PULMONARY HYPERTENSION

Pulmonary arterial hypertension (PAH) may be defined as a resting mean pulmonary artery pressure of >= 20 mmHg. (greater than 25 mmHg at rest or 30 mmHg after exercise; also diastolic pressure >8 mmHg)

Endothelin is thought to play a key role in the pathogenesis of PAH. It is more common in females and typically presents between the ages of 30-50 years. Pulmonary hypertension may of course develop secondary to chronic lung diseases such as COPD - PAH is diagnosed in the absence of this although certain factors increase the risk, including HIV, cocaine and anorexigens (e.g. fenfluramine). Around 10% of cases are inherited in an autosomal dominant fashion.

Features

• progressive exertional dyspnoea is the classical presentation

• other possible features include exertional syncope, exertional chest pain, ascites and/or peripheral oedema, hepatomegaly, cold extremities

• cyanosis

• clinical signs:

  • right ventricular heave: indicating right ventricular hypertrophy or dilatation
  • loud P2: early in the disease reflects increased pulmonary artery pressure and may be accompanied by a palpable P2 in severe cases. With advanced PAH there may be right ventricular failure leading to a soft S2
  • raised JVP with prominent 'a' waves: reflects increased resistance to right atrial emptying due to elevated right ventricular end-diastolic pressure. However, JVP is typically NOT elevated in many cases.
  • tricuspid regurgitation

  🩺 S1 + S2 (loud P2) + S3 + PSM loudest at the LLSE augmented by inspiration

Management

Management should first involve treating any underlying conditions, for example with anticoagulants or oxygen. Following this, it has now been shown that acute vasodilator testing is central to deciding on the appropriate management strategy. Acute vasodilator testing aims to decide which patients show a significant fall in pulmonary arterial pressure following the administration of vasodilators such as intravenous epoprostenol or inhaled nitric oxide.

If there is a positive response to acute vasodilator testing (a minority of patients)

• oral calcium channel blockers

If there is a negative response to acute vasodilator testing (the vast majority of patients)

• prostacyclin analogues: treprostinil, iloprost
• endothelin receptor antagonists
  • non-selective: bosentan
  • selective antagonist of endothelin receptor A: ambrisentan
• phosphodiesterase inhibitors: sildenafil

Patients with progressive symptoms should be considered for a heart-lung transplant.

Riociguat (Adempas) increases nitric oxide by stimulating guanylate cyclase; increases vasodilation by generating cGMP. (preg: cat. X)