Cardiomyopathy

It is a disease of the heart muscle. The heart is a series of 2 pumps separated by the lungs. The right side of the heart is to bring blood from the body and send it to the lungs. Once in the lungs, the blood is oxygenated and then travels to the left side of the heart and then to the body. Both sides of the heart pump blood simultaneously. The heart is essentially a big muscle and when the heart relaxes, the chambers of the heart expand. As it dilates the oxygenated blood is drawn into the right side and deoxygenated blood is drawn into the left chamber simultaneously. When the heart contracts it expells this blood either to the lungs or the body. The heart muscle can fail in 3 ways.

Power failure - The chambers of the heart dilate a lot which stretches the muscle of the heart wall thinly making it ineffective and less powerful when pumping, resulting in less blood leaving the heart and heart failure. This is dilated cardiomyopathy.  Small - The walls of the heart become very thick in some cases, they often become scarred and stiff. This prevents the heart from expanding and pulling enough blood in to the push out. This is restrictive cardiomyopathy. Blockage - There is assymetric thickening of the heart wall muscle. The septum becomes very hypertrophied and blocks bloodflow out from the aorta. It also creates the same environment as small pump. This is hypertrophic cardiomyopathy. 

This is how a cardiomyopathy is created. 

Cardiomyopathy is a disease of heart muscle. The right chambers of the heart are responsible for drawing in blood from the body and sending it to the lungs to become oxygenated. The right chambers of the heart are responsible for drawing the oxygenated blood from the lungs and sending it to the rest of the body to provide oxygen and nutrients while removing waste and returning deoxygenated to the right chambers of the heart to begin again. If a cardiomyopathy is present the heart cannot effectively do this. There is a decreased outflow of blood to the lungs from the right chambers. This causes shortness of breath and increased respiratory rate. There is also a build up of blood in the body that isnt being pumped into the lungs well (oedema). If the left chambers of the heart are having decreased outflow the symptoms occur in the body. The blood coming from the left chambers also supplies the heart itself. This causes an increase in heart rate as the heart isnt getting enough blood. This causes pain as well known as angina. The rest of the muscles in the body will become weakened and fatigued. It also supplies the brain which can cause fainting and dizziness. There is also a build up of blood in the lungs as it is not getting efficiently moved through the left side of the heart (pulmonary oedema).

Dilated Cardiomyopathy - increased jugular venous pressure due to thinning of the muscle wall as the heart is dilated. The blood from the right heart thats getting backed up in the veins of the neck causing them to appear distended. It also has an S3 heart sound as the blood is entering an already partially full chamber. Increased heart size (cardiomegaly). Restrictive Cardiomyopathy - heart muscle is very stiff and scarred down. JVP increased again. S4 heart sound is caused by blood entering into a stiff chamber that can be heard. Hypertrophic cardiomyopathy - walls are really big and not as stretchy. the septum is very assymetrically enlarged and blocks the outflow of blood from the left ventricle. S4 heart sound also and heart murmur (systolic ejection murmur) that increases with the Valsalva maneuver (bearing down to make the left ventricle chamber smaller intensifying the murmur). The murmur is caused by turbulent bloodflow during ejection. 

Dilated cardiomyopathy is caused by a dysfunction in the heart muscles ability to contract. This a systolic failure. The heart muscle is very thin and the walls of the ventricles are not able to contract as well as it should. The heart can contract but it is not able to expell all of the blood from the ventricles. If there is blood left in the ventricles, then there is less blood going to the lungs or the rest of the body. This is a decreased ejection fraction. The chambers of the heart dilate in response to this decreased ejection fraction. Dilatation of the ventricles increases the total volume that the heart ejects with each contraction and the blood getting to the lungs and body remains enough. This dilation gets worse and eventually the atria are also dilated to help cope with the build up of blood that hasnt gotten through yet. Eventually the chambers cant dilate enough. This is when the symptoms of heart failure become apparent. These are due to a decreased ability to pump the bloodflow forwards which will cause chest pain, syncope or due to the blood building up behind the heart causing oedema of the legs and abdomen.

This can be genetic due to proteins in the muscle cells that dont allow them to contract very well. It can be due to inflammation of the heart from a vural infection for example (myocarditis). It can be due to toxins that affect the heart such as alcohol or pregnancy. It can also be idiopathic. It cannot be caused by ischaemic heart disease, valvular heart disease or hypertension which can also cause heart failure.  

History - the signs and symptoms are very general and are not specific to dilated cardiomyopathy. They are similar to heart failure - chest pain, syncope and fatique and oedema. 

Blood work - Brain natriuretic peptide (BNP) becomes elevated in conditions that cause the heart to expand but is not very specific.

EKG - it is almost always abnormal but the results are non-specific.

Chest Xray - cardiomegaly (enlarged heart).

Best test is an echocardiogram as it shows the dilation of the chambers and the decreased ejection fraction.

Angiograms are not routinely used and neither are biopsies. 

pump failure - B blockers - decrease oxygen demand of the heart which can decrease symptoms if the heart is overworked. Digoxin isnt used frequently but can be used to increase contraction strength. Pacemaker to regulate the beating of the heart if the disease is severe. Heart transplant

backup of blood - low salt diet. sodium regulates the fluid in the body. A low salt diet causes the body to get rid of backup of fluid caused by cardiomyopathies. If diet is not sufficient, diuretics can be added to the treatment. ACE inhibitors  are also used. 

decreased outflow - ACE inhibitors - dilate arterioles and decreases the resistance in the arteriole system that the heart has to pump against for the same contraction strength you can get an increased outflow from the heart. 

The key cell in the RAAS system are juxtaglomerular (JG) cells in the blood vessels of the kidney. They are specialist smooth muscle cells. The release the hormone renin when BP needs raised. If the JG notice BP is low or a sympathetic nerve cell when triggered in fight or flight, or the macula densa cells in the distal convoluted tubule can sense sodium and if there isnt a lot of sodium they send prostaglandins to the JG cells to release renin and increase blood pressure. 

The liver cells make angiotensinogen (sleep-walker) in its inactive form and meets renin which cleaves part of angiotensinogen to make angiotensin-1. Angiotensin-1 is active and in the blood vessels lined with endothelial cells convert angiotensin-1 to angiotensin-2 is very active. Angiotensin-2 works in 4 cell types. 1. smooth muscle cells are going to contract and increase resistance in blood vessels etc. 2. kidney cells retain water, increasing stroke volume. 3. pituitary gland secretes hormones (ADH antidiuretic hormone) which increase vascular resistance and water retention in kidneys. 4. the adrenal gland makes the hormone aldosterone acting on kidney cells to increase water retention.

Increasing the stroke volume in the kidneys by retaining water and by constricting the vascular system and increasing the vascular resistance, blood pressure will rise. 

If the RAAS system is chronically activated there is a permanent retention of water and permanent constriction of the blood vessels which will result in vascular resistance and increased pressure within the circulatory system. This means the heart will have to work harder to pump blood around the body. It  increases the CO and blood pressure. If this is not treated it will become chronic hypertension. 

Heart disease can develop as the the patient now has chronic hypertension if it is left untreated. Heart disease is a leading cause in dilated cardiomyopathy development. The ventricles of the heart become stretched and enlarged to increase the amount of blood they can hold and pump out to deal with the increase in fluid and pressure. This causes the walls of the ventricle to thin and the muscle cannot contract with enough power to fully empty the chambers. This leads to heart failure.