The importance of calibration method in determining the association between central blood pressure with left ventricular and left atrial strain

Association of Cumulative Systolic Blood Pressure With Left Atrial Function in the Setting of Normal Left Atrial Size: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Lower left atrial (LA) function is associated with increased risk for cardiovascular disease events; data on risk factors for impaired LA function are limited. We evaluated the effect of cumulative systolic blood pressure (cSBP) from midlife to older age on LA strain in adults with normal LA size.

METHODS

We included participants in the Atherosclerosis Risk in Communities study with LA strain measured on the visit 5 echocardiogram (2011-13), excluding those with atrial fibrillation and LA volume index >34 mL/m2. The cSBP was calculated from visit 1 (1987-89) through visit 5. Linear regression models were used to evaluate associations between cSBP and LA strain measures.

RESULTS

A total of 3,859 participants with a mean (SD) age of 75.2 (5.0) years were included in the analysis; 725 (18.8%) were Black and 2,342 (60.7%) were women. After adjusting for demographics, cardiovascular disease risk factors, heart failure, and coronary heart disease, each 10 mm Hg increase in cSBP was associated with 0.32% (95% CI, -0.52%, -0.13%) and 0.37% (95% CI, -0.51%, -0.22%) absolute reduction in LA reservoir and conduit strain, respectively. Associations were attenuated after adjustment for left ventricular (LV) systolic and diastolic function and mass (-0.12%: 95% CI, -0.31, 0.06 for reservoir strain; and -0.24%: 95% CI -0.38%, -0.10% for conduit strain). In subgroup analyses, the association of cSBP with conduit strain was statistically significant among those with normal LV systolic and diastolic function.

CONCLUSIONS

Cumulative exposure to elevated blood pressure from midlife to late life was modestly associated with lower LA reservoir and conduit strain in older adults with normal LA size, mostly related to the effect of blood pressure on LV function and mass. However, the association of cSBP and LA conduit strain in subgroups with normal LV function suggests that LA remodeling in response to hypertension occurs before LV dysfunction is detected on echocardiography.

Impact of a cuff-based device calibration method on the agreement between invasive and noninvasive aortic and brachial pressure

INTRODUCTION

Brachial cuff-based methods are increasingly used to estimate aortic systolic blood pressure (aoSBP). However, there are several unresolved issues.

AIMS

to determine to what extent the scheme used to calibrate brachial records (1) can affect noninvasive obtained aoSBP levels, and consequently, the level of agreement with the aoSBP recorded invasively, and (2) how different ways of calibrating ultimately impact the relationship between aoSBP and cardiac properties.

METHODS

brachial and aortic blood pressure (BP) was simultaneously obtained by invasive (catheterisation) and noninvasive (brachial oscillometric-device) methods (89 subjects). aoSBP was noninvasive obtained using three calibration schemes: 'SD': diastolic and systolic brachial BP, 'C': diastolic and calculated brachial mean BP (bMBP), 'Osc': diastolic and oscillometry-derived bMBP. Agreement between invasive and noninvasive aoSBP, and associations between BP and echocardiographic-derived parameters were analysed.

CONCLUSIONS

'C' and 'SD' schemes generated aoSBP levels lower than those recorded invasively (mean errors: 6.9 and 10.1 mmHg); the opposite was found when considering 'Osc'(mean error: -11.4 mmHg). As individuals had higher invasive aoSBP, the three calibration schemes increasingly underestimated aoSBP levels; and viceversa. The 'range' of invasive aoSBP in which the calibration schemes reach the lowest error level (-5-5 mmHg) is different: 'C': 103-131 mmHg; 'Osc': 159-201 mmHg; 'SD':101-124 mmHg. The calibration methods allowed reaching levels of association between aoSBP and cardiac characteristics, somewhat lower, but very similar to those obtained when considering invasive aoSBP. There is no evidence of a clear superiority of one calibration method over another when considering the association between aoSBP and cardiac characteristics.