medsurg week 7:

Cardiac Review Notes

Anatomy and Physiology of the Heart

  • Four Chambers of the Heart

    • Two atria (top)

    • Two ventricles (bottom)

  • Blood Flow

    • Right side: Pumps deoxygenated blood to the lungs

    • Left side: Pumps oxygenated blood to the body

  • Layers of the Heart

    • Endocardium: Innermost layer

    • Myocardium: Middle layer, muscular layer that contracts

    • Epicardium: Outermost layer

Heart Valves

  • Tricuspid Valve: Allows blood flow from right atrium to right ventricle

  • Mitral Valve: Allows blood flow from left atrium to left ventricle

  • Aortic Valve: Allows blood flow from left ventricle to aorta

  • Pulmonary Valve: Allows blood flow from right ventricle to pulmonary artery

Blood Flow Pathway through the Heart

  1. Blood enters the right atrium from the superior and inferior vena cava

  2. Flows through the tricuspid valve into the right ventricle

  3. Moves through the pulmonary valve into the pulmonary artery

  4. Blood travels to the lungs to become oxygenated

  5. Oxygenated blood returns to the heart through the pulmonary vein into the left atrium

  6. Blood flows through the mitral valve into the left ventricle

  7. Left ventricle pumps blood through the aortic valve into the aorta

  8. Oxygen and nutrients are delivered to tissues, and deoxygenated blood returns to the heart via the superior and inferior vena cava

Aortic Branches

  • Coronary Arteries: First branches from the aorta, nourish the heart muscle

Blood Vessel Types

  • Arteries: Carry blood away from the heart under high pressure

  • Veins: Return blood under low pressure, contain valves to assist blood back to the heart

  • Capillaries: Sites of gas and nutrient exchange, characterized by thin walls

Circulatory System Overview

  • Arterioles: Smaller blood vessels linked to arteries

  • Venules: Small blood vessels that connect capillaries to veins

Cardiac Conduction System

  • Electrical Impulses: Conducted throughout the heart to coordinate contractions

    • Initiated at the Sinoatrial (SA) Node (the heart's pacemaker)

    • Signal travels to the Atrioventricular (AV) Node, to the Bundle of His, and through Purkinje Fibers to stimulate contraction of the ventricles

Electrocardiogram (EKG) Components

  • P Wave: Represents atrial depolarization (atrial contraction)

  • PR Interval: Duration from start of P wave to start of Q wave; reflects time for electrical activity to pass from atria to ventricles

  • QRS Complex: Reflects depolarization and contraction of ventricles

  • ST Segment: Isometric line between ventricular depolarization and repolarization

  • T Wave: Represents ventricular repolarization (ventricles relaxation)

Cardiac Cycle Phases

  1. Atrial Systole: Atria contract, filling ventricles with blood

  2. Ventricular Systole: Ventricles contract, ejecting blood into the pulmonary artery (right side) or aorta (left side)

  3. Complete Cardiac Diastole: Heart muscle relaxes, allowing chambers to fill with blood

Measures of Cardiac Function

  • Cardiac Output: Volume of blood pumped by the heart each minute (normal: 4-8 liters/min)

  • Ejection Fraction: Percentage of blood pumped out of a ventricle with each heartbeat

    • Normal range: 50%-70%

    • Example: If 60% of blood is ejected from the left ventricle during contraction, it reflects a healthy ejection fraction

  • Stroke Volume: Amount of blood ejected with each heartbeat. Influenced by:

    • Preload: Volume of blood filling the ventricles before contraction

    • Contractility: Strength of ventricular contraction

    • Afterload: Pressure the ventricles must overcome to eject blood

    • Analogy: Heart as a balloon - preload = water (volume), contractility = squeeze strength, afterload = knot tightness (pressure)

Cardiac Reserve

  • Refers to the heart's ability to increase output during stress, exercise, or illness

  • Healthy heart can typically increase output up to a limit; failing hearts cannot compensate effectively, leading to symptoms

Nervous System and Heart Regulation

  • Sympathetic Nervous System: Activates 'fight or flight' responses, increasing heart rate and blood flow during stress

  • Parasympathetic Nervous System: Promotes 'rest and digest', decreasing heart rate and promoting recovery

Cardiovascular Assessment

  • Health History: Gather information regarding chest pain, shortness of breath, palpitations, and patient medications

  • Physical Examination: Assess vital signs, general appearance, skin color, and temperature of extremities

    • Conduct orthostatic vital signs to check blood pressure changes from lying to standing

  • Auscultation: Listen for heart sounds S1 and S2

Laboratory Studies

  • Cardiac Biomarkers: Indicators of heart muscle damage; include:

    • Creatinine Kinase (CK): Elevated CK-MB indicates cardiac muscle damage

    • Troponin: Highly specific for cardiac muscle injury; routinely measured in chest pain cases

    • Myoglobin: Found in both skeletal and cardiac muscle; indicates muscle damage

    • BNP (B-type Natriuretic Peptide): Indicates heart failure and fluid overload

    • C-Reactive Protein: Marker of inflammation linked to cardiovascular disease

    • Homocysteine: High levels linked to atherosclerosis and cardiovascular risks

Diagnostic Tests

  • Stress Tests: Evaluate heart response to increased workload

    • Exercise Stress Test: Patient exercises to measure heart performance

    • Pharmacologic Stress Test: Administration of drugs to simulate exercise; measure heart's responses

  • Echocardiogram: Ultrasound of the heart; assesses structures, ejection fraction, and valve function

    • Transthoracic: Non-invasive; uses gel and ultrasound probe

    • Transesophageal: More detailed; invasive; catheter goes down the esophagus

  • Cardiac Catheterization: Invasive procedure to assess heart chambers and vessels

    • Right Heart Catheterization: Measures pressures in the right heart

    • Left Heart Catheterization: Assesses left heart and evaluates coronary artery blockages using contrast agents

Regulation of Blood Pressure

  • Cardiac Output and Systemic Vascular Resistance (SVR) are key factors

    • Cardiac output increases blood flow

    • SVR influences resistance based on artery diameter

    • Constricted arteries increase blood pressure; dilated arteries decrease blood pressure

Renin-Angiotensin-Aldosterone System (RAAS)

  • A major regulator of blood pressure and volume; involves various hormones and proteins

Conclusion

  • Review and questions for clarification encouraged

  • Open to emails for further discussion

  • Note: This exhaustive guide serves as a comprehensive study note covering anatomy, physiology, tests, and regulatory mechanisms of the heart and circulatory system.