Low serum magnesium and the development of atrial fibrillation in the community: the Framingham Heart Study.

BACKGROUND: Low serum magnesium has been linked to increased risk of atrial fibrillation (AF) after cardiac surgery. It is unknown whether hypomagnesemia predisposes to AF in the community. METHODS AND RESULTS: We studied 3530 participants (mean age, 44 years; 52% women) from the Framingham Offspring Study who attended a routine examination and were free of AF and cardiovascular disease. We used Cox proportional hazard regression analysis to examine the association between serum magnesium at baseline and risk of incident AF. Analyses were adjusted for conventional AF risk factors, use of antihypertensive medications, and serum potassium. During up to 20 years of follow-up, 228 participants developed AF. Mean serum magnesium was 1.88 mg/dL. The age- and sex-adjusted incidence rate of AF was 9.4 per 1000 person-years (95% confidence interval, 6.7-11.9) in the lowest quartile of serum magnesium (≤1.77 mg/dL) compared with 6.3 per 1000 person-years (95% confidence interval, 4.1-8.4) in the highest quartile (≥1.99 mg/dL). In multivariable-adjusted models, individuals in the lowest quartile of serum magnesium were ~50% more likely to develop AF (adjusted hazard ratio, 1.52; 95% confidence interval, 1.00-2.31; P=0.05) compared with those in the upper quartiles. Results were similar after the exclusion of individuals on diuretics. CONCLUSIONS: Low serum magnesium is moderately associated with the development of AF in individuals without cardiovascular disease. Because hypomagnesemia is common in the general population, a link with AF may have potential clinical implications. Further studies are warranted to confirm our findings and to elucidate the underlying mechanisms.

Lack of association between serum magnesium and the risks of hypertension and cardiovascular disease.

BACKGROUND: Experimental studies have linked hypomagnesemia with the development of vascular dysfunction, hypertension, and atherosclerosis. Prior clinical studies have yielded conflicting results but were limited by the use of self-reported magnesium intake or short follow-up periods. METHODS: We examined the relationship between serum magnesium concentration and incident hypertension, cardiovascular disease (CVD), and mortality in 3,531 middle-aged adult participants in the Framingham Heart Study offspring cohort. Analyses were performed using Cox proportional hazards regressions, adjusted for traditional CVD risk factors. RESULTS: Follow-up was 8 years for new-onset hypertension (551 events) and 20 years for CVD (554 events). There was no association between baseline serum magnesium and the development of hypertension (multivariable-adjusted hazards ratio per 0.15 mg/dL 1.03, 95% CI 0.92-1.15, P = .61), CVD (0.83, 95% CI 0.49-1.40, P = .49), or all-cause mortality (0.77, 95% CI 0.41-1.45, P = .42). Similar findings were observed in categorical analyses, in which serum magnesium was modeled in categories (<1.5, 1.5-2.2, >2.2 mg/dL) or in quartiles. CONCLUSIONS: In conclusion, data from this large, community-based cohort do not support the hypothesis that low serum magnesium is a risk factor for developing hypertension or CVD.

Too little too late? Communication with patients with congenital heart disease about challenges of adult life.

OBJECTIVE: To investigate the experiences and communication preferences of adult patients with congenital heart disease (CHD) in the domains of employment, insurance, and family planning. DESIGN: Patients ≥ 18 years of age completed a questionnaire about experiences and communication preferences regarding employment, health insurance, and family planning. RESULTS: Of 152 patients (median age = 33 years, 50% female, 35% with CHD of great complexity), one in four reported work-related problems due to CHD and a quarter also recalled a previous gap in health insurance. Of females, 29% experienced an unplanned pregnancy. The median importance of discussion ratings (on a 0-10 scale) were 3.5 (employment), 6.0 (insurance), and 8.0 (family planning). Few patients recalled discussions about employment (19%) or health insurance (20%). Over half recalled discussions about family planning, although males were less likely to have had these discussions than females (24% vs 86%, P < .001). Across the three domains, patients identified 16-18 years as the most appropriate age to initiate discussion, although for patients who recalled discussions, they typically occurred between 20 and 25 years. CONCLUSIONS: Adults with CHD commonly face employment, health insurance, and family planning challenges. However, discussions about these matters occur with less frequency than recommended and at older ages than patients would prefer. Communication about such issues should be incorporated into a comprehensive educational curriculum for adolescents during the process of transition to adult care.

Prevalence and Correlates of Post-traumatic Stress Disorder in Adults With Congenital Heart Disease.

Post-traumatic stress disorder (PTSD) is associated with adverse outcomes and increased mortality in cardiac patients. No studies have examined PTSD in the adult congenital heart disease (ACHD) population. The objectives of this study were to assess the prevalence of self-reported symptoms of PTSD in patients with ACHD and explore potential associated factors. Patients were enrolled from an outpatient ACHD clinic and completed several validated measures including the Impact of Event Scale-Revised, PTSD Checklist-Civilian Version, and the Hospital Anxiety and Depression Scale. Clinical data were abstracted through medical data review. A total of 134 participants (mean age 34.6 ± 10.6; 46% men) were enrolled. Of the 127 participants who completed the Impact of Event Scale-Revised, 14 (11%) met criteria for elevated PTSD symptoms specifically related to their congenital heart disease or treatment. Of the 134 patients who completed PTSD Checklist-Civilian Version, 27 (21%) met criteria for global PTSD symptoms. In univariate analyses, patients with congenital heart disease-specific PTSD had their most recent cardiac surgery at an earlier year (p = 0.008), were less likely to have attended college (p = 0.04), had higher rates of stroke or transient ischemic attack (p = 0.03), and reported greater depressive symptoms on the Hospital Anxiety and Depression Scale (7 vs 2, p <0.001). In multivariable analysis, the 2 factors most strongly associated with PTSD were depressive symptoms (p <0.001) and year of most recent cardiac surgery (p <0.03). In conclusion, PTSD is present in 11% to 21% of subjects seen at a tertiary referral center for ACHD. The high prevalence of PTSD in this complex group of patients has important implications for the medical and psychosocial management of this growing population.

Weight loss, saline loading, and the natriuretic peptide system.

BACKGROUND: In epidemiologic studies, obesity has been associated with reduced natriuretic peptide (NP) concentrations. Reduced NP production could impair the ability of obese individuals to respond to salt loads, increasing the risk of hypertension and other disorders. We hypothesized that weight loss enhances NP production before and after salt loading. METHODS AND RESULTS: We enrolled 15 obese individuals (mean BMI 45±5.4 kg/m(2)) undergoing gastric bypass surgery. Before and 6 months after surgery, subjects were admitted to the clinical research center and administered a large-volume intravenous saline challenge. Echocardiography and serial blood sampling were performed. From the pre-operative visit to 6 months after surgery, subjects had a mean BMI decrease of 27%. At the 6-month visit, N-terminal pro-atrial NP (Nt-proANP) levels were 40% higher before, during, and after the saline infusion, compared with levels measured at the same time points during the pre-operative visit (P<0.001). The rise in Nt-pro-ANP induced by the saline infusion (≈50%) was similar both before and after surgery (saline, P<0.001; interaction, P=0.2). Similar results were obtained for BNP and Nt-proBNP; resting concentrations increased by 50% and 31%, respectively, after gastric bypass surgery. The increase in NP concentrations after surgery was accompanied by significant decreases in mean arterial pressure (P=0.004) and heart rate (P<0.001), and an increase in mitral annular diastolic velocity (P=0.02). CONCLUSION: In obese individuals, weight loss is associated with a substantial increase in the "setpoint" of circulating NP concentrations. Higher NP concentrations could contribute to an enhanced ability to handle salt loads after weight loss.

Cardiopulmonary exercise testing in adults with congenital heart disease.

Adults with congenital heart disease (CHD) are at high risk for morbidity and mortality. Identifying those who are at highest risk of complications can be challenging, in part because self-reported functional status is not a reliable indicator of physiological status. Individuals with CHD may present with exercise limitation due to a variety of cardiac and non-cardiac causes. Cardiopulmonary exercise testing (CPET) provides an integrated assessment of cardiac, pulmonary, and metabolic function and can identify the source of exercise limitation in many patients. Because CPET parameters have also been associated with outcome in adults with CHD, CPET has recently emerged as an important prognostic indicator in this population.

Effects of subacute dietary salt intake and acute volume expansion on diastolic function in young normotensive individuals.

AIMS: Chronic excess salt intake may have blood pressure-independent adverse effects on the heart such as myocardial hypertrophy and fibrosis. Effects of subacute sodium loading with excess dietary salt on diastolic function in normotensive individuals have been conflicting and the mechanisms are poorly understood. METHODS AND RESULTS: Thirteen healthy normotensive subjects (age 24 ± 4 years) entered a 2-week crossover study with 1 week of a low-salt diet <10 mEq/day and 1 week of a high-salt diet >200 mEq/day. At the end of each study week, left ventricular dimensions, systolic, and diastolic function were assessed with echocardiography before and after 2 L of normal saline infusion. One week of high-salt and low-salt diets did not lead to differences in echocardiographic parameters of systolic or diastolic function, even after rapid volume expansion with saline infusion. The peak early diastolic strain rate (SR) increased after volume loading both after completion of low-salt (1.62 ± 0.23/s vs. 1.82 ± 0.14/s, P < 0.05) and high-salt diets (1.67 ± 0.16/s vs. 1.86 ± 0.22/s, P < 0.05). There was a positive correlation between the peak early diastolic SR and the cardiac index (r = 0.52, P = 0.017). CONCLUSION: In healthy normotensive individuals, subacute excess dietary sodium intake does not affect diastolic function. The peak early diastolic SR, similar to other mitral Doppler and tissue Doppler parameters of diastolic function, appears to be strongly dependent on pre-load.

Atrial natriuretic peptide is negatively regulated by microRNA-425.

Numerous common genetic variants have been linked to blood pressure, but no underlying mechanism has been elucidated. Population studies have revealed that the variant rs5068 (A/G) in the 3' untranslated region of NPPA, the gene encoding atrial natriuretic peptide (ANP), is associated with blood pressure. We selected individuals on the basis of rs5068 genotype (AG vs. AA) and fed them a low- or high-salt diet for 1 week, after which they were challenged with an intravenous saline infusion. On both diets, before and after saline administration, ANP levels were up to 50% higher in AG individuals than in AA individuals, a difference comparable to the changes induced by high-salt diet or saline infusion. In contrast, B-type natriuretic peptide levels did not differ by rs5068 genotype. We identified a microRNA, miR-425, that is expressed in human atria and ventricles and is predicted to bind the sequence spanning rs5068 for the A, but not the G, allele. miR-425 silenced NPPA mRNA in an allele-specific manner, with the G allele conferring resistance to miR-425. This study identifies miR-425 as a regulator of ANP production, raising the possibility that miR-425 antagonists could be used to treat disorders of salt overload, including hypertension and heart failure.

FGF-23 and the progression of coronary arterial calcification in patients new to dialysis.

BACKGROUND AND OBJECTIVE: Fibroblast growth factor 23 (FGF-23), a regulator of phosphorus metabolism, is a risk marker in CKD. FGF-23 has been associated with coronary arterial calcification (CAC), but it is not known whether FGF-23 predicts CAC progression in CKD. The aim of this study was to evaluate the association of FGF-23 with CAC progression in advanced CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: FGF-23 levels and CAC were measured by electrocardiography-triggered multislice computed tomography in 99 individuals initiating dialysis. Patients were enrolled in the study from April 2008 to July 2010. CAC was calculated using Agatston and calcium volume score. Sixty-seven study participants had repeat CAC measures at 1 year. Linear regression was used to assess the association of FGF-23 with CAC. RESULTS: The mean age of study participants was 50 years; 33% were women, and 64% were black. The median FGF-23 level was 1238 relative units (RU)/ml (interquartile range, 515-2218 RU/ml). According to Agatston score, FGF-23 was not associated with baseline CAC (P=0.14) but was significantly associated with CAC progression. There was a 192.3-Agatston unit change in CAC score per 1-SD change in FGF-23 (P=0.008) in models adjusting for known risk factors for CAC and serum phosphate. This association persisted after adjustment for high-sensitivity C-reactive protein, 25-OH vitamin D levels, and the use of phosphorus binders. Results were similar when change in calcium volume score was used. CONCLUSIONS: In individuals with advanced CKD, serum FGF-23 is strongly associated with CAC progression. FGF-23 may be a marker of cardiovascular risk in CKD.

Cardiac Magnetic Resonance Imaging in Ischemic Heart Disease.

Coronary artery disease (CAD) is the leading cause of death in the adult population in the United States. Imaging is an essential component of the management of CAD, providing both diagnostic and prognostic information. This review provides an overview of the use of cardiovascular magnetic resonance (CMR) imaging in the evaluation of ischemia in both acute and chronic settings. The authors compare CMR imaging with other imaging modalities, highlighting the advantages and opportunities of CMR imaging, as well as limitations.

Relation of visceral adiposity to circulating natriuretic peptides in ambulatory individuals.

Natriuretic peptides have important roles in the regulation of vasomotor tone, salt homeostasis, and ventricular remodeling. Lower natriuretic peptide levels observed in obese individuals may underlie the greater cardiovascular risk associated with obesity. Thus the aim of this study was to determine whether lower natriuretic peptide levels in obesity are attributable to differences in regional fat distribution. We investigated the relation of plasma N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) to regional adiposity in 1,873 community-based individuals (46% women, mean age 45 years). Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes were measured by multidetector computed tomography. In gender-specific multivariable analyses adjusting for age and blood pressure, log NT-pro-BNP was inversely associated with VAT in men (beta -0.11 per standard deviation increment, p <0.001) and women (beta -0.19, p <0.001). Log NT-pro-BNP was inversely associated with SAT in women only (beta -0.14, p <0.001). In models containing VAT and SAT, only VAT was significantly associated with log NT-pro-BNP (men, beta -0.137, p <0.001; women, beta -0.184, p <0.001). VAT remained associated with log NT-pro-BNP even after adjustment for body mass index and waist circumference (beta -0.119, p <0.001) and in analyses restricted to nonobese patients (beta -0.165, p <0.001). Adjustment for insulin resistance attenuated the associations of NT-pro-BNP with VAT and SAT. In conclusion, this study demonstrates that circulating NT-pro-BNP is related to variations in regional and particularly visceral adiposity. These findings suggest that excess visceral adiposity and concomitant hyperinsulinemia may contribute to the natriuretic peptide "deficiency" observed in obesity.

Cardiac natriuretic peptides, obesity, and insulin resistance: evidence from two community-based studies.

BACKGROUND: The natriuretic peptides play an important role in salt homeostasis and blood pressure regulation. It has been suggested that obesity promotes a relative natriuretic peptide deficiency, but this has been a variable finding in prior studies and the cause is unknown. AIM: The aim of this study was to examine the association between obesity and natriuretic peptide levels and evaluate the role of hyperinsulinemia and testosterone as mediators of this interaction. METHODS: We studied 7770 individuals from the Framingham Heart Study (n = 3833, 54% women) and the Malmö Diet and Cancer study (n = 3918, 60% women). We examined the relation of plasma N-terminal pro-B-type natriuretic peptide levels (N-BNP) with obesity, insulin resistance, and various metabolic subtypes. RESULTS: Obesity was associated with 6-20% lower levels of N-BNP (P < 0.001 in Framingham, P = 0.001 in Malmö), whereas insulin resistance was associated with 10-30% lower levels of N-BNP (P < 0.001 in both cohorts). Individuals with obesity who were insulin sensitive had only modest reductions in N-BNP compared with nonobese, insulin-sensitive individuals. On the other hand, individuals who were nonobese but insulin resistant had 26% lower N-BNP in Framingham (P < 0.001) and 10% lower N-BNP in Malmö (P < 0.001), compared with nonobese and insulin-sensitive individuals. Adjustment for serum-free testosterone did not alter these associations. CONCLUSIONS: In both nonobese and obese individuals, insulin resistance is associated with lower natriuretic peptide levels. The relative natriuretic peptide deficiency seen in obesity could be partly attributable to insulin resistance, and could be one mechanism by which insulin resistance promotes hypertension.

Preload dependency of left ventricular torsion: the impact of normal saline infusion.

BACKGROUND: left ventricular (LV) rotation results from contraction of obliquely oriented myocardial fibers. The net difference between systolic apical counterclockwise rotation and basal clockwise rotation is left ventricular torsion (LVT). Although LVT is altered in various cardiac diseases, determinants of LVT are incompletely understood. METHODS AND RESULTS: LV end-diastolic volume, LV apical and basal rotation, peak systolic LVT, and peak early diastolic untwisting rate were measured by speckle-tracking echocardiography in healthy subjects (n=8) before and after infusion of a weight-based normal saline bolus (2.1±0.3 L). Saline infusion led to a significant increase in end-diastolic LV internal diameter (45.9±3.7 versus 47.6±4.2 mm; P=0.002) and LV end-diastolic volume (90.0±21.6 versus 98.3±19.6 mL; P=0.01). Stroke volume (51.3±10.9 versus 63.0±15.5 mL; P=0.003) and cardiac output (3.4±0.8 versus 4.4±1.5 L/min; P=0.007) increased, whereas there was no change in heart rate and blood pressure. There was a significant increase in the magnitude of peak systolic apical rotation (7.5±2.4° versus 10.5±2.8°; P<0.001) but no change in basal rotation (-4.1±2.3° versus -4.8±3.1°; P=0.44). Accordingly, peak systolic LVT increased by 33% after saline infusion (11.2±1.3° versus 14.9±1.7°; P<0.001). This saline-induced increase in LVT was associated with a marked increase in peak early diastolic untwisting rate (72.3±21.4 versus 136.8±30.0 degrees/s; P<0.001). CONCLUSIONS: peak systolic LVT and peak early diastolic untwisting rate are preload-dependent. Changes in LV preload should be considered when interpreting results of future LVT studies.

Effect of weight loss after weight loss surgery on plasma N-terminal pro-B-type natriuretic peptide levels.

Natriuretic peptides have multiple beneficial cardiovascular effects. Previous cross-sectional studies have indicated that obese subjects have lower natriuretic peptide concentrations than those of normal weight. It is not known whether this relative natriuretic peptide deficiency is reversible with weight loss. We studied 132 obese subjects undergoing weight loss surgery with serial measurement of plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations at preoperative, early (1 to 2 months), and late postoperative (6 months) points. In addition, 20 subjects also underwent echocardiography at baseline and 6 months after surgery. Significant weight loss was observed after surgery (median body mass index 45.1, 41.0, and 32.9 kg/m(2) for the 3 corresponding points, analysis of variance p <0.001). The median NT-proBNP levels increased substantially (31.6, 66.9, and 84.9 pg/ml; p <0.001). The average intrasubject increase in NT-proBNP at the 2 postoperative points was 3.4 and 5.0 times the preoperative level (p <0.001 for both points vs preoperatively). In the multivariate regression models adjusted for clinical characteristics and insulin resistance, the strongest predictor of the change in NT-proBNP level 6 months after weight loss surgery was the change in weight (p = 0.03). Echocardiography showed a mean intrasubject reduction in left ventricular mass index of 18% (p <0.001) and mild improvements in diastolic function, with no change in ejection fraction. In conclusion, we have demonstrated that weight loss is associated with early and sustained increases in NT-proBNP concentrations, despite evidence of preserved systolic and improved diastolic function. These findings suggest a direct, reversible relation between obesity and reduced natriuretic peptide levels.