Functions of the Heart
• Regulates blood supply
– Changes in contraction rate and force match
blood delivery to changing metabolic needs
– Most healthy people can increase cardiac
output by 300–500%
Deoxygenated blood returns to
the heart via the superior and
inferior vena cava, enters the
right atrium, passes into the
right ventricle, and from here it
is ejected to the pulmonary
Oxygenated blood returning
from the lungs enters the left
atrium via the pulmonary veins,
passes into the left ventricle,
and is then ejected to the aorta.
Coordination of chamber contraction, relaxation
The Heart: Cardiac Output
• Cardiac output (CO)
• Amount of blood pumped by each side of the
heart in one minute
• CO = (heart rate [HR]) x (stroke volume [SV])
• Stroke volume
• Volume of blood pumped by each ventricle in
Conduction system of the heart
Heart contracts as a unit
Atrial and ventricular syncytia help conduct
electrical signals through the heart
Sinoatrial (S-A) node is continuous with atrial
S-A node cells can initiate impulses on their
own; activity is rhythmic
Electrocardiogram (ECG) can trace conduction
of electrical signals through the heart
Characteristics of blood vessels
Arteries and arterioles carry blood away from
Capillaries- site of exchange
Venules, veins- return blood to heart
Endothelium- prevents platelet aggregation
secretes substances that control diameter
of blood vessel
Tunica media- smooth muscle and connective
tissue. Innervated by sympathetic nerves
Missing in smallest arteries
Tunica externa- connective tissue; is
KIDNEYS AND BLOOD PRESSURE RUGULATION
THE “RENIN-ANGIOTENSIN SYSTEM”
Definition of Hypertension- Hypertension is very common disorder
particularly past middle age.
Hypertension could be that level of BP (blood pressure) at or above
which long term antihypertensive treatment will reduce cardiovascular
Blood Pressure- The force exerted by the blood against the walls of
the blood vessels.
Normal blood pressure- 140/90 mmHg (systolic/diastolic)
Types of Hypertension: Mild Hypertension- 90-99 mmHg/140-159 mmHg
Moderate hypertension- 100-109 mmHg/160-179 mmHg
Severe Hypertension- 110mmHg or more/180 mmHg or more
Classification: Primary hypertension- elevated BP without known cause, accounts
for over 95% of hypertension cases.
Secondary hypertension- cause of hypertension can be identified
accounts for 5% of hypertension cases.
DIURETICS- First line therapy for HT, promotes salt-water excretion
thereby relaxing the vascular constriction.
Thiazide diuretics- Hydrochlorthiazide, Chlorthalidone
Mechanism of action- act on DCT To inhibit Na/Cl Co-transport
ADR- Hypokalemia, hypoglycemia, hypercalcaemia
Marketed Products- Hydrazide Tab( cipla), Aquazide(Sun)
Loop diuretics- Furosemide, buetanide, torasemide
Mechanism of action- act on ascendind loop of henle by inhibiting
Used in only severe HT with cardiac and renal insuffiency
ADR- Hyperuricaemia, hypercalciuria, hyperemagnesaemia,
Marketed Products- Lasix (SANOFI AVENTIS)
ANGIOTENSIN CONVERTING ENZYME INHIBITORS– Enalapril,
Mechanism of action- blocks conversion of angiotensin 1 to ang. 2
which is vasoconstrictor and stimulates aldosterone release and thus
promotes Na retention, also inhibit degradation of bradykinin which is
ADR- hypotension after first dose, dry cough, angioneuratic oedema,
hyperkalaemia, fatal during pregnancy
Marketed products- Aceten tab(WOCKHARDT),
Angiopril(TORRENT), Acinopril(NICHOLAS), Ciprol(CIPLA)
ANGIOTENSIN RECEPTOR ANTAGONIST
CALCIUM CHANNEL BLOCKER
BETA ADRENERGIC BLOCKER
FACTS WITH HYPERTENSION
One fifth of the deaths in India are from coronary heart disease. By the
year 2020, it will account for one third of all deaths. Sadly, many of
these Indians will be dying young.
there appears to be a steady increase in hypertension prevalence over
the last 50 years, more in urban than in rural areas. Hypertension is 2530% in urban and 10-15% in rural subjects.
Current projections suggest that India will have the largest
cardiovascular disease burden in the world.
An Arrhythmia is an abnormal rhythm of the heart and is caused
by problems with Hearts electrical impulse generation or
conduction or both.
The electrical impulses may occur too fast or too slow or
irratically causing the heart to beat very fast or very slow .
The normal rate of heart beat in a healthy person ranges between
60-80 beats per second
Types of Arrhythmias
The arrhythmias are basically into following categories
depending upon there impact on rate of heartbeat.
1) Bradycardia :In which the rate of heart beat is very low i.e. less than 60pulse /min.
2) Tachycardia : In which the rate of heart beat is very high i.e. more than 100 pulse /min
3)Atrial Fibrillation (AF or AFib) :AF is a quivering or irregular heartbeat that can lead to
stroke and other heart-related complications.
4)Ventricular fibrillation: is life-threatening
Ventricular fibrillation (v-fib for short) is the most serious cardiac rhythm disturbance. The
lower chambers quiver and the heart can't pump any blood, causing cardiac arrest
Types of Bradycardia
Sinus bradycardia : The heart rate is less than 60 beats per min and it is considered as
normal and not needed tobe treated.
Sinus pause (also called sinus arrest) : During a sinus pause, the heart may miss one or
more beats because its natural pacemaker.
Sick sinus syndrome :Sick sinus syndrome happens when the normal pacemaker of the
heart (the sinus node) does not work properly
Heart block :Heart block refers to an abnormality in the way electricity passes through
the normal electrical pathways of the heart. The abnormality "blocks" the electrical
impulse from continuing through the normal pathways and usually results in a slower
Types of Tachycardia
Atrial or Supraventricular tachycardia (SVT) is a fast heart rate that starts in the upper
chambers of the heart.
some forms are called paroxysmal atrial tachycardia (PAT) or paroxysmal
supraventricular tachycardia (PSVT).
Sinus tachycardia = fast but steady Sinus tachycardia is a normal increase in the heart
rate The sinoatrial (SA) node --- the heart's natural pacemaker - sends out electrical
signals faster than usual. The heart rate is fast, but the heart beats properly.
Ventricular tachycardia is a fast heart rate that starts in the heart's lower chambers
(ventricles). It often occurs in life-threatening situations that dictate rapid diagnosis and
Physical causes of arrhythmia
Heart attack .
Congenital heart defects (present at the time of birth) e.g.
Wolff-Parkinson-White syndrome .
• Strong emotions, anger and other feelings may cause
imbalance in heart beats.
Combination of above two.
Electrolyte and pH imbalance.
Altering electrophysiological properties of
Mechanism of Arrythmias
When the SA node is suppressed the other specialized conduction tissues like artrial fibres, artrioventricular
nodal tissue, bundle if HIS, pirkinje fibres takes up the role of pacemakers and develop automaticity.such
conditions occur in the cases of myocardial ischaemia,hypopotassaemia circulating cathecoalmines.
This phenomenon occurs when the slope of depolarization in phase 1 increase causing premature ventricular
beats,ventricular tachycardias,ventricular,rhythm escape.
Reentry or Altered Impulse Propagation or Conductivity Defect
In this type of mechanism heart may transmit impulses slowly or act as a conduction blocks.simply slowing the
rate of transmission of impulses through ventricals causing ventricular tachycardias, A-V blocks,
ventricular premature beats.this can occur in case of
Vaughan Williams and Singh in 1969 divided
the antiarrythmatic drugs into four classes
according to their actions on the heart cells.
Na+ channel blocker
Ca channel blocker
Class I Drugs
• They are further classified into IA, IB, IC
IA : They moderately decrease dv/dt (electrical potential) of 0 phase.
Drugs: Quninidine, Procanamide, Disopyramide, Moricizine
IB : They make a little decrease in dv/dt of 0 phase.
Drugs : Lidocaine, Mexiletine
Ic : They markably decrease in dv/dt of 0 phase.
Drugs : Propafenone, Flecainide
Adenosine, Digitalis : For PSVT (Paroxysmal Supraventricular Tachycardia)
Anticholinergics-Antropine : for A-V Blocks(Artrio-Ventricular blocks)
Anti arrythmatic Drugs can only reset the heart beat by monitoring or controlling
the flow of ions or elements such as Na+,Ca2+.Cl-,K+ in the cardial cells.
Or they can Prolong the ERP(effective refractory period) and ADP(action
Simply antiarrythmatic drugs are used only for resseting or prolonging the action
The important Drugs which are used freqently are tabulised as follows
Important Drugs Used for Arrythmia
Oral 100-150 mg
i.v. 40-80 mg
i.v. 100-300 mg
Hepatic and biliary
I.V. 5 mg
Urine and faeces
I.V. 6-12 mg
< 10 sec
Adverse effects of
The major adverse effect of antiarrythmatic drugs are they themselves cause arrythmia.
Major part of these drugs are toxic if not administered accurately .e.g. lidocaine
They can cause fall or rise in blood pressure.
Other adverse effect seen in most antiarrythmatic drugs is
nausea,bradyarrythmia,drowsiness,pulmonary aveoltis and fibrosis.
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