CARDIOVASCULAR PHYSIOLOGY
VIVA QUESTIONS AND ANSWERS
DR.C.GANESAN M.D
PROFFESSOR OF MEDICINE
This consists of 94
cardiovascular physiology viva questions, each organized under logical
headings and suitable for MBBS, BDS, BSc Nursing, Physiotherapy, Allied
Health Sciences, and postgraduate physiology viva examinations.
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SECTION I – BLOOD PRESSURE REGULATION
AND CARDIOVASCULAR REFLEXES
1. Bainbridge Reflex
The Bainbridge reflex is a
cardiovascular reflex in which an increase in venous return stretches the right
atrium, causing an increase in heart rate. Stretch receptors located in the
atrial wall transmit impulses through the vagus nerve to the medulla. The
reflex reduces venous congestion by pumping blood more rapidly. It mainly
operates during increased blood volume or intravenous fluid infusion. It
complements the baroreceptor reflex in maintaining circulatory balance.
2. Chemoreceptors Responsible for
Blood Pressure Regulation and Their Stimuli
Peripheral chemoreceptors are located
in the carotid and aortic bodies, while central chemoreceptors are situated in
the medulla. Peripheral chemoreceptors are stimulated by hypoxia, hypercapnia,
and acidosis. Central chemoreceptors mainly respond to increased carbon dioxide
and hydrogen ion concentration in cerebrospinal fluid. Their activation
increases sympathetic activity, heart rate, and blood pressure.
3. Sudden Standing Increases
Diastolic Blood Pressure – Explain
On sudden standing, gravity causes
blood pooling in the lower limbs and transient reduction in venous return. The
resulting fall in arterial pressure stimulates baroreceptors in the carotid
sinus and aortic arch. Sympathetic activation causes arteriolar
vasoconstriction, increasing total peripheral resistance. This preferentially
elevates diastolic blood pressure while maintaining cerebral perfusion.
4. Compensatory Mechanism Activated
When Blood Pressure Falls to 40 mmHg
A severe fall in blood pressure to
about 40 mmHg activates the central nervous system ischemic response. Reduced
cerebral blood flow strongly stimulates the vasomotor center in the medulla.
Massive sympathetic discharge causes intense vasoconstriction and increased
cardiac activity. This emergency mechanism attempts to restore arterial
pressure rapidly. It functions only during life-threatening hypotension.
5. Compensatory Mechanism When Mean
Blood Pressure Rises to 140 mmHg
When mean arterial pressure rises to
approximately 140 mmHg, arterial baroreceptors become strongly stimulated. They
inhibit sympathetic activity while increasing parasympathetic tone. Heart rate,
cardiac contractility, and peripheral resistance decrease. These changes lower
blood pressure toward normal. The baroreceptor reflex provides rapid short-term
regulation.
6. Stress Relaxation and Reverse
Stress Relaxation in Blood Pressure Regulation
Stress relaxation refers to the
gradual relaxation of blood vessel walls after an increase in blood volume or
pressure. This helps accommodate extra blood without a sustained rise in
pressure. Reverse stress relaxation occurs when blood volume decreases, causing
vessels to constrict gradually. These mechanisms contribute to intermediate
regulation of blood pressure. They are also known as delayed compliance
mechanisms.
7. Hypertension, Systolic
Hypertension and White Coat Hypertension
Hypertension is a persistent
elevation of arterial blood pressure above the normal range. Systolic
hypertension refers to isolated elevation of systolic pressure with normal
diastolic pressure, commonly seen in elderly individuals. White coat
hypertension is a temporary rise in blood pressure during clinical examination
due to anxiety. Ambulatory blood pressure monitoring helps confirm the
diagnosis. Early detection prevents cardiovascular complications.
8. Which Pressure Better Indicates
Hypertension – Systolic or Diastolic?
Both systolic and diastolic pressures
are important in assessing hypertension. However, systolic blood pressure is
considered a stronger predictor of cardiovascular events, especially in older
adults. Diastolic pressure is more significant in younger individuals.
Persistent elevation of either requires medical evaluation. Blood pressure
interpretation should always consider the patient's age and risk factors.
9. Labile Hypertension
Labile hypertension refers to
fluctuating blood pressure that varies between normal and elevated levels.
Emotional stress, anxiety, physical activity, and autonomic imbalance commonly
contribute to these fluctuations. Blood pressure may be normal at rest but
elevated during stress. Continuous or ambulatory monitoring is often required
for diagnosis. Some patients may eventually develop sustained hypertension.
10. Hypotension
Hypotension is defined as abnormally
low arterial blood pressure, usually below 90/60 mmHg. It may result from
reduced cardiac output, blood loss, dehydration, or autonomic dysfunction.
Symptoms include dizziness, weakness, blurred vision, and fainting. Severe
hypotension can compromise organ perfusion and lead to shock. Treatment depends
on the underlying cause.
11. Postural (Orthostatic)
Hypotension
Postural hypotension is a significant
fall in blood pressure occurring within three minutes of standing. It results
from inadequate autonomic compensation for gravitational blood pooling.
Patients experience dizziness, lightheadedness, or syncope. Common causes
include dehydration, diabetes, autonomic neuropathy, and certain medications.
Slow positional changes and adequate hydration help reduce symptoms.
SECTION II – PULSE AND EXERCISE
PHYSIOLOGY
12. Difference Between Pulse Pressure
and Pressure Pulse
Pulse pressure is the numerical
difference between systolic and diastolic blood pressure. Pressure pulse refers
to the pressure wave generated by ventricular ejection that travels through
arteries. Pulse pressure reflects stroke volume and arterial compliance.
Pressure pulse can be recorded graphically as an arterial pulse waveform. Both
are valuable indicators of cardiovascular function.
13. Purpose of Exercise Tolerance
Test
The exercise tolerance test evaluates
cardiovascular performance during physical exertion. It helps diagnose coronary
artery disease, exercise-induced arrhythmias, and myocardial ischemia. The test
assesses heart rate, blood pressure, ECG changes, and exercise capacity. It
also evaluates treatment effectiveness and prognosis. It is widely used in
cardiology practice.
14. Cardiac Reserve
Cardiac reserve is the difference
between maximum cardiac output during exercise and cardiac output at rest.
Healthy individuals possess a large cardiac reserve that supports increased
physical activity. Athletes usually have a greater reserve than sedentary
individuals. Reduced cardiac reserve indicates impaired cardiac function. It is
clinically important in heart failure assessment.
15. By Observing Heart Rate, Can You
Predict the Intensity of Exercise or Work Done by a Person?
Heart rate increases proportionally
with exercise intensity because sympathetic activity rises as oxygen demand
increases. A higher heart rate generally indicates greater physical workload.
This relationship is used in exercise stress testing and athletic training.
However, factors such as age, medications, fitness level, and emotional stress
also influence heart rate. Therefore, heart rate provides a useful but not
absolute measure of exercise intensity.
16. Where Do You Find Physiological
Bradycardia?
Physiological bradycardia is commonly
seen in healthy athletes, during deep sleep, and in individuals with high vagal
tone. Regular endurance training improves cardiac efficiency, allowing the
heart to pump more blood with fewer beats. Resting heart rates below 60 beats
per minute may be normal in these individuals. It is usually asymptomatic and
does not require treatment. Physiological bradycardia differs from pathological
bradycardia associated with heart disease.
17. What is Pulse Deficit?
Pulse deficit is the difference
between the heart rate heard at the apex of the heart and the pulse rate felt
at the radial artery. It occurs when some ventricular contractions fail to
produce an effective peripheral pulse. This is commonly seen in atrial
fibrillation and other arrhythmias. Simultaneous auscultation of the apex and
palpation of the radial pulse are required for its measurement. A significant
pulse deficit indicates ineffective cardiac output.
18. What is Pulse? How Can You Record
It?
The arterial pulse is the rhythmic
expansion and recoil of an artery produced by left ventricular systole. It
reflects the pressure wave travelling through the arterial system rather than
the actual movement of blood. Pulse is commonly palpated at the radial artery
and may also be recorded using a sphygmograph or arterial pressure transducer.
Pulse assessment includes rate, rhythm, volume, character, and symmetry. It
provides valuable information about cardiovascular function.
19. Name the Waves of Normal Arterial
Pulse Tracing. What Are Their Physiological Basis?
A normal arterial pulse tracing
consists of the percussion wave, tidal wave, dicrotic notch, and dicrotic wave.
The percussion wave represents rapid ventricular ejection. The tidal wave
results from reflected pressure waves from peripheral arteries. The dicrotic notch
is produced by closure of the aortic valve, while the dicrotic wave follows due
to elastic recoil of the arterial wall. These waves help evaluate cardiac and
vascular function.
20. Can You Indicate the Systolic and
Diastolic Phases of the Ventricle on the Arterial Pulse Tracing?
The ascending limb and peak of the
arterial pulse correspond to ventricular systole during rapid blood ejection
into the aorta. The descending limb represents ventricular relaxation and
diastole. The dicrotic notch marks closure of the aortic valve, indicating the
end of systole. The dicrotic wave occurs during early diastole due to elastic
recoil. Thus, arterial pulse tracing reflects the phases of the cardiac cycle.
21. What is Dicrotic Pulse?
A dicrotic pulse is an arterial pulse
with two palpable peaks during one cardiac cycle. The second wave occurs during
diastole because of an exaggerated dicrotic wave. It is commonly observed in
low cardiac output states such as severe heart failure, typhoid fever, and
septic shock. It indicates reduced arterial pressure and increased peripheral
vasodilation. Recognition of this pulse assists in clinical diagnosis.
22. What is Plateau Pulse?
Plateau pulse, also called pulsus
tardus, is a pulse with a slow-rising and prolonged systolic peak. It is
typically associated with severe aortic stenosis. Obstruction to left
ventricular outflow delays ventricular ejection into the aorta. The pulse feels
weak and sustained during palpation. It is an important clinical sign of left
ventricular outflow obstruction.
23. What is Anacrotic Pulse?
An anacrotic pulse is a slow-rising
pulse that contains a notch on the ascending limb of the pulse wave. It is most
commonly found in severe aortic stenosis. The obstruction delays ventricular
ejection, producing a characteristic waveform. It is best demonstrated on
arterial pulse tracing rather than by palpation alone. It reflects severe
obstruction of the aortic valve.
24. What Do You Mean by Pulsus
Alternans and Pulsus Paradoxus?
Pulsus alternans is a regular pulse
with alternating strong and weak beats despite a normal rhythm, indicating
severe left ventricular dysfunction. Pulsus paradoxus is an exaggerated fall in
systolic blood pressure of more than 10 mmHg during inspiration. It occurs in
cardiac tamponade, severe asthma, and constrictive pericarditis. Both are
important clinical indicators of serious cardiac disease. Careful pulse
examination helps identify these abnormalities.
25. What is Water Hammer Pulse?
Water hammer pulse, also called Corrigan's
pulse, is a rapidly rising and rapidly collapsing arterial pulse. It is
characteristic of aortic regurgitation due to increased stroke volume followed
by rapid diastolic runoff. The pulse is forceful and best appreciated by
elevating the patient's arm. It may also occur in patent ductus arteriosus and
hyperdynamic circulatory states. It indicates a widened pulse pressure.
26. How Does Jugular Venous Pulse
Recording Give an Idea About Right Atrial Pressure?
The internal jugular vein
communicates directly with the right atrium without intervening valves.
Therefore, pressure changes in the right atrium are transmitted to the jugular
vein. Observation of jugular venous pulse provides an indirect assessment of
right atrial pressure and central venous pressure. Elevated jugular venous
pressure suggests right heart failure or fluid overload. It is an important
bedside clinical examination.
27. Name the Waves of Jugular Venous
Pulse and the Causes of Their Onset.
The jugular venous pulse consists of
the a wave, c wave, x descent, v wave, and y descent. The a wave is
produced by right atrial contraction. The c wave results from bulging of the
tricuspid valve during ventricular contraction. The x descent represents atrial
relaxation, the v wave reflects venous filling of the right atrium, and the y
descent indicates rapid ventricular filling after tricuspid valve opening.
These waves help assess right heart function.
28. Define ECG.
Electrocardiography (ECG) is the
graphic recording of the electrical activity generated by the heart during each
cardiac cycle. Electrodes placed on the body surface detect electrical
potentials produced by depolarization and repolarization. ECG is a simple,
non-invasive, and widely used diagnostic investigation. It helps evaluate heart
rhythm, conduction abnormalities, myocardial ischemia, and chamber enlargement.
It is an essential tool in clinical cardiology.
29. Enumerate the Clinical
Significance of ECG.
The ECG helps diagnose cardiac
arrhythmias, myocardial infarction, myocardial ischemia, electrolyte
disturbances, and conduction defects. It also detects chamber enlargement,
ventricular hypertrophy, and the effects of drugs such as digoxin. ECG is
useful for monitoring patients during surgery and intensive care. It provides
valuable prognostic information in cardiovascular disease. It remains one of
the most commonly performed cardiac investigations.
30. What Does the P Wave Represent?
What Does It Signify?
The P wave represents atrial
depolarization initiated by the sinoatrial node. It indicates the spread of
electrical impulses through both atria before atrial contraction. Normally, the
P wave is smooth, rounded, and lasts less than 0.12 seconds. Abnormal P waves
suggest atrial enlargement or ectopic atrial rhythms. It is the first
electrical event recorded in a normal ECG.
31. What Do the QRS Complex and QRST
Complex Represent? What Is the Duration of the Ventricular Complex?
The QRS complex represents
ventricular depolarization, which initiates ventricular contraction. The QRST
complex includes ventricular depolarization followed by ventricular
repolarization. Normally, the QRS complex lasts 0.06–0.10 seconds and
should not exceed 0.12 seconds. A prolonged QRS duration suggests
intraventricular conduction delay or bundle branch block. The ventricular
complex is the most prominent part of the ECG.
32. What Do the Q and R-S Waves
Indicate?
The Q wave represents
initial depolarization of the interventricular septum from left to right.
The R wave reflects depolarization of the major ventricular
muscle mass. The S wave represents the final depolarization of
the basal regions of the ventricles. Together, these waves form the QRS complex
indicating ventricular activation. Abnormal Q waves may suggest previous
myocardial infarction.
33. What Is the Significance of the T
Wave?
The T wave represents
ventricular repolarization after ventricular contraction. It is normally
upright in most ECG leads except aVR. Changes in the T wave may occur in
myocardial ischemia, electrolyte disturbances, or ventricular hypertrophy. Tall
T waves are often seen in hyperkalemia, while inverted T waves suggest ischemia
or infarction. Thus, the T wave provides important information about
ventricular recovery.
34. What Does the PR Interval
Represent? What Is Its Significance?
The PR interval extends
from the beginning of the P wave to the beginning of the QRS complex. It
represents conduction of the electrical impulse from the atria through the AV
node, Bundle of His, and Purkinje system to the ventricles. The normal duration
is 0.12–0.20 seconds. A prolonged PR interval indicates
first-degree AV block, whereas a shortened interval may occur in pre-excitation
syndromes. It reflects AV conduction time.
35. What Is the TP Interval and What
Is Its Significance?
The TP interval is
the period between the end of the T wave and the beginning of the next P wave.
It represents electrical diastole when both atria and ventricles are
electrically inactive. This interval serves as the true isoelectric baseline of
the ECG. It is useful for identifying ST-segment deviations accurately. The TP
interval reflects complete cardiac relaxation.
36. What Is the QT Interval and What
Does It Represent?
The QT interval extends
from the beginning of the QRS complex to the end of the T wave. It represents
the total duration of ventricular depolarization and repolarization. The QT
interval varies with heart rate and is corrected as QTc for clinical
interpretation. Prolongation increases the risk of ventricular arrhythmias such
as Torsades de Pointes. It is an important indicator of ventricular electrical
activity.
37. What Is the ST Interval? What
Does It Represent?
The ST interval extends
from the end of the S wave to the end of the T wave. It includes both the ST
segment and the T wave. This interval represents the period of ventricular
repolarization. Abnormal changes may occur in myocardial ischemia, infarction,
and electrolyte disturbances. It provides information about ventricular
recovery after depolarization.
38. What Is the ST Segment? What Is
Its Significance?
The ST segment extends
from the end of the QRS complex (J point) to the beginning of the T wave. It
represents the period when the ventricles are completely depolarized. Normally,
it lies on the isoelectric baseline. ST elevation suggests acute myocardial
injury, while ST depression indicates myocardial ischemia. Careful assessment
of the ST segment is essential in diagnosing acute coronary syndromes.
39. Define Lead.
A lead is a
recording of the electrical potential difference between two electrodes or
between one exploring electrode and a reference electrode. It provides a
specific view of the heart's electrical activity from different directions.
Multiple leads allow comprehensive assessment of cardiac electrical events. ECG
interpretation depends on analysing all standard leads together. Each lead
records the same cardiac activity from a different angle.
40. Classify the ECG Leads.
ECG leads are classified into bipolar
limb leads, augmented unipolar limb leads, and unipolar
chest (precordial) leads. Bipolar leads include Leads I, II, and III.
Augmented limb leads are aVR, aVL, and aVF. Chest leads include V1 to V6.
Together, these twelve leads provide a complete electrical map of the heart.
41. Why Is a Unipolar Lead So Called?
A unipolar lead records
electrical activity using one exploring positive electrode and one electrically
neutral reference electrode. The reference electrode has nearly zero electrical
potential because it is formed by combining signals from other limb electrodes.
Therefore, only one active electrode contributes significantly to the
recording. Examples include augmented limb leads and chest leads. These leads
provide localized information about cardiac electrical activity.
42. What Do You Mean by Rule of Thumb
in ECG?
The Rule of Thumb is
a simple method used for rapid ECG interpretation. It includes checking the
heart rate, rhythm, cardiac axis, P waves, PR interval, QRS complex, ST
segment, T wave, and QT interval in a systematic manner. Following this
sequence minimizes diagnostic errors. It is especially useful for students and
beginners learning ECG interpretation. A structured approach improves clinical
accuracy.
43. What Is an Augmented Limb Lead?
Why Is It So Called?
Augmented limb leads are aVR,
aVL, and aVF, which are unipolar limb leads with increased voltage. The
electrical signal is amplified by approximately 50%, making the recorded waves
larger and easier to interpret. The term "augmented" refers to this
increase in voltage. These leads provide frontal plane views of the heart. They
complement the standard bipolar limb leads.
44. What Do Unipolar Chest Leads
Represent?
The unipolar chest leads
(V1–V6) record the electrical activity of the heart in the horizontal
plane. Each lead is placed at a specific position on the chest wall. They
provide detailed information about the anterior, septal, lateral, and posterior
regions of the ventricles. Chest leads are particularly useful in detecting
myocardial infarction and ventricular hypertrophy. They complement the frontal
plane limb leads.
45. What Do You Mean by
Dextrocardiogram?
A dextrocardiogram is
an ECG recorded in a patient with dextrocardia, where the heart lies
on the right side of the chest. Standard ECG leads show characteristic
abnormalities such as inverted complexes in Lead I and reversed chest lead
progression. Right-sided chest leads help obtain a normal pattern. Recognition
of dextrocardia prevents misinterpretation of the ECG. It may occur as an
isolated anomaly or with situs inversus.
46. What Is Levocardiogram?
A levocardiogram refers
to the normal ECG pattern recorded when the heart is situated on the left side
of the thorax. The electrical axis is directed predominantly toward the left
ventricle because it forms the major muscle mass of the heart. The chest leads
show normal R-wave progression from V1 to V6. This pattern is seen in the
majority of healthy individuals. It serves as the standard ECG against which
abnormalities are compared.
47. What Do You Mean by Einthoven's
Triangle?
Einthoven's triangle is an imaginary equilateral
triangle formed by the right arm, left arm, and left leg electrodes. The heart
lies approximately at the center of this triangle. The three bipolar limb leads
(I, II, and III) are derived from its sides. It provides the basis for
recording electrical activity in the frontal plane. The concept is fundamental
to understanding electrocardiography.
48. What Is Einthoven's Law?
Einthoven's law states that the electrical
potential recorded in Lead II is equal to the sum of the potentials recorded in
Leads I and III. Mathematically, Lead II = Lead I + Lead III. This
relationship helps verify the accuracy of ECG recordings. It also forms the
basis for calculating the electrical axis of the heart. The law applies to
standard bipolar limb leads.
49. What Is the J Point? What Is Its
Significance?
The J point is the
junction between the end of the QRS complex and the beginning of the ST
segment. It marks the completion of ventricular depolarization and the onset of
ventricular repolarization. The J point serves as the reference for measuring
ST-segment elevation or depression. Abnormal elevation may indicate acute
myocardial infarction or pericarditis. It is an important landmark in ECG
interpretation.
50. What Is a Vector?
A vector is a
quantity that has both magnitude and direction. In electrocardiography, it
represents the direction and strength of electrical impulses travelling through
the heart. The resultant cardiac vector changes continuously during
depolarization and repolarization. ECG leads record the projection of these
vectors from different angles. Vector analysis helps determine the electrical
axis and diagnose conduction abnormalities.
51. What Do You Know About the U Wave
in ECG?
The U wave is a
small positive wave that sometimes follows the T wave on the ECG. It is thought
to represent delayed repolarization of the Purkinje fibres or papillary
muscles. Normally, the U wave is small and often absent. Prominent U waves are
commonly seen in hypokalemia and bradycardia. Inverted U waves may indicate
myocardial ischemia or hypertension.
52. What Do You Mean by Left and
Right Axis Deviation? How Can They Be Assessed from ECG?
The electrical axis represents
the average direction of ventricular depolarization. Left axis
deviation usually ranges from −30° to −90°, whereas right
axis deviation ranges from +90° to +180°. They are
assessed by examining the polarity of the QRS complexes in Leads I and aVF.
Left axis deviation is seen in left ventricular hypertrophy and left anterior
fascicular block, while right axis deviation occurs in right ventricular
hypertrophy and pulmonary disease. Axis determination is an important part of
ECG interpretation.
53. What Are the Physiological Left
or Right Axis Deviations? What Is the Clinical Significance of the Electrical
Axis of the Heart?
Physiological left axis deviation may
occur in obesity, pregnancy, and expiration, whereas physiological right axis
deviation is common in children, tall individuals, and during deep inspiration.
The electrical axis reflects the direction of ventricular depolarization.
Abnormal axis deviation suggests ventricular hypertrophy, conduction defects,
or myocardial infarction. Determination of the axis assists in diagnosing many
cardiac disorders. It should always be interpreted along with the clinical
findings.
54. What Is the Difference Between
First-Degree and Second-Degree Heart Block?
In first-degree heart block,
all atrial impulses reach the ventricles, but conduction through the AV node is
delayed, producing a prolonged PR interval. In second-degree heart
block, some atrial impulses fail to conduct to the ventricles, resulting in
dropped QRS complexes. First-degree block is usually asymptomatic and benign.
Second-degree block may cause dizziness or syncope and can progress to complete
heart block. ECG is essential for differentiating these conditions.
55. What Do You Mean by Wenckebach
Phenomenon?
The Wenckebach phenomenon,
also called Mobitz Type I second-degree AV block, is characterized
by progressive prolongation of the PR interval until a ventricular beat is
dropped. After the missed beat, the cycle repeats. It usually results from delayed
conduction within the AV node. This condition is often benign and may occur in
healthy individuals with increased vagal tone. Symptomatic cases may require
medical evaluation.
56. What Is Third-Degree Heart Block?
What Do You Mean by Idioventricular Rhythm?
Third-degree heart block, or complete heart block, occurs
when no atrial impulses reach the ventricles. The atria and ventricles beat
independently due to complete AV dissociation. Ventricular contraction is
maintained by a slow escape pacemaker, producing an idioventricular
rhythm. Patients commonly present with severe bradycardia, dizziness, or
syncope. Permanent pacemaker implantation is usually required.
57. What Is the Difference Between
Flutter and Fibrillation?
Flutter is a rapid but regular rhythm
caused by organized electrical activity, whereas fibrillation is
rapid, irregular, and disorganized electrical activity. In atrial flutter,
atrial rates are approximately 250–350 beats per minute, producing
characteristic saw-tooth waves. Atrial fibrillation causes an irregularly
irregular pulse with absent P waves. Ventricular fibrillation results in
complete loss of effective cardiac output and is a medical emergency.
Fibrillation is generally more serious than flutter.
58. What Are the Clinical ECG
Findings During Myocardial Infarction?
Acute myocardial infarction produces
characteristic ECG changes that evolve with time. Early findings include
hyperacute T waves followed by ST-segment elevation in
affected leads. Later, pathological Q waves develop due to
myocardial necrosis. T-wave inversion appears during the healing phase. Serial
ECG recordings help determine the location, severity, and progression of
myocardial infarction.
59. What Do You Mean by Stokes–Adams
Syndrome?
Stokes–Adams syndrome is a sudden episode of syncope
caused by transient cessation of cardiac output due to complete heart block or
severe bradyarrhythmia. The brain receives inadequate blood flow, resulting in
brief loss of consciousness. Recovery usually occurs spontaneously when
ventricular escape rhythm resumes. Patients may experience repeated attacks and
are at risk of sudden death. Permanent pacemaker therapy is the treatment of
choice.
60. What Are the ECG Changes During
Bundle Branch Block? What Changes Occur in Heart Sound Production?
A bundle branch block (BBB) delays
ventricular depolarization on the affected side, resulting in a QRS
duration greater than 0.12 seconds. Right bundle branch block shows
an RSR′ pattern in V1, whereas left bundle branch block produces
broad, notched R waves in lateral leads. Ventricular contraction becomes
asynchronous. This delay causes wide splitting of the second heart
sound, especially in right bundle branch block. BBB is commonly associated
with structural heart disease.
61. What Do You Mean by Extrasystole?
An extrasystole is a
premature heartbeat that occurs before the next expected normal cardiac beat.
It may arise from the atria, atrioventricular junction, or ventricles. Patients
often experience palpitations followed by a compensatory pause. Extrasystoles
may occur in healthy individuals or in association with electrolyte imbalance,
myocardial ischemia, or heart disease. Occasional extrasystoles are usually
benign, whereas frequent ones require further evaluation.
62. What Types of ECG Changes Take
Place in Atrial Flutter and Atrial Fibrillation?
In atrial flutter, the
ECG shows regular saw-tooth flutter (F) waves with atrial
rates of about 250–350 beats per minute. Ventricular rhythm may be
regular or variable depending on AV conduction. In atrial fibrillation,
there are no distinct P waves, and irregular fibrillation (f) waves
are present. The ventricular rhythm becomes irregularly irregular.
These ECG findings help distinguish the two common supraventricular arrhythmias.
63. How Does the ECG Change with Time
After Myocardial Infarction?
The ECG changes in myocardial
infarction occur in a predictable sequence. Initially, hyperacute T
waves appear, followed by ST-segment elevation indicating
acute myocardial injury. Within hours to days, pathological Q waves develop
due to myocardial necrosis. Later, T-wave inversion appears
during the healing phase, while ST segments gradually return to baseline.
Serial ECG recordings are valuable for diagnosis, monitoring, and prognosis.
64. What Do You Mean by Mean
Circulatory Filling Pressure and Mean Systemic Filling Pressure?
Mean circulatory filling pressure
(MCFP) is the
uniform pressure throughout the entire circulation when the heart stops and
blood flow ceases. Mean systemic filling pressure (MSFP) refers
to the pressure within the systemic circulation under the same conditions,
excluding the pulmonary circulation. These pressures depend mainly on blood
volume and venous tone. They determine venous return to the heart. Increased
MSFP enhances cardiac filling and cardiac output.
65. Name Different Types of Blood
Vessels in the Vascular System with Examples.
The vascular system consists of elastic
arteries, muscular arteries, arterioles, capillaries, venules, and veins.
Elastic arteries, such as the aorta, conduct blood from the heart.
Muscular arteries distribute blood to organs, while arterioles regulate
vascular resistance. Capillaries are the principal sites of exchange between
blood and tissues. Veins and venules return blood to the heart and serve as
capacitance vessels.
66. Blood Flow to Different Organs
Can Be Regulated by Small Changes in Arterial Calibre. How Is This Possible?
According to Poiseuille's law,
blood flow is directly proportional to the fourth power of the vessel
radius. Therefore, even a small increase in arterial radius greatly
increases blood flow, while a slight decrease markedly reduces flow. Arterioles
possess abundant smooth muscle that allows rapid changes in diameter. This
mechanism enables precise regulation of blood supply to individual organs. It
plays a major role in controlling peripheral resistance and arterial pressure.
67. What Do You Mean by Critical
Closing Pressure?
Critical closing pressure is the arterial pressure below
which a blood vessel collapses and blood flow stops despite the presence of a
pressure gradient. It depends on vascular smooth muscle tone and external
tissue pressure. Increased sympathetic activity raises the critical closing
pressure by causing vasoconstriction. This mechanism helps regulate tissue
perfusion during circulatory stress. It becomes important in shock and severe
hypotension.
68. State Laplace's Law. What Is Its
Functional Significance?
Laplace's law states that wall
tension is directly proportional to the product of pressure and radius and
inversely proportional to wall thickness. In blood vessels, increased
radius increases wall tension, predisposing to aneurysm formation. In the
heart, ventricular dilation increases wall stress and myocardial oxygen demand.
Thickened ventricular walls reduce wall tension in hypertrophy. Laplace's law
explains many cardiovascular adaptations and pathological conditions.
69. What Is Axon Reflex?
The axon reflex is a
local reflex that occurs without involving the central nervous system. When the
skin is stimulated, impulses travel along sensory nerve branches and return
through collateral branches to release vasodilator substances. This produces
local vasodilatation around the stimulated area. The axon reflex contributes to
the flare component of the triple response. It is an important example of
peripheral neural regulation.
70. What Do You Mean by Cold Blue
Skin and Warm Red Skin?
Cold blue skin results from reduced blood flow
due to vasoconstriction, causing increased extraction of oxygen and
accumulation of deoxygenated hemoglobin. It is commonly seen in shock, heart
failure, and peripheral vascular disease. Warm red skin occurs
due to vasodilatation and increased blood flow, as seen in fever, inflammation,
and septic shock. Skin colour provides useful information about peripheral
circulation. Careful examination aids clinical assessment.
71. What Is Triple Response?
The triple response is
the characteristic skin reaction produced by a firm stroke with a blunt object.
It consists of a red reaction, flare, and wheal.
The response is mediated by capillary dilation, axon reflex, and increased
capillary permeability due to histamine release. It demonstrates local vascular
and neural responses in the skin. Sir Thomas Lewis first described this
physiological phenomenon.
72. What Is the Physiological Basis
of Red Reaction, Flare, and Wheal?
The red reaction results
from direct dilatation of capillaries at the site of injury. The flare is
caused by arteriolar vasodilatation mediated through the axon reflex. The wheal develops
because histamine increases capillary permeability, allowing plasma to
accumulate in the tissues. Together, these three responses constitute the
triple response of Lewis. They demonstrate the interaction between nerves and
blood vessels.
73. What Is White Reaction?
The white reaction is
a transient pale line that appears immediately after light stroking of the
skin. It results from temporary constriction of small cutaneous blood vessels
due to mechanical stimulation. The reaction lasts only a few seconds before the
red reaction develops. It is more evident in individuals with increased
sympathetic tone. The white reaction represents an initial vasoconstrictor
response.
74. What Is the Average Total
Peripheral Resistance at Rest?
Total peripheral resistance (TPR) is the resistance offered by
the systemic circulation to blood flow. In a healthy adult at rest, TPR is
approximately 18–20 mmHg per litre per minute or about 900–1400
dynes·sec·cm⁻⁵. Arterioles contribute the greatest proportion of peripheral
resistance. TPR is influenced by vessel diameter, blood viscosity, and vessel
length. It plays a major role in regulating arterial blood pressure.
75. On What Factors Does Peripheral
Resistance Depend?
Peripheral resistance depends mainly
on arteriolar diameter, which is the most important determinant. It
is also influenced by blood viscosity, vessel length,
and the arrangement of blood vessels. Sympathetic stimulation, circulating
hormones, and local metabolic factors regulate vascular tone. According to
Poiseuille's law, small changes in vessel radius produce large changes in
resistance. Peripheral resistance is a major determinant of arterial blood
pressure.
76. Define Poiseuille's Law.
Poiseuille's law states that blood flow through
a cylindrical vessel is directly proportional to the pressure difference and
the fourth power of the vessel radius, and inversely proportional to blood
viscosity and vessel length. Thus, even a small increase in vessel radius
markedly increases blood flow. Arterioles are the main resistance vessels
because they can alter their diameter rapidly. This law explains the regulation
of tissue perfusion and peripheral resistance. It is fundamental to
cardiovascular physiology.
77. What Is Circulation Time? Give
the Value of Total Circulation Time.
Circulation time is the time taken for blood to
complete one full circuit from the heart through the systemic and pulmonary
circulations back to the heart. In a healthy adult at rest, the total
circulation time is approximately one minute. The arm-to-tongue circulation
time is about 15–20 seconds, while the arm-to-lung circulation time
is about 6–8 seconds. Circulation time depends on cardiac output
and vascular resistance. It is prolonged in heart failure and circulatory
shock.
78. Coronary Blood Flow Fluctuates
with Each Phase of the Cardiac Cycle – Explain.
Coronary blood flow varies throughout
the cardiac cycle because contraction of the myocardium compresses the coronary
vessels. During ventricular systole, especially in the left
ventricle, blood flow decreases markedly due to vessel compression.
During diastole, myocardial relaxation allows maximal coronary
perfusion. Therefore, the left coronary artery receives most of its blood
during diastole. Adequate diastolic pressure is essential for myocardial oxygen
supply.
79. Why Is the Subendocardial Portion
of the Left Ventricle More Prone to Myocardial Infarction?
The subendocardial region of
the left ventricle is subjected to the highest intramural pressure during
systole, compressing its blood vessels. It is the last region to receive blood
during diastole and has the greatest oxygen demand. Any reduction in coronary
perfusion first affects this area. Consequently, it is particularly vulnerable
to ischemia and infarction. This explains the frequent occurrence of
subendocardial myocardial infarction.
80. What Is the Normal Time Taken for
Coronary Circulation?
Blood passes through the coronary
circulation in approximately 7–10 seconds under normal resting
conditions. Coronary circulation provides oxygen and nutrients to the
myocardium while removing metabolic waste products. The duration depends on
cardiac output, coronary vascular resistance, and heart rate. Coronary blood
flow increases several-fold during exercise to meet increased metabolic
demands. Efficient coronary circulation is essential for normal cardiac
function.
81. What Are the Factors on Which
Coronary Blood Flow Depends?
Coronary blood flow depends mainly
on coronary perfusion pressure, duration of diastole,
and coronary vascular resistance. Local metabolic factors such
as adenosine, nitric oxide, and reduced oxygen tension
cause coronary vasodilatation. Heart rate, myocardial oxygen demand, and autonomic
nervous activity also influence coronary flow. Coronary artery obstruction
significantly reduces myocardial perfusion. These factors ensure that
myocardial oxygen supply matches metabolic demand.
82. What Is the Normal Pulmonary
Blood Flow Rate?
The normal pulmonary blood
flow is approximately 5 litres per minute, which is equal
to the cardiac output in a healthy adult at rest. The pulmonary circulation is
a low-pressure, low-resistance vascular system. It facilitates efficient gas
exchange between blood and alveoli. Pulmonary blood flow increases during
exercise in proportion to cardiac output. Proper pulmonary perfusion is
essential for oxygenation of blood.
83. What Is the Normal Blood Flow
Rate in the Liver?
The liver receives
approximately 1.2–1.5 litres of blood per minute, representing
about 25% of resting cardiac output. About 75% of
hepatic blood comes through the portal vein, while the
remaining 25% is supplied by the hepatic artery.
This dual blood supply supports metabolism, detoxification, and nutrient
processing. Hepatic blood flow is influenced by portal venous pressure and
cardiac output. It is one of the highest organ blood flows in the body.
84. What Is the Normal Coronary Blood
Flow?
Normal coronary blood flow is
approximately 225–250 mL per minute, accounting for about 4–5%
of resting cardiac output. The myocardium extracts nearly 70–80% of
the oxygen delivered by coronary blood. During exercise, coronary blood flow
may increase four to five times to meet increased metabolic demand.
Most left ventricular perfusion occurs during diastole. Adequate coronary flow
is essential for maintaining myocardial function.
85. Give the Normal Value of Cerebral
Blood Flow.
Normal cerebral blood flow is
approximately 750 mL per minute, representing about 15% of
resting cardiac output. It corresponds to nearly 50 mL per 100 g of
brain tissue per minute. Cerebral blood flow is maintained by
autoregulation despite moderate changes in blood pressure. Carbon dioxide is a
major regulator of cerebral vascular tone. Continuous cerebral perfusion is
vital for normal brain function.
86. Define Shock. Classify It.
Shock is a state of acute circulatory
failure in which tissue perfusion is inadequate to meet metabolic needs,
leading to cellular hypoxia and organ dysfunction. It is classified into hypovolemic, cardiogenic, distributive
(septic, anaphylactic, neurogenic), and obstructive shock.
Early recognition is essential to prevent irreversible organ damage. Clinical
features include hypotension, tachycardia, altered mental status, and reduced
urine output. Prompt treatment improves survival.
87. What Do You Mean by Cold Shock?
Cold shock is characterized by reduced
cardiac output, intense peripheral vasoconstriction, and cold, clammy
extremities. It commonly occurs in hypovolemic and cardiogenic
shock. Sympathetic activation diverts blood to vital organs at the expense
of skin perfusion. Patients present with hypotension, tachycardia, weak pulse,
and delayed capillary refill. Immediate fluid resuscitation or treatment of the
underlying cause is required.
88. What Is Warm Shock?
Warm shock is characterized by peripheral
vasodilatation resulting in warm, flushed skin despite hypotension. It is
typically seen in the early stages of septic shock and occasionally
in anaphylactic shock. Systemic vascular resistance decreases markedly while
cardiac output may initially increase. Patients have warm extremities, bounding
pulses, and low blood pressure. Early recognition and prompt management are
essential.
89. What Is Congestive Shock?
Congestive shock refers to circulatory failure
associated with severe venous congestion due to impaired cardiac pumping,
particularly in advanced heart failure. Blood accumulates in the venous system,
causing elevated venous pressure and tissue edema. Pulmonary congestion may
also develop, leading to breathlessness. Cardiac output remains insufficient
despite increased filling pressures. Treatment focuses on improving cardiac
function and relieving congestion.
90. What Are the Symptoms of Left
Ventricular Failure?
Left ventricular failure causes
symptoms due to pulmonary congestion and reduced systemic perfusion. Patients
commonly experience breathlessness, orthopnea, paroxysmal
nocturnal dyspnea, fatigue, and reduced exercise tolerance.
Persistent cough with frothy sputum may occur in pulmonary edema. Severe cases
can lead to acute respiratory distress. Early treatment improves symptoms and
prognosis.
91. What Are the Signs and Symptoms
of Right Ventricular Failure?
Right ventricular failure leads to
systemic venous congestion. Clinical features include raised jugular
venous pressure, dependent pitting edema, hepatomegaly, ascites,
and ankle swelling. Patients may complain of abdominal discomfort,
fatigue, and weight gain due to fluid retention. Pulmonary symptoms are usually
less prominent than in left-sided failure. Right ventricular failure commonly
develops secondary to left ventricular failure or pulmonary hypertension.
92. What Are the Common Causes of
Left Ventricular Failure?
The common causes of left ventricular
failure include systemic hypertension, coronary artery
disease, myocardial infarction, aortic valve disease, mitral
valve disease, and cardiomyopathy. Persistent pressure or
volume overload impairs left ventricular function. Arrhythmias and congenital
heart diseases may also contribute. Progressive ventricular dysfunction results
in pulmonary congestion and reduced cardiac output. Identifying the underlying
cause guides treatment.
93. How Do You Differentiate Left and
Right Cardiac Failure Broadly on the Basis of Edema?
In left ventricular failure,
edema primarily develops in the lungs, producing pulmonary edema
with breathlessness and crepitations. In right ventricular failure,
edema occurs mainly in the systemic circulation, causing ankle
swelling, hepatomegaly, ascites, and raised jugular venous pressure. Pulmonary
edema is uncommon in isolated right heart failure. Thus, the site of fluid
accumulation distinguishes the two conditions clinically. Both may coexist in
advanced congestive heart failure.
94. Enumerate Some of the Effects of
Severe Hemorrhage.
Severe hemorrhage causes a rapid
reduction in circulating blood volume, leading to decreased venous return,
reduced cardiac output, and hypotension. Compensatory responses include
tachycardia, peripheral vasoconstriction, activation of the sympathetic nervous
system, and stimulation of the renin–angiotensin–aldosterone system. If
untreated, tissue hypoxia progresses to metabolic acidosis, shock, and multiple
organ dysfunction. Patients may present with pallor, cold clammy skin, weak
pulse, and altered consciousness. Prompt control of bleeding and volume
replacement are lifesaving.
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