Mildly elevated left ventricular outflow tract gradients are associated with increased short term mortality in inpatients without septal hypertrophy

Abstract Background The significance of left ventricular outflow tract gradients (LVOTG) on the clinical outcomes of hypertrophic cardiomyopathy (HCM) has been well studied. An LVOTG of ≥ 30 mmHg is considered significant. However, mildly elevated LVOTG at rest in individuals without basal septal hypertrophy is sometimes encountered in the echocardiography laboratory and data on its association with survival in this group is lacking. Purpose Here we explore the association between LVOTG and short term all cause mortality in inpatients without basal septal hypertrophy. Methods We retrospectively reviewed 47,866 consecutive inpatients who had an echocardiography study during their hospital stay between March 2010 and February 2021 . After excluding cases with incomplete data (10,882) and patients with basal septal hypertrophy > 12 mm (9,486), we remained with 27,498 patients. Demographic, baseline clinical and echocardiographic characteristics were derived from electronic records. Mortality data was validated against the ministry of health national records. A binary logistic regression model for predicting 30-day mortality according to LVOTG dichotomized at each point was used. Then we divided the cohort into 4 LVOTG groups (0-6, 6-10, 10-20 and > 20 mmHg) and the same regression model was used to compare between the groups. Results The mean age in our cohort was 66 ± 17 years and 54% were male. The mean LVOTG was 4.2 ± 2.4 mmHg (Median 4 (IQR=3-5) and the mean left ventricular ejection fraction was 55 ± 9%. A binary logistic regression model showed that when different LVOTG cut-points were used, even a mildly elevated LVOTG predicted short-term survival in this population (figure 1). We then divided our cohort into 4 groups based on LVOTG. There were 24,703 (90%) patients in group 1, 2549 (9%) in group 2, 201 (1%) in group 3 and 25 (0.1%) individuals in group 4. Patients in groups 1 and 2 were younger, had higher hemoglobin levels, lower C-reactive protein (CRP) levels, mildly lower septal thickness, and lower left ventricular ejection fraction compared to the groups with higher LVOTG (table 1). We then applied the same multivariate binary regression model to predict short term mortality with group 1 as a reference. The hazard ratio (HR) for group 2 was 1.3 (CI 95%: 1-1.6, p=0.03), for group 3 HR=2.8 (CI 95%: 1.6-5.1, p<0.001) and for group 4 HR=2.8 (CI 95%: 0.6-12.8, p=0.18). Conclusions We have shown in a large cohort of inpatients without basal septal hypertrophy that a mildly elevated rest LVOTG (6-10 and 10-20 mmHg) predicted all cause 30-day mortality. Patients in the elevated LVOTG groups were older with lower hemoglobin and higher CRP levels, but LVOTG remained an independent predictor in a multivariate regression model. This could potentially aid early detection of at-risk populations.Mortality at different LVOTG cut-pointsBaseline characteristics