Isolated Systolic Hypertension of Youth – Findings From the I24abc Consortium

Objective: There is considerable controversy concerning the physiology and prognostic significance of isolated systolic hypertension (ISH) in youth. We sought to address this by pooling hemodynamic and echocardiographic data from participants up to 40 years in a large international academic research consortium. Design and method: In all 18 centers, 24-hour blood pressure (24hBP) was measured with the same validated oscillometric upper arm device (Mobil-O-Graph, I.E.M., Germany), using a transfer function and ARCSolver algorithms for determination of central pressures (using mean/diastolic BP calibration), pulsatile (Pressure Augmentation-AP, amplitudes of Forward (Pf) and Backward (Pb) wave) and steady state (Cardiac Output-CO, Total Peripheral Resistance-TPR) hemodynamics. Hypertension phenotypes were defined according to average 24h brachial BP as normotension (NTN), isolated systolic (ISH) and diastolic (IDH) hypertension, and systolic/diastolic hypertension (SDH). Left ventricular mass was determined by echocardiography, and indexed to body surface area (LVMi). Results: Overall, 675 participants were included. 52.3, 5.9, 19.1 and 22.7% were classified as NTN, ISH, IDH, and SDH, with average 24h brachial BPs of 117/71, 134/75, 124/85 and 140/93 mmHg, respectively. Participants with ISH were the youngest and tallest among all 4 groups, and had the highest proportion of men. Average 24h central SBP and PP were 121/49, 143/66, 125/38 and 140/46 mmHg in NTN, ISH, IDH, and SDH, respectively. Participants with ISH had highest average 24h values for pulsatile hemodynamics (AP, Pf, Pb) and cardiac output (CO), and participants with SDH had highest average 24h values for TPR, respectively (see Table). LVMi was 76.9, 84.8, 78.2 and 96.3 g/m2 in participants with NTN, ISH, IDH, and SDH, respectively (p<0.0001). Conclusions: In this cohort of younger individuals, ISH was an infrequent condition with specific clinical and hemodynamic characteristics. The relatively high LVMi and central BPs in those with ISH as compared to IDH and NTN is a suspicious prognostic sign.