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Cardiology - Heart Failure > Cardiac Cycle > Flashcards

Cardiac Cycle Flashcards

1
Q

List the 5 main determinants of ventricular mechanical performance:

A

Preload
Afterload
Contractility (Inotropy)
Diastolic function (Lusitropy)
Heart rate (Chronotropy)

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2
Q

List the 3 basic events in the cardiac cycle with respect to the left ventricle

A

LV contraction
LV relaxation
LV filling

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3
Q

LV pressure ____ as Calcium arrives at the contractile proteins after cellular depolarization triggers actin-myosin interaction

A

increases

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4
Q

When LV pressure exceeds that in the ______ (normally ___ to ___ mm Hg), the mitral valve closes, causing the mitral component of the first sound, M1

A

left atrium
8 to 15 mmHg (dime)

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5
Q

The phase of LV contraction after mitral closure and before aortic opening when the LV volume is fixed is called ____

A

Isovolumic contraction

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6
Q

LV pressure continues to ______ until it _____ aortic pressure, causing the aortic valve to open

A

increase
exceeds

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7
Q

At the initiation of LV relaxation, myocyte calcium starts to ____ because of ____. Calcium dissociates from ____ , thereby preventing further cross-bridge formation

A

decline
SR Calcium uptake
Troponin C

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8
Q

What are the two phases of blood flow from the left ventricle to the aorta? When do they occur (roughly)?

A

Phase of rapid ejection: occurs right when LV pressure exceeds aortic pressure, causing the aortic valve to open

Phase of reduced ejection: occurs during the beginning of LV relaxation

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9
Q

During the phase of reduced ejection, blood flow from the LV to the aorta rapidly diminishes but is maintained by ____; also called the ____ effect

A

aortic recoil
Windkessel effect

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10
Q

When the pressure in the aorta significantly ____ the falling LV pressure in the phase of reduced ejection, the aortic valve ____

A

exceeds
closes

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11
Q

Describe isovolumic relaxation in the LV

A

This is the phase in the cardiac cycle where LV pressure has fallen significantly below that of the aorta (causing the aortic valve to close) but has not yet fallen below that of the left atrium

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12
Q

When LV pressure is _____ than that in the left atrium, the mitral valve opens and the filling phase of the cardiac cycle restarts

A

lower

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13
Q

Under normal circumstances, LV filling is caused by a _____ from the ____ to the ____

A

negative pressure gradient
left atrium
LV apex

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14
Q

As pressures in the LA and LV equalize, LV filling virtually stops. Continued filling requires that atrial pressure ____ LV pressure. This is achieved by _____ (also called the ____). This mechanism is especially important at ____

A

exceeds
atrial systole
left atrial kick
high heart rates

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15
Q

At the molecular level, an increased inotropic state is usually explained by either ____ or ____

A

enhanced Ca++ transients
enhanced myofilament Ca++ sensitivity

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16
Q

Frequently, increased inotropy is associated with enhanced rates of ____, also referred to as ____

A

relaxation
lusitropy

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17
Q

Define preload.
What is it best represented by?
What is it best estimated by?

A

Preload describes the degree of myocardial stretch or distinction before contraction has started
Preload is best represented by the LVEDV (end diastolic volume)
Preload is best estimated by the LVEDP (end diastolic pressure)

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18
Q

Define afterload.
What can afterload be more accurately described as?

A

Afterload refers to the forces opposing LV ejection
Afterload is often oversimplified as being equal to aortic blood pressure, but is more accurately described as aortic impedance or elastance

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19
Q

The relationship between LVEDV and LVEDP is ____, with the slope reflecting LV ___

A

curvilinear
compliance

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20
Q

An increase in the strength of contraction can generally be categorized as either a _____ effect (_____), or an ____ effect (_____)

A

Frank-Starling effect (increased sarcomere length)
inotropic effect (altered Ca++ transient or myofilament Ca++ sensitivity)

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21
Q

By the Frank-Starling law, ____ LV volume leads to ____ contractile function, which in turn will ____ the systolic aortic pressure and thus the ____ in the subsequent contraction cycle

A

increased
increased
increase
afterload

22
Q

LV pressure and LV volume are nonlinearly related due to variance in ______

A

myocardial compliance

23
Q

In patients with reduced diastolic LV compliance, a ____ LVEDP is required to achieve a similar LVEDV (preload)

A

higher

24
Q

The true “distending” pressure that determines LV preload volume is referred to as the ____ and can be calculated by _____

A

LV transmural pressure
LVEDP minus the external pericardial pressure (approximated by RA pressure)

25
Q

External pericardial pressure can be approximated by ____

A

right atrial pressure (nickel)

26
Q

State Laplace’s law

A

Wall stress = (pressure x radius)/(2 x wall thickness)

27
Q

According to Laplace’s law, the larger the LV size and radius, the ___ is the wall stress

A

larger

28
Q

According to Laplace’s law, at any given radius (LV size), the greater the pressure developed by the LV, the ___ is the wall stress

A

greater

29
Q

An increase in wall stress achieved by either LV size or intraventricular pressure will ___ myocardial oxygen uptake because a ____ rate of ATP use is required for the myofibrils to develop ___ tension

A

increase
greater
more

30
Q

Wall stress ___ as afterload increases

A

increases

31
Q

In congestive heart failure, the heart dilates so the increased radius ____ wall stress. Furthermore, because ejection of blood is inadequate, the radius stays too large throughout the contractile cycle, and both LVEDV and LV end systolic wall stress are ____. This _____ LV efficiency, _____ myocardial oxygen demand, and ____ release of natriuetic peptide levels.

A

increases
increased
decreases
increases
increases

32
Q

Peak systolic wall stress reflects the 3 major components of afterload:

A

Peripheral resistance
Arterial compliance
Peak intraventricular pressure

33
Q

____ arterial compliance and ____ afterload can be anticipated with aortic remodeling and dilation, as in severe systemic hypertension or in elderly patients

A

Decreased
increased

34
Q

An increased heart rate progressively ____ the force of ventricular muscle contraction. This is also referred to as the _____ phenomenon. However, at a very high heart rate, force progressively ____

A

increases
Bowditch staircase phenomenon
decreases

35
Q

At a higher heart rate, there is ____ Na+ and Ca++ entry per unit time and ____ time for the cell to extrude these ions, which results in _____ [Na+] and cellular and SR Ca++ content. The ____ in SR Ca++ content ___ the amount of Ca++ released during the action potential, the primary cause of the ____ in contractility at higher heart rates.

A

increased
decreased
higher
increase
increases
increase

36
Q

______ diastolic wall stress, resulting from increased preload (EDV), will require ____ oxygen because the _____ stroke volume must be ejected against the afterload

A

Increased
more
greater

37
Q

The double product is a practical index of ____ uptake.
It is calculated by ____

A

Oxygen
Double product = SBP x HR

38
Q

Define minute work. How does this relate to myocardial oxygen consumption?

A

Minute work is SBP x SV X HR
Minute work relates to mycardial oxygen uptake because it accounts for three determinants of myocardial oxygen uptake:
1) Preload (helps determine stroke volume)
2) Afterload (in part determined by blood pressure)
3) Heart rate

39
Q

Define the pressure-work index

A

The double product x cardiac output
(SBP x HR) x (SV x HR)

40
Q

The same degree of vasodilation causes a ____ decrease in SBP and a ____ increase in SV in HFpEF whereas, in HFrEF, this causes a ____ decrease in SBP and a ____ increase in SV. This is because the pressure-volume slope in HFpEF is much ____ than in HFrEF

A

large
small
small
large
greater (much higher LV pressure compared LV volume in HFpEF compared to HFrEF)

41
Q

In patients with HFrEF, the ventricle is ____, EF is low, and contractility is severely ____. As such, the pressure-volume loop is shifted to the far ____ on the volume axis, and the end-systolic pressure-volume relationship (ESPVR, contractility) is very _____. In this setting, a reduction in arterial afterload (Ea) produces _____ reductions in blood pressure despite often _____ increases in stroke volume. This heightened “afterload dependence” of the LV in HFrEF serves as the hemodynamic basis of aggressive use of _____ in this disease.

In contrast, patients with HFpEF display a(n) ____ Ees (end-systolic elastance) leading to a ____ ESPVR. In this patient, the same degree of afterload reduction (Ea) using a _____ causes a much more _____ decrease in blood pressure, with _____ improvement in forward stroke volume.

A

dilated
depressed
right
shallow
modest
dramatic
vasodilators

increased
steep
vasodilator
dramatic
little

42
Q

The phases of diastole are ______ and ______.

A

isovolumic pressure decline
filling

43
Q

The filling phase of diastole is divided into ____, _____ and _____.

A

early rapid filling
diastasis
atrial systole

44
Q

Early rapid filling contributes ___ to ___% of LV filling in normal individuals.

A

70 to 80%

45
Q

Early diastolic filling is driven by which gradient?

A

LA to LV pressure gradient

46
Q

Diastasis occurs in ___-diastole when ____ and ____ pressure is usually almost equal.

A

mid-diastole
LA
LV

47
Q

Diastasis contributes _____ of LV filling and its duration _____ with tachycardia

A

less than 5%
shortens

48
Q

Atrial systole contributes ____ to ____% of LV diastolic filling and is dependent on several factors including the ____ interval

A

15 to 25%
PR interval

49
Q

The left atrium acts as a blood-volume sensor in the heart and releases ____ in response to stretch so that ___-induced diuresis can help restore blood volume to normal.

A

atrial natriuretic peptide (ANP)

50
Q

The left atrium contains receptors for the affront arms of various reflexes, including mechanoreceptors that ______ the sinus discharge rate, thereby contributing to the _____ of exercise as venous return increases (_____ reflex).

A

increase
tachycardia
Bainbridge reflex

Cardiology - Heart Failure (5 decks)

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