Position in pulmonary vascular pathology
Pulmonary vascular pathology accompanies a wide variety of diseases and includes several major syndromes. In addition to pulmonary hypertension, this group encompasses pulmonary edema, adult respiratory distress syndrome (ARDS), and pulmonary embolism (PE). Hypertension itself is traditionally divided into two broad categories: primary (idiopathic) and secondary, developing against the background of pre-existing conditions. Regardless of the form, the key hemodynamic consequence is the overload of the right heart chambers.
Primary pulmonary hypertension syndrome
The primary form is extremely rare in clinical practice. The main risk group includes children, as well as women aged 20 to 40 years. Although the exact etiology of the disease remains unknown, its pathogenesis is associated with several probable factors:
- Autoimmune reactions. There is substantial evidence linking the syndrome to systemic diseases. Pulmonary arteriopathy frequently develops in patients with scleroderma, rheumatoid polyarteritis, Hashimoto's thyroiditis, and primary biliary cholangitis. Notably, fibrinoid necrosis is detected within the walls of the pulmonary arteries.
- Genetics. The pathology is classified as a polygenic disease. Familial cases with both dominant and recessive inheritance patterns have been described in the literature. The role of environmental factors is also not excluded.
- Hormonal influence. The association with hormones is supported by the fact that the disease frequently affects women of reproductive age, with pregnancy or oral contraceptive use acting as potential triggers.
- Congenital factors. The syndrome is often diagnosed in patients with congenital malformations of the heart and the pulmonary artery itself.
Morphological pattern of the primary form
Macroscopic and microscopic changes strictly depend on the caliber of the affected vessels. Pronounced atherosclerosis develops in the large branches of the pulmonary artery. At the same time, medium and small branches undergo fibrosis and marked muscular hypertrophy.
At the microscopic level, a specific symptom complex known as plexogenic pulmonary arteriopathy develops. The spectrum of these morphological changes clearly corresponds to the stages of disease progression:
- The process begins with the muscularization of the pulmonary artery wall.
- Migration of dark muscle cells directly into the vascular intima occurs.
- Intimal cells begin to actively proliferate and transform into myofibroblasts.
- Characteristic plexogenic structures are formed.
- Vessel walls undergo dilatation, inevitably leading to the formation of microaneurysms.
- At the final stages, microaneurysms rupture, and fibrinoid necrosis develops in the tissue.
Secondary pulmonary hypertension syndrome
The secondary form is always a complication of other pathological processes. Chronic lung diseases, chronic left ventricular heart failure, and recurrent episodes of pulmonary embolism (PE) play a leading role in classical etiology. However, in recent years, the association of secondary hypertension with the progression of chronic liver diseases and chronic viral infections has become increasingly relevant.
Morphological changes in the lung tissue in the secondary syndrome boil down to the development of pulmonary sclerosis—the pathological proliferation of connective tissue. Furthermore, if the disease is accompanied by venous congestion, pulmonary vasculitis, or embolism, hemosiderosis (deposition of an iron-containing pigment) joins the morphological picture.
Briefly: answers to topical questions
What mean pulmonary artery pressure values at rest define the presence of pulmonary hypertension?
The presence of pulmonary hypertension is defined by a mean pulmonary artery pressure ≥ 25 mmHg at rest. Normally, this parameter is ≤ 20 mmHg. Depending on other hemodynamic parameters, the following variants are distinguished:
- Pre-capillary pulmonary hypertension — mean pressure ≥ 25 mmHg, pulmonary artery wedge pressure ≤ 15 mmHg, pulmonary vascular resistance ≥ 3 Wood units.
- Post-capillary pulmonary hypertension — mean pressure ≥ 25 mmHg, pulmonary artery wedge pressure > 15 mmHg.
What specific gene mutations are associated with the familial form of primary pulmonary hypertension?
Mutations in the BMPR2 gene and mutations in other candidate genes are associated with the hereditary form of pulmonary arterial hypertension. Sources also indicate that familial cases may be inherited in a dominant or recessive manner; the disease belongs to polygenic pathologies.
Which drug classes are used for targeted therapy of pulmonary hypertension?
Endothelin receptor antagonists and calcium channel blockers are used for the specific therapy of pulmonary arterial hypertension. The mechanism of action of these drugs aims to reduce pulmonary vascular resistance, which improves the filling of the left heart chambers.
- Endothelin receptor antagonists — include ambrisentan, bosentan, macitentan, and tezosentan (an endothelin receptor blocker).
- Calcium channel blockers — used in patients with a long-term response to this drug class.
Therapy is selected strictly on an individual basis, as there is currently no curative medication.
Which ECG signs indicate the development of cor pulmonale and right ventricular hypertrophy?
Rightward deviation of the electrical axis of the heart (right axis deviation) and specific changes in chest leads indicate the development of cor pulmonale and right ventricular hypertrophy. Diagnosis is possible with a significant increase in the muscle mass of the right ventricle. The main ECG signs of right ventricular hypertrophy:
- Increase in the R wave — in leads V1, V2 > 7 mm.
- Increase in the S wave — in leads V5, V6 > 7 mm.
- Index — sum of RV1 + SV5 (V6) > 11 mm.
Additionally, a negative T wave and ST-segment depression in V1, as well as ST elevation in V5–V6, are recorded. With concomitant right atrial hypertrophy, a tall, peaked P wave (height > 2.0–2.5 mm) is detected in leads II, III, aVF.
What is the pathogenetic mechanism of pulmonary hemosiderosis development in secondary pulmonary hypertension?
The pathogenetic mechanism of pulmonary hemosiderosis development in secondary pulmonary hypertension is based on chronic venous congestion. The process includes the following stages:
- Hyperemia — engorgement of venous vessels with blood.
- Diapedesis — exit of erythrocytes from the vascular bed into the lung tissue.
- Pigment formation — engulfment of erythrocytes by macrophages with the formation of hemosiderin inside siderophages (hemosiderophages).
SH-ferritin, which is part of hemosiderin, exerts a vasoparalytic effect—thereby aggravating venous congestion—and a sclerogenic effect, stimulating the diffuse proliferation of connective tissue. Macroscopically, the lungs acquire a dense consistency and a brown color, which is classified as brown induration of the lungs (induratio fusca pulmonum).
To quickly recall the factors in the development of primary pulmonary hypertension, use the acronym AAGV (in Russian): Autoimmune reactions, Genetics, Gormones (hormonal background), Vascular malformations (congenital defects).
Class and exam questions
Who is in the primary risk group for primary pulmonary hypertension?
The disease predominantly affects children and women of reproductive age (20 to 40 years). This indirectly confirms the role of hormonal background in the pathogenesis.
What is plexogenic pulmonary arteriopathy?
This is a specific cascade of microscopic vascular changes in primary hypertension. It includes arterial muscularization, the formation of plexogenic structures, the appearance of microaneurysms, and culminates in fibrinoid necrosis.
What changes occur in lung tissue during secondary hypertension?
Pulmonary sclerosis develops in the lung tissue. If the process occurs against the background of venous congestion, vasculitis, or embolism, hemosiderosis additionally arises.
How does pulmonary hypertension affect the heart?
Permanently elevated resistance in the pulmonary circulation forces the right ventricle to work harder. This causes its compensatory hypertrophy and the development of cor pulmonale (cor pulmonale).
What else to study on this topic
- Pulmonary edema as a syndrome of vascular pathology
- Adult respiratory distress syndrome (ARDS)
- Pulmonary embolism (PE)
- Pathogenesis and developmental stages of cor pulmonale
- Morphology of hemosiderosis and pulmonary sclerosis
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