Alterations in cardiac autonomic control in severe idiopathic pulmonary arterial hypertension and its correlation to exercise capacity
Purpose: Idiopathic pulmonary arterial hypertension (IPAH) is a rapidly progressive disease leading to right heart failure and death. It is already known that in pts with PAH there is an alteration in cardiac autonomic nervous activity. Heart rate turbulence (HRT) is considered a prognostic marker of proarrhythmia and sudden cardiac death, unmasking abnormal transient alterations in cardiac autonomic control. Aim of the study was to examine HRT in patients with severe idiopathic PAH (IPAH) and its relation to exercise capacity.
Methods: The study population consisted of 46 pts, (32 ♀ and 14 ♂), mean age 50±9 years, Group A 20 pts: NYHA III, III–IV diagnosed as severe IPAH and Group B 26 pts: NYHA II, II–III diagnosed as moderately severe IPAH. All pts underwent cardiopulmonary exercise capacity (CPET) assessment and 24h Holter monitoring HRT analysis with calculation of 2 parameters, turbulence onset (TO) and turbulence slope (TS). Abnormal values: TO>0, TS<2.5msec/RR. Pts were defined as HRT (+) when TO or/and TS were abnormal and as HRT (−) when both TO and TS were normal or when HRT could not be calculated because of none or too few suitable PVCs.
Results: Abnormal HRT was found in 12 out of 20 pts (n=12, 60%) in group A and in none out of 26 (n=0, 0%) in group B (p=0,001). There was a tendency to greater TS mean values (±SD) in group B than in group A (6,55±7,5 vs 2,1±1,9 p=0.066). Significant positive correlation was found between TS and maximum oxygen uptake (VO2 max) (r=0,64, p=0,04). The correlation remained significant after adjustment for age and sex [β (SE)=0,0039 (0,001), p=0,028] and was independent of whether the patient was in A or B group [β (SE)=0, 0043 (0,001), p=0,033].
Conclusion: Our study population pts suffering of severe IPAH presented with cardiac autonomic system impairment, demonstrated mainly as abnormal TS in HRT. Interestingly a significant positive correlation was revealed between TS and physical capacity expressed as maximum oxygen consumption in CPET.