Cardiac Physiology and Heart Failure Concepts

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Questions and Answers

What is the most common cause of primary myocardial failure?

Viral myocarditis

Pressure overload

Drug toxicity

Myocardial infarction (correct)

Which condition is characterized by congestion in the lungs and pulmonary edema?

Secondary cardiac failure

Left sided heart failure (correct)

Right sided heart failure

Primary myocardial failure

What is a physiological basis for treating heart failure that includes reducing the increase in blood volume?

Diuretics (correct)

Beta-blockers

Antihypertensives

Inotropic agents

In cases of secondary cardiac failure due to volume overload, which physiological approach can be considered?

Decreasing preload Signup and view all the answers

Which type of heart failure involves failure of the myocardium without prior disease in the heart?

Primary myocardial failure Signup and view all the answers

What is the definition of contractility in the context of cardiac physiology?

The intrinsic ability of the cardiac muscle to generate force. Signup and view all the answers

Which of the following conditions can depress contractility?

Hypercapnea. Signup and view all the answers

What is the effect of sympathetic stimulation on contractility?

It increases the strength of contraction. Signup and view all the answers

How does an increase in heart rate affect cardiac output between 60-90 bpm?

Cardiac output remains unchanged due to decreased stroke volume. Signup and view all the answers

What is the primary impact of increased afterload on stroke volume?

Stroke volume decreases due to increased resistance. Signup and view all the answers

What is a consequence of a very high heart rate (greater than 160 bpm)?

Marked decrease in cardiac output. Signup and view all the answers

Which of the following correctly describes preload?

The volume of blood returning to the heart. Signup and view all the answers

What does a positive inotropic effect indicate?

Increased strength of ventricular contractions. Signup and view all the answers

What does an increase in right atrial pressure (RAP) primarily affect in the ventricular function curves?

It increases the cardiac output. Signup and view all the answers

Which factor causes a leftward shift in the ventricular function curve?

Sympathetic stimulation. Signup and view all the answers

What does a rightward shift in the ventricular function curve indicate?

Decreased contractility of the heart. Signup and view all the answers

Which of the following contributes to the driving force of venous return?

Mean circulatory pressure minus central venous pressure. Signup and view all the answers

A decrease in cardiac output at any level of right atrial pressure is indicative of what condition?

Heart failure. Signup and view all the answers

Which of the following conditions can lead to direct myocardial depression?

Hypoxia. Signup and view all the answers

What is indicated by a mean circulatory pressure (MCP) of 7 mm Hg in the context of venous return?

It indicates the systemic filling pressure in the cardiovascular system. Signup and view all the answers

What is the normal range for Central Venous Pressure (CVP)?

0 to 5 mm Hg Signup and view all the answers

In the absence of heart function, how does mean circulatory pressure (MCP) relate to peripheral venous pressure (PVP)?

MCP is equal to PVP. Signup and view all the answers

What effect does increased contractility have on Right Atrial Pressure (RAP)?

RAP decreases Signup and view all the answers

How does hypovolemia affect Mean Circulatory Pressure (MCP)?

MCP decreases Signup and view all the answers

What defines Cardiac Reserve?

The difference between maximal and basal cardiac output Signup and view all the answers

Which mechanism primarily initiates short-lived increases in cardiac output to meet immediate demands?

Increased venous return Signup and view all the answers

What happens to venous return if the heart is arrested?

RAP becomes equal to MCP Signup and view all the answers

What is the primary difference between increases in cardiac output within the permissive limit and those beyond it?

Extrinsic mechanisms depend on adrenergic support for increased CO Signup and view all the answers

What is the initial response of heart rate during acute stress situations?

Heart rate increases due to vagal tone cancellation Signup and view all the answers

What is the maximum heart rate that can be reached due to sympatho-adrenal stimulation?

180 bpm Signup and view all the answers

Which condition exemplifies the mechanisms of cardiac dilatation due to volume overload?

Aortic valve incompetence Signup and view all the answers

In what scenario would cardiac hypertrophy occur as a response to pressure overload?

Hypertension Signup and view all the answers

What is a key limitation of cardiac reserve regarding heart rate?

Increased workload and oxygen consumption Signup and view all the answers

What happens if the end-diastolic volume (EDV) increases excessively?

Overstretch beyond Starling’s limit Signup and view all the answers

What occurs to the end-systolic volume (ESV) with excessive increases in contractility?

Decreases to low values Signup and view all the answers

What is a potential risk associated with cardiac hypertrophy exceeding certain limits?

Decreased blood supply to the ventricle Signup and view all the answers

What is the impact of sympatho-adrenal stimulation on stroke volume (SV)?

Decreases ESV and therefore increases SV Signup and view all the answers

What condition describes the heart's incapacity to provide adequate cardiac output despite normal filling conditions?

Heart failure Signup and view all the answers

Which of the following describes the clinical feature of forward failure in heart failure?

Inadequate cardiac output Signup and view all the answers

In the context of heart failure, what is the consequence of diastolic dysfunction?

Decreased ejection fraction Signup and view all the answers

Which factor is likely to cause high output failure?

Fever Signup and view all the answers

What happens to the ejection fraction (EF) in severe heart failure?

It decreases to as low as 20% Signup and view all the answers

How does hypertrophy affect the myocardium during heart failure?

Leads to diastolic dysfunction despite normal systolic function Signup and view all the answers

Which mechanism is primarily disrupted in systolic dysfunction?

Myocardial contractility Signup and view all the answers

What is a common consequence of increased end-diastolic pressure (EDP) in heart failure?

Decreased ventricular compliance Signup and view all the answers

Study Notes

Cardiac Output Part 2

Cardiac output is defined as the volume of blood pumped by the heart per minute.
The primary factors affecting cardiac output include preload, afterload, contractility, and heart rate.
Preload is the degree of stretch on the cardiac muscle fibers before contraction, primarily determined by right atrial pressure.
Afterload is the resistance the heart must overcome to pump blood into the systemic circulation.
Contractility is the intrinsic ability of the cardiac muscle to shorten and generate force. Healthy myocardium, normal blood supply, and normal metabolism are all necessary for normal contractility.
Heart rate is the frequency of heart contractions per minute.
Sympathetic stimulation increases contractility (positive inotropism).
Parasympathetic stimulation decreases contractility (negative inotropism).
An increase in heart rate between 60-90 bpm does not change cardiac output, but at higher rates, cardiac output increases.
Factors that decrease cardiac output include hypoxia, hypercapnia, acidosis, myocardial infarction, viral myocarditis, drug intoxication (e.g., barbiturates), and downregulation of β-adrenergic receptors.

Ventricular Function Curves

Ventricular function curves illustrate the relationship between preload (right atrial pressure) and cardiac output (CO).
An increase in right atrial pressure (RAP) leads to increased cardiac output.
Shifting of the curve represents changes in contractility.
The leftward (upward) shift of the curve represents an increase in contractility. This occurs during increased sympathetic stimulation.
The rightward (downward) shift of the curve indicates decreased contractility. It occurs during vagal stimulation or from myocardial depressants.

Venous Return Curve

The venous return curve depicts the relationship between venous return (blood flow into the heart) and right atrial pressure (RAP).
The driving force of venous return is determined by the difference between mean circulatory pressure (MCP) and central venous pressure (CVP).
Changes in venous return affect the end-diastolic volume and ejection fraction.

Cardiac Reserve

Cardiac reserve is the ability of the heart to increase its cardiac output to meet increased body demands.
Cardiac reserve is the difference between maximal and basal cardiac output.
Increased heart rate and contractility are mechanisms used to increase cardiac output in the short term, while increased blood volume (distension) and muscle hypertrophy are longer-term mechanisms.

Heart Failure (HF)

Heart failure is the inability of the heart to maintain adequate cardiac output to meet the body's needs under normal conditions or in response to increased demands.
Heart failure may be categorized as primary or secondary.

Mechanism of Low Cardiac Output

Systolic dysfunction and diastolic dysfunction are the principle mechanisms for low cardiac output in heart failure. Systolic dysfunction is a problem with the heart's ability to pump out blood, while diastolic dysfunction is a problem with the heart's ability to fill with blood.
Factors that reduce cardiac output include decreased contractility due to myocardial infarction or other factors, and problems with the relaxation and flexibility of the ventricles (diastolic dysfunction) due to hypertension and/or hypertrophy.

Types of Heart Failure

Primary myocardial failure is when the heart muscle itself is impaired, with no underlying issues.
Secondary myocardial failure is when the heart was previously normal, but the body's mechanisms to increase cardiac reserve were not sufficient to cope with the demands placed on the heart.

Physiological Basis of Treatment

Treatment of heart failure (HF) should address underlying and contributory factors.
Activities, meals, and temperature should be managed to reduce the demands placed on the heart.
Digitalis improves myocardial contractility.
Diuretics reduce fluid volume.
Treatment options should target the underlying cause for secondary HF.

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Description

This quiz covers essential concepts in cardiac physiology and the mechanisms of heart failure. It explores topics such as myocardial failure, contractility, preload, afterload, and the physiological responses to various cardiac conditions. Test your understanding of how these factors influence heart function and treatment approaches.