Clase 18 Fisiología Cardíaca 3 - Función de las válvulas (IG:@doctor.paiva)

Functions of Cardiac Valves

Overview of Cardiac Valves

• The class introduces the functions of cardiac valves, including a general overview and specific focus on atrioventricular valves and semilunar valves. It also touches on valvular alterations such as stenosis and insufficiency.

Structure of Cardiac Valves

• Cardiac valves consist of a fibrous ring with leaflets that open to allow blood flow or close to prevent it. There are four main valves: the atrioventricular (tricuspid and mitral) and semilunar (pulmonary and aortic) valves.

Atrioventricular vs Semilunar Valves

• The tricuspid valve has three leaflets, while the mitral valve has two; both are supported by chordae tendineae connected to papillary muscles. In contrast, semilunar valves (pulmonary and aortic) do not have these structures.

Function During Cardiac Cycle

• During diastole (ventricular filling), the tricuspid and mitral valves open; during systole (ventricular contraction), the pulmonary and aortic valves open to allow blood ejection into major arteries.

Role in Preventing Backflow

• Atrioventricular valves prevent retrograde flow from ventricles to atria during systole due to increased ventricular pressure pushing against them, ensuring unidirectional blood flow through the heart.

Papillary Muscles and Chordae Tendineae

Importance of Papillary Muscles

• Only atrioventricular valves have papillary muscles and chordae tendineae, which help maintain valve closure during ventricular contraction by preventing excessive bulging into the atria. This mechanism is crucial for avoiding valvular prolapse.

Mechanism of Action

• Papillary muscles contract during systole, pulling on chordae tendineae to keep AV valve leaflets closed against high ventricular pressure, thus preventing backflow into the atria. This action is vital for maintaining proper heart function.

Semilunar Valve Functionality

Characteristics of Semilunar Valves

• Semilunar valves (pulmonary and aortic) lack supporting structures like papillary muscles or chordae tendineae; they rely solely on pressure differences between ventricles and arteries for closure during diastole, preventing backflow into ventricles.

Pressure Dynamics in Diastole

• During diastole, arterial pressures remain high from previous systolic contractions while ventricular pressures drop as they relax; this dynamic prevents retrograde blood flow from arteries back into ventricles via semilunar valve closure.

Closing Mechanisms of Heart Valves

Closing Dynamics

• The abrupt closure of semilunar valves occurs due to higher arterial pressures compared to lower ventricular pressures during diastole; this results in rapid closure without support structures leading to distinct sounds associated with heartbeats.

This structured approach provides an organized summary that captures key concepts discussed in the transcript while allowing easy navigation through timestamps for further reference.

Understanding Valvular Alterations

Overview of Valve Function and Anatomy

• The edges of the valves experience significant mechanical stress, leading to a robust fibrous tissue structure designed to withstand physical tension.

• Two primary types of valvular alterations are discussed: stenosis (restriction in valve opening) and insufficiency (inability to close properly).

Stenosis: Implications and Effects

• Stenosis refers to the inability of a valve to open fully, resulting in increased resistance during blood flow.

• Mitral stenosis causes reduced blood flow from the left atrium to the left ventricle, leading to pulmonary congestion due to backflow into the lungs.

• Aortic stenosis results in decreased blood flow into the aorta, requiring increased effort from the left ventricle, which can lead to concentric hypertrophy.

Insufficiency: Mechanisms and Consequences

• Insufficiency occurs when a valve cannot close completely, allowing retrograde blood flow. This condition can lead to volume overload in both chambers involved.

• In mitral insufficiency, retrograde flow occurs during systole, causing an increase in volume load on both the left atrium and ventricle.

Hypertrophy Types Related to Valvular Issues

• Left ventricular hypertrophy due to mitral insufficiency is eccentric because it results from volume overload rather than pressure overload.

• Aortic insufficiency leads to diastolic retrograde flow into the left ventricle, causing eccentric hypertrophy due to increased preload.

Causes of Valvulopathies

• Major causes include rheumatic fever (inflammation leading to hardened valves), congenital defects (e.g., Down syndrome), and endocarditis caused by bacterial infections.

• Streptococcus bacteria are often implicated in rheumatic fever; endocarditis may arise from oral bacteria entering circulation.

Understanding Valvulopathy: A Personal Dedication

Overview of Valvulopathy

• The discussion begins with an explanation of valvulopathy, specifically focusing on two types: insufficient valves and stenotic valves.

• An insufficient valve is characterized by a normal opening but fails to close completely, leading to potential complications.

• Conversely, a stenotic valve closes properly but has difficulty opening fully, which can impede blood flow.

Personal Dedication

• The speaker dedicates the video to their grandfather, Paiva, who passed away three years ago due to heart issues related to valvulopathy.