Non invasive evaluation of cardiomechanics in patients undergoing MitrClip procedure

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.

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.

Age related structural and functional changes in left ventricular performance in healthy subjects: a 2D echocardiographic study

Left ventricular (LV) adaptation to aging is currently poorly understood. We aimed to characterize age related changes in LV structure and function by studying a large group of healthy subjects across a wide age range. Prospectively enrolled healthy volunteers (n = 778, 327 females; age 18 to 100 years, mean age 49.8 ± 18.1 years), were divided into 4 age groups: 18 to 34 years (n = 165); 35 to 49 years (n = 242), 50 to 79 years (n = 334) and ≥ 80 years (n = 40). All subjects underwent clinical examination, as well as comprehensive transthoracic echocardiogram [TTE]. Body mass index, systolic blood pressure (BP), and left atrial volume (p < 0.0001) increased with age while diastolic BP (p < 0.0001) decreased over time. LV mass/body surface area (BSA) and relative wall thickness increased with age (p < 0.0001) coincident with worsening parameters of diastolic function (E/A and E/Em, p < 0.0001). The ejection fraction and Sm did not change significantly. Stroke volume, ejection time index, flow rate and stroke work significantly increased with age (p < 0.01). The arterial elastance (Ea), a measure of ventricular afterload, and ventricular elastance (Ees), an index of LV systolic stiffness did not change with age nor did their ratio (Ees/Ea) the latter being an expression of ventricular-arterial coupling. Age, gender and LVM were the main independent variables associated with LV systolic function. In conclusion, LV adaptation to aging in a healthy cohort is characterized by concentric LV remodeling, increased contractility and preserved ventricular-arterial coupling.

Evaluation of ventriculo-arterial coupling in ST elevation myocardial infarction with left ventricular dysfunction treated with levosimendan

BACKGROUND

Acute heart failure (AHF) after ST-segment elevation myocardial infarction (STEMI) is usually treated with inotropic support or vasoactive medications. In this study, we aimed at investigating the role of levosimendan on cardiovascular determinants of contractility and afterload in patients with AHF following STEMI treated with percutaneous coronary intervention (PCI).

METHODS

Forty-eight consecutive STEMI patients were retrospectively enrolled. Non-invasive assessment of left ventricular elastance (Ees) and arterial elastance (Ea) and their relationship, ventriculo-arterial coupling (VAC) was performed before and after levosimendan infusion.

RESULTS

After infusion of levosimendan a significant increase in SV was detected in all patients (from 48 ± 17 to 60 ± 21 ml, p < 0.001). VAC slightly decreased from 1.74 ± 0.8 to 1.66 ± 0.7 (p = NS) as a result of a profound reduction in arterial elastance (Ea 2.34 ± 1.09 to 1.74 ± 0.5 mm Hg/ml, p < 0.001) and in ventricular elastance (Ees 1.57 ± 0.12 to 1.24 ± 0.09 mm Hg/ml, p = 0.021). Ejection fraction (EF) (from 0.29 ± 0.1 to 0.32 ± 0.1, p < 0.01) and WMSI, (from 2.16 ± 0.47 to 2.05 ± 0.54, p < 0.05) also, significantly improved. Finally, baseline VAC was able to predict the use of norepinephrine (NE) and early and one-year mortality of patients treated.

CONCLUSION

In STEMI patients with AHF the use of levosimendan significantly increases stroke volume after 24-hour treatment through Ea reduction. Baseline VAC seemed to predict early and late mortality and early and prolonged use of NE, however, this needs to be tested in larger series of patients and multivariate adjustments for other prognostic predictors.

Relationship between Microcirculatory Perfusion and Arterial Elastance: A Pilot Study

Background

Arterial elastance (Ea) represents the total afterload imposed on the left ventricle, and it is largely influenced by systemic vascular resistance (SVR). Although one can expect that Ea is influenced by peripheral endothelial function, no data are available to support it in patients. The aim of this study was to investigate the relationship between Ea, SVR, and microvascular perfusion in critically ill patients undergoing the fluid challenge (FC).

Methods

A prospective study in patients receiving a fluid challenge. A pulse wave analysis system (MostCare, Vygon, France) was used to estimate Ea and an incident dark field (IDF) handheld device (Braedius Medical BV, The Netherlands) to evaluate the sublingual microcirculation. Microvascular perfusion was assessed using the proportion of small-perfused vessels (PPV). Relative changes in each variable were calculated before and after FC; fluid responsiveness was defined as an increase in the cardiac index by at least 10% from baseline.

Results

We studied 20 patients requiring a fluid challenge (n=10 for hypotension; n=5 for oliguria; n=3 for lactate values greater than 2 mmol/l; n=2 for tachycardia), including 12 fluid responders. There was a strong correlation between Ea and SVR (r² = 0.75; p < 0.001) and only a weak correlation between Ea and PPV at baseline (r² = 0.22; p=0.04). Ea decreased from 1.4 [1.2–1.6] to 1.2 [1.1–1.4] mmHg/mL (p=0.01), SVR from 1207 [1006–1373] to 1073 [997–1202] dyn ∗ s/cm⁵ (p=0.06), and PPV from 56 [51–64] % to 59 [47–73] % (p=0.25) after fluid challenge. Changes in Ea were significantly correlated with changes in SVR, but not with changes in PPV.

Conclusions

The correlation between Ea and indexes of microvascular perfusion in the sublingual region is weak. The impact of microcirculatory perfusion on the arterial load is probably limited.

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.

Early Hemodynamic Improvement after Percutaneous Mitral Valve Repair Evaluated by Noninvasive Pressure-Volume Analysis

BACKGROUND

Mitral regurgitation represents a volume load on the left ventricle leading to congestion and symptoms of heart failure. The aim of this study was to characterize early hemodynamic adaptions after percutaneous mitral valve (MV) repair.

METHODS

Forty-six consecutive patients with symptomatic high-grade MV insufficiency (mean age, 72 years; 54% men) were prospectively included in the study and examined before and after successful catheter-based clip implantation. Seventy percent of patients had secondary mitral regurgitation. Noninvasive pressure-volume loops were reconstructed from echocardiography with simultaneous blood pressure measurements.

RESULTS

MV repair reduced left ventricular end-diastolic volume index from 87 ± 41 to 80 ± 40 mL/m(2) (P < .0001). End-systolic volume index was 55 ± 37 mL/m(2) before versus 54 ± 37 mL/m(2) after repair (P = .52). Hence, total stroke volume decreased from 60 ± 23 to 49 ± 16 mL (P < .0001), as did total ejection fraction (from 41 ± 14% to 37 ± 13%, P = .002) and global longitudinal strain (from -11 ± 4.9% to -9.1 ± 4.4%, P = .0001). Forward stroke volume, forward ejection fraction, and forward cardiac output remained constant (43 ± 12 mL vs 42 ± 11 mL, 33 ± 17% vs 35 ± 18%, and 3.2 ± 0.9 L/min vs 3.4 ± 0.8 L/min, respectively). Parameters of left ventricular contractility (end-systolic elastance and peak power index) and measurements of afterload (arterial elastance, end-systolic wall stress, and total peripheral resistance) were similar before and after MV repair. Forward ejection fraction correlated more strongly with end-systolic elastance (r = 0.61, P < .0001) than did total ejection fraction (r = 0.35, P = .0007) or global longitudinal strain (r = -0.38, P = .0002). Total mechanical energy (pressure-volume area) decreased from 10,903 ± 4,410 to 9,124 ± 2,968 mm Hg × mL (P = .0007) because of reduced stroke work (5,546 ± 2,241 mm Hg × mL vs 4,414 ± 1,412 mm Hg × mL, P < .0001). At 3 months, symptom status had improved (76% of patients in New York Heart Association classes I and II), and 97% of patients had mitral regurgitation grade ≤2+.

CONCLUSIONS

Left ventricular contractility and forward cardiac output remained unchanged after percutaneous MV repair despite decreases in total ejection fraction and global longitudinal strain. The left ventricle was unloaded through reduced end-diastolic volume. Thus, MV repair is associated with an improved hemodynamic state in noninvasive pressure-volume analysis.

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.