Michele Pilato

MicroRNA-29 in Aortic Dilation: Implications for Aneurysm Formation

Rationale: Aging represents a major risk factor for coronary artery disease and aortic aneurysm formation. MicroRNAs (miRs) have emerged as key regulators of biological processes, but their role in age-associated vascular pathologies is unknown. Objective: We aim to identify miRs in the vasculature that are regulated by age and play a role in age-induced vascular pathologies. Methods and Results: Expression profiling of aortic tissue of young versus old mice identified several age-associated miRs. Among the significantly regulated miRs, the increased expression of miR-29 family members was associated with a profound downregulation of numerous extracellular matrix (ECM) components in aortas of aged mice, suggesting that this miR family contributes to ECM loss, thereby sensitizing the aorta for aneurysm formation. Indeed, miR-29 expression was significantly induced in 2 experimental models for aortic dilation: angiotensin II-treated aged mice and genetically induced aneurysms in Fibulin-4R/R mice. More importantly, miR-29b levels were profoundly increased in biopsies of human thoracic aneurysms, obtained from patients with either bicuspid (n=79) or tricuspid aortic valves (n=30). Finally, LNA-modified antisense oligonucleotide-mediated silencing of miR-29 induced ECM expression and inhibited angiotensin II-induced dilation of the aorta in mice. Conclusion: In conclusion, miR-29-mediated downregulation of ECM proteins may sensitize the aorta to the formation of aneurysms in advanced age. Inhibition of miR-29 in vivo abrogates aortic dilation in mice, suggesting that miR-29 may represent a novel molecular target to augment matrix synthesis and maintain vascular wall structural integrity.

MicroRNA-29 in aortic dilation: implications for aneurysm formation [Molecular Medicine]

Rationale: Aging represents a major risk factor for coronary artery disease and aortic aneurysm formation. MicroRNAs (miRs) have emerged as key regulators of biological processes, but their role in age-associated vascular pathologies is unknown. Objective: We aim to identify miRs in the vasculature that are regulated by age and play a role in age-induced vascular pathologies. Methods and Results: Expression profiling of aortic tissue of young versus old mice identified several age-associated miRs. Among the significantly regulated miRs, the increased expression of miR-29 family members was associated with a profound downregulation of numerous extracellular matrix (ECM) components in aortas of aged mice, suggesting that this miR family contributes to ECM loss, thereby sensitizing the aorta for aneurysm formation. Indeed, miR-29 expression was significantly induced in 2 experimental models for aortic dilation: angiotensin II-treated aged mice and genetically induced aneurysms in Fibulin-4R/R mice. More importantly, miR-29b levels were profoundly increased in biopsies of human thoracic aneurysms, obtained from patients with either bicuspid (n=79) or tricuspid aortic valves (n=30). Finally, LNA-modified antisense oligonucleotide-mediated silencing of miR-29 induced ECM expression and inhibited angiotensin II-induced dilation of the aorta in mice. Conclusion: In conclusion, miR-29-mediated downregulation of ECM proteins may sensitize the aorta to the formation of aneurysms in advanced age. Inhibition of miR-29 in vivo abrogates aortic dilation in mice, suggesting that miR-29 may represent a novel molecular target to augment matrix synthesis and maintain vascular wall structural integrity.

Difference in hemodynamic and wall stress of ascending thoracic aortic aneurysms with bicuspid and tricuspid aortic valve

The aortic dissection (AoD) of an ascending thoracic aortic aneurysm (ATAA) initiates when the hemodynamic loads exerted on the aneurysmal wall overcome the adhesive forces holding the elastic layers together. Parallel coupled, two-way fluid-structure interaction (FSI) analyses were performed on patient-specific ATAAs obtained from patients with either bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV) to evaluate hemodynamic predictors and wall stresses imparting aneurysm enlargement and AoD. Results showed a left-handed circumferential flow with slower-moving helical pattern in the aneurysms center for BAV ATAAs whereas a slight deviation of the blood flow toward the anterolateral region of the ascending aorta was observed for TAV ATAAs. Blood pressure and wall shear stress were found key hemodynamic predictors of aneurysm dilatation, and their dissimilarities are likely associated to the morphological anatomy of the aortic valve. We also observed discontinues, wall stresses on aneurysmal aorta, which was modeled as a composite with two elastic layers (i.e., inhomogeneity of vessel structural organization). This stress distribution was caused by differences on elastic material properties of aortic layers. Wall stress distribution suggests AoD just above sinotubular junction. Moreover, abnormal flow and lower elastic material properties that are likely intrinsic in BAV individuals render the aneurysm susceptible to the initiation of AoD.

Primary Graft Failure After Heart Transplantation: The Importance of Donor Pharmacological Management

BACKGROUND Primary graft failure (PGF) remains the strongest determinant of perioperative mortality after heart transplantation (HT). Donor management may play an important role in the incidence of PGF. MATERIALS AND METHODS Multivariate analysis was used to identify PGF determinants after HT. Donor and recipient data were analyzed together with preharvest management information and perioperative results. PGF was defined as the need for mechanical circulatory support immediately post-HT. RESULTS Isolated HT was performed in 54 consecutive patients from January 2006 to June 2009. PGF occurred in 11 (20%) patients. Upon univariate analysis, preoperative mean pulmonary arterial pressure was significantly higher among patients developing PGF (P=.02). The donors for PGF patients had more often been managed with high inotropic support (dopamine>10 microg/kg/min and/or alpha agonists>0.06 microg/kg/min; P=.008). In contrast, death for head trauma was more common among donors for patients who did not develop PGF (P=.02). In-hospital mortality was 13% (7/54); 71% of these deceased patients displayed PGF (5/7). Upon multivariate analysis, preharvest high donor inotropic support was the strongest determinant of PGF (P=.01, odds ratio [OR]=7.5). Donor death due to head trauma showed a protective effect against PGF (P=.03, OR=0.1). CONCLUSION PGF remains a lethal perioperative complication despite modern tools for prompt cardiac mechanical assistance. As a result of the organ shortage, many centers accept marginal hearts assuming that donor hemodynamic management shows a reduced impact on PGF. We suggest a timely evaluation of the hazards for PGF whenever high inotropic support is used, especially among donors dying for causes other than head trauma.

The role of 1.5T cardiac MRI in the diagnosis, prognosis and management of pulmonary arterial hypertension

Cardiovascular magnetic imaging is a noninvasive, three dimensional tomographic technique that allows for a detailed morphology of the cardiac chambers, the accurate quantification of right ventricle volumes, myocardial mass, and transvalvular flow. It can also determine whether right ventricular diastolic function is impaired through pulmonary hypertension. The aim of this article is to review the main kinetic, morphological and functional changes of the right ventricle that can occur in patients affected by pulmonary arterial hypertension (PAH) and to assess how the MRI findings can influence the prognosis, and guide the decision-making strategy. In those cases in which MRI shows a significant cardiac diastolic dysfunction, the prognosis is predictive of pharmacological treatment failure, and mortality. This leaves double lung-heart transplantation as the only therapeutic option. The coexistence of PAH and left ventricle impairment causes worse right ventricle function, leads to a poor prognosis, and may change the therapeutic strategies (for example, PAH associated with left ventricle dysfunction may require a double lung-heart transplant).

Anti-correlation between longevity gene SirT1 and Notch signaling in ascending aorta biopsies from patients with bicuspid aortic valve disease

About 1–2% of the population present with bicuspid aortic valves (BAV), a defect of the aortic valve resulting in the formation of two leaflets instead of three. This disease leads to an abnormal aorta, altered in strength and size, which in turn is a high risk factor for potentially lethal events such as aortic dissection and aneurysm formation. BAV is inheritable, with a demonstrated association with Notch1, a member of the Notch intercellular signaling pathway that is implicated in various cardiovascular disorders. Sirtuin 1 (SirT1) is a protein deacetylase of the sirtuin family, whose activation appears beneficial for cardiac diseases. A recent study has shown that SirT1 can limit Notch signaling in model systems of vascular growth. If a concomitant dysregulation in Notch and SirT1 signaling pathways can cause the phenotypic form of human BAV is unknown. To address this issue, we analyzed human ascending aorta biopsies from BAV and control patients obtained at the time of cardiac surgery. RNA and proteins were extracted from formalin-fixed and paraffin-embedded specimens, and quantitative real-time PCR and immunoblotting were used to determine the expression of sirtuins and members of the Notch family of proteins. We found a significant increase in SirT1 expression that correlates with a decreased expression of the Notch signaling effectors detected. We put forward the idea that an altered interaction between SirT1 and Notch signaling could participate in BAV pathogenesis and that these molecules could be used as potential clinical markers.

Donor pharmacological hemodynamic support is associated with primary graft failure in human heart transplantation

The aim of this study was to test the impact of donor and recipient characteristics on the development of primary graft failure (PGF) after heart transplantation (HT) by focusing on the donors inotropic support. Heart donors and matched recipients data were prospectively collected. Univariate and multivariate analyses were used to determine independent predictors for PGF and peri-operative mortality. The donors high inotrope requirement was defined as sustained need for dopamine exceeding 10 microg/kg/min and/or alpha agonists exceeding 0.06 microg/kg/min. PGF instead was defined as need for immediate post-HT mechanical circulatory support. Since 2006, we have performed 37 HTs. PGF occurred in six patients (16.2%). Although four patients (66.6%) were weaned off circulatory support, two of them (33.3%) died on mechanical assistance. Total in-hospital mortality was 10.8% (4/37). Upon multivariate analysis, pre-harvesting donor high inotrope dosage was the major determinant for PGF (P=0.03, OR=10.8). Given the organ shortage, many centers accepted marginal hearts assuming the donors pre-harvest hemodynamic managing has a reduced impact on PGF development. As PGF remains the most lethal postoperative complication, the hazards should be carefully considered when using pre-harvesting high inotrope infusion rates.

Prediction of right ventricular failure after ventricular assist device implant: systematic review and meta-analysis of observational studies

Right ventricular failure (RVF) after left ventricular assist device (LVAD) implantation is associated with increased morbidity and mortality, but the identification of LVAD candidates at risk for RVF remains challenging. We undertook a systematic review and meta‐analysis of observational studies of risk factors associated with RVF after LVAD implant. Thirty‐six studies published between 1 January 1995 and 30 April 2015, comprising 995 RVF patients out of a pooled final population of 4428 patients, were identified. Meta‐analysed prevalence of post‐LVAD RVF was 35%. A need for mechanical ventilation [odds ratio (OR) 2.99], or continuous renal replacement therapy (CRRT; OR 4.61, area under the curve 0.78, specificity 0.91) were the clinical variables with the highest effect size (ES) in predicting RVF. International normalized ratio [INR; standardized mean difference (SMD) 0.49] and N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) (SMD 0.52) were the biochemical markers that best discriminated between RVF and No‐RVF populations, though NT‐proBNP was highly heterogeneous. Right ventricular stroke work index (RVSWI) and central venous pressure (CVP) (SMD −0.58 and 0.47, respectively) were the haemodynamic measures with the highest ES in identifying patients at risk of post‐LVAD RVF; CVP was particularly useful in risk stratifying patients undergoing continuous‐flow LVAD implant (SMD 0.59, P < 0.001, I2 = 20.9%). Finally, pre‐implant moderate to severe right ventricular (RV) dysfunction, as assessed qualitatively (OR 2.82), or a greater RV/LV diameter ratio (SMD 0.51) were the standard echocardiographic measurements with the highest ES in comparing RVF with No‐RVF patients. Longitudinal systolic strain of the RV free wall had the highest ES (SMD 0.73) but also the greatest heterogeneity (I2 = 74%) and was thus only marginally significant (P = 0.05). Patients on ventilatory support or CRRT are at high risk for post‐LVAD RVF, similarly to patients with slightly increased INR, high NT‐proBNP or leukocytosis. High CVP, low RVSWI, an enlarged right ventricle with concomitant low RV strain also identify patients at higher risk.

Iatrogenic hypoglycemia secondary to tight glucose control is an independent determinant for mortality and cardiac morbidity

OBJECTIVE Evaluation of the effects of tight glycemia control in critically ill patients should include temporal as well as punctual glycemia data. METHODS Insulin drip was used to target intensive care unit (ICU) glucose levels between 80 and 126 mg dl⁻¹ in a consecutive series of adult cardiac surgery patients. ICU hourly glycemia was prospectively recorded. Glycemia standard deviation, hyperglycemia index (area under the curve for glycemia>126 mg dl⁻¹ divided by total hours in ICU), and hypoglycemic episodes were recorded and analyzed, together with outcomes. RESULTS A total of 596 patients were included. Hypoglycemia occurred in 21% of the patients. In-hospital mortality was 2.6%. There was a univariate correlation between mortality and glycemia standard deviation, and hypoglycemia occurrence. At multivariate analysis, hypoglycemia was a determinant for mortality (p=0.002; odds ratio (OR)=20.0), respiratory failure (p=0.0001; OR=1.4), requirement of a tracheostomy (p=0.0001; OR=21.6), and hemodynamic instability requiring intra-aortic balloon pump (IABP) (p=0.01; OR=1.5). To clarify the determinants of hypoglycemia, a second multivariate model was built. Diabetes (p=0.0001; OR=23) and chronic renal failure (p=0.01; OR=25) were the sole determinants for hypoglycemia occurrence. CONCLUSION Iatrogenic hypoglycemia secondary to ICU tight glycemia control correlates with hospital mortality, respiratory, and cardiac morbidity in patients undergoing cardiac surgery. ICU hyperglycemia index and glycemia temporal variability have no independent correlation with outcomes. Higher glycemia targets should be advised in the perioperative management of patients with diabetes and renal failure, as both conditions independently increase the risk of hypoglycemia occurrence.

Extracorporeal membrane oxygenation for graft failure after heart transplantation: A multidisciplinary approach to maximize weaning rate

Objectives Primary graft failure (PGF) after heart transplantation is a detrimental complication, and carries high morbidity and mortality. The aim of this study was to analyze the results of our multidisciplinary approach in supporting patients affected with PGF after heart transplantation. Methods Out of 114 consecutive patients receiving orthotopic heart transplantation between January 2006 and July 2013, 18 (15.7%) developed PGF requiring veno-arterial extracorporeal membrane oxygenator (VA-ECMO) support. Fourteen patients were male and the mean age was 49 ± 11 years. General principles in treating the patients were based on a low dose of adrenaline (0.05 mic/kg per min) infusion; femoral intra-aortic balloon pump (13 of the 18 patients); low dose of vasoconstrictors; careful fluid balance; daily echocardiographic transesophageal monitoring. Results Mean graft recipient pulmonary vascular resistance was 3.6 ± 3.2 WU. Five patients had absolute contraindication to IABP placement. The mean left ventricle ejection fraction pre-VA-ECMO was 18.4% ± 10.2%. The mean VA-ECMO and IABP support times were 6.7 ± 3.2 and 9.2 ± 7.6 days, respectively. Mean VA-ECMO flow was 4164 ± 679 l/min. The mean left ventricle ejection fraction increased to 43.4% ± 17.7% at the end of support. Weaning and discharge rates in patients treated with VA-ECMO+IABP were 84% and 53%, respectively. Causes of death were primarily end-stage organ failure. Conclusions A multidisciplinary evaluation of ECMO patients done by intensivists, cardiologists, and surgeons may influence weaning and survival rate. Our approach seems to be a safe and reproducible strategy for avoiding left ventricle distension and fluid overload, and for detecting complications that negatively affect outcomes.