Assessment of absolute coronary flow and microvascular resistance reserve in patients with severe aortic stenosis

Introduction

The development of left ventricular hypertrophy in patients with severe aortic stenosis (AS) is accompanied by adaptive coronary flow regulation, both in epicardial and microvascular compartment, which ultimately lead to a chronic ischemic insult even in the absence of obstructive coronary artery disease. Intracoronary continuous thermodilution of saline through a dedicated infusion catheter is a novel tool that allows to measure absolute coronary flow and microvascular resistance at rest and during hyperemia and to calculate both coronary flow reserve (CFR) and Microvascular Resistance Reserve (MRR)

Purpose

We aimed to assess absolute coronary flow, microvascular resistance, CFR and MRR in patients with AS, by continuous intracoronary thermodilution, comparing these hemodynamic findings with a propensity-score matched contemporary cohort of patients without AS.

Methods

Absolute coronary blood flow and microvascular resistance were measured by continuous thermodilution in 29 patients with AS and compared to 15 controls matched for age, gender, diabetes mellitus and functional severity of epicardial coronary lesions. Myocardial work, total myocardial mass and LAD-specific mass were quantified by echocardiography and cardiac-CT.

Results

Patients with AS presented a significantly positive LV remodeling with lower global longitudinal strain and higher global work index compared to controls (p<0.02). Total LV myocardial mass and LAD-specific myocardial mass were significantly higher in patients with AS. Compared to matched controls, absolute resting flow in the LAD was significantly higher in the AS cohort (86 [66–107] ml/min vs 68 [52–75] ml/min, p=0.036), resulting, in lower CFR (2.30±0.69 vs 2.89±0.77, p=0.005) and MRR (2.73±0.74 vs 3.53±0.95, p=0.005) in the AS cohort compared to controls (Figure 1). No differences were found in hyperemic flow and resting and hyperemic resistances. Interestingly, hyperemic myocardial perfusion (calculated as the ratio between the absolute coronary flow in the LAD and the mass subtended by the vessel, expressed in mL/min/g), but not resting, was significantly lower in the AS group (1.9 [1.5–2.5] ml/min/g vs 2.3 [2–3.1] ml/min/g p=0.036).

Conclusions

In patients with severe aortic stenosis and non-obstructive coronary artery disease, with the progression of LVH, the compensatory mechanism of increased resting flow maintains an adequate perfusion at rest, but not during hyperemia (Figure 2). As consequence, both CFR and MRR are significantly impaired.

Funding Acknowledgement

Type of funding sources: None.

Impact of aortic regurgitation on long-term outcomes in heart failure with preserved ejection fraction

Background

Aortic Regurgitation (AR) may aggravate the clinical course in patients with heart failure and preserved ejection fraction (HFpEF) by increasing filling pressures and triggering LV remodelling.

Objective

To assess AR's prevalence and long-term prognostic implications in patients with HFpEF.

Methods

The study population consisted of 458 consecutive patients (age 77.5±9.2 y, 57.9% females) hospitalized with de novo or worsened HFpEF. Patients with more than moderate aortic and/or mitral valve disease were excluded. Data on cardiovascular death, HF re-hospitalization and their composite (MACE) were collected.

Results

Out of 309 (67.5%) patients with any AR, 156 (34.0%) and 153 (33.5%) had mild-AR and moderate-AR, respectively. The remaining 149 (32.5%) individuals had no-AR. Patients with versus without AR were significantly older with larger LV and LA volumes and a higher prevalence of diastolic dysfunction (all p<0.05). During a median follow-up of 33±25 months, a total of 114 patients (24.9%) died from cardiovascular causes, 126 patients (27.5%) were re-hospitalized for HF, while 272 (59.4%) had the composite endpoint (MACE). In multivariable Cox regression analysis, any AR emerged as an only independent predictor of MACE (HR=1.90, 95% CI 1.26–2.87, p=0.002). Mild-AR and Moderate AR increased the risk of MACE by 77% and 92%, respectively, compared to the No-AR (Figure).

Conclusions

In patients with HFpEF, mild-to-moderate AR is highly prevalent, and it seems to identify individuals with worse long-term outcomes. This suggests that even mild AR should be considered a high-risk prognostic marker in patients with HFpEF.

Funding Acknowledgement

Type of funding sources: None.

Outcomes benefit in asymptomatic patients with moderate aortic valve stenosis followed up in heart valve clinics

Background

The management of patients with asymptomatic moderate aortic stenosis (AS), particularly the follow-up and the choice between early intervention vs watchful waiting, remains debated. A progressively increasing number of patients with valvular heart disease (VHD) were diagnosed and followed in an ambulatory setting with a dedicated cardiologist and cardiac imaging specialist: the Heart Valve Clinics (HVC). However, the number of patients with VHD is that high, that these patients are also followed by routine cardiac care consultations (standard-of-care).

Purpose

To determine the benefit of a HVC approach and outcomes compared to standard-of-care for patients with moderate asymptomatic AS.

Methods

From November 2014 a HVC environment was introduced at our Cardiovascular Center, to follow patients with moderate and severe VHD by an imaging and valve specialist. Patients who received at least one visit in the Ambulatory HVC were included in a prospective registry. All consecutive patients with aortic valve velocity max>3 cm/sec diagnosed with 2-D echocardiography according to the ESC Guidelines were included in this study. Exclusion criteria included more than moderate aortic regurgitation and prior aortic valve replacement (AVR). Natural history, need for AVR, and survival of patients with baseline moderate AS were assessed at follow up. Cox proportional hazard model, Kaplan-Meier survival curves and propensity score matching where used to assess the HVC approach effect on the mortality.

Results

A total of 2130 patients were included (1879 in the standard-of-care group and 251 in the Ambulatory HVC group). 1187 (55.7%) were male, and the mean (SD) age was 77.2±12.2 years. A total of 919 patients (43.1%) had severe AS (aortic valve area <1.0 cm2). Mean clinical follow-up was 1.2±2.4 years. A total of 822 patients (38.6%) died during the follow up and 114 patients (55.6%) underwent AVR during the study period. After using 1:1, nearest neighbour, without replacement propensity score matching, baseline characteristics between the two groups were balanced. The introduction of Ambulatory HVC was associated with a reduction of adjusted all-cause mortality compared to the standard-of-care group (HR=0.53, 95% CI 0.35–0.82, p=0.004) (Figure1). At multivariable analysis, the Ambulatory HVC pathway was a significant predictor of reduced all-cause of death (HR=0.46, 95% CI 0.33–0.65, p<0.001), together with younger age and higher GFR, independently of AVA, tricuspid regurgitation gradient, LVEF and chronic obstructive pulmonary disease.

Conclusions

Patients with moderate AS followed up in HVC had lower rate of all-cause of death compared to the standard-of-care group. The Ambulatory HVC was a significant predictor of reduced all-cause of death and was associated with more efficient patient management and lower mortality. Dedicated HVC have the potential to improve patient care and clinical outcomes.

Funding Acknowledgement

Type of funding sources: None.

Performance of non-invasive myocardial work to predict the first hospitalization for de novo heart failure with preserved ejection fraction (HFpEF)

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Dr. Paolisso, Dr. Esposito, Dr. Fabbricatore are supported by a research grant from the CardioPaTh PhD Program of University of Naples Federico II

Background

Non-invasive myocardial work (MW) is a validated index of left ventricular (LV) systolic performance, incorporating afterload and myocardial metabolism. The role of MW in predicting the first hospitalization for de novo heart failure with preserved ejection fraction (HFpEF) is still unknown.

Purpose

To investigate the diagnostic performance of MW to predict the first de novo HFpEF hospitalization in ambulatory individuals with preserved LVEF.

Methods

Twenty-nine patients with trans-thoracic echocardiography performed at least 6 months before the first HFpEF hospitalization were compared with 29 matched controls. MW was derived as the area of pressure-strain loop using speckle-tracking and brachial artery blood pressure. Global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE) were collected. First HFpEF hospitalization and its combination with cardiovascular death (MACE) and all-cause of death (MAE) were assessed.

Results

At baseline, future HFpEF patients showed lower GWI, GCW, GWE and higher GWW than controls (all p < 0.05).  At admission versus baseline, GWE significantly decreased, and GWW increased in the HFpEF group (p < 0.05), whereas no significant difference was observed in the controls over time. GWW, with a cut-off of 170 mmHg%, showed the largest AUC to predict first HFpEF hospitalization (AUC = 0.80, 95% CI 0.69–0.91, p < 0.001), MACE (AUC = 0.80, 95% CI 0.66–0.90, p < 0.001) and MAE (AUC = 0.79, 95% CI 0.62–0.88, p = 0.001). GWW > 170 mmHg% was associated with a 4-fold increase of MACE (HR = 4.5, 95% CI 1.59–13.12, p = 0.005) and a 3-fold higher risk of MAE (HR = 2.9, 95% CI 1.24–6.6, p = 0.014).

Conclusions

In ambulatory patients with preserved LVEF and risk factors, GWW showed high accuracy to predict the first HFpEF hospitalization and its combination with mortality. The GWW routine assessment may be clinically helpful in patients with dyspnea. Abstract Figure 1: Serial changes of LARs, LV GLS  Abstract Figure 2:Kaplan–Meier survival curves fo

Determination of cerebral water content by magnetic resonance imaging after small volume infusion of 18% hypertonic saline solution in a patient with refractory intracranial hypertension

Hypertonic saline solution (HSS) has been investigated in the treatment of intracranial hypertension (ICH) in a limited number of studies, usually after failure of conventional treatment. HSS, used in concentrations that vary from 3% to 23.4%, seems to be effective in reducing refractory ICH and to be devoid of adverse effects. We treated a patient with refractory ICH with a small-volume infusion of 18% HSS, and performed magnetic resonance imaging (MRI) before and after HSS infusion. MRI showed a marked reduction in cerebral water content 1 h after the infusion. To our knowledge, this is the first MRI study in a patient with brain injury to evaluate the effect of HSS on brain water content. Further studies are necessary to test HSS efficacy and to identify, through MRI or computed tomography (CT) scan imaging, a subgroup of patients with brain injury who would be best treated with HSS.

Three-dimensional model of the extracellular domain of the type 4a metabotropic glutamate receptor: new insights into the activation process

Metabotropic glutamate receptors (mGluRs) belong to the family 3 of G-protein-coupled receptors. On these proteins, agonist binding on the extracellular domain leads to conformational changes in the 7-transmembrane domains required for G-protein activation. To elucidate the structural features that might be responsible for such an activation mechanism, we have generated models of the amino terminal domain (ATD) of type 4 mGluR (mGlu4R). The fold recognition search allowed the identification of three hits with a low sequence identity, but with high secondary structure conservation: leucine isoleucine valine-binding protein (LIVBP) and leucine-binding protein (LBP) as already known, and acetamide-binding protein (AmiC). These proteins are characterized by a bilobate structure in an open state for LIVBP/LBP and a closed state for AmiC, with ligand binding in the cleft. Models for both open and closed forms of mGlu4R ATD have been generated. ACPT-I (1-aminocyclopentane 1,3,4-tricarboxylic acid), a selective agonist, has been docked in the two models. In the open form, ACPT-I is only bound to lobe I through interactions with Lys74, Arg78, Ser159, and Thr182. In the closed form, ACPT-I is trapped between both lobes with additional binding to Tyr230, Asp312, Ser313, and Lys317 from lobe II. These results support the hypothesis that mGluR agonists bind a closed form of the ATDs, suggesting that such a conformation of the binding domain corresponds to the active conformation.

Pharmacological characterization of the rat metabotropic glutamate receptor type 8a revealed strong similarities and slight differences with the type 4a receptor

In the brain, group-III metabotropic glutamate (mGlu) receptors mGlu(4), mGlu(7) and mGlu(8) receptors play a critical role in controlling the release process at many glutamatergic synapses. The pharmacological profile of mGlu(4) receptor has been studied extensively, allowing us to propose a pharmacophore model for this receptor subtype. Surprisingly, the activity of only a few compounds have been reported on mGlu(7) and mGlu(8) receptors. In order to identify new possibilities for the design of selective compounds able to discriminate between the members of the group-III mGlu receptors, we have undertaken a complete pharmacological characterization of mGlu(8) receptor and compared it with that of mGlu(4) receptor, using the same expression system, and the same read out. The activities of 32 different molecules revealed that these two mGlu receptors subtypes share a similar pharmacological profile. Only small differences were noticed in addition to that previously reported with S-carboxyglutamate (S-Gla) being a partial agonist at mGlu(4) receptor and a full antagonist at mGlu(8) receptor. These include: a slightly higher relative potency of the agonists 1S,3R and 1S,3S-aminocyclopentane-1,3-dicarboxylic acid (ACPD), S-4-carboxyphenylglycine (S-4CPG) and S-4-carboxy-3-hydroxyphenylglycine (S-4C3HPG), and a slightly higher potency of the antagonists 2-aminobicyclo[3.1.0]hexane-2, 6-dicarboxylic acid (LY354740) and RS-alpha-methyl-4-phosphonophenylglycine (MPPG) on mGlu(8) receptor. When superimposed on the mGlu(4) receptor pharmacophore model, these molecules revealed three regions that may be different between the ligand binding sites of mGlu(8) and mGlu(4) receptors.

New perspectives for the development of selective metabotropic glutamate receptor ligands

The metabotropic glutamate receptors are GTP-binding-protein (G-protein) coupled receptors that play important roles in regulating the activity of many synapses in the central nervous system. As such, these receptors are involved in a wide number of physiological and pathological processes. Within the last few years, new potent and selective agonists and antagonists as well as radioligands acting on these receptors have been developed. Molecular modeling studies revealed the structural features of the glutamate binding site, and will be useful for the design of more selective and potent ligands. More interestingly, recent data revealed new regulatory sites on the receptor protein, able either to decrease or potentiate the action of the endogenous ligand. No doubt that in the near future a multitude of new tools to modulate the activity of these receptors will be discovered, enabling the identification of the possible therapeutic applications for these new neuroactive molecules.

Comparative effect of L-CCG-I, DCG-IV and gamma-carboxy-L-glutamate on all cloned metabotropic glutamate receptor subtypes

In a previous study we reported that the addition of a carboxylic group to the mGlu receptor agonist aminocyclopentane-1,3-dicarboxylate (ACPD) changes its properties from agonist to antagonist at both mGlu1 and mGlu2 receptors, and resulted in an increase in affinity at mGlu4 receptors, with isomers being either agonists or antagonists. In the present study, the effect of gamma-carboxy-L-glutamic acid (Gla) and (2S,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV), two carboxylic derivatives of non-selective agonists, were examined on all cloned mGlu receptors. We found that this additional carboxylic group on glutamate prevents its interaction with group-I mGlu receptors and generates a potent group-II antagonist (K(B) = 55 microM on mGlu2). At group-III mGlu receptors, Gla was found to be either an antagonist (mGlu7 and mGlu8 receptors) or a partial agonist (mGlu4 and mGlu6 receptors). We show here that L-CCG-I is a general mGlu receptor agonist activating all cloned receptors. We also confirm that DCG-IV, which corresponds to L-CCG-I with an additional carboxylic group, is a selective group-II agonist. However, this additional COOH group changes the properties of L-CCG-I from an agonist to an antagonist at all group-III receptors, making this compound one of the most potent group-III mGlu receptor antagonist known so far. These observations will be useful for the development of more potent and selective mGlu receptor agonists and antagonists.