Pathology - Cardiac Unit

major chamber of the heart

right artria, left artia, right ventricle, left ventricle

major vessels of the heart

aorta, pulmonary arteries, pulmonary veins, superior vena cava, inferior vena cava

location of heart

resides in mediastinum, between the lungs, slightly left of the midline

ischemic heart disease

leading cause of death in the US, caused by atherosclerotic coronary artery disease (CAD), reduced myocardial blood perfusion

CAD

Coronary Artery Disease, heart disease

warning signs of ischemic heart disease

chest pain (angina), shortness of breath (SOB), sweating (disphoresis)

unstable stable angina

caused by dislodged (breaks off) atherosclerotic plaque (fat deposit in an artery) breaks loose and causes partial blockage - thrombosis - in blood vessel

characteristics of unstable angina

occurs at rest, still reversible ischemia (reduced blood supply to part of body that leads to lack of oxygen and nutrients), no necrosis of myocytes, incomplete coronary artery occlusion (coronary artery that supplies blood to heart is partially blocked), treatment is nitroglycerin, high risk of heart attack (myocardial infarction - MI)

ischemia

reduced blood supply to part of body that leads to lack of oxygen and nutrients

incomplete coronary artery occlusion

at supplies blood to heart is partially blocked

heart attack

MI - myocardial infarction

stable angina

caused by >70% narrowing (stenosis) of coronary artery, triggered by exertion or emotional stress, reversible ischemia, no necrosis of myoctyes

necrosis of myocytes

death of heart muscle cells (myocytes) due to lack of oxygen and nutrients

symptoms of stable angina

chest pain that last <20 minutes, radiation to left arm and jaw, SOB, diaphoresis

treatment of stable angina

rest or nitroglycerin (vasodilator - substance that widens/dilates blood vessels and allows blood to flow more easily

prinzmetal's (variant) angina

coronary artery vasospasm (temporary, sudden narrowing (spasm) of coronary artery that reduces blood flow to heart)

characteristics of prinzmetal's (variant) angina

episodic chest pain (that is unrelated to exertion), reversible ischemia, no necrosis of myocytes, EKG shows elevated ST segment

treatment of prinzmetal's angina

nitroglycerin and calcium channel blockers (help widen and relax blood vessels by blocking calcium from entering the muscle cells of heart and blood vessels)

MI - myocardial infarction

cause: necrosis (death) of cardiomyocytes, atherosclerotic plaque ruptures and leads to complete occlusion of coronary artery; other causes: embolus (clot that moves through blood stream and can block blood vessel), cocaine abuse, vasculitis (condition where blood vessels become inflamed)

coronary arteries

blood vessels that supply oxygen rich blood to heart muscle

embolus

clot that moves through blood stream and can block blood vessel

vasculitis

blood vessels become inflamed

symptoms of MI

crushing chest pain > 20 mins, pain radiating to left arm, jaw, and midback, dyspnea (SOB), diaphoresis (excessive sweating), CANNOT be relieved with nitroglycerin

affected areas of MI

occlusion (closing) of left anterior descending artery (LAD) -> necrosis in anterior wall and anterior interventrical septum (45% of cases), occlusion of right coronary artery (RCA) -> necrosis in posterior wall, posterior septum, papillary muscles (2nd most common)

progression of MI

initial MI leads to subendocardial necrosis (death of heart muscle cells in subendocardial layer which is inner layer of heart muscle just beneath heart's inner lining (endocardium), and continued ischemia that leads to transmural necrosis (full-thickness infarct)

MI diagnostic tests

1. blood cardiac enzymes: troponin I -> gold standard, levels rise 2-4 post-infarct, peaks at 24 hours, returns normal in 7-10 days, levels are > 0.40 ng/mL indicate heart damage

creatine kinase-MB (CK-MB) -> found in cardiac muscle, normal range is 5-25 IU/L

MI diagnostic tests cont.

2. electrocardiogram (ECG/EKG), ST elevation (STEMI), ST depression (NSTEMI)

congestive heart failure (CHF)

pump failure affecting either right (pulmonic) or left (systemic) heart

pulmonic circulation - right

pathway that blood takes as it move between heart and lungs, responsible for oxygenating the blood

process of pulmonary circulation

1. deoxy blood from body enter right atrium of heart

2. pumped into right ventricle that sends blood through pulmonary artery to lungs

3. in lungs, blood picks up oxygen and releases co2

4. oxy blood returns to left atrium of heart through pulmonary veins

systemic circulation - left

pathways that blood takes as it moves between heart and rest of body, delivers oxygen-rich blood to organs, tissues, cells, and returns deoxy blood back to heart

process of systemic circulation

1. oxy blood from left atrium is pumped into left ventricle

2. left ventricle pumps oxy-rich blood through aorta to rest of body

3. oxy and nutrients are delivered to tissues and waste products like co2 are picked up

4. deoxy blood returns to right atrium through veins like superior and inferior vena cava

left-sided heart failure

caused by hypertension, ischemic heart disease, MI, cardiomyopathy (groups of diseases that affect the heart muscle leading to weakening, thickening, stiffening)

left-sided heart failure

effects: pulmonary congestion -> pulmonary edema (fluid in lungs in the alveoli air sacs), crackles on auscultation (listening to internal sounds of body using stethoscope)

left-sided heart failure complications

- capillary rupture (patients can drown in fluids aka intra-alveolar hemorrhage)

- renin-angiotensin system activation -> decreases perfusion to kidneys and triggers release of renin (enzyme produced by juxtaglomerular cells in kidneys for BP, fluid balance, electrolyte levels, and increased renin leads to increase aldosterone (hormone produced by adrenal glands to regular body's sodium and water) which leads to fluid retention leads to WORSENED congestion

treatment of left-sided heart failure

ACE inhibitors -> used to treat hypertension, heart failure, kidney disease, etc. work by blocking angiotensin-converting enzyme (ACE)

right-sided heart failure

- most commonly caused by left-sided CHF

- also caused by chronic obstructive pulmonary disease (COPD) which leads to cor pulmonale -> condition where the right side of the heart (ventricle) enlarges and weakens due to high BP in arteries of lungs (pulmonary hypertension)

symptoms of right-sided heart failure

- jugular venous distension (JVD) -> visible swelling or bulging of jugular veins in neck when too much pressure or fluid buildup in venous system -> when right side of heart is unable to pump blood effectively, blood backs up into veins and causes the jugular vein to become distended

- hepatosplenomegaly (painful enlargement of liver and spleen)

- peripheral pitting edema (fluid accumulates in tissues of extremities and causes swelling that leaves pit with applied pressure)

- nutmeg liver (congestive hepatopathy - liver dysfunction caused by chronic congestion of blood flow)

JVD

jugular venous distension -> visible swelling or bulging of jugular veins in neck when too much pressure or fluid buildup in venous system -> when right side of heart is unable to pump blood effectively, blood backs up into veins and causes the jugular vein to become distended

hepatosplenomegaly

painful enlargement of liver and spleen

peripheral pitting edema

fluid accumulates in tissues of extremities and causes swelling that leaves pit with applied pressure

congestive hepatopathy

nutmeg liver -> liver dysfunction caused by chronic congestion of blood flow)

medications for CHF

- inotropic drugs -> alters the force of heart contraction by either increasing or decreasing the heart's pumping ability

- chronotropic drugs -> alter the heart rate

common drugs for CHF

- furosemide: diuretic -> increases urine production and helps the body remove excess fluid and salt

- carvedilol -> beta blocker that slows down the heart rate and reduce the force of contraction

- lisinopril (ACE inhibitor)

- digoxin -> increases intercellular Ca2+ concentration that leads to stronger heart contractions

congenital heart defects

- structural abnormalities in the heart

- defects occur when heart does not properly form and leads to problems with blood flow, oxygen delivery, heart functions, etc.

- can range from mild (small holes) to severe (complex malformations that require surgery)

- develop during embryogenesis (weeks 3-8 of gestation)

shunting types of CHD

- left to right shunting (acyanotic) -> when oxy-rich blood from left side of heart is abnormally redirected to right side and increases pulmonary blood flow

~ since blood is already oxygenated, cyanosis does not occur and makes defects acyanotic

shunting types of CHD cont.

right to left shunting -> cyanotic: occurs when deoxy blood from right side of heart bypasses lungs and enters systematic circulation resulting in low oxygen levels in blood and leads to cyanosis

blood flow through heart

overview of circulation: 2 sides

- right heart (pulmonary, low pressure) -> deoxy blood to lungs

- left heart (systemic, high pressure) -> oxy blood to body

step-by-step blood flow process

1. body -> right atrium (superior and inferior vena cava)

2. right atrium -> right ventricle (tricuspid valve)

3. right ventricle -> lungs (pulmonary valve and pulmonary artery)

4. lungs -> left atrium (pulmonary veins)

5. left atrium -> left ventricle (mitral valve)

6. left ventricle -> body (aortic valve and aorta)

7. body uses oxygen and cycle repeats

why does pressure matter for blood flow?

- left side = high pressure (systemic)

- right side = low pressure (pulmonary)

- BLOOD FLOWS FROM HIGH TO LOW PRESSURE

left to right shunts (acyanotic CHDs)

- blood moves from high pressure left side to low pressure right side

- increased pulmonary blood flow -> risk of pulmonary hypertension

examples of left to right shunting (acyanotic CHDs)

atrial septal defect, ventricular septal defect, patent ductus arteriosus

atrial septal defect (ASD)

2 types:

- ASD in ostium secundum (90%)

- ASD in ostium primum (10% and associated with down syndrome)

ASD in ostium secundum

- type of hole in heart

- happens when the wall between the two upper chambers of heart (atria) doesn't close properly during development

- this allows blood to flow between left and right atria and makes heart work harder

ASD in ostium primum

- hole in lower part of wall (septum) between two upper chambers of heart (atria)

- happens because septum doesn't fully develop during fetal growth

- requires surgical repair because it cannot close on its own

effects of ASD

- left to right (acyanotic) shunting

- right ventricular hypertrophy and pulmonary hypertension

- splitting of S2 heart sound which is caused by delayed pulmonary valve closure

right ventricular hypertrophy (RVH)

condition where right ventricle of heart becomes thicker and larger than normal; happens because right ventricle has to work harder to pump blood to lungs

ventricle

chamber of heart that pumps blood to lungs or body (right and left ventricle)

valve

flap-like structure that controls blood flow by opening and closing and prevents backflow

four types of valves to prevent blood from flowing backwards

- tricuspid valve: between right atrium and ventricle

- pulmonary valve: between right ventricle and pulmonary artery

- mitral valve: between left atrium and left ventricle

- aortic valve: between left ventricle and aorta

treatment of ASD

ASD closure procedure

exception to ASD: tricuspid atresia (agenesis)

congenital heart defect where tricuspid valve does not form properly

- instead of normal opening, there is solid tissue blocking blood flow from right atrium to right ventricle

tricuspid valve

between right atrium and ventricle

pulmonary valve

between right ventricle and pulmonary artery

mitral valve

between left atrium and left ventricle

aortic valve

between left ventricle and aorta

exception to ASD: hypoplastic right ventricle

due to lack of blood flow and workload, right ventricle remains underdeveloped and cannot effectively pump blood to lungs

exception to ASD: ASD with right to left shunting

blood must bypass the absent tricuspid valve flowing right to left through ASD or patent foramen ovale (PFO) into left atrium

exception to ASD: cyanosis due to systematic desaturation

deoxy blood from right atrium mixes with oxy blood in left atrium -> leads to reduced systemic oxygenation and cyanosis

patent foramen ovale (PFO)

small hole in heart that remains open after birth

- occurs when normal opening (foramen ovale) between two upper chambers of heart (atria) fails to close as it should after birth

exception to ASD: pulmonary circulation depends on PDA or VSD

since right ventricle is hypoplastic, blood must reach the lungs through patent ductus arteriosus (PDA) or ventricular septal defect (VSD)

- without these, pulmonary blood flow is severely restricted and worsens hypoxia (when part of body does not receive enough oxygen)

hypoplastic

underdeveloped and smaller than normal

pulmonary ductus arteriosis (PDA)

congenital heart condition where ductus arteriosus (normal fetal vessel) fails to close after birth

- blood can flow back into lungs instead of going to body and can put strain on heart or lungs

congenital

present at birth

ductus arteriosus

blood vessel that connects pulmonary artery (blood away from heart) to aorta (blood to body)

- allows blood to bypass lungs because baby gets oxygen from placenta

- meant to close within a few hours to days after baby starts breathing on its own

ventricular septal defect (VSD)

- most common congenital heart defect

- hole in wall (septum) between two lower chambers of heart (ventricles)

- allows oxy-rich blood from left ventricle to mix with oxy-poor blood in right ventricle and leads to extra blood flow in lungs and increased strain on heart

- associated with fetal alcohol syndrome

- 50% of small VSD close spontaneously

progression of VSD

- initially left to right shunting

- chronic pulmonary hypertension -> eisenmenger's syndrome : RV hypertrophy, polycythemia (high RBC form low oxygen), cyanosis (bluish skin), and clubbing (thickened fingertips from chronic hypoxia)

PDA (patent ductus arteriosus)

pathophysiology:

- before birth -> allows blood to bypass lungs

- closure occurs due to bradykinin (peptide for inflammatory response and helps regulate BP), oxygen, and decreased PGE2 (type of lipid produced by cells in response to injury, inflammation, etc.

- failure to close -> PDA (10% of CHD)

causes of PDA

congenital rubella syndrome

congenital rubella syndrome (CRS)

condition that occurs when a pregnant women contract rubella (german measles) during first trimester and can lead to serious birth defects

effects of PDA

left to right acyanotic shunting

right to left shunts (cyanotic CHDs)

- deoxy blood bypasses lungs -> enters systematic circulation

- reduced oxygen saturation -> cyanosis in body

examples of right to left shunts

persistent truncus arteriosus, tetralogy of fallot, transposition of great arteries

persistant truncus arteriosus (PTA)

failure of TA to divide -> single large vessel instead of separate aorta and pulmonary artery

- mixing of oxy and deoxy blood -> both ventricle eject blood into one trunk

- cyanosis develops due to reduced systemic oxygenaton

- associated with digeorge syndrome (genetic disorder caused by small deletion of chromosome 22 in 33% of cases

- increased right heart volume load -> pulmonary circuit overload and leads to heart failure within weeks of birth

truncus arteriosus

in the embryo, the truncus arteriosus is a single outflow tract from both ventricles that later divides into aorta and pulmonary artery

- eventually, the TA must undergo separation of these vessels to direct oxy-poor blood to lungs through pulmonary artery and oxy-rich blood to body through the aorta

tetralogy of fallot (ToF)

set of four congenital heart defects occurring together: pulmonary valve stenosis, right ventricular hypertrophy, ventricular hypertrophy, ventricular septal defect, overriding aorta (positioned over VSD)

pulmonary valve stenosis

heart defect where pulmonary valve (controls blood flow from right ventricle to pulmonary artery (to lungs)) is narrowed and makes it harder to pump blood through pulmonary valve in lungs

right ventricular hypertrophy

condition where the right ventricle (pumping deoxy blood into lungs for oxygen) of heart becomes thicker and enlarged

overriding aorta

congenital heart defect where aorta (main artery that carries oxy blood from heart to body) is positioned abnormally -> instead of arising from left ventricle, the aorta overrides both left and right ventricles so it can receive blood from both ventricles

- positioned above VSD

symptoms of ToF (tetralogy of fallot)

cyanosis, Tet spells, boot-shaped heart on x-ray

treatment of ToF (tetralogy of fallot)

knee-to-chest position which increases blood flow to lungs

tet spells

sudden episodes of severe cyanosis, difficulty breathing, fainting, collapsing

transposition of the great arteries (TGA)

CHD in which two main arteries (aorta and pulmonary artery) are switched or transposed

- means that aorta that is meant to carry oxy-rich blood to body arises from right ventricle while pulmonary artery that is meant to carry deoxy-blood to lung arises from left ventricle

in normal heart

- left ventricle pumps oxy-rich blood into aorta that circulates through body

- right ventricle pumps deoxy-blood into pulmonary artery and sends to lungs for oxygenation

in heart with TGA

- aorta arises from right ventricle

- pulmonary artery arises from left ventricle

effect of TGA

oxy-poor blood is pumped into body and oxy-rich blood sent back to lungs which causes body to be deprived of oxygen

symptoms of TGA

cyanosis, rapid breathing and/or SOB, fatigue, poor feeding, heart murmur

cause of TGA

maternal diabetes -> gestational diabetes that develop during pregnancy

treatment of TGA

surgery where aorta and pulmonary artery are surgically switched

diagnosis of TGA

physical examination (cyanosis and murmur), echocardiogram (ultrasound of heart), chest x-ray and ECG