Cardiovascular medicine, lecture I

Question 1

■ Systolic dysfunction – broadly refers to?
■ Diastolic dysfunction – broadly refers to?

Answer 1

■ Systolic dysfunction – pump failure
■ Diastolic dysfunction – filling failure

Question 2

Forward failure broadly = ?
Backward failure broadly = ?

Answer 2

Forward failure = reduced cardiac output
Backward failure = congestion

Question 3

Blood composition

Answer 3

■ Plasma 55%
■ ‘Buffy coat’ 4%
■ RBC 41%

Changes will have an effect on cardiac function.

Question 4

How does the cardiac output from the left heart (systemic circulation) differ from the right heart (pulmonic circulation)?

Answer 4

Left CO is a bit more than right.

– 1-2% more blood is shunted from left cardiac output volume via bronchial circulation (returning to LA).

+ Small fraction of coronary circulation via
thebesian veins (cardiac veins).

Question 5

The aorta divides into the…

Answer 5

Cranially into truncus brachiocephalicus,
a. subclavia sinistra & dextra, common carotid arteries etc. etc.

Caudally into the aorta decendens etc…. aa.iliaca.

Question 6

The arterial system is mostly arranged “in parallel,” meaning that blood flows from the heart into separate arterial branches that independently supply different organs. This allows each organ to receive freshly oxygenated blood directly from the heart without being affected by other organs’ metabolic needs.

However, there are two major exceptions where circulation is arranged “in series” rather than in parallel:

Answer 6

splanchnic - Instead of returning directly to the heart, this blood is collected by the portal vein and directed to the liver.

& renal circulation - two-capillary-bed system is called a portal system (specifically, the renal portal system), allowing for filtration in the glomerulus and reabsorption/secretion in the tubules.

Question 7

Describe the pulmonary circulation.

Answer 7

Right heart circulation: starting from the main pulmonary artery, truncus pulmonalis to left and right pulmonary arteries… pulmonary capillaries - pulmonary veins… returning to the left atrium.

Question 8

Describe the events that occur during one cardiac cycle. (4+)

Answer 8

1. LV contraction
   ■ Pressure generation
2. Blood flowing to aorta
   ■ Aortic elasticity
3. Ventricular relaxation
   ■ Systemic blood distribution and diffusion into capillaries
   ■ Collection to venous system
   ■ Vena cava -> RA
   ■ RA -> RV
4. RV contraction
   ■ Blood flows to pulmonary circulation
   ■ Oxygenated blood -> LA

Question 9

Resistance arteries are

Answer 9

the smallest arteries and arterioles.

Branching arteries reduce BP pulsation (“pressure
reservoirs”).

Capillaries and small venules are exchange vessels.

Question 10

Exchange vessels are

Answer 10

capillaries and small venules.

Then, veins are highly distensible, capacitance vessels (volume reservoir).

Smallest arteries and arterioles = resistance arteries

Question 11

Volume reservoir is made up of

Answer 11

veins which are highly distensible, capacitance vessels (volume reservoir).

Question 12

Percentage of blood volume in veins and arteries?

Answer 12

Blood volume: 70% in veins, 17% in arteries

Question 13

What occurs in case of reduced cardiac output or blood volume loss?

Answer 13

venous contraction

Question 14

Forward failure aka reduced
cardiac output presents with

Answer 14

Weakness, fainting, low blood
pressure, pale mucous
membranes

Question 15

Backward failure aka
congestion presents with

Answer 15

*Left sided: pulmonary edema that can cause dyspnea, cough

*Right sided: ascites, pleural effusion, tachypnea

Question 16

Anulus fibrosus is

Answer 16

the skeleton of the heart and acts as electrical insulation between atria and ventricles.

Question 17

Desmosomes are

Answer 17

critical adhesion structures in cardiomyocytes.

Question 18

Sarcomeres are

Answer 18

the basic contractile unit of muscle fiber. Each sarcomere is composed of two main protein filaments—actin and myosin.

■ Myocyte packed with myofibrils
■ Myofibril consists of sarcomeres
■ Sarcomere = basic contractile unit

Question 19

Describe the mechanism of contraction of cardiac myocytes.

Answer 19

■ Shortening of sarcomeres, Ca++ initiates shortening

■ Released Ca²⁺ binds to troponin, causing a conformational change on the actin filament, exposing myosin-binding sites.

■ ATP energizes myosin head so it can bind actin and shorten the sarcomere. Contraction is linked to O2 supply.

■ Ca²⁺ is pumped back into the sarcoplasmic reticulum and K+ efflux occurs for repolarization.

Question 20

Coronary artery blood flow occurs at what point of the cardiac cycle?

Answer 20

Diastole

■ Most blood returns via coronary
sinus to right atrium.

■ A proportion of drainage via
thebesian veins.

Question 21

What is sinus of Valsalva?

Answer 21

The sinus of Valsalva refers to the three pouch-like dilations located just above the aortic valve in the ascending aorta.

These sinuses are important because they help direct blood flow into the coronary arteries, which originate from them.

Question 22

Concentric hypertrophy vs eccentric hypertrophy

Answer 22

Concentric thickens inward due to pressure overload.

Eccentric thickens outward due to volume overload.

Question 23

Sarcomeres added in parallel indicates?
Sarcomeres added in series indicates?

Answer 23

in parallel - concentric hypertrophy
in series - eccentric hypertrophy

Question 24

What does Starling’s law of the heart tell us?

Answer 24

The more the ventricular muscle fibers are stretched during diastole (due to increased venous return), the stronger the subsequent contraction.

However, if the heart is overstretched (as in heart failure), the contractile force declines, leading to reduced cardiac output.

Question 25

Describe the cardiac conduction system. (5)

Answer 25

sinus node / sinoatrial node / SA node (right atrium) atrioventricular node / AV node bundle of His bundle branches purkinje fibers

Question 26

The P wave represents

Answer 26

sinus node activation aka atrial depolarization which will lead to atrial contraction

Question 27

The PR interval represents

Answer 27

atrioventricular node delay (to allow the atria to empty into the ventricles)

Question 28

The QRS bundle represents

Answer 28

ventricular depolarization (Bundle of His, Bundle Branches, Purkinje Fibers) resulting in ventricular contraction.

Question 29

The T wave represents

Answer 29

ventricular repolarization

Question 30

The ST segment represents

Answer 30

The ST segment represents the period between ventricular depolarization and repolarization (the plateau phase).

Question 31

At the end of diastole all cardiac chambers are

Answer 31

relaxed. ## Footnote (for a brief moment)

Question 32

Ventricular volume at the end of diastole is termed? Ventricular pressure at the end of diastole?

Answer 32

end diastolic volume (EDV) end diastolic pressure (EDP)

Question 33

Atrial systole is 20% of ventricular filling. What does this mean?

Answer 33

At the start of atrial systole, the ventricles are normally filled with approximately 70–80 percent of their capacity due to inflow during diastole. Atrial contraction, also referred to as the “atrial kick,” contributes the remaining 20–30 percent of filling.

Question 34

S1 heart sounds represents

Answer 34

Closure of the atrioventricular valves after the sharp rise of ventricular pressure reaches the threshold required. For a brief moment, we have - isovolumetric contraction when the volume does not change at all.

Question 35

What causes the aortic valve to open?

Answer 35

When the left ventricular pressure overtakes the aortic valve pressure. Ventricular ejection involves: ■ Rapid ejection phase ■ Reduced ejection phase Contraction ceases at second half of ejection.

Question 36

What is the dicrotic notch?

Answer 36

The dicrotic notch which is a drop on the down slope shows systole termination and depicts the aortic valve closure and successive backward flow. The position of the dicrotic notch throughout the cardiac activity differs as per the duration of aortic closure.

Question 37

S2 heart sound represents

Answer 37

Closure of semilunar valves (aortic and pulmonary)

Question 38

all heart valves are closed during

Answer 38

Isovolumetric relaxation

Question 39

If EDP is high,

Answer 39

S3 can be heard.

Question 40

Diastasis is

Answer 40

the period between rapid filling and atrial kick.

Question 41

second phase of ventricular filling refers to

Answer 41

Atrial systole | If ventricles are stiff, S4 can be heard. ## Footnote Cause remember that 80% of the systolic volume fills due to inflow during diastole. The rest comes with atrial contraction.

Question 42

What is the pressure-volume loop?

Answer 42

Pressure-volume loops are graphs showing the changing relationship between left ventricular pressure and volume during a cardiac cycle. They provide useful information such as stroke volume or end-diastolic volume, as well as systolic, diastolic, and pulse pressure.

Question 43

Describe cardiac chamber pressures.

Answer 43

Right Atrium (RA) → 2–8 mmHg * Lowest pressure since it receives blood from the body (via the superior and inferior vena cava). Right Ventricle (RV) → 15–30 mmHg (systolic) / 2–8 mmHg (diastolic) * Systolic pressure (15–30 mmHg): When the ventricle contracts. * Diastolic pressure (2–8 mmHg): When it relaxes and fills. Pulmonary Artery (PA) → 15–30 mmHg (systolic) / 4–12 mmHg (diastolic) * Similar to RV but slightly higher diastolic pressure due to pulmonary vascular resistance. Left Atrium (LA) → 2–12 mmHg * Slightly higher pressure than RA to push blood into the left ventricle. Left Ventricle (LV) → 100–140 mmHg (systolic) / 3–12 mmHg (diastolic) * Systolic pressure (100–140 mmHg): When it contracts. * Diastolic pressure (3–12 mmHg): When it relaxes. Aorta → 100–140 mmHg (systolic) / 60–90 mmHg (diastolic) * Pressure is highest in the systemic circulation. * Diastolic pressure is maintained by the elastic recoil of the aorta.

Question 44

CO = | Cardiac output – volume of blood pumped in a minute. ## Footnote (equation)

Answer 44

CO=HR * SV ## Footnote Affected by characteristics of heart tissues (HR + contractility) and characteristics of vascular resistance (preload & afterload).

Question 45

Regulation of the heart rate.

Answer 45

■ HR control mainly via autonomic NS ■ Sinus rate – controlled by symp- and parasymph- NS. ## Footnote Normally parasymph predominates.

Question 46

Parasympatholytic drugs increase HR significantly. What do sympatholytics do?

Answer 46

Sympatholytics actually only reduce the HR slightly (e.g. beta blockers). That's why we favor atropine instead which is parasympatholytic and brings up the heart rate.

Question 47

Fancy terms for increasing the following: – Heart rate – Strenght of contraction – Conduction velocity – Relaxation

Answer 47

– Heart rate (chronotropy) – Strenght of contraction (inotropy) – Conduction velocity (dromotropy) – Relaxation (lusitropy)

Question 48

Preload is

Answer 48

Filling of the heart prior to contraction (EDV) Preload, afterload and inotropy have interdependent effects - changing any of these variables, changes the other two. ## Footnote Frank-Starling law of the heart: increased venous return results in increased force of contraction.

Question 49

Frank-Starling law of the heart: increased venous return results in

Answer 49

increased force of contraction. ## Footnote Preload, afterload and inotropy have interdependent effects - changing any of these variables, changes the other two.

Question 50

Afterload is

Answer 50

the total resistance to blood flow out of the heart. ## Footnote Preload, afterload and inotropy have interdependent effects - changing any of these variables, changes the other two.

Question 51

Primary physiologic way of increasing cardiac output is...

Answer 51

By increasing contractility by way of the effect of noradrenaline or adrenaline. Preload, afterload and inotropy have interdependent effects - changing any of these variables, changes the other two. ## Footnote inotropy

Question 52

Definition of heart failure.

Answer 52

HF = a complex clinical syndrome resulting from any structural or functional disorder impairing ventricular filling or ejection. – Inability to meet metabolic needs; or meets only with elevated filling pressures. – Circulatory failure – Myocardial failure: deficiency of myocardial contraction – Insufficient cardiac filling

Question 53

Heart failure - classification (2)

Answer 53

■ Congestive heart failure (CHF): “backward failure” ■ Reduced cardiac output: “forward failure”

Question 54

Congestive heart failure (CHF): “backward failure” is characterized by (2)

Answer 54

– Left sided: pulmonary edema – Right sided: jugular distension, pleural effusion, hepatic congestion, ascites, (peripheral edema)

Question 55

Reduced cardiac output: “forward failure” is characterized by

Answer 55

Weakness, syncope, hypotension, poor perfusion

Question 56

Main 4 compensatory mechanisms in a failing heart. (4)

Answer 56

Four levels of compensatory mechanisms: – Reduction of parasympathetic tone – Increase of sympathetic tone – Water retention – Cardiac remodeling ## Footnote These are only effective short-term afterwhich decompensation occurs.

Question 57

Basic steps of RAAS.

Answer 57

Renin-Angiotensin-Aldosterone system 1. Kidneys detect low blood pressure or low sodium (or are activated sympathetically) and release renin from the juxataglomerular cells). 2. Renin acts on angiotensinogen (produced by the liver) and converts it into angiotensin I. 3. Angiotensin-Converting Enzyme (ACE) (mainly from the lungs) converts angiotensin I into angiotensin II. 4. Angiotensin II is a powerful vasoconstrictor that raises blood pressure. * It also stimulates Aldosterone Release (adrenal glands) which increases sodium and water retention. * And stimulates ADH Release (from the posterior pituitary) which promotes water reabsorption in the kidneys.