Cardiovascular and Circulatory System

What does the cardiovascular system consist of & major functions?

• Consists of:

  • The heart → Cardio

  • Arteries, Veins, Capillaries → Vascular

• Major functions:

  • Provides a route for blood to travel from the heart to nourish the various tissues of the body

  • Carries cellular wastes to the excretory organs

  • Allows lymphatic flow to drain tissue fluid back into the circulation

  • Returns blood to the heart for recirculation

What are the four chambers, valves, layers, two vascular system? (A&P)

• Four chambers:

  • Right atrium and ventricle

  • Left atrium and ventricle

• Atrioventricular valves: tricuspid and mitral

• Semilunar valves aortic and pulmonic

• Three layers: endocardium, myocardium, epicardium

• Vascular system:

  • Arterial

  • Venous

• Cardiac hemodynamics

What is the Cardiac conduction system: Electrophysiology of the heart?

• SA node (Pacemaker)

• AV node

• Bundle of His

• R+L bundle branches

• Purkinje fibers

Explain the steps of the cardiac action potential

• Depolarization: electrical activation of cell caused by influx of sodium into cell while potassium exits cell

• Repolarization: return of cell to resting state caused by reentry of potassium into cell while sodium exits

• Refractory periods

  • Effective refractory period: phase in which cells are incapable of depolarizing

  • Relative refractory period: phase in which cells require stronger-than-normal stimulus to depolarize

Define cardiac cycle and what are the major sequential events?

• Refers to the events that occur in the heart from the beginning of one heartbeat to the next

• Number of cycles depends on heart rate

• Each cycle has three major sequential events:

  • Diastole

  • Atrial systole

  • Ventricular systole

Why does the left ventricle have the greatest pressure?

It pumps oxygenated blood to the entire body so it needs more pressure to push the blood

Define blood pressure BP

• Force exerted by blood against the blood vessels; systole/diastole

Define Systematic vascular resistance (SVR)

resistance the heart encounter when pumping blood into the systemic circulation

Define Cardiac output (CO)

amount of blood pumped by ventricle in liters per minute

Define Stroke volume (SV)

amount of blood ejected with each heartbeat

Define Heart rate (HR)

number of times the heart beats per minute

Define Mean arterial pressure (MAP)

average pressure in the arteries over a cardiac cycle

Define Ejection fraction

percent of end diastolic volume ejected with each heart beat (left ventricle)

What is pulse pressure and explain narrow v wide pulse pressure & identify causes?

• difference between the systolic and the diastolic pressures; normal pulse pressure is 40 mm Hg.

• A narrow pulse pressure (e.g., BP of 92/74 mm Hg and pulse pressure of 18 mm Hg) occurs when there is vasoconstriction that is compensating for a low stroke volume and ejection velocity (shock, HF, hypovolemia, mitral regurgitation) or obstruction to blood flow during systole (mitral or aortic stenosis). This compensation allows for adequate organ perfusion.

• A wide pulse pressure (e.g., BP of 88/38 mm Hg and pulse pressure of 50 mm Hg) is associated with conditions that elevate the stroke volume (anxiety, exercise, bradycardia), or cause vasodilation (fever, septic shock).

What affects stroke volume?

• Preload: degree of stretch of cardiac muscle fibers at end of diastole

• Afterload: resistance to ejection of blood from ventricle

• Contractility: ability of cardiac muscle to shorten in response to electrical impulse

What are the factors that influence co?

• CO= SV & HR

• Control of SV

  • Preload: Frank-Sterling Law; the more blood that fills the ventricle (stretches the muscle), the harder it contracts and the more blood it ejects. 

  • Afterload: affected by systemic vascular resistance, pulmonary vascular resistance

  • Contractility: increased by catecholamines, SNS, certain medications and decreased by hypoxemia, acidosis, certain medications

    • Increased contractility results in increased stroke volume

• Control of heart rate

  • Autonomic nervous system, baroreceptors

What is Mean Arterial Pressure, factors tht influence, and how to maintain adequte blood flow?

• Factors that influence MAP include:

  • Total blood volume (viscosity)

  • Cardiac output (stroke volume × heart rate)

  • Size and integrity of the vascular bed, especially capillaries

• To maintain adequate blood flow through the coronary arteries, MAP must be at least 60 mmHg.

  • A MAP between 60 and 70 mmHg (and higher) is necessary to maintain perfusion of major body organs, such as the kidneys and brain.

  • The lower the MAP, the worse the perfusion

What is the assessment of the cardiovascular system?

• Health history

• Demographic information

• Family/genetic history

• Cultural/social factors

• Risk factors

  • Modifiable

  • Nonmodifiable

What is the health history of cardio & circulatory system?

• Common symptoms

  • Chest pain/discomfort

  • Pain/discomfort in other areas of the upper body

  • SOB/dyspnea

  • Peripheral edema, weight gain, abdominal distention

  • Palpitations

  • Unusual fatigue, dizziness, syncope, change in LOC

What is the past history, family and social history to keep in mind with cardio & circulatory system?

• Medications

• Nutrition

• Elimination

• Activity, exercise

• Sleep, rest

• Self-perception/self-concept

• Roles and relationships

• Sexuality and reproduction

• Coping and stress tolerance

What is the physical assessment of the cardiovascular system?

• General appearance

• Skin and extremities

• Pulse pressure

• Blood pressure; orthostatic changes

• Arterial pulses

• Jugular venous pulsations

• Heart inspection, palpation, auscultation

• Assessment of other systems

Laboratory Tests (Cardiovascular)

Diagnostic tests used to evaluate myocardial injury, cardiac function, inflammation, clotting status, lipid levels, and overall cardiovascular risk.

Cardiac Biomarkers

Substances released into the blood when the heart muscle is damaged; used to diagnose and monitor myocardial injury such as myocardial infarction (MI).

Creatine Kinase (CK)

An enzyme found in cardiac and skeletal muscle that rises with muscle damage; not specific to the heart.

CK Isoenzymes

Different forms of creatine kinase that help identify the tissue source of muscle damage.

CK-MB

A cardiac-specific isoenzyme of CK; rises with myocardial injury and helps differentiate cardiac from skeletal muscle damage.

Myoglobin

A protein released early with muscle injury, including myocardial injury; rises quickly but is not cardiac-specific.

Troponin T

A cardiac protein released with myocardial cell damage; highly specific and sensitive for myocardial infarction.

Troponin I

A cardiac-specific protein released with myocardial injury; considered the preferred biomarker for diagnosing MI.

Blood Chemistry

Laboratory tests that evaluate electrolytes and metabolic substances to assess cardiovascular and overall physiologic status.

Hematology

Blood tests that evaluate red blood cells, white blood cells, and platelets to assess oxygen delivery, infection, and clotting ability.

Coagulation Studies

Tests that assess the blood’s ability to clot and monitor anticoagulant therapy.

Lipid Profile

A group of blood tests that measure cholesterol and triglyceride levels to assess cardiovascular disease risk.

Cholesterol

A lipid measured in the blood that contributes to atherosclerosis when elevated.

Triglycerides

A type of fat in the blood; elevated levels increase cardiovascular risk.

Low-Density Lipoprotein (LDL)

“Bad” cholesterol that contributes to plaque formation in arteries.

High-Density Lipoprotein (HDL)

“Good” cholesterol that helps remove cholesterol from the bloodstream.

Brain (B-type) Natriuretic Peptide (BNP)

is a neurohormone that helps regulate BP and fluid volume. BNP levels are useful for prompt diagnosis of HF in settings such as the ED. Elevations in BNP can occur from a number of other conditions such as pulmonary embolus, MI, and ventricular hypertrophy; elevated levels indicate heart failure.

C-Reactive Protein (CRP)

a protein produced by the liver in response to systemic inflammation. The high-sensitivity CRP (hs-CRP) test is used as an adjunct to other tests to predict CVD risk.

Homocysteine

an amino acid, is linked to the development of atherosclerosis because it can damage the endothelial lining of arteries and promote thrombus formation. Therefore, an elevated blood level of homocysteine is thought to indicate a high risk for CAD, stroke, and peripheral vascular disease, although it is not an independent predictor of CAD. Genetic factors and a diet low in folate, vitamin B6, and vitamin B12 are associated with elevated homocysteine levels

Blood Urea Nitrogen (BUN)

End product of protein metabolism excreted by kidneys; reflects renal perfusion and hydration status.

Clinical Significance of Elevated BUN

May indicate reduced renal perfusion due to decreased cardiac output or intravascular volume deficit.

Calcium (Ca²⁺)

Essential for blood coagulation, neuromuscular activity, and myocardial contractility.

Hypocalcemia

Decreased calcium levels reduce myocardial contractility and may cause hypotension.

Hypercalcemia

Increases myocardial contractility and irritability; can potentiate digitalis toxicity and increase risk of dysrhythmias.

Creatinine

A waste product filtered by the kidneys; sensitive indicator of renal function.

Clinical Significance of Elevated Creatinine

Indicates impaired renal function, often associated with decreased cardiac output or fluid imbalance.

Magnesium (Mg²⁺)

Necessary for calcium absorption, potassium regulation, ATP production, and myocardial contraction.

Hypomagnesemia

May cause ventricular dysrhythmias and increased myocardial irritability.

Hypermagnesemia

Can cause hypotension, bradycardia, heart block, and asystole.

Potassium (K⁺)

Essential for cardiac electrical activity and muscle contraction.

Hypokalemia

Causes dysrhythmias, including ventricular tachycardia and fibrillation.

Hyperkalemia

Causes decreased cardiac conduction, heart block, asystole, and life-threatening arrhythmias.

Sodium (Na⁺)

Regulates fluid balance and indirectly affects cardiac function.

Hyponatremia

Often indicates fluid excess and may be seen in heart failure.

Hypernatremia

Indicates fluid deficit, often caused by dehydration or water loss.

Coagulation Cascade

Injury to a blood vessel initiates thrombus formation through interactions among phospholipids, calcium, clotting factors, and thrombin to form fibrin.

Activated Partial Thromboplastin Time (aPTT)

Measures the activity of the intrinsic pathway and is used to assess the effects of unfractionated heparin.

Normal aPTT

Approximately 21–35 seconds.

Therapeutic aPTT Range (Heparin Therapy)

1.5–2.5 times baseline values.

Low Limit of Normal aPTT

11–13 seconds.

Prothrombin Time (PT)

Measures the extrinsic pathway and is used to monitor warfarin therapy.

International Normalized Ratio (INR)

A standardized measurement of PT that allows comparison between laboratories; used to monitor warfarin effectiveness.

Therapeutic INR Range

2–3, although specific ranges may vary based on diagnosis.

Heparin Monitoring

Effectiveness is monitored using aPTT, not INR.

Warfarin Monitoring

Effectiveness is monitored using PT/INR, not aPTT.

Complete Blood Count (CBC)

Measures total number of white blood cells, red blood cells, and platelets; also includes hemoglobin and hematocrit.

Hematocrit

Percentage of red blood cells found in 100 mL of whole blood.

Normal Hematocrit (Male)

42–52%.

Normal Hematocrit (Female)

36–48%.

Hemoglobin

Iron-containing protein in red blood cells that transports oxygen.

Normal Hemoglobin (Male)

14–17.4 g/dL.

Normal Hemoglobin (Female)

12–16 g/dL.

Clinical Significance of Low Hemoglobin/Hematocrit

May lead to serious consequences such as myocardial ischemia or acute myocardial infarction due to reduced oxygen delivery.

Platelets

First line of protection against bleeding; aggregate at sites of vascular injury.

Normal Platelet Count

140,000–400,000/mm³.

Platelet Function in Injury

Platelets adhere, aggregate, and initiate clot formation.

White Blood Cell Count (WBC)

Measures immune response and risk for infection.

Normal WBC Count

4,500–11,000/mm³.

WBC Monitoring

Especially important in immunocompromised patients and those with invasive procedures or serious infections.

What is electrocardiography (ECG/EKG)?

• 12-lead ECG

• Used to diagnose arrhythmias, conduction abnormalities, electrolyte disturbances, and chamber enlargement, as well as myocardial ischemia, injury, or infarction

What are the cardiac stress testing that are done?

• Exercise stress test

  • Patient walks on treadmill with intensity progressing according to protocols

  • ECG, V/S, symptoms monitored

  • Terminated when target HR is achieved

• Pharmacologic stress testing

  • Vasodilating agents given to mimic exercise

What are the diagnostic tests that can be done?

• Radionuclide imaging:

  • Myocardial perfusion imaging

  • Positron emission tomography

  • Test of ventricular function, wall motion

  • Computed tomography

  • Magnetic resonance angiography

What are the echocardiography that are done?

• Noninvasive ultrasound test that is used to:

  • Measure the ejection fraction

  • Examine the size, shape, and motion of cardiac structures

• Transthoracic

• Transesophageal

What is cardiac catheterization?

• Invasive procedure used to diagnose structural and functional diseases of the heart and great vessels

• Right heart catheterization

  • Pulmonary artery pressure and oxygen saturations may be obtained; biopsy of myocardial tissue may be obtained

• Left heart catheterization

  • Involves use of contrast agent

What are the nursing interventions for cardiac catherization?

• Observe cath site for bleeding, hematoma

• Assess peripheral pulses

• Evaluate temperature, color, and capillary refill of affected extremity

• Screen for arrhythmias

• Maintain bed rest 2 to 6 hours

• Instruct patient to report chest pain, bleeding

• Monitor for contrast-induced nephropathy

• Ensure patient safety

What are the types of hemodynamic monitering?

• Central venous pressure

• Pulmonary artery pressure

• Intra-arterial B/P monitoring

• Minimally invasive cardiac output monitoring devices