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Body in Balance Midterm #2 > Pulmonary Circulation: Physiology and Pathology > Flashcards

Pulmonary Circulation: Physiology and Pathology Flashcards

1
Q

Fetal Pulmonary Circulation

A

Very high pulmonary vascular resistance

Low oxygen tension

Low vasodilators (PgI2, NO)

High vasoconstrictors

8% of blood flow to lungs

Foramen ovale and ductus arteriosus shunt blood to systemic circulation

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2
Q

Hypoxic Pulmonary Vasoconstriction

A

Alveolar hypoxia (not arterial) controls vasoconstriction

Action is at smooth muscle cell in small PA’s

Hypoxia inhibits potassium channels on smooth muscle cell membrane → depolarization

Voltage-gated Ca+2 channels allow Ca+2 to enter smooth muscle cells

Increased cytosolic Ca+2 leads to myosin light chain phosphorylation and smooth muscle contraction

Inhibition of potassium current proportional to severity of hypoxia

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3
Q

postnatal pulmonary circulation

A

After birth marked reduction in vascular resistance

Alveolar oxygenation ! NO, PgI2

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4
Q

Pulmonary Vascular Resistance

A

PVR = (mPAP-LAP)/CO (Woods units; normal <1.5)

PVR = (mPAP-LAP)/CO x 80 (dynes·sec·cm-5; normal 20-120)

  • PVR is dependent on pressures and flow
  • PVR actually decreases with rising CO due to recruitment & distension of capillaries allowing for high capacitance of pulmonary system
  • PVR is only 1/10 of systemic vascular resistance (800-1200 dynes·sec·cm-5)
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5
Q

Diagnostic Evaluation of PH

A
  • ECHO: primary screening test for PH
    • Estimated PASP >35 mmHg, LA/RA dilation, tricuspid regurgitation, RV hypertrophy and dysfunction
  • Evaluate for cause of PH
    • Group 1: LFTs, ANA, HIV
    • Group 2: left heart/valve disease (ECHO)
    • Group 3: PFTs, overnight oximetry or polysomnogram
    • Group 4: VQ scan
  • Right heart catheterization: confirmatory test for PH
  • Diagnostic
    • Right Heart Cath:
      • mPAP > 25mmHg
    • For PAH:
      • PAOP < 15 mmHg
      • PVR > 3 Woods units
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6
Q

Mechanism of PH due to Left Heart Disease

A
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7
Q

Causes of Pulmonary Hypertension

A
  • Idiopathic Pulmonary Arterial Hypertension
    • Intimal, medial, and adventitial thickening of muscular pulmonary arteries (A) • Pulmonary arteritis • Concentric “onion skinning” artery thickening • Plexiform lesions (G)
  • Left Heart Disease
    • Systolic heart failure • Diastolic heart failure • Valvular disease • Congenital anomalies of the left ventricular outflow tract
  • Chronic Thromboembolic Disease
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8
Q

Causes of Pulmonary Hypertension: WHO Classifications

A
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9
Q

Cor Pulmonale: overview

A
  • RV failure that develops from chronic pulmonary hypertension from pulmonary disorders
  • Primary pulmonary vascular problem (ie IPAH)
  • Primary pulmonary airway/alveolar/parenchymal problem (ie COPD, pulmonary fibrosis)
  • Does not include RV failure secondary to LV failure
  • Evidence of altered structure (hypertrophy/dilation) and impaired RV function
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10
Q

Why does the right heart fail?

A

Right Ventricle

  • Low pressure system: 20/10
  • Right ventricle has thin muscle wall
  • Not as adaptable to higher strain

Left Ventricle

  • High pressure system: 120/80
  • Left ventricle has thick muscle wall
  • More adaptable to higher strain
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11
Q

Idiopathic Pulmonary Arterial Hypertension

A
  • ** diagnosis of exclusion **
  • 1-2 cases per million in general population
  • 3-4x as common in females
  • 3rd-5th decades
  • No ethnic predispositions
  • Hereditary factors
  • Elevated blood pressure in pulmonary arteries that can reach systemic values
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12
Q

Normal Pulmonary Vascular Response to Hyperdynamic State

A
  • PAP rises due to CO (flow)
  • mPAP = PVR x CO + LAP
  • Decrease in PVR due to recruitment and vascular distention
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13
Q

Lung Disease

A
  • Destruction of lung parenchyma leading to loss of vascular bed
  • Stiffening of large PAs
  • Chronic hypoxia leads to medial hypertrophy and musculariza/on of small PAs
  • Chronic inflamma/on intensifies vascular remodeling
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14
Q

Pulmonary Hypertension

A

Definition:

  • Mean PAP > 25 mmHg at rest

High morbidity/mortality from right heart failure

Presenting symptoms

  • Dyspnea in majority
  • Syncope, chest pain, edema

Many potential etiologies

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15
Q

Pulmonary Vasodilators

A
  • Alkalosis
  • Hyperventilation
  • Oxygen
  • Nitric oxide (Produced by endothelium; Can be delivered exogenously (inhaled)
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16
Q

Pulmonary Hypertension in Lung Disease and Hypoxia

A
  • Second most common cause of PH
  • Typically only in severe disease (think hypoxia, acidosis, hypercarbia)
    • Interstitial lung disease (ie pulmonary fibrosis, sarcoid)
    • COPD/Emphysema
    • Sleep disordered breathing (ie obstructive sleep apnea, obesity hypoventilation syndrome)
  • Treatment aimed at underlying disease, avoiding vasoconstrictors ie hypoxia
17
Q

mediators of pulmonary vasoconstriction

A

Hypoxia • Acidosis • Hypoventilation • Hypercarbia

18
Q

Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

A
  • Loss of vascular surface area due to clot
  • More common with large clot burden or recurrent PE
  • Microvascular remodeling similar to that seen in PAH
  • Occurs in up to 4% of PE, typically within 2 yrs of PE
  • 1 in 4 patients with CTEPH have NO prior history of PE
  • Requires lifelong anticoagulation
  • Should be evaluated for surgical embolectomy
19
Q

Pulmonary Hypertention in Left Heart Disease

A

Most common cause of PH

  • Common: systolic or diastolic heart failure, aortic or mitral valve disease
  • Uncommon: Restrictive pericarditis, infiltrative cardiomyopathy
  • True incidence unknown, but may affect up to 50% of patients with left heart failure

Differentiated from PAH by elevated left atrial pressure (and therefore PAOP)

Treatment aimed at treating left heart disease

20
Q

Treatment of PAH

21
Q

Humoral Mediators of Pulmonary Pressure

A

Vasoconstrictors

  • Endothelin-1
  • Thromboxane A2
  • Serotonin
  • Angiotensin II

Vasodilators

  • Prostaglandin I2 and E2
  • Oxygen
  • Vasoactive Intestinal Peptide (VIP)
22
Q

Cor Pulmonale: common causes, symptoms, findings and things it can cause

A
  • Most common causes: COPD, pulmonary fibrosis
  • Symptoms: Progressive dyspnea, syncope, chest pain
  • Exam findings: Elevated JVP, loud S2, holosystolic murmur at the left lower sternal border, hepatomegaly, ascites, lower extremity edema
  • Common cause of hospitalization and death
23
Q

Clinical Presentation of PH

A
  • Early - nonspecific symptoms
    • Dyspnea is initial symptom in 60%
    • Fatigue, chest pain, palpitations, syncope
  • Late – evidence of right heart failure
  • Labs nonspecific, elevated BNP common
  • CXR – enlarged PA’s and RA/RV dilatation
  • PFT’s – reduced DLCO

Body in Balance Midterm #2 (26 decks)

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