ObjectiveA new derivative of 24 h ambulatory blood pressure monitoring (ABPM) is introduced and its association with left ventricular mass index (LVMI) in essential hypertension is examined.Patient populationOne hundred and fifty-three previously untreated essential hypertension patients.MethodsPatients underwent casual blood pressure (BP) readings, 24 h ABPM and left ventricular echocardiographic assessment. The following 24 h awake and sleep ABP variables were calculated: mean systolic and diastolic BP, systolic and diastolic BP loads (percentage of systolic readings > 140/120 mmHg (day/night) and diastolic readings > 90/80 mmHg (day/night)), standard deviation of systolic and diastolic ABP and nocturnal fall of systolic BP, as well as the integrated areas under the ABP curve. The area under the BP curve divided in horizontal slices was accurately modelled by a sigmoid curve. The parameters controlling the shape of the curve and in particular that regarding its ‘slope’ is hereafter called the ‘pressure-time index’.Results‘Systolic pressure-time index 24 h’ (SPTI24) is related to left ventricular mass index (multivariate analysis,P= 0.008). Using either partial correlation coefficients or a multivariate analysis, SPTI24is related to left ventricular mass index, independently of age, casual blood pressure, mean systolic and diastolic ABP, systolic and diastolic BP loads, BP variability (standard deviation (SD), nocturnal fall of systolic BP) and integrated area under the curve (multivariate analysis,P= 0.004).ConclusionsIn essential hypertension, the SPTI24is related to LVMI independently of age, casual blood pressure, integrated area under the curve or any other derivative of 24 h ABPM, and might be used to assess the extent of hypertensive load.