Evaluation of ventricular-arterial coupling by impedance cardiography in healthy volunteers

BACKGROUND

The interplay between cardiac function and the arterial system is currently defined as ventricular-arterial coupling (VAC) and it is an expression of global cardiovascular efficiency. VAC involves a variety of complex interactions between the heart and the vasculature. A basic index of VAC is the ratio of effective arterial elastance (Ea)/ end-systolic elastance (Ees). While this is often done with echocardiography, obtaining Ea/Ees using impedance cardiography is feasible, although this possibility has not been explored so far.

OBJECTIVE

The aim of this study was to compare the Ea/Ees values obtained using echocardiography and impedance cardiography.

APPROACH

Two independent operators estimated Ea/Ees in 91 (41  ±  14 years old, women 51%) untreated apparently healthy individuals using (1) Doppler echocardiography with the single-beat method developed by Chen et al (2001 J. Am. Coll. Cardiol. 38 2028-34); and (2) data provided by impedance cardiography. The differences between Ea/Ees values were compared and correlation between both methods was estimated.

MAIN RESULTS

Although Ea and Ees values calculated by impedance cardiography were lower than those estimated by echocardiography (-0.201  ±  0.457 mmHg ml^-1 and  -0.193  ±  0.413 mmHg ml^-1), Ea/Ees ratio values were similar. Thus, there was no significant difference between the mean values of Ea/Ees estimated by impedance cardiography or echocardiography (Ea/Ees impedance cardiography  -  Ea/Ees echocardiography  =  -0.015  ±  0.096, p   =  0.150). Ea/Ees values calculated by both methods were highly correlated (r  =  0.85, p   <  0.001), as well as the pre-ejection and left ventricular ejection time (r  =  0.83 and r  =  0.91, respectively).

SIGNIFICANCE

In healthy individuals, estimation of Ea/Ees by impedance cardiography yielded similar values to those obtained using echocardiography.

Blood pressure response to treatment of obese vs non-obese adults with sleep apnea

Many patients with obstructive sleep apnea (OSA), but not all, have a reduction in blood pressure (BP) with positive airway pressure (PAP) treatment. Our objective was to determine whether the BP response following PAP treatment is related to obesity. A total of 188 adults with OSA underwent 24-hour BP monitoring and 24-hour urinary norepinephrine collection at baseline. Obesity was assessed by waist circumference, body mass index, and abdominal visceral fat volume. Participants adherent to PAP treatment were reassessed after 4 months. Primary outcomes were 24-hour mean arterial pressure (MAP) and 24-hour urinary norepinephrine level. Obstructive sleep apnea participants had a significant reduction in 24-hour MAP following PAP treatment (-1.22 [95% CI: -2.38, -0.06] mm Hg; P = .039). No significant correlations were present with any of the 3 obesity measures for BP or urinary norepinephrine measures at baseline in all OSA participants or for changes in BP measures in participants adherent to PAP treatment. Changes in BP measures following treatment were not correlated with baseline or change in urinary norepinephrine. Similar results were obtained when BP or urinary norepinephrine measures were compared between participants dichotomized using the sex-specific median of each obesity measure. Greater reductions in urinary norepinephrine were correlated with higher waist circumference (rho = -0.21, P = .037), with a greater decrease from baseline in obese compared to non-obese participants (-6.26 [-8.82, -3.69] vs -2.14 [-4.63, 0.35] ng/mg creatinine; P = .027). The results indicate that the BP response to PAP treatment in adults with OSA is not related to obesity or urinary norepinephrine levels.

Left Atrial Phasic Function by Cardiac Magnetic Resonance Feature Tracking Is a Strong Predictor of Incident Cardiovascular Events

BACKGROUND

The prognostic importance of left atrial (LA) dysfunction is increasingly recognized. Magnetic resonance imaging can provide excellent visualization of the LA wall. We aimed to study the association of LA dysfunction measured using feature-tracking magnetic resonance imaging with incident adverse cardiovascular events among subjects with or without heart failure (HF) at baseline.

METHODS AND RESULTS

We prospectively studied 640 adults without HF (n=419), HF with preserved ejection fraction (n=101), or HF with reduced ejection fraction (n=120). We measured phasic LA function by volumetric and feature-tracking methods to derive longitudinal strain. The composite outcome of incident HF hospitalization or death was adjudicated during a median follow-up of 37.1 months. Measures of LA phasic function were more prominently impaired in subjects with HF with reduced ejection fraction than among subjects with HF with preserved ejection fraction. In unadjusted Cox proportional hazards models, all measures of phasic LA function and volumes (maximum, minimum, and diastatic) were associated with the composite outcome. However, in analyses that adjusted for clinical risk factors, HF status, maximum LA volume, left ventricular mass, and left ventricular ejection fraction, measures of conduit and reservoir LA function, but not booster-pump function, were associated with the composite outcome. The strongest associations were observed for conduit longitudinal strain (standardized hazard ratio, 0.66; 95% CI, 0.49-0.88; P=0.004), conduit strain rate (standardized hazard ratio, 1.59; 95% CI, 1.16-2.16; P=0.0035), and reservoir strain (standardized hazard ratio, 0.68; 95% CI, 0.52-0.89; P=0.0055).

CONCLUSIONS

Phasic LA function measured using magnetic resonance imaging feature tracking is independently predictive of the risk of incident HF admission or death, even after adjusting for LA volume and left ventricular remodeling.

Phenotype and Risk Burden of Sleep Apnea: A Population-Based Cohort Study

Sleep apnea (SA) prevalence had increased. The socioeconomic burden is significant because of healthcare-related costs and adverse outcome, especially in moderate-to-severe SA. However, the population impact is unclear, particularly for mild SA. We aimed to assess the current prevalence and the cardiovascular risk associates of SA in the general population. We performed home polygraphy and extensive clinical, sociodemographic, and cardiovascular assessment in 2205 eligible subjects from a population-based cohort. Successful polygraphy was obtained in 1809 subjects (mean age, 56.0; SD, 5.9 years; 52.3% women). The prevalence was 41.0%, 11.8%, and 6.5% for mild, moderate, and severe SA in men and 26.6%, 4.4%, and 1.2% in women. Male sex, age, increasing BMI, and snoring were independently associated with SA, whereas sleepiness or tiredness were not. Compared with those without SA, mild SA was associated with (age- and sex-adjusted OR; 95% CI): diabetes mellitus (2.40; 1.52-3.80), hypertension (1.76; 1.42-2.19), left ventricular hypertrophy (1.36; 1.03-1.79), arterial plaques (1.19; 0.94-1.52), and increased IL-6 (interleukin-6) levels (1.37; 1.10-1.72). These associations were more pronounced in moderate-to-severe SA. To conclude, SA is highly prevalent in the middle-aged general population. It is largely undetected and undetectable using a symptom-based strategy. Yet, even the large group with mild SA shows a manifestly higher metabolic, inflammatory, and cardiovascular risk factor burden, with potential public health implications.

Right ventricular outflow tract velocity time integral-to-pulmonary artery systolic pressure ratio: a non-invasive metric of pulmonary arterial compliance differs across the spectrum of pulmonary hypertension

Pulmonary arterial compliance (PAC), invasively assessed by the ratio of stroke volume to pulmonary arterial (PA) pulse pressure, is a sensitive marker of right ventricular (RV)-PA coupling that differs across the spectrum of pulmonary hypertension (PH) and is predictive of outcomes. We assessed whether the echocardiographically derived ratio of RV outflow tract velocity time integral to PA systolic pressure (RVOT-VTI/PASP) (a) correlates with invasive PAC, (b) discriminates heart failure with preserved ejection-associated PH (HFpEF-PH) from pulmonary arterial hypertension (PAH), and (c) is associated with functional capacity. We performed a retrospective cohort study of patients with PAH (n = 70) and HFpEF-PH (n = 86), which was further dichotomized by diastolic pressure gradient (DPG) into isolated post-capillary PH (DPG < 7 mmHg; Ipc-PH, n = 54), and combined post- and pre-capillary PH (DPG ≥ 7 mm Hg; Cpc-PH, n = 32). Of the 156 patients, 146 had measurable RVOT-VTI or PASP and were included in further analysis. RVOT-VTI/PASP correlated with invasive PAC overall (ρ = 0.61, P < 0.001) and for the PAH (ρ = 0.38, P = 0.002) and HFpEF-PH (ρ = 0.63, P < 0.001) groups individually. RVOT-VTI/PASP differed significantly across the PH spectrum (PAH: 0.13 [0.010–0.25] vs. Cpc-PH: 0.20 [0.12–0.25] vs. Ipc-PH: 0.35 [0.22–0.44]; P < 0.001), distinguished HFpEF-PH from PAH (AUC = 0.72, 95% CI = 0.63–0.81) and Cpc-PH from Ipc-PH (AUC = 0.78, 95% CI = 0.68–0.88), and remained independently predictive of 6-min walk distance after multivariate analysis (standardized β-coefficient = 27.7, 95% CI = 9.2–46.3; P = 0.004). Echocardiographic RVOT-VTI/PASP is a novel non-invasive metric of PAC that differs across the spectrum of PH. It distinguishes the degree of pre-capillary disease within HFpEF-PH and is predictive of functional capacity.

Abstract 106: Predicting Pulmonary Hypertension Readmission Using Machine Learning Models

Objectives: Pulmonary hypertension (PH) is increasingly recognized but understudied. We sought to determine predictors of 30-day readmission after PH-related hospitalization using Driverless Artificial Intelligence (DAI) algorithm.

Methods: We utilized the 2012-2014 Healthcare Cost and Utilization Project Nationwide Readmission Database (NRD) that accounts for weighted estimates of roughly 35 million discharges in the United States. Adult patients with primary ICD-9-CM diagnosis codes of 416.0 and 416.8 for primary and secondary PH with an index admission and any readmission within 30-days of the index event were identified. We assessed predictors of all cause 30-day readmission from clinical, hospital and 29 AHRQ comorbidity measures using predictive modeling to provide interpretable risk factors globally at population level and locally associated with each discharge. The risk prediction model was developed using DAI algorithm and results compared to models based on LIME GLM, Random Forest, and Decision Tree. Overall model performance was assessed using concordance statistic.

Results: Data from patients with 14,659 admissions and 2797 30-day readmissions were used to train the model. After data processing, the final model included 3674 variables. The Random Forest model had the best performance with c-statistic of 0.70 and surrogate models compared at AUCs of 0.51(Decision Tree), 0.62 (LIME) and (DAI) 0.59. Global features that mainly important to the overall prediction of DAI model were deficiency anemia, APR-DRG severity risk, APR-DRG mortality risk, renal failure and CHF.

Conclusion: Using predictive models with high predictive power, interpretable risk factors and prediction accuracy may enable health care systems to accurately target high-risk PH patients and prevent recurrent readmissions.

The role of ventricular-arterial coupling in cardiac disease and heart failure: assessment, clinical implications and therapeutic interventions. A consensus document of the European Society of Cardiology Working Group on Aorta & Peripheral Vascular Diseases, European Association of Cardiovascular Imaging, and Heart Failure Association

Ventricular-arterial coupling (VAC) plays a major role in the physiology of cardiac and aortic mechanics, as well as in the pathophysiology of cardiac disease. VAC assessment possesses independent diagnostic and prognostic value and may be used to refine riskstratification and monitor therapeutic interventions. Traditionally, VAC is assessed by the non-invasive measurement of the ratio of arterial (Ea) to ventricular end-systolic elastance (Ees). With disease progression, both Ea and Ees may become abnormal and the Ea/Ees ratio may approximate its normal values. Therefore, the measurement of each component of this ratio or of novel more sensitive markers of myocardial (e.g. global longitudinal strain) and arterial function (e.g. pulse wave velocity) may better characterize VAC. In valvular heart disease, systemic arterial compliance and valvulo-arterial impedance have an established diagnostic and prognostic value and may monitor the effects of valve replacement on vascular and cardiac function. Treatment guided to improve VAC through improvement of both or each one of its components may delay incidence of heart failure and possibly improve prognosis in heart failure. In this consensus document, we describe the pathophysiology, the methods of assessment as well as the clinical implications of VAC in cardiac diseases and heart failure. Finally, we focus on interventions that may improve VAC and thus modify prognosis.

Effect of Obesity on Left Atrial Strain in Persons Aged 35-55 Years (The Asklepios Study)

Obesity increases the risk of heart failure and atrial fibrillation. Left atrial (LA) dysfunction is increasingly recognized as a mediator of cardiovascular disease. Early effects of obesity on LA function have not been examined in large population samples. We quantified LA strain and strain rate (SR) through speckle tracking echocardiography in 1,531 middle-aged community-based participants enrolled in the Asklepios study. We compared LA function between individuals with body mass index (BMI) < 25 kg/m² (n = 779), 25 to 29.9 kg/m² (n = 618) and ≥ 30 kg/m² (n = 134). Significant differences in reservoir longitudinal LA strain (BMI < 25 kg/m² = 35.3%, BMI 25-29.9 kg/m² = 33.1%, and BMI ≥ 30 kg/m² = 30.9%; p < 0.00001) strain rate ([SR] BMI < 25 kg/m² = 151; BMI 25 to 29.9 kg/m² = 141; and BMI ≥ 30 kg/m² = 135 %/s; p <0.00001) and expansion index (BMI < 25 kg/m² = 1.6, BMI 25 to 29.9 kg/m² = 1.4, and BMI ≥ 30 kg/m² = 1.4; p <0.00001) were seen, indicating reduced reservoir function with increasing BMI. Obesity was also associated with impaired LA conduit function, including conduit longitudinal LA strain (BMI < 25 kg/m² = 21.6%, BMI 25 to 29.9 kg/m² = 18.9%, and BMI ≥ 30 kg/m² = 16.7%; p <0.00001), SR (BMI < 25 kg/m² = -189, BMI 25 to 29.9 kg/m² = 166, and BMI ≥ 30 kg/m² = 150 %/s; p <0.0001) and passive LA emptying fraction (BMI < 25 kg/m² = 40.5, BMI 25 to 29.9 kg/m² = 36.5, and BMI ≥ 30 kg/m² = 36%, p <0.00001). These differences persisted after adjustment for age, gender and other potential confounders. In contrast to reservoir and conduit function, obesity was associated with increased booster pump function (active LA emptying fraction: BMI < 25 kg/m² = 19.4%, BMI 25 to 29.9 kg/m² = 20.5%, and BMI ≥ 30 kg/m² = 21.5%; p <0.00001). In middle-aged adults, obesity is associated with impaired reservoir and conduit LA function and higher booster function, which may be compensatory. Loss of booster LA function, either because of more advanced LA dysfunction or atrial fibrillation, may play an important role in precipitating heart failure in obese individuals.

Impact of Diabetes Mellitus on Ventricular Structure, Arterial Stiffness, and Pulsatile Hemodynamics in Heart Failure With Preserved Ejection Fraction

Background Heterogeneity in the underlying processes that contribute to heart failure with preserved ejection fraction ( HF p EF ) is increasingly recognized. Diabetes mellitus is a frequent comorbidity in HF p EF , but its impact on left ventricular and arterial structure and function in HF p EF is unknown. Methods and Results We assessed the impact of diabetes mellitus on left ventricular cellular and interstitial hypertrophy (assessed with cardiac magnetic resonance imaging, including T1 mapping pregadolinium and postgadolinium administration), arterial stiffness (assessed with arterial tonometry), and pulsatile arterial hemodynamics (assessed with in-office pressure-flow analyses and 24-hour ambulatory monitoring) among 53 subjects with HF p EF (32 diabetic and 21 nondiabetic subjects). Despite few differences in clinical characteristics, diabetic subjects with HFpEF exhibited a markedly greater left ventricular mass index (78.1 [95% CI , 70.4-85.9] g versus 63.6 [95% CI , 55.8-71.3] g; P=0.0093) and indexed extracellular volume (23.6 [95% CI , 21.2-26.1] mL/m2 versus 16.2 [95% CI , 13.1-19.4] mL/m2; P=0.0008). Pronounced aortic stiffening was also observed in the diabetic group (carotid-femoral pulse wave velocity, 11.86 [95% CI , 10.4-13.1] m/s versus 8.8 [95% CI , 7.5-10.1] m/s; P=0.0027), with an adverse pulsatile hemodynamic profile characterized by increased oscillatory power (315 [95% CI , 258-373] mW versus 190 [95% CI , 144-236] mW; P=0.0007), aortic characteristic impedance (0.154 [95% CI , 0.124-0.183] mm Hg/mL per second versus 0.096 [95% CI , 0.072-0.121] mm Hg/mL per second; P=0.0024), and forward (59.5 [95% CI , 52.8-66.1] mm Hg versus 40.1 [95% CI , 31.6-48.6] mm Hg; P=0.0010) and backward (19.6 [95% CI , 16.2-22.9] mm Hg versus 14.1 [95% CI , 10.9-17.3] mm Hg; P=0.0169) wave amplitude. Abnormal pulsatile hemodynamics were also evident in 24-hour ambulatory monitoring, despite the absence of significant differences in 24-hour systolic blood pressure between the groups. Conclusions Diabetes mellitus is a key determinant of left ventricular remodeling, arterial stiffness, adverse pulsatile hemodynamics, and ventricular-arterial interactions in HF p EF . Clinical Trial Registration URL : https://www.clinicaltrials.gov . Unique identifier: NCT 01516346.

Vitamin K Status, Warfarin Use, and Arterial Stiffness in Heart Failure

Large artery stiffening contributes to the pathophysiology of heart failure (HF) and associated comorbidities. MGP (matrix Gla-protein) is a potent inhibitor of vascular calcification. MGP activation is vitamin K-dependent. We aimed (1) to compare dp-ucMGP (dephospho-uncarboxylated MGP) levels between subjects with HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF) and subjects without HF; (2) to assess the relationship between dp-ucMGP levels and arterial stiffness; and (3) to assess the relationship between warfarin use, dp-ucMGP levels, and arterial stiffness in HF. We enrolled 348 subjects with HFpEF (n=96), HFrEF (n=53), or no HF (n=199). Carotid-femoral pulse wave velocity, a measure of large artery stiffness, was measured with arterial tonometry. Dp-ucMGP was measured with ELISA. Dp-ucMGP levels were greater in both HFrEF (582 pmol/L; 95% CI, 444-721 pmol/L) and HFpEF (549 pmol/L; 95% CI, 455-643 pmol/L) compared with controls (426 pmol/L; 95% CI, 377-475 pmol/L; ANCOVA P=0.0067). Levels of dp-ucMGP were positively associated with carotid-femoral pulse wave velocity (standardized β, 0.31; 95% CI, 0.19-0.42; P<0.0001), which was also true in analyses restricted to patients with HF (standardized β, 0.34; 95% CI, 0.16-0.52; P=0.0002). Warfarin use was significantly associated with carotid-femoral pulse wave velocity (standardized β, 0.13; 95% CI, 0.004-0.26; P=0.043), but this relationship was eliminated after adjustment for dp-ucMGP. In conclusion, levels of dp-ucMGP are increased in HFpEF and HFrEF and are independently associated with arterial stiffness. Future studies should investigate whether vitamin K supplementation represents a suitable therapeutic strategy to prevent or reduce arterial stiffness in HFpEF and HFrEF.

Arterial Properties as Determinants of Left Ventricular Mass and Fibrosis in Severe Aortic Stenosis: Findings From ACRIN PA 4008

Background The role of arterial load in severe aortic stenosis is increasingly recognized. However, patterns of pulsatile load and their implications in this population are unknown. We aimed to assess the relationship between the arterial properties and both (1) left ventricular remodeling and fibrosis and (2) the clinical course of patients with severe aortic stenosis undergoing aortic valve replacement ( AVR ). Methods and Results We enrolled 38 participants with symptomatic severe aortic stenosis scheduled to undergo surgical AVR . Aortic root characteristic impedance, wave reflections parameters (reflection magnitude, reflected wave transit time), and myocardial extracellular mass were measured with cardiac magnetic resonance imaging and arterial tonometry Cardiac magnetic resonance imaging was repeated at 6 months in 30 participants. A reduction in cellular mass (133.6 versus 113.9 g; P=0.002) but not extracellular mass (42.3 versus 40.6 g; P=0.67) was seen after AVR . Participants with higher extracellular mass exhibited greater reflection magnitude (0.68 versus 0.54; P=0.006) and lower aortic root characteristic impedance (56.3 versus 96.9 dynes/s per cm5; P=0.006). Reflection magnitude was a significant predictor of smaller improvement in the quality of life (Kansas City Cardiomyopathy Questionnaire score) after AVR ( R=-0.51; P=0.0026). The 6-minute walk distance at 6 months after AVR was positively correlated with the reflected wave transit time ( R=0.52; P=0.01). Conclusions Consistent with animal studies, arterial wave reflections are associated with interstitial volume expansion in severe aortic stenosis and predict a smaller improvement in quality of life following AVR . Future trials should assess whether wave reflections represent a potential therapeutic target to mitigate myocardial interstitial remodeling and to improve the clinical status of this patient population.

Physical Activity Following Positive Airway Pressure Treatment in Adults With and Without Obesity and With Moderate-Severe Obstructive Sleep Apnea

STUDY OBJECTIVES

To examine the level of physical activity (PA) before and following positive airway pressure (PAP) treatment in adults who have obstructive sleep apnea (OSA) with obesity versus without obesity.

METHODS

Simultaneous waist accelerometer and wrist actigraphy recordings were obtained in 129 adults with obesity and 69 adults without obesity and who had OSA prior to and following 4 months of PAP therapy and in 52 patients in a control group. Primary PA measurements were average steps per day on waist accelerometry and average counts per minute (CPM) per day on wrist actigraphy.

RESULTS

At baseline, participants with obesity and OSA exhibited fewer steps per day on waist accelerometer and fewer CPM per day on wrist actigraphy compared to participants without obesity and with OSA (despite similar apnea-hypopnea index between groups). Following PAP treatment, participants with OSA had modestly increased CPM per day on wrist actigraphy (17.69 [95% confidence interval (CI), 5.67-29.71], P = .005) and increased light PA time (0.26 [95% CI, 0.07-0.44] hours, P = .008) on waist accelerometer. Participants without obesity and with OSA had greater improvements in PA measures on average compared to participants with obesity and OSA, although the differences were not statistically significant. Weight increased following PAP treatment in the participants with obesity and OSA (1.71 [95% CI, 0.41-3.02] kg, P = .010) but was unchanged in the group without obesity (0.93 [95% CI, -0.89 to 2.76] kg, P = .311).

CONCLUSIONS

Compared to study participants without obesity and with OSA, participants with obesity and OSA had reduced PA at baseline. PA increased significantly in participants without obesity, with OSA, and who were adherent to PAP treatment. Results indicate that treatment of OSA is unlikely to be associated with a change in PA in adults with obesity and OSA and help explain the absence of weight loss following PAP treatment in adults with OSA.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov, title: The Effects of Treating Obese and Lean Patients With Sleep Apnea (PISA), identifier: NCT01578031, URL: https://clinicaltrials.gov/ct2/show/NCT01578031.

Hemodynamic Patterns Identified by Impedance Cardiography Predict Mortality in the General Population: The PREVENCION Study

Background Blood pressure is determined by the interactions between the heart and arterial properties, and subjects with identical blood pressure may have substantially different hemodynamic determinants. Whether arterial hemodynamic indices quantified by impedance cardiography ( ICG ), a simple operator-independent office procedure, independently predict all-cause mortality in adults from the general population, and specifically among those who do not meet criteria for American College of Cardiology/American Heart Association stage 2 hypertension, is currently unknown. Methods and Results We studied 1639 adults aged 18 to 80 years from the general population. We used ICG to measure hemodynamic parameters and metrics of cardiac function. We assessed the relationship between hemodynamic parameters measured at baseline and all-cause mortality over a mean follow-up of 10.9 years. Several ICG parameters predicted death. The strongest predictors were total arterial compliance index (standardized hazard ratio=0.38; 95% confidence interval=0.31-0.46; P<0.0001) and indices of cardiac contractility: velocity index (standardized hazard ratio=0.45; 95% confidence interval=0.37-0.55; P<0.0001) and acceleration index (standardized hazard ratio=0.44; 95% confidence interval=0.35-0.55; P<0.0001). These remained independently predictive of death after adjustment for multiple confounders, as well as systolic and diastolic blood pressure. Among subjects without stage 2 hypertension (n=1563), indices of cardiac contractility were independently predictive of death and identified a subpopulation (25% of non-stage-2 hypertensives) that demonstrated a high 10-year mortality risk, equivalent to that of stage 2 hypertensives. Conclusions Hemodynamic patterns identified by ICG independently predict mortality in the general population. The predictive value of ICG applies even in the absence of American College of Cardiology/American Heart Association stage 2 hypertension and identifies higher-risk individuals who are in earlier stages of the hypertension continuum.

Aldosterone, inactive matrix gla-protein, and large artery stiffness in hypertension

Vascular calcification leads to increased large artery stiffness. Matrix gla-protein (MGP) is a vitamin K-dependent protein that inhibits arterial calcification. Aldosterone promotes vascular calcification and stiffness, but the relationships between aldosterone, MGP, and arterial stiffness are unknown. We studied 199 adults (predominantly older men) with hypertension. We assessed the relationship between levels of dephospho-uncarboxylated MGP (dp-ucMGP), aldosterone, and carotid-femoral pulse wave velocity (CF-PWV) using standard regression and mediation analyses. Plasma aldosterone was measured in a subgroup of subjects (n = 106). Aldosterone was strongly associated with dp-ucMGP (standardized β = 0.50, P < .001), which was independent of potential confounders (β = 0.37, P < .001). Levels of dp-ucMGP were significantly associated with CF-PWV (β = 0.30; P < .001), which persisted after adjustment for potential confounders (β = 0.25; P = .004). Plasma aldosterone was also significantly associated with CF-PWV (standardized β = 0.21; P = .035). However, in a model that included aldosterone and dp-ucMGP, only the latter was associated with CF-PWV. Mediation analyses demonstrated a significant dp-ucMGP-mediated effect of aldosterone on CF-PWV, without a significant direct (dp-ucMGP independent) effect. Our study demonstrates a novel independent association between high aldosterone levels and dp-ucMGP, suggesting that aldosterone may influence the MGP pathway. This relationship appears to underlie the previously documented relationship between aldosterone and increased arterial stiffness.

Poor Glycemic Control Is Associated With Increased Extracellular Volume Fraction in Diabetes

OBJECTIVE

We assessed whether poor glycemic control is associated with an increase in myocardial fibrosis among adults with diabetes.

RESEARCH DESIGN AND METHODS

We studied 47 adults with type 2 diabetes and stratified them into three groups according to their hemoglobin A1c (HbA1c) level: <6.5% (group 1; n = 12), 6.5-7.5% (group 2; n = 20), and >7.5% (group 3; n = 15). Left ventricular (LV) mass was assessed using cardiac MRI. The extracellular volume fraction (ECVF), an index of myocardial fibrosis, was measured by using myocardial T1 mapping before and after the administration of a gadolinium-based contrast agent.

RESULTS

Mean HbA1c was 5.84 ± 0.16%, 6.89 ± 0.14%, and 8.57 ± 0.2% in groups 1, 2, and 3, respectively. LV mass was not significantly different between the groups. The myocardial ECVF was significantly greater in groups 2 (mean 27.6% [95% CI 24.8-30.3]) and 3 (27.6% [24.4-30.8]) than in group 1 (21.1% [17.5-24.7]; P = 0.015). After adjusting for age, sex, BMI, blood pressure, and estimated glomerular filtration rate, the myocardial ECVF was significantly greater in groups 2 (27.4% [24.4-30.4]) and 3 (28% [24.5-31.5]) than in group 1 (20.9% [17.1-24.6]; P = 0.0156, ANCOVA).

CONCLUSIONS

An increased myocardial ECVF, suggesting myocardial fibrosis, is independently associated with poor glycemic control among adults with diabetes. Further research should assess whether tight glycemic control can revert fibrosis to healthy myocardium or ameliorate it and its adverse clinical consequences.

Circulating Dephospho-Uncarboxylated Matrix Gla-Protein Is Associated With Kidney Dysfunction and Arterial Stiffness

BACKGROUND

Large artery stiffening is increased in advanced chronic kidney disease (CKD) but likely develops progressively in earlier stages of CKD. Active matrix Gla-protein (MGP) is a potent vitamin K-dependent inhibitor of vascular calcification. A recent animal model demonstrated intrinsic abnormalities in vitamin K metabolism even in early CKD, but whether early human CKD is associated with vascular vitamin K deficiency is unknown.

METHODS

We enrolled 137 adults without HF with varying degrees of renal function: normal estimated glomerular filtration rate (eGFR; >90 ml/min; n = 59), mildly reduced eGFR (stage 2 CKD: eGFR = 60-89 ml/min; n = 53) or at least moderately reduced eGFR (stage 3-5 CKD; eGFR < 60 ml/min; n = 25). Carotid-femoral pulse wave velocity (CF-PWV) was measured with carotid and femoral tonometry. Dephospho-uncarboxylated matrix gla-protein (dp-ucMGP) was measured with enzyme-linked immunosorbent assay (ELISA) (VitaK; Maastricht University; The Netherlands).

RESULT

Dp-ucMGP levels were progressively increased with decreasing renal function (eGFR ≥ 90: 247 pmol/l; eGFR 60-89: 488 pmol/l; eGFR < 60: 953 pmol/l; P < 0.0001). These differences persisted after adjustment for multiple potential confounders (eGFR ≥ 90: 314 pmol/l; eGFR 60-89: 414 pmol/l; eGFR < 60: 770 pmol/l; P < 0.0001). In a multivariable model adjusted for various confounders, dp-ucMGP was a significant independent predictor of CF-PWV (β = 0.21; P = 0.019). In formal mediation analyses, dp-ucMGP mediated a significant relationship between eGFR and higher CF-PWV (β = -0.16; P = 0.005), whereas no significant dp-ucMGP-independent relationship was present (β = -0.02; P = 0.80).

CONCLUSIONS

CKD is associated with increased (inactive) dp-ucMGP, a vitamin K-dependent inhibitor of vascular calcification, which correlates with large artery stiffness. Further studies are needed to assess whether vitamin K2 supplementation represents a suitable therapeutic strategy to prevent or reduce arterial stiffening in CKD.

"Sleep disordered breathing and ECG R-wave to radial artery pulse delay, The Multi-Ethnic Study of Atherosclerosis"

BACKGROUND

Electrocardiography R-wave to radial artery pulse delay (RRD) represents pulse transit time inclusive of pre-ejection period (PEP) and arterial pulse propagation time. RRD is proposed to largely reflect arterial stiffness when PEP is accounted for (shorter RRD = higher arterial stiffness). Sleep disordered breathing (SDB) causes intermittent hypoxemia and sympathetic activation, which negatively influences vascular function. We aimed to examine the association of measures of SDB with RRD.

METHODS

Our sample consisted of participants in the Multi-Ethnic Study of Atherosclerosis without prevalent cardiovascular disease who underwent a daytime arterial elasticity exam, cardiac magnetic resonance imaging (MRI), and overnight polysomnography. SDB measures of interest included apnea hypopnea index (AHI) and oxygen desaturation index (ODI) (N = 1173). RRD was regressed on each measure of SDB separately, with adjustment for other cardiovascular risk factors as well as for correlates of the PEP, another component of RRD, by including cardiac MRI measures of contractility and preload.

RESULTS

In multivariate analysis, among measures of SDB, ODI, a marker of intermittent hypoxemia, was inversely associated with RRD (β = -60.2 msec per SD [15.5/hr], p = 0.04). No significant association was found with AHI. In gender stratified analyses, ODI and AHI were predictive of RRD in men only (β = -111.3 msec per SD [15.5/hr], p = 0.01 and β = -100.3 msec per SD [16.1/hr], p = 0.02 respectively).

CONCLUSION

Severity of SDB as measured by ODI was associated with RRD, a marker of arterial stiffness. Thus, association of RRD with measures of SDB appears to be gender-dependent.

Association of arginine vasopressin with low atrial natriuretic peptide levels, left ventricular remodelling, and outcomes in adults with and without heart failure

Aims

The arginine vasopressin (AVP) pathway has been extensively studied in heart failure (HF) with reduced ejection fraction (HFrEF), but less is known about AVP in HF with preserved EF (HFpEF). Furthermore, the association between AVP and atrial natriuretic peptide (ANP, a well‐known inhibitor of AVP secretion) in HF is unknown.

Methods and results

We studied subjects with HFpEF (n = 28) and HFrEF (n = 25) and without HF (n = 71). Left ventricular (LV) mass and left atrial (LA) volumes were measured with cardiac magnetic resonance imaging. Arginine vasopressin and ANP were measured with enzyme‐linked immunosorbent assay. Arginine vasopressin levels were significantly greater in HFpEF [0.96 pg/mL; 95% confidence interval (CI) = 0.83–1.1 pg/mL] compared with subjects without HF (0.69 pg/mL; 95% CI = 0.6–0.77 pg/mL; P = 0.0002). Heart failure with preserved ejection fraction (but not HFrEF) was a significant predictor of higher AVP after adjustment for potential confounders. Arginine vasopressin levels were independently associated with a greater LA volume and also paradoxically, with lower ANP levels. Key independent correlates of higher AVP were the presence of HFpEF (standardized β = 0.32; 95% CI = 0.09–0.56; P = 0.0073) and the ANP/LA volume ratio (standardized β = −0.23; 95% CI = −0.42 to −0.04; P = 0.0196). Arginine vasopressin levels were independently associated with LV mass (β = 0.26; 95% CI = 0.09–0.43; P = 0.003) and with an increased risk of death or HF admissions during follow‐up (hazard ratio = 1.61; 95% CI = 1.13–2.29; P = 0.008).

Conclusions

Arginine vasopressin is increased in HFpEF and is associated with LV hypertrophy and poor outcomes. Higher AVP is associated with the combination of LA enlargement and paradoxically low ANP levels. These findings may indicate that a relative deficiency of ANP (an inhibitor of AVP secretion) in the setting of chronically increased LA pressure may contribute to AVP excess.