Determinants of ventricular function in pressure-overload hypertrophy in man

Cardiac computed tomography-derived coronary artery volume to myocardial mass in patients with severe coronary artery disease

BACKGROUND

Coronary artery lumen volume (V) to myocardial mass (M) ratio (V/M) can show the mismatch between epicardial coronary arteries and the underlying myocardium.

METHODS

The V, M and V/M were obtained from the coronary computed tomography angiography (CCTA) of patients in the FAST-TRACK CABG study, the first-in-human trial of coronary artery bypass grafting (CABG) guided solely by CCTA and fractional flow reserve derived from CCTA (FFRCT) in patients with complex coronary artery disease (CAD). The correlations between V/M ratios and baseline characteristics were determined and compared with those from the ADVANCE registry, an unselected cohort of historical controls with chronic CAD.

RESULTS

The V/M ratio was obtained in 106 of the 114 pre-CABG CCTAs. Mean age was 65.6 years and 87% of them were male. The anatomical SYNTAX score from CCTA was significantly higher than the functional SYNTAX score derived using FFRCT [43.1 (15.2) vs 41.1 (16.5), p ​< ​0.001]. Mean V, M, and V/M were 2204 ​mm3, 137 ​g, and 16.5 ​mm3/g, respectively. There were weak negative correlations between V and anatomical and functional SYNTAX scores (Pearson's r ​= ​-0.26 and -0.34). V and V/M had a strong correlation (r ​= ​0.82). The V/M ratio in the current study was significantly lower than that in the ADVANCE registry (median 16.1 vs. 24.8 [1st quartile 20.1]).

CONCLUSION

Systematically smaller V/M ratios were found in this population with severe CAD requiring CABG compared to an unselected cohort with chronic CAD. The V/M ratio could provide additional non-invasive assessment of CAD especially when combined with FFRCT.

Prognostic value of extraaortic-valvular cardiac damage in patients with moderate aortic stenosis and reduced left ventricular ejection fraction

PURPOSE

The extraaortic-valvular cardiac damage (EVCD) Stage has shown potential for risk stratification for patients with aortic stenosis (AS). This study aimed to examine the usefulness of the EVCD Stage in risk stratification of patients with moderate AS and reduced left ventricular ejection fraction (LVEF).

METHODS

Clinical data from patients with moderate AS (aortic valve area, .60-.85 cm2/m2; peak aortic valve velocity, 2.0-4.0 m/s) and reduced LVEF (LVEF 20%-50%) were analyzed during 2010-2019. Patients were categorized into three groups: EVCD Stages 1 (LV damage), 2 (left atrium and/or mitral valve damage), and 3/4 (pulmonary artery vasculature and/or tricuspid valve damage or right ventricular damage). The primary endpoint included a composite of cardiac death and heart failure hospitalization, with non-cardiac death as a competing risk.

RESULTS

The study included 130 patients (mean age 76.4 ± 6.8 years; 62.3% men). They were categorized into three groups: 26 (20.0%) in EVCD Stage 1, 66 (50.8%) in Stage 2, and 48 (29.2%) in Stage 3/4. The endpoint occurred in 54 (41.5%) patients during a median follow-up of 3.2 years (interquartile range, 1.4-5.1). Multivariate analysis indicated EVCD Stage 3/4 was significantly associated with the endpoint (hazard ratio 2.784; 95% confidence interval 1.197-6.476; P = .017) compared to Stage 1, while Stage 2 did not (hazard ratio 1.340; 95% confidence interval .577-3.115; P = .500).

CONCLUSION

The EVCD staging system may aid in the risk stratification of patients with moderate AS and reduced LVEF.

Tracking single hiPSC-derived cardiomyocyte contractile function using CONTRAX an efficient pipeline for traction force measurement

Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) are powerful in vitro models to study the mechanisms underlying cardiomyopathies and cardiotoxicity. Quantification of the contractile function in single hiPSC-CMs at high-throughput and over time is essential to disentangle how cellular mechanisms affect heart function. Here, we present CONTRAX, an open-access, versatile, and streamlined pipeline for quantitative tracking of the contractile dynamics of single hiPSC-CMs over time. Three software modules enable: parameter-based identification of single hiPSC-CMs; automated video acquisition of >200 cells/hour; and contractility measurements via traction force microscopy. We analyze >4,500 hiPSC-CMs over time in the same cells under orthogonal conditions of culture media and substrate stiffnesses; +/- drug treatment; +/- cardiac mutations. Using undirected clustering, we reveal converging maturation patterns, quantifiable drug response to Mavacamten and significant deficiencies in hiPSC-CMs with disease mutations. CONTRAX empowers researchers with a potent quantitative approach to develop cardiac therapies.

Pressure overload-induced systolic heart failure is associated with characteristic myocardial microRNA expression signature and post-transcriptional gene regulation in male rats

Although systolic function characteristically shows gradual impairment in pressure overload (PO)-evoked left ventricular (LV) hypertrophy (LVH), rapid progression to congestive heart failure (HF) occurs in distinct cases. The molecular mechanisms for the differences in maladaptation are unknown. Here, we examined microRNA (miRNA) expression and miRNA-driven posttranscriptional gene regulation in the two forms of PO-induced LVH (with/without systolic HF). PO was induced by aortic banding (AB) in male Sprague-Dawley rats. Sham-operated animals were controls. The majority of AB animals demonstrated concentric LVH and slightly decreased systolic function (termed as ABLVH). In contrast, in some AB rats severely reduced ejection fraction, LV dilatation and increased lung weight-to-tibial length ratio was noted (referred to as ABHF). Global LV miRNA sequencing revealed fifty differentially regulated miRNAs in ABHF compared to ABLVH. Network theoretical miRNA-target analysis predicted more than three thousand genes with miRNA-driven dysregulation between the two groups. Seventeen genes with high node strength value were selected for target validation, of which five (Fmr1, Zfpm2, Wasl, Ets1, Atg16l1) showed decreased mRNA expression in ABHF by PCR. PO-evoked systolic HF is associated with unique miRNA alterations, which negatively regulate the mRNA expression of Fmr1, Zfmp2, Wasl, Ets1 and Atg16l1.

Acute Decompensated Aortic Stenosis: State of the Art Review

Aortic stenosis (AS) is a progressive disease that carries a poor prognosis. Patients are managed conservatively until satisfying an indication for transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR) based on AS severity and the presence of symptoms or adverse impact on the myocardium. Up to 1 in 3 TAVIs are performed for patients with acute symptoms of dyspnoea at rest, angina, and/or syncope - termed acute decompensated aortic stenosis (ADAS) and require urgent aortic valve replacement. These patients have longer hospital length of stay, undergo physical deconditioning, have a higher rate of acute kidney injury and mortality compared to stable patients with less severe symptoms. There is an urgent need to prevent ADAS and to deliver pathways to manage and improve ADAS-related outcomes. We provide here a contemporary review on epidemiological and pathophysiological aspects of ADAS, with a focus on the impact of ADAS from clinical and economic perspectives. We will offer also a global overview of the available evidence for treatment of ADAS and with priorities suggested for addressing current gaps in the literature and unmet clinical needs to improve outcomes for AS patients.

In situ diagnosis and simultaneous treatment of cardiac diseases using a single-device platform

The in situ diagnosis of cardiac activities with simultaneous therapeutic electrical stimulation of the heart is key to preventing cardiac arrhythmia. Here, we present an unconventional single-device platform that enables in situ monitoring even in a wet condition and control of beating heart motions without interferences to the recording signal. This platform consists of the active-matrix array of pressure-sensitive transistors for detecting cardiac beatings, biocompatible, low-impedance electrodes for cardiac stimulations, and an alginate-based hydrogel adhesive for attaching this platform conformally to the epicardium. In contrast to conventional electrophysiological sensing using electrodes, the pressure-sensitive transistors measured mechanophysiological characteristics by monitoring the spatiotemporal distributions of cardiac pressures during heart beating motions. In vivo tests show mechanophysiological readings having good correlation with electrocardiography and negligible interference with the electrical artifacts caused during cardiac stimulations. This platform can therapeutically synchronize the rhythm of abnormal heartbeats through efficient pacing of cardiac arrhythmia.

Usefulness of velocity ratio in patients with moderate aortic stenosis and reduced left ventricular ejection fraction

Background. Moderate aortic stenosis (AS) increases left ventricular afterload and results in unfavorable outcomes in patients with reduced left ventricular ejection fraction (LVEF). Velocity ratio (VR) may be appropriate for the evaluation of aortic valve (AV) hemodynamics because of the low dependence on flow. Therefore, this study investigated the usefulness of VR on the clinical outcomes of such patients. Method. Clinical data of patients with moderate AS (AV area, 0.60-0.85 cm²/m²; peak AV velocity, 2.0-4.0 m/s) and reduced LVEF (LVEF 20-50%) were analyzed during 2010-2018. VR was calculated as peak left ventricular outflow tract velocity/peak AV velocity. The primary endpoint included all-cause death, heart failure hospitalization, and AV replacement. Results. In total, 104 patients (mean age, 75.9 ± 7.0 years; 62.5% men) were included. LVEF was 39.5% ± 7.8%. The AV area was 0.72 ± 0.08 cm²/m², peak AV velocity was 2.59 ± 0.40 m/s, and VR was 0.30 ± 0.07. The follow-up period was 1.7 (0.5-3.5) years. Kaplan-Meier estimates for the endpoint were 59.9% at 3 years. Multivariable analysis revealed that VR (hazard ratio, 0.947; 95% confidence interval, 0.905-0.990; p = .018) was significantly related to this endpoint. Patients with a VR <0.25 had significantly higher incidence rates of the endpoint than those with a VR ≥0.25 (85.6% versus 47.8% at 3 years; p < .001). Conclusions. Patients with moderate AS and reduced LVEF have unfavorable clinical outcomes, particularly those with low VR.

Prevalence of Left Ventricular Hypertrophy Caused by Systemic Hypertension Preceding the Development of Severe Aortic Stenosis

It is generally assumed that left ventricular (LV) hypertrophy in aortic stenosis (AS) is a compensatory adaptation to chronic outflow obstruction. The advent of transcutaneous aortic valve replacement has stimulated more focus on AS in older patients, most of whom have antecedent hypertension. Accordingly, our aim was to investigate the interaction between hypertension and AS on LV remodeling in contemporary practice. We studied consecutive patients referred for echocardiograms with initial aortic valve (AV) peak velocity <3.0 m/s and a peak velocity of >3.5 m/s on a subsequent study performed at least 5 years later. LV size and geometry were measured echocardiographically. Midwall fractional shortening (FSmw) and peak systolic stress were calculated from 2-dimensional echocardiographic and Doppler data. Of 80 patients with progressive AS, 59% were women with mean age 82 ± 9 years. The average interval between the 2 echocardiograms was 5.9 ± 1.8 years. During the study period, peak velocity increased from 2.5 ± 0.4 to 4.2 ± 0.6 m/s (p < 0.01) and LV mass indexed to body surface area increased from 80 ± 28 to 122 ± 51 g/m² (p < 0.01) with a corresponding shift from normal or concentric LV remodeling geometry to concentric hypertrophy. There was no correlation between change in LV mass index and AV mean gradient or valvulo-arterial impedance. However, change in LV mass index did correlate positively with initial peak velocity and inversely with initial LV mass. Plots of FSmw against circumferential stress at baseline and follow-up suggest that systolic function more than compensates for increasing load in many patients. In conclusion, most patients seen in our practice with severe AS have antecedent hypertension and LV remodeling at a time when outflow obstruction is mild. LV remodeling worsens in parallel with worsening severity of AS. Remodeling in these patients features increasing concentric remodeling of the LV, rather than LV dilation. Systolic function, as assessed by FSmw, remains compensated, or even improves relative to afterload, during progression of AS. Given these findings, we speculate that regression of LV hypertrophy to normal will not be affected by transcutaneous aortic valve replacement because LV hypertrophy preceded hemodynamically severe AS.

Effect of Transaortic Valve Intervention for Aortic Stenosis on Myocardial Mechanics

Chronic afterload excess in aortic stenosis results in compensatory concentric hypertrophy which mitigates the increased systolic load. Surgical aortic valve replacement has been shown to decrease afterload and improve left ventricular (LV) ejection fraction (EF). The extent to which these changes take place in patients undergoing TAVI (transcatheter aortic valve intervention) may be different than what has been observed in the surgical aortic valve replacement patients who were generally younger with few co-morbidities. Accordingly, we analyzed indices of LV structure and ventricular mechanics pre- and 1-year after TAVI in 397 patients (mean age 81±9, 46% women) with severe symptomatic aortic stenosis, complete echocardiographic data was available in 156 patients and these patients compromised our study population. Our principal findings are: (1) LV remodeling occurs after TAVI; (2) afterload decreases significantly; (3) LV chamber and myocardial function, assessed by left ventricular ejection fraction and midwall fractional shortening, and stroke volume, respectively, remain unchanged or decrease. In conclusion, TAVI effects LV remodeling despite significant co-morbidities. Thus, TAVI reduces afterload and leads to LV remodeling. Surprisingly, however, systolic function does not improve. These data run counter to the paradigm that afterload reduction improves systolic function and suggest that the response to afterload reduction is complex in the TAVI population.

Echocardiographic assessment of aortic stenosis: a practical guideline from the British Society of Echocardiography

The guideline provides a practical step-by-step guide in order to facilitate high-quality echocardiographic studies of patients with aortic stenosis. In addition, it addresses commonly encountered yet challenging clinical scenarios and covers the use of advanced echocardiographic techniques, including TOE and Dobutamine stress echocardiography in the assessment of aortic stenosis.

Mechanical Circulatory Support in Cardiogenic Shock due to Structural Heart Disease

Despite advances in cardiovascular care, managing cardiogenic shock caused by structural heart disease is challenging. Patients with cardiogenic shock are critically ill upon presentation and require early disease recognition and rapid escalation of care. Temporary mechanical circulatory support provides a higher level of care than current medical therapies such as vasopressors and inotropes. This review article focuses on the role of hemodynamic monitoring, mechanical circulatory support, and device selection in patients who present with cardiogenic shock due to structural heart disease. Early initiation of appropriate mechanical circulatory support may reduce morbidity and mortality.

Aortic valve stenosis-multimodality assessment with PET/CT and PET/MRI

Aortic valve disease is the most common form of heart valve disease in developed countries and a growing healthcare burden with an ageing population. Transthoracic and transoesophageal echocardiography remains central to the diagnosis and surveillance of patients with aortic stenosis, providing gold standard assessments of valve haemodynamics and myocardial performance. However, other multimodality imaging techniques are being explored for the assessment of aortic stenosis, including combined PET/CT and PET/MR. Both approaches provide unique information with respect to disease activity in the valve alongside more conventional anatomic assessments of the valve and myocardium in this condition. This review investigates the emerging use of PET/CT and PET/MR to assess patients with aortic stenosis, examining how the complementary data provided by each modality may be used for research applications and potentially in future clinical practice.

Regional heterogeneity of afterload sensitivity in myocardial strain

PURPOSE

The peak systolic strain decreases due to afterload augmentation. However, its deterioration (i.e., afterload sensitivity) may be different within the left ventricular (LV) segments. We investigated how afterload influences regional strain and whether there is regional heterogeneity of afterload sensitivity.

METHODS

Afterload was increased by aortic banding in 20 open-chest dogs. Short-axis images were acquired at baseline and during banding. Circumferential strain was analyzed in six segments, and the absolute decrease in the peak systolic strain during banding (Δε) was calculated for each segment. To assess the effect of the compensatory preload recruitment during banding, the endocardial lengths of the septum and free wall were measured at end-diastole, and the rate of increase due to banding was calculated.

RESULTS

LV systolic pressure was significantly increased during banding (100 ± 14 vs. 143 ± 18 mmHg, P < 0.001). The peak systolic strain in all segments was significantly decreased during banding. Δɛ in the anterior segment, which is a part of the free wall, was significantly lower than that in the inferoseptal segment (2.6 ± 4.7 vs. 6.5 ± 3.5%, P = 0.035). The rate of increase in endocardial length in the free wall was significantly larger than that in the septum (15.6 ± 10.4 vs. 8.1 ± 7.4%, P = 0.014).

CONCLUSION

The decrease in septal strain during afterload augmentation was larger than that in free wall strain, indicating that there was regional heterogeneity of afterload sensitivity in circumferential strain. The larger compensatory preload recruitment in the free wall than in the septum is implicated as a cause of the heterogeneity.

Impact of preprocedural left ventricle hypertrophy and geometrical patterns on mortality following TAVR

BACKGROUND

In contrast to surgical aortic valve replacement, left ventricle (LV) hypertrophy (LVH) had not been clearly associated with mortality following transcatheter aortic valve replacement (TAVR).

METHODS

We performed a retrospective analysis of patients enrolled in the Israeli multicenter TAVR registry for whom preprocedural LV mass index (LVMI) data were available. Patients were divided into categories according to LVMI: normal LVMI and mild, moderate, and severe LVH. Mild LVH was regarded as the reference group. Additionally, LV geometry patterns were examined (concentric and eccentric LVH, and concentric remodeling).

RESULTS

The cohort consisted of 1,559 patients, 46.5% male, with a mean age of 82.2 (±6.8) years and mean LVMI of 121 (±29) g/m². Rates of normal LVMI and mild, moderate, and severe LVH were 31% (n = 485), 21% (n = 322), 18% (n = 279), and 30% (n = 475), respectively. Three-year mortality rates for normal LVMI and mild, moderate, and severe LVH were 19.8%, 18.3%, 23.7%, and 24.4%, respectively. Compared to mild LVH, moderate LVH and severe LVH were independently associated with an increased risk for all-cause mortality (hazard ratio [HR] 1.58, 95% CI 1.15-2.18, P = .005; HR 1.46, 95% CI 1.1-1.95, P = .009; respectively). Concentric LVH was independently associated with a decreased risk for mortality compared to normal LV geometry (HR 0.75, 95% CI 0.63-0.89, P = .001). Compared to concentric LVH, eccentric LVH was independently associated with a 33% increased risk for mortality (HR 1.33, 95% CI 1.11-1.60, P = .002).

CONCLUSIONS

Mild concentric LVH confers a protective effect among patients with severe aortic stenosis undergoing TAVR. However, hypertrophy becomes maladaptive, and an increased baseline LVMI, eccentric pattern particularly, may be associated with all-cause mortality in this population.

Left Ventricular Contractility and Wall Stress in Patients With Aortic Stenosis With Preserved or Reduced Ejection Fraction

OBJECTIVES

This study sought to determine the prevalence of reduced contractility and uncompensated wall stress in patients with aortic stenosis (AS) with preserved or reduced left ventricular ejection fraction (LVEF) and their impact on survival.

BACKGROUND

LVEF in AS is determined not only by contractility but also by loading conditions.

METHODS

Patients with first diagnosis (time 0) of severe AS (aortic valve area [AVA]≤1 cm²) with prior echo study (-3±1 years) were identified. Contractility was evaluated by plotting midwall fractional shortening (mFS) against circumferential end-systolic wall stress (cESS), stratified by LVEF of 60% at time 0. The temporal changes (from -3 years to time 0) and prognostic value of LVEF, contractility, and wall stress were assessed.

RESULTS

Of 445 patients, 290 (65%) had LVEF ≥60% (median: 66% [interquartile range {IQR}: 63% to 69%]) and 155 patients (35%) had LVEF <60% (median: 47% [IQR: 34% to 55%]). Median AVA was 1.27 cm² (IQR: 1.13 to 1.43 cm²) at -3 years and 0.90 cm² (IQR: 0.83 to 0.96 cm²) at time 0. Decreased contractility was already present at -3 years (49 [17%] vs. 59 [38%]; LVEF ≥60% vs. <60%; p < 0.001) and became more prevalent at time 0 (69 [24%] vs. 106 [68%]; p < 0.001). Overall, wall stress was well controlled in both groups at -3 years (1 [0%] vs. 12 [8%]; p < 0.001) but deteriorated over time in patients with LVEF <60% (time 0: 0 [0%] vs. 26 [17%]; p < 0.001). During a median follow-up of 3.4 years, LVEF <60%, decreased contractility and high wall stress were associated with worse survival (p < 0.01 for all). Decreased contractility remained incremental to LVEF in patients with LVEF ≥60% (p < 0.01), but less so when LVEF was <60% (p = 0.11).

CONCLUSIONS

In patients with severe AS, LVEF <60% is associated with a poor prognosis, being linked with decreased contractility and/or high wall stress. Decreased contractility is also present in a subset of patients with LVEF ≥60% and provides incremental prognostic value. These abnormalities already exist before AVA reaches 1.0 cm².

Association Between Left Ventricle Diastolic Dysfunction and Unfavorable Prognostic Markers in Patients with Aortic Insufficiency

INTRODUCTION

The presence of symptoms, systolic dysfunction and Left Ventricle (LV) dilation are considered unfavourable prognostic markers in Aortic Valve Insufficiency (AVI). The role of diastolic dysfunction, which is considered unfavourable outcome marker in cardiac pathologies, is not well established in AVI.

AIM

To evaluate if the presence of diastolic dysfunction may be associated with unfavourable prognostic markers in AVI patients.

MATERIALS AND METHODS

A cross-sectional prospective study was performed on 22 patients with moderate or severe AVI. They underwent clinical evaluation and transthoracic echocardiography. Associations between clinical, epidemiological and echocardiographic were evaluated by Student t-test for normally distributed variables or Mann-Whitney test for non-normal distribution. Comparison between proportions was performed by Chi-square test.

RESULTS

There was an association between increased LV filling pressure, assessed by E' and E/E' of Mitral Tissue Doppler, and impaired LV systolic function, respectively: R = 0.563, R2 = 0.281; p = 0.008 and R = 0.639, R2 = 0.378; p = 0.002. The LV indexed mass also was inversely associated with the LV ejection fraction (R = 0.62, R2 = 0.35 and p = 0.003).

CONCLUSION

There was an association of LV diastolic dysfunction and ventricular hypertrophy with impaired left ventricle systolic function. Increased LV filling pressure and LV indexed mass should be considered in the management of AVI patients.

The Role of Imaging in Aortic Valve Disease

PURPOSE OF REVIEW

Aortic valve disease is the most common form of heart valve disease in developed countries. Imaging remains central to the diagnosis and risk stratification of patients with both aortic stenosis and regurgitation and has traditionally been performed with echocardiography. Indeed, echocardiography remains the cornerstone of aortic valve imaging as it is cheap, widely available and provides critical information concerning valve hemodynamics and ventricular function.

RECENT FINDINGS

Whilst diagnostic in the vast majority of patients, echocardiography has certain limitations including operator variability, potential for measurement errors and internal inconsistencies in severity grading. In particular, low-gradient severe aortic stenosis is common and challenging to diagnose. Aortic valve imaging may therefore be improved with alternative and complimentary multimodality approaches.

SUMMARY

This review investigates established and novel techniques for imaging both the aortic valve and the myocardial remodelling response including echocardiography, computed tomography, cardiovascular magnetic resonance and positron emission tomography. Moreover, we examine how the complementary information provided by each modality may be used in both future clinical practice and the research arena.

The role of cardiac biochemical markers in aortic stenosis

Calcified aortic stenosis is one of the most common causes of heart failure in the elderly. Current guidelines recommend aortic valve replacement in patients with severe disease and evidence of decompensation based on either symptoms or impaired systolic ejection fraction. However, symptoms are often subjective whilst impaired ejection fraction is not a sensitive marker of ventricular decompensation. Interest has surrounded the use of cardiac biochemical markers as objective measures of left ventricular decompensation in aortic stenosis. We will first examine mechanisms of release of biochemical markers associated with myocardial wall stress (BNP/NT-proBNP), myocardial fibrosis (markers of collagen metabolism, galectin-3, soluble ST2) and myocyte death/myocardial ischemia (high-sensitivity cardiac troponins, heart-type fatty acid binding protein, myosin-binding protein C); and discuss future directions of these markers.

Cardiac and Hemodynamic Benefits: Mode of Action of Ivabradine in Heart Failure

Heart failure has seen a number of therapeutic advances in recent years. Despite this, heart failure is still related to increasing rates of morbidity, repeated hospitalizations, and mortality. Ivabradine is a recent treatment option for heart failure. It has a mode of action that includes reduction in heart rate, and leads to improvement in outcomes related to heart failure mortality and morbidity, as demonstrated by the results of the SHIFT trial in patients with systolic heart failure, functional classes II and III on the New York Heart Association classification, and left ventricular ejection fraction ≤ 35%. These results are intriguing since many heart failure drugs reduce heart rate without such benefits, or with quite different effects, making it more difficult to understand the novelty of ivabradine in this setting. Many of the drugs used in heart failure modify heart rate, but most have other pathophysiological effects beyond their chronotropic action, which affect their efficacy in preventing morbidity and mortality outcomes. For instance, heart rate reduction at rest or exercise with ivabradine prolongs diastolic perfusion time, improves coronary blood flow, and increases exercise capacity. Another major difference is the increase in stroke volume observed with ivabradine, which may underlie its beneficial cardiac effects. Finally, there is mounting evidence from both preclinical and clinical studies that ivabradine has an anti-remodeling effect, improving left ventricular structures and functions. All together, these mechanisms have a positive impact on the prognosis of ivabradine-treated patients with heart failure, making a compelling argument for use of ivabradine in combination with other treatments.

Discrepancies in Left Ventricular Mass Calculation Based on Echocardiography and Cardiovascular Magnetic Resonance Measurements in Patients with Left Ventricular Hypertrophy

BACKGROUND

Increased left ventricular (LV) mass is associated with adverse cardiovascular outcomes, and its accurate assessment is important. The aim of this study was to analyze the degree of difference among various methods of LV mass calculation based on transthoracic echocardiographic (TTE) measurements and cardiovascular magnetic resonance (CMR) measurements, especially in patients with aortic stenosis with varying degrees of LV hypertrophy (LVH). The mechanism underlying this disagreement was also investigated.

METHODS

Ninety-nine patients with moderate to severe aortic stenosis and 33 control subjects matched for age, sex, body weight, and height were enrolled in this prospective observational cohort study. All patients underwent TTE and CMR imaging. LV mass index (LVMI) was calculated using three formulas on the basis of TTE measurements (the Penn-cube, American Society of Echocardiography [ASE], and Teichholz methods) and compared with measurements obtained using CMR, the reference method.

RESULTS

Although all methods calculated using TTE measurements showed good correlations with CMR measurements, LVMI measured using the Penn-cube and ASE methods tended to be larger than LVMI measured using CMR (difference in LVMI by the Penn-cube and ASE methods, 59.3 ± 29.7 and 30.6 ± 22.3 g/m², respectively). This tendency decreased with the Teichholz method (difference in LVMI by the Teichholz method, 22.9 ± 19.1 g/m²). The degree of LVMI overestimation was significantly different among the three methods (P < .001 by one-way analysis of variance), which was more significant in patients with LVH, especially with the Penn-cube method (differences between CMR and TTE measurements in patients with aortic stenosis and LVH, 66.3 ± 34.8 vs 31.2 ± 26.6 vs 15.5 ± 20.9 g/m² for the Penn-cube, ASE, and Teichholz methods, respectively; P < .001 with post hoc Tukey analysis). There was a good correlation between LVMI and LV diameter-to-length ratio (r = 0.468, P < .001), which suggested that the left ventricle takes on a more globular shape with the increase of LVMI, resulting in a significant deviation from the basic assumptions on which the Penn-cube and ASE methods were built.

CONCLUSIONS

Current methods of calculating LVMI from echocardiographic measurements carry a tendency to measure LVMI larger than methods based on CMR measurements, which was more significant in patients with LVH. The change of the left ventricle's shape with LVH may be a plausible explanation for this, and a correction method may be needed when calculating LVMI from echocardiographic measurements, especially in patients with LVH and smaller body size.

[Reverse myocardial remodeling in patients with aortic valve disease and mitral insufficiency in early postoperative period]

Surgical treatment of patients with aortic valve disease and concomitant mitral insufficiency remains debatable. We analyzed early postoperative results of surgical treatment of 80 patients depending on type of surgery. All patients were divided into three groups: the 1st - aortic valve replacement in patients without mitral valve dysfunction (control group) (n=44); the 2nd - isolated aortic valve replacement in patients with concomitant mitral regurgitation degree 2-3 (n=18), the 3rd - simultaneous aortic and mitral valve replacement (n=18). Combined valve replacement was associated with more intraoperative blood loss (852.78±442.08 ml) compared with aortic valve replacement (658.7±374.09 ml), p<0.05. In patients with mitral regurgitation greater hematocrit decrease was observed (22.13±3.6% in group 2 and 21.4±4.48 in group 3) in comparison with control group (24.17±3.72% in group 1), p<0.05. Incidence of postoperative complications did not differ in all groups. Mortality rate was 6.8% in group 1 and 11.1% in group 3, there were no deaths in group 2. Both valves correction provided faster myocardial remodeling. Left ventricular end-diastolic volume decreased on 50 ml in group 3, on 33.67 ml in group 2 and on 50.73 ml in group 1 (p<0.05). Pulmonary pressure decreased on 20 mm Hg in group 3, on 13 mm Hg - in group 2 and on 12.57 mm Hg - in group 1, p<0.05. In groups 1 and 3 pulmonary pressure became normal after operation, in group 2 signs of pulmonary hypertension were observed (pressure - 35.3 mm Hg). Analysis of the results showed that simultaneous mitral and aortic valves replacement initiates normalization of intracardiac hemodynamics in early postoperative period.

Cardiovascular function in large to small hibernators: bears to ground squirrels

Mammalian hibernation has intrigued scientists due to extreme variations in normal seasonal physiological homeostasis. Numerous species manifest a hibernation phenotype although the characteristics of the hypometabolic state can be quite different. Ground squirrels (e.g., Sciuridae) are often considered the prototypical hibernator as individuals in this genus transition from an active, euthermic state (37 °C) to a nonresponsive hibernating state where torpid body temperature commonly falls to 3-5 °C. However, the hibernating state is not continuous as periodic warming and arousals occur. In contrast, the larger hibernators of genus Ursus are less hypothermic (body temperatures decline from approximately 37°-33 °C), are more reactive, and cyclical arousals do not occur. Both species dramatically reduce cardiac output during hibernation from the active state (bears ~75 % reduction in bears and ~97 % reduction in ground squirrels), and both species demonstrate hypokinetic atrial chamber activity. However, there are several important differences in cardiac function between the two groups during hibernation. Left ventricular diastolic filling volumes and stroke volumes do not differ in bears between seasons, but increased diastolic and stroke volumes during hibernation are important contributors to cardiac output in ground squirrels. Decreased cardiac muscle mass and increased ventricular stiffness have been found in bears, whereas ground squirrels have increased cardiac muscle mass and decreased ventricular stiffness during hibernation. Molecular pathways of cardiac muscle plasticity reveal differences between the species in the modification of sarcomeric proteins such as titin and α myosin heavy chain during hibernation. The differences in hibernation character are likely to account for the alternative cardiac phenotypes and functional strategies manifested by the two species. Molecular investigation coupled with better knowledge of seasonal physiological alterations is dramatically advancing our understanding of small and large hibernators and their evolutionary differences.

ERBB2 deficiency alters an E2F-1-dependent adaptive stress response and leads to cardiac dysfunction

The tyrosine kinase receptor ERBB2 is required for normal development of the heart and is a potent oncogene in breast epithelium. Trastuzumab, a monoclonal antibody targeting ERBB2, improves the survival of breast cancer patients, but cardiac dysfunction is a major side effect of the drug. The molecular mechanisms underlying how ERBB2 regulates cardiac function and why trastuzumab is cardiotoxic remain poorly understood. We show here that ERBB2 hypomorphic mice develop cardiac dysfunction that mimics the side effects observed in patients treated with trastuzumab. We demonstrate that this phenotype is related to the critical role played by ERBB2 in cardiac homeostasis and physiological hypertrophy. Importantly, genetic and therapeutic reduction of ERBB2 activity in mice, as well as ablation of ERBB2 signaling by trastuzumab or siRNAs in human cardiomyocytes, led to the identification of an impaired E2F-1-dependent genetic program critical for the cardiac adaptive stress response. These findings demonstrate the existence of a previously unknown mechanistic link between ERBB2 and E2F-1 transcriptional activity in heart physiology and trastuzumab-induced cardiac dysfunction.

The role of adenosine in preconditioning by brief pressure overload in rats

BACKGROUND/PURPOSE

Brief pressure overload of the left ventricle reduced myocardial infarct (MI) size in rabbits has been previously reported. Its effects in other species are not known. This study investigates effects of pressure overload and the role of adenosine in rats in this study.

METHODS

MI was induced by 40-minute occlusion of the left anterior descending coronary artery followed by 3-hour reperfusion. MI size was determined by triphenyl tetrazolium chloride staining. Brief pressure overload was induced by two 10-minute episodes of partial snaring of the ascending aorta. Systolic left ventricular pressure was raised 50% above the baseline value. Ischemic preconditioning was elicited by two 10-minute coronary artery occlusions.

RESULTS

The MI size (mean ± standard deviation), expressed as percentage of area at risk, was significantly reduced in the pressure overload group as well as in the ischemic preconditioning group (17.4 ± 3.0% and 18.2 ± 1.5% vs. 26.6 ± 2.4% in the control group, p < 0.001). Pretreatment with 8-(p-sulfophenyl)-theophylline (SPT), an inhibitor of adenosine receptors, did not significantly limit the protection by pressure overload and ischemic preconditioning (18.3 ± 1.5% and 18.2 ± 2.0%, respectively, p < 0.001). SPT itself did not affect the extent of infarct (25.4 ± 2.0%). The hemodynamics, area at risk and mortality were not significantly different among all groups of animals.

CONCLUSION

Brief pressure overload of the left ventricle preconditioned rat myocardium against infarction. Because SPT did not significantly alter MI size reduction, our results did not support a role of adenosine in preconditioning by pressure overload in rats.

Increase in cardiac myosin heavy-chain (MyHC) alpha protein isoform in hibernating ground squirrels, with echocardiographic visualization of ventricular wall hypertrophy and prolonged contraction

Deep hibernators such as golden-mantled ground squirrels (Callospermophilus lateralis) have multiple challenges to cardiac function during low temperature torpor and subsequent arousals. As heart rates fall from over 300 beats min(-1) to less than 10, chamber dilation and reduced cardiac output could lead to congestive myopathy. We performed echocardiography on a cohort of individuals prior to and after several months of hibernation. The left ventricular chamber exhibited eccentric and concentric hypertrophy during hibernation and thus calculated ventricular mass was ~30% greater. Ventricular ejection fraction was mildly reduced during hibernation but stroke volumes were greater due to the eccentric hypertrophy and dramatically increased diastolic filling volumes. Globally, the systolic phase in hibernation was ~9.5 times longer, and the diastolic phase was 28× longer. Left atrial ejection generally was not observed during hibernation. Atrial ejection returned weakly during early arousal. Strain echocardiography assessed the velocity and total movement distance of contraction and relaxation for regional ventricular segments in active and early arousal states. Myocardial systolic strain during early arousal was significantly greater than the active state, indicating greater total contractile movement. This mirrored the increased ventricular ejection fraction noted with early arousal. However, strain rates were slower during early arousal than during the active period, particularly systolic strain, which was 33% of active, compared with the rate of diastolic strain, which was 67% of active. As heart rate rose during the arousal period, myocardial velocities and strain rates also increased; this was matched closely by cardiac output. Curiously, though heart rates were only 26% of active heart rates during early arousal, the cardiac output was nearly 40% of the active state, suggesting an efficient pumping system. We further analyzed proportions of cardiac myosin heavy-chain (MyHC) isoforms in a separate cohort of squirrels over 5 months, including time points before hibernation, during hibernation and just prior to emergence. Hibernating individuals were maintained in both a 4°C cold room and a 20°C warm room. Measured by SDS-PAGE, relative percentages of cardiac MyHC alpha were increased during hibernation, at both hibernacula temperatures. A potential increase in contractile speed, and power, from more abundant MyHC alpha may aid force generation at low temperature and at low heart rates. Unlike many models of cardiomyopathies where the alpha isoform is replaced by the beta isoform in order to reduce oxygen consumption, ground squirrels demonstrate a potential cardioprotective mechanism to maintain cardiac output during torpor.

Introduction to aortic stenosis

Aortic stenosis is perhaps the most common of all valvular heart diseases in the developed nations of the world. Once primarily caused by rheumatic fever, the most common pathogenesis today is an active inflammatory process with some features that are similar to atherosclerosis. Because of this shift, the age at onset of severe obstruction has changed from the sixth decade 50 years ago to the eighth decade in most individuals today. The onset of symptoms remains a key determinant of outcome, although the later age at onset may make it difficult to discern if aortic stenosis or other age-related comorbidities is the cause of the symptoms. Once symptoms of aortic stenosis develop, life expectancy is shortened to ≈3 years unless the mechanical obstruction to left ventricular outflow is relieved by aortic valve replacement. Traditionally performed during cardiac surgery, aortic valve replacement now may be performed safely and effectively using transcatheter techniques, potentially revolutionizing the approach to this potentially fatal disease.

Myocardial stress and hypertrophy: a complex interface between biophysics and cardiac remodeling

Pressure and volume overload results in concentric and eccentric hypertrophy of cardiac ventricular chambers with, respectively, parallel and series replication of sarcomeres. These divergent patterns of hypertrophy were related 40 years ago to disparate wall stresses in both conditions, with systolic wall stress eliciting parallel replication of sarcomeres and diastolic wall stress, series replication. These observations are relevant to clinical practice, as they relate to the excessive hypertrophy and contractile dysfunction regularly observed in patients with aortic stenosis. Stress-sensing mechanisms in cardiomyocytes and activation of cardiomyocyte death by elevated wall stress continue to intrigue cardiovascular scientists.

Coexisting cardiac diseases and pressure recovery phenomenon contribute to discrepancy between the echocardiographic severity of aortic stenosis and left ventricular hypertrophy

BACKGROUND

Assessing left ventricular (LV) hypertrophy (LVH) is an important step in the echocardiographic diagnosis of aortic stenosis (AS). We aimed to investigate the causes of discrepancies between the degrees of AS and LVH.

METHODS

The study subjects consisted of 149 consecutive patients with AS having aortic valve area <2.0 cm(2) (mean age 72.5 ± 11.9 years, 67 men and 82 women). Coexisting cardiac diseases were determined based on echocardiographic findings and comprehensive clinical judgment. Echocardiographic measurements included LV mass index (LVMI), aortic valve area index (AVAI), transaortic mean pressure gradient (MPG), valvulo-arterial impedance (Zva), energy loss coefficient (ELCo), and energy loss index (ELI).

RESULTS

LVMI was not significantly correlated with AVAI and Zva, and had a weak correlation with MPG (r = 0.305, p = 0.0001). There were 55 patients in group A (non-severe AS without significant LVH), 58 in group B (non-severe AS with significant LVH), 7 in group C (severe AS without significant LVH), and 29 in group D (severe AS with significant LVH). Coexisting cardiac diseases were more frequently observed (p = 0.0003) in group B (50 %) than in group A (18 %). In group C, ELCo and (ELI - AVAI)/ELI were significantly greater than in group D (p = 0.043 and 0.007, respectively).

CONCLUSION

Significant LVH seen in less than moderate AS is often due to coexisting cardiac diseases, and there may be an overestimation of AS severity due to pressure recovery among patients with apparently severe AS who do not have significant LVH.

The safety and efficacy of enhanced external counterpulsation as a treatment for angina in patients with aortic stenosis

BACKGROUND

Comorbid aortic stenosis (AS) has been considered a precaution when applying enhanced external counterpulsation (EECP) to individuals with angina due to concerns about treatment-related hemodynamic changes.

HYPOTHESIS

The aim of this study was to determine whether EECP safely reduces symptoms of myocardial ischemia and improves hemodynamics in individuals with AS.

METHODS

Forty-three patients with AS (average age, 73 years; 86% male) and 43 comparison patients without AS were chosen from a database of 1327 EECP patients. Canadian Cardiovascular Society (CCS) Functional Angina Classification, diastolic augmentation ratio, and blood pressure were measured at baseline and on completion of the course of EECP.

RESULTS

Thirty-five of the 43 patients with AS (81%, 95% CI: 66.6% to 91.6%) and 38 of the 43 without AS (88%, 95% CI: 74.9% to 96.1%) improved in angina class (P < 0.0001). There was no statistical difference between the percentages in patients with and without AS (P = 0.54). CCS angina class outcome was not associated with AS severity (P = 0.55). The percentage of patients with diastolic augmentation ratio ≥1.0 was 16.3% in both groups at baseline and improved to 39.5% in AS patients and 37.2% in non-AS patients after EECP (both P = 0.002). The average decreases in systolic blood pressure in subjects with AS (-15 mm Hg, 95% CI: 11 to 20, P < 0.0001) and without AS (-18 mm Hg, 95% CI: 14 to 22, P < 0.0001) were similar (P = 0.31). No major adverse cardiac events were reported.

CONCLUSIONS

Angina patients with AS who undergo EECP had clinically important symptomatic and hemodynamic improvements comparable to their non-AS counterparts.

Calcific aortic stenosis: a disease of the valve and the myocardium

Although aortic stenosis is a common condition associated with major morbidity, mortality, and health economic costs, there are currently no medical interventions capable of delaying or halting its progression. Re-evaluation of the underlying pathophysiology is therefore required so that novel therapeutic strategies can be developed. Aortic stenosis is characterized by progressive aortic valve narrowing and secondary left ventricular hypertrophy. Both processes are important because in combination they drive the development of symptoms and adverse events that characterize the latter stages of the disease. In this review, the authors examine the pathophysiology of aortic stenosis with respect to both the valve and the myocardium. In particular, the authors focus on the role of inflammation, fibrosis, and calcification in progressive valve narrowing and then examine the development of left ventricular hypertrophy, its subsequent decompensation, and the transition to heart failure. Finally the authors discuss potential therapeutic strategies on the basis of similarities aortic stenosis shares with other pathological conditions.

Left ventricular remodeling and hypertrophy in patients with aortic stenosis: insights from cardiovascular magnetic resonance

BACKGROUND

Cardiovascular magnetic resonance (CMR) is the gold standard non-invasive method for determining left ventricular (LV) mass and volume but has not been used previously to characterise the LV remodeling response in aortic stenosis. We sought to investigate the degree and patterns of hypertrophy in aortic stenosis using CMR.

METHODS

Patients with moderate or severe aortic stenosis, normal coronary arteries and no other significant valve lesions or cardiomyopathy were scanned by CMR with valve severity assessed by planimetry and velocity mapping. The extent and patterns of hypertrophy were investigated using measurements of the LV mass index, indexed LV volumes and the LV mass/volume ratio. Asymmetric forms of remodeling and hypertrophy were defined by a regional wall thickening ≥ 13 mm and >1.5-fold the thickness of the opposing myocardial segment.

RESULTS

Ninety-one patients (61 ± 21 years; 57 male) with aortic stenosis (aortic valve area 0.93 ± 0.32 cm2) were recruited. The severity of aortic stenosis was unrelated to the degree (r2=0.012, P=0.43) and pattern (P=0.22) of hypertrophy. By univariate analysis, only male sex demonstrated an association with LV mass index (P=0.02). Six patterns of LV adaption were observed: normal ventricular geometry (n=11), concentric remodeling (n=11), asymmetric remodeling (n=11), concentric hypertrophy (n=34), asymmetric hypertrophy (n=14) and LV decompensation (n=10). Asymmetric patterns displayed considerable overlap in appearances (wall thickness 17 ± 2mm) with hypertrophic cardiomyopathy.

CONCLUSIONS

We have demonstrated that in patients with moderate and severe aortic stenosis, the pattern of LV adaption and degree of hypertrophy do not closely correlate with the severity of valve narrowing and that asymmetric patterns of wall thickening are common.

Dissociation of structural and functional phenotypes in cardiac myosin-binding protein C conditional knockout mice

BACKGROUND

Cardiac myosin-binding protein C (cMyBP-C) is a sarcomeric protein that dynamically regulates thick-filament structure and function. In constitutive cMyBP-C knockout (cMyBP-C(-/-)) mice, loss of cMyBP-C has been linked to left ventricular dilation, cardiac hypertrophy, and systolic and diastolic dysfunction, although the pathogenesis of these phenotypes remains unclear.

METHODS AND RESULTS

We generated cMyBP-C conditional knockout (cMyBP-C-cKO) mice expressing floxed cMyBP-C alleles and a tamoxifen-inducible Cre-recombinase fused to 2 mutated estrogen receptors to study the onset and progression of structural and functional phenotypes caused by the loss of cMyBP-C. In adult cMyBP-C-cKO mice, knockdown of cMyBP-C over a 2-month period resulted in a corresponding impairment of diastolic function and a concomitant abbreviation of systolic ejection, although contractile function was largely preserved. No significant changes in cardiac structure or morphology were immediately evident; however, mild hypertrophy developed after near-complete knockdown of cMyBP-C. In response to pressure overload induced by transaortic constriction, cMyBP-C-cKO mice treated with tamoxifen also developed greater cardiac hypertrophy, left ventricular dilation, and reduced contractile function.

CONCLUSIONS

These results indicate that myocardial dysfunction is largely caused by the removal of cMyBP-C and occurs before the onset of cytoarchitectural remodeling in tamoxifen-treated cMyBP-C-cKO myocardium. Moreover, near ablation of cMyBP-C in adult myocardium primarily leads to the development of hypertrophic cardiomyopathy in contrast to the dilated phenotype evident in cMyBP-C(-/-) mice, which highlights the importance of additional factors such as loading stress in determining the expression and progression of cMyBP-C-associated cardiomyopathy.

Impact of renin-angiotensin system blockade therapy on outcome in aortic stenosis

OBJECTIVES

The purpose of this study was to investigate the impact of renin-angiotensin system blockade therapy on outcomes in aortic stenosis (AS).

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are perceived to be relatively contraindicated in AS. However, inhibitors of the renin-angiotensin system may be beneficial in AS through their cardioprotective and beneficial effects on left ventricular remodeling.

METHODS

The Health Informatics dispensed prescribing, morbidity, and mortality database for the population of Tayside, Scotland, was linked through a unique patient identifier to the Tayside echocardiography database (>110,000 scans). Patients with a diagnosis of AS from 1993 to 2008 were identified. Cox regression model (adjusted for confounding variables) and propensity score analysis were used to assess the impact of ACEIs or ARBs on all-cause mortality and cardiovascular (CV) events (CV death or hospitalizations).

RESULTS

A total of 2,117 patients with AS (mean age 73 ± 12 years, 46% men) were identified and 699 (33%) were on ACEI or ARB therapy. Over a mean follow-up of 4.2 years, there were 1,087 (51%) all-cause deaths and 1,018 (48%) CV events. Those treated with ACEIs or ARBs had a significantly lower all-cause mortality with an adjusted hazard ratio of 0.76 (95% confidence interval: 0.62 to 0.92, p < 0.0001) and fewer CV events with an adjusted hazard ratio of 0.77 (95% confidence interval: 0.65 to 0.92, p < 0.0001). The outcome benefits of ACEIs/ARBs were further supported by propensity score analysis.

CONCLUSIONS

This large observational study suggests that ACEI/ARB therapy is associated with an improved survival and a lower risk of CV events in patients with AS.