Cardiovascular

Alterations of Cardiovascular Function

Control of Cardiovascular Function

  • Disorders of Blood Flow & Blood Pressure Regulation

    • Overview of the cardiovascular system and its functions related to blood flow and pressure regulation.

Structure of Cardiovascular System

  • Components include:

    • External jugular vein

    • Subclavian vein

    • Superior vena cava

    • Right atrium

    • Internal jugular vein

    • Aortic arch

    • Left atrium

    • Right ventricle

    • Left ventricle

    • Right coronary artery

    • Left coronary artery

    • Anterior and posterior septa

    • Important structures: Pericardium (consisting of fibrous and visceral layers), myocardium, endocardium.

Principles of Blood Flow

  • Blood Flow Dynamics:

    • Blood flows down a pressure gradient (from high to low pressure) and through paths of least resistance.

    • Resistance is influenced by:

    • Length of the blood vessel (constant in the cardiovascular system)

    • Viscosity of the blood (thickness)

    • Anemia decreases viscosity; Polycythemia increases it.

    • A critical point: A 1-unit change in the radius of a vessel results in a fourfold change in resistance.

Types of Blood Flow

  • Laminar Flow:

    • Characterized by smooth, orderly flow; often silent and predictable.

  • Turbulent Flow:

    • Associated with obstructions and produces sounds called cardiac murmurs and vascular bruits.

Factors Regulating Cardiac Output

  • The four primary factors impacting cardiac output:

    • Preload: Amount of blood in the ventricles at the end of diastole.

    • Afterload: Resistance the heart must overcome to eject blood.

    • Contractility: Strength of the heart's contraction at a given preload.

    • Heart Rate: The number of times the heart beats in a minute.

  • Cardiac Output Formula: CO = HR imes SV where

    • CO = Cardiac Output

    • HR = Heart Rate

    • SV = Stroke Volume

The Cardiac Cycle

  • Phases of the cardiac cycle include:

    • Systole (contraction phase)

    • Diastole (relaxation phase)

  • Atrial Pressure, Ventricular Pressure, Aortic Pressure measurements critical during these phases. The cycle includes events of isovolumetric contraction, ventricular ejection, and ventricular filling.

Preload Details

  • Preload correlates with myocardial muscle stretch before contraction, represented by End-Diastolic Volume (EDV).

  • Frank-Starling Law states that increased preload increases stroke volume until physiological limits are exceeded.

  • Diagram and detailed relationship between preload vs. cardiac output illustrate this principle.

Afterload Details

  • Afterload primarily concerns the left ventricle and is influenced by the systemic vascular resistance (SVR).

  • The Mean Arterial Pressure (MAP) is a key clinical measure of afterload and reflective of the diastolic pressure, emphasizing its role over systolic in the filling phase.

Contractility Details

  • Reflects the strength of ventricular contraction independent of preload.

  • Left Ventricular Ejection Fraction (EF) is used to measure contractility and is defined as:

    • EF = rac{SV}{EDV}

  • Normal EF ranges from 60% to 75%.

Heart Rate Details

  • An increase in heart rate correlates with an increase in cardiac output, with clinical measures including pulse and ECG readings.

Disorders of Blood Flow (Arterial & Venous Disorders)

  • Arterial Disorders include:

    • Atherosclerosis

    • Characterized by plaque formation within arterial walls leading to reduced blood flow.

    • Related pathologies include hyperlipidemia and dyslipidemia.

  • Venous Disorders include:

    • Deep Venous Thrombosis (DVT)

    • Chronic Venous Insufficiency

Atherosclerosis Overview

  • Pathophysiology: Involves inflammatory responses, lipid accumulation, and plaque formation, leading to narrowing and potential blockage of arteries.

  • Key risk factors include elevated LDL cholesterol and decreased HDL cholesterol, impacting vascular health.

  • Consequences may include heart attack, stroke, and peripheral artery disease.

Aneurysms

  • Defined as localized abnormal dilatation of blood vessels due to weakening of vessel walls. Types include:

    • Fusiform, Saccular, and Dissecting aneurysms

  • Aneurysms are critical in areas stressed by high blood pressure and are often correlated with atherosclerosis.

Hypertension

  • Primary (Essential) Hypertension: No known cause but linked to lifestyle factors.

  • Secondary Hypertension: Caused by other conditions like renal disease or hormonal changes.

  • Complications include target-organ damage leading to conditions like heart disease and stroke.

  • Orthostatic Hypotension: Rapid blood pressure drop upon standing, necessitating patient education in transition management.

Cardiac Conduction and Rhythm Disorders

  • Insights into normal conduction pathways are presented, emphasizing the action potentials across the heart.

  • ECG interpretation of electrical activity:

    • Delays at the AV node, depolarizations and repolarizations reflected in the P-QRS-T sequence.

Myocardial Disorders and Coronary Artery Disease

  • Disorders can lead to ischemia and infarction:

    • Differentiation between myocardial ischemia (inadequate blood supply) and infarction (tissue death) is critical.

  • Serum Biomarkers: Troponin, CK-MB, and myoglobin are relevant in diagnosing cardiac events.

  • Presentation and management of acute coronary syndromes are essential for treatment outcomes.

Heart Failure

  • Pathophysiology: Inability of the heart to meet metabolic demands leads to various compensatory mechanisms.

  • Clinical manifestations include fatigue, edema, and decreased urine output.

  • Differentiation between heart failure types (right vs. left, high output vs. low output) guides treatment strategies.

Circulatory Failure (Shock)

  • Types of Shock:

    • Cardiogenic, Hypovolemic, Obstructive, Distributive (including neurogenic, anaphylactic, septic).

  • Emphasis on the need for early detection and intervention in compensated shock stages to improve outcomes.

Summary

  • This comprehensive outline provides a detailed explanation of cardiovascular function, highlighting the importance of recognizing disorders, their pathophysiology, and clinical manifestations to guide effective treatment strategies.