Hypotension and syncopal attacks have been reported in association with drugs 
which block the renin-angiotensin-aldosterone system (RAAS). It has been 
proposed that the underlying mechanism is due to sensitisation of the 
Bezold-Jarisch reflex leading to withdrawal of sympathetic tone, profound and 
prolonged bradycardia, and hypotension. Sensitisation of this reflex occurs in 
the presence of blockade of the RAAS. In the ALTITUDE trial the use of the 
direct renin inhibitor, aliskiren, was associated with hypotensive episodes and 
an excess of ischaemic stroke. It is hypothesised that this is best explained by 
activation of the Bezold-Jarisch reflex, which may be particularly important in 
circumstances where there is dual blockade of the RAAS.