Right atrial function could be prognostic in PAH

Dec 11 2015

By Eleanor McDermid, Senior medwireNews Reporter

Right atrial (RA) function is impaired in patients with pulmonary arterial hypertension (PAH) and may indicate right ventricular (RV) overload and failure, research suggests.

Study author Amil Shah (Brigham and Women’s Hospital, Boston, Massachusetts, USA) and colleagues note that RV failure is an important risk factor for death in PAH patients, but that RV function is hard to reliably assess.

The RA, by contrast, “is a simpler geometric structure”, they say, suggesting that RA dysfunction may be a useful noninvasive surrogate marker of RV failure and PAH prognosis.

They note that RA assessment was possible in 97% of the patients in their study, whereas assessment of RV function was only possible in 88%. The 65 patients with assessable RA echocardiographical images were an average of 50 years old and were drawn from a clinical trial of patients with advanced PAH.

Strain analysis showed that the PAH patients had significantly reduced RA longitudinal strain (27.1 vs 56.9%), peak longitudinal strain rate (1.4 vs 2.1%) and total emptying fraction (51 vs 66%), relative to 30 healthy controls of similar age. This indicated that they had reduced RA reservoir function – the phase concurrent with RV contraction.

PAH patients also had reduced conduit function (concurrent with rapid passive RV filling), indicated by significantly reduced RA early longitudinal strain rate, passive emptying fraction and ratio of passive-to-total emptying fraction.

By contrast, active function (RA contraction) was preserved, resulting in an increased active-to-total emptying fraction in PAH patients compared with controls, at 86% versus 66%. The researchers say this reflects a relatively greater contribution of active function to overall RV diastolic filling in PAH patients, “likely as a compensatory mechanism for the reduced passive conduit emptying”.

“These findings suggest that the loss of this compensatory mechanism, either because of atrial fibrillation or possibly RA fatigue, may play an important role in the prognosis of patients with PAH”, they write in Circulation: Cardiovascular Imaging.

RA longitudinal strain did not correlate with mean pulmonary arterial pressure or pulmonary vascular resistance. However, it was significantly associated with poorer RV function and with indirect measures of RV overload, such as RV end diastolic area and the ratio of RV to left ventricular area.

“These findings suggest that impaired RA function may manifest in PAH primarily when the RV becomes overloaded and begins to fail”, concludes the team.

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