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Venous Function

Venous Function

Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology transport deoxygenated blood and waste products from capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology in the periphery back to the heart. Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology are capacitance vessels Capacitance vessels Veins: Histology, meaning that they can stretch significantly, increasing the volume of fluid they can hold without significantly increasing their pressure. Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology respond to stimulation from the ANS ANS The ans is a component of the peripheral nervous system that uses both afferent (sensory) and efferent (effector) neurons, which control the functioning of the internal organs and involuntary processes via connections with the CNS. The ans consists of the sympathetic and parasympathetic nervous systems. Autonomic Nervous System: Anatomy, as arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology do, but to less of an extent. The effects of either venoconstriction or venodilation, however, impact venous capacitance. As veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology constrict, capacitance goes down, forcing more blood back to the heart (i.e., increasing venous return), which in turn affects the amount of blood that can be pumped out of the heart on the next heartbeat. Thus, changes in venous capacitance can significantly affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO). These effects can be plotted on graphs known as venous function curves.

Last updated: 4 Dec, 2021

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Properties of Veins and the Venous System

Properties of veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology

Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology are tubular collections of cells that transport deoxygenated blood and waste products from capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology in the periphery of the body back to the heart. 

  • Compared to arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology, veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology have:
  • Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology are capacitance vessels:
    • Capacitance: how much a vessel can stretch without significantly increasing pressure
    • Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology are collapsed when empty but able to distend significantly. This property is known as compliance Compliance Distensibility measure of a chamber such as the lungs (lung compliance) or bladder. Compliance is expressed as a change in volume per unit change in pressure. Veins: Histology.
    • The venous system can hold up to 60%–80% of the blood volume at rest.
  • Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology often accompany an artery:
    • Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology tend to surround the artery in an irregular branching network.
    • Functions as a countercurrent heat Heat Inflammation exchange system → allows cool blood returning from the periphery to be warmed before returning to the heart
  • Venous circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment is a low-pressure system:
    • Averages only 10 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg
    • The pressure is affected by gravity.
    • The closer the vessel is to the heart, the lower the pressure.

Overcoming gravity: valves and muscle pumps

Pressure in the venous system is too low to spontaneously push blood against gravity; moving blood against gravity up to the heart requires:

  • Skeletal muscle pump Pump ACES and RUSH: Resuscitation Ultrasound Protocols: 
    • When skeletal muscles Skeletal muscles A subtype of striated muscle, attached by tendons to the skeleton. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Muscle Tissue: Histology contract, they squeeze the veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology between them.
    • This pushes blood forward in the circuit, toward the heart, increasing preload Preload Cardiac Mechanics.
  • 1-way venous valves:
Muscle pump and venous valves

Muscle pump Pump ACES and RUSH: Resuscitation Ultrasound Protocols and venous valves:
As skeletal muscles Skeletal muscles A subtype of striated muscle, attached by tendons to the skeleton. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Muscle Tissue: Histology surrounding a vein contract, they compress the vessel, forcing the blood to move forward. One-way valves One-way valves Veins: Histology within the veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology prevent back- flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure and ensures blood only flows in one direction.

Image: “Skeletal Muscle Pump Pump ACES and RUSH: Resuscitation Ultrasound Protocols” by Philschatz. License: Public Domain

Regulating capacitance

  • Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology have smooth muscle in their walls:
    • Much less than similarly sized arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
    • However, still have the ability to constrict and dilate somewhat
  • Sympathetic stimulation → venoconstriction
  • Venoconstriction → ↓ capacitance → forces blood forward through the venous circuit → ↑ venous return to the heart 
  • Venodilation → ↑ capacitance → more blood can be held in venous circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment → ↓ venous return to the heart
  • Clinical relevance: The amount of venous return is directly related to preload Preload Cardiac Mechanics, which is one of the major components determining the stroke volume Stroke volume The amount of blood pumped out of the heart per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume. Cardiac Cycle, and thus cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO).
Venous pressure

Venous pressure:
Smooth muscle in vein walls can contract or relax, changing the luminal diameter within a vein. Sympathetic stimulation causes venoconstriction, reducing venous capacitance and forcing more blood back to the heart. This increases preload Preload Cardiac Mechanics, which in turn can increase stroke volume Stroke volume The amount of blood pumped out of the heart per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume. Cardiac Cycle and cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO).

Image by Lecturio.

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2:42
Central Venous Pressure (CVP) – Regulation of Venous Pressure

Venous Function Curves

Understanding Understanding Decision-making Capacity and Legal Competence venous function curves

Venous function curves (also known as systemic vascular function curves) plot central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter ( CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter) against CO.

Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output:

  • Represents the amount of blood pumped out of the heart per minute
  • CO = HR Ă— stroke volume Stroke volume The amount of blood pumped out of the heart per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume. Cardiac Cycle
    • HR: number of heartbeats per minute
    • Stroke volume Stroke volume The amount of blood pumped out of the heart per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume. Cardiac Cycle: volume of blood pumped out per contraction
  • CO is affected by:
  • Normally approximately 5–7 L/min
  • Usually plotted on the X- axis Axis The second cervical vertebra. Vertebral Column: Anatomy of venous function curves

Central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter: 

  • Represents the pressure in the vena cava near the right atrium
  • Used to assess:
    • Venous return to the heart (the major determinant of atrial filling pressure, and thus preload Preload Cardiac Mechanics)
    • Right atrial pressures Atrial pressures The pressure within the cardiac atrium. It can be measured directly by using a pressure catheter. It can be also estimated using various imaging techniques or other pressure readings such as pulmonary capillary wedge pressure (an estimate of left atrial pressure) and central venous pressure (an estimate of right atrial pressure). Cardiac Cycle
  • CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter increases with:
    • ↑ In venous blood volume
    • ↓ In venous compliance Compliance Distensibility measure of a chamber such as the lungs (lung compliance) or bladder. Compliance is expressed as a change in volume per unit change in pressure. Veins: Histology 
  • Normally between 0 and 12 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg
  • Usually plotted on the Y- axis Axis The second cervical vertebra. Vertebral Column: Anatomy of venous function curves
Example of a venous function curve

Example of a venous function curve:
Central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter ( CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter) is plotted along the Y- axis Axis The second cervical vertebra. Vertebral Column: Anatomy and cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO) is plotted on the X- axis Axis The second cervical vertebra. Vertebral Column: Anatomy. There is an inverse linear relationship Relationship A connection, association, or involvement between 2 or more parties. Clinician–Patient Relationship between the 2 variables until a CO is reached, at which point CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter drops to 0 (because veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology have the ability to collapse).

Image by Lecturio.

Venous function curve shape:

  • CO and CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter are inversely related:
    • Linear relationship Relationship A connection, association, or involvement between 2 or more parties. Clinician–Patient Relationship
    • As CO ↑ → CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter ↓ 
    • Increasing CO moves more blood out of venous circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment and into arterial circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment (in the short term) → ↓ venous blood volume → ↓ CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter
  • Because veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology can collapse completely, there is a CO at which CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter simply drops to 0.

Mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion systemic filling pressure ( mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion circulatory pressure)

  • Pressure in the venous system if the heart is not pumping
  • Represents the elastic Elastic Connective Tissue: Histology recoil Recoil Vessels can stretch and return to their original shape after receiving the stroke volume of blood ejected by the left ventricle during systole. Arteries: Histology potential stored in the walls of the systemic vasculature caused by the presence of blood sitting in the tubes
  • On venous function curves: the point where the curve meets the CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter axis Axis The second cervical vertebra. Vertebral Column: Anatomy (usually the Y- axis Axis The second cervical vertebra. Vertebral Column: Anatomy)

Factors affecting the shape/location of the curve:

  • Blood volume
  • Systemic vascular resistance Vascular Resistance The force that opposes the flow of blood through a vascular bed. It is equal to the difference in blood pressure across the vascular bed divided by the cardiac output. Vascular Resistance, Flow, and Mean Arterial Pressure (SVR)
  • Venous compliance Compliance Distensibility measure of a chamber such as the lungs (lung compliance) or bladder. Compliance is expressed as a change in volume per unit change in pressure. Veins: Histology

How blood volume affects venous function curves

  • Increase in blood volume:
    • Shifts the curve up and to the right
    • At a given CO, the CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter will be higher (and vice versa).
    • Mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion systemic filling pressure is increased because there is more fluid in the venous system.
  • Decrease in blood volume:
    • Shifts the curve down and to the left
    • At a given CO, the CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter will be lower (and vice versa).
    • Mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion systemic filling pressure is decreased because there is less fluid in the venous system.
  • Venous function curve when blood volume increases

    Venous function curve when blood volume increases

    Image by Lecturio.
  • Venous function curve when it decreases

    Venous function curve when blood volume decreases

    Image by Lecturio.

How systemic vascular resistance Vascular Resistance The force that opposes the flow of blood through a vascular bed. It is equal to the difference in blood pressure across the vascular bed divided by the cardiac output. Vascular Resistance, Flow, and Mean Arterial Pressure affects venous function curves

  • Increased SVR:
    • The slope of the curve steepens.
    • Mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion systemic filling pressure remains unchanged (because the total volume in the circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment is unchanged).
    • ↑ SVR means there is an ↑ afterload Afterload Afterload is the resistance in the aorta that prevents blood from leaving the heart. Afterload represents the pressure the LV needs to overcome to eject blood into the aorta. Cardiac Mechanics; this makes it harder to pump Pump ACES and RUSH: Resuscitation Ultrasound Protocols blood → ↓ SV → ↓ CO
    • Therefore, for a given CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter, the CO will be lower.
  • Decreased SVR:
    • The slope of the curve flattens out.
    • Mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion systemic filling pressure remains unchanged (because the total volume in the circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment is unchanged).
    • ↓ SVR means there is ↓ afterload Afterload Afterload is the resistance in the aorta that prevents blood from leaving the heart. Afterload represents the pressure the LV needs to overcome to eject blood into the aorta. Cardiac Mechanics; this allows the heart to more easily pump Pump ACES and RUSH: Resuscitation Ultrasound Protocols blood → ↑ SV → ↑ CO
    • Therefore, for a given CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter, the CO will be higher.

How venous compliance Compliance Distensibility measure of a chamber such as the lungs (lung compliance) or bladder. Compliance is expressed as a change in volume per unit change in pressure. Veins: Histology affects venous function curve changes

Venoconstriction:

  • Occurs in conjunction with ↑ in SVR due to sympathetic stimulation
  • The slope of the curve steepens.
  • Mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion systemic filling pressure increases (because more blood is being forced back into the heart).
  • Venoconstriction almost always occurs in conjunction with an ↑ SVR → there is an ↑ afterload Afterload Afterload is the resistance in the aorta that prevents blood from leaving the heart. Afterload represents the pressure the LV needs to overcome to eject blood into the aorta. Cardiac Mechanics → ↓ CO
Venous function curve showing the effects of venoconstriction

Venous function curve showing the effects of venoconstriction

Image by Lecturio.

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Vascular Function Curves – Regulation of Venous Pressure

Combined Venous/Cardiac Function Curves

Understanding Understanding Decision-making Capacity and Legal Competence combined venous/ cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curves

  • Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curves:
    • Plot CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter or left ventricular end-diastolic pressure Left ventricular end-diastolic pressure Cardiac Mechanics on the X- axis Axis The second cervical vertebra. Vertebral Column: Anatomy.
    • Plot CO on the Y- axis Axis The second cervical vertebra. Vertebral Column: Anatomy.
    • Demonstrates the principles of the Frank-Starling law (i.e., how preload Preload Cardiac Mechanics affects CO): 
      • Intrinsic properties of actin Actin Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or g-actin. In conjunction with myosins, actin is responsible for the contraction and relaxation of muscle. Skeletal Muscle Contraction and myosin Myosin A diverse superfamily of proteins that function as translocating proteins. They share the common characteristics of being able to bind actins and hydrolyze mgATP. Myosins generally consist of heavy chains which are involved in locomotion, and light chains which are involved in regulation. Within the structure of myosin heavy chain are three domains: the head, the neck and the tail. The head region of the heavy chain contains the actin binding domain and mgATPase domain which provides energy for locomotion. The neck region is involved in binding the light-chains. The tail region provides the anchoring point that maintains the position of the heavy chain. The superfamily of myosins is organized into structural classes based upon the type and arrangement of the subunits they contain. Skeletal Muscle Contraction filaments in the cardiomyocytes allow the cells to contract more, the more they are stretched.
      • As left ventricular end-diastolic pressure Left ventricular end-diastolic pressure Cardiac Mechanics increases due to increased ventricular filling Ventricular filling Cardiac Cycle, stroke volume Stroke volume The amount of blood pumped out of the heart per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume. Cardiac Cycle increases as well.
      • ↑ Left ventricular end-diastolic pressure Left ventricular end-diastolic pressure Cardiac Mechanics (i.e., ↑ preload Preload Cardiac Mechanics) → ↑ myofilament stretching → stronger contraction → ↑ SV → ↑ CO
  • Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curves can be “laid over” venous function curves. 
    • Venous function curve axes are flipped.
    • The 2 curves will cross each other at an equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy point: 
      • Represents the “steady-state” operating point for a particular set of physiologic conditions
      • Usually around a CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter of 2 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg and a CO of 5L/min (normal values)
Combined venous-cardiac function curve illustrating the equilibrium point between central venous pressure (cvp) and cardiac output (co)

Combined venous/ cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curve illustrating the equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy point between central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter ( CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter) and cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO):
A CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter of 2 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg and a CO of 5 L/min is the functional average for most people.

Image by Lecturio.

How changes in inotropy affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment combined venous/ cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curves

Clinical scenario #1: MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction leading to a decrease in inotropy

  • A ↓ in inotropy:
  • If venous function remains the same, the equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy point moves down along the venous function curve, resulting in:
    • ↓ CO
    • ↑ CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter
  • This ↓ CO may be too low to sustain life, so the body needs to compensate for the decreased inotropy in other ways.
  • It can do this by increasing blood volume (by increasing renal absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption of water):
    • ↑ Blood volume shifts the venous function curve up and to the right
    • The new equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy point has a higher CO (also has a higher CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter).
  • Volume overloading the heart allows the body to increase CO into a range capable of life-sustaining perfusion.
Venous function curves illustrating how the body can increase blood volume to compensate for a decrease in inotropy

Venous function curves illustrating how the body can increase blood volume to compensate for a decrease in inotropy:
(Left) When inotropy is decreased, central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter ( CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter) increases, whereas cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO) decreases. However, expanding the intravascular volume can compensate for these changes to improve CO (right).

Image by Lecturio.

How changes in blood volume affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment combined venous/ cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curves

Clinical scenario #2: hemorrhage

  • A ↓ in blood volume shifts the venous function curve down and to the left
  • ↓ Blood volume, means:
    • ↓ CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter 
    • ↓ CO (may be too low to sustain perfusion)
  • The body can compensate by increasing inotropy (heart pumps more strongly)
    • Steepens the cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) function curve
    • New equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy point has a higher CO
  • Stronger cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) contractions bring the CO back into a normal range, despite the lower CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter.
Venous function curves illustrating how an increase in inotropy (i. E. , contractility) compensates for a decrease in blood volume

Venous function curves illustrating how an increase in inotropy (i.e., contractility) compensates for a decrease in blood volume:
(Left) When volume is decreased, central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter ( CVP CVP The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter) decreases along with cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output (CO). However, increasing inotropy can compensate for these changes to improve CO (right).

Image by Lecturio.

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References

  1. Mohrman, DE, & Heller, LJ. (2018). Overview of the cardiovascular system. In Mohrman, DE, & Heller, LJ. (Eds.), Cardiovascular Physiology, (9th Ed., pp. 1–22). McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1153946098
  2. Mohrman, DE, & Heller, LJ. (2018). Vascular control. In Mohrman, DE, & Heller, LJ. (Eds.), Cardiovascular Physiology, (9th Ed., pp. 128–159). McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1153946722
  3. Mohrman, DE, & Heller, LJ. (2018). Regulation of arterial pressure. In Mohrman, DE., & Heller, LJ. (Eds.), Cardiovascular Physiology, (9th Ed., pp. 175–96). McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1153946898
  4. Baumann, BM. (2016). Systemic hypertension. In Tintinalli, JE., et al. (Eds.), Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, (8th Ed., pp. 399–407 ). McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1121496251
  5. Klabunde RE. (2021). Cardiovascular physiology concepts. Retrieved June 10, 2021, from https://www.cvphysiology.com/

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