Chapter Summary:
In this section, we learned all about the cardiovascular system. The anatomy of the heart was reviewed. This section also covered the electrical conductivity of the heart, heart sounds, arrhythmia of the heart, the process by which blood pressure is controlled regulation of blood flow and hypertension. This section covered a lot of material and explained very well not only the anatomy of the heart but also why it works the way it does. The cardiovascular system does an amazing job at regulating itself.

Heart Murmurs:
Heart murmurs are heard during auscultation of the heart sounds. A murmur is an abnormal heart sound that is present because of blood flow patterns in the heart that are abnormal. Abnormal blood flow can occur for many different reasons. It can be caused by a valve that doesn't open or close properly, and it can also be caused by blood back flowing through valves as well. The septum that separates the right and left ventricles can sometimes have holes in it. These holes allow blood flow where it would not normally be and also produce a heart murmur. My son has a heart murmur. His is caused by a condition called aortic bicuspid valve. His aortic valve doesn't open all the way because two of the valve leaflets are fused together and this reduces his blood flow.
Below is an example of a heart murmur that is a result of aortic stenosis. It starts with three normal heart sounds then adds the murmur.

Arrhythmias occur for many reasons. They can be a result of decreased blood flow in the coronary arteries, a block in electrical impulses or heart failure. Bradycardia is a heartbeat that is slower than 60 beats per minute and tachycardia is a heartbeat that is faster than 100 beats per minute. Some people have normal resting heartrates that are either brady or tachy. This can be a life-threatening problem if the heart beats too fast or too slow. If the heart beats too slow, it does not perfuse enough blood for the body. If the heart beats too fast, it can go into a condition called ventricular tachycardia which is lethal.

Ventricular Tachycardia

A common arrhythmia that I see frequently in my job is called atrial fibrillation. In any fibrillation rhythm, the contraction of the atria and ventricles occurs at different times and they are not coordinated, which makes coordinated pumping of the heart impossible. In atrial fibrillation, the electrical impulses that control the contraction of the atria are disorganized and the pumping of the atria is ineffective. The atria will contract without any type of coordination with the ventricles.

Atrial Fibrillation

There are many many many many more arrhythmias that I could cover, but for the sake of time and space, I will just stick to these. Ventricular tachycardia and ventricular fibrillation are both lethal and if the heart is not shocked out of these rhythms, the person will die. Aortic fibrillation is very common and is relatively benign. Many patients that I encounter are in a constant state of A-fib.

Congestive Heart Failure:
Congestive heart failure is a problem that seems to be on the rise. Congestive heart failure occurs because of increase venous volume and pressure from that increased venous volume. Failure of the ventricles of either side raises the pressure on the atria which causes edema and congestion. If the failure is on the left side, the edema and congestion occurs in the lungs. If the pulmonary edema is severe enough, it can be fatal. Pulmonary edema can cause shortness of breath and fatigue. These are classic signs of congestive heart failure. If the right ventricle is the failing one, it will cause edema and congestion to build up in the circulation system of the body as a whole. The elevated blood volume of the body causes a chronically low cardiac output when congestive heart failure is occurring. During congestive heart failure, the body reduces urine output despite the fact that ANP is being secreted at an increased rate. ANP is responsible for stimulating urine and water excretion. Often people with congestive heart failure have edema in their legs and feet and are treated with diuretics to try and lower their blood volume.

Application to Nursing:
Cardiology applies to nursing in so many ways it is hard to narrow down just one application. For me and my job that I would like to have in the near future, cardiology and the understanding of it will be my entire job. I plan on working in the Critical Care/Telemetry Unit at Prairie Lakes Hospital when I am done with nursing school. In this unit, we take care of not only critically ill patients, but we also take care of patients that have had an angiogram done, a pacemaker inserted, recent bypass surgery, etc. We take care of a multitude of cardiac patients. Having a vast knowledge of cardiology and the functions of the cardiovascular system is critical to work in my department. This not only applies to my future, but also applies to my current job as a telemetry technician. My job is to watch cardiac monitors and alert nursing staff of any changes in a patient's heart rhythm. Often times, serious problems can be detected by changes in a cardiac rhythm. IN order to do my job properly and understand what to watch for when I am watching patients on the monitors, I must understand the anatomy and functionality of the heart. When I measure out cardiac rhythms, certain distances between points on the rhythm strips can indicate various heart problems. For example, a P-R interval that measure greater that .200 is an indicator of a first degree AV block. This means that there is a block in the electrical current of the AV node of the heart. That type of information is vital for me to do my job properly. The nurses often depend on my interpretation of a cardiac rhythm and often need things explained to them as far as what is going on with the patient's heart. This is where knowledge of cardiology is crucial.

Essential Question:

"What are the three most important variables that affect blood pressure? Describe each variable and how it affects blood pressure. Describe two reflexes that help maintain blood pressure within normal limits."

There are three main variables that are essential for blood pressure changes. They are cardiac rate, stroke volume and total peripheral resistance. Cardiac rate the amount of times your heart beats each minute. When the heart rate increases, the blood pressure also increases. When the heart rate decreases, so does the blood pressure. In a heart that is pumping fast, the blood is traveling through the vascular system so rapidly that the vessels do not have time to depressurize. Because of this, the pressure in the arteries is maintained and they are under an almost constant state of pressure which is why the blood pressure rises when the heart rate increases. When the heart rate decreases, the heart is pumping less often and the arteries are allowed time to depressurize between beats. This drops the blood pressure because the heart is not pumping as often or with as much force. The arteries are not under a constant state of pressure.
Stroke volume is the next variable that is essential for blood pressure changes. Stroke volume is a measure of the amount of blood that is pumped by the heart with each beat. The greater the stroke volume is, the greater the blood pressure will be. When the stroke volume increases, more blood is being pumped through the heart with each beat. This increase in blood means a greater pressure that is being exerted on the walls of the arteries. As the pressure being exerted on the walls of the arteries increases, the blood pressure will increase.
Peripheral resistance is the last of the variables that affect blood pressure. Peripheral resistance is the resistance that the arteries have to blood flow. I equate this to trying to drive a car through packed snow. The packed snow exerts a resistance on the tires of the car and more force from the car is needed to drive through the snow. The same idea is true for our arteries. The more resistance to blood flow that the arteries present, the harder the heart has to pump to move the blood through the arteries and the higher the blood pressure will be.
Two reflexes that help the blood pressure stay within normal limits are the baroreceptor reflex and the atrial stretch reflex. The baroreceptors lie in the aortic arch and the carotid sinus. When the baroreceptors detect changes in the blood pressure, they activate the the parasympathetic or sympathetic nerve systems depending on if they detect a rise or fall in blood pressure. When a fall in blood pressure is detected, the sympathetic nerve system is activated and the cardiac output will increase as well as peripheral resistance. These increases will then raise the blood pressure. When a rise in blood pressure is detected, the parasympathetic nerve system is activated and a reduction in both cardiac output and peripheral resistance is activated which lowers the blood pressure.
The aortic stretch receptors are located in the atria of the heart. These receptors detect an increased venous return to the heart. When an increased volume to the heart is detected, these receptors inhibit the release of the anti-diuretic hormone which will increase urine output and lower the blood volume which will lower the blood pressure. The aortic stretch receptors also stimulate the release of atrial natriuretic peptide. The ANP increases the release of urinary salt and water. This release also decreases the blood volume and thus decreases the blood pressure.

I thought this video was very entertaining and did a good job of explaining a heart block called Wenckebach...Enjoy!

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