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Questions and Answers
What is the primary cause of worldwide mortality as mentioned?
Which of the following best describes cardiomegaly?
What contributes to the unique pumping function of the left ventricular myocytes?
Which layer is NOT part of the trilayered architecture of heart valves?
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What change occurs in the left atrial cavity size during heart failure?
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How does aging affect the left ventricular cavity?
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Which of the following describes a common mechanism contributing to heart failure?
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What structural change is associated with the valves in heart failure?
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What is one of the endocrine functions of ventricular myocytes?
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What characteristic is observed in the right ventricular myocytes compared to the left?
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Which of the following best describes the Frank-Starling mechanism?
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What is the role of the Renin-Angiotensin-Aldosterone System in heart failure?
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Which component of the conduction system serves as the primary pacemaker of the heart?
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Which change occurs in epicardial coronary arteries during heart failure?
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Which of these is NOT a physiological mechanism that maintains arterial pressure during heart failure?
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What is characterized by a dilated ascending aorta and a rightward shift in heart failure?
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What type of hypertrophy is characterized by new sarcomeres being assembled in series, primarily leading to ventricular dilation?
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Which is NOT a cause of left-sided heart failure?
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Which symptom is commonly associated with left-sided heart failure?
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What morphological change is typically seen in the lungs of patients with left-sided heart failure?
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Which of the following is true about diastolic heart failure?
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What is a common clinical manifestation of both systolic and diastolic heart failure?
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What is the appearance of the liver in right-sided heart failure?
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Which process leads to hypertrophy in response to pressure overload?
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Study Notes
Cardiac Structure and Specializations
- Heart weighs 0.4-0.5% of body weight
- Hypertrophy: Increased heart weight or ventricular thickness
- Dilation: Enlarged chamber size
- Cardiomegaly: Increased cardiac weight or size (or both) resulting from hypertrophy and/or dilation
- Normal Heart Weight: 250-320 g (F), 300-360 g (M)
- Normal Ventricular Thickness: RV - 0.3-0.5 cm, LV - 1.3-1.5 cm
Myocardium
- Pumping function of the heart is driven by coordinated contraction (systole) and relaxation (diastole) of cardiac myocytes.
- Left ventricular myocytes are arranged in a spiral circumferential orientation to produce strong coordinated waves of contraction spreading from the apex to the base of the heart.
- Right ventricular myocytes have a less structured organization, producing weaker contractile forces.
- Heart also performs endocrine functions:
- Atrial cardiomyocytes contain Atrial Natriuretic Peptide
- Ventricular Myocytes contain B-Type Natriuretic Peptide
- Both peptides promote arterial vasodilation and stimulate kidneys to eliminate salt and water.
Valves
- Atrioventricular Valves: Tricuspid and Mitral
- Semilunar Valves: Aortic and Pulmonary
- Valves are lined by endothelium
- Valves have a three-layered architecture: Fibrosa Layer, Spongiosa Layer, Ventricularis or Atrialis Layer
Conduction System
- The conduction system of the heart is responsible for the sequential contraction of the heart chambers
- The components of the cardiac conduction system:
- Sinoatrial (SA) Node Pacemaker
- Atrioventricular (AV) Node
- Bundle of His (AV Bundle)
- Right and Left Bundle Branch Divisions
- Purkinje Network
Effects of Aging on the Heart
- Size of the left ventricular cavity is reduced.
- The basal ventricular septum protrudes into the left ventricular outflow tract.
- There is a decrease in myocytes.
- There is an increase in connective tissue.
- There is a deposition of extracellular amyloid.
- Valvular aging changes occur.
- Progressive atherosclerosis occurs.
Six Principal Mechanisms of Heart Failure
- Failure of the Pump: Systolic dysfunction or diastolic dysfunction
- Obstruction to Flow: Examples include calcific aortic valve stenosis, systemic hypertension, or aortic coarctation
- Regurgitant Flow: Backward flow of blood that results in increased volume workload and may overwhelm the pumping capacity of the affected chambers.
Heart Failure
- Often called Congestive Heart Failure (CHF).
- A heart cannot pump blood to adequately meet the metabolic demands of peripheral tissues, or can do so only at elevated filling pressures.
- Common end stage of many forms of chronic heart disease.
- Acute hemodynamic stresses, such as fluid overload, abrupt valvular dysfunction, or myocardial infarction, can all precipitate sudden CHF.
- Physiologic mechanisms maintain arterial pressure and perfusion of vital organs:
- Frank-Starling mechanism: Increases filling volumes -> dilates the heart -> enhances contractility.
- Activation of Neurohumoral Systems: Augment heart function and/or regulate filling volumes and pressures.
- Release of Norepinephrine: Elevates heart rate, augments myocardial contractility and increases vascular resistance.
- Activation of Renin-Angiotensin-Aldosterone System: Promotes water & salt retention.
- Release of Atrial Natriuretic Peptide: Diuresis and vascular smooth muscle relaxation.
- Myocardial Adaptations: Ventricular remodeling - collective molecular, cellular, and structural changes that occur in response to injury or altered ventricular loading.
Cardiac Hypertrophy
- The pattern of hypertrophy reflects the stimulus.
- Pressure-Overload Hypertrophy: New sarcomeres are assembled in parallel to the long axes of cells. Ex: Concentric Hypertrophy due to hypertension or aortic stenosis.
- Volume-Overload Hypertrophy: New sarcomeres are assembled in series within existing sarcomeres, leading primarily to ventricular dilation. Ex: Eccentric Hypertrophy due to valvular regurgitation.
- Cardiac hypertrophy is not accompanied by a proportional increase in capillary numbers.
- Cardiac hypertrophy is associated with heightened metabolic demands, deposition of fibrous tissue (interstitial fibrosis), and vulnerability to ischemia-related decompensation.
Molecular Changes in Hypertrophy
- Expression of immediate-early genes (e.g., FOS, JUN, MYC, and EGR1).
Left Sided Heart Failure
- Causes: IHD, Hypertension, Aortic and Mitral Valvular Diseases, Primary Myocardial Diseases
- Effects: Congestion of pulmonary circulation, Stasis of blood in the left sided chambers, Hypoperfusion of tissues.
- Morphology: Varies depending on the disease process. Nonspecific microscopic changes: Hypertrophy and interstitial fibrosis. Lung: Pulmonary congestion and edema. Heart failure cells.
- Clinical Manifestations: Cough and dyspnea, Orthopnea or paroxysmal nocturnal dyspnea, Cardiomegaly, tachycardia, a third heart sound due to volume overload (S3), or a fourth heart sound (S4) due to increased myocardial stiffness. Reduced ejection fraction, Azotemia, Cerebral hypoperfusion - hypoxic encephalopathy.
### Left Sided Heart Failure Types:
- Systolic Failure: Insufficient ejection fraction (pump failure) is caused by disorders that damage or derange the contractile function of the left ventricle.
- Diastolic Failure: The left ventricle is abnormally stiff and cannot relax during diastole. Hypertension is the most common underlying etiology. May appear in older patients without any known predisposing factors as an exaggeration of normal stiffening of the heart with age.
Right Sided Heart Failure
- Morphology: Varies with cause. Hypertrophy and dilatation of the right atrium and ventricle.
- Liver: Congestive hepatomegaly- "nutmeg liver" appearance, Centrilobular necrosis, Cardiac cirrhosis.
- Spleen: Congestive splenomegaly.
- Bowel Wall: Chronic congestion and edema.
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Description
Explore the intricate structures and specializations of the heart in this quiz. Learn about normal heart weight, hypertrophy, dilation, and the unique functions of myocardial cells. Test your knowledge on the cardiac myocytes' roles in pumping and endocrine functions.
