
The pressure in the filled ventricle at the end of diastole. It is also called End-Diastolic Volume.
It influences the force and amount of the next contraction.
Starling's law of the Heart states what?
The more the myocardial muscle is stretched the greater its force of contraction will be.
Therefore, the greater the venous return, the greater the preload (filling/stretching of the muscle) and the greater the stroke volume.
What landmark denotes the 2nd rib and superior border of the middle mediastinum?
The Sternal Angle
Explain the pericardium and its layers.
It is a sac that surrounds the heart. The Fibrous pericardium attaches to the sternum and surrounding structures and protects the heart. It is VERY strong and is why then the pericardial cavity gets fluid in it a Cardiac Tamponade can result.
The Serous layer of the pericardium has a Visceral layer and a Parietal layer. The Visceral layer is the same layer as the epicardium and lies on the hearts outer surface. The Parietal later is the layer ontop of the Visceral Pericardium.
The pericardium contains a pericardial cavity which a lipid based solution resides that allows the heart to beat without friction.
Explain the complete flow of blood through the heart.
Blood enters the R. Atrium from the Superior and Inferior Vena Cava as well as the Coronary Sinus. Blood passes through the Tricuspid or Right Atrioventricular valve to the R. Ventricle where it is pumped through the Pulmonary Valve to the Pulmonary Trunk then to the Right and Left lung via the Pulmonary Arteries. The blood flows back to the Left Atrium from the Right and Left Pulmonary Veins. The blood flows through the Mitral or Left Atrioventricular Valve to the Left Ventricle where it is pumped through the Aortic Valve to the Ascending Aorta.
Where do the coronary arteries originate? When do they fill?
They originate in the Aorta just after the Aortic Valve. They fill during Diastole.
Which nerve controls Parasympathetic Responses in the heart?
The Vagus (10th) Cranial nerve.
Trace the normal cardiac conduction system pathways.
SA Node, Internodal Pathways to AV Node, AV Node to the AV Bundle (of His) to the Left and Right Bundle Branches.
What are the Inherent Rates for the SA Node, AV Junction and the Purkinje Fibers in the Ventricles?
SA Node 60-100 bpm
AV Junction 40-60 bpm
Ventricle 20-40 bpm
What is the "Primary Pacemaker" for the heart? What is it's rate and how much of it is actual pacemaker cells?
50% Actual Pacemaker Cells
Where does the electrical Impluse travel after the SA Node?
Through the Internodal Pathways to the AV Node and AV Junction.
What is Bachmann's Bundle? Why is it important?
Also known as Wenckebach’s bundle and Thorel’s pathway.
A group of interatrial fibers contained in the left atrium
Subdivision of anterior internodal tract.
Conducts electrical activity from the SA node to the left atrium.
Describe the AV Node. Why is it important?
Located on floor of right atrium above tricuspid valve.
Electrical activity delayed 0.05 seconds, this pause allows for more complete filling of ventricles.
Only pathway of atrial electrical impulses to ventricles.
Where is the "Secondary Pacemaker" Located?
Describe the Bundle of His
Conduction pathway that leads out of AV node.
Receives blood from left anterior and posterior descending coronary arteries.
Lies at top of interventricular septum.
Referred to as the common bundle.
Ability to self-initiate electrical activity at intrinsic firing rate of 40-60 bpm.
Connection between upper and lower chambers of the heart.
Divides into two main bundle branches
What comes after the Bundle of His?
Right bundle branch, Left bundle branch
Conducts electrical activity from bundle of His to Purkinje’s network
Describe the Purkinje's Network
Fibers that spread throughout the ventricles
Carries impulses directly to ventricular muscle cells
Intrinsic firing rate of 20-40 bpm
Describe the "P Wave"
Is the first wave produced by electrical impulse from SA Node.
Smooth, rounded upward deflection.
Represents Atrial Depolarization
0.10 seconds in length.
Describe the PR Interval
PRI” represents the time the impulse takes to travel from SA Node through the Internodal pathways in the atria towards the ventricles.
The measuring starts from the beginning of the “P” wave to the start of the QRS
Length is 0.12-0.20 seconds
Describe the QRS Complex
Consists of the Q, R, and S waves.
Represents the Ventricular Depolarization and Atrial Repolarization
Measures less than 0.12 seconds or 3 small boxes
"Q" Wave is the first downward deflection
"R” wave is the first upward deflection.
Largest deflection seen in Leads I and II
“S” wave is the first downward deflection after the “R” wave.
Describe the "T" Wave. Why is it important?
Follows ST Segment
Represents Ventricular Repolarization
Slightly rounded, positive deflection.
Resting phase of cardiac cycle. (Most vulnerable phase of the cycle)