A third of patients with CSA before transplant acquired OSA after transplant. This alteration in apnea type cannot be explained by variations in body weight or dosage of prednisolone between the three patient groups after transplant, nor could we identify upper airway anatomic differences. No patient in the control group acquired OSA despite a similar medication profile. Therefore, we believe it possible that these patients may have had OSA prior to the development of CHF and CSA, which was uncovered by the eradication of CSA. This conclusion remains to be confirmed with rigorous prospective studies. read more
Thalhofer et al demonstrated persistence of CSA 3 to 9 weeks following transplantation in approximately 20% of patients with CHF and CSA. The severity of CSA was unchanged from the pretransplant value, prompting the conclusion that respiratory control centers were permanently damaged as a result of chronic CHF. In contrast, we have demonstrated that in those in whom CSA persists, there is substantial attenuation of severity over time. Furthermore, we have extended the observations of Thalhofer et al by demonstrating that correction of heart function translates to a reduction in both the CSA cycle length and the ventilation:apnea length ratio to levels similar to that observed in patients with idiopathic nonhypercapnic CSA, in whom heart function is normal and that persistence of CSA may occur despite normalization of sympathetic nerve activity. Our study confirms our previous observation that cycle length correlates inversely with heart function; therefore, we postulate that persistent abnormalities of chemosensitivity may underpin the persistence of CSA in these patients.
In summary we have demonstrated that CSA may persist for > 6 months following successful heart transplantation albeit with a significant attenuation in severity. This is despite the demonstration of normal heart function and reduction of sympathetic activity to the normal range. Further studies on chemoreflex and baroreflex activity, upper airway function and autonomic activity are required to further our understanding of SDB in this posttransplant group.