Pulmonary hypertension

Background

*Pulmonary Hypertension (PH) = mean PA pressure >25mmHg assessed by right heart cath

• PH divided into 5 groups:
  • Group 1 PAH: Idiopathic pulmonary arterial hypertension, formerly called primary PH
  • Group 2 PH: PH due to left heart disease (systolic/diastolic dysfunction and valvular heart dz)
  • Group 3 PH: PH due to lung diseases or various causes of hypoxemia, such as COPD, ILD, or sleep-disordered breathing
  • Group 4 PH: PH due to chronic thromboembolic disease
  • Group 5 PH: PH of unclear multifactorial mechanisms (myeloproliferative dz, sarcoidosis, glycogen storage dz, etc)

Etiology

• PAH can be heritable, idiopathic, or associated with connective tissue disease, HIV, portal HTN, congenital heart dz, schistosomiasis, chronic hemolytic anemia
• PH can be due to lung disease, left heart disease, chronic exposure to high altitudes, chronic thromboembolic disease, myeloproliferative disorders, sarcoidosis, vasculitis, glycogen storage disease, Gaucher disease, chronic renal failure on dialysis

Diagnosis

• Physical exam:
  • Consider in undifferentiated patients with dyspnea, fatigue, syncope (late PH finding), chest pain, palpitations, LE edema
  • Look for JVD, hepatomegaly, ascites, edema, stigmata of liver failure
• ECG findings (similar to acute pulmonary embolism):
  • Right axis deviation
  • Evidence of right heart strain
  • S1Q3T3
  • Right ventricular hypertrophy
    • Large R waves in precordial leads
  • Tachyarrhythmias (aflutter or afib)
• Radiologic findings:
  • CXR:
    • RA enlargement (obliteration of retrosternal space on lateral CXR)
    • Prominent pulmonary vasculature (congestion)
    • PA dilation
  • CT Chest:
    • Pulmonary artery > ascending aorta suggests PH
    • Pulmonary artery diameter greater than 30 mm suggest PH
    • Right heart enlargement
  • Echocardiogram:
    • RVH, RV dilatation and hypokinesis
    • RV close to LV size (+/- septal flattening/bowing)
    • Tricuspid valve regurgitation

Chronic Therapies

Prostacyclins

Mechanisms of action: vasodilatation, inhibit platelet aggregation

• Epoprostenol, Iloprost, Treprostinil, Beraprost
  • Complications include acute decompensation if stopped abruptly, diarrhea, edema, headache

Phosphodiesterase Type 5 (PDE5) Inhibitors

Mechanism of Action: vasodilation, increases RV contractility

• Sildenafil
• Complications include hypotension with administration of nitrates, flushing, epistaxis, headache

Endothelin receptor antagonists

Mechanism of Action: vasodilation via vascular modulation modulation

• Bosentan, Ambrisentan
  • Complications include liver failure, supratherapeutic INR,
• Patients also usually taking digoxin, coumadin, diuretics, home O2. RARELY are they on CCB only if responsive during cath. Consider line infections as complication to chronic infusions.

Acute Treatment for PAH crisis

PH patients do not tolerate rapid changes in hemodynamics well, all therapies should be instituted with caution.

Optimize Circulation

1. Optimize(usually reduce) RV preload:
   1. Pts usually euvolemic or hypervolemic, rarely need IVF
   2. Diuretics to treat RV failure:
      1. Furosemide 20-40mg IV
      2. Furosemide drip @ 5-20mg/hr
   3. If suspect sepsis or hypovolemia, small (250-500cc) NS challenge to assess fluid responsiveness. If not responsive to IVF challenge, start norepinephrine (MAP > 65 mmHg).
2. Increase cardiac output:
   1. Once MAP >65 mmHg, start low dose dobutamine (5-10mcg/kg/min)
   2. Improves inotropic support and theoretically decreases pulmonary vascular resistance
3. Reduce RV afterload:
   1. Avoid hypoxia, maintain O2 sat >90% (increases pulmonary vasoconstriction)
   2. Avoid hypercapnea (increases pulmonary vascular resistance)
   3. Avoid acidosis
4. Treat arrhythmias:
   1. SVT most common although(aflutter and afib occure equally)
   2. Treatment of aflutter is often more successful than afib
   3. Pts do not tolerate negative inotropy, deteriorate to RV failure

Do NOT rate control tachycardias, best to electrically cardiovert or attempt rhythm control with amiodarone

1. May require radiofrequency ablation
2. AVOID calcium channel blockers or beta blockers

Optimize Oxygenation

1. Intubated patients should be optimized to increased O2 delivery and minimize hypercapnea, maintain low tidal volumes and low PEEP as tolerated

Source

• Critical Decisions in Emergency Medicine, May 2013; 27(5)