A significant reduction (20% vs 54%) in the efficacy of Valsalva at reverting paroxysmal SVT when standing compared with supine in a group of 35 patients with inducible and sustained SVT. | Mehta et al6 |
Sixty-five healthy subjects in sinus rhythm performing Valsalva in a series of positions studied established a significant increase in mean postmanoeuvre R-R interval (and therefore decrease in heart rate) when supine compared with sitting or semirecumbent. | Wong et al11 |
Studied the effects of respiration and posture on 11 patients with known paroxysmal SVT and demonstrated that increasing body dependency to a head-down position alone increased blood pressure sufficiently to revert 8 out of 11 patients (albeit in a highly controlled laboratory environment). | Waxman et al12 |
Compared baroreflex sensitivity with postural changes in 14 healthy subjects. A significant decrease in heart rate during the fourth phase of Valsalva, a significant increase in cardiac vagal activity and a decrease in sympathetic activation when comparing head-up to a head-down position were observed. | Kardos et al16 |
Examined the effects of head-down tilt on 17 patients with paroxysmal SVT and concluded that it conferred no additional benefit (Valsalva method used was asking the patients to ‘bear-down’ for 5 s). | Ornato et al10 |