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What Does Pulmonary Hypertension Do To The Heart?

Pulmonary hypertension is defined as mean pulmonary arterial pressure measured by right heart catheterization ≥ 25 mmHg at rest. Pulmonary hypertension is an uncommon disorder occurs in people of all ages and races, probably affects around 1% of the global population.

Pulmonary hypertension causes numerous complications in the heart such as:

Right-sided heart enlargement and heart failure
Blood clots (Narrow arteries).
Arrhythmia (Irregular heartbeat)

Important Concept and Reason behind Right-Sided Heart Enlargement and Heart Failure, Blood Clots, and Arrhythmia

Arteries which carry oxygenated blood to the lung from heart become narrowed, making it very complex for blood to flow. These arteries are known as pulmonary arteries and the pressure increase in these arteries is referred as pulmonary hypertension. This abnormally high artery pressure cause stress in the right ventricle of the heart. These consequences increase in the size of the heart i.e. characterized by hyperplasia. Enlarged heart with abnormal right ventricles makes the affected individual more pathetic. It may lead to right heart failure because of its inability to pump the blood to the lungs.

Poor hemodynamics i.e. reduced blood flow and narrowed arteries are the first sign of the injury. It begins as remodeling on the layers of cells that forms the blood vessel of the lungs. The layer of cells interacts with the smooth muscle cells in the vessel wall and as a result, the smooth muscle contracts more than normal and narrows the vessel. Major resistance in pulmonary arteries, intimal hyperplasia, medial hypertrophy, adventitial proliferation, in situ thrombosis, and inflammation are the consequences of pathological remodeling. The cause of the remodeling is unclear although extensive research was done in pulmonary hypertension.

Multiple pathways are involved in the pathogenesis of PAH. The condition has an unequal proportion of vasoconstricting and vasodilating substances in the pulmonary arteries. vasoconstrictors thromboxane, endothelin, and serotonin substances are present in high proportion whereas, the synthesis of vasodilators such as prostacyclin, nitric oxide, and vasoactive intestinal polypeptide are seen in less percentage. This is the consequences of pulmonary artery vasoconstriction that contribute to pulmonary vascular dysfunction.

Right ventricular hypertrophy (RVH) occurs due to increased pulmonary vascular resistance (PVR). In maladaptive cases, it shows eccentric dilatation, increased fibrosis, and capillary rarefaction with a reduction in ejection fraction and cardiac output and elevation in filling pressures. In certain conditions, maladaptive RVH cause increase in aerobic glycolysis, fatty acid oxidation, and glutaminolysis. Whereas in adaptive RVH, it is characterized by concentric hypertrophy with minimal eccentric dilatation and fibrosis, maintains normal ejection fraction, cardiac output, and filling pressures.

One of the important factors contributes to maladaptive Right ventricular (RV) remodeling and metabolic changes are RV ischemia due to reduced right coronary artery epicardial flow and capillary rarefaction associated with PAH. There is more evidence exists that RV ischemia contributes to RV failure in PAH. RV failure is characterized by a decreased cardiac index (< 2.5 L/min/m2) and increased right-sided, cardiac filling pressures, including right atrial pressure (RAP) ≥ 8 mmHg. RV failure in PAH causes pedal edema, neck vein distension, abdominal fullness and exertional dyspnea.

PH in the more advanced cases shows symptoms even for mild activity or exercise. Irregular heartbeat (palpitations or strong, throbbing sensation), increased pulse, paleness or dizziness, continues shortness of breath and sometimes difficult to breathe at the rest time. Sometimes pulmonary hypertension can lead to bleeding because of injury in lungs and heart, and cause coughing up blood (hemoptysis), which is a potentially fatal complication.

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What Does Pulmonary Hypertension Do To The Heart?