Pulmonary hypertension

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Pulmonary hypertension (PH) is a condition characterized by a sustained elevation of mean pulmonary artery pressure to > 25 mm Hg at rest or > 30 mm Hg with exercise.

Pulmonary hypertension is classified by the World Health Organization into five major categories.

    • Group Ipulmonary hypertension is referred to as pulmonary arterial hypertension (PAH).
      • PAH requires three findings:
        • PH as defined above,
        • a mean pulmonary capillary wedge pressure > 15 mm Hg, and
        • an elevated pulmonary vascular resistance > 3 Wood units.
      • Group I encompasses idiopathic (primary), familial, and venous (or capillary)-related pulmonary hypertension.
          • Idiopathic PAH(previously termed primary pulmonary hyperten- sion or PPH)
            • most common in young females (female:male ratio is 2:1).
            • Mean age of onset is 36 years.
          • Familial PAH refers to inheritable disorders.
            • Other causes of PH in this group include collagen vascu- lar disease,       congenital systemic-to-pulmonary shunts, portal hypertension, HIV       infection, drugs or toxins (e.g., anorexigens), glycogen storage disease,      hereditary hemorrhagic telangiectasia,andhemoglobinopathies.
          • Venous or capillary-related PH includes veno-occlusive disease and pulmonary–capillary hemangiomatosis.
        • Group II is PH from pulmonary venous hypertension as a result of left-sided atrial or ventricular heart disease or left-sided valvular (mitral or aortic) heart disease.
        • Group III encompasses PH associated with chronic hypoxemia,as in COPD, interstitial lung disease, sleep-disordered breathing, alveolar hypoventilation disorders, or chronic exposure to high altitudes.
        • Group IV PH is due to chronic thrombotic disease, embolic disease, or both.
        • Group V is the miscellaneous classification of PH.

      It includes sarcoidosis, pulmonary Langerhans’-cell histiocytosis,       lymphangiomatosis, and external compression of the pulmonary vessels (from      adenopathy, tumor, etc.)

      Pathology and Pathophysiology

        • The pulmonary circulation is normally a low-resistance, high-compliance vascular system.
        • The pulmonary circulation is the only organ to receive 100% of the cardiac output.
        • Pulmonary blood flow can increase four to five times its baseline during exercise or times of stress, by increasing CO and decreasing pulmonary vascular resistance (PVR).
        • The pathologic changes that occur in PAH are vasoconstriction, smooth muscle and endothelial cell proliferation, in situ thrombosis, and plexiform lesions in end-stage PAH.
        • Endothelin-1 is the most powerful vasoconstrictor found endogenously.

        Clinical Features, Diagnosis, and Clinical Course

        • Fatigue appears to be the most common symptom and is present in approximately 60% of  patients at diagnosis.
        • Dyspnea occurs in 60% of patients when they initially present but is encountered by all as the  disease progresses.
        • Syncopeandangina,particularlywithexertion,arelatemanifestationsofthedisease,suggest ing the presence of severe pulmonary hypertension causing reduced cardiac output.
        • On physical exam, there is a loud second heart sound (P2), jugular venous distension (JVD), hepatomegaly, lower-extremity edema, and ascites, and there may be a murmur of pulmonary and/or tricuspid regurgitation.
        • An echocardiogram is the best screening test for PH, but to make the diagnosis, a right heart catheterization must be performed.
        • Chestradiographymayshowperipheralpulmonaryhypovascularity(“pruning”),prominent proximal pulmonary arteries, and right ventricular enlargement into the retrosternal space.
        • The electrocardiogram showsright axis deviation, right atrial enlargement, right ventricular hypertrophy, and right ventricular strain.
        • With an echocardiogram, the right ventricle and pulmonary artery pressures can be esti- mated, right ventricular and left atrial enlargement are seen, and tricuspid and pulmonary valve regurgitation are seen with color Doppler. However, the right ventricle and pulmonary pressures are only estimated and may not be accurate.
        • A right heart catheterization (Swan–Ganz catheter) is required to confirm a suspected diagnosis of PH.

        Prognosis

        • Historically, the prognosis for patients with PAH has been poor, with an estimated mediansurvival of 2.8 years

        Therapy

          • Conventional medical therapy for pulmonary hypertension has centered on the use of supple- mental oxygen (with goal oxygen saturation >90%), diuretics, anticoagulants (warfarin with goal international normalized ratio [INR] between 1.5 and 2.5), and vasodilators.
          • Diuretics must be used with caution in patients with higher right-sided pressures to avoid significant reductions in cardiac preload that could further reduce cardiac output.
          • Anticoagulation is recommended to achieve an INR of 1.5–2.5 times that of normal controls.
          • Digoxin is always recommended for use in patients who have pulmonary hypertension with evidence of left ventricular dysfunction.
          • Calcium channel blockers used include nifedipine (dose range, 30–240 mg/day) anddiltiazem (120–900 mg/day).
          • The prostacyclin derivatives include intravenous (IV) epoprostenol, inhaled iloprost, and subcutaneous, intravenous, or inhaled treprostinil.
          • Epoprostenol is currently the most effective therapy but has a short half-life and must be administered continuously via an IV infusion. Side effects may limit its use and include flushing, headache, nausea, vomiting, diarrhea, jaw pain, hypotension, and delivery-site complications.
          • Iloprost is given via inhalation, but its half-life is short, and so it requires six to nine inhalations per day.
          • Treprostinil is a longer- acting prostacyclin analog, is infused subcutaneously or intravenously, and is complicated by site infusion pain that can be severe enough to cause discontinuation.
          • The endothelin receptor antagonists include bosentan and ambrisentan, both of which are administered orally
          • Sildenafil and tadalafil comprise the phosphodiesterase type-5 inhibitors that have been approved for the treatment of PAH.
              • They work in the same pathway as exogenous nitric oxide by increasing cyclic GMP and causing vasodilation.


            Pulmonary Hypertension – What Is Pulmonary Hypertension Video.mp4
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