Exercise capacity reflects airflow limitation rather than hypoxaemia in patients with pulmonary arteriovenous malformations.

BACKGROUND: Pulmonary arteriovenous malformations (PAVMs) generate a right-to-left shunt. Impaired gas exchange results in hypoxaemia and impaired CO2 clearance. Most patients compensate effectively but some are dyspneic, and these are rarely the most hypoxaemic. AIM: To test degrees of concurrent pathology influencing exercise capacity. DESIGN: Replicate, sequential single centre, prospective studies. METHODS: Cardiopulmonary exercise tests (CPETs) were performed in 26 patients with PAVMs, including individuals with and without known airflow obstruction. To replicate, relationships were tested prospectively in an independent cohort where self-reported exercise capacity evaluated by the Veterans Specific Activity Questionnaire (VSAQ) was used to calculate metabolic equivalents (METs) at peak exercise (n = 71). Additional measurements included oxygen saturation (SpO2), forced expiratory volume in 1 s (FEV1), vital capacity (VC), fractional exhaled nitric oxide (FeNO), haemoglobin and iron indices. RESULTS: By CPET, the peak work rate was only minimally associated with low SpO2 or low arterial oxygen content (calculated as CaO2=1.34 × SpO2 × haemoglobin), but was reduced in patients with low FEV1 or VC. Supranormal work rates were seen in patients with severe right-to-left shunting and SpO2 < 90%, but only if FEV1 was >80% predicted. VSAQ-calculated METS also demonstrated little relationship with SpO2, and in crude and CaO2-adjusted regression, were lower in patients with lower FEV1 or VC. Bronchodilation increased airflow even where spirometry was in the normal range: exhaled nitric oxide measurements were normal in 80% of cases, and unrelated to any PAVM-specific variable. CONCLUSIONS: Exercise capacity is reduced by relatively mild airflow limitation (obstructive or restrictive) in the setting of PAVMs.

Orthodeoxia and postural orthostatic tachycardia in patients with pulmonary arteriovenous malformations: a prospective 8-year series.

Postural changes in 258 patients with pulmonary arteriovenous malformations (PAVMs) reviewed between 2005 and 2013 were evaluated prospectively using validated pulse oximetry methods. Of the 257 completing the test, 75 (29%) demonstrated orthodeoxia with an oxygen saturation fall of at least 2% on standing. None described platypnoea (dyspnoea on standing). The heart rate was consistently higher in the erect posture: 74 (29%) had a postural orthostatic tachycardia of ≥20 min(-1), and in 25 (10%) this exceeded 30 min(-1). Orthostatic tachycardia was more pronounced in PAVM patients than controls without orthodeoxia (age-adjusted coefficient 5.5 (95% CIs 2.6, 8.4) min(-1), p<0.001). For PAVM patients, the age-adjusted pulse rise was 0.79 min(-1) greater for every 1% greater drop in oxygen saturation on standing (p<0.001). In contrast to the postural orthostatic tachycardia syndrome, in this population, there was a trend for more pronounced orthostatic tachycardia to be associated with better exercise tolerance.

Embolisation of pulmonary arteriovenous malformations: no consistent effect on pulmonary artery pressure.

Increasing evidence supports the use of embolisation to treat pulmonary arteriovenous malformations (AVMs). Most pulmonary AVM patients have hereditary haemorrhagic telangiectasia (HHT), a condition that may be associated with pulmonary hypertension. The current authors tested whether pulmonary AVM embolisation increases pulmonary artery pressure (P(pa)) in patients without baseline severe pulmonary hypertension. P(pa) was measured at the time of pulmonary AVM embolisation in 143 individuals, 131 (92%) of whom had underlying HHT. Angiography/embolisation was not performed in four individuals with severe pulmonary hypertension, whose systemic arterial oxygen saturation exceeded levels usually associated with dyspnoea in pulmonary AVM patients. In 143 patients undergoing pulmonary AVM embolisation, P(pa) was significantly correlated with age, with the most significant increase occurring in the upper quartile (aged >58 yrs). In 43 patients with repeated measurements, there was no significant increase in P(pa) as a result of embolisation. In half, embolisation led to a fall in P(pa). The maximum rise in mean P(pa) was 8 mmHg: balloon test occlusion was performed in one of these individuals, and did not predict the subsequent rise in P(pa) following definitive embolisation of the pulmonary AVMs. In the present series of patients, which excluded those with severe pulmonary hypertension, pulmonary artery pressure was not increased significantly by pulmonary arteriovenous malformation embolisation.