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Cardiac Cycle

Cardiac Cycle

The cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation describes 1 complete contraction and relaxation of all 4 chambers of the heart during a standard heartbeat. The cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation includes 7 phases, which together describe the cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation of ventricular filling, isovolumetric contraction, ventricular ejection, and isovolumetric relaxation. The cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation is frequently represented in a graph known as a pressure-volume loop, which shows how intraventricular volumes and pressures are related to one another throughout the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation.

Last updated: Aug 5, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Definition and Anatomy Review

Phases of the Cardiac Cycle

Normal Pressures in the Cardiac Chambers and Great Vessels

Pressure-Volume Loops

Clinical Relevance

Definition and Anatomy Review

Definitions

The cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation describes 1 complete contraction and relaxation of all 4 chambers of the heart during a standard heartbeat. The 7 phases of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation all occur in < 1 second.

Systole: cardiac muscle Cardiac muscle The muscle tissue of the heart. It is composed of striated, involuntary muscle cells connected to form the contractile pump to generate blood flow. Muscle Tissue: Histology contraction
Diastole: cardiac muscle Cardiac muscle The muscle tissue of the heart. It is composed of striated, involuntary muscle cells connected to form the contractile pump to generate blood flow. Muscle Tissue: Histology relaxation

Ventricular systole and diastole, and the coinciding phases of the cardiac cycle — Ventricular systole and diastole, and the coinciding phases of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation
Image by Lecturio.

Anatomy review

Blood sequentially flows through the heart in 1 direction through the following structures:

Deoxygenated blood enters the heart via the superior vena cava Superior vena cava The venous trunk which returns blood from the head, neck, upper extremities and chest. Mediastinum and Great Vessels: Anatomy (SVC) and the inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy ( IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy) →
Right atrium (RA) → tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy → right ventricle (RV) → pulmonary valve Pulmonary valve A valve situated at the entrance to the pulmonary trunk from the right ventricle. Heart: Anatomy →
Pulmonary trunk Pulmonary Trunk Truncus Arteriosus → pulmonary 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 → lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy (blood is oxygenated) → pulmonary veins Pulmonary veins The veins that return the oxygenated blood from the lungs to the left atrium of the heart. Lungs: Anatomy →
Left atrium (LA) → mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy → left ventricle (LV) → aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy → aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy →
Systemic 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 → 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 (blood is deoxygenated) → 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 → SVC/ IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy → back to the heart

General structure and flow of blood through the heart — The general structure and 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 of blood through the heart:
Blue areas represent deoxygenated blood, which passes through the right side of the heart. Red areas represent oxygenated blood, which passes through the left side of the heart. The right side of the heart pumps the deoxygenated blood to the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy. The left side of the heart pumps blood out to the systemic arterial system.
Image by Lecturio.

Phases of the Cardiac Cycle

Note: This animation does not have sound.

Phases 6, 7, and 1: ventricular filling

Ventricular filling occurs in 3 parts:

Ventricles are in diastole (relaxed).
Pressure in the ventricles is lower than the pressure in the atria.
= Atrioventricular (AV) valves (tricuspid and mitral valves) are open.
Phase 6:
- Blood rapidly fills the ventricles.
- Result of the high-pressure gradient between the atria and ventricles
Phase 7:
- Marked by slower passive filling
- P wave P wave Electrocardiogram (ECG) of the ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) occurs marking atrial depolarization Depolarization Membrane Potential.
- 90% of the ventricular volume is obtained through passive filling in phases 6 and 7.
Phase 1 Phase 1 Skin: Structure and Functions:
- Atrial systole (i.e., atrial contraction) occurs.
- Supplies the remaining 10% of the ventricular volume at rest (40% during exercise)
End-diastolic volume (EDV):
- The volume of blood in a single ventricle at the end of ventricular filling
- Approximately 130 mL in each ventricle

Diagram of the cardiac cycle highlighting phases 6 and 7 — Diagram of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation highlighting phases 6 and 7, ventricular filling:
As the left ventricle (LV) remains relaxed, the left ventricular pressure is less than the pressure in the left atrium (LA). The pressure differential opens the mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy and blood begins flowing from the LA into the LV, passively filling the LV. During this time, the left ventricular pressure remains low (red line), but the volume increases (blue line), representing a period of isoelectric activity on the electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) (yellow line).
Image by Lecturio.

Diagram of the cardiac cycle highlighting phase 1 — Diagram of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation highlighting phases 6 and 7, ventricular filling:
As the left ventricle (LV) remains relaxed, the left ventricular pressure is less than the pressure in the left atrium (LA). The pressure differential opens the mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy and blood begins flowing from the LA into the LV, passively filling the LV. During this time, the left ventricular pressure remains low (red line), but the volume increases (blue line), representing a period of isoelectric activity on the electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) (yellow line).
Image by Lecturio.

Phase 2 Phase 2 Skin: Structure and Functions: isovolumetric contraction

Isovolumetric means “same volume”. Phase 2 Phase 2 Skin: Structure and Functions represents ventricular contraction while both the AV valves and the semilunar valves are closed, which = no change in ventricular volume.

Ventricles depolarize: = QRS complex QRS complex Electrocardiogram (ECG) on ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)
Ventricular systole (i.e., contraction) begins.
Ventricular pressure rises sharply:
- Ventricular pressure > atrial pressure
- Tricuspid and mitral valves close as blood surges back against the valves (heart sound S1 S1 Heart Sounds).
Semilunar valves (aortic and pulmonic valves) remain closed because:
- Aortic pressure Aortic pressure Cardiac Mechanics > LV pressure
- Pulmonary trunk Pulmonary Trunk Truncus Arteriosus pressure > RV pressure
= No blood is ejected during phase 2 Phase 2 Skin: Structure and Functions of ventricular contraction.

Diagram of the cardiac cycle highlighting phase 2 — Diagram of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation highlighting phase 2 Phase 2 Skin: Structure and Functions, isovolumetric contraction:
Left ventricular volume (blue) remains the same, but the left ventricular pressure (red) sharply increases, occurring immediately following left ventricular depolarization Depolarization Membrane Potential (seen as the QRS complex QRS complex Electrocardiogram (ECG) on the ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) (yellow line)).
Image by Lecturio.

Phases 3 and 4: ventricular ejection

Blood is ejected from the ventricle during ventricular contraction (i.e., systole):
- Phase 3 Phase 3 Skin: Structure and Functions: rapid ejection
- Phase 4: slower ejection
Begins when the semilunar valves open, which occurs when:
- LV pressure > aortic pressure Aortic pressure Cardiac Mechanics
- RV pressure > pulmonary trunk Pulmonary Trunk Truncus Arteriosus pressure
Changes in ventricular pressure:
- Initially, a sharp increase continues in the 1st half of phase 3 Phase 3 Skin: Structure and Functions.
- Decrease as blood is ejected during the 2nd half of phase 3 Phase 3 Skin: Structure and Functions and continues through phase 4
End-systolic volume (ESV):
- Residual volume Residual volume The volume of air remaining in the lungs at the end of a maximal expiration. Common abbreviation is rv. Ventilation: Mechanics of Breathing left in the ventricles at the end of systole
- Approximately 60 mL
Stroke volume:
- The amount of fluid ejected during systole
- Stroke volume = EDV ‒ ESV
Ejection fraction (EF):
- The percentage of the EDV ejected during ventricular systole
- EF = stroke volume / EDV
- Average EF: approximately 55%–60%
Ventricular repolarization Repolarization Membrane Potential occurs during phases 3 and 4: = T wave T wave Electrocardiogram (ECG) on ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)

Cardiac cycle highlighting phases 3 and 4 — Diagram of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation highlighting phases 3 and 4, ventricular ejection:
As the left ventricle remains contracted, the ventricular pressure (red line) peaks and begins to decrease as blood is ejected out of the ventricle. The phase coincides with the ST segment ST segment Isoelectric segment between the s wave and the initial deflection of the t wave. Electrocardiogram (ECG) of the electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) followed by the T wave T wave Electrocardiogram (ECG) of ventricular repolarization Repolarization Membrane Potential (yellow line).
Image by Lecturio.

Phase 5: isovolumetric relaxation

Beginning of ventricular diastole
Aortic and pulmonary valves close due to decreasing intraventricular pressures.
Intraventricular pressure sharply decreases as the ventricular muscles relax and the cavity expands.
T wave T wave Electrocardiogram (ECG) resolution on ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)

Diagram of the cardiac cycle highlighting phase 5 — Diagram of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation highlighting phase 5, isovolumetric relaxation:
As the left ventricle begins isovolumetric relaxation, the ventricular pressure sharply drops (red line), but the volume does not change (blue line). The aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy closes in response to the pressure differential between the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy and the left ventricle. Aortic pressure Aortic pressure Cardiac Mechanics is shown by the top dotted line. The ventricle finishes repolarizing as shown on the electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) (yellow line).
Image by Lecturio.

Atrial pressures

Atrial systole: contraction of the atria ( phase 1 Phase 1 Skin: Structure and Functions)
Atrial diastole: relaxation of the atria (phases 2–7)
Atrial pressure waveforms:
- A wave: represents atrial contraction (i.e., atrial systole (also known as the “atrial kick”))
- C wave: reverberation of pressure into the atrium during ventricular contraction
- V wave:
  - During phases 3–5, the atria fill and the AV valves are closed.
  - The V wave marks the sudden drop in pressure as the AV valves open at the beginning of ventricular filling.

Diagram of the cardiac cycle highlighting the phases of atrial diastole — Diagram of the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation highlighting the phases of atrial diastole:
Atrial pressure is shown by the lower dotted line. The A wave indicates the increase in atrial pressure during atrial contraction. As the ventricles contract against the closed atrioventricular (AV) valves, the increase in pressure reverberates through the atria as seen in the C wave. The C wave coincides with the isovolumetric contraction of the left ventricle. Atrial relaxation begins during ventricular systole. With the AV valves closed, the atria are passively filled, increasing the atrial pressure. The V wave signifies the sudden fall in atrial pressure when the AV valves open to begin phase 6 (passive ventricular filling).
Image by Lecturio.

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Systole and Diastole – Cardiac Cycle

Isovolumetric Contraction: LV Phases – Cardiac Cycle

Atrial Systole and Diastole – Cardiac Cycle

Normal Pressures in the Cardiac Chambers and Great Vessels

The normal pressures found in the heart chambers and great vessels during ventricular systole and diastole are shown in the table and image below:

Differences in pressure between 1 chamber and another cause:
- Valves to open or close
- Blood to move forward in the circuit
Low-pressure areas: right side of the heart
High-pressure areas: left side of the heart

**Table: Normal pressures in the heart chambers and great vessels**
Location	Pressure during ventricular systole ( 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)	Pressure during ventricular diastole ( 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)
Right atrium	0–4	0–4
Right ventricle	25	4
Pulmonary 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	25	10
Left atrium	8–10	8–10
Left ventricle	120	10
Aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy	120	80

Pressures (in mm hg) within the chambers of the heart and great vessels — Pressures (in 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) within the chambers of the heart and great vessels:
The numerator represents the highest pressure achieved during systole and the denominator represents the lowest pressure achieved during diastole. Pressure differentials directly cause valve opening and blood movement.
A: aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
RA: right atrium
PT: pulmonary trunk Pulmonary Trunk Truncus Arteriosus
LA: left atrium
RV: right ventricle
LV: left ventricle
* denotes end-diastolic pressure
Image by Lecturio.

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Intracardiac and Vascular Heart Pressure – Cardiac Cycle

Pressure-Volume Loops

A graphic demonstration of how volumes and pressures change in the left ventricle throughout the cardiac cycle:
- Removes “time” from the cardiac cycle graphs
- Result: The diagram appears as a loop.
X-axis: LV volume
Y-axis: LV pressure
Point A: mitral valve opens
Point B: mitral valve closes
Point C: aortic valve opens
Point D: aortic valve closes
Ventricular filling (phases 6, 7, and 1):
- Segment A → B
- Seen as the “flat-ish” line across the bottom of the graph, moving from left to right
- Volume increases.
- Because the mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy is open, pressure increases minimally.
Isovolumetric contraction ( phase 2 Phase 2 Skin: Structure and Functions):
- Segment B → C
- Seen as the vertical line going straight up
- The mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy closes at point B.
- The aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy doesn’t open until point C: = Volume change is not possible with both valves closed.
- The ventricular contraction causes an increase in LV pressure without changes in volume.
Ventricular ejection (phases 3 and 4):
- Segment C → D
- Seen as the curved line along the top, moving from right to left
- The aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy opens allowing blood to leave: = volume falls
- Ventricles contract: Pressure increases until volume falls, causing pressure to also fall.
Isovolumetric relaxation (phase 5):
- Segment D → A
- Seen as the vertical line going straight down
- The aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy closes.
- The mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy does not open until point A: = Volume change is not possible with both valves closed.
- Ventricular relaxation causes a drop in LV pressure without changes in volume.

Left ventricular pressure-volume loop — Left ventricular pressure-volume loop:
The diagram illustrates the relationship Relationship A connection, association, or involvement between 2 or more parties. Clinician–Patient Relationship between left intraventricular pressure and volume throughout the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation. The segment from point A to point B represents ventricular filling. The mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy opens at point A and closes at point B. The segment from point B to point C represents isovolumetric contraction. The aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy opens at point C. The curved line from point C to point D represents ventricular ejection. The aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy closes at point D. The segment from point D to point A represents isovolumetric relaxation.
Image by Lecturio.

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Complete Picture of the Cardiac Cycle – Cardiac Cycle

Clinical Relevance

The following are common conditions affecting the cardiac cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation.

Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) (HF): Congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure ( CHF CHF Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure) refers to the inability of the heart to supply the body with the normal cardiac output Cardiac output The volume of blood passing through the heart per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with stroke volume (volume per beat). Cardiac Mechanics required to meet metabolic needs. Congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure may result in chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain, exertional dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, and episodes of hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension, dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome), and/or syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope. Ejection fraction of the LV is used to clinically categorize HF into either HF with preserved EF (≥ 50%) or HF with reduced EF (≤ 40%). Severity, prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas, and treatment regimens differ for each category.
Cardiomyopathies Cardiomyopathies A group of diseases in which the dominant feature is the involvement of the cardiac muscle itself. Cardiomyopathies are classified according to their predominant pathophysiological features (dilated cardiomyopathy; hypertrophic cardiomyopathy; restrictive cardiomyopathy) or their etiological/pathological factors (cardiomyopathy, alcoholic; endocardial fibroelastosis). Cardiomyopathy: Overview and Types: a group of myocardial diseases associated with structural changes of the myocardium Myocardium The muscle tissue of the heart. It is composed of striated, involuntary muscle cells connected to form the contractile pump to generate blood flow. Heart: Anatomy and impaired systolic and/or diastolic function in the absence of other heart disorders. Cardiomyopathies Cardiomyopathies A group of diseases in which the dominant feature is the involvement of the cardiac muscle itself. Cardiomyopathies are classified according to their predominant pathophysiological features (dilated cardiomyopathy; hypertrophic cardiomyopathy; restrictive cardiomyopathy) or their etiological/pathological factors (cardiomyopathy, alcoholic; endocardial fibroelastosis). Cardiomyopathy: Overview and Types are classified as dilated, restrictive, hypertrophic, or arrhythmogenic. With abnormal ventricular structure, the pumping action of the ventricles can be severely impaired, resulting in heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) and/or volume overload.

References

Mohrman, D. E., & Heller, L. J. (2018). Overview of the cardiovascular system. In Mohrman, D. E., & Heller, L. J. (Eds.), Cardiovascular physiology, (9th ed. pp. 1–22). McGraw-Hill Education. https://www.accessmedicine.mhmedical.com/content.aspx?aid=1153946098
Mohrman, D. E., & Heller, L. J. (2018). Vascular control. In Mohrman, D. E., & Heller, L. J. (Eds.), Cardiovascular physiology, (9th ed. pp. 128–159). McGraw-Hill Education. https://www.accessmedicine.mhmedical.com/content.aspx?aid=1153946722
Mohrman, D. E., & Heller, L. J. (2018). Regulation of arterial pressure. In Mohrman, D. E., & Heller, L. J. (Eds.), Cardiovascular physiology, (9th ed. pp. 175–196). McGraw-Hill Education. https://www.accessmedicine.mhmedical.com/content.aspx?aid=1153946898
Baumann, B. M. (2016). Systemic hypertension. In Tintinalli, J. E., et al. (Ed.), Tintinalli’s emergency medicine: A comprehensive study guide, (8th ed., pp. 399–407). McGraw-Hill Education. https://www.accessmedicine.mhmedical.com/content.aspx?aid=1121496251
Conduction System Tutorial. (n.d.). Retrieved June 1, 2021, from http://www.vhlab.umn.edu/atlas/conduction-system-tutorial/cardiac-action-potentials.shtml
Hall, J. E., & Guyton, A. C. (2016). The Heart. In Guyton and Hall Textbook of Medical Physiology (13th ed).
Saladin, K. S., Miller, L. (2004). Anatomy and physiology. (3rd ed., pp. 739–740).

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