Cvs

Cardiovascular System (CVS)

Heart

The central blood pumping organ that receives & pumps out blood to the whole body.

Position: In middle mediastinum in between the two lungs, behind body of sternum, about 1/3rd of it is on the right side &2/3rd are on the left side of the body

Position of the Heart

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Inside heart there are

Four chambers

Four openings, guarded by

Four valves

Right & Left Atrium are receiving chambers

Right & Left Ventricle are distributing chambers

Superficial Anatomy of the Heart

Openings of Heart

1. Right atrio-ventricular opening

2. Left atrio-ventricular opening

3. Aortic opening

4. Pulmonary opening

1. Right atrio-ventricular opening

2. Left atrio-ventricular opening

3. Aortic opening

4. Pulmonary opening

There are four valves:

1. Right atrioventricular valve (tricuspid valve)

2. Left atrioventricular valve (mitral valve)

3. Pulmonary valve

4. Aoritc valve

Valves of Heart

Heart valves ensure unidirectional blood flow through the heart.

Atrio-ventricular (AV) valves lie between the atria and the ventricles.

AV valves prevent backflow into the atria when ventricles contract.

Aortic semilunar valve lies between the left ventricle and the aorta .

Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk.

Semilunar valves prevent backflow of blood into the ventricles

Valves of Heart

Functions of Valves

• Maintain unidirectional flow of blood

• Prevent backflow

• Produce heart sound

Circulatory Pathway

Right Atrium Left Atrium

Lungs

Left Ventricle

Right Ventricle

Aorta

Systemic Circulation

Pulmonary

valve

Pulmonary

veinsBicuspidvalve

Aorticvalve

Tissue

Tricuspidvalve

Heart Muscle: Syncytium

• Cardiac muscle fibers are striated – sarcomere is the functional unit

• Fibers are branched; connect to one another at intercalated discs. The discs contain several gap junctions

• Nuclei are centrally located

• Abundant mitochondria

• SR is less abundant than in skeletal muscle, but greater in density than smooth muscle

• Sarcolemma has specialized ion channels that skeletal muscle does not – voltage-gated Ca2+ channels

• Fibers are not anchored at ends; allows for greater sarcomere shortening and lengthening

Major Types of Cardiac Muscle

• Atrial Muscle

• Ventricular Muscle

• Specialized excitatory and conductive muscle fibers

SA NodeInter-nodal pathway AV Node The AV Bundle The left & right bundles of purkinje fibers

Heart Muscle: Cardiac Conduction System

• Specialized muscle cells “pace” the rest of the heart; cells contain less actin and myosin, are thin and pale microscopically

• Sinoatrial (SA) node; pace of about 65 bpm

• Internodal pathways connect SA node to atrioventricular (AV) node

• AV node could act as a secondary pacemaker; autorhythmic at about 55 bpm

• Bundle of His

• Left and right bundle branches

• Purkinje fibers; also autorhythmic at about 45 bpm

Properties of Heart Muscle

AutorhythmicityConductivity Excitability & Contractility All or none law Frank Starling Law Refractory PeriodAbsolute Relative Tonicity

Blood Vessel

Hollow tubes, which carry blood along with oxygen, nutrients & metabolic waste products within the body.

Types:• Artery• Vein• Capillary

Blood Vessel

Artery Vein

Carries oxygenated blood Carries deoxygenated blood

Carries nutrients to cell Carries waste products away from cell

Thick walled Thin walled

Blood flow is projectile Blood flow is sluggish

Difference between artery and vein

Circulation

Circulation:

The flow of blood & lymph throughout the body within a close system of vessels.

Types:• Systemic• Pulmonary• Portal

Circulatory Pathway

Blood flow through Heart

Pathway of Blood Through the Heart and Lungs

• Right atrium tricuspid valve right ventricle

• Right ventricle pulmonary semi lunar valve pulmonary arteries lungs

• Lungs pulmonary veins left atrium

• Left atrium bicuspid valve left ventricle

• Left ventricle aortic semi lunar valve aorta

• Aorta systemic circulation

Pathway of Blood Throughthe Heart & Lungs

Coronary Circulation

• Coronary circulation is the functional blood supply to the heart muscle itself

• Collateral routes ensure blood delivery to heart even if major vessels are occluded

Coronary Circulation: Arterial Supply

Arteries include:

1. the right and left coronary arteries

2. marginal arteries

3. anterior and posterior interventricular arteries and

4. the circumflex artery

Coronary Circulation: Venous Supply

Veins include:

• the great cardiac vein

• anterior and posterior cardiac veins

• the middle cardiac vein and

• the small cardiac vein

Coronary Circulation

Importance of Circulation

• Supply oxygen, nutrients to tissue

• Carry away CO2 & waste products

• Prevent intravascular coagulation

• Thermal balance

Important Terms

• Cardiac output: The amount of blood that is ejected by heart per minute.

• Stroke Volume: The amount of blood pumped out by ventricles in each beat/contraction. It is about 70-80 ml.

• Heart rate: The number of contractions of heart per minute.

• Cardiac Output = Stroke Volume Heart rate

Abnormalities of Heart Rate

Tachycardia: Increased heart rate above the upper normal physiological limit

Bradycardia: Decreased heart rate below normal physiological limit

Pulse

The rhythmic dilatation & elongation of arterial wall by intermittent ejection of blood from heart transmitted as a wave to the periphery.

Importance:• Heart rate is counted• Few clinical condition can be recognized:

Hypertrophy, arrhythmia, Fibrillation etc.

Some Diseases

• Myocardial Infarction: Acute ischaemic necrosis of an area of heart muscle.

• Heart Block: Transmission of impulse through the heart is blocked.

• Shock: Widespread hypo perfusion of tissue due to reduction of blood volume or cardiac output is called shock.

• Angina Pectoris: Cardiac pain due to impaired coronary blood flow.

BLOOD PRESSURE

AND

HYPERTENSION

Blood PressureIt is the lateral pressure exerted by

blood on the vessel wall while

flowing through it.

BP is expressed as

systolic (during systole) and

diastolic (during diastole) blood pressure.

Normal BP in healthy adult:

Systolic: 120 15 mm Hg

Dialstolic: 80 10 mm Hg

Blood pressure

Blood pressure = Cardiarc output Peripheral resistance

• Peripheral resistance is the resistance of the vessels to blood while passing within it.

Factors affecting Blood Pressure:

• Age • Sex• Build & Posture• Exercise• Sleep, meal • Emotion• Respiration etc.

Hypertension

Persistent rise of blood pressure above normalrange in respect of age & sex.

Types:• Essential Hypertension: 85 to 90%

Unknown cause.• Secondary Hypertension: 10 to 15%

Causes are: – Kidney diseases– Endocrine diseases– Stricture of Aorta– Drugs like oral contraceptives, steroids etc.

Receptors & Neurotransmitters

• Receptors are substances, lipoprotein in nature, present in the cell membrane or inside the cell, with which neurotransmitters and drugs combine in order to produce various effects.

• Neurotransmitters are chemical substances released from nerve terminals and acts on various receptors to produce physiological effects.

Adrenergic receptors

The receptors of the sympathetic nervous systems are called adrenergic receptors. Sympathetic neurotransmitters like adrenaline and noradrenaline stimulates these receptors.

There are mainly two types of adrenergic receptors: (alpha) and (beta) receptors. They are further subdivided into 1, 2, 1 and 2 receptors.

These receptors are found in heart, blood vessels, kidney, pancreas, uterus and some other organs.

Complications of Hypertension

Affected organs:

• Brain

• Eye

• Heart

• Kidney

• Artery

Brain:

• Cerebral hemorrhage

• Cerebral infarction

• Stroke

• Paralysis and

• even death

Eye:

Retina is damaged leading to blindness

Heart:• Coronary artery disease• Left ventricular hypertrophy• Left ventricular failure• Artial fibrillation

Kidney:• Proteinuria• Progressive renal failure

Artery:• Atherosclerosis• Aneurism

Antihypertensive Drugs Drugs that are used to control hypertension are called

antihypertensive drugs.

Antihypertensives are mainly of following groups:

• Diuretic

• Alpha Blocker

• Beta Blocker

• Calcium Channel Blocker

• ACE inhibitor

• Angiotensin II antagonist

Diuretics

Diuretics promote the excretion of water and electrolytes by the kidneys.These are used either alone or in combination to reduce blood pressure.

Classification of Diuretics:1. Loop diuretics (high efficacy)2. Thiazides (moderate efficacy)3. K+ sparing diuretics (low efficacy)

Diuretics

1. Loop diuretics:· Frusemide· Ethacrynic acid

2. Thiazides:· Hydrochlorothiazide· Bendrofluazide

3. K+ sparing diuretics:· Spironolactone· Amiloride

Alpha Blocking drugs

Alpha () blockers block the 1 & 2 adrenoceptors.

Blockade of 1 receptor results in vasodilatation leading to fall of blood pressure due to decrease in peripheral resistance.

Drugs are:

• Prazosin

• Doxazosin

• Terazosin

Beta Blockers

Beta blockers block beta adrenergic receptor and are used in the management of cardiovascular disorder like hypertension, angina pectoris , cardiac arrhythmia and myocardial infarction.

Beta Blockers

Drugs Receptors blocked

Atenolol

1Metoprolol

Butaxamine 2

Propanolol

both

1 and 2

Timolol

Labetolol

Carvedilol 1, 2 and 1

Calcium Channel Blockers

Calcium Channel Blockers inhibit the influx of calcium in vascular smooth muscle and myocardial cells. This results in dilatation of coronary and peripheral arteries & arterioles.

CCB have no effect in venous tone.

Drugs used as calcium channel blockers are

• Amlodipine• Nifedipine • Diltiazem• Verapamil • Lacidipine• Lercanidipine etc.

ACE Inhibitors

Angiotensin II is a very potent vasoconstrictor.

ACE Inhibitors inhibit angiotensin converting

enzyme (ACE) thus preventing conversion of

Angiotensin I to Angiotensin II . This results in

vasodilation and fall of blood pressure.

Drugs used as ACE Inhibitors are:

Captopril

Enalapril

Lisinopril

Ramipril

Angiotensin II Receptor Antagonists

These act mainly by selective blockade of

Angiotensin II receptors resulting in vasodilation

and fall of BP

Drugs are:» Losartan» Irbesartan» Valsartan

Vasodilators

Vasodialators dilate arterioles and decrease peripheral resistance; thus lower blood pressure.• Oral vasodilators:

HydralazineMinoxidil

• Intravenous:Sodium nitroprussideDiazoxide

Centrally Acting Antihypertensives

These stimulate 2 adrenoceptor in the CNS results in a reduction in sympathetic tone and a fall in blood pressure.

Drugs are:

» Clonidine

» Methyldopa etc.

Guideline for the use of Antihypertensives

Grading of Hypertension

Hypertension can be graded on the basis of

diastolic blood pressure.

Mild : 90 to 105 mm Hg

Moderate: 105-120 mm Hg

Severe: >120 mm Hg

Malignant: rising rapidly over 140 mm Hg

Treatment of Mild & Moderate Hypertension

First line treatment (any one drug)

1. Diuretics– Particularly in the elderly– Thiazides are the drug of choice

2. Beta blockers

3. ACE inhibitors or Angiotensin II antagonists can be used as alternative first line therapy, if the above drugs are not tolerated

Sencond line treatment (addition of a 2nd drug)

• If first line therapy fails

• To minimize side effects

Logical combination of drugs:

First line drug + Additional drug

ACE inhibitor + CCB

Diuretics

Beta blocker + Diuretics

Diuretics + ACE inhibitor

Beta blocker

In case of severe hypertension or despite second

line therapy hypertension is not controlled, a third

drug, especially, Vasodilators is added with second

line therapy.

Treatment of Severe Hypertension

Emergency management is lowering diastolic

BP upto 100 mm Hg with Intravenous

vasodilators.

Next management is as for severe hypertension.

Treatment of Malignant Hypertension

If hypertension is associated with other disease:

Associated with Choice of drugs Drugs avoided

Diabetes

Hyperlipidemia

ACE inhibitor

CCB

Asthma Diuretics

CCB

Beta blocker

Angina pectoris Beta blocker

CCB

Heart failure Diuretics

ACE inhibitor

Verapamil

Previous MI Beta blocker

ACE inhibitor