A prediction model for ventricular tachycardia events using 24h ambulatory ECG

Background

Ventricular tachycardia (VT) is a potentially lethal condition that occurs intermittently. The aim of this study was to derive a risk prediction model for VT episodes detected on ≤30 day mobile cardiac telemetry using a 24 hour ambulatory ECG recording.

Methods

We included patients who were monitored for 2–30 full days in the USA using a full-disclosure mobile cardiac telemetry device in 2017. Patients with a VT episode ≥10 beats duration (VT≥10 beats) on the first full recording day were excluded. Arrhythmias were algorithmically detected and manually verified. A LASSO model was derived for the outcome of a VT≥10 beats detected on days 2–30. Potential predictors included age, sex, and ECG data from the first 24h: heart rate (max, min and mean), premature atrial and ventricular complexes occurring as singles, couplets, triplets, and runs ≥4 beats as well as the fastest rate for each event. The population was split into equal random training and testing samples.

Results

In a population of 19,789 patients (mean age 65.3, 43.4% men), and during a median recording time of 18 days there were 1,511 patients with at least one VT≥10 beats. The LASSO model had good discrimination in the testing sample, ROC-statistic 0.7586, 95% CI 0.7398–0.7774 (Figure 1a). A model excluding age and gender had similar discrimination (ROC 0.7528, 95% CI 0.7339–0.7717). In the testing sample the model was well calibrated (Figure 1b). In the top quintile more than one in five patients had a VT≥10 beats, enough to warrant extended monitoring.

Conclusion

A risk score based on variables easily derived from a standard 24h ECG can be used to predict high risk of VT episodes ≥10 beats within 30 days. In the top quintile VT events ≥10 beats were ten times more common than in the bottom quintile.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Hjärt-LungfondenSwedish Society for Medical Research

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)

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 < 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< 0.0001) and A (4.2 mm2 vs 6.4 mm2, p< 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 < 0.04), females had the opposite with higher normalized V and A with tablet compared to powder (p < 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