CARDIOVASCULAR SYSTEM

BY

Dr. A.R. JOSHI

PROFESSOR OF PHYSIOLOGY

CARDIOVASCULAR SYSTEM

Properties of Cardiac Muscle1. Autorhythmicity2. Conductivity3. Contractility4. Excitability5. All or none law6. Long refractory period

Electrodes (leads).

Amplifier

Recording unit

Bipolar leads – I, II, III.

Unipolar leads –

Limb leads – aVR , aVL , aVF

Chest leads – V1 to V6.

P- Wave- Depolarization of atria

QRS Complex- Depolarization of ventricles

T- Wave – Repolarization of ventricles

PR interval – AV conduction time• (0.12 – 0.16 Sec.)

QT interval – Ventricular systole• (0.26 – 0.30 Sec)

TP interval – Ventricular diastole• (0.46 – 0.50 Sec)

ST- Segment should be iso-electric

Diagnosis of arrhythmias & heart blocks.

Diagnosis of hypertrophy. Diagnosis of IHD. Diagnosis of other diseases like

electrolyte imbalance, pericarditis etc.

NERVE SUPPLY OF HEART

Autonomic Nervous SystemSympathetic supply( T1 to T5 )Effects of stimulation(Due to Noradrenalin and Adrenalin )1. Increase in Heart rate2. Increase in Force of contraction3. Increase in Excitability4. Increase in Conductivity(Effects blocked by alpha & beta blockers)

PARA SYMPATHETIC SUPPLY(Lt. & Rt. Vagus)

Effects of Stimulation :(Due to Acetyl Choline )1. Decrease in Heart rate2. Decrease in Force of contraction3. Decrease in Excitability4. Decrease in Conductivity

(All effects reverted by Atropine which blocks muscarinic 2 receptors)

CARDIAC CYCLE Total time – 0.8 sec when HR -75/min.

Events :Atrial events :

1. Atrial systole 0.1 sec2. Atrial diastole 0.7 secVentricular events : 1. Ventricular systole 0.3 sec2. Ventricular diastole 0.5 sec

VENTRICULAR SYSTOLE(contraction)

Events :1. Isovolumetric contraction phase2. Maximum ejection phase 3. Reduced ejection phase (First Heart sound occurs at beginning of Iso-volumetric contraction phase)

VENTRICULAR DIASTOLE(relaxation)

Events :1. Protodiastole2. Isovolumetric relaxation phase3. First rapid filling phase4. Diastasis5. Last rapid filling phase (Second heart sound occurs at beginning

of Isovolumetric relaxation phase )

FIRST HEART SOUNDCauses :

1. Closure of A-V valves 2. Contraction of Ventricles 3. Ejection of blood in big vessels

Peculiarities 1. Like LUBB

2. Intensity high & pitch low 3. More duration 4. Best heard at apex 5. Best heard with diaphragm 6. Coincides with carotid pulse

SECOND HEART SOUNDCauses :

1. Closure of S-L valves 2. Relaxation of Ventricles 3. Regurgitation of blood in big vessels

Peculiarities : 1. Like DUP

2. Intensity low & pitch high 3. Short duration 4. Best heard at base 5. Best heard with bell 6. Comes after carotid pulse

REGULATION OF HEART RATE

1. Nervous factors2. Hormonal factors3. Local factors4. Reflexes : Cardio acceleratory reflex

Cardio inhibitory reflex5. Miscellaneous factors like body temp.

CLINICAL EXAMINATION OF ARTERIAL PULSE

1. Rate2. Rhythm3. Volume4. Force5. Tension6. Equality7. Condition of vessel wall8. Peripheral pulsations9. Apex–pulse co-relation

CARDIAC OUTPUT

1. Stroke Volume (70 ml)2. Minute volume=S.V x H.R.(5 litres/min.)3. End systolic volume (60 ml)4. End diastolic volume (130 ml)5. Ejection systolic fraction (0.55)

=Stroke volume/End diastolic volume (Criterion of cardiac fitness )

FACTORS AFFECTINGSTROKE VOLUME

Venous return (Input factors) :1. Muscle pump2. Respiratory pump3. Blood volume4. Pressure gradient5. Venous tone

FORCE OF CONTRACTRION(Output factors)

1. Nervous factors2. Hormonal factors3. Frank-Starling’s law4. Coronary perfusion5. Diastolic period

CAUSES OF CARDIAC FAILURE

1. Ischaemic 2. Hypertensive 3. Valvular 4. Cardiomyopathies

RIGHT HEART FAILURECauses : COPD

Ischaemia Pulmonary valve diseases Secondary to chronic LVF

Effects: Pitting oedema over feet Prominent neck veins Liver enlargement & ascitis Hepato-jugular reflex present

LEFT HEART FAILURE

Causes : Hypertension Ischaemia Aortic valve diseases

Effects : Pulmonary oedema Basal crepitations Pulsus alternans

(Preferably with hospitalization)

1. Treat the basic cause 2. Oxygenation3. Salt restricted diet 4. Cardiotonic drugs like digitalis5. Drugs to reduce load on heart like diuretics

TREATMENT OF CARDIAC FAILURE

PHYSIOLOGICAL VARIATION

1. Age

2. Sex

3. Exercise

4. Posture

5. Diurnal

6. Mental stress

7. High altitude

FACTORS AFFECTING B.P.

Systolic B.P. depends upon Cardiac output

Diastolic B.P. depends upon Peripheral Resistance, which depends upon-

● Diameter of blood vessel

● Elasticity of blood vessel

● Viscosity of blood

● Velocity of blood

● Length of blood vessel

REGULATION OF B.P.

Short term regulation : Nervous regulation

1. Baroreceptors 2. Chemoreceptors 3. CNS ischemic response Hormonal regulation1. Renin angiotensin2. Catecholamines3. ADH

REGULATION OF B.P.(cont.. )

Intermediate :

1. Vascular stress relaxation

2. Capillary fluid shift mechanism

Long term :

1. Role of aldosterone

2. Role of kidney

HYPERTENSION

Definition :Types : 1. Primary

2. Secondary

Predisposing factors for primary hypertension : 1. Age 2. Sex 3. Heredity 4. Life style(Diet,sedentary work,stress,habits) 5. D.M. and obesity

HYPERTENSION (cont.. )

Symptomatology : ● Asymptomatic ● Classical symptoms ● Complications LVF Encephalopathy and stroke Nephropathy Retinopathy

TREATMENT OF PRIMARY HYPERTENSION

● Mild hypertension :

Life style modification Salt, fat and sugar restriction Tranquillizers if required

● Moderate hypertension : All above Diuretics

● Severe hypertension: All above

Anti hypertensives

ANTIHYPERTENSIVE DRUGS

1. Beta blockers e.g.atenolol

2. Calcium channel blockers e.g.amlodipine

3. ACE inhibitors e.g.captopril

4. Angiotensin receptor blockers e.g.losartan

5. Alpha receptor blockers e.g.doxazocin

SHOCKPersistent hypotension leading to

inadequate tissue perfusion.Types :1. Hypovolemic

2. Cardiogenic 3. Anaphylactic 4. Neurogenic 5. Septic

STAGES OF HYPOVOLEMIC

SHOCK

1. Compensatory : Blood loss upto 500ml

(All B.P.regulating mechanisms working to maximum)

2. Progressive : Blood loss upto 1 litre

(External help in form of fluid or blood transfusion )

3. Irreversible : Blood loss more than 1 litre

(Harmful positive feedback sets in )

PRINCIPLES OF TREATMENT

1. Hospitalization

2. Replacement therapy

3. Drugs e.g dopamine

4. Treatment of complications

e.g renal failure

PECULARITIES OF CORONARY CIRCULATION

(Normal flow –250 ml per min )

1. End arteries2. Filled in diastole3. High capillary density4. A-V difference of oxygen is high5. Local factors regulate blood flow6. Presence of beta receptors7. Energy derived from fatty acids

PECULARITIES OF PULMONARY CIRCULATION

( Normal flow –5lits per min )

1. Low pressure system2. No tissue fluid formation3. Distensible4. Nerves and hormones have no effect5. Hypoxia causes vasoconstriction6. Less blood flow to apex and more to base7. Rich lymphatic supply