Reduced systemic vascular resistance is the underlying hemodynamic mechanism in nitrate‐stimulated vasovagal syncope during head‐up tilt‐table test

Abstract

Presyncopal symptoms during NTG-stimulated HUTT are SVR mediated, not cardiac output mediated. This study challenges the conventional idea of a decrease in cardiac output mediated by NTG as the overriding cause of presyncopal symptoms during HUTT.

Byung Gyu Kim et al.: Reduced systemic vascular resistance is the underlying hemodynamic mechanism in nitrate‐stimulated vasovagal syncope during head‐up tilt‐table test

“…SVR is calculated as 80 * (MAP-CVP)/CO, where MAP is mean arterial pressure and CVP is central venous pressure. The normal values of SVR range from 800 to 1200 dynes s/cm 5 [4] , consistent with the original article [1] . SVRI is calculated as 80*(MAP-CVP)/CI, where CI is cardiac index [5] ; and the formula equals 80*(MAP-CVP)/(CO/BSA), where BSA is body surface area.…”

“…The correct SVRI units should be presented as either dynes s/(cm 5 /m 2 ) or dynes s*m 2 /cm 5 . We estimated that the proper SVRI values in the study conducted by Kim et al [1] would range from 1900 to 2300 dynes s m 2 /cm 5 . We agree with the general results and conclusions of the article; however, the SVRI results should be recalculated.…”

“…We read with great interest the well-crafted article by Kim et al [1] , which reported that presyncopal symptoms during nitrate-stimulated tilt-testing could be explained by decreased systemic vascular resistance (SVR) rather than reduced cardiac output (CO). The study setup is sound, but being accustomed to this methodology [2] , [3] , we noticed inaccuracies in Tables 2 and 3.…”

“…This formula may also be presented as SVRI=SVR*BSA, and the normal values of SVRI range from 1900 to 2400 dynes s m 2 /cm 5 [2] , [3] , [5] . Notably, the reported SVRI values in the article by Kim et al [1] range from 612 to 683 and the units are given as dynes s/cm 5 /m 2 , indicating that the SVR values were divided and not multiplied by BSA. The correct SVRI units should be presented as either dynes s/(cm 5 /m 2 ) or dynes s*m 2 /cm 5 .…”

Stepwise Approach to the Different Parts of Vasovagal Syncope in a Patient Undergoing Cardioneuro Ablation

“…However, after successful vagal denervation, the vasodepressor response became obvious. Kim et al [10] recently assessed the determinants of VVS during glyceryl trinitrate-stimulated HUT and demonstrated that syncope might be related with systemic vascular resistance rather than cardiac output. In our case, HUT was demonstrated glyceryl trinitrate-stimulated vasodepressor response after CNA.…”