Heat-related morbidity in patients with orthostatic hypotension and primary autonomic failure

We investigated the effects of high-external-temperature exposure on neurogenic orthostatic hypotension (OH). Thirty-one patients with autonomic failure (AF) and pharmacologically treated OH related to probable multiple-system atrophy (n=7), Parkinson's disease (n=10), pure autonomic failure (n=7), and diffuse Lewy body disease (n=7) and 26 parkinsonians without AF were included. Prevalence and severity of clinical events were studied during the August 2003 heat wave and the 2004 summer. The prevalence of OH-related events was significantly higher in 2003 [45.1 vs. 11.5%; P=0.0052; OR=6.31 (1.35--33.53)] and 2004 [42.3 vs. 12.0%; P=0.014; OR=5.40 (1.28--22.68)] in AF than in controls. The mean severity score for clinical events was significantly higher in AF than in controls during 2003 heat wave (1.2+/-1.4 vs. 0.2+/-0.5) but similar in summer 2004 (0.7+/-1.0 vs. 0.1+/-0.3). Severe events (unusual home care, assistance, or hospitalization) were only observed in AF patients. A nonstatistically significant higher prevalence of clinical events was observed in AF patients prescribed fludrocortisone (66.7%) by comparison to heptaminol (42.9%), midodrine (45.5%), or midodrine plus fludrocortisone (28.6%). This study shows that AF patients have a poor clinical outcome when exposed to high temperatures and that heat exposure is a risk factor for OH worsening.