Tilt testing.

Tilt testing can help to diagnose unexplained syncope, by precipitating an episode during cardiac monitoring. The Italian protocol, now most widely used, involves giving sublingual nitroglycerine after 15 min, while monitoring beat-to-beat blood pressure (BP) and recording on video. Tilt testing is time-consuming but it is clinically useful and can guide therapy. Complications are rare. Syncope types include vasovagal syncope where BP falls after >3 min of tilt-up and later the heart rate falls; classic orthostatic hypotension where there is an immediate, progressive BP fall with minimal heart rate change; delayed orthostatic hypotension with a late BP fall after a stable phase but little or no heart rate rise; psychogenic pseudosyncope with apparent loss of consciousness, but no BP fall and a moderate heart rate rise; and postural orthostatic tachycardia syndrome where there is a significant heart rate rise but no BP fall.