Prepared by MD, PhD., Associate Professor, Marta R. Gerasymchyk, pathophysiology department of Ivano-Frankivsk National Medical University, Ukraine. For medical students

2. Plan of the lecture
1. Organization of the circulatory
system.
2. Cardiac cycle.
3. Conductive system of the heart.
4. Mechanisms of compensation
5. Arhytmias of the heart. Deffinition.
Classification. Pathogenesis.
6. Ischaemic heart disease.
6. Heart failure.

3. Actuality of the lectureActuality of the lecture
The disorders of cardiac rhythm concern to complex manifestations of
pathology of heart. Its can arise in rather small damage of the conducting
system, and in some cases in structural changes. More often arrythmia
arise with infectious illnesses and intoxications as consequence of
miocarditis or dystrophy processes in cardiac muscle, and also in heart
ishemic disease, cardiosclerosis.
The disorders of cardiac rhythm arise also owing to reflex influences from
various interreceptors areas (disease of liver, intestinal tract, uterus), and
also in hemodynamic disorders (arterial hypertension). Not infrequently
аrrythmia is a result of disturbance of functions central and vegetative
parts of nervous system. For example, the increase of activity
parasymphatic nervous system lead to delay of conductivity. Similar is
observed also by overdose of some medicin drugs (digitalis, quinidine,
morphine). If bradycardia is accompanied complete atrioventricular
blockade, can occur ischemia of brain with loss consciousness and
occuring spasmes.
Arrythmia can be result in development of cardiac insufficiency.

4. FUNCTIONAL ORGANIZATION
OF THE CIRCULATORY SYSTEM
■ The circulatory system consists of the heartheart,
which pumps blood; the arterial systemarterial system,
which distributes oxygenated blood to the
tissues; the venous systemvenous system, which collects
deoxygenated blood from the tissues and
returns it to the heart; and the capillariescapillaries,
where exchange of gases, nutrients, and
wastes occurs.
■ The circulatory system is divided into two
parts: the low-pressure pulmonarylow-pressure pulmonary
circulationcirculation, linking the transport function of
the circulation with the gas exchange
function of the lungs; and the high-pressurehigh-pressure
systemic circulationsystemic circulation, providing oxygen and
nutrients to the tissues.
■ The circulation is a closed system, so the
output of the right and left heart must be
equal over time for effective functioning of
the circulation.

5. THE HEARTTHE HEART■■ TheThe heart is a four-chamberedheart is a four-chambered pumppump
consisting ofconsisting of two atriatwo atria (the right atrium,(the right atrium,
which receives blood returning to the heartwhich receives blood returning to the heart
from the systemic circulation, and the leftfrom the systemic circulation, and the left
atrium, which receives oxygenated bloodatrium, which receives oxygenated blood
from the lungs) andfrom the lungs) and two ventriclestwo ventricles (a right(a right
ventricle, which pumps blood to the lungs,ventricle, which pumps blood to the lungs,
and a left ventricle, which pumps bloodand a left ventricle, which pumps blood
into the systemic circulation).into the systemic circulation).
■■ Heart valvesHeart valves control the direction ofcontrol the direction of
blood flow from the atria to the ventriclesblood flow from the atria to the ventricles
(the(the atrioventricular valvesatrioventricular valves), from the right), from the right
side of the heart to the lungs (side of the heart to the lungs (pulmonicpulmonic
valvevalve), and from the left side of the heart), and from the left side of the heart
to the systemic circulation (to the systemic circulation (aortic valveaortic valve).).
■■ TheThe cardiac cyclecardiac cycle is divided into twois divided into two
major periods:major periods: systolsystole, when the ventriclese, when the ventricles
are contracting, andare contracting, and diastolediastole, when the, when the
ventricles are relaxed and filling.ventricles are relaxed and filling.
■■ TheThe work and efficiency of the heartwork and efficiency of the heart
is determined by the volume of blood itis determined by the volume of blood it
pumps out (pumps out (preloadpreload), the pressure that it), the pressure that it
must generate to pump the blood out ofmust generate to pump the blood out of
the heart (the heart (afterloadafterload), and the rate at which), and the rate at which
it performs these functions (it performs these functions (heart rateheart rate).).

9. Electrocardiogram (ECG)Electrocardiogram (ECG)

13. (Frank-) Starling Law(Frank-) Starling Law
• Within limits, the greater the stretching of the
muscle fibers (preloadpreload), the greater the force of
contraction.
• The extra force of contraction is necessary to
pump the increased volume of blood from the
ventricle.
• Cardiac output increases
Neural reflexesNeural reflexes
• Bainbridge reflex – increased heart rate due
to increased right atrial pressure
• Increased pressure in arteries stimulates a
baroreceptor reflex that decreases heart rate.

14. Cardiac ConductionCardiac Conduction
SystemSystem

15. Origin and SpreadOrigin and Spread
of Excitation in theof Excitation in the
HeartHeart
c

16. ARRHYTHMIAS OFARRHYTHMIAS OF
HEARTHEART Violation of rhythm of heartViolation of rhythm of heart accompanies aaccompanies a
number of diseases of the cardio-vascular system.number of diseases of the cardio-vascular system.
Most often they are observed at coronaryMost often they are observed at coronary
insufficiency.insufficiency. Arrhythmia registeredArrhythmia registered inin the acutethe acute
period of heart attack of myocardium in 95-100 %period of heart attack of myocardium in 95-100 %
patientspatients..
 In most world countriesIn most world countries sudden cardiac death issudden cardiac death is
about 15 %about 15 % from all cases of «natural» death. Thefrom all cases of «natural» death. The
main reason of sudden death at cardiac pathologymain reason of sudden death at cardiac pathology
in 93 % is arrhythmias.in 93 % is arrhythmias.
Arrhytmias are violation of frequency, rhythm,Arrhytmias are violation of frequency, rhythm,
co-ordination and sequence of heartbeatco-ordination and sequence of heartbeat..

17. Etiology of heart rhythm disorderEtiology of heart rhythm disorder
The rhythm violations arise under the influence of different pathologicalThe rhythm violations arise under the influence of different pathological
agents, which can be divided on such groups:agents, which can be divided on such groups:
 Functional violationsFunctional violations andand influencesinfluences, for example:, for example: violation ofviolation of
vegetative nerves systemvegetative nerves system condition (sympathetic or parasympatheticcondition (sympathetic or parasympathetic
link hyperactivity),link hyperactivity), physical workphysical work,, physical overloadphysical overload,, body temperaturebody temperature
changeschanges,, the increase of intracranium pressurethe increase of intracranium pressure,, respirationrespiration (especially(especially
in children);in children);
 Organic injury of myocardiumOrganic injury of myocardium , for example:, for example: inflammation ofinflammation of
myocardiummyocardium (as the result of infection), the(as the result of infection), the myocardium dystrophymyocardium dystrophy (in(in
the result of hypoxia, ischemia or amiloidosis),the result of hypoxia, ischemia or amiloidosis), necrosis ofnecrosis of
myocardiummyocardium;;
 Influences of toxic substances on the myocardiumInfluences of toxic substances on the myocardium (alcohol,(alcohol,
drugs, big dose adrenalin and noradrenalin, glucocorticoids, bacterialdrugs, big dose adrenalin and noradrenalin, glucocorticoids, bacterial
toxins, phosphororganic substances);toxins, phosphororganic substances);
 Hormone balance disorderHormone balance disorder (hyperthyroidism, hypothyroidism,(hyperthyroidism, hypothyroidism,
hyperfunction of supranephral glands);hyperfunction of supranephral glands);
 Violation of intracellular or extracellular ions balanceViolation of intracellular or extracellular ions balance
(changes of sodium, potassium, calcium, magnesium and chlorine(changes of sodium, potassium, calcium, magnesium and chlorine
concentration);concentration);
 Mechanical influences on the heartMechanical influences on the heart (catheter using for the(catheter using for the
diagnosis and treatment heart diseases, operation on the heart, chestdiagnosis and treatment heart diseases, operation on the heart, chest
trauma).trauma).

18. • Development of arrhythmiasDevelopment of arrhythmias can be related tocan be related to
violations of basic functions of the conductingviolations of basic functions of the conducting
system of heart:system of heart:
1) automatism1) automatism,,
2)2) excitabilityexcitability andand
3)3) conductivity.conductivity.
• Classification of arrhythmias:Classification of arrhythmias:
I. Arrhythmias, related with violations of automatism.I. Arrhythmias, related with violations of automatism.
II. Arrhythmias, related with violations of excitability.II. Arrhythmias, related with violations of excitability.
III. Arrhythmias, related with violations ofIII. Arrhythmias, related with violations of
conductivity.conductivity.
IV. Arrhythmias, related with violations of excitabilityIV. Arrhythmias, related with violations of excitability
and conductivity.and conductivity.

19. Normal Rhythms

20. Arrhythmias, related with violationArrhythmias, related with violation
ofof automatismautomatism of heartof heart
 Distinguish two groups of arrhythmiasDistinguish two groups of arrhythmias, related with, related with violationviolation
of automatism of heart.of automatism of heart.
1)1) Nomotopic arrhythmiasNomotopic arrhythmias -- the generation of impulsesthe generation of impulses, as well, as well
as in a norm,as in a norm, takes place bytakes place by pacemaker cells (P-cells) inpacemaker cells (P-cells) in
sinoatrial [sinus] node, [nodus sinuatrialis]sinoatrial [sinus] node, [nodus sinuatrialis]. To them belong:. To them belong:
 a)a) sinus tachycardiasinus tachycardia is multiplying frequency of cardiacis multiplying frequency of cardiac
reductions;reductions;
 b)b) sinus bradycardiasinus bradycardia is diminishing of frequency of cardiacis diminishing of frequency of cardiac
reductions;reductions;
 c)c) sinus (respiratory) arrhythmiasinus (respiratory) arrhythmia is a change of frequency ofis a change of frequency of
heartbeat in the different phases of respiratory cycleheartbeat in the different phases of respiratory cycle
(become more frequent at inhalation [breath] and(become more frequent at inhalation [breath] and
diminishing is at exhalation [outward breath]).diminishing is at exhalation [outward breath]).

21. Arrhythmias, related withArrhythmias, related with
violation of automatismviolation of automatism

22. Heterotopic ArrhythmiasHeterotopic Arrhythmias
2)2) heterotopic arrhythmiasheterotopic arrhythmias areare a syndrome ofa syndrome of weakness of sinusweakness of sinus
nodenode.. The generation of impulses appears into other structures ofThe generation of impulses appears into other structures of
the conducting system. A syndrome develops as a result ofthe conducting system. A syndrome develops as a result of
diminishing of activity or stopping of activity of sinus node at thediminishing of activity or stopping of activity of sinus node at the
damage of it cells or primary functional violations. The followingsdamage of it cells or primary functional violations. The followings
types of pathological rhythms of heart can develop:types of pathological rhythms of heart can develop:
 a)a) atrium slow rhythmatrium slow rhythm - a driver of rhythm is in the structures of- a driver of rhythm is in the structures of
left atrium, frequency of heartbeatleft atrium, frequency of heartbeat lesser than 70 per 1 minlesser than 70 per 1 min;;
 b)b) atrio-ventricular rhythmatrio-ventricular rhythm - the source of impulses are drivers- the source of impulses are drivers
of rhythm of the II order (overhead, middle or lower part of atrio-of rhythm of the II order (overhead, middle or lower part of atrio-
ventricular node), frequency of heartbeat in dependence on theventricular node), frequency of heartbeat in dependence on the
place of generation of impulsesplace of generation of impulses diminishes from 70 to 40 perdiminishes from 70 to 40 per
minuteminute ;;
 c)c) idioventricular rhythmidioventricular rhythm - the generation of impulses appears in- the generation of impulses appears in
the drivers of rhythm of the III order (His' bundle, atrioventricularthe drivers of rhythm of the III order (His' bundle, atrioventricular
fascicle, fasciculus atrioventricularis and pedunculi of it),fascicle, fasciculus atrioventricularis and pedunculi of it),
frequency of heartbeatfrequency of heartbeat lesser than 40 per minutelesser than 40 per minute..

23. Reason and mechanisms of development ofReason and mechanisms of development of
sinus tachy- and bradycardiasinus tachy- and bradycardia
► Sinus tachycardia and bradycardiaSinus tachycardia and bradycardia relate to therelate to the
groupgroup of nomotopic arrhythmias, connect withof nomotopic arrhythmias, connect with
violations of function of automatismviolations of function of automatism..
► A capacity for automatic formation of impulsesA capacity for automatic formation of impulses
depends on cells, located in the conductingdepends on cells, located in the conducting
system of heart (system of heart (p-cellsp-cells) in which present) in which present
spontaneous slow depolarization of cellularspontaneous slow depolarization of cellular
membrane in the period of diastole.membrane in the period of diastole.
► Frequency of generation of impulses dependsFrequency of generation of impulses depends onon::
a)a) maximal diastolic potential of these cellsmaximal diastolic potential of these cells;;
b)b) level of critical potential on a membranelevel of critical potential on a membrane, after, after
which appearswhich appears potential of actionpotential of action; and; and
c)c) speeds of diastolic depolarization.speeds of diastolic depolarization.

24. Reason and mechanisms of development ofReason and mechanisms of development of
sinus tachy- and bradycardiasinus tachy- and bradycardia
 Increase generating of impulsesIncrease generating of impulses .. Reasons:Reasons:
a) at diminishing of level of maximal diastolic potential of cells of sinus nodea) at diminishing of level of maximal diastolic potential of cells of sinus node
b) at approaching to it of maximum critical potential,b) at approaching to it of maximum critical potential,
c) at multiplying speed of slow diastolic depolarization.c) at multiplying speed of slow diastolic depolarization.
 Such phenomenon is observed:Such phenomenon is observed:
a) under act of the promoted temperature of bodya) under act of the promoted temperature of body
b) stretching areas of sinus node,b) stretching areas of sinus node,
c) under act of mediators of sympathetic system.c) under act of mediators of sympathetic system.
 Opposite,Opposite,
a) diminishing of speed of slow diastolic depolarization,a) diminishing of speed of slow diastolic depolarization,
b) hyperpolarization in a diastole andb) hyperpolarization in a diastole and
c) the decreasing of critical maximum potential, as it is observed at annoying ac) the decreasing of critical maximum potential, as it is observed at annoying a
vagus nerve, are accompanied deceleration of generation of impulses, andvagus nerve, are accompanied deceleration of generation of impulses, and
consequently -consequently -
 The instability [fluctuation, variation] of tone of vagus nerve during the act ofThe instability [fluctuation, variation] of tone of vagus nerve during the act of
breathing predetermine respiratory arrhythmia (become more frequentbreathing predetermine respiratory arrhythmia (become more frequent
palpitation at inhalation, deceleration - at exhalation).palpitation at inhalation, deceleration - at exhalation).
 Children have respiratory arrhythmia in a normChildren have respiratory arrhythmia in a norm , sometimes it also, sometimes it also
observed for adults.observed for adults.
Tachycardia developsTachycardia develops
Bradycardia developsBradycardia develops

25. Arrhythmias, related to violations of excitabilityArrhythmias, related to violations of excitability
The main reason is appearance so-called ectopic hotbed of
excitations which generate premature impulsespremature impulses.
The most widespread arrhythmias of this group are:
a) extrasystole [beat]a) extrasystole [beat] andand
b) paroxysmal [recurrent, reentrant] tachycardia.b) paroxysmal [recurrent, reentrant] tachycardia.
Extrasystole is a type of arrhythmias, which are stipulated
violations of function of excitability which shows up the origin
of premature contraction of heart or only ventricles.
In dependence on localization of hotbed which an premature
impulse goes out from, distinguish the followings types of
extrasystole:
a)a) sinussinus (or nomotopic),(or nomotopic),
b)b) atrialatrial,,
c)c) atrio-ventricularatrio-ventricular andand
d)d) ventricular [ventricular premature beats].ventricular [ventricular premature beats].
As a wave of excitation, which arose up in an unusual place,
spreads in the changed direction, it is reflected on the
structure of the electric field of heart and finds a reflection on
an electrocardiogram.

26. ExtrasystolesExtrasystoles ((ESES))
• When an action potential from a
supraventricular ectopic focus is transmitted
to the ventricles (atrial or nodal extrasystole),
it can disturb their regular (sinus) rhythm
(supraventricular arrhythmia). An atrial ES
can be identified in the ECG by a distorted
(and premature) P wave followed by a normal
QRS complex. If the action potential
originates in the AV node (nodal ES), the
atria are depolarized retrogradely, the P wave
therefore being negative in some leads and
hidden within the QRS complex or following it
(1, blue frame). Because the sinus node is
also often depolarized by a supraventricular
ES, the interval between the R wave of the
ES (= RES) and the next normal R wave is
frequently prolonged by the time of
transmission from ectopic focus to the sinus
node (postextrasystolic pause). The intervals
between R waves are thus: RES–R > R–R
and (R–RES + RES–R) < 2 R–R ( 1 ). An
ectopic stimulus may also occur in a ventricle
(ventricular extrasystole → 2, 3). In this
case the QRS of the ES is distorted. If the
sinus rate is low, the next sinus impulse may
be normally transmitted to the ventricles
(interposed ES; 2). At a higher sinus rate the
next (normal) sinus node action potential may
arrive when the myocardium is still refractory,
so that only the next but one sinus node
impulse becomes effective (compensatory
pause). The R–R intervals are: R–RES
+RES–R = 2 R–R.
Ectopic Origin of Stimulus (1–5)
Abnormal Conduction (5)

27. Sinus extrasystoleSinus extrasystole
• Sinus extrasystole arises up
as a result of premature
excitation part of cells of
sinus node. On ECG:
shortening interval TP.
• As a result shortening of
diastole and diminishing of
filling of ventricles a pulse
wave is diminished too.

28. Atrial extrasystolesAtrial extrasystoles
• Atrial extrasystolesAtrial extrasystoles are
observed at presence of heart
beat of ectopic excitation in the
different areas of atrium and are
characterized:
a) change the form P-waveform P-wave
(reduced, two-phase, negativereduced, two-phase, negative);
b) at the stored complex QRS and
c) some lengthening of diastolic
interval after extrasystole (an
incomplete compensate pauseincomplete compensate pause).

29. Atrio-Atrio-
ventricularventricular
extrasystoleextrasystole
• Atrio-ventricular extrasystole is observed in case of occurring of
additional impulse in atrio-ventricular node.
• The wave of excitation, which goes out from overhead and middle
parts of node, spreads in two directions:
a) into ventricles - as normal
b) into atrium - retrograde direct. Thus:
a) the negativenegative P-waveP-wave can be present before or laybefore or lay on complex QRSon complex QRS;
b) diastole interval after a extrasystole is a little prolonged.
A extrasystole can be accompanied simultaneous beat of atrium and
ventricles.
• At a atrio-ventricular extrasystole which goes out from lower part of
node, there is a compensate pause, the same, as well as at a
ventricular extrasystole and P-wave is negative and situated after
complex QRS.

30. Ventricular extrasystoleVentricular extrasystole
• Ventricular extrasystoleVentricular extrasystole are
characterized presence of a completecomplete
compensate pausecompensate pause after premature
heartbeat and deformation complex
QRS.
• Next beat of ventricles arises up onlyNext beat of ventricles arises up only
after arrival to them of duty normalafter arrival to them of duty normal
impulseimpulse.. That is why duration of a
compensate pause equals duration of
two normal diastolic pauses. However if
reductions of heart are so rare that to the
moment of arrival of duty normal impulse
ventricles have time to go out from the
state of adiphoria, a compensate pause
is absent. Premature heartbeat gets in an
interval between two normal and in this
case called the inserted extrasystole.

31. • 1) Atrial ectopic beatsAtrial ectopic beats appear as early
(premature extrasystoles) and abnormal
P-waves in the ECG; they are usually
followed by normal QRS-complexes.
Following the premature beat there is
often a compensatory interval. A
premature beat in the left ventricle is weak
because of inadequate venous return, but
after the long compensatory interval, the
post-extrasystolic contraction (following a
long venous return period) is strong due
the Starling´s law of the heart. -
Adrenergic b-blockers are sometimes
necessary.
• 2) Ventricular ectopic beatsVentricular ectopic beats
(extrasystoles) are recognized in the ECG
by their wide QRS-complex (above 0.12
s), since they originate in the ventricular
tissue and slowly spread throughout the
two ventricles without passing the Purkinje
system. The ventricular ectopic beat is
recognized by a double R-wave. The
classical tradition of simultaneous cardiac
auscultation and radial artery pulse
palpation eases the diagnosis. Now and
then a pulsation is not felt, and an early
frustraneous beat is heard together with a
prolonged interval. A beat initiated in the
vulnerable period may release lethal
ventricular tachycardia, since the tissue is
no longer refractory.

32. Paroxysmal tachycardiaParoxysmal tachycardia
• Paroxysmal tachycardiaParoxysmal tachycardia is arrhythmia, which is stipulated
violations of function of excitability, which shows up the
origin of group of extrasystoles which fully repress a
physiology rhythm.
• At paroxysmal tachycardia the normal rhythm of heart isnormal rhythm of heart is
suddenly brokensuddenly broken by attack of beats with frequency from 140
to 250 shots per minute.
• Duration of attack can be different - from a few secondsfew seconds to a
few minutesfew minutes. It is suddenly stopped and recommences
normal rhythm.
Paroxysmal supraventrical
tachycardia
Paroxysmal supraventricular tachycardia: note accelerated
rate and narrow QRS complexes.

33. Arrhythmias, related to violation ofArrhythmias, related to violation of
conductivity of impulsesconductivity of impulses
 Select two groups of such arrhythmias:Select two groups of such arrhythmias:
1) Heart block.1) Heart block.
2) Increased conducting of impulses –2) Increased conducting of impulses – WPW-syndromeWPW-syndrome (Wolf-Parkinson-(Wolf-Parkinson-
White block)White block)
 Heart blocksHeart blocks are arrhythmias, conditionedare arrhythmias, conditioned deceleration or completedeceleration or complete
stopped conducting of impulsesstopped conducting of impulses on the conducting system.on the conducting system.
 ReasonsReasons::
a)a) the damage of conductive ways,the damage of conductive ways,
b)b) worsening of other functional descriptionsworsening of other functional descriptions, which is accompanied, which is accompanied
deceleration or complete stopped conducting of impulse.deceleration or complete stopped conducting of impulse.
 Violations of conductivity canViolations of conductivity can arise up:arise up:
a)a) between a sinus node and atriumsbetween a sinus node and atriums
b)b) inwardly atriums,inwardly atriums,
c)c) between atriums and ventricles andbetween atriums and ventricles and
d)d) in one of legs of His' bundle.in one of legs of His' bundle.
 Followings types of blockades select:Followings types of blockades select:
1)1) intraatrialintraatrial;;
2)2) atrio-ventricular;atrio-ventricular;
3)3) intraventricularintraventricular..

34. SA BLOCKSA BLOCK
Rate normal or bradycardia
P wave those present are normal
QRS normal
Conduction normal
Rhythm basic rhythm is regular*

35. Atrio-ventricularAtrio-ventricular
blockblock
 Four typesFour types of atrio-of atrio-
ventricular (AV)-ventricular (AV)-
block. From aboveblock. From above
downwards:downwards:
 First-degree AV-First-degree AV-
block,block,
 Second-degreeSecond-degree
Mobitz I blockMobitz I block
(Wenchebach),(Wenchebach),
 Second-degreeSecond-degree
Mobitz II block,Mobitz II block,
andand
 Complete AV-Complete AV-
block.block.

36. First-Degree
 Long PR interval (>200 msec; one big box)
 Slowed conduction through the AV node
 Characteristics: rate and rhythm are typically normal
Heart Blocks
Second-Degree
Every QRS complex is preceded by a P wave, but not every P wave is
followed by a QRS complex.
 Some impulses are not transmitted through the AV node.
Two types:
 Mobitz type I (Wenckebach) - Progressive prolongation of PR interval until
a ventricular beat is missed and then the cycle begins again. This arrhythmia
will have an unsteady rhythm.

37. Third-Degree (Complete)
Complete dissociation of P waves and QRS complexes
Impulses are not transmitted through the AV node.
Characteristics: steady rhythm (usually) and very slow ventricular HR
(usually);
no consistent PR interval because impulses are not transmitted through the
AV node;
rate for P waves is different than rate for R waves
Mobitz type II:
The PR interval is consistent, i.e.,
It doesn’t lengthen and this separates it from Wenckebach.
The rhythm can be steady or unsteady depending upon block ratio (P to QRS
ratio: 2:1, 3:1, 3:2, etc.).

39. Increase conductingIncrease conducting
of impulsesof impulses
• WPW-syndrome –
characterized the
speed-up
conducting of
impulses from
atriums to the
ventricles, as a
result there is
premature
excitation of the
last, tachycardia
develops, the
interval of PQ
diminishes on an
electrocardiogram.

40. Accessory pathway (Bundle of Kent) between atria and
ventricles
Characteristics:
PR interval; steady rhythm and normal rate (usually);
Slurred upstroke of the R wave (delta wave); widened QRS
complex
The cardiac impulse can travel in retrograde fashion to the
atria over the accessory pathway and initiate a reentrant
tachycardia.
Wolff-Parkinson-White Syndrome

41. Re-entry mechanismRe-entry mechanism
Under normal conditions, anUnder normal conditions, an
electrical impulse is conductedelectrical impulse is conducted
through the heart in an orderly,through the heart in an orderly,
sequential manner. Thesequential manner. The electricalelectrical
impulse then dies out and does notimpulse then dies out and does not
reenter adjacent tissuereenter adjacent tissue becausebecause thatthat
tissue has already been depolarizedtissue has already been depolarized
and is refractory to immediateand is refractory to immediate
stimulationstimulation. However, under certain. However, under certain
abnormal conditions, an impulse canabnormal conditions, an impulse can
reenter an area of myocardium thatreenter an area of myocardium that
was previously depolarized andwas previously depolarized and
depolarize it again. There threedepolarize it again. There three
conditions are the necessary for thisconditions are the necessary for this
mechanism beginning:mechanism beginning:
1 – two conductive ways are the1 – two conductive ways are the
functionally or anatomicallyfunctionally or anatomically
disconnected;disconnected;
2 – some conductive way is2 – some conductive way is
blocked;blocked;
3 – the antegrade conductive way3 – the antegrade conductive way
is blocked, but the retrograde oneis blocked, but the retrograde one
is preserved.is preserved.
So, in that condition impulse (orSo, in that condition impulse (or
impulses) travels numerous throughimpulses) travels numerous through
some area of conductive system andsome area of conductive system and
returns through another pathway toreturns through another pathway to
the reactivated myocardiocytes.the reactivated myocardiocytes.

42. Potassium
 Hyperkalemia:
Increases rate of repolarization, resulting in
sharp-spiked T waves
 Shortened QT interval.
 Hypokalemia:
Decreases rate of repolarization, resulting in
U waves
 Prolonged QT interval.
Calcium
 Hypercalcemia:
Decreases the QT interval
 Hypocalcemia:
Increases the QT interval

43. Excitation in Electrolyte
Disturbances
Hyperkalemia (> 6.5 mmol/L): Hypokalemia (< 2.5 mmol/L):
Hypercalcemia (> 2.75 mmol/L
total calcium)
Hypocalcemia (< 2.25 mmol/L
total calcium)

44. Arrhythmias with violation of functions ofArrhythmias with violation of functions of
excitability and conductivityexcitability and conductivity
1)1) atrial flutteratrial flutter (frequency of(frequency of
atrium beats -atrium beats - 250-400250-400 //
min).min).
2)2) Atrial fibrillationAtrial fibrillation (frequency(frequency
of impulses which arise upof impulses which arise up
in atrium isin atrium is 400-600400-600 / min)./ min).
► Atrial flutterAtrial flutter andand
fibrillation have identicalfibrillation have identical
reasons of developmentreasons of development
and can pass one toand can pass one to
another. So, these twoanother. So, these two
types of violation of rhythmtypes of violation of rhythm
of heart combine into oneof heart combine into one
and called isand called is fibrillationfibrillation..
3)3) ventricle flutterventricle flutter (frequency(frequency
of ventricle beat isof ventricle beat is 150-150-
300300/m)./m).
4)4) FibrillationFibrillation of ventriclesof ventricles
(frequency of impulses in(frequency of impulses in
ventricles isventricles is 300-500300-500 / min)./ min).
► ArrhythmiasArrhythmias which arise up as a result of simultaneous violation of functionswhich arise up as a result of simultaneous violation of functions
ofof excitabilityexcitability andand conductivityconductivity.. To them belong:To them belong:

45. Even when the stimulus
formation in the sinus
node is normal,
abnormal ectopic
excitations can start
from a focus in an
atrium (atrial), the AV
node (nodal), or a
ventricle (ventricular).

47. ECGs (lead II)
showing
abnormal rhythms
A:Respiratory sinus arrhythmia.
B:Sinus arrest with vagal escape.
C:Atrial fibrillation.
D:Premature ventricular complex.
E:Complete atrioventricular block.

48. Self-AssessmentSelf-AssessmentMultiple Choice QuestionsMultiple Choice Questions
 I. Each of the following five statements have True/False options:I. Each of the following five statements have True/False options:
 Stem statement: The ventricular action potential isStem statement: The ventricular action potential is
A.A. initiated by rapid entry of Na+. initiated by rapid entry of Na+.
B.B. characterised by slow Ca2+ -Na+- channels. characterised by slow Ca2+ -Na+- channels.
C.C. characterised by closed K+- channels in phase 3. characterised by closed K+- channels in phase 3.
D.D. dependent upon Ca2+-influx. dependent upon Ca2+-influx.
E.E. independent of the Na+-K+ -pump in phase 4. independent of the Na+-K+ -pump in phase 4.
 II. Each of the following five statements have True/False options:II. Each of the following five statements have True/False options:
A.A. In myocardial cells, as in nerve and skeletal muscle cells, K+ plays a minor role in determiningIn myocardial cells, as in nerve and skeletal muscle cells, K+ plays a minor role in determining
the resting membrane potential.the resting membrane potential.
BB. The impulse propagates from the sinus node via five bundles of internodal syncytial cells through. The impulse propagates from the sinus node via five bundles of internodal syncytial cells through
the left and right atrial wall to the atrioventricular node.the left and right atrial wall to the atrioventricular node.
C.C. The long absolute refractory period of the ventricular cells, covers the whole shortening phaseThe long absolute refractory period of the ventricular cells, covers the whole shortening phase
of the contraction, where all the fast Na+-channels are voltage-inactivated. As a consequence,of the contraction, where all the fast Na+-channels are voltage-inactivated. As a consequence,
no stimulus is sufficient regardless of size.no stimulus is sufficient regardless of size.
D.D. The fast Na+-influx causes phase 0 of atrial- , ventricular- , and Purkinje- action potentials. TheThe fast Na+-influx causes phase 0 of atrial- , ventricular- , and Purkinje- action potentials. The
fast Na+-channels are both voltage- and time-dependent.fast Na+-channels are both voltage- and time-dependent.
E.E. Noradrenaline activates a-adrenergic constrictor receptors in the coronary vessels, whereas Noradrenaline activates a-adrenergic constrictor receptors in the coronary vessels, whereas
adrenaline activates b-adrenergic vasodilatator receptors.adrenaline activates b-adrenergic vasodilatator receptors.
 III.III. The following five statements have True/False options.The following five statements have True/False options.
A.A. WPW-syndrome or Wolf-Parkinson-White block is caused by a short cut through an extraWPW-syndrome or Wolf-Parkinson-White block is caused by a short cut through an extra
conduction pathway from the atria to the ventricles.conduction pathway from the atria to the ventricles.
BB. Atrial fibrillation is more malignant than ventricular fibrillation.. Atrial fibrillation is more malignant than ventricular fibrillation.
C.C. All pacemaker abnormalities arise in the sinus node.All pacemaker abnormalities arise in the sinus node.
DD. Premature beats are also called atrial ectopic beats.. Premature beats are also called atrial ectopic beats.
EE. Only few cardiac arrhythmias can lead to atrial fibrillation and flutter.. Only few cardiac arrhythmias can lead to atrial fibrillation and flutter.
Try to solveTry to solve
the problemsthe problems
beforebefore
looking up thelooking up the
answersanswers

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