Pathophysiological consequences of pulmonary hypertension

Exertional shortness of breath may represent the first discrete clinical symptom of pulmonary hypertension. Dyspnea at rest and pathologic heart sounds, particularly a loud secondary pulmonary sound, indicate advanced-stage pulmonary hypertension. Under experimental conditions, pulmonary artery pressures increase when more than two-thirds of the vascular bed is occluded. In patients with a thromboembolic episode, a 70 per cent obstruction of the vascular bed is still compatible with life.

When pulmonary hypertension results from increased pulmonary blood flow or pulmonary venous congestion, such as with a ventricular septal defect, the right heart slowly adapts to the slow rise in vascular resistance and responds by hypertrophy. When pulmonary artery and systemic pressures eventually equalize, the left-to-right direction of blood flow through the shunt reverses (Eisenmenger syndrome) and a further increase in vascular resistance due to hypoxemia results in right ventricular failure. Provided that the alveolar capillary bed is not affected by the disease process, oxygenation is primarily restricted not by a diffusion limitation but by the inadequate response of cardiac output to increased oxygen consumption. When the process is diffuse and the pulmonary capillaries are also involved, a variety of factors, not exclusively a limitation of diffusion capacity, reduce blood oxygenation.

In the late course of the chronic disease, impairment in right ventricular function owing to the increase in right ventricular afterload leads to a reduction in contractility, thus lowering cardiac output and oxygen delivery. Insufficiency of the tricuspid valve and regurgitation combined with high central venous pressures are typical clinical findings. The combination of reduced arterial oxygen content, critical tissue perfusion of right ventricular muscle, and a further decrease in coronary blood flow eventually induces right ventricular failure.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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