Haemodynamic variables may distinguish pre- from post-capillary PH

By Eleanor McDermid, Senior medwireNews Reporter

Researchers have identified the haemodynamic variables that best distinguish between patients with idiopathic pulmonary arterial hypertension (PAH) and isolated post-capillary pulmonary hypertension (PH).

Patients identified as having idiopathic PAH by this means have a good chance of responding to prostacyclin treatment, the team reports, adding that targeted therapies are not currently recommended for patients with isolated post-capillary PH, due to lack of efficacy.

Irene Lang (Medical University of Vienna, Austria) and co-researchers found that mean pulmonary arterial wedge pressure (mPAWP) and diastolic pulmonary vascular pressure gradient (DPG) best distinguished between 38 patients with idiopathic PAH and 1209 with isolated post-capillary PH, identified from among 4363 patients undergoing diagnostic right heart catheterisation.

They had anticipated an mPAWP cutoff that was “lower than currently accepted”, but in fact they confirmed the previously proposed threshold of 12 mmHg. This distinguished between the two groups with a sensitivity of 99.4% and a specificity of 96.8%, with idiopathic PAH patients having values below the threshold.

At a cutoff of 7 mmHg, DPG distinguished between the patient groups with a sensitivity of 96.8% and a specificity of 100%, with idiopathic PAH patients having values at or above the threshold.

The transpulmonary gradient was the next-most accurate parameter, giving a sensitivity of 96.8% and a specificity of 96.7% at a cutoff of 22 mmHg. The accuracy of other parameters was lower, with pulmonary vascular resistance the most and mean right atrial pressure the least accurate.

Among 978 patients given prostacyclin treatment in four randomised trials, those with an mPAWP below 12 mmHg had significant improvements in seven haemodynamic parameters relative to those given placebo. By contrast, those with a higher mPAWP only improved their cardiac output, and by less than patients with lower mPAWP.

Likewise, patients with a DPG above 20 mmHg (chosen to maximise sensitivity) had significant haemodynamic improvements in response to active treatment, whereas those with a lower DPG did not.

Writing in CHEST, the researchers caution that their findings are only applicable to patients given prostacyclin treatment, saying that “validation of the algorithm is needed to ensure applicability for other ‘PAH-targeted therapies’.”

They add: “Our data substantiate the value of baseline and on-treatment hemodynamics for the clinical follow-up of patients with PAH.”

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