Post on 30-Oct-2014
description
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