Adaptive Reductions in Left Ventricular Diastolic Compliance Protect the Heart From Stretch-Induced Stunning

Porcine Model of Hypertrophy-Independent Left Ventricular Stiffening via Repetitive Pressure Overload

Diastolic dysfunction arising from alterations in myocardial structure and/or function is a central component of several cardiovascular disorders, including heart failure with preserved ejection fraction (HFpEF). Basic research aimed at understanding underlying mechanisms contributing to the development of diastolic dysfunction has generally centered upon models of left ventricular (LV) hypertrophy arising from persistent and severe elevations in myocardial afterload (e.g., aortic banding). Mechanisms of hypertrophy-independent diastolic dysfunction, on the other hand, have received less attention, even though overt anatomic LV hypertrophy is absent in many HFpEF patients. Here, we describe the development of a novel porcine model of repetitive pressure overload (RPO) in which chronic, intermittent exposure to transient episodes of hypertension produces an increase in LV stiffness, interstitial fibrosis, cardiomyocyte hypertrophy, and capillary rarefaction without significant changes in LV mass. This model offers important insight into how diastolic dysfunction and HFpEF may develop in the absence of comorbidities, sustained hypertension, or LV hypertrophy, while also providing a useful translational research tool for investigation of novel therapeutic approaches to restore myocardial compliance and improve diastolic function.

Combination of cardiac color Doppler ultrasound, serum MR-ProANP and NT-ProBNP forecasted hypertensive LVH and LFH

To analyze the value of the combined test of the cardiac color Doppler ultrasound, the serum middle receptor pro-atrial natriuretic peptide (MR-ProANP) and the N-terminal pro-brain natriuretic peptide (NT-ProBNP) in forecasting the hypertensive left ventricular hypertrophy (LVH) and left heart failure (LHF). All patients were subjected to cardiac color Doppler ultrasound examination to obtain left atrium volume index (LAVI), left ventricular end-diastolic diameter (LVEDD), early-diastolic peak flow velocity (E), early-diastolic mean flow velocity (e'), early-diastolic peak flow velocity/early-diastolic mean flow velocity (E/e') and left ventricular ejection fraction (LVEF). Biomarkers were performed to obtain serum MR-ProANP and NT-ProBNP concentrations, and statistical analysis was performed. The LVEF was obviously lower than that in the control group (P<0.01). The area under the receiver operating characteristic (ROC) curve (AUC) values of LVEF, E/e', serum MR-ProANP and NT-ProBNP alone were in the range of 0.7-0.8. The AUC, sensitivity and specificity of LVEF and E/e' combined with MR-ProANP and NT-ProBNP to diagnose hypertensive LVH and LHF were 0.892, 89.14% and 78.21%, which were higher than those of single diagnosis. In the heart failure group, LVEF was negatively correlated with serum MR-ProANP and NT-ProBNP concentrations (P<0.05), and E/e' was positively correlated with serum MR-ProANP and NT-ProBNP concentrations (P<0.05). Pump function and ventricular remodeling in patients with hypertensive LVH and LHF are closely related to serum MR-ProANP and NT-ProBNP levels. Combination of the two testing can improve the prediction and diagnostic efficacy of LHF.

Could Repeated Cardio-Renal Injury Trigger Late Cardiovascular Sequelae in Extreme Endurance Athletes?

Regular exercise confers multifaceted and well-established health benefits. Yet, transient and asymptomatic increases in markers of cardio-renal injury are commonly observed in ultra-endurance athletes during and after competition. This has raised concerns that chronic recurring insults could cause long-term cardiac and/or renal damage. Indeed, extreme endurance exercise (EEE) over decades has sometimes been linked with untoward cardiac effects, but a causal relation with acute injury markers has not yet been established. Here, we summarize the current knowledge on markers of cardiac and/or renal injury in EEE athletes, outline the possible interplay between cardiac and kidney damage, and explore the roles of various factors in the development of potential exercise-related cardiac damage, including underlying diseases, medication, sex, training, competition, regeneration, mitochondrial dysfunction, oxidative stress, and inflammation. In conclusion, despite the undisputed health benefits of regular exercise, we speculate, based on the intimate link between heart and kidney diseases, that in rare cases excessive endurance sport may induce adverse cardio-renal interactions that under specific, hitherto undefined conditions could result in persistent cardiac damage. We highlight future research priorities and provide decision support for athletes and clinical consultants who are seeking safe strategies for participation in EEE training and competition.

Myocardial Injury, Troponin Release and Cardiomyocyte Death in Brief Ischemia, Failure and Ventricular Remodeling

Troponin released from irreversibly injured myocytes is the gold standard biomarker for the rapid identification of an acute coronary syndrome. In acute myocardial infarction, necrotic cell death is characterized by sarcolemmal disruption in response to a critical level of energy depletion after more than 15-minutes of ischemia. While troponin I and T are highly specific for cardiomyocyte death, high-sensitivity assays have demonstrated that measurable circulating levels of troponin are present in the majority of normal subjects. In addition, transient as well as chronic elevations have been demonstrated in many disease states not clearly associated with myocardial ischemia. The latter observations have given rise to the clinical concept of myocardial injury. This review will summarize evidence supporting the notion that circulating troponin levels parallel the extent of myocyte apoptosis in normal ventricular remodeling and in pathophysiological conditions not associated with infarction or necrosis. It will review the evidence that myocyte apoptosis can be accelerated by both diastolic strain from elevated ventricular preload as well as systolic strain from dyskinesis after brief episodes of ischemia too short to cause a critical level of myocyte energy depletion. We then show how chronic, low rates of myocyte apoptosis from endogenous myocyte turnover, repetitive ischemia or repetitive elevations in LV diastolic pressure can lead to significant myocyte loss in the absence of neurohormonal stimulation. Finally, we posit that the differential response to strain-induced injury in heart failure may determine whether progressive myocyte loss and HFrEF or interstitial fibrosis and HFpEF become the heart failure phenotype.

Hemodynamic profiles by non-invasive monitoring of cardiac index and vascular tone in acute heart failure patients in the emergency department: External validation and clinical outcomes

Background

Non-invasive finger-cuff monitors measuring cardiac index and vascular tone (SVRI) classify emergency department (ED) patients with acute heart failure (AHF) into three otherwise-indistinguishable subgroups. Our goals were to validate these “hemodynamic profiles” in an external cohort and assess their association with clinical outcomes.

Methods

AHF patients (n = 257) from five EDs were prospectively enrolled in the validation cohort (VC). Cardiac index and SVRI were measured with a ClearSight finger-cuff monitor (formerly NexFin, Edwards Lifesciences) as in a previous study (derivation cohort, DC, n = 127). A control cohort (CC, n = 127) of ED patients with sepsis was drawn from the same study as the DC. K-means cluster analysis previously derived two-dimensional (cardiac index and SVRI) hemodynamic profiles in the DC and CC (k = 3 profiles each). The VC was subgrouped de novo into three analogous profiles by unsupervised K-means consensus clustering. PERMANOVA tested whether VC profiles 1–3 differed from profiles 1–3 in the DC and CC, by multivariate group composition of cardiac index and vascular tone.

Profiles in the VC were compared by a primary outcome of 90-day mortality and a 30-day ranked composite secondary outcome (death, mechanical cardiac support, intubation, new/emergent dialysis, coronary intervention/surgery) as time-to-event (survival analysis) and binary events (odds ratio, OR). Descriptive statistics were used to compare profiles by two validated risk scores for the primary outcome, and one validated score for the secondary outcome.

Results

The VC had median age 60 years (interquartile range {49–67}), and was 45% (n = 116) female. Multivariate profile composition by cardiac index and vascular tone differed significantly between VC profiles 1–3 and CC profiles 1–3 (p = 0.001, R² = 0.159). A difference was not detected between profiles in the VC vs. the DC (p = 0.59, R² = 0.016).

VC profile 3 had worse 90-day survival than profiles 1 or 2 (HR = 4.8, 95%CI 1.4–17.1). The ranked secondary outcome was more likely in profile 1 (OR = 10.0, 1.2–81.2) and profile 3 (12.8, 1.7–97.9) compared to profile 2. Diabetes prevalence and blood urea nitrogen were lower in the high-risk profile 3 (p<0.05). No significant differences between profiles were observed for other clinical variables or the 3 clinical risk scores.

Conclusions

Hemodynamic profiles in ED patients with AHF, by non-invasive finger-cuff monitoring of cardiac index and vascular tone, were replicated de novo in an external cohort. Profiles showed significantly different risks of clinically-important adverse patient outcomes.

Incremental value of left atrial booster and reservoir strain in predicting atrial fibrillation in patients with hypertrophic cardiomyopathy: a cardiovascular magnetic resonance study

BACKGROUND

Left atrial (LA) size and function are known predictors of new onset atrial fibrillation (AF) in hypertrophic cardiomyopathy (HCM) patients. Components of LA deformation including reservoir, conduit, and booster function provide additional information on atrial mechanics. Whether or not LA deformation can augment our ability to predict the risk of new onset AF in HCM patients beyond standard measurements is unknown.

METHODS

We assessed LA size, function, and deformation on cardiovascular magnetic resonance (CMR) in 238 genotyped HCM patients and compared this with twenty age, sex, blood pressure and body mass index matched control subjects. We further evaluated the determinants of new onset AF in HCM patients.

RESULTS

Compared to control subjects, HCM patients had higher LA antero-posterior diameter, lower LA ejection fraction and lower LA reservoir (19.9 [17.1, 22.2], 21.6 [19.9, 22.9], P = 0.047) and conduit strain (10.6 ± 4.4, 13.7 ± 3.3, P = 0.002). LA booster strain did not differ between healthy controls and HCM patients, but HCM patients who developed new onset AF (n = 33) had lower booster strain (7.6 ± 3.3, 9.5 ± 3.0, P = 0.001) than those that did not (n = 205). In separate multivariate models, age, LA ejection fraction, and LA booster and reservoir strain were each independent determinants of AF. Age ≥ 55 years was the strongest determinant (HR 6.62, 95% CI 2.79-15.70), followed by LA booster strain ≤ 8% (HR 3.69, 95% CI 1.81-7.52) and LA reservoir strain ≤ 18% (HR 2.56, 95% CI 1.24-5.27). Conventional markers of HCM phenotypic severity, age and sudden death risk factors were associated with LA strain components.

CONCLUSIONS

LA strain components are impaired in HCM and, together with age, independently predicted the risk of new onset AF. Increasing age and phenotypic severity were associated with LA strain abnormalities. Our findings suggest that the routine assessment of LA strain components and consideration of age could augment LA size in predicting risk of AF, and potentially guide prophylactic anticoagulation use in HCM.

Influence of right ventricular pressure and volume overload on right and left ventricular diastolic function

BACKGROUND

Ventricular interdependence may account for altered ventricular mechanics in congenital heart disease. The present study aimed to identify differences in load-dependent right ventricular (RV)-left ventricular (LV) interactions in porcine models of pulmonary stenosis (PS) and pulmonary insufficiency (PI) by invasive admittance-derived hemodynamics in conjunction with noninvasive cardiovascular magnetic resonance (CMR).

METHODS

Seventeen pigs were used in the study (7 with PS, 7 with PI, and 3 controls). Progressive PS was created by tightening a Teflon tape around the pulmonary artery, and PI was created by excising 2 leaflets of the pulmonary valve. Admittance catheterization data were obtained for the RV and LV at 10 to 12 weeks after model creation, with the animal ventilated under temporary diaphragm paralysis. CMR was performed in all animals immediately prior to pressure-volume catheterization.

RESULTS

In the PS group, RV contractility was increased, manifested by increased end-systolic elastance (mean difference, 1.29 mm Hg/mL; 95% confidence interval [CI], 0.57-2.00 mm Hg/mL). However, in the PI group, no significant changes were observed in RV systolic function despite significant changes in RV diastolic function. In the PS group, LV end-systolic volume was significantly lower compared with controls (mean difference, 25.1 mL; 95% CI, -40.5 to -90.7 mL), whereas in the PI group, the LV showed diastolic dysfunction, demonstrated by an elevated isovolumic relaxation constant and ventricular stiffness (mean difference, 0.03 mL^-1; 95% CI, -0.02 to 0.09 mL^-1).

CONCLUSIONS

The LV exhibits systolic dysfunction and noncompliance with PI. PS is associated with preserved LV systolic function and evidence of some LV diastolic dysfunction. Interventricular interactions influence LV filling and likely account for differential effects of RV pressure and volume overload on LV function.

Clinical Phenogroups in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for more than one-half of patients with heart failure. Effective treatment of HFpEF has not been established, largely because of the complexities and heterogeneity in the phenotypes of HFpEF. Categorizing patients based on clinical and pathophysiologic phenotype may provide more targeted and efficacious therapies. Despite this clinical need, there is no consensus on how to categorize patients with HFpEF into phenogroups. Possible metrics include the presence or absence of specific comorbidities that influence pathophysiology, imaging, hemodynamics, or other biomarkers. This article describes currently recognized phenotypes of HFpEF and potential treatment strategies.

Blood Pressure Reduction in Hypertensive Acute Heart Failure

PURPOSE OF REVIEW

To review the key clinical and research questions regarding blood pressure (BP) reduction with vasodilators in the early management of hypertensive acute heart failure (H-AHF).

RECENT FINDINGS

Despite numerous AHF vasodilator clinical trials in the past two decades, virtually none has studied a population where vasoconstriction is the predominant physiology, and with the agents and doses most commonly used in contemporary practice. AHF patients are remarkably heterogenous by vascular tone, and this heterogeneity is not always discernible through BP or clinical exam. Emerging data suggest that diastolic BP may be a stronger correlate of vascular tone in AHF than systolic BP, despite the latter historically serving as a key inclusion criterion for vasodilator clinical trials. Existing data are limited. A clinical trial that evaluates vasodilators in a manner of use consistent with contemporary practice, specifically within the subpopulation of patients with true H-AHF, is greatly needed. Until then, observational data supports long-standing vasodilators such as nitroglycerin, administered by IV bolus, and with goal reduction of SBP ≤25% as a safe first-line approach for patients with severe H-AHF presentations.

Novel Göttingen Miniswine Model of Heart Failure With Preserved Ejection Fraction Integrating Multiple Comorbidities

A lack of preclinical large animal models of heart failure with preserved ejection fraction (HFpEF) that recapitulate this comorbid-laden syndrome has led to the inability to tease out mechanistic insights and to test novel therapeutic strategies. This study developed a large animal model that integrated multiple comorbid determinants of HFpEF in a miniswine breed that exhibited sensitivity to obesity, metabolic syndrome, and vascular disease with overt clinical signs of heart failure. The combination of a Western diet and 11-deoxycorticosterone acetate salt-induced hypertension in the Göttingen miniswine led to the development of a novel large animal model of HFpEF that exhibited multiorgan involvement and a full spectrum of comorbidities associated with human HFpEF.