The cardiovascular system consists of the circulatory system and the heart.
Arteries carry blood away from the heart.
Capillaries are small vessels that facilitate the exchange of fluids and gases between the vascular system and interstitial space.
Veins carry blood towards the heart.
Basic Heart Anatomy
The tricuspid valve controls the flow of blood from the right atrium into the right ventricle.
The pulmonary valve controls the flow of blood from the right ventricle to the pulmonary arteries.
The mitral valve (aka bicuspid valve) controls the flow of blood from the left atrium to the left ventricle.
The aortic valve controls the flow of blood from the left ventricle to the aorta.
The heart is covered by a double-membrane structure called the pericardium.
The space inside the pericardium is filled with pericardial fluid, which cushions the heart and serves as a physical barrier, containing pain and mechanoreceptors.
Alterations of Cardiovascular Function
Hypertension
Hypertension is defined as elevated systolic and/or diastolic blood pressure.
Guidelines for hypertension are subject to change.
According to the Eighth Joint National Committee guidelines (2014), hypertension is considered blood pressure >140 systolic and/or >90 diastolic.
The American Heart Association 2017 guidelines define hypertension as SBP 130 and DBP 80.
Types of hypertension:
Primary hypertension: Caused by interactions between genetics and the environment.
Secondary hypertension: Caused by another medical illness (e.g., Cushing’s syndrome, pheochromocytoma, renal artery stenosis).
Risk factors for hypertension include family history, older age, obesity, glucose intolerance (prediabetes or diabetes), low socioeconomic status, smoking, and increased sodium intake.
Uncontrolled hypertension can lead to myocardial infarctions, cardiovascular muscle hypertrophy, eventual heart failure, kidney disease, and cerebrovascular accidents.
Severely elevated hypertension can be life-threatening, referred to as malignant hypertension or hypertensive crisis, leading to end-organ damage and cerebral edema, considered a medical emergency.
Most people with hypertension are asymptomatic (silent disease), except in malignant hypertension.
Diagnosis is confirmed if an individual has elevated blood pressure on at least two separate occasions.
Treatment:
Primary hypertension: Reduce or eliminate risk factors (smoking cessation, exercise), dietary changes (low sodium DASH diet), and anti-hypertensive medications.
Secondary hypertension: Treat the underlying cause.
Orthostatic Hypotension
Normal compensation for moving from lying down to standing involves increasing heart rate and vasoconstricting arterioles to raise blood pressure.
Orthostatic hypotension (postural hypotension) occurs when this mechanism fails.
Defined as a decrease in SBP by 20 mmHg and/or a decrease in DBP by 10 mmHg and/or onset of symptoms within 3 minutes of moving from lying to sitting or from sitting to standing.
Factors contributing to orthostatic hypotension: anti-hypertensive drugs, altered body chemistry, prolonged immobility, volume depletion, conditions causing venous pooling (pregnancy or lower extremity varicose veins).
Thrombus formation in large veins, typically in the lower extremities (deep femoral, superficial femoral, popliteal veins), but may occur in upper extremities (subclavian vein).
Symptoms are typically absent but may include swelling of affected limb.
High risk in hospitalized patients; prophylactic treatments with heparin, other medications, or mechanical SCDs are often used.
Major concern is that DVTs can break off and become emboli.
Factors that promote DVT (Virchow’s Triad):
Injury to the blood vessel endothelium:
Examples: atherosclerosis, hypertension, chronic hyperglycemia, direct injury (needle stick).
Abnormalities of blood flow (turbulent blood flow or venous stasis):
Examples: sickle cell disease, prolonged inactivity (post-operative or long flights), abnormal cardiac contractility (atrial fibrillation).
Hypercoagulability:
Examples: thrombocytosis, deficiency in anti-coagulation proteins or excess in pro-coagulation proteins, malignancy, testosterone and estrogen, smoking, pro-inflammatory states.
Embolism
A bolus of matter circulates in the bloodstream and then lodges, leading to obstruction of blood flow.
Air emboli (may occur from inappropriate air injection through central lines or IVs)
Amniotic fluid emboli
Bacterial emboli (typically occur from endocarditis)
Fat emboli (typically occur from long bone fractures).
Venous emboli are dangerous because they can travel to the lungs (pulmonary embolus).
Cardiac emboli are dangerous because they can travel to the brain (thromboembolic cerebrovascular accident) or cardiac vessels (myocardial infarction).
Atherosclerosis
Thickening and hardening of arterial blood vessel walls.
Initiated by injury to endothelial cells in the blood vessel wall.
Injury leads to accumulation of lipid-laden macrophages which release inflammatory markers and lead to the formation of a plaque.
Plaques may obstruct blood flow into distal tissues, leading to symptoms of hypoxia.
Some plaques may rupture, leading to the formation of a thrombus and possible embolus.
Leading cause of coronary artery disease and cerebrovascular accidents.
Symptoms depend on the organ affected by inadequate perfusion.
Atherosclerosis in extremities can lead to peripheral artery disease.
Atherosclerosis in cardiac arteries can lead to angina (chest pain) and myocardial infarctions.
Atherosclerosis in cerebrovascular arteries can lead to TIAs and strokes.
Treatment involves reducing risk factors and preventing lesion progression:
Exercising, smoking cessation, and controlling hypertension and diabetes.
Reducing LDL cholesterol levels by diet, medications, or both.
Coronary Artery Disease (CAD)
Any vascular disorder that narrows or occludes the coronary arteries.
The most common cause is atherosclerosis.
Results in an imbalance between coronary supply of blood and myocardial demand for oxygen and nutrients.
May result in reversible myocardial ischemia (angina) or irreversible tissue death (myocardial infarction or heart attack).
Risk factors may be separated as modifiable or nonmodifiable.
Non-modifiable risk factors: advanced age, positive family history, male genotype, female genotype after menopause.
Modifiable risk factors: cigarette smoking, hypertension, diabetes and insulin resistance, high cholesterol (dyslipidemia), obesity, and sedentary lifestyle.
Treatment of coronary artery disease bases on the level of tissue injury.
Three main types of coronary artery disease:
Stable angina
Unstable angina
Myocardial infarction (heart attack) acute coronary syndromes (ACS) medical emergencies
CAD: Cardiac Angina
Stable angina
Reversible chest pain caused by myocardial ischemia
Pain is typically described as heaviness or pressure and may radiate to neck, lower jaw, or left arm/shoulder and is associated with diaphoresis (sweating) and dyspnea (difficulty breathing)
Typically occurs in response to increased myocardial oxygen demand such as during exercise or emotional stress
Brief rest allows for return of adequate perfusion and symptoms disappear
EKG/Labs
May have transient ST depression or T wave inversion during stress
Normal troponin and CK-MB
Unstable angina
Considered an acute coronary syndrome (medical emergency)
Reversible myocardial ischemia however harbinger of impending myocardial infarction
New onset angina, angina that occurs during rest or does not resolve, angina that is increasing in frequency or severity
EKG/Labs
Associated with transient ST wave depressions and T wave inversions
Normal troponin and CK-MB
CAD: Myocardial Infarction
Myocardial infarction (heart attack)
Considered an acute coronary syndrome (medical emergency)
Prolonged ischemia leads to irreversible death of cardiac muscle
Note that patients may not have angina first – myocardial infarctions may be presenting symptom of coronary artery disease
Most common - severe sudden onset chest pain characterized as heaviness or pressure
Pain may radiate to neck, lower jaw, left arm/shoulder and associated with diaphoresis and dyspnea
Symptoms typically do not improve with rest
Older adults or individuals with diabetes are more likely to have “atypical” symptoms such as nausea and vomiting
Some may not have chest pain at all!
Note that it is impossible to distinguish between angina and myocardial infarction à need to do EKG and troponin/CK-MB tests
Will have elevated troponin and CK-MB (may need to do serial tests to confirm)
EKG changes such as ST elevation (STEMI) or ST depression and/or T wave inversion (NSTEMI)
Treatments
Emergency medical intervention!
Aspirin, oxygen, nitrates, and treatment of pain
Needs evaluation by cardiologist for possible cardiac catherization and percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG), anti-thrombotics or anticoagulation
Cardiomyopathies
Disorders of myocardium
Three main categories
Dilated: impaired systolic function leads to dilated ventricle and stretched myocardium
Hypertrophic: myocardium hypertrophy
Restrictive: stiff and noncompliant myocardium
Cardiomyopathies often progress to heart failure
Valvular Disorders
There are 4 main valves of the heart: tricuspid valve, pulmonary valve, mitral valve, and aortic valve
Disorders of any of these valves can cause diseases
These valvular disorders are also characterized by specific murmurs that can be heard on cardiac auscultation
Valvular stenosis: Valve orifice is constricted and narrowed
Valvular regurgitation: Valve fails to shut completely; can also be called valvular insufficiency or incompetence
Aortic Stenosis
Most common valvular abnormality
Can be caused by age-related calcification of aortic valve, congenital bicuspid valve, or inflammation related to rheumatic heart disease
Narrowing of the aortic semilunar valve causing diminished blood flow from the left ventricle into the aorta
To compensate, left ventricle may become enlarged or hypertrophic which will eventually increase cardiac oxygen demand
Clinical manifestations depend on severity of aortic stenosis
May include angina, myocardial infarction, syncope, and heart failure however prognosis is poor after onset of symptoms
Crescendo-decrescendo systolic heart murmur
Treatment may require valve repair or transplantation with prosthetic valve followed by long-term anticoagulation therapy
Aortic Regurgitation
Can be caused by congenital bicuspid valve, chronic hypertension, rheumatic heart disease, connective tissue disorders (ankylosing spondylitis), etc
Inability of aortic valve leaflets to close properly during ventricular diastole leading to a backwards “leak” of blood flow from aorta into the left ventricle
To compensate, left ventricle may become enlarged or hypertrophic which may eventually increase cardiac oxygen demand
Clinical manifestations depend on quantity of “leak” and degree of compensation
Chest pain, shortness of breath, and heart failure
Widened pulse pressure (high systolic pressure with normal diastolic pressure), diastolic decrescendo murmur
Treatment includes medications if not severe, or valve replacement if severe
Other Common Valvular Disorders
Mitral valve stenosis
Mitral valve regurgitation
Most commonly caused by mitral valve prolapse
Tricuspid valve regurgitation
Heart Failure
Pathophysiologic condition in which the heart is unable to generate adequate cardiac output, resulting in an inadequate perfusion of tissues or an increased diastolic filling pressure of the left ventricle, or both
Risk factors include myocardial infarction, hypertension, diabetes, smoking, alcohol use, renal failure, valvular heart diseases, and etc
Divided into different types:
Left Heart Failure (aka Congestive Heart Failure)
Right Heart Failure (aka Cor Pulmonale)
Systolic Failure (HFrEF)
Diastolic Failure (HFpEF)
Left Heart Failure
Systolic Failure (HFrEF)
Inability of heart to generate adequate cardiac output to perfuse tissues due to reduced stroke volume
Reduced stroke volume may be caused by reduced cardiac contractility, increased preload, or increased afterload
Common symptoms include fatigue, dyspnea, orthopnea, cough with frothy sputum (caused by pulmonary edema)
Diastolic Failure (HFpEF)
Inability of the heart to relax during diastole or decreased left ventricular compliance
Mainly caused by cardiac hypertrophy (induced by hypertension or myocardial ischemia)
Ejection fraction is preserved but hypertrophy causes excess pressure which leads to build up of fluid in the lungs
Common symptoms include fatigue, dyspnea on exertion, pulmonary edema
Right Heart Failure
Inability of the right ventricle to provide adequate blood flow into the pulmonary circulation
Most commonly caused by severe left heart failure (increase in left ventricular filling pressure is reflected back into the pulmonary circulation leading to R ventricular hypertrophy)
Less commonly caused by pulmonary hypertension
Right ventricular hypertrophy leads to systolic and diastolic failure, which can lead to a build up of fluid in systemic venous circulation
Common manifestations include dependent edema, jugular venous distention, hepatosplenomegaly, ascites
Right vs Left Heart Failure
Note that L heart failure often has signs of R heart failure and vice versa.
Ranges from asymptomatic occasional “missed” heart beats to severe life-threatening disturbances that affect the pumping ability of the heart
May be caused by an abnormal rate of impulse generation or an abnormal impulse conduction
Examples:
Life-threatening ventricular fibrillation or unstable ventricular tachycardia (considered part of ACLS)
Atrial fibrillation
Atrial flutter
Sinus bradycardia
Acute Pericarditis
Acute inflammation of the pericardium
Clinical manifestations: fever, myalgias, and malaise following by sudden onset severe chest pain
Treatment depends on the cause
Most causes of pericarditis are viral infections; treatment would be rest and supportive care
Bacterial pericarditis is more urgent and requires antibiotics
Post myocardial infarction pericarditis (Dressler syndrome); treatment is rest and supportive care while watching for development of pericardial effusion/cardiac tamponade
Cardiac Tamponade
Pericardial effusion
Accumulation of fluid in the pericardial sac
If too much accumulation, can lead to tamponade
Cardiac tamponade
Life-threatening condition in which excess pericardial fluid impairs contraction of atria and ventricles
Clinical manifestations include hypotension, dyspnea, tachycardia, jugular venous distension, cardiomegaly, and distant/muffled heart sounds
Treatment is pericardiocentesis
Pediatric Cardiology
Fetal Circulation
Fetal Circulation
Aorta
Placenta
Foramen Ovale.
Lung
Pulmonary Artery
Ductus Venosus
Liver
Umbilical Cord
Umbilical Vein
Oxygen-rich Blood
Oxygen-poor Blood
Mixed Blood
Umbilical Arteries
Ductus Arteriosus
Lung
Left Kidney
Newborn Changes to Circulation
The circulatory system of a newborn must change after birth
Gas exchange shifts from the placenta to the lungs
Fetal shunts close
Ductus venosus
After closure, the round ligament of the liver forms
Foramen ovale
Closes from increased pulmonary venous return and decreased inferior vena cava return
Ductus arteriosus
Closes from increased oxygen saturation in the systemic arterial blood
Patent Ductus Arteriosus
Failure of ductus arteriosus to close (normally occurs within a few hours of birth)
Leads to shunting of blood from aorta to pulmonary arteries
Clinical symptoms include hypercyanotic spells, signs of pulmonary over-circulation, unique machinery-like murmur, and weak pulses
Tetralogy of Fallot
Potentially life-threatening congenital disorder characterized by 4 main heart defects:
Large ventral septal defect (VSD)
Overriding aorta over the VSD
Pulmonary stenosis
Right ventricular hypertrophy
Clinical manifestations include dyspnea, restlessness, difficulty feeding
May have “tet” spells (hypercyanotic spells) triggered by crying or exertion
Coarctation of the Aorta
Congenital heart disease in which narrowing of the aorta impedes blood flow
Severity depends on degree of coarctation
Clinical manifestations may include:
More severe forms may present with heart failure and shock
Less severe forms may be asymptomatic but with hypertension in upper extremities and hypotension in the lower extremities
Systolic ejection murmur heard on cardiac auscultation