Exercise training in dilated cardiomyopathy improves rest and stress cardiac function without changes in cardiac high energy phosphate metabolism

Risk stratification and exercise recommendations in cardiomyopathies and channelopathies: a practical guide for the multidisciplinary team

Exercise offers a plethora of health benefits. However, certain genetic and acquired diseases such as cardiomyopathies and channelopathies are associated with sudden cardiac death during exercise. Several factors complicate exercise prescription in individuals living with these conditions. The lack of high-quality evidence supporting exercise recommendations, variation in the clinical phenotypes within the same condition and sparse physician education around exercise prescription all leads to a reluctance to provide specific guidance on how to engage in physical activity.This article aims to summarise the latest evidence underpinning risk stratification and current guideline recommendations for physical activity in individuals with cardiomyopathies and channelopathies wishing to engage in exercise. It also aims to provide a basic practical approach to exercise prescription for health professionals involved in the care of these patients. This approach may then serve as a foundation that can be easily personalised. Since risk can never be completely eliminated, all decisions regarding exercise participation should be taken following shared dialogue between the physician, patient and wider stake holders where appropriate.

Sport activity in patients with cardiomyopathies: a review

Exercise has undisputable benefits and is an important therapy component for most cardiovascular diseases, with a proven role in reducing mortality. On the contrary, exercise may paradoxically trigger sudden cardiac arrest in patients with cardiomyopathies requiring refrain from competitive sports participation. The 2020 European guidelines for patients with cardiovascular disease provided indication for sports participation for patients with cardiac conditions, including cardiomyopathies. Although in some cases, the knowledge of the natural history of the disease and the risk of death during intensive exercise is more robust, in others, the evidence is scarce. Therefore, recommendations are not available for all possible scenarios with several uncertainties. In addition, many patients aspire to continue competitive sports or practise recreational activities after a diagnosis of cardiomyopathy. These aspects generate concern for the physician, who should make complex decisions, and confronts the request to design specific exercise programmes without specific indications. This article will review the available evidence on the sports-related risk of sudden cardiac death or cardiovascular events and the progression of the disease in cardiomyopathies.

Cardiac 31P MR spectroscopy: development of the past five decades and future vision-will it be of diagnostic use in clinics?

In the past five decades, the use of the magnetic resonance (MR) technique for cardiovascular diseases has engendered much attention and raised the opportunity that the technique could be useful for clinical applications. MR has two arrows in its quiver: One is magnetic resonance imaging (MRI), and the other is magnetic resonance spectroscopy (MRS). Non-invasively, highly advanced MRI provides unique and profound information about the anatomical changes of the heart. Excellently developed MRS provides irreplaceable and insightful evidence of the real-time biochemistry of cardiac metabolism of underpinning diseases. Compared to MRI, which has already been successfully applied in routine clinical practice, MRS still has a long way to travel to be incorporated into routine diagnostics. Considering the exceptional potential of ³¹P MRS to measure the real-time metabolic changes of energetic molecules qualitatively and quantitatively, how far its powerful technique should be waited before a successful transition from "bench-to-bedside" is enticing. The present review highlights the seminal studies on the chronological development of cardiac ³¹P MRS in the past five decades and the future vision and challenges to incorporating it for routine diagnostics of cardiovascular disease.

Return to Sport From Viral Myocarditis in a Previously Healthy Collegiate Athlete: A Case Report

The objective of this paper is to present the case of a healthy, 19-year-old female collegiate soccer player who developed acute pulmonary edema and acute heart failure in the recovery room after hip labral arthroscopic surgery. The patient's initial diagnosis, of negative pressure pulmonary edema in direct relation to extubation, was questioned when she became hemodynamically unstable. A cardiac biopsy revealed acute pulmonary edema and heart failure secondary to viral myocarditis. The patient was treated and discharged 10 days after admission. Specific and substantiated return-to-play guidelines after a cardiac event, specifically viral myocarditis, have been sparse. The interprofessional collaboration between athletic trainers and cardiologists is a key dynamic in the clinical decision-making process of a safe return to competitive athletic participation after a cardiac event.

Prosthetic walking after bilateral transfemoral amputation in a patient with dilated cardiomyopathy: a case report

In this study, we present a case of a 14-year-old adolescent boy who developed rhabdomyolysis and underwent bilateral transfemoral amputation after cardiopulmonary resuscitation for cardiac arrest because of dilated cardiomyopathy (DCM). Patients with bilateral transfemoral amputation have slower walking velocity and greater oxygen consumption during walking. Rehabilitation of such patients may be demanding especially if they have DCM, one of the major causes of advanced heart failure. The patient was admitted to our hospital on postoperative day (POD) 206. At first, we started with residuum compression. Simultaneously, resistance training and range-of-motion exercise were performed. He started the walking training with short stubbies prostheses on POD 262. Then, we used two types of knee joint prostheses, microprocessor-controlled prosthetic knee (MPK) and non-MPK. We chose MPK for his bilateral knee joints because it was easier for him to walk with MPK than with non-MPK. MPK also has the advantage of high stability and less burden on the heart. He achieved to walk with the prosthesis using T-canes with both hands on POD 374. Furthermore, he was able to return to school after discharge. In patients with transfemoral amputations and DCM with exercise restrictions, MPK is preferred because it reduces cardiac load during physical activity.

Cardiac energetics alteration in a chronic hypoxia rat model: A non-invasive in vivo31P magnetic resonance spectroscopy study

BACKGROUND

Energetics alteration plays a crucial role in the myocardial injury process in chronic hypoxia diseases (CHD). 31P magnetic resonance spectroscopy (MRS) can investigate alterations in cardiac energetics in vivo.

OBJECTIVE

To characterize the potential value of 31P MRS in evaluating cardiac energetics alteration of chronic hypoxic rats (CHRs).

METHODS

Twenty-four CHRs were induced by SU5416 combined with hypoxia and divided into four groups according to the modeling time of one, two, three and five weeks, respectively. Control group also contains six rats. 31P MRS was performed weekly and the ratio of concentrations of phosphocreatine (PCr) to adenosine triphosphate (ATP) (PCr/ATP) was obtained. In addition, the cardiac structure index and systolic function parameters, including the right ventricular ejection fraction (RVEF), right ventricular end-diastolic volume index (RVEDVi), right ventricular end-systolic volume index (RVESVi), and the left ventricular function parameters, were measured.

RESULTS

Decreased resting cardiac PCr/ATP ratio in CHRs was observed at the first week, compared to the control group (2.90±0.35 vs. 3.31±0.45, p = 0.045), while the RVEF, RVEDVi, and RVESVi decreased at the second week (p < 0.05). The PCr/ATP ratio displayed a significant correlation with RVEF (r = 0.605, p = 0.001), RVEDVi, and RVESVi (r = -0.661, r = -0.703; p < 0.001).

CONCLUSIONS

31P MRS can easily detect the cardiac energetics alteration in a CHR model before the onset of ventricular dysfunction. The decreased PCr/ATP ratio likely reveales myocardial injury and cardiac dysfunction.

Uncoupling protein 1 knockout aggravates isoproterenol-induced acute myocardial ischemia via AMPK/mTOR/PPARα pathways in rats

Uncoupling protein 1 (UCP1) was found exclusively in the inner membranes of the mitochondria of brown adipose tissue (BAT). We found that UCP1 was also expressed in heart tissue and significantly upregulated in isoproterenol (ISO)-induced acute myocardial ischemia (AMI) rat model. The present study is to determine the underlying mechanism involved in the UCP1 upregulation in ISO-induced AMI rat model. The Ucp1^−/− rats were generated by CRISPR-Cas9 system and presented decreased BAT volume. 2-months old Sprague Dawley (SD) wild-type (WT) and Ucp1^−/− rats were treated with ISO intraperitoneally 30 mg/kg once a day for 3 consecutive days to establish AMI model. In saline group, the echocardiographic parameters, serum markers of myocardial injury cardiac troponin I (cTnI), creatine kinase isoenzyme MB (CK-MB), oxidant malondialdehyde (MDA), antioxidant superoxide dismutase (SOD) or fibrosis were comparable between WT and Ucp1^−/− rats. ISO treatment induced worse left ventricle (LV) hypertrophy, myocardial fibrosis, increased higher cTnI, CK-MB and MDA and decreased lower SOD level in Ucp1^−/− rats compared with that of WT rats. Ucp1^−/− rats also presented lower myocardial phosphocreatine (PCr)/ATP-ratio, which demonstrated worse cardiac energy regulation defect. ISO treatment induced the phosphorylation of AMP-activated protein kinase (AMPK) activation, subsequently the phosphorylation of mammalian target of rapamycin (mTOR) inhibition and peroxisome proliferators-activated receptor α (PPARα) activation in WT rats, whereas activation of AMPK/mTOR/PPARα pathways significantly inhibited in Ucp1^−/− rats. To sum up, UCP1 knockout aggravated ISO-induced AMI by inhibiting AMPK/mTOR/PPARα pathways in rats. Increasing UCP1 expression in heart tissue may be a cytoprotective therapeutic strategy for AMI.

Responses to exercise training in patients with heart failure. Analysis by oxygen transport steps

BACKGROUND

Exercise training (ET) increases exercise tolerance, improves quality of life and likely the prognosis in heart failure patients with reduced ejection fraction (HFrEF). However, some patients do not improve, whereas exercise training response is still poorly understood. Measurement of cardiac output during cardiopulmonary exercise test might allow ET response assessment according to the different steps of oxygen transport.

METHODS

Fifty-three patients with HFrEF (24 with ischemic cardiomyopathy (ICM) and 29 with dilated cardiomyopathy (DCM) had an aerobic ET. Before and after ET program, peak oxygen consumption (VO_2peak) and cardiac output using thoracic impedancemetry were measured. Oxygen convection (QO_2peak) and diffusion (DO₂) were calculated using Fick's principle and Fick's simplified law. Patients were considered as responders if the gain was superior to 10%.

RESULTS

We found 55% VO_2peak responders, 62% QO_2peak responders and 56% DO₂ responders. Four patients did not have any response. None baseline predictive factor for VO_2peak response was found. QO_2peak response was related to exercise stroke volume (r = 0.84), cardiac power (r = 0.83) and systemic vascular resistance (SVR_peak) (r = -0.42) responses. Cardiac power response was higher in patients with ICM than in those with DCM (p < 0.05). Predictors of QO2_peak response were low baseline exercise stroke volume and ICM etiology. Predictors of DO₂ response were higher baseline blood creatinine and prolonged training.

CONCLUSION

The analysis of the response to training in patients with HFrEF according to the different steps of oxygen transport revealed different phenotypes on VO_2peak responses, namely responses in either oxygen convection and/or diffusion.

Myocardial Energetics in Obesity: Enhanced ATP Delivery Through Creatine Kinase With Blunted Stress Response

BACKGROUND

Obesity is strongly associated with exercise intolerance and the development of heart failure. Whereas myocardial energetics and diastolic function are impaired in obesity, systolic function is usually preserved. This suggests that the rate of ATP delivery is maintained, but this has never been explored in human obesity. We hypothesized that ATP transfer rate through creatine kinase (CK) (k_f^CKrest) would be increased, compensating for depleted energy stores (phosphocreatine/ATP), but potentially limiting greater ATP delivery during increased workload. We hypothesized that these changes would normalize with weight loss.

METHODS

We recruited 80 volunteers (35 controls [body mass index 24±3 kg/m²], 45 obese [body mass index 35±5 kg/m²]) without coexisting cardiovascular disease. Participants underwent body composition analysis, magnetic resonance imaging of abdominal, liver, and myocardial fat content, left ventricular function, and ³¹P magnetic resonance spectroscopy to assess phosphocreatine/ATP and CK kinetics, at rest and during dobutamine stress. Obese volunteers were assigned to a dietary weight loss intervention, before reexamination.

RESULTS

At rest, although myocardial phosphocreatine/ATP was 14% lower in obesity (1.9±0.3 versus 2.2±0.2, P<0.001), k_f^Ckrest was 33% higher (0.23±0.07 s^-1 versus 0.16±0.08 s^-1, P=0.002), yielding no difference in overall resting ATP delivery (obese 2.5±0.9 µmol·g^-1·s^-1 versus control 2.2±1.1 µmol·g^-1·s^-1, P=0.232). In controls, increasing cardiac workload led to an increase in both k_f^CK (+86%, P<0.001) and ATP delivery (+80%, P<0.001). However, in obesity, similar stress led to no significant increase in either k_f^CK (P=0.117) or ATP delivery (P=0.608). This was accompanied by reduced systolic augmentation (absolute increase in left ventricular ejection fraction, obese +16±7% versus control +21±4%, P=0.031). Successful weight loss (-11±5% body weight) was associated with improvement of these energetic changes such that there was no significant difference in comparison with controls.

CONCLUSIONS

In the obese resting heart, the myocardial CK reaction rate is increased, maintaining ATP delivery despite reduced phosphocreatine/ATP. During increased workload, although the nonobese heart increases ATP delivery through CK, the obese heart does not; this is associated with reduced systolic augmentation and exercise tolerance. Weight loss reverses these energetic changes. This highlights myocardial energy delivery through CK as a potential therapeutic target to improve symptoms in obesity-related heart disease, and a fascinating modifiable pathway involved in the progression to heart failure, as well.

Physical activity is reduced prior to ventricular arrhythmias in patients with a wearable cardioverter defibrillator

INTRODUCTION

The utility of accelerometer-based activity data to identify patients at risk of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) has not previously been investigated. The aim of the current study was to determine whether physical activity is associated with manifesting spontaneous sustained VT/VF requiring emergent defibrillation in patients with an ejection fraction of ≤35%.

METHODS

Patients consecutively prescribed a wearable cardioverter defibrillator (WCD) from April 2015 to May 2018 were included. Shock data and 4 weeks of physical activity data, beginning with the first week of WCD wear, were analyzed.

RESULTS

Based on the ROC curve outcome generated from 4057 patients, average daily step count during the first week accurately predicted those patients with sustained VT/VF compared to those without (shocked (n = 81) vs nonshocked (n = 3976) area under the curve, c-index = 0.71, 95% CI = 0.65-0.77, P < .001). An average cutoff of 3637 daily steps during week 1 separated the groups. Patients who averaged fewer than 3637 steps per day during the first week of WCD use were 4.3 times more likely to experience a shock than those who walked more than 3637 steps per day (OR = 4.29, 95% CI = 2.58-7.15, P < .001).

DISCUSSION

Average daily step counts are lower in WCD patients who manifest spontaneous VT/VF. Whether these findings represent a causal or correlational relationship, future studies to encourage a minimum daily step count in high-risk patients may impact the incidence of sustained VT/VF.

Effect of exercise training on cardiac metabolism in rats with heart failure

Objectives. Heart failure (HF) impairs resting myocardial energetics, myocardial mitochondrial performance, and maximal oxygen uptake (VO_2max). Exercise training is included in most rehabilitation programs and benefits HF patients. However, the effect of exercise intensity on cardiac mitochondrial respiration and concentrations of the key bioenergetic metabolites phosphocreatine (PCr), adenosine triphosphate (ATP), and inorganic phosphate (Pi) is unclear. This study aimed to investigate the effects of exercise training at different intensities in rats with HF. Methods. Rats underwent myocardial infarction or sham operations and were divided into three subgroups: sedentary, moderate intensity, or high intensity. The impact of HF and 6 weeks of exercise training on energy metabolism was evaluated by ³¹P magnetic resonance spectroscopy and mitochondrial respirometry. The concentrations of PCr, ATP, and Pi were quantified by magnetic resonance spectroscopy. VO_2max was measured by treadmill respirometry. Results. Exercise training increased VO_2max in sham and HF. PCr/ATP ratio was reduced in HF (p < .01) and remained unchanged by exercise training. PCr concentration was significantly lower in HF compared to sham (p < .01). Moderate and high-intensity exercise training increased ATP in HF and sham. HF impaired complex I (CI) and complex II (p = .034) respiration. High-intensity exercise training recovered CI respiration in HF rats compared to HF sedentary (p = .014). Conclusions. Exercise training improved cardiac performance, as indicated by increased VO_2max and higher exercise capacity, without changing the myocardial PCr/ATP ratio. These observations suggest that the PCr/ATP biomarker is not suited to evaluate the beneficial effects of exercise training in the heart. The exact mechanisms require further investigations, as exercise training did increase ATP levels and CI respiration.

The effectiveness of cardiac rehabilitation in non-ischemic dilated cardiomyopathy patients: A pilot study

BACKGROUND/PURPOSE

We aimed to investigate the efficacy of cardiac rehabilitation (CR) through parameters of cardiopulmonary exercise testing (CPET) and echocardiography in non-ischemic dilated cardiomyopathy (DCM) patients.

METHODS

We retrospectively identified non-ischemic DCM patients through medical records (between October 2011 and October 2018) in rehabilitation outpatient-clinics. Patients were divided into rehabilitation and control groups. Patients in the rehabilitation group eligible for inclusion had CR for 3-6 months. Control group patients were without rehabilitation. We recorded CPET and echocardiography parameters at the baseline and follow-up time-points. For safety evaluation, we investigated all adverse effects during training sessions. We utilized Mann-Whitney U test for between- and Wilcoxon signed-rank test for within-group comparisons.

RESULTS

Twenty-five patients (14 in rehabilitation and 11 in control group) were included. In the rehabilitation group, significantly increased peak V˙O₂/kg, peak V˙O₂%, peak workload and peak O₂ pulse were observed after completing CR, and echocardiographic parameters including left ventricular ejection fraction and end-systolic volume. Rehabilitation group patients demonstrated better improvement (change from the baseline) in peak V˙O₂/kg, peak V˙O₂% and peak workload vs. control. No adverse effects during rehabilitation trainings were observed.

CONCLUSION

For non-ischemic DCM, rehabilitation led to superior cardiopulmonary outcomes vs. no rehabilitation, without adverse effects.

Sudden Cardiac Death in Genetic Cardiomyopathies

Sudden cardiac death (SCD) caused by ventricular arrhythmias is common in patients with genetic cardiomyopathies (CMs) including dilated CM, hypertrophic CM, and arrhythmogenic right ventricular CM (ARVC). Phenotypic features can identify individuals at high enough risk to warrant placement of an implantable cardioverter-defibrillator, although risk stratification schemes remain imperfect. Genetic testing is valuable for family cascade screening but with few exceptions (eg, LMNA mutations) do not identify higher risk for SCD. Although randomized trials are lacking, observational data suggest that ICDs can be beneficial. Vigorous exercise can exacerbate ARVC disease progression and increase likelihood of ventricular arrhythmias.

Human Cardiac 31P-MR Spectroscopy at 3 Tesla Cannot Detect Failing Myocardial Energy Homeostasis during Exercise

Phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS) is a unique non-invasive imaging modality for probing in vivo high-energy phosphate metabolism in the human heart. We investigated whether current ³¹P-MRS methodology would allow for clinical applications to detect exercise-induced changes in (patho-)physiological myocardial energy metabolism. Hereto, measurement variability and repeatability of three commonly used localized ³¹P-MRS methods [3D image-selected in vivo spectroscopy (ISIS) and 1D ISIS with 1D chemical shift imaging (CSI) oriented either perpendicular or parallel to the surface coil] to quantify the myocardial phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio in healthy humans (n = 8) at rest were determined on a clinical 3 Tesla MR system. Numerical simulations of myocardial energy homeostasis in response to increased cardiac work rates were performed using a biophysical model of myocardial oxidative metabolism. Hypertrophic cardiomyopathy was modeled by either inefficient sarcomere ATP utilization or decreased mitochondrial ATP synthesis. The effect of creatine depletion on myocardial energy homeostasis was explored for both conditions. The mean in vivo myocardial PCr/ATP ratio measured with 3D ISIS was 1.57 ± 0.17 with a large repeatability coefficient of 40.4%. For 1D CSI in a 1D ISIS-selected slice perpendicular to the surface coil, the PCr/ATP ratio was 2.78 ± 0.50 (repeatability 42.5%). With 1D CSI in a 1D ISIS-selected slice parallel to the surface coil, the PCr/ATP ratio was 1.70 ± 0.56 (repeatability 43.7%). The model predicted a PCr/ATP ratio reduction of only 10% at the maximal cardiac work rate in normal myocardium. Hypertrophic cardiomyopathy led to lower PCr/ATP ratios for high cardiac work rates, which was exacerbated by creatine depletion. Simulations illustrated that when conducting cardiac ³¹P-MRS exercise stress testing with large measurement error margins, results obtained under pathophysiologic conditions may still lie well within the 95% confidence interval of normal myocardial PCr/ATP dynamics. Current measurement precision of localized ³¹P-MRS for quantification of the myocardial PCr/ATP ratio precludes the detection of the changes predicted by computational modeling. This hampers clinical employment of ³¹P-MRS for diagnostic testing and risk stratification, and warrants developments in cardiac ³¹P-MRS exercise stress testing methodology.

Voluntary Exercise Improves Cardiac Function and Prevents Cardiac Remodeling in a Mouse Model of Dilated Cardiomyopathy

Objective: Despite the indubitable beneficial effect of exercise to prevent of cardiovascular diseases, there is still a lack of studies investigating the impact of exercise in non-ischemic dilated cardiomyopathy. Here, we investigated the impact of voluntary exercise on cardiac function in a mouse model of non-ischemic dilated cardiomyopathy (αMHC-MerCreMer:Sf/Sf), induced by cardiac-specific inactivation of the Serum Response Factor.

Materials and Methods: Seven days after tamoxifen injection, 20 αMHC-MerCreMer:Sf/Sf mice were assigned to sedentary (n = 8) and exercise (n = 12) groups. Seven additional αMHC-MerCreMer:Sf/Sf mice without tamoxifen injection were used as control. The exercise group performed 4 weeks of voluntary running on wheel (1.8 ± 0.12 km/day). Cardiac function, myocardial fibrosis, and mitochondrial energetic pathways were then blindly assessed.

Results: Exercised mice exhibited a smaller decrease of left ventricular (LV) fractional shortening and ejection fraction compared to control mice. This was associated with a lower degree of LV remodeling in exercised mice, as shown by a lower LV end-systolic intrerventricular septal and posterior wall thickness decrease from baseline values compared to sedentary mice. Moreover, exercised mice displayed a reduced gene expression of atrial and brain natriuretic factors. These benefits were associated by a reduced level of myocardial fibrosis. In addition, exercised mice exhibited a higher mitochondrial aconitase, voltage-dependent anion-selective channel 1 and PPAR gamma coactivators-1 alpha proteins levels suggesting that the increase of mitochondrial biogenesis and/or metabolism slowed the progression of dilated cardiomyopathy in exercised animals.

Conclusions: In conclusion, our results support the role of voluntary exercise to improve outcomes in non-ischemic dilated heart failure (HF) and also support its potential for a routine clinical use in the future.

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.

Cardiac Rehabilitation Exercise Training for High-Risk Cardiac Patients

Objective

To examine the effect and safety of cardiac rehabilitation (CR) program in high-risk cardiac patients and compare these results to those of control CR participants without high-risk criteria.

Methods

A total of 12 high-risk cardiac patients were recruited as subjects. The high-risk criteria were: advanced heart failure with left ventricular ejection fraction (LVEF) of less than 30%, a recent history of cardiac arrest or dangerous arrhythmia, and cardiac device insertion. Another 12 CR participants without any high-risk criteria mentioned above were recruited as controls. Both groups underwent 6 to 8 weeks of CR exercise training. Exercise tolerance tests were performed before and after completion of the CR program. After CR completion, both groups were evaluated and their results were compared.

Results

After completion of the CR exercise program, both groups showed significant increases in peak oxygen uptake (VO_2peak) and LVEF. In the control group (n=12), VO_2peak increased from 25.9 to 31.8 mL/kg/min (changing rate, +21.4%±22.1%) and LVEF increased from 56.1% to 59.1% (changing rate, +5.3%±8.4%). In the high-risk group (n=12), VO_2peak increased from 16.8 to 21.0 mL/kg/min (changing rate, +28.6%±21.4%) and LVEF increased from 26.1% to 29.4% (changing rate, +16.1%±12.9%). There was no serious cardiovascular event during all exercise hours.

Conclusion

High-risk cardiac patients who completed a supervised CR program demonstrated significant improvements in VO_2peak and LVEF without any serious cardiovascular event. The improvement rate was similar to that of control group.

Energy Deregulation Precedes Alteration in Heart Energy Balance in Young Spontaneously Hypertensive Rats: A Non Invasive In Vivo31P-MR Spectroscopy Follow-Up Study

Introduction

Gradual alterations in cardiac energy balance, as assessed by the myocardial PCr/ATP-ratio, are frequently associated with the development of cardiac disease. Despite great interest for the follow-up of myocardial PCr and ATP content, cardiac MR-spectroscopy in rat models in vivo is challenged by sensitivity issues and cross-contamination from other organs.

Methods

Here we combined MR-Imaging and MR-Spectroscopy (Bruker BioSpec 9.4T) to follow-up for the first time in vivo the cardiac energy balance in the SHR, a genetic rat model of cardiac hypertrophy known to develop early disturbances in cytosolic calcium dynamics.

Results

We obtained consistent ³¹P-spectra with high signal/noise ratio from the left ventricle in vivo by using a double-tuned (³¹P/¹H) surface coil. Reasonable acquisition time (<3.2min) allowed assessing the PCr/ATP-ratio comparatively in SHR and age-matched control rats (WKY): i) weekly from 12 to 21 weeks of age; ii) in response to a bolus injection of the ß-adrenoreceptor agonist isoproterenol at age 21 weeks.

Discussion

Along weeks, the cardiac PCr/ATP-ratio was highly reproducible, steady and similar (2.35±0.06) in SHR and WKY, in spite of detectable ventricular hypertrophy in SHR.

At the age 21 weeks, PCr/ATP dropped more markedly (-17.1%±0.8% vs. -3,5%±1.4%, P<0.001) after isoproterenol injection in SHR and recovered slowly thereafter (time constant 21.2min vs. 6.6min, P<0.05) despite similar profiles of tachycardia among rats.

Conclusion

The exacerbated PCr/ATP drop under ß-adrenergic stimulation indicates a defect in cardiac energy regulation possibly due to calcium-mediated abnormalities in the SHR heart. Of note, defects in energy regulation were present before detectable abnormalities in cardiac energy balance at rest.

Mitochondrial Function and Diabetes: Consequences for Skeletal and Cardiac Muscle Metabolism

SIGNIFICANCE

An early hallmark in the development of type 2 diabetes is the resistance to the effect of insulin in skeletal muscle and in the heart. Since mitochondrial function was found to be diminished in patients with type 2 diabetes, it was suggested that this defect might be involved in the etiology of insulin resistance. Although several hypotheses were suggested, yet unclear is the mechanistic link between these two phenomena.

RECENT ADVANCES

Herein, we review the evidence for disturbances in mitochondrial function in skeletal muscle and the heart in the diabetic state. Also the mechanisms involved in improving mitochondrial function are considered and, whenever possible, human data is cited.

CRITICAL ISSUES

Reported evidence shows that interventions that improve skeletal muscle mitochondrial function also improve insulin sensitivity in humans. In the heart, available data from animal studies suggests that enhancement of mitochondrial function can reverse aging-induced changes in heart function, and can be protective against cardiomyopathy and heart failure.

FUTURE DIRECTIONS

Mitochondria and their functions can be targeted with the aim of improving skeletal muscle insulin sensitivity and cardiac function. However, human clinical intervention studies are needed to fully substantiate the potential of mitochondria as a target to prevent cardiometabolic disease.

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.

Targets for therapy in sarcomeric cardiomyopathies

To date, no compounds or interventions exist that treat or prevent sarcomeric cardiomyopathies. Established therapies currently improve the outcome, but novel therapies may be able to more fundamentally affect the disease process and course. Investigations of the pathomechanisms are generating molecular insights that can be useful for the design of novel specific drugs suitable for clinical use. As perturbations in the heart are stage-specific, proper timing of drug treatment is essential to prevent initiation and progression of cardiac disease in mutation carrier individuals. In this review, we emphasize potential novel therapies which may prevent, delay, or even reverse hypertrophic cardiomyopathy caused by sarcomeric gene mutations. These include corrections of genetic defects, altered sarcomere function, perturbations in intracellular ion homeostasis, and impaired myocardial energetics.

Cardiac rehabilitation of a patient with an advanced dilated cardiomyopathy: a case report

The dilated cardiomyopathy is the common type of cardiomyopathy, and its distinctive characteristic is the systolic dysfunction. Not many reports were issued about the efficacy of cardiac rehabilitation in patients with an advanced dilated cardiomyopathy until yet. A 50-year-old man who was diagnosed with dilated cardiomyopathy with congestive heart failure was admitted to the emergency room after a sudden collapse and a ventricular fibrillation was presented in the actual electrocardiogram. After three months, the patient participated in an 8-week cardiac rehabilitation program with electrocardiogram monitoring for 50 minutes per session at five times per week. The maximal oxygen consumption improved from 13.5 to 19.4 mL/kg/min during this time. At 3.9 metabolic equivalents, the myocardial oxygen demand decreased from 21,710 to 12,669 mmHg.bpm and the Borg's scale of perceived exertion decreased from 15 to 9. The left ventricular ejection fraction improved from 14% to 19%. So in this case report will be presented a patient after a successful cardiac rehabilitation program. Before this the patient suffered from a much more advanced dilated cardiomyopathy and was resuscitated from cardiac arrest.

Almanac 2014: cardiomyopathies

Cardiomyopathies are myocardial disorders that are not explained by abnormal loading conditions and coronary artery disease. They are classified into a number of morphological and functional phenotypes that can be caused by genetic and non-genetic mechanisms. The dominant themes in papers published in 2012-2013 are similar to those reported in Almanac 2011, namely, the use (and interpretation) of genetic testing, development and application of novel non-invasive imaging techniques and use of serum biomarkers for diagnosis and prognosis. An important innovation since the last Almanac is the development of more sophisticated models for predicting adverse clinical events.

Exercise: friend or foe?

Physical activity and exercise have been associated with reduced cardiovascular risk, morbidity, and mortality, as well as all-cause mortality, both in the general population and in patients with various forms of cardiovascular disease. Increasing amounts of exercise are associated with incremental reductions in mortality, but considerable benefits have been found even with a low level of exercise. Exercise is beneficial for most individuals, but risks exist. Exercise is associated with reduced long-term morbidity and mortality, but acute exercise can transiently increase the risk of fatal or nonfatal cardiovascular events. Although tragic, these events are very rare, and even to some extent preventable with screening programmes. Low-intensity physical activity is important and beneficial to all individuals, including those with a high risk of adverse cardiovascular events. In individuals who are physically fit and who do not have genetic predisposition to, or signs of, cardiovascular disease, the greater the intensity and amount of exercise, the greater the health benefits. Nevertheless, effective strategies to encourage exercise in the population are lacking. A sustained increase in physical activity is likely to require more than individual advice, and needs to include urban planning and possibly even legislation.