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Pul. hypertension

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Pulmonary hypertension

Definition

Aetiology

Pathophysiology

Investigations

Management

Further reading

Definition

Systolic pressure > 35 mmHg }
Diastolic > 15 } at rest
Mean > 25 }

Mean > 35 during exercise

Aetiology

Causes can be grouped into active, passive and reactive (active superimposed on passive). "Passive" pulmonary hypertension is due to post-pulmonary capillary elevation and is therefore associated with a high PCWP. "Active" is due to the constriction or obstruction of capillary and precapillary vessels resulting in increased resistance to flow. "Reactive": pulmonary hypertension initially passive but the upstream pulmonary vasculature responds to chronic passive congestion by developing an active-superimposed-on-passive component

Passive

- LVF
- mitral valve disease
- congenital cardiac disease (eg cor triatriatum)
- congenital pulmonary vein stenosis
- acquired obstruction of major pulmonary veins
- left atrial myxoma or thrombus

Active

- pulmonary embolus
- schistosomiasis
- primary pulmonary hypertension
- Eisenmenger syndrome
- disorders of ventilation

  • due to vasoconstriction of pulmonary bed:
  • high altitude pulmonary hypertension (residence > 3000 m)
  • primary central hypoventilation
  • sleep-apnoea syndrome
  • obesity-hypoventilation syndrome
  • polio
  • myasthenia gravis
  • COAD (main determinants are acidaemia and hypoxia)
  • cystic fibrosis

NB most potent and clinically important vasoconstrictive stimulus is alveolar hypoxia

  • due to anatomic restriction of capillary bed:
  • sarcoidosis
  • systemic sclerosis
  • cryptogenic fibrosing alveolitis
  • ARDS
  • extensive lung resection
  • extensive fibrothorax
  • due to both:
  • kyphoscoliosis
  • chronic fibrotic TB

- collagen-vascular disease
- sickle haemaglobinopathies
- portal hypertension
- drugs and herbal remedies
- diffuse pulmonary amyloidosis
- pulmonary vasculitis

Reactive

- mitral valve disease
- pulmonary capillary haemangiomatosis
- toxic oil syndrome due to rapeseed oil ingestion

Pathophysiology

Cardiac compensatory mechanisms

  • to maintain cardiac output RV can compensate acutely, subacutely and chronically
  • acute: increased sympathetic activity increases HR and contractility
  • subacute: RV dilates due to inability of chamber to empty completely. According to Laplace’s law this results in increased afterload (T=P x R/(2 x wall thickness)). However preload also increases and thus cardiac output increases according to Starling’s law. ie RV ejection increases at expense of increased end-diastolic pressure and increased risk of RV "failure"
  • chronic: gradual rise in RVEDP leads to RVH
  • in critically ill there is some evidence that extreme RV volume overload can be partially responsible for LV failure

Symptoms

Features of underlying disease

  • exertional dyspnoea (without orthopnoea or PND)
  • exertional substernal chest pain
  • fatigue
  • exertional or post-exertional syncope
  • symptoms often masked by those of underlying disease

Signs

  • physical signs that can be attributed solely to pulmonary hypertension are predominantly those of RV pressure overload and therefore are not usually appreciated until PASP approaches 55 mmHg
  • large A wave in JVP
  • RV heave
  • pulmonary ejection click and flow murmur
  • RV 4th HS
  • signs of RVF
  • signs often overshadowed by those of underlying disease

Investigation

CXR

  • active pulmonary hypertension: marked enlargement of main PA segment, dilatation of central hilar PA branches down to origin of segmental vessels and constriction of segmental arteries. Pulmonary veins not dilated
  • passive: signs of pulmonary venous hypertension.

ECG

  • helpful in predicting presence of severe pulmonary hypertension due to primary pulmonary hypertension, congenital heart disease and interstitial pneumonitis (RAD, RVH). Less reliable in PE and COPD

Echo

  • used to evaluate right heart morphology and function; exclude LV and congenital heart disease, mitral valve disease, and LA myxoma; estimate PAP from TR jet. (Estimate of PASP correlates well with catheter measurements)

Radionuclide angiography

  • most useful in evaluating course of disease once it is known and response to treatment

Cardiac catheterization

  • single most important investigation
  • passive: raised PCWP and PAP. PAEDP-PCWP < 5 mmgHg
  • active: Raised gradient but normal PCWP
  • reactive: both PCWP and gradient are increased

Management

- treat cause if possible
- avoid factors which cause pulmonary hypertension eg acidosis and hypercarbia
- vasoactive drugs such as prostacyclin, PGE1, nitric oxide, adenosine, diazoxide, nifedipine, phentolamine and hydralazine may help. Should be used in combination with PA catheter to determine effect on pulmonary circulation and cardiac output.
- action of nitric oxide is most specific to pulmonary vascular bed as binding to Hb in pulmonary capillary blood markedly reduces its systemic vasodilator activity
- pulmonary vascular responses to IV prostacyclin or adenosine are usually similar to those of inhaled nitric oxide but may increase shunt as not delivered selectively to those parts of the lung which are ventilated
- aerosolized prostacyclin produces selective effects similar to those of inhaled nitric oxide
- ensure adequate oxygenation
- presence of reactive pulmonary hypertension should not be considered a contraindication to mitral valve replacement in patients with MS as both components of the pulmonary hypertension resolve with time

Drug

Route

Dose

Half life

Prostacylcin

IV

2-20 ng/kg/min

3-5 min

Adenosine

IV

50-200 m g/kg/min

5-10 s

Nitric oxide

Inhaled

5-80 ppm

15-30 s

Nifedipine

PO

30-240 mg/day

2-5 h

Diltiazem

PO

120-900 mg/day

2-4.5 h

Further reading

Rubin LJ Pulmonary hypertenson. In Rippe 3rd ed, 1996

Rubin LJ. Pulmonary hypertension. NEJM, 1997; 336:111

© Charles Gomersall July 1999


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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