Systemic Circulation in Advanced Heart Failure and Cardiogenic Shock: State-of-the-Art Review

The integrative physiology of the left ventricle and systemic circulation is fundamental to our understanding of advanced heart failure and cardiogenic shock. In simplest terms, any increase in aortic stiffness increases the vascular afterload presented to the failing left ventricle. The net effect is increased myocardial oxygen demand and reduced coronary perfusion pressure, thereby further deteriorating contractile function. Although mechanical circulatory support devices should theoretically work in concert with guideline-directed medical therapy, cardiac resynchronization and inotropic and vasopressor agents designed to support myocardial performance and enhance left ventricle recovery, this does not always occur. Each therapy and intervention may result in vastly different and sometimes deleterious effects on vascular afterload. Although best described by a combination of both steady-state and pulsatile components, the latter is frequently overlooked when mean arterial pressure or systemic vascular resistance alone is used to quantify vascular afterload in advanced heart failure and cardiogenic shock. In this state-of-the-art review, we examine what is known about vascular afterload in advanced heart failure and cardiogenic shock, including the use of temporary and permanent mechanical circulatory support systems. Importantly, we outline 4 key components for a more complete assessment of vascular afterload. Unlike previous discussions on this topic, we set aside considerations of venous return and ventricular preload, as important as they are, to focus exclusively on the hydraulic load within the systemic circulation against which the impaired left ventricle must contract.

Development and Clinical Application of Left Ventricular-Arterial Coupling Non-Invasive Assessment Methods

The constant and dynamic interaction between ventricular function and arterial afterload, known as ventricular-arterial coupling, is key to understanding cardiovascular pathophysiology. Ventricular-arterial coupling has traditionally been assessed invasively as the ratio of effective arterial elastance over end-systolic elastance (Ea/Ees), calculated from information derived from pressure-volume loops. Over the past few decades, numerous invasive and non-invasive simplified methods to estimate the elastance ratio have been developed and applied in clinical investigation and practice. The echocardiographic assessment of left ventricular Ea/Ees, as proposed by Chen and colleagues, is the most widely used method, but novel echocardiographic approaches for ventricular-arterial evaluation such as left ventricle outflow acceleration, pulse-wave velocity, and the global longitudinal strain or global work index have arisen since the former was first published. Moreover, multimodal imaging or artificial intelligence also seems to be useful in this matter. This review depicts the progressive development of these methods along with their academic and clinical application. The left ventricular-arterial coupling assessment may help both identify patients at risk and tailor specific pharmacological or interventional treatments.

Relationship between intraventricular mechanical dyssynchrony and left ventricular systolic and diastolic performance: An in vivo experimental study

Left ventricular mechanical dyssynchrony (LVMD) refers to the nonuniformity in mechanical contraction and relaxation timing in different ventricular segments. We aimed to determine the relationship between LVMD and LV performance, as assessed by ventriculo-arterial coupling (VAC), LV mechanical efficiency (LVeff ), left ventricular ejection fraction (LVEF), and diastolic function during sequential experimental changes in loading and contractile conditions. Thirteen Yorkshire pigs submitted to three consecutive stages with two opposite interventions each: changes in afterload (phenylephrine/nitroprusside), preload (bleeding/reinfusion and fluid bolus), and contractility (esmolol/dobutamine). LV pressure-volume data were obtained with a conductance catheter. Segmental mechanical dyssynchrony was assessed by global, systolic, and diastolic dyssynchrony (DYS) and internal flow fraction (IFF). Late systolic LVMD was related to an impaired VAC, LVeff , and LVEF, whereas diastolic LVMD was associated with delayed LV relaxation (logistic tau), decreased LV peak filling rate, and increased atrial contribution to LV filling. The hemodynamic factors related to LVMD were contractility, afterload, and heart rate. However, the relationship between these factors differed throughout the cardiac cycle. LVMD plays a significant role in LV systolic and diastolic performance and is associated with hemodynamic factors and intraventricular conduction.

Altered Aortic Hemodynamics and Relative Pressure in Patients with Dilated Cardiomyopathy

Ventricular-vascular interaction is central in the adaptation to cardiovascular disease. However, cardiomyopathy patients are predominantly monitored using cardiac biomarkers. The aim of this study is therefore to explore aortic function in dilated cardiomyopathy (DCM). Fourteen idiopathic DCM patients and 16 controls underwent cardiac magnetic resonance imaging, with aortic relative pressure derived using physics-based image processing and a virtual cohort utilized to assess the impact of cardiovascular properties on aortic behaviour. Subjects with reduced left ventricular systolic function had significantly reduced aortic relative pressure, increased aortic stiffness, and significantly delayed time-to-pressure peak duration. From the virtual cohort, aortic stiffness and aortic volumetric size were identified as key determinants of aortic relative pressure. As such, this study shows how advanced flow imaging and aortic hemodynamic evaluation could provide novel insights into the manifestation of DCM, with signs of both altered aortic structure and function derived in DCM using our proposed imaging protocol.

Ventricular-arterial coupling: definition, pathophysiology and therapeutic targets in cardiovascular disease

INTRODUCTION

The heart and arterial system are equally affected by arteriosclerosis/atherosclerosis. There is a constant interaction between the left ventricular (LV) function and the arterial system, termed ventricular-arterial coupling (VAC), which reflects the global cardiovascular efficiency. VAC is traditionally assessed by echocardiography as the ratio of effective arterial elastance (E_a) over end-systolic elastance (E_es) (E_a/E_es). However, the concept of VAC is evolving and new methods have been proposed such as the ratio of pulse wave velocity (PWV) to global longitudinal strain (GLS) and myocardial work index.

AREA COVERED

This clinical review presents the hemodynamic background of VAC, its clinical implications and the impact of therapeutic interventions to normalize VAC. The review also summarizes the detrimental effects of cardio-metabolic risk factors on the aorta and LV, and provides an update on arterial load and its impact on LV function. The narrative review is based upon a systemic search of the bibliographic database PubMed for publications on VAC.

EXPERT OPINION

Newer methods such as PWV/GLS-ratio may be a superior marker of VAC than the traditional echocardiographic E_a/E_es in predicting target organ damage and its association with clinical outcomes. Novel anti-diabetic drugs and optimal antihypertensive treatment may normalize VAC in high-risk patients.

Noninvasive Assessment of Ventricular-Arterial Coupling in Heart Failure

The heart and the arterial system are anatomically and functionally linked together. Noninvasive assessment of ventricular-arterial coupling (VAC) can be done using different methods that are promising tools to assess individual hemodynamics and tailor treatment in patients with heart failure (HF). Moreover, different methods available can be appropriately used in different settings such as acute and chronic HF. VAC parameters also can add incremental value over the conventional risk factors in predicting cardiac outcome.

The role of ventricular-arterial coupling in cardiac disease and heart failure: assessment, clinical implications and therapeutic interventions. A consensus document of the European Society of Cardiology Working Group on Aorta & Peripheral Vascular Diseases, European Association of Cardiovascular Imaging, and Heart Failure Association

Ventricular-arterial coupling (VAC) plays a major role in the physiology of cardiac and aortic mechanics, as well as in the pathophysiology of cardiac disease. VAC assessment possesses independent diagnostic and prognostic value and may be used to refine riskstratification and monitor therapeutic interventions. Traditionally, VAC is assessed by the non-invasive measurement of the ratio of arterial (Ea) to ventricular end-systolic elastance (Ees). With disease progression, both Ea and Ees may become abnormal and the Ea/Ees ratio may approximate its normal values. Therefore, the measurement of each component of this ratio or of novel more sensitive markers of myocardial (e.g. global longitudinal strain) and arterial function (e.g. pulse wave velocity) may better characterize VAC. In valvular heart disease, systemic arterial compliance and valvulo-arterial impedance have an established diagnostic and prognostic value and may monitor the effects of valve replacement on vascular and cardiac function. Treatment guided to improve VAC through improvement of both or each one of its components may delay incidence of heart failure and possibly improve prognosis in heart failure. In this consensus document, we describe the pathophysiology, the methods of assessment as well as the clinical implications of VAC in cardiac diseases and heart failure. Finally, we focus on interventions that may improve VAC and thus modify prognosis.

Clinical-Physiological Considerations in Patients Undergoing Staged Palliation for a Functionally Single Ventricle

OBJECTIVES

The objectives of this review are to discuss the pathophysiology of the circulation with a functionally univentricular heart, with a focus on the unique physiologic characteristics, which provide the underpinnings for the management of these complex patients.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

The circulation of the patient with a functionally univentricular heart displays unique physiologic characteristics, which are quite different from those of the normal biventricular circulation. There are profound differences within the heart itself in terms of ventricular function, interventricular interactions, and myocardial architecture, which are likely to have significant implications for the efficiency of ventricular ejection and metabolism. The coupling between the systemic ventricle and the aorta also displays unique features. The 3D orientation of the Fontan anastomosis itself can profoundly impact cardiac output, although the "portal" pulmonary arterial bed is a crucial determinant of overall cardiovascular function. As a result, disease-specific approaches to improve cardiovascular function are required at all stages during the care of these complex patients.

Effects of Cardiac Resynchronization Therapy on Cardiac Remodeling and Contractile Function: Results From Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction (REVERSE)

Background

Cardiac resynchronization therapy results in improved ejection fraction in patients with heart failure. We sought to determine whether these effects were mediated by changes in contractility, afterload, or volumes.

Methods and Results

In 610 patients with New York Heart Association class I/II heart failure from the Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction (REVERSE) study, we performed detailed quantitative echocardiography assessment prior to and following cardiac resynchronization therapy. We derived measures of contractility (the slope [end-systolic elastance] and the volume intercept of the end-systolic pressure–volume relationship, stroke work, and preload recruitable stroke work), measures of arterial load and ventricular–arterial coupling, and measures of chamber size (volume intercept, end-systolic and end-diastolic volumes). At 6 and 12 months, cardiac resynchronization therapy was associated with a reduction in the volume intercept and end-systolic and end-diastolic volumes (P<0.01). There were no consistent effects on end-systolic elastance, stroke work, preload recruitable stroke work, or ventricular–arterial coupling. In the active cardiac resynchronization therapy population, baseline measures of arterial load were associated with the clinical composite score (odds ratio 1.30, 95% CI 1.04 to 1.63, P=0.02). The volume intercept was associated with mortality (hazard ratio 1.90, 95% CI 1.01 to 3.59, P=0.047) and more modestly with the combined end point of mortality or heart failure hospitalization (hazard ratio 1.48, 95% CI 0.8 to 2.25, P=0.06). In contrast, end-systolic elastance, stroke work, preload recruitable stroke work, and ventricular–arterial coupling were not associated with any outcomes.

Conclusion

In patients with NYHA Class I/II heart failure, cardiac resynchronization therapy exerts favorable changes in left ventricular end-systolic and end-diastolic volumes and the volume intercept. The volume intercept may be useful to gain insight into prognosis in heart failure.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique identifier: NCT00271154.

The Ventricular-Arterial Coupling: From Basic Pathophysiology to Clinical Application in the Echocardiography Laboratory

The interplay between cardiac function and arterial system, which in turn affects ventricular performance, is defined commonly ventricular-arterial coupling and is an expression of global cardiovascular efficiency. This relation can be expressed in mathematical terms as the ratio between arterial elastance (EA) and end-systolic elastance (EES) of the left ventricle (LV). The noninvasive calculation requires complicated formulae, which can be, however, easily implemented in computerized algorithms, allowing the adoption of this index in the clinical evaluation of patients. This review summarizes the up-to-date literature on the topic, with particular focus on the main clinical studies, which range over different clinical scenarios, namely hypertension, heart failure, coronary artery disease, and valvular heart disease.

Cardiac resynchronization results in aortic blood flow-associated changes in the arterial load components: basal biomechanical conditions determine the load changes

The cardiac resynchronization therapy (CRT)effects on the arterial load components, the mechanisms (i.e.haemodynamic changes-dependence) involved in the load reduction and the factors (i.e. basal load conditions) associated with the load changes after CRT, are to be evaluated.

AIMS

a)to analyze the potential changes in the arterial load components(peripheral resistances, arterial compliance and impedance)associated with the CRT, b) to determine if the load components changes are associated with variations in haemodynamic variables (pressure, heart rate or blood flow), c) to analyze the relationship between the load components basal state and their changes after CRT. To fulfill these aims cardiac and arterial structural and mechanical parameters were non-invasively evaluated in 8 heart failure patients, pre- and post-CRT (23+/-8 days). The main results were that short-term after CRT: 1)there were changes in the static and dynamic determinants of the arterial load; 2) the changes in the load components were not associated with heart rate or pressure variations, but with blood flow changes, and 3) the load components basal levels and their changes after CRT were associated.