Patients with PPH are susceptible to mild hypoxemia that is aggravated by exercise because of superimposed hypoxic pulmonary vasoconstriction. It has been suggested that significant hypoxemia is less common in PPH since these patients tend not to have significant ventilation-perfusion abnormalities. We looked at the prevalence and predisposing variables in PPH patients with significant hypoxemia.
Charts of PPH patients followed in the pulmonary hypertension clinic at our institution were reviewed for demographics, exercise capacity, exercise induced hypoxemia, hemodynamic variables, and pulmonary function test results.
Thirty-two patients (age 46.4±10.7; 23F/9M; NYHA III/IV) with PPH (6 with familial PPH) followed in our clinic for 23.5±22.4 months were included.
ParameterO2 requiring (N=16)Non-O2 requiring (N= 16)P valueAge (years)48.6±10.944.1±10.20.2Sex11F/5M12F/4M0.7Etiology: -Familial -Sporadic4 (12.5%) 12 (37.5%)2 (6.25%) 14 (43.75%)0.4Hypothyroidism5 (15.62%)0 (0%)0.02*ANA positive2 (6.25%)6 (18.75%).0.1Intra-cardiac shunt**5 (15.62%)1 (3.72%)0.1PFT abnormalities8 (25%)7 (21.9%)0.7MVO2-pre-therapy64.0±11.258.2±6.60.4% Sat-on therapy64.0±6.360.1±9.30.3DLCO53.5±22.170.4±15.40.02*Improvement in exercise capacity with therapy4%13.9 %0.6*
all secondary to PFO (MVO2: mixed venous oxygen saturation).There was no significant difference in NYHA functional class, RVSP by 2 D echocardiography, mean PAP, CO, or CI between those requiring O2 and those not requiring O2. Among O2 requiring patients, those having intra-cardiac shunts were found to have a DLCO of 51.6 ± 12.4 as compared to 54.36 ± 25.9 for those not having intracardiac shunts. (p=0.7)
A significant proportion of PPH patients may have exertional hypoxemia requiring oxygen supplementation. Clinically significant hypoxemia may develop in the absence of right to left shunting. A lower DLCO in the hypoxemic group without right to left shunting may indicate significant ventilation-perfusion abnormalities. Patients with familial PPH, and those with hypothyroidism were more likely to have significant exercise-induced hypoxemia requiring O2 therapy.
All patients with PPH should be assessed for exercise-induced hypoxemia.
S.A. Ismail, None.