Gender interaction effect on coronary lumen volume to mass ratio after administration of sublingual GTN powder compared to tablet in coronary computed tomography angiography (CCTA)
Authors: Kye J , Bagsic S , Kuo R , Cohoon T , Bhavnani S , Almeida S , Price M , Robinson A , Gonzalez J , Wesbey G 
Published: February 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Nitroglycerin (GTN) results in improved CCTA image quality and diagnostic accuracy due to vasodilation and improved contrast density. Although studies have shown that sublingual (SL) GTN spray has greater vasodilation and faster onset and duration of action compared to SL tablet, it is not commonly used due to cost. The comparative efficacy of SL GTN powder in CCTA is unknown.

Purpose
The purpose of this study is to determine whether SL GTN powder can increase the coronary lumen volume (V) and the coronary lumen volume to left myocardial mass ratio (V/M) compared to SL GTN tablet.

Methods
34 patients (17 females) with 0.8 mg SL GTN powder and 34 patients (17 females) with 0.8 mg SL GTN tablet administration were included in this retrospective case-control study. GTN was given 5 minutes pre-CCTA on a 256 slice single-heartbeat CT. Inclusion criteria: CAD-RADS 0 or 1, precontrast LM + LAD AJ-130 CAC &lt; 100, heart rate less than 75, phase of the cardiac cycle diastole, successful motion correction, Likert score 4 or 5, right- or co-dominance. The primary outcome assessed was left main plus left anterior descending (LM + LAD) V between GTN powder vs tablet. The secondary outcomes were LM + LAD V divided by 1) length of LM + LAD (derived mean area, A), and 2) M (V/M). The outcomes were measured by blinded PI with 17 yrs CCTA experience on GE workstation, 2020 version. Categorical variables were compared by Chi-Squared tests and continuous variables were compared between powder and tablet groups by unpaired t-tests if normally distributed, and Mann-Whitney U tests otherwise. Exploratory outcome analyses tested route of administration by sex interactions and main effects by Two-Way ANOVA’s. Further covariate-adjusted analyses were conducted using multiple linear regression models.

Results
Baseline characteristics were similar between powder and tablet administration. No statistically significant difference in median V, LM + LAD derived A , or median V/M was observed. A sex main effect demonstrated that females had significantly smaller V (630.6 mm3 vs 951.7 mm3, p&lt; 0.0001) and A (4.2 mm2 vs 6.4 mm2, p&lt; 0.0001) compared to males. These V and A sex differences were also observed when BMI or weight were included as covariates. When V and A were normalized by M, both revealed sex interactions depending on formulation. While males had higher normalized V and A in powder vs tablet (p &lt; 0.04), females had the opposite with higher normalized V and A with tablet compared to powder (p &lt; 0.04).

Conclusions
SL administration of the GTN powder 5 minutes before CCTA did not result in greater vasodilatory effect compared to the GTN tablet. However, gender interaction effects were observed, with greater V/M and A/M ratio in males with powder and greater V/M and A/M in women with tablet. These results suggest a potential differential gender effect based on the formulation of GTN. Prospective studies are warranted to evaluate these findings.
Abstract Figure. LM + LAD Lumen Volume to LV Mass by Sex