Pulmonary artery (PA) pressure in an individual living at sea level is 18-25/6-10 rnmHg. PAH exists when PA systolic and mean pressure exceed 30 and 20 Inn1 respectively. PAH is a haemodynamic abnoimalily common to a variety of conditions that is characterized by increased right ventricular after load and work. The clinical manifestations, natural history, and reversibility of PAH depend heavily on the etiology, severity and nature of pulmollary vascular lesion, PAH can either bc acute or chronic. The acute form is usually seen in PE which was dealt in previous section.This section deals with chronic PAH.The cause of the PAH and their descriptions afe as follows:
1)The first calegoiy includes patients of PAH without any identifiable cause or so-called priinaiy pulinonary hypertension (PPH). This group will be discussed subsequently. In situations where a cause can be identified the condition is called as secondary PAH.Secondary PAH is inore common than primruy variety and the various causes are shown in Table .
2) Secondary causes,
3) Pulmonary venous hypertension,
4) Left to right shunt lesions,
5) Disorders of respiratory system or hypoxemla,
6) Thrombotic or embolic diseases,
7) Diseases of pulmonary vasculature, and
6 ) Others.
Pulmonary Venous Hypertension (PVH)
This category consists predominantly of left sided valvular or myocardial diseases.The common valvular lesions which produce PVH include mitral stenosis, mitralm regurgitation, mixed mitral valve disease and also aortic valve disease. The initial hemodynamic abnormality in all these conditions is elevation of left atrial pressure,pulmonary wedge pressure (venous pressure) which subsequently leads to PAH. 11le other conditions which lead to PVH are myocardial disorders like myocardial infarction, myocarditis and cardiomyopathies. These disorders lead to left ventricular failure, pulmonruy venous congestion and secondary PAH.
PAH Caused by Left to Right Shunts
This category includes large number of children or adults developing PAH secondary to congenital heart disease - left to right shunt lesions like atrial septal del'ect (ASD),ventricular septal defect (VSD) or patent ductus arteriovenous (PDA). In these conditions the volume overloading of the heart leads to increase in pulmonary blood flow and subsequent development of secondnry PAH. This group is also called as hyperkinetic PAH.
PAH Associated with Disorders of the Respiratory System or Hypoxen~ia In this category, the predominant cause is inadequate oxygenation of arterial blood as a result of either lung disease, impaired control of breathing or residence at high altitude. In this category, the increase in mean pulmonary artery pressure is generally modest (< 35 mm Hg). The survival in this group depends on tile severity of pulmonary disease rather than puln~onary haemodynainics. In native residents who develop PAH at high altitude, relocation to sea level rapidly ilnproves the PAH. PAH secondary to lung disease is usually refel~ed as cor pulmonale and will be discussed in details subsequently.PAH Caused by Thrombotic or Embolic Disease As described e&-lier some patients of PE can develop chronic tl~rornboembolic PAH due to proxitnal organized clot in major pulmonary arteries. Tllcse patients at times closely resemble PPH and the distinction is necessary as this group of patients can benefit from surgical pulmonary endarterectomy.PAH Caused by Diseases Affecting the Pulmonary Vasculature This category involved PAH stemming from inflammatoiy processes or mechanical obstruction (e.g., schistosomiasis, sarcoidosis). Lung biopsy may be needed to establish diagnosis of these conditions.
Clinical Features
The symptoms in patients with secondary PAH inay reflect the undellying cause or may be indistinguishable from those seen in PPH.In patients with PVH history suggestive of left heart failure (noctural dyspnea,orthopnea, pullnonary oedema) can be present. In congenital heart disease left to sight shunts (e.g. ASD, VSD, PDA) history of recurrent respiratoiy infections, failure to thrive and growth retardation may be there. History of chronic obstructive or restrictive lung disease may be present in those with cor pulmonale. Hislory of DVT or PE may be a pointer to thromboeinbolic PAH.The physical findings in secondary PAH are usually mixed and reflect the findings of primary cause and of PAH. The most sensitive sign for PAH is an accentuated pulmonary component of 52, which also may be palpable in the pulrnonic area, and .right ventricular lift of the sternum may be seen, With very high PAP, characteristic Idiastolic and systolic murnlurs of pulmonary valvular and tricuspid valvular regurgitation may be heard together with a systolic ejection sound and right ventricular S3. Elevation of jugular venous pressure, hepatornegaly and peripheral edema are seen when congestive cardiac failure supervenes.There may be findings of an underlying cause like valvular heart disease (mitral stenosis or mitral regurgitation) or shunt like ASD, VSD or PDA. There may be underlying signs of chronic lung disease in patients with cor pulmonale. .
Investigations
1) X-ray Clzest: X-ray chest provides valuable infoinlation both about presence of PAH and its cause. In general prominence and dilatation of main pulmonary artery segment and right and left pulmonary asteiies indicates PAH, Enlargement of left atrium and signs of pbln~onary venous bypertension point to mitiaa1 stenosis or a myocardial disease. In patients with shunt lesions, increased shunt vascularity may be seen on chest X-ray. Pathology in lungs in form of fibrosis, cavitation and emphysema may point to cor pulmonale.
2) Electrocardiogram (ECG): ECG may show light atsial enlargement (RAE), right axis deviation (RAD), right ventricular hypertrophy (RVH), rSR pattern,incomplete or complete right bundlc branch block (RBBB) and ST-T changes as a reflection of PAH. The degree of PAH determines the ECG changes and ECG may be non diagnostic or normal in mild or moderate PAH. Presence of left atrial enlargement (LAE), left ventricular 11ypertl.ophy (LVH), or left bundle branch block (LBBB) are strong pointers to disease in the left side of the heart. Atiial fibrillation (AF) is coniinoil in mitral stenosis.
3 ) Echocardiography: Echocardiography is the most valuable investigation for evaluation of a patient with PAH. A complete echocardiography study (M mode,2 DE, Doppler) is recommended for conlplete diagnosis. Echocardiography provides information both about presence and degree of PAH and its cause. PAH is diagnosed by enlargement of right heast chambers, estimation of PA pressure and by Doppler deinonstration of tiicuspid or pulmonary regurgitation.The demonstration of valvular, myocardial or shunt lesions provides accurate diagnosis of cause of PAH. Figure 5 shows demonstsation of large thron~bus in pulmonary artery in a patient with chronic thrombo embolic PAH.
4 ) Cardiac Catheterization and ~ n ~ i o ~ r a The need h ~ : for cardiac ,catheterization and angiography for diagnosing presence of PAH and for deterrnihtion o i its cause has considerably reduced in today's era when echocardiograpl-ly and other newer techniques ase available. Cardiac catheterization and haemodynamic studies are required rarely for calculation ol' pulmonary vascular resistance, shunt ratios and lor drug testing.
5 ) Other Tests: Tests like CT, CTPA, MRA, VQ scan are required to m'ke diagnosis of thsomboembolic PAH or lung disorders. Puln~onary filnction test are often useful for diagnosing restrictive or obstructive lung disorders.
Management
The management of PAH usually depends on the underline cause. In patients with PVH the underlying valve disease needed to be corrected. If LV dysfunction has caused the PAH then appropriate therapy with nitrates, diurelics, ACE inhibitors is required. Shunt lesions require prompt closure of defects by surgery or'devices to reduce and reverse PAH, The PAH secondary to hypoxemia, hypoventilation usually responds to oxygen therapy. The management of PPH and cor pulmonale will be discussed in details in subsequent sections.
Digoxin and diuretics are often utilized when RV failure and congestive symptoms develop. There are no specific agents to reduce PA pressure in secondary PAH.Prostanoids, endothelin receptor antagoilists and phosphodiestrase inhibitors are currently being investigated.
1)The first calegoiy includes patients of PAH without any identifiable cause or so-called priinaiy pulinonary hypertension (PPH). This group will be discussed subsequently. In situations where a cause can be identified the condition is called as secondary PAH.Secondary PAH is inore common than primruy variety and the various causes are shown in Table .
2) Secondary causes,
3) Pulmonary venous hypertension,
4) Left to right shunt lesions,
5) Disorders of respiratory system or hypoxemla,
6) Thrombotic or embolic diseases,
7) Diseases of pulmonary vasculature, and
6 ) Others.
Pulmonary Venous Hypertension (PVH)
This category consists predominantly of left sided valvular or myocardial diseases.The common valvular lesions which produce PVH include mitral stenosis, mitralm regurgitation, mixed mitral valve disease and also aortic valve disease. The initial hemodynamic abnormality in all these conditions is elevation of left atrial pressure,pulmonary wedge pressure (venous pressure) which subsequently leads to PAH. 11le other conditions which lead to PVH are myocardial disorders like myocardial infarction, myocarditis and cardiomyopathies. These disorders lead to left ventricular failure, pulmonruy venous congestion and secondary PAH.
PAH Caused by Left to Right Shunts
This category includes large number of children or adults developing PAH secondary to congenital heart disease - left to right shunt lesions like atrial septal del'ect (ASD),ventricular septal defect (VSD) or patent ductus arteriovenous (PDA). In these conditions the volume overloading of the heart leads to increase in pulmonary blood flow and subsequent development of secondnry PAH. This group is also called as hyperkinetic PAH.
PAH Associated with Disorders of the Respiratory System or Hypoxen~ia In this category, the predominant cause is inadequate oxygenation of arterial blood as a result of either lung disease, impaired control of breathing or residence at high altitude. In this category, the increase in mean pulmonary artery pressure is generally modest (< 35 mm Hg). The survival in this group depends on tile severity of pulmonary disease rather than puln~onary haemodynainics. In native residents who develop PAH at high altitude, relocation to sea level rapidly ilnproves the PAH. PAH secondary to lung disease is usually refel~ed as cor pulmonale and will be discussed in details subsequently.PAH Caused by Thrombotic or Embolic Disease As described e&-lier some patients of PE can develop chronic tl~rornboembolic PAH due to proxitnal organized clot in major pulmonary arteries. Tllcse patients at times closely resemble PPH and the distinction is necessary as this group of patients can benefit from surgical pulmonary endarterectomy.PAH Caused by Diseases Affecting the Pulmonary Vasculature This category involved PAH stemming from inflammatoiy processes or mechanical obstruction (e.g., schistosomiasis, sarcoidosis). Lung biopsy may be needed to establish diagnosis of these conditions.
Clinical Features
The symptoms in patients with secondary PAH inay reflect the undellying cause or may be indistinguishable from those seen in PPH.In patients with PVH history suggestive of left heart failure (noctural dyspnea,orthopnea, pullnonary oedema) can be present. In congenital heart disease left to sight shunts (e.g. ASD, VSD, PDA) history of recurrent respiratoiy infections, failure to thrive and growth retardation may be there. History of chronic obstructive or restrictive lung disease may be present in those with cor pulmonale. Hislory of DVT or PE may be a pointer to thromboeinbolic PAH.The physical findings in secondary PAH are usually mixed and reflect the findings of primary cause and of PAH. The most sensitive sign for PAH is an accentuated pulmonary component of 52, which also may be palpable in the pulrnonic area, and .right ventricular lift of the sternum may be seen, With very high PAP, characteristic Idiastolic and systolic murnlurs of pulmonary valvular and tricuspid valvular regurgitation may be heard together with a systolic ejection sound and right ventricular S3. Elevation of jugular venous pressure, hepatornegaly and peripheral edema are seen when congestive cardiac failure supervenes.There may be findings of an underlying cause like valvular heart disease (mitral stenosis or mitral regurgitation) or shunt like ASD, VSD or PDA. There may be underlying signs of chronic lung disease in patients with cor pulmonale. .
Investigations
1) X-ray Clzest: X-ray chest provides valuable infoinlation both about presence of PAH and its cause. In general prominence and dilatation of main pulmonary artery segment and right and left pulmonary asteiies indicates PAH, Enlargement of left atrium and signs of pbln~onary venous bypertension point to mitiaa1 stenosis or a myocardial disease. In patients with shunt lesions, increased shunt vascularity may be seen on chest X-ray. Pathology in lungs in form of fibrosis, cavitation and emphysema may point to cor pulmonale.
2) Electrocardiogram (ECG): ECG may show light atsial enlargement (RAE), right axis deviation (RAD), right ventricular hypertrophy (RVH), rSR pattern,incomplete or complete right bundlc branch block (RBBB) and ST-T changes as a reflection of PAH. The degree of PAH determines the ECG changes and ECG may be non diagnostic or normal in mild or moderate PAH. Presence of left atrial enlargement (LAE), left ventricular 11ypertl.ophy (LVH), or left bundle branch block (LBBB) are strong pointers to disease in the left side of the heart. Atiial fibrillation (AF) is coniinoil in mitral stenosis.
3 ) Echocardiography: Echocardiography is the most valuable investigation for evaluation of a patient with PAH. A complete echocardiography study (M mode,2 DE, Doppler) is recommended for conlplete diagnosis. Echocardiography provides information both about presence and degree of PAH and its cause. PAH is diagnosed by enlargement of right heast chambers, estimation of PA pressure and by Doppler deinonstration of tiicuspid or pulmonary regurgitation.The demonstration of valvular, myocardial or shunt lesions provides accurate diagnosis of cause of PAH. Figure 5 shows demonstsation of large thron~bus in pulmonary artery in a patient with chronic thrombo embolic PAH.
4 ) Cardiac Catheterization and ~ n ~ i o ~ r a The need h ~ : for cardiac ,catheterization and angiography for diagnosing presence of PAH and for deterrnihtion o i its cause has considerably reduced in today's era when echocardiograpl-ly and other newer techniques ase available. Cardiac catheterization and haemodynamic studies are required rarely for calculation ol' pulmonary vascular resistance, shunt ratios and lor drug testing.
5 ) Other Tests: Tests like CT, CTPA, MRA, VQ scan are required to m'ke diagnosis of thsomboembolic PAH or lung disorders. Puln~onary filnction test are often useful for diagnosing restrictive or obstructive lung disorders.
Management
The management of PAH usually depends on the underline cause. In patients with PVH the underlying valve disease needed to be corrected. If LV dysfunction has caused the PAH then appropriate therapy with nitrates, diurelics, ACE inhibitors is required. Shunt lesions require prompt closure of defects by surgery or'devices to reduce and reverse PAH, The PAH secondary to hypoxemia, hypoventilation usually responds to oxygen therapy. The management of PPH and cor pulmonale will be discussed in details in subsequent sections.
Digoxin and diuretics are often utilized when RV failure and congestive symptoms develop. There are no specific agents to reduce PA pressure in secondary PAH.Prostanoids, endothelin receptor antagoilists and phosphodiestrase inhibitors are currently being investigated.
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