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Cardiovascular > EXAM #1: CORONARY & PULMONARY CIRCULATION > Flashcards

EXAM #1: CORONARY & PULMONARY CIRCULATION Flashcards

1
Q

What is WPW Syndrome?

A

An accessory pathway linking atrial to ventricular tissue, bypassing the AV node

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2
Q

What normally prevents re-entry?

A

Depolarization circuit encounters tissue in the absolute refractory period

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3
Q

What two mechanisms can lead to the development of re-entry circuits?

A

1) Reduced refractory period– propagating waveform and re-enter a previously blocked path
2) Reduced conduction velocity

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4
Q

What is a passive arrhythmia?

A

Conduction abnormality that arises from an abnormality in tissue structure

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5
Q

List examples of tissue structure changes that can lead to the development of a passive arrhythmia?

A
  • Gap junction changes
  • Fat deposition
  • Fibrosis
  • Changes in cell size
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6
Q

What is the source-sink concept in arrhythmogenesis?

A 
Source= strength of an impulse 
Sink= amount of tissue that must be excited
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7
Q

How does the APD change the source-sink relationship if there is an area of inexctiable tissue?

A
  • Source does NOT change (same impulse strength)
  • Propagates on a relative smaller area (sink)

Strength is relative greater and the APD shortens.

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8
Q

What part of the heart is supplied by the RCA?

A

Posterior LV, and RV

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9
Q

What are the two major branches of the LCA?

A
  • LAD

- Left circumflex artery

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10
Q

What does the LAD supply?

A

Anterior LV

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11
Q

What does the left circumflex supply?

A

Lateral LV

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12
Q

When is blood flow highest through the coronary arteries?

A

Early diastole

*B/c of some retrograde flow from the aorta

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13
Q

What part of the heart is more subject to phasic changes in blood flow?

A

Left heart b/c of higher ventricular wall pressure

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14
Q

What is autoregulation of coronary blood flow?

A

Changes in vascular resistance to maintain constant blood flow

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15
Q

What are the mechanisms of autoregulation?

A

1) Myogenic

2) Metabolic

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16
Q

Define myogenic autoregulation.

A
  • Activation of stretch receptors
  • Stretch receptors alter ion channels
  • Can cause depolarization and contraction of vascular smooth muscle in response to changes in pressure
17
Q

What is metabolic autoregulation?

A

The effects of metabolites on coronary autoregulation

18
Q

What is coronary reserve?

A

Ability of the coronary vasculature to respond to a vasodilatory stimulus

An inability to vasodilate in conditions of increased metabolic demand= reduced coronary reserve

19
Q

What disease states can reduce the coronary reserve?

A

1) Thrombus/ plaque formation= physical impedence to full luminal diameter
2) Heart Failure/DM= inability to properly respond to vasodilatory stimuli

20
Q

What is the sequence of events that happens to coronary blood flow in hypoxia?

A

1) Less O2
2) ATP depletion leads to Adenosine release
3) Adenosine binds A2 receptors

Outcome is vasodilation

21
Q

Describe the influence of the SNS on coronary blood flow.

A

SNS has a BIPHASIC effect on coronay circulation

  • First, alpha activation leads to VASOCONSTRICTION
  • Vasoconstriction= hypoxia
  • METABOLIC response= VASODILATION in a second phase
22
Q

How does the resistance of the pulmonary circulation compare to the systemic circulation?

A

Pulmonary circulation has DECREASED resistance compared to systemic circulation

23
Q

How do the pulmonary vessels compare to the systemic vessels?

A

1) More elastic with less smooth muscle
2) Larger lumen and shorter length
3) More distensible and compressible
4) Blunted myogenic mechanisms

24
Q

What is ventilation: perfusion matching? What is the normal V:Q ratio?

A

Supplying blood to well oxygenated lung tissue

*Normal= 0.8 to 1.0

25
Q

What are the passive mechanisms that regulate pulmonary blood flow?

A

1) Gravity
2) Body position
3) Extravascular pressure
4) Intravascular pressure

26
Q

Generally, speaking how does gravity effect pulmonary perfusion? From a disease standpoint what is the outcome of gravity?

A
  • Blood must work AGAINST gravity to reach the APEX
  • Blood flows with gravity to reach the base

Increased hydrostatic pressure is developed in the base of the lung, which more readily leads to pulmonary edema in the bases

27
Q

What are recruitment and distension as passive mechanisms that alter pulmonary blood flow?

A

Recruitment= opening of previously closed capillaries to accommodate increased blood flow

Distension= widening of already open capillaries to accommodate increased blood flow

28
Q

What is the most important active mechanism to regulate pulmonary blood flow?

A

Hypoxic VASOCONSTRICTION

Note that this is OPPOSITE compared to the coronary vessels

29
Q

What is the outcome of hypoxic vasoconstriction?

A

Diversion of pulmonary blood flow from hypoxic lung regions

30
Q

What is the normal pressure of the pulmonary artery?

A

20 mmHg

31
Q

What pressure defines pulmonary artery HTN?

A

25 mmHg

32
Q

What is extravascular compression (heart)?

A

Compression of the coronary arteries with increased chamber pressure during systole

33
Q

What are the three major mechanisms that alter coronary blood flow?

A

1) Extravascular compression
2) Autoregulation
3) Autonomic input

34
Q

What is phasic blood flow in regards to the coronary arteries?

A
  • The undulating or phasic flow of blood through the coronary arteries
  • This is a pressure dependent phenomenon; flow is high during diastole and low during systole
35
Q

What is the consequence of severe/prolonged hypoxia?

A
  • Hypoxic vasoconstriction that INCREASES pulmonary vascular resistance
  • Causing PULMONARY ARTERY HTN
36
Q

What determines pulmonary artery pressure?

A

CO and pulmonary vascular resistance (PVR)

37
Q

What normally happens as CO increased to maintain a constant pulmonary artery pressure?

A

Decreased PVR

38
Q

What are some diseases that will increase PVR leading to PAH?

A

1) PE

2) LVH

39
Q

What is the consequence of prolonged PAH?

A

RVH

Cardiovascular (38 decks)

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