Shift in sleep apnoea type in heart failure patients in the CANPAP trial

In patients with heart failure (HF), the predominant type of sleep apnoea can change over time in association with alterations in circulation time. The aim of this study was to determine whether, in some patients with HF, a spontaneous shift from mainly central (>50% central events) to mainly obstructive (>50% obstructive events) sleep apnoea (CSA and OSA, respectively) over time coincides with improvement in left ventricular ejection fraction (LVEF). Therefore, sleep studies and LVEFs of HF patients with CSA from the control arm of the Canadian Continuous Positive Airway Pressure for Patients with Central Sleep Apnea and Heart Failure (CANPAP) trial were examined to determine whether some converted to mainly OSA and, if so, whether this was associated with an increase in LVEF. Of 98 patients with follow-up sleep studies and LVEFs, 18 converted spontaneously to predominantly OSA. Compared with those in the nonconversion group, those in the conversion group had a significantly greater increase in the LVEF (2.8% versus -0.07%) and a significantly greater fall in the lung-to-ear circulation time (-7.6 s versus 0.6 s). In patients with HF, spontaneous conversion from predominantly CSA to OSA is associated with an improvement in left ventricular systolic function. Future studies will be necessary to further examine this relationship.