Comparison of right and left ventricular function in obese and nonobese men

Retained Metabolic Flexibility of the Failing Human Heart

BACKGROUND

The failing heart is traditionally described as metabolically inflexible and oxygen starved, causing energetic deficit and contractile dysfunction. Current metabolic modulator therapies aim to increase glucose oxidation to increase oxygen efficiency of adenosine triphosphate production, with mixed results.

METHODS

To investigate metabolic flexibility and oxygen delivery in the failing heart, 20 patients with nonischemic heart failure with reduced ejection fraction (left ventricular ejection fraction 34.9±9.1) underwent separate infusions of insulin+glucose infusion (I+G) or Intralipid infusion. We used cardiovascular magnetic resonance to assess cardiac function and measured energetics using phosphorus-31 magnetic resonance spectroscopy. To investigate the effects of these infusions on cardiac substrate use, function, and myocardial oxygen uptake (MVo2), invasive arteriovenous sampling and pressure-volume loops were performed (n=9).

RESULTS

At rest, we found that the heart had considerable metabolic flexibility. During I+G, cardiac glucose uptake and oxidation were predominant (70±14% total energy substrate for adenosine triphosphate production versus 17±16% for Intralipid; P=0.002); however, no change in cardiac function was seen relative to basal conditions. In contrast, during Intralipid infusion, cardiac long-chain fatty acid (LCFA) delivery, uptake, LCFA acylcarnitine production, and fatty acid oxidation were all increased (LCFA 73±17% of total substrate versus 19±26% total during I+G; P=0.009). Myocardial energetics were better with Intralipid compared with I+G (phosphocreatine/adenosine triphosphate 1.86±0.25 versus 2.01±0.33; P=0.02), and systolic and diastolic function were improved (LVEF 34.9±9.1 baseline, 33.7±8.2 I+G, 39.9±9.3 Intralipid; P<0.001). During increased cardiac workload, LCFA uptake and oxidation were again increased during both infusions. There was no evidence of systolic dysfunction or lactate efflux at 65% maximal heart rate, suggesting that a metabolic switch to fat did not cause clinically meaningful ischemic metabolism.

CONCLUSIONS

Our findings show that even in nonischemic heart failure with reduced ejection fraction with severely impaired systolic function, significant cardiac metabolic flexibility is retained, including the ability to alter substrate use to match both arterial supply and changes in workload. Increasing LCFA uptake and oxidation is associated with improved myocardial energetics and contractility. Together, these findings challenge aspects of the rationale underlying existing metabolic therapies for heart failure and suggest that strategies promoting fatty acid oxidation may form the basis for future therapies.

Effect of continuous positive airway pressure on atrial remodeling and diastolic dysfunction of patients with obstructive sleep apnea and metabolic syndrome: a randomized study

OBJECTIVE

The aim of this study was to evaluate the role of obstructive sleep apnea (OSA) treatment on heart remodeling and diastolic dysfunction in patients with metabolic syndrome (MS).

METHODS

This study is a prespecified analysis of a randomized placebo-controlled trial that enrolled patients with a recent diagnosis of MS and moderate-to-severe OSA to undergo continuous positive airway pressure (CPAP) or nasal dilators (placebo) for 6 months. Patients were invited to perform a transthoracic echocardiogram by a single investigator blinded to treatment assignment.

RESULTS

A total of 99 (79% men; mean [SD], age: 48 [9] years; BMI: 33 [4] kg/m² ) completed the study. At follow-up, in the placebo group, patients had a significant increase in atrial diameter: from 39.5 (37.0-43.0) mm to 40.5 (39.0-44.8) mm (p = 0.003). CPAP prevented atrial enlargement: from 40.0 (38.0-44.0) to 40.0 (39.0-45.0) mm (p = 0.194). In patients with diastolic dysfunction at baseline, almost half had diastolic dysfunction reversibility with CPAP (in comparison with only two patients in the placebo group, p = 0.039). In the regression analysis, the chance of diastolic dysfunction reversibility by CPAP was 6.8-fold (95% CI: 1.48-50.26, p = 0.025) compared with placebo.

CONCLUSIONS

In patients with MS and OSA, 6 months of CPAP therapy prevented atrial remodeling and increased the chance of diastolic dysfunction reversibility.

Fat cardiomyopathy in patients with severe degree of obesity. Case report

Currently, the world is constantly increasing the number of people with obesity. As was shown by the Framingham study, obesity is a risk factor for many cardiovascular diseases. The effect of obesity on the structure and function of the heart is manifested in the form of cardiac remodeling, the effect on energy metabolism in the heart and infiltration of both myocardium with lipids, and an increase in the accumulation of adipose tissue in the pericardium, imbalance of adipokines and activation of inflammatory markers. Cardiac remodeling occurs primarily due to thickening of the left ventricle (LV) walls and an increase in the LV myocardium mass. Systolic dysfunction of the heart is less common in obese individuals compared with diastolic dysfunction. However, more modern methods (tissue Doppler, visualization of the deformation of the chambers of the heart strain imaging) reveal a subclinical decrease in systolic function in people with obesity. It is not fully known whether obesity is associated with systolic dysfunction, regardless of other risk factors. In any case, it has been proven that heart failure in people with obesity can develop independently of other risk factors. As an illustration, we give an example when the presence of obesity and concomitant pathology (arterial hypertension, diabetes) led to the development of systolic dysfunction with a decrease in the LV ejection fraction to 35% (fat cardiopathy), which show the potential for the influence of both obesity itself and in combination with concomitant diseases to lead to severe systolic heart failure.

Left ventricular myocardial oxygen demand and subclinical dysfunction in patients with severe obesity referred for bariatric surgery

BACKGROUND AND AIMS

Increased myocardial oxygen (O₂) demand carries higher cardiovascular risk in hypertension. We hypothesized that myocardial O₂ demand is increased in severe obesity and linked to early left ventricular (LV) dysfunction.

METHODS AND RESULTS

Baseline data from 106 severely obese subjects referred for gastric bypass surgery (42 ± 11 years, 74% women, body mass index [BMI] 41.9 ± 4.8 kg/m², 32% with hypertension) in the prospective FatWest (Bariatric Surgery on the West Coast of Norway) study was used. LV systolic function was assessed by biplane ejection fraction (EF), midwall shortening (MWS) and endocardial global longitudinal strain (GLS), and LV diastolic function by mitral annular early diastolic velocity (e'). Myocardial O₂ demand was estimated from the LV mass-wall stress-heart rate product (high if > 1.62 × 10⁶/2.29 × 10⁶ g kdyne/cm² bpm in women/men). High myocardial O₂ demand was found in 33% and associated with higher BMI and high prevalence of low GLS (65%) and low MWS (63%) despite normal EF. In ROC analyses, higher myocardial O₂ demand discriminated between patients with low vs. normal MWS and GLS (area under curve 0.71 and 0.63, p < 0.05). In successive multiple regression analyses, higher myocardial O₂ demand was associated with lower LV MWS, GLS and average e', respectively, independent of age, gender, BMI, pulse pressure, diabetes mellitus, and EF (all p < 0.05).

CONCLUSION

In obese patients without known heart disease and with normal EF referred for bariatric surgery, high myocardial O₂ demand is associated with lower myocardial function whether assessed by GLS or MWS independent of confounders. CLINICALTRIALS.

GOV IDENTIFIER

NCT01533142.

Cardiac remodeling in patients with childhood-onset craniopharyngioma-results of HIT-Endo and KRANIOPHARYNGEOM 2000/2007

Hypothalamic obesity caused by childhood-onset craniopharyngioma results in long-term cardiovascular morbidity. Knowledge about clinical markers and risk factors for cardiovascular morbidity is scarce. A cross-sectional study on transthoracic echocardiographic parameters was performed to determine the associations with clinical and anthropometric parameters in 36 craniopharyngioma patients. BMI correlated with the thickness of interventricular septum in diastole (IVSd) (r = 0.604, p < 0.001) and left ventricular posterior wall thickness in diastole (LVPWd) (r = 0.460, p = 0.011). In multivariate analyses on risk factors for cardiac remodeling, sex hormone replacement therapy, BMI, and male gender were positively correlated with increased left ventricular internal diameter in diastole (LVIDd), R² = 0.596, F = 10.323, p < 0.001. BMI and insulin resistance were selected as significant independent determinants of IVSd, produced R² = 0.655, F = 29.441, p < 0.001. Due to a wide range of disease duration, 17 pediatric and 19 adult patients were analyzed separately. In the adult subgroup (age at study ≥ 18 years), BMI correlated with IVSd (r = 0.707, p = 0.003), LVPWd (r = 0.592, p = 0.020), and LVIDd (r = 0.571, p = 0.026). In the pediatric subgroup (age at study < 18 years), no correlation between transthoracic echocardiography (TTE) parameters and BMI was observed. Only LVIDd correlated with disease duration (r = 0.645, p < 0.001). All cardiac functions were within the normal range, indicating no association with functional impairments.Conclusion: Cardiac remodeling in patients with craniopharyngioma correlated with the degree of hypothalamic obesity, disease duration, sex hormone replacement therapy, male gender, and insulin resistance. As echocardiography has limited sensitivity in patients with obesity, further research on more sensitive techniques for cardiac diagnostics in craniopharyngioma patients is warranted. What is Known: •Long-term prognosis in survivors of craniopharyngioma is impaired by obesity and cardiovascular disease. •Associations between echocardiographic findings and clinical and anthropometric parameters after craniopharyngioma are not yet analyzed. What is New: •In patients with childhood-onset craniopharyngioma, cardiac remodeling was associated with hypothalamic obesity, duration of disease, male gender sex hormone replacement, and insulin resistance. •Due to reduced echocardiographic sensitivity caused by obesity-related technical limitations, more sensitive cardiac diagnostics should be considered.

Noninvasive In Vivo Assessment of Cardiac Metabolism in the Healthy and Diabetic Human Heart Using Hyperpolarized 13C MRI

RATIONALE

The recent development of hyperpolarized 13C magnetic resonance spectroscopy has made it possible to measure cellular metabolism in vivo, in real time.

OBJECTIVE

By comparing participants with and without type 2 diabetes mellitus (T2DM), we report the first case-control study to use this technique to record changes in cardiac metabolism in the healthy and diseased human heart.

METHODS AND RESULTS

Thirteen people with T2DM (glycated hemoglobin, 6.9±1.0%) and 12 age-matched healthy controls underwent assessment of cardiac systolic and diastolic function, myocardial energetics (31P-magnetic resonance spectroscopy), and lipid content (1H-magnetic resonance spectroscopy) in the fasted state. In a subset (5 T2DM, 5 control), hyperpolarized [1-13C]pyruvate magnetic resonance spectra were also acquired and in 5 of these participants (3 T2DM, 2 controls), this was successfully repeated 45 minutes after a 75 g oral glucose challenge. Downstream metabolism of [1-13C]pyruvate via PDH (pyruvate dehydrogenase, [13C]bicarbonate), lactate dehydrogenase ([1-13C]lactate), and alanine transaminase ([1-13C]alanine) was assessed. Metabolic flux through cardiac PDH was significantly reduced in the people with T2DM (Fasted: 0.0084±0.0067 [Control] versus 0.0016±0.0014 [T2DM], Fed: 0.0184±0.0109 versus 0.0053±0.0041; P=0.013). In addition, a significant increase in metabolic flux through PDH was observed after the oral glucose challenge (P<0.001). As is characteristic of diabetes mellitus, impaired myocardial energetics, myocardial lipid content, and diastolic function were also demonstrated in the wider study cohort.

CONCLUSIONS

This work represents the first demonstration of the ability of hyperpolarized 13C magnetic resonance spectroscopy to noninvasively assess physiological and pathological changes in cardiac metabolism in the human heart. In doing so, we highlight the potential of the technique to detect and quantify metabolic alterations in the setting of cardiovascular disease.

Obesity and Mechanisms of its Negative Impact on the Cardiovascular System

Currently, the number of obese people in the world is constantly increasing. Obesity has a direct negative impact on the heart and blood vessels, which can be considered not only as an appropriate response to an increase in the volume of circulating blood due to an increase in body weight, but also as a side tissue reaction of the myocardium to hormonal and metabolic changes inherent in obesity. Our review is devoted to the description of the mechanisms of influence of obesity on the structural and functional parameters of the heart, which create prerequisites for the development of cardiovascular diseases, as well as the existing contradictions. Currently, the accumulated data suggest that an excessive amount of adipose tissue, in addition to metabolic disorders, including insulin resistance, imbalance of adipokines and inflammation markers, leading to the development of lipotoxicity, can directly penetrate the myocardium and cause violations of its contractile properties, as well as affect the conduction of excitation pulses and provoke the development of rhythm and conduction disorders. The development of endothelial dysfunction in obesity ultimately leads to the development of atherosclerosis and coronary heart disease. In addition, obesity contributes to the emergence of risk factors for hypertension, diabetes, atrial fibrillation, chronic heart failure, obstructive sleep apnea syndrome. Given the differences in the literature on the effect of obesity on long-term outcomes in patients with cardiovascular diseases, it is important to conduct prospective studies on the role of individual factors and their combinations that affect the mortality of patients with cardiovascular diseases.

Cardiac Structure and Function in Morbidly Obese Parturients: An Echocardiographic Study

BACKGROUND

The increasing prevalence of obesity worldwide is a major threat to global health. Cardiac structural and functional changes are well documented for obesity as well as for pregnancy, but there is limited literature on morbidly obese parturients. We hypothesized that there are both cardiac structural and functional differences between morbidly obese pregnant women and pregnant women of normal body mass index (BMI).

METHODS

This prospective cross-sectional study was performed in 2 referral maternity units in Cape Town, South Africa, over a 3-month period. Forty morbidly obese pregnant women of BMI ≥40 kg·m (group O) were compared to 45 pregnant women of BMI ≤30 kg·m (group N). Cardiac structure and function were assessed by transthoracic echocardiography, according to the recommendations of the British Society of Echocardiography. The 2-sample t-test with unequal variances was used for the comparison of the mean values between the groups.

RESULTS

Acceptable echocardiographic images were obtained in all obese women. Statistical significance was defined as P < .0225 after applying the Benjamini-Hochberg correction for multiple testing. Mean (standard deviation) mean arterial pressure was higher in group O (91 [8.42] vs 84 [9.49] mm Hg, P < .001). There were no between-group differences in heart rate, stroke volume, or cardiac index (84 [12] vs 79 [13] beats·minute, P = .103; 64.4 [9.7] vs 59.5 [13.5] mL, P = .069; 2551 [474] vs 2729 [623] mL·minute·m, P = .156, for groups O and N, respectively). Stroke volume index was lower, and left ventricular mass was higher in group O (30.14 [4.51] vs 34.25 [7.00] mL·m, P = .003; 152 [24] vs 115 [29] g, P < .001). S' septal was lower in group O (8.43 [1.20] vs 9.25 [1.64] cm·second, P = .012). Considering diastolic function, isovolumetric relaxation time was significantly prolonged in group O (73 [15] vs 61 [15] milliseconds, P < .001). The septal tissue Doppler index E' septal was lower in group O (9.08 [1.69] vs 11.28 [3.18], P < .001). There were no between-group differences in E' average (10.7 [2.3] vs 12.0 [2.7], P = .018, O versus N) or E/E' average (7.85 [1.77] vs 7.27 [1.68], P = .137, O versus N). Right ventricular E'/A' was lower in group O (1.07 [0.47] vs 1.29 [0.32], P = .016).

CONCLUSIONS

Cardiac index did not differ between obese pregnant women and those with normal BMI. Their increased left ventricular mass and lower stroke volume index could indicate a limited adaptive reserve. Obese women had minor decreases in septal left ventricular tissue Doppler velocity, but the E/E' average values did not suggest clinically significant diastolic dysfunction.

The relative contribution of metabolic and structural abnormalities to diastolic dysfunction in obesity

Background:

Obesity causes diastolic dysfunction, and is one of the leading causes of heart failure with preserved ejection fraction. Myocardial relaxation is determined by both active metabolic processes such as impaired energetic status and steatosis, as well as intrinsic myocardial remodelling. However, the relative contribution of each to diastolic dysfunction in obesity is currently unknown.

Methods:

Eighty adult subjects (48 male) with no cardiovascular risk factors across a wide range of body mass indices (18.4–53.0 kg m⁻²) underwent magnetic resonance imaging for abdominal visceral fat, left ventricular geometry (LV mass:volume ratio) and diastolic function (peak diastolic strain rate), and magnetic resonance spectroscopy for PCr/ATP and myocardial triglyceride content.

Results:

Increasing visceral obesity was related to diastolic dysfunction (peak diastolic strain rate, r=−0.46, P=0.001). Myocardial triglyceride content (β=−0.2, P=0.008), PCr/ATP (β=−0.22, P=0.04) and LV mass:volume ratio (β=−0.61, P=0.04) all independently predicted peak diastolic strain rate (model R² 0.36, P<0.001). Moderated multiple regression confirmed the full mediating roles of PCr/ATP, myocardial triglyceride content and LV mass:volume ratio in the relationship between visceral fat and peak diastolic strain rate. Of the negative effect of visceral fat on diastolic function, 40% was explained by increased myocardial triglycerides, 39% by reduced PCr/ATP and 21% by LV concentric remodelling.

Conclusions:

Myocardial energetics and steatosis are more important in determining LV diastolic function than concentric hypertrophy, accounting for more of the negative effect of obesity on diastolic function than LV geometric remodelling. Targeting these metabolic processes is an attractive strategy to treat diastolic dysfunction in obesity.

Effect of Bariatric Surgery on Emergency Department Visits and Hospitalizations for Atrial Fibrillation

Atrial fibrillation (AF) and obesity are major health problems in the United States. However, little is known about whether bariatric surgery affects AF-related morbidities. This study investigated whether bariatric surgery is associated with short-term and long-term changes in the risk of emergency department (ED) visits or hospitalizations for AF. We performed a self-controlled case series study of obese adults with AF who underwent bariatric surgery by using population-based ED and inpatient databases in California, Florida, and Nebraska from 2005 to 2011. The primary outcome was ED visit or hospitalization for AF. We used conditional logistic regression to compare each patient's risk of the outcome event during sequential 12-month periods, using presurgery months 13 to 24 as a reference period. Our sample consisted of 523 obese adults with AF who underwent bariatric surgery. The median age was 57 years (interquartile range 48 to 64 years), 59% were female, and 84% were non-Hispanic white. During the reference period, 15.9% (95% confidence interval [CI] 12.7% to 19.0%) of patients had an ED visit or hospitalization for AF. The risk remained similar in the subsequent 12-month presurgery period (adjusted OR [aOR] 1.29 [95% CI, 0.94 to 1.76] p = 0.11). In contrast, the risk significantly increased within 12 months after bariatric surgery (aOR 1.53 [95% CI 1.13 to 2.07] p = 0.006). The risk remained elevated during 13-24 months after bariatric surgery (aOR 1.41 [95% CI, 1.03 to 1.91] p = 0.03). In conclusion, this population-based study demonstrated that bariatric surgery was associated with an increased risk of AF episodes requiring an ED visit or hospitalization for at least 2 years after surgery among obese patients with AF.

Right ventricular function measured by TAPSE in obese subjects at the time of acute myocardial infarction and 2year outcomes

INTRODUCTION

Obesity is associated with significantly better outcome after acute myocardial infarction (AMI), a phenomenon known as 'obesity paradox'. Tricuspid annular plane systolic excursion (TAPSE) is an echocardiographic measurement of right ventricular (RV) function and has prognostic implications at the time of AMI.

METHODS

We examined the difference in RV function among patients admitted with AMI according to obesity status. In a single center cohort analysis of 105 patients admitted between 2010 and 2011 with the diagnosis of AMI. Demographic, anthropometric data and cardiovascular risk factors were prospectively collected. All subjects had echocardiogram within 48h of AMI diagnosis for TAPSE calculations. Subjects were divided into two groups based on their obesity status.

RESULTS

Obese subjects had better RV function compared to non-obese, TAPSE: 19±6.6 vs. 16±4.9mm; p 0.02 at the time of AMI. There was no significant difference in TAPSE between OSA and non-OSA subjects, 19±6.3 vs. 17±6.2mm; p 0.21. After 2years of follow up, patients with obesity and better RV function were less likely to develop new onset heart failure (HF) with OR 0.30 (95% CI 0.09-0.93; p 0.03) and OR 0.31 (95% CI 0.11-0.76; p 0.007) respectively.

CONCLUSION

Obese patients had better RV function measured by TAPSE at the time AMI when compared non-obese patients. Patients with better RV function at the time of AMI were less likely to develop new-onset HF and there was a trend in the obese group to less likely develop new-onset HF after 2year follow up.

Assessment of left atrial volume and function by real time three-dimensional echocardiography in obese patients

OBJECTIVE

To evaluate left atrial (LA) volume and functions in obese subjects using real time three-dimensional echocardiography (RT3DE) and also the relationship between LA mechanical functions and N-terminal pro-atrial natriuretic peptide (NT-proANP).

METHODS

This study included 40 obese (26 females and 14 males, mean age 51.9 years) and 40 normal weight subjects (23 females and 16 males, mean age 53.5 years) with normal coronary angiograms. All the study participants underwent RT3DE to assess LA volume and mechanical function. Plasma NT-proANP was determined by ELISA method.

RESULTS

There was no significant difference between groups in left ventricular (LV) diameters and ejection fraction, which reflect LV systolic function. However, transmitral deceleration time, isovolumetric relaxation time, and peak late diastolic tissue Doppler velocity values, which reflect LV diastolic function, were found to be significantly higher in obese subjects when compared with controls. LA maximum volume (LAVmax), LAVmax index (LAVI), LA minimal volume (LAVmin), before atrial contraction volume (LAVpreA), LA active emptying volume, LA total emptying volume, and LA active emptying fraction, which reflect LA reservoir and pump functions, were also higher in obese subjects when compared with controls. LA passive emptying fraction was significantly lower in obese subjects than in controls. NT-proANP levels were similar between groups. There were positive correlations between NT-proANP level and LAVI, LAVmax, LAVmin, LAVpreA, and LA total and active emptying volumes.

CONCLUSIONS

Left atrial mechanical functions and volumes are impaired in obese subjects. These findings may be regarded as early markers of subclinical cardiac failure in obese subjects who have not yet exhibited any clinical evidence of cardiovascular disease.

Effects of Obesity on Cardiovascular Hemodynamics, Cardiac Morphology, and Ventricular Function

Obesity produces a variety of hemodynamic alterations that may cause changes in cardiac morphology which predispose to left and right ventricular dysfunction. Various neurohormonal and metabolic alterations commonly associated with obesity may contribute to these abnormalities of cardiac structure and function. These changes in cardiovascular hemodynamics, cardiac morphology, and ventricular function may, in severely obese patients, predispose to heart failure, even in the absence of other forms of heart disease (obesity cardiomyopathy). In normotensive obese patients, cardiac involvement is commonly characterized by elevated cardiac output, low peripheral vascular resistance, and increased left ventricular (LV) end-diastolic pressure. Sleep-disordered breathing may lead to pulmonary arterial hypertension and, in association with left heart failure, may contribute to elevation of right heart pressures. These alterations, in association with various neurohormonal and metabolic abnormalities, may produce LV hypertrophy; impaired LV diastolic function; and less commonly, LV systolic dysfunction. Many of these alterations are reversible with substantial voluntary weight loss.

The paradox of obesity cardiomyopathy and the potential for weight loss as a therapy

Obesity is an independent risk factor for developing heart failure and the combination of the two disease states will prove to be a significant health burden over the coming years. Obesity is likely to contribute to the development of heart failure through a variety of mechanisms, including structural and functional changes, lipotoxicity and steatosis and altered substrate selection. However, once heart failure has developed, it seems that obesity confers a beneficial influence on prognosis in what has been termed the 'obesity paradox'. This may be a statistical phenomenon, but it should be considered that there is truly a protective state in the physiology of obesity. There is little evidence regarding the impact of weight loss in obese heart failure and whether or not this is beneficial. There have been small studies regarding the cardiovascular effects of both dietary weight loss and bariatric surgery, but few in heart failure. This is an important and increasingly relevant clinical question which must be addressed.

Obesity and atrial fibrillation: A comprehensive review of the pathophysiological mechanisms and links

Obesity is a worldwide health problem with epidemic proportions that has been associated with atrial fibrillation (AF). Even though the underlying pathophysiological mechanisms have not been completely elucidated, several experimental and clinical studies implicate obesity in the initiation and perpetuation of AF. Of note, hypertension, diabetes mellitus, metabolic syndrome, coronary artery disease, and obstructive sleep apnea, represent clinical correlates between obesity and AF. In addition, ventricular adaptation, diastolic dysfunction, and epicardial adipose tissue appear to be implicated in atrial electrical and structural remodeling, thereby promoting the arrhythmia in obese subjects. The present article provides a concise overview of the association between obesity and AF, and highlights the underlying pathophysiological mechanisms.

Successful weight reduction improves left ventricular diastolic function and physical performance in severe obesity

Obesity and the metabolic syndrome (MetS) are risk factors for left ventricular diastolic dysfunction (LVDD). However, little is known about the impact of successful weight reduction (WR) on diastolic function and physical performance.Obese subjects (øBMI 40.2 ± 8.6 kg/m(2)) underwent a 1-year WR program comprising diet and lifestyle components. Echocardiography and exercise capacity (6-minute walk) were performed at baseline and after 1 year. The distribution of weight reduction was split at the sample median and subjects were dichotomized in "successful WR" (% WR ≥ median, corresponding to a weight loss of 8%) and "failed-WR" (% WR < median).From a total of 188 obese subjects, 71 had LVDD at baseline. Obese patients with successful WR improved their MetS alterations, including fasting glucose, insulin, lipids, adipokines, blood pressure levels, and epicardial fat thickness. The same was not true for obesity with failed WR. Subjects with successful WR demonstrated significant improvement in echocardiographic LVDD parameters (median [interquartile range]): Δe' (2,5 [-1.0, 4.7], P < 0.01), Δe'/a' (0.34 [0.07, 079], P < 0.01), ΔE/e' (-1.14 [-2.72, -0.54], P < 0.05), ΔE/A (0.08 [-0.04, 0.26], P < 0.05), ΔArd-Ad (-28 [-54, -4], P < 0.01), and 6-minute walk distance (65 [19, 135], P < 0.01). Improvement of ≥ 2 LVDD criteria was accomplished in 30% of subjects with WR versus 10% without (P = 0.009). Using multivariable regression analysis, reduction of epicardial fat thickness was particularly predictive for the improvement of diastolic function.In summary, in severe obesity, successful long-term WR was associated with improved LV diastolic function and exercise capacity.

Obesity and heart failure: epidemiology, pathophysiology, clinical manifestations, and management

Obesity is a risk factor for heart failure (HF) in both men and women. The mortality risk of overweight and class I and II obese adults with HF is lower than that of normal weight or underweight adults with HF of comparable severity, a phenomenon referred to as the obesity paradox. Severe obesity produces hemodynamic alterations that predispose to changes in cardiac morphology and ventricular function, which may lead to the development of HF. The presence of systemic hypertension, sleep apnea, and hypoventilation, comorbidities that occur commonly with severe obesity, may contribute to HF in such patients. The resultant syndrome is known as obesity cardiomyopathy. Substantial weight loss in severely obese persons is capable of reversing most obesity-related abnormalities of cardiac performance and morphology and improving the clinical manifestations of obesity cardiomyopathy.

Structural and Metabolic Effects of Obesity on the Myocardium and the Aorta

Obesity per se is a recognized risk factor for cardiovascular disease exerting independent adverse effects on the cardiovascular system. Despite this well documented link, the mechanisms by which obesity modulates cardiovascular risk are not well understood. Obesity is linked to a wide variety of cardiac changes, from subclinical diastolic dysfunction to end stage systolic heart failure. In addition, obesity causes changes in cardiac metabolism that make ATP production and utilization less efficient producing functional consequences that are linked to the increased rate of heart failure in this population. This review focuses on the cardiovascular structural and metabolic remodelling that occurs in obesity with and without co-morbidities and the potential links to increased mortality in this population. © 2014 S. Karger GmbH, Freiburg.

Metabolic syndrome and right ventricle: an updated review

The cluster of metabolic and hemodynamic abnormalities which characterize the metabolic syndrome (MS) is responsible for subclinical cardiac and extra-cardiac damage such as left ventricular hypertrophy, diastolic dysfunction, carotid atherosclerosis and microalbuminuria. The development of different non-invasive imaging methods enabled a detail investigation of right ventricular structure and function, and revealed that right ventricular remodeling followed changes in the left ventricular structure and function in patients with arterial hypertension, diabetes or obesity. Previous investigations also reported that the coexistence of two components of the MS induced more significant cardiac remodeling than the presence of only one MS risk-factor. The relationship between different components of the MS (increased blood pressure, abdominal obesity, increased fasting glucose level and dyslipidemia) and right ventricular remodeling could be explained by several hemodynamic and non-hemodynamic mechanisms. However, the association between right ventricular remodeling and the MS has not been sufficiently investigated so far. The aim of this article was to review recent articles focusing on the association between metabolic syndrome components and the metabolic syndrome itself with impairments in right ventricular structure and function assessed by different imaging techniques.

The impact of isolated obesity on right ventricular function in young adults

Background

Obesity is an independent risk factor for cardiovascular diseases. The effects of obesity on left ventricular structure and function have been reported, but relatively little is known regarding right ventricular (RV) function in obesity.

Objective

To evaluate subclinical RV alterations in obese, but otherwise healthy, young adults by conventional echocardiography and tissue Doppler imaging (TDI).

Methods

In this study, we included 35 normal weight healthy subjects with a body mass index (BMI) < 25 kg/m² (group I), 27 subjects with a BMI of 30-34.99 kg/m² (group II), and 42 subjects with a BMI ≥ 35 kg/m² (group III). All subjects underwent transthoracic echocardiography. In addition to standard echocardiographic measurements, tricuspid annular peak systolic (Sm), peak early (Em), and late diastolic (Am) velocities, isovolumetric contraction (ICTm), relaxation (IRTm) time, and ejection time (ETm) were obtained by TDI, and RV myocardial performance index (MPIm) was calculated.

Results

In group II, RV Em/Am was significantly decreased and IRTm and MPIm were significantly increased compared to group I (p < 0.01). RV Sm, Em, and the Em/Am ratio were significantly lower and RV IRTm and MPIm were significantly higher in group III than in group II (p < 0.05 for RV Sm and IRTm and p < 0.01 for others). RV Am differed significantly between groups III and I (p < 0.05). BMI was significantly and negatively correlated with RV Sm, Em, and the Em/Am ratio, but positively correlated with RV MPI (p < 0.01).

Conclusion

Our study showed that isolated obesity in young normotensive adults was associated with subclinical abnormalities in RV structure and function.

Myocardial substrate metabolism in obesity

Obesity is linked to a wide variety of cardiac changes, from subclinical diastolic dysfunction to end-stage systolic heart failure. Obesity causes changes in cardiac metabolism, which make ATP production and utilization less efficient, producing functional consequences that are linked to the increased rate of heart failure in this population. As a result of the increases in circulating fatty acids and insulin resistance that accompanies excess fat storage, several of the proteins and genes that are responsible for fatty acid uptake and metabolism are upregulated, and the metabolic machinery responsible for glucose utilization and oxidation are inhibited. The resultant increase in fatty acid metabolism, and the inherent alterations in the proteins of the electron transport chain used to create the gradient needed to drive mitochondrial ATP production, results in a decrease in efficiency of cardiac work and a relative increase in oxygen usage. These changes in cardiac mitochondrial metabolism are potential therapeutic targets for the treatment and prevention of obesity-related heart failure.

Effects of weight loss on myocardial energetics and diastolic function in obesity

A reduced myocardial phosphocreatine/adenosine triphosphate (PCr/ATP) ratio is linked to both diastolic dysfunction and heart failure. Although obesity is well known to cause diastolic dysfunction a link to impaired cardiac energetics has only recently been established. We assessed whether or not long-term weight loss in obesity, which is known to reduce mortality, is accompanied by both improved cardiac energetics and diastolic function. Normal weight (BMI 22 ± 2; n = 18) and obese subjects (BMI 34 ± 4; n = 13) underwent cine-MRI (1.5 Tesla) to determine left ventricular diastolic function using volume-time curve analysis, and (31)P-MR spectroscopy (3 Tesla) to assess cardiac energetics (PCr/ATP ratio). Obese subjects (n = 13) underwent repeat assessment after 1 year of supervised weight loss. Obesity, in the absence of identifiable cardiovascular risk factors, was associated with significantly impaired myocardial high energy phosphate metabolism (PCr/ATP ratio, normal; 2.03 ± 0.27 vs. obese; 1.58 ± 0.47, p = 0.002) and significantly lower peak diastolic filling rate (normal; 4.8 ± 0.8 vs. obese; 3.8 ± 0.7 EDV/s, p = 0.01). Weight loss (on average 9 kg, 55% excess weight) over 1 year resulted in a 24% increase in PCr/ATP ratio (p = 0.01) and an 18% improvement in peak diastolic filling rate (p = 0.01). Myocardial PCr/ATP ratio remained positively correlated with peak diastolic filling rate after weight loss (r = 0.63, p = 0.02). In obesity, weight loss improves impaired cardiac energetics and myocardial relaxation. Improved myocardial energetics appear to play a key role in diastolic functional recovery accompanying weight loss.

Effects of catecholamine stress on diastolic function and myocardial energetics in obesity

BACKGROUND

Obesity is characterized by impaired cardiac energetics, which may play a role in the development of diastolic dysfunction and inappropriate shortness of breath. We assessed whether, in obesity, derangement of energetics and diastolic function is further altered during acute cardiac stress.

METHODS AND RESULTS

Normal-weight (body mass index, 22±2 kg/m(2); n=9-17) and obese (body mass index, 39±7 kg/m(2); n=17-46) subjects underwent assessment of diastolic left ventricular function (cine magnetic resonance imaging volume-time curve analysis) and cardiac energetics (phosphocreatine/ATP ratio; (31)P-magnetic resonance spectroscopy) at rest and during dobutamine stress (heart rate increase, 65±22% and 69±14%, respectively; P=0.61). At rest, obesity was associated with a 22% lower peak filling rate (P<0.001) and a 15% lower phosphocreatine/ATP ratio (1.73±0.40 versus 2.03±0.28; P=0.048). Peak filling rate correlated with fat mass, left ventricular mass, leptin, waist-to-hip ratio, and phosphocreatine/ATP ratio. On multivariable analysis, phosphocreatine/ATP was the only independent predictor of peak filling rate (β=0.50; P=0.03). During stress, a further reduction in phosphocreatine/ATP occurred in obese (from 1.73±0.40 to 1.53±0.50; P=0.03) but not in normal-weight (from 1.98±0.24 to 2.04±0.34; P=0.50) subject. For similar levels of inotropic stress, there were smaller increases in peak filling rate in obesity (38% versus 70%; P=0.01).

CONCLUSIONS

In obesity, cardiac energetics are further deranged during inotropic stress, in association with continued diastolic dysfunction. Myocardial energetics may play a key role in the impairment of diastolic function in obesity.

Strain imaging in morbid obesity: insights into subclinical ventricular dysfunction

BACKGROUND

Obesity has become an important health problem throughout the world. Early detection of cardiovascular abnormalities may be useful in the future for patient management. This study aimed to identify subclinical ventricular dysfunction in obese patients.

HYPOTHESIS

Morbid obesity is associated with ventricular dysfunction.

METHODS

Doppler echocardiogram was performed in 92 morbidly obese and in 31 healthy controls. Conventional echocardiography and tissue Doppler-based strain imaging were used to analyze ventricular function. Intra- and interobserver strain imaging variabilities were tested on 15 randomly selected cases.

RESULTS

Left ventricular (LV) global strain (22.5% ± 3.5 vs 24.4% ± 2.5, P<0.005) and right ventricular (RV) strain (25.8% ± 5.2 vs 28.2% ± 5.2, P<0.029) were lower in obese patients when compared with healthy controls. Echocardiographic parameters of diastolic function were also different from controls. LV strain correlated with LV mass, E/e' ratio, left atrial volume, and RV strain. At multivariate analysis, morbid obesity remained a significant determinant of global LV strain, independently of associated comorbidities.

CONCLUSIONS

These findings suggest that incipient biventricular dysfunction is present in morbidly obese patients when new echocardiographic indices are used to investigate ventricular function. In addition, strain imaging may provide a more accurate assessment of the ventricular function in obese patients.

Impact of Body Mass Index on Left Ventricular Function

BACKGROUND

Obesity is associated with increased cardiovascular morbidity and mortality. A direct effect of isolated obesity on cardiac function is not well established. The study was designed to determine the direct effect of various grades of isolated obesity on echocardiographic indices of systolic and diastolic left ventricular function.

METHODS

Fifty one obese and 25 normal weight, serving personnel without any other pathological condition were studied. Group I (n=25) consisted of subjects with normal weight and body mass index (BMI <25kg/m(2)), Group II (n=34) of overweight subjects (BMI 25-29.9 kg/m(2)) and Group III (n=17) of obese subjects (BMI >30 kg/m(2)). Echocardiographic indices of systolic and diastolic function were obtained and dysfunction was assumed when at least two values differed by ≥ 2 SD from the normal weight group.

RESULT

Ejection fraction, fractional shortening were increased (p<0.05) in Group II and III. Left ventricular dimensions were increased (p< 0.001) but relative wall thickness was unchanged. Systolic dysfunction was not observed in any of the obese patients. The mitral valve pressure half time (p< 0.01), left atrial diameter (p < 0.01) and the deceleration time were increased (p< 0.01) in obese subjects, while other diastolic variables were unchanged. No difference were found between obesity subgroups. Subclinical diastolic dysfunction was more prevalent among obese subjects. BMI correlated significantly with indices of left ventricular systolic and diastolic function.

CONCLUSION

Subclinical left ventricular diastolic dysfunction was noted in all grades of obesity which correlates with BMI.

Epicardial adipose tissue and relationship with coronary artery disease

Epicardial adipose tissue (EAT) is metabolically active tissue that accumulates around the coronary arteries. Epicardial fat is a rich source of free fatty acids and may contribute to local inflammatory load by increased synthesis of inflammatory cytokines. Direct passage of bioactive molecules into the coronary arteries due to close contact with the vascular wall and the lack of fascia may contribute to the pathogenesis of coronary artery disease. Direct correlation between visceral fat and EAT defines the latter as an indirect marker of intra-abdominal visceral adiposity. EAT is related to anthropometric and clinical features of the metabolic syndrome (MS) and to hepatic transaminases as markers of steatohepatitis. An increase in EAT thickness is related to an increase in left ventricular mass and is correlated with atrial enlargement and impairment in diastolic filling in obesity. Echocardiographic study of EAT is an easy and reliable imaging indicator of visceral adiposity and cardiovascular risk. EAT is an independent factor strongly correlated with significant coronary stenosis. A level of EAT above an established average value can be considered a predictive marker of cardiovascular risk. We review the most recent studies proving the specific active role of EAT in the development of cardiac disease.

A pilot study of patients with clinically severe obesity undergoing laparoscopic surgery: evidence for impaired cardiac performance

OBJECTIVE

Given the propensity for heart disease in obese patients, the authors investigated the effects of pneumoperitoneum on cardiac performance.

DESIGN

A pilot observational intraoperative study.

SETTING

A single-center university hospital.

PARTICIPANTS

Patients undergoing laparoscopic gastric bypass surgery.

INTERVENTIONS

Abdominal insufflation.

MEASUREMENTS AND RESULTS

Hemodynamic, respiratory, and echocardiographic data were collected at 4 epochs: (1) baseline after the induction of anesthesia, (2) after abdominal insufflation in supine position, (3) after abdominal insufflation in the reverse Trendelenburg (RT) position, and (4) after desufflation in RT position. At epoch 1, 3 of 13 patients manifested systolic dysfunction (SD), 5 of 13 patients exhibited diastolic dysfunction (DD) according to transmitral flow (TMF) Doppler criteria, and 4 of 8 patients according to Doppler tissue imaging (DTI) criteria. With pneumoperitoneum, the total systemic resistance increased to values of 142% from baseline (p < 0.05). Compared with baseline, stroke volume decreased by 25%, cardiac output by 35%, and fractional area change by 13% (p < 0.05). Mean arterial blood pressure and heart rate remained stable. Additionally, new-onset DD manifested in 1 of 8 patients according to TMF criteria and in 3 of 4 patients according to DTI criteria. Desufflation of the abdomen reverted the diastolic function to baseline in all but 1 patient.

CONCLUSION

The study data revealed that surgical pneumoperitoneum used in patients with clinically severe obesity resulted in the deterioration of cardiac performance including the development of new-onset DD. These patients, despite their relative young age and without a history of heart failure or coronary artery disease, displayed a cardiovascular profile during laparoscopic surgery similar to that seen in patients with significant heart disease.

Cardiac remodeling in a rat model of diet-induced obesity

The mechanisms by which diet-induced obesity cause remodeling and cardiac dysfunction are still unknown. Interstitial collagen and myocardial ultrastructure are important in the development of left ventricular hypertrophy, and are essential to the adaptive and maladaptive changes associated with obesity. Thus, the accumulation of collagen and ultrastructural damage may contribute to cardiac dysfunction in obesity. The purpose of the present study was to investigate cardiac function in a rat model of diet-induced obesity and to test the hypothesis that cardiac dysfunction induced by obesity is related to myocardial collagen deposition and ultrastructural damage. Thirty-day-old male Wistar rats were fed standard (control [C]) and hypercaloric diets (obese [Ob]) for 15 weeks. Cardiac function was evaluated by echocardiogram and isolated left ventricle papillary muscle. Cardiac morphology was assessed by histology and electron microscopy. Compared with C rats, Ob rats had increased body fat, systolic blood pressure and area under the curve for glucose, leptin and insulin plasma concentrations. Echocardiographic indexes indicated that Ob rats had increased left ventricular mass, increased systolic stress and depressed systolic function. Analysis of the isolated papillary muscle was consistent with higher myocardial stiffness in Ob compared with C rats. The Ob rats had an increase in myocardial collagen and marked ultrastructural changes compared with C rats. Obesity promotes pathological cardiac remodeling with systolic dysfunction and an increase in myocardial stiffness, which, in turn, is probably related to afterload elevation and cardiac fibrosis. Obesity also causes damage to myocardial ultrastructure, but its effect on myocardial function needs to be further clarified.

Therapeutic Implications of PPARgamma in Cardiovascular Diseases

Peroxisome proliferator-activated receptor-γ (PPARγ) is the members of the nuclear receptor superfamily as a master transcriptional factor that promotes differentiation of preadipocytes by activating adipose-specific gene expression. Although PPARγ is expressed predominantly in adipose tissue and associated with adipocyte differentiation and glucose homeostasis, PPARγ is also present in a variety of cell types including vascular cells and cardiomyocytes. Activation of PPARγ suppresses production of inflammatory cytokines, and there is accumulating data that PPARγ ligands exert antihypertrophy of cardiomyocytes and anti-inflammatory, antioxidative, and antiproliferative effects on vascular wall cells and cardiomyocytes. In addition, activation of PPARγ is implicated in the regulation of endothelial function, proliferation and migration of vascular smooth muscle cells, and activation of macrophages. Many studies suggest that PPARγ ligands not only ameliorate insulin sensitivity, but also have pleiotropic effects on the pathophysiology of atherosclerosis, cardiac hypertrophy, ischemic heart, and myocarditis.

The effect of surgical weight reduction on left ventricular structure and function in severe obesity

The aim of this study was to examine the effect of surgical weight reduction on cardiac structure and function and to seek the determinants of these changes. Sixty-six severely obese adults (BMI >or=35 kg/m(2)) who received bariatric surgery underwent echocardiographic examination before and 3 months after surgery. At 3 months after surgery, BMI and systolic blood pressure (BP) decreased (43.3 +/- 6.3 to 34.1 +/- 5.6 kg/m(2), P < 0.001, and 146 +/- 12 to 130 +/- 14 mm Hg, P < 0.001, respectively). In left ventricular (LV) geometry, the relative wall thickness (RWT) and LV mass index decreased significantly (0.43 +/- 0.05 to 0.35 +/- 0.05, P < 0.001, and 50 +/- 11 to 39 +/- 11 g/m(2.7), P < 0.001, respectively) without changes in chamber size. Multivariate analyses showed change in systolic BP to be an independent predictor for the changes in RWT and LV mass index. In myocardial performance, peak systolic mitral annular velocity and all diastolic indexes showed significant improvements. We concluded that LV hypertrophy and function improved rapidly after bariatric surgery in severely obese adults. BP reduction was the major determinant for the regression of LV hypertrophy in the early stage of surgical weight reduction.

Effects of weight loss on ventricular systolic and diastolic functions and left ventricular mass assessed by tissue doppler imaging in obese geriatric women: preliminary report

BACKGROUND AND AIMS

Obesity is one of the most common diseases in the world. Particularly in elderly subjects, the effects of weight loss on cardiac functions have not been previously investigated by means of pulsed wave tissue doppler imaging (PWTDI). Using PWTDI, we examined the effects of weight loss on cardiac functions and left ventricular (LV) mass in obese geriatric women.

METHODS

Thirteen obese women aged 66-83 years (mean age 71.2+/-4.9 yrs) with a body mass index 35.6-49 kg/m2 (mean body mass index 39.9+/-4.3 kg/m2) were evaluated by echocardiography and PWTDI. Only subjects with uncomplicated obesity were included. All measurements, including anthropometric variables, systolic and diastolic indices, and LV mass, were made before and after a 6-month Orlistat plus hypocaloric diet. Myocardial systolic wave (Sm) velocity, isovolumic acceleration (IVA), myocardial precontraction time (PCTm) and the PCTm to contraction time (CTm) ratio were calculated as systolic indices. Early diastolic wave (Em), late diastolic wave (Am), Em to Am ratio, myocardial relaxation time (RTm), deceleration time (DT) and isovolumic relaxation time (IVRT) were determined as diastolic measurements.

RESULTS

Subjects lost an average of 8.4+/-1.2 kg. LV mass decreased significantly after weight loss (p<0.001). In addition, IVRT decreased significantly (p=0.038). Only RTm decreased significantly (p=0.016), whereas other PWTDI parameters of LV remained the same. In the right ventricle, Sm velocity, IVA, Em, and Am velocities were similar. However, the PCTm to Am ratio decreased significantly (p=0.006), and the Em to Am ratio increased (p=0.04) and RTm decreased significantly (p=0.016) after weight loss.

CONCLUSIONS

In obese geriatric women, weight loss improves ventricular diastolic functions and decreases LV mass. It also contributes to partial improvement in right ventricular systolic function.

Right ventricular subclinical diastolic dysfunction in obese children: the effect of weight reduction with a low-carbohydrate diet

This study aimed primarily to identify whether childhood obesity leads to right ventricular (RV) subclinical diastolic dysfunction or not. It also aimed to examine the effect of weight reduction on right ventricular function. Standard and tissue Doppler echocardiography was performed for 28 overweight (body mass index [BMI], 25-30 kg/m(2)) and 34 obese (BMI, > or = 30 kg/m(2)) children and for 29 age- and sex-matched lean referents (BMI, 17-25 kg/m(2)). Levels of plasma lipids, fasting glucose, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) were obtained for all the participants. For 6 months, 30 obese children were given a low-carbohydrate diet and then reevaluated by echocardiography. Conventional echocardiographic parameters all were similar for obese, overweight, and lean control children. The tricuspid free-wall isovolumetric relaxation time (IVRT), tricuspid lateral annular early diastolic velocity (e'), ratio of early-to-late diastolic velocity (e'/a'), and tricuspid lateral annular IVRT differed significantly between the overweight and control children. The RV tissue Doppler parameters were found to be similar between the preobese and control children. The IVRT of the RV free wall and lateral tricuspid annulus was significantly decreased, and the e'/a' of the lateral tricuspid annulus was significantly increased after the diet. In conclusion, obesity is associated with subclinical RV diastolic dysfunction in pediatric patients. Weight reduction with a low-carbohydrate diet may reverse the effects of obesity on RV diastolic function.

Beneficial cardiovascular effects of bariatric surgical and dietary weight loss in obesity

OBJECTIVES

We hypothesized that, in obese persons without comorbidities, cardiovascular responses to excess weight are reversible during weight loss by either bariatric surgery or diet.

BACKGROUND

Obesity is associated with cardiac hypertrophy, diastolic dysfunction, and increased aortic stiffness, which are independent predictors of cardiovascular risk.

METHODS

Thirty-seven obese (body mass index 40 +/- 8 kg/m(2)) and 20 normal-weight subjects (body mass index 21 +/- 2 kg/m(2)) without identifiable cardiac risk factors underwent cardiac magnetic resonance imaging for the assessment of the left and right ventricles and of indexes of aortic function. Thirty of the obese subjects underwent repeat imaging after 1 year of significant weight loss, achieved in 17 subjects by diet and in 13 subjects by bariatric surgery. Seven obese subjects underwent repeat imaging after 1 year of continued obesity.

RESULTS

Left and right ventricular masses were significantly increased, left ventricular diastolic function impaired, and aortic distensibility reduced in the obese. Both diet and bariatric surgery led to comparable, significant decreases in left and right ventricular masses, end-diastolic volume, and diastolic dysfunction, and an increase in aortic distensibility at all levels of the aorta, most pronounced distally (e.g., distal descending aorta 5.1 +/- 1.8 mm Hg(-1) x 10(-3) before weight loss and 6.8 +/- 2.5 mm Hg(-1) x 10(-3) after weight loss; p < 0.001). No improvements were observed in continued obesity.

CONCLUSIONS

Irrespective of method, 1 year of weight loss leads to partial regression of cardiac hypertrophy and to reversal of both diastolic dysfunction and aortic distensibility impairment. These findings provide a potential mechanism for the reduction in mortality seen with weight loss.

Significance of peroxisome proliferator-activated receptors in the cardiovascular system in health and disease

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that belong to the nuclear receptor superfamily. Three isoforms of PPAR have been identified, alpha, delta and gamma, which play distinct roles in the regulation of key metabolic processes, such as glucose and lipid redistribution. PPARalpha is expressed predominantly in the liver, kidney and heart, and is primarily involved in fatty acid oxidation. PPARgamma is mainly associated with adipose tissue, where it controls adipocyte differentiation and insulin sensitivity. PPARdelta is abundantly and ubiquitously expressed, but as yet its function has not been clearly defined. Activators of PPARalpha (fibrates) and gamma (thiazolidinediones) have been used clinically for a number of years in the treatment of hyperlipidaemia and to improve insulin sensitivity in diabetes. More recently, PPAR activation has been found to confer additional benefits on endothelial function, inflammation and thrombosis, suggesting that PPAR agonists may be good candidates for the treatment of cardiovascular disease. In this regard, it has been demonstrated that PPAR activators are capable of reducing blood pressure and attenuating the development of atherosclerosis and cardiac hypertrophy. This review will provide a detailed discussion of the current understanding of basic PPAR physiology, with particular reference to the cardiovascular system. It will also examine the evidence supporting the involvement of the different PPAR isoforms in cardiovascular disease and discuss the current and potential future clinical applications of PPAR activators.

Cardiac remodeling in obesity

The dramatic increase in the prevalence of obesity and its strong association with cardiovascular disease have resulted in unprecedented interest in understanding the effects of obesity on the cardiovascular system. A consistent, but puzzling clinical observation is that obesity confers an increased susceptibility to the development of cardiac disease, while at the same time affording protection against subsequent mortality (termed the obesity paradox). In this review we focus on evidence available from human and animal model studies and summarize the ways in which obesity can influence structure and function of the heart. We also review current hypotheses regarding mechanisms linking obesity and various aspects of cardiac remodeling. There is currently great interest in the role of adipokines, factors secreted from adipose tissue, and their role in the numerous cardiovascular complications of obesity. Here we focus on the role of leptin and the emerging promise of adiponectin as a cardioprotective agent. The challenge of understanding the association between obesity and heart failure is complicated by the multifaceted interplay between various hemodynamic, metabolic, and other physiological factors that ultimately impact the myocardium. Furthermore, the end result of obesity-associated changes in the myocardial structure and function may vary at distinct stages in the progression of remodeling, may depend on the individual pathophysiology of heart failure, and may even remain undetected for decades before clinical manifestation. Here we summarize our current knowledge of this complex yet intriguing topic.

Major weight loss prevents long-term left atrial enlargement in patients with morbid and extreme obesity

AIMS

To assess long-term changes in left atrial (LA) volume in patients with morbid obesity [body mass index (BMI) >or=35 kg/m(2) with co-morbidities] and extreme obesity (BMI >or=40 kg/m(2)), after surgically-induced weight loss (WL) after gastric bypass surgery.

METHODS AND RESULTS

We reviewed 57 patients who underwent gastric bypass surgery and had echocardiograms both before and after the operation. A control group was frequency-matched for BMI, sex, age, and for duration of follow-up. After a mean follow-up of 3.6 years, LA volume did not change significantly in patients who underwent bariatric surgery, but increased in the control group by 15 +/- 28 ml (P < 0.0001), and 0.1 +/- 0.2 ml (P < 0.0001) for height-indexed LA volume, with a difference between cases and controls that remained significant after adjusting for potential confounders (P = 0.01). In the study population as a whole, there was a positive correlation between change in body weight and change in LA volume (r = 0.22, P = 0.006) independent of clinical conditions associated with LA enlargement.

CONCLUSION

Change in body weight is associated with change in LA size independent of obesity-associated co-morbidities. Successful WL induced by bariatric surgery prevents the progressive increase in LA volume.

Uncomplicated obesity is associated with abnormal aortic function assessed by cardiovascular magnetic resonance

AIMS

Obese subjects with insulin resistance and hypertension have abnormal aortic elastic function, which may predispose them to the development of left ventricular dysfunction. We hypothesised that obesity, uncomplicated by other cardiovascular risk factors, is independently associated with aortic function.

METHODS AND RESULTS

We used magnetic resonance imaging to measure aortic compliance, distensibility and stiffness index in 27 obese subjects (BMI 33 kg/m2) without insulin resistance and with normal cholesterol and blood pressure, and 12 controls (BMI 23 kg/m2). Obesity was associated with reduced aortic compliance (0.9 +/- 0.1 vs. 1.5 +/- 0.2 mm2/mmHg in controls, p < 0.02) and distensibility (3.3 +/- 0.01 vs. 5.6 +/- 0.01 mmHg-1 x 10-3, p < 0.02), as well as higher stiffness index (3.4 +/- 0.3 vs. 2.1 +/- 0.1, p < 0.02). Body mass index and fat mass were negatively correlated with aortic function. Leptin was higher in obesity (8.9 +/- 0.6 vs. 4.7 +/- 0.6 ng/ml, p < 0.001) and also correlated with aortic measures. In multiple regression models, fat mass, leptin and body mass index were independent predictors of aortic function.

CONCLUSION

Aortic elastic function is abnormal in obese subjects without other cardiovascular risk factors. These findings highlight the independent importance of obesity in the development of cardiovascular disease.