Supranormal Left Ventricular Ejection Fraction, Stroke Volume, and Cardiovascular Risk: Findings From Population-Based Cohort Studies

BACKGROUND

Supranormal ejection fraction by echocardiography in clinically referred patient populations has been associated with an increased risk of cardiovascular disease (CVD). The prognostic implication of supranormal left ventricular ejection fraction (LVEF)-assessed by cardiac magnetic resonance (CMR)-in healthy, community-dwelling individuals is unknown.

OBJECTIVES

The purpose of this study is to investigate the prognostic implication of supranormal LVEF as assessed by CMR and its inter-relationship with stroke volume among community-dwelling adults without CVD.

METHODS

Participants from the MESA (Multi-Ethnic Study of Atherosclerosis) and DHS (Dallas Heart Study) cohorts free of CVD who underwent CMR with LVEF above the normal CMR cutoff (≥57%) were included. The association between cohort-specific LVEF categories and risk of clinically adjudicated major adverse cardiovascular events (MACE) was assessed using adjusted Cox models. Subgroup analysis was also performed to evaluate the association of LVEF and risk of MACE among individuals stratified by left ventricular stroke volume index.

RESULTS

The study included 4,703 participants from MESA and 2,287 from DHS with 727 and 151 MACE events, respectively. In adjusted Cox models, the risk of MACE was highest among individuals in LVEF Q4 (vs Q1) in both cohorts after accounting for potential confounders (MESA: HR = 1.27 [95% CI: 1.01-1.60], P = 0.04; DHS: HR = 1.72 [95% CI: 1.05-2.79], P = 0.03). A significant interaction was found between the continuous measures of LVEF and left ventricular stroke volume index (P interaction = 0.02) such that higher LVEF was significantly associated with an increased risk of MACE among individuals with low but not high stroke volume.

CONCLUSIONS

Among community-dwelling adults without CVD, LVEF in the supranormal range is associated with a higher risk of adverse cardiovascular outcomes, particularly in those with lower stroke volume.

Abstract 15: The Use of Handheld Focused Cardiac Ultrasound (FoCUS) for EF Assessment at Parkland Memorial Hospital: A Quality Improvement Initiative With Novel Applications for Clinical Outcomes

Background: Focused cardiac ultrasound (FCU) has been used to answer clinical questions. Chemotherapy-related cardiotoxicity (CRR) is an entity that requires serial echocardiography. It is unknown whether FCU can be used to screen for CRR using advanced practice providers (APPs). The goal of this study is to determine if FCU can be used to reliably evaluate left ventricular ejection fraction (EF) by an APP to assess for CRR.

Methods: The study was conducted at the Echo lab and the Oncology clinic. An Oncology APP was trained on the use of FCU and EF analysis. The APP was trained to obtained standard 2D views for EF assessment and on EF interpretation. The EF assessment was compared to sonographer echocardiogram on the same day. EF was assessed by a cardiologist and this was deemed to be the gold standard. The studies were all analyzed by two separate blinded cardiologists and the degree of correlation was analyzed. Linear regression modeling to analyze correlation between EF interpretation between all blinded observers and Bland Altman analysis was performed. Image quality was evaluated for all FCU images by a single blinded cardiologist and segmental endocardial border delineation was scored.

Results: A total of 91 patients were scanned in Phase I of the study. The correlation coefficient between cardiologists was r=0.93. The correlation between cardiologist and APP were r=0.79 and 0.76 respectively. For the images obtained by the APP, the correlation between the APP and cardiologists were =0.83 and re=0.78. The correlation between APP and EF gold standard was r=0.77. The correlation between experienced cardiologists interpreting the FCU images was r=0.87. All images were determined to be interpretable.

Conclusions: There was good correlation between cardiologists with respect to EF analysis. There was also good correlation between APP and cardiologists for EF analysis. Image quality from FCU was found to be good and acceptable for interpretation. This study demonstrates it is feasible to train an APP on obtaining images for EF analysis and they can be trained on EF interpretation with good correlation with experienced echocardiographers. We will evaluate outcomes associated with its use including delays to chemotherapy imposed by traditional echocardiography, cost to the health care system and patient-reported outcomes.

Impact of Pregnancy on Maternal Cardiac Atria

Objective The aim of this study was to assess atrial changes across pregnancy and postpartum using cardiac magnetic resonance imaging (cMRI) to measure atrial end-diastolic volume (EDV).

Study Design This was a 2-year prospective observational study of healthy nulliparous women. Each underwent serial cMRI in both maternal left lateral and supine positions at five epochs: 12 to 16 weeks, 26 to 30 weeks, 32 to 36 weeks, within 48 hours after delivery, and 12 weeks postpartum. EDV was calculated and compared with 12-week postpartum values.

Results A total of 24 women completed the study. One woman developed preeclampsia, and her data were excluded. Mean age was 27 ± 2.8 years, and mean body mass index was 25.4 ± 3.8 kg/m2. Left atrial EDV increased by 12 weeks (p = 0.045) and remained significantly elevated through 32 to 36 (p < 0.0001) weeks. Maternal lateral positioning was associated with larger left atrial EDV after 12 weeks. Right atrial EDV was significantly elevated at 26 to 30 (p = 0.04) and 32 to 36 (p = 0.02) weeks in the lateral position, though there was no difference in the supine position.

Conclusion We documented a significant increase in EDV for both atria during pregnancy. Volume changes were greater in the lateral compared with the supine position, with the most dramatic changes in left atrium at 32 to 36 weeks.

Factors Associated With Left Atrial Remodeling in the General Population

BACKGROUND

Although contributors to remodeling of the left ventricle (LV) have been well studied in general population cohorts, few data are available describing factors influencing changes in left atrial (LA) structure.

METHODS AND RESULTS

Maximum LA volume was determined by cardiac magnetic resonance imaging among 748 participants in the Dallas Heart Study at 2 visits a mean of 8 years apart. Associations of changes in LA volume (ΔLAV) with traditional risk factors, biomarkers, LV geometry, and remodeling by cardiac magnetic resonance imaging and detailed measurements of global and regional adiposity (by magnetic resonance imaging and dual-energy x ray absorptiometry) were assessed using multivariable linear regression. Greater ΔLAV was independently associated with black and Hispanic race/ethnicity, change in systolic blood pressure, LV mass and ΔLV mass, N-terminal probrain natriuretic peptide and change in N-terminal probrain natriuretic peptide, and body mass index (P<0.05 for each). In subanalyses, the associations of ΔLAV with LV mass parameters were driven by associations with baseline and ΔLV end diastolic volume (P<0.0001 for each) and not wall thickness (P=0.21). Associations of ΔLAV with body mass index were explained exclusively by associations with visceral fat mass (P=0.002), with no association seen between ΔLAV and subcutaneous abdominal fat (P=0.47) or lower body fat (P=0.30).

CONCLUSIONS

Left atrial dilatation in the population is more common in black and Hispanic than in white individuals and is associated with parallel changes in the LV. LA dilatation may be mediated by blood pressure control and the development of visceral adiposity.

Lifelong Physical Activity Regardless of Dose Is Not Associated With Myocardial Fibrosis

BACKGROUND

Recent reports have suggested that long-term, intensive physical training may be associated with adverse cardiovascular effects, including the development of myocardial fibrosis. However, the dose-response association of different levels of lifelong physical activity on myocardial fibrosis has not been evaluated.

METHODS AND RESULTS

Seniors free of major chronic illnesses were recruited from predefined populations based on the consistent documentation of stable physical activity over >25 years and were classified into 4 groups by the number of sessions/week of aerobic activities ≥30 minutes: sedentary (group 1), <2 sessions; casual (group 2), 2 to 3 sessions; committed (group 3), 4 to 5 sessions; and Masters athletes (group 4), 6 to 7 sessions plus regular competitions. All subjects underwent cardiopulmonary exercise testing and cardiac magnetic resonance imaging, including late gadolinium enhancement assessment of fibrosis. Ninety-two subjects (mean age 69 years, 27% women) were enrolled. No significant differences in age or sex were seen between groups. Median peak oxygen uptake was 25, 26, 32, and 40 mL/kg/min for groups 1, 2, 3, and 4, respectively. Cardiac magnetic resonance imaging demonstrated increasing left ventricular end-diastolic volumes, end-systolic volumes, stroke volumes, and masses with increasing doses of lifelong physical activity. One subject in group 2 had late gadolinium enhancement in a noncoronary distribution, and no subjects in groups 3 and 4 had evidence of late gadolinium enhancement.

CONCLUSIONS

A lifelong history of consistent physical activity, regardless of dose ranging from sedentary to competitive marathon running, was not associated with the development of focal myocardial fibrosis.

Determinants of Racial/Ethnic Differences in Cardiorespiratory Fitness (from the Dallas Heart Study)

Previous studies have demonstrated ethnic/racial differences in cardiorespiratory fitness (CRF). However, the relative contributions of body mass index (BMI), lifestyle behaviors, socioeconomic status (SES), cardiovascular (CV) risk factors, and cardiac function to these differences in CRF are unclear. In this study, we included 2,617 Dallas Heart Study participants (58.6% women, 48.6% black; 15.7% Hispanic) without CV disease who underwent estimation of CRF using a submaximal exercise test. We constructed multivariable-adjusted linear regression models to determine the association between race/ethnicity and CRF, which was defined as peak oxygen uptake (ml/kg/min). Black participants had the lowest CRF (blacks: 26.3 ± 10.2; whites: 29.0 ± 9.8; Hispanics: 29.1 ± 10.0 ml/kg/min). In multivariate analysis, both black and Hispanic participants had lower CRF after adjustment for age and gender (blacks: Std β = -0.15; p value ≤0.0001, Hispanics: Std β = -0.05, p value = 0.01; ref group: whites). However, this association was considerably attenuated for black (Std β = -0.04, p value = 0.03) and no longer significant for Hispanic ethnicity (p value = 0.56) after additional adjustment for BMI, lifestyle factors, SES, and CV risk factors. Additional adjustment for stroke volume did not substantially change the association between black race/ethnicity and CRF (Std β = -0.06, p value = 0.01). In conclusion, BMI, lifestyle, SES, and traditional risk factor burden are important determinants of ethnicity-based differences in CRF.

Inhalant-Abuse Myocarditis Diagnosed by Cardiac Magnetic Resonance

Multiple reports of toxic myocarditis from inhalant abuse have been reported. We now report the case of a 23-year-old man found to have toxic myocarditis from inhalation of a hydrocarbon. The diagnosis was made by means of cardiac magnetic resonance imaging with delayed enhancement. The use of cardiac magnetic resonance to diagnose myocarditis has become increasingly common in clinical medicine, although there is not a universally accepted criterion for diagnosis. We appear to be the first to document a case of toxic myocarditis diagnosed by cardiac magnetic resonance. In patients with a history of drug abuse who present with clinical findings that suggest myocarditis or pericarditis, cardiac magnetic resonance can be considered to support the diagnosis.

Quality Improvement of Staphylococcus aureus Bacteremia Management and Predictors of Relapse-free Survival

PURPOSE

The purpose of this study is to improve the quality of care and patient outcomes for Staphylococcus aureus bacteremia.

METHODS

A quasi-experimental pre- and postintervention study design was used to compare process and clinical endpoints before and after a quality-improvement initiative. All inpatients >18 years of age with a positive blood culture for S. aureus during the specified pre- and postintervention period with clinical information available in the electronic medical record were included. An institutional protocol for the care of patients with S. aureus bacteremia was developed, formalized, and distributed to providers using a pocket card, an electronic order set, and targeted lectures over a 9-month period.

RESULTS

There were 167 episodes of S. aureus bacteremia (160 patients) identified in the preintervention period, and 127 episodes (123 patients) in the postintervention period. Guideline adherence improved in the postintervention period for usage of transesophageal echocardiogram (43.9% vs 20.2%, P <.01) and adequate duration of intravenous therapy (71% vs 60%, P = .05). In a multivariate Cox proportional hazard model, the variables associated with increased relapse-free survival were postintervention period (hazard ratio [HR] 0.48; confidence interval [CI], 0.24-0.95; P .035) and appropriate source control (HR 0.53; CI, 0.24-0.92; P .027). Regardless of intervention, presence of cancer was associated with an increased risk of relapse or mortality at 90 days (HR 2.88; P <.0001; CI, 1.35-5.01).

CONCLUSION

A bundled educational intervention to promote adherence to published guidelines for the treatment of S. aureus bacteremia resulted in a significant improvement in provider adherence to guidelines as well as increased 90-day relapse-free survival.

Abstract 239: Appropriateness and Impact of Transthoracic Echocardiography in a Veterans Affairs Health Care System

Background: Appropriate Use Criteria (AUC) for transthoracic echocardiograms (TTEs) was developed in 2007 and later revised in 2011 to meet the need for guidance on appropriate use of diagnostic imaging. Few studies have evaluated the correlation between AUC and downstream clinical impact. We describe the association of AUC and clinical impact for TTEs from a VA center.

Methods: All TTEs from April 2011 at a VA center were retrospectively reviewed. TTEs were excluded for LVAD/ transplant patients or for inadequate clinical data to assign AUC or clinical impact. Based on 2011 AUC , TTEs were classified as: appropriate, inappropriate, or uncertain. After blinding to AUC, TTEs were assessed for clinical impact as: change in care, continuation of current care, or no change in care.

Results: Among 441 TTEs (43% inpatient), 82.7% were appropriate, 9% inappropriate and 8% uncertain. Overall, change of care was seen in 39% of TTEs, continuation of current care in 32% and no change in care in 30%. Appropriate TTEs more frequently resulted in a change in care than inappropriate TTEs (41% vs. 23%, p<0.03, Figure 1).

Conclusions: Although only 8 in 10 TTEs were appropriate by 2011 AUC, almost 4 in 10 TTEs lead to an active change in care. Appropriate TTEs were more likely to change patient care than inappropriate TTEs. Additional research is needed to evaluate the association of clinical impact and differences in TTE practice at VA vs. non VA medical centers.

Potential of electron beam computed tomography for coronary artery calcium screening to evaluate fatty liver: comparison with 1H magnetic resonance spectroscopy in the Dallas Heart Study

OBJECTIVES

Electron beam computed tomography (EBCT) for coronary artery calcification can potentially evaluate liver fat, another marker of cardiovascular risk. We compared quantitative estimates of hepatic steatosis measured by EBCT with those obtained by a well-validated, accurate-measure, magnetic resonance spectroscopy ((1)H MRS).

METHODS

EBCT and (1)H MRS were performed in 2159 subjects from the Dallas Heart Study. Forty subjects were randomly selected from each of 5 subgroups of liver fat percent by (1)H MRS (n = 200). EBCT average liver attenuation (HU) was determined in a 1- to 2-cm circular region of interest over the liver lobes. Pearson correlation coefficients were calculated. Using a previously defined (1)H MRS hepatic steatosis cut point (>5.5%), an optimized EBCT liver attenuation cut point was determined by receiver operating characteristic analysis.

RESULTS

(1)H MRS liver fat content and EBCT average right lobe liver attenuation were moderately negatively correlated (r = -0.64, P < 0.0001) in all subjects and in those with (1)H MRS hepatic steatosis (r = -0.71, P < 0.0001). This correlation did not improve with attenuation correction of the EBCT data using a standard calcium phantom or statistical transformation. Using an optimized receiver operating characteristic EBCT cut point (64.5 HU), sensitivity was 78% and specificity was 72% for detecting (1)H MRS hepatic steatosis, with a high false negative rate. Risk factors for hepatic steatosis (obesity, diabetes mellitus, insulin resistance, metabolic syndrome) were more strongly correlated with (1)H MRS than EBCT liver fat measures.

CONCLUSIONS

Liver attenuation on EBCT acquired for coronary artery calcification screening correlates modestly with (1)H MRS measures of liver fat content, with a high false negative rate.

Circulating lymphotoxin β receptor and atherosclerosis: observations from the Dallas Heart Study

OBJECTIVE

Lymphotoxin β receptor (LTβR), a member of the tumor necrosis factor superfamily, binds ligands expressed by activated lymphocytes. Interruption of LTβR signaling improves autoimmune diseases and alters lipid homeostasis. We assayed circulating LTβR and examined its association with atherosclerosis phenotypes in a population-based sample.

METHODS AND RESULTS

Plasma LTβR was measured by ELISA in 3215 subjects enrolled in the Dallas Heart Study. Atherosclerosis was assessed using CT measurements of coronary calcium (CAC) and abdominal MRI measurements of aortic plaque (AP) (n=2252) and aortic wall thickness (AWT) (n=2265). We analyzed associations between LTβR and atherosclerosis using multivariable logistic and linear regression methods. Higher levels of LTβR associated with most traditional cardiovascular risk factors, multiple inflammatory markers, and markers of cardiac injury. Univariable analyses demonstrated significant associations of LTβR with CAC, AP, and AWT (p<0.0001 for each). In multivariable models adjusted for traditional risk factors, the 4th vs. the 1st quartile of LTβR remained associated with prevalent CAC, AP, and increased AWT (all p<0.05). Similar associations were observed when LTβR was modeled as a log-transformed continuous variable.

CONCLUSION

LTβR levels are independently associated with atherosclerosis in multiple vascular beds. These findings support further investigation of the lymphotoxin/LTβR pathway in atherosclerosis.

Long-term outcomes with ambrisentan monotherapy in pulmonary arterial hypertension

BACKGROUND

This study evaluated long-term outcomes in patients with pulmonary arterial hypertension (PAH) undergoing treatment with ambrisentan monotherapy, a selective oral endothelin-1 receptor antagonist.

METHODS AND RESULTS

Patients who participated in the Ambrisentan in Pulmonary Arterial Hypertension: A Phase 3, Randomized, Double-Blind, Placebo-Controlled Multicenter Efficacy Study (ARIES-1) clinical trial and extension phase at our institution were included. Cardiac catheterization, 6-minute walk distance (6MWD), and cardiac magnetic resonance (MRI) data were retrospectively reviewed. Twelve patients with PAH (11 idiopathic, 1 fenfluramine) had follow-up from 3 to 5.5 years from the initiation of ARIES-1. Patients received ambrisentan therapy throughout the study period and were on ambrisentan monotherapy for the first 2 years. At year 1, improvements in median mean pulmonary arterial pressure (PA), cardiac output, and pulmonary vascular resistance (PVR) were seen (P = .02, P = .03, P < .01), and the improvement in PVR persisted at 2 years. 6MWD also improved significantly between baseline (350 m) and 1 and 2 years (397 m, P < .01 and 393 m, P = .01). Cardiac MRI results were more varied, with an increase in RV ejection fraction from 29% at baseline to 46% at 2 years (P = .02), but other MRI variables did not improve.

CONCLUSIONS

Ambrisentan monotherapy led to improvements in catheterization, 6MWD, and RV ejection fraction, and shows promise as a long-term treatment for pulmonary arterial hypertension.

The association between plasma caspase-3, atherosclerosis, and vascular function in the Dallas Heart Study

BACKGROUND

Caspase-3, an apoptosis protease, is expressed in atherosclerotic plaques. We examined the relationship between plasma caspase-3 levels, aortic compliance, and atherosclerosis.

METHODS

Caspase-3 was measured in 3,221 subjects from the Dallas Heart Study. Electron beam computed tomography measures of coronary calcium (CAC) (n = 2,404) and magnetic resonance imaging (MRI) measures of abdominal aortic wall thickness (AWT) (n = 2,208) and aortic compliance (AC) (n = 2,328) were obtained. Multivariate analyses were performed, adjusting for age, sex, ethnicity, body mass index (BMI), traditional cardiovascular risk factors, and cardiac medications.

RESULTS

In univariable analysis, caspase-3 associated with CAC (P < 0.0001), AWT (P = 0.002), and AC (P < 0.0001). After multivariable adjustment, 4th quartile caspase-3 (compared to 1st quartile) was significantly associated with CAC (P = 0.004), AWT (P = 0.02), and AC (P < 0.0001) with similar findings for caspase-3 as a continuous variable.

CONCLUSIONS

Caspase-3 independently associates with CAC, AWT, and AC, suggesting a link between apoptosis and atherosclerosis.

Differentiating True Versus Pseudo Left Ventricular Aneurysm

The differentiation of left ventricular pseudoaneurysm from true aneurysm is sometimes difficult. Given the propensity for pseudoaneurysms to rupture leading to cardiac tamponade, shock, and death, compared with a more benign natural history for true aneurysms, accurate diagnosis of these conditions is clinically important. Clinical symptoms, physical examination findings, electrocardiograms, and routine x-rays are not sensitive or specific for diagnosing left ventricular aneurysms nor for distinguishing true from pseudoaneurysm once detected. Our aim is to present a case report demonstrating these difficulties and to review the use of various cardiac imaging modalities in differentiating between these 2 entities.