Sabbah, Michael S.

Objectives: Peripheral arterial disease is a significant cause of morbidity and mortality. The goal of this study was to develop a novel treatment to promote angiogenesis. Platelets have been previously implicated in angiogenic events; however, platelet activation rather than presence of growth factors has been associated with new blood vessel formation. This study evaluated exosomes purified from activated platelets to determine their potential in promoting angiogenesis both in vitro and in vivo. Methods & Results: Under Current Good Manufacturing Practices, conditioned medium processed from apheresis platelet cultures yielded a purified exosome product (PEP) enriched for CD63, CD9 and Alix. In vitro, PEP drove HUVEC proliferation, migration, and vascular tube formation. Proteomic evaluation showed Flk1 (VEGFR2) was one of the key angiogenic proteins in PEP. HUVECs treated with Flk1 antibody neutralized PEP (anti-Flk1-PEP) showed reduced vascular tube formation compared to PEP. To evaluate in vivo angiogenesis, a rodent model of hindlimb ischemia was treated with sustained release PEP embedded in fibrin glue (PEP/TISSEEL) with blood flow evaluated by SPY angiography at 28 days post-treatment. Animals treated with PEP/TISSEEL showed improved blood flow with significant difference (p<0.001) as compared to sham, TISSEEL, and anti-Flk1-PEP/TISSEEL. Muscle tissue stained with α smooth muscle actin showed a significant increase (p<0.001) in vascular area in PEP/TISSEEL treated animals compared to TISSEEL alone. To further evaluate clinical translatability, a rabbit ear ischemia wound model was then treated with PEP/TISSEEL. Rabbit ears showed accelerated wound healing and restored blood flow on SPY angiography. Histologic evaluation of vascular area showed a significant increase in vascular area (p<0.05) compared to sham and TISSEEL alone animals. Conclusions: Exosome driven donation of Flk1 here promoted angiogenic events and was successfully translated into healing outcomes in the setting of two animal models of peripheral ischemia. This novel insight into biotherapy achievable pro-angiogenesis establishes a clinical-grade off-the-shelf exosome technology for the treatment of peripheral vascular disease.

Abstract Aims In heart failure (HF), pulmonary venous hypertension (PVH) produces pulmonary hypertension (PH) with remodeling of pulmonary veins (PV) and arteries (PA). In a porcine PVH model, we performed proteomic-based bioinformatics to investigate unique pathophysiologic mechanisms mediating PA and PV remodeling. Methods and results Large PV were banded (PVH, n = 10) or not (Sham, n = 9) in piglets. At sacrifice, PV and PA were perfusion labelled for vessel-specific histology and proteomics. The PA and PV were separately sampled with laser-capture micro-dissection for mass spectrometry. Pulmonary vascular resistance [Wood Units; 8.6 (95% confidence interval: 6.3, 12.3) vs. 2.0 (1.7, 2.3)] and PA [19.9 (standard error of mean, 1.1) vs. 10.3 (1.1)] and PV [14.2 (1.2) vs. 7.6 (1.1)] wall thickness/external diameter (%) were increased in PVH (P &lt; 0.05 for all). Similar numbers of proteins were identified in PA (2093) and PV (2085) with 94% overlap, but biological processes differed. There were more differentially expressed proteins (287 vs. 161), altered canonical pathways (17 vs. 3), and predicted upstream regulators (PUSR; 22 vs. 6) in PV than PA. In PA and PV, bioinformatics indicated activation of the integrated stress response and mammalian target of rapamycin signalling with dysregulated growth. In PV, there was also activation of Rho/Rho-kinase signalling with decreased actin cytoskeletal signalling and altered tight and adherens junctions, ephrin B, and caveolae-mediated endocytosis signalling; all indicating disrupted endothelial barrier function. Indeed, protein biomarkers and the top PUSR in PV (transforming growth factor-beta) suggested endothelial to mesenchymal transition in PV. Findings were similar in human autopsy specimens. Conclusion These findings provide new therapeutic targets to oppose pulmonary vascular remodeling in HF-related PH.

Abstract Background Bioprosthetic tricuspid valve stenosis (TS) is an uncommon and frequently under-diagnosed condition. Although the resulting right heart failure symptoms are well-known, the associated thrombogenic potential is under-recognized. Case summary A 44-year-old woman with bioprosthetic tricuspid valve (TV) replacement in 2001 was referred for urgent consultation due to acute worsening of dyspnoea and severe swelling and pain in her left arm and neck. She was diagnosed with atrial fibrillation 6 months before the presentation and was found to have right atrial (RA) thrombus with pulmonary embolism and extensive retrograde venous extension 1 month prior. Review of studies done at her local institution revealed 10 mmHg mean gradient (MG) across the bioprosthetic TV that was only reported as mild–moderate TS. Echocardiography done at our instruction confirmed suspicion of severe TS with calcified immobile leaflets. Computed tomography showed persistent RA thrombus and therefore surgical replacement of the TV was undertaken. Subsequently, patient’s dyspnoea rapidly improved. Discussion Progressive dyspnoea and symptoms of right heart failure in a patient with a history of bioprosthetic TV replacement should be investigated for prosthetic valve dysfunction. Due to its rarity, TS diagnosis can be overlooked on routine echocardiography. In our patient, despite a measured MG of 10 mmHg, the presence of critical TS was not initially recognized. As TS is associated with increased thrombogenic potential and given the rare occurrence of in situ RA thrombosis, physicians must have a high index of suspicion for TS in the appropriate clinical context.

Abstract Aims Cardiac power is a measure of cardiac performance that incorporates both pressure and flow components. Prior studies have shown that cardiac power predicts outcomes in patients with reduced left ventricular (LV) ejection fraction (EF). We sought to evaluate the prognostic significance of peak exercise cardiac power and power reserve in patients with normal EF. Methods and results We performed a retrospective analysis in 24 885 patients (age 59 ± 13 years, 45% females) with EF ≥50% and no significant valve disease or right ventricular dysfunction, undergoing exercise stress echocardiography between 2004 and 2018. Cardiac power and power reserve (developed power with stress) were normalized to LV mass and expressed in W/100 g of LV myocardium. Endpoints at follow-up were all-cause mortality and diagnosis of heart failure (HF). Patients in the higher quartiles of power/mass (rest, peak stress, and power reserve) were younger and had higher peak blood pressure and heart rate, lower LV mass, and lower prevalence of comorbidities. During follow-up [median 3.9 (0.6–8.3) years], 929 patients died. After adjusting for age, sex, metabolic equivalents (METs) achieved, ischaemia/infarction on stress test results, medication, and comorbidities, peak stress power/mass was independently associated with mortality [adjusted hazard ratio (HR), highest vs. lowest quartile, 0.5, 95% confidence interval (CI) 0.4–0.6, P &lt; 0.001] and HF at follow-up [adjusted HR, highest vs. lowest quartile, 0.4, 95% CI (0.3, 0.5), P &lt; 0.001]. Power reserve showed similar results. Conclusion The assessment of cardiac power during exercise stress echocardiography in patients with normal EF provides valuable prognostic information, in addition to stress test findings on inducible myocardial ischaemia and exercise capacity.

Background: Comorbidity-driven microvascular inflammation is posited as a unifying pathophysiologic mechanism for heart failure with preserved ejection fraction (HFpEF). Obesity is proinflammatory and common in HFpEF. We hypothesized that unique obesity-inflammation HFpEF phenotypes exist and are associated with differences in clinical features, fibrosis biomarkers, and functional performance. Methods: Patients (n=301) from 3 HFpEF clinical trials were studied. Unsupervised machine learning (hierarchical clustering) with obese status and 13 inflammatory biomarkers as input variables was performed. Associations of clusters with HFpEF severity and fibrosis biomarkers (PIIINP [procollagen III N-terminal peptide], CITP [C-telopeptide for type I collagen], IGFBP7 [insulin-like growth factor-binding protein-7], and GAL-3 [galectin-3]) were assessed. Results: Hierarchical clustering revealed 3 phenotypes: pan-inflammatory (n=129; 64% obese), noninflammatory (n=83; 55% obese), and obese high CRP (C-reactive protein; n=89; 98% obese). The pan-inflammatory phenotype had more comorbidities and heart failure hospitalizations; higher left atrial volume, NT-proBNP (N-terminal pro-B-type natriuretic peptide), and fibrosis biomarkers; and lower glomerular filtration rate, peak oxygen consumption, 6-minute walk distance, and active hours/day ( P <0.05 for all). The noninflammatory phenotype had the most favorable values for all measures. The obese high CRP phenotype resembled the noninflammatory phenotype except for isolated elevation of CRP and lower functional performance. Hierarchical cluster assignment was independent of CRP genotype combinations that alter CRP levels and more biologically plausible than other clustering approaches. Multiple traditional analytic techniques confirmed and extended the hierarchical clustering findings. Conclusions: Unique obesity-inflammation phenotypes exist in HFpEF and are associated with differences in comorbidity burden, HFpEF severity, and fibrosis. These data support comorbidity-driven microvascular inflammation as a pathophysiologic mechanism for many but not all HFpEF patients.

Background: The role of coronary microvascular disease and its impact on functional and energetic reserve in heart failure with preserved ejection fraction (HFpEF) remains unclear. We hypothesized that in response to submaximal pharmacologic stress (dobutamine), patients with HFpEF have impairment in left ventricular (LV) myocardial mechanical (external work [EW]), energetic (myocardial O 2 consumption [MVO 2 ]), and myocardial blood flow (MBF) reserve. We further assessed whether coupling of MBF to EW is impaired in HFpEF and associated with compensatory increases or pathological decreases in myocardial O 2 extraction. Lastly, we assessed whether coupling of MVO 2 to EW (mechanical efficiency) was impaired in HFpEF. Methods and Results: In prospectively enrolled patients with HFpEF (n=19) and age/sex-matched healthy controls (n=19), we performed 11 C-acetate positron emission tomography assessing MVO 2 and MBF at rest and during dobutamine infusion. EW was calculated as stroke volume (echo)×end-systolic pressure×heart rate. At rest, compared with controls, patients with HFpEF had higher LV EW, MVO 2 , and MBF. With dobutamine, LV EW, MVO 2 , and MBF increased in both HFpEF and controls; however, the magnitude of increases was significantly smaller in HFpEF. In both groups, MBF increased in relation to EW, but in HFpEF, the slope of the relationship was significantly smaller than in controls. Myocardial O 2 extraction was increased in HFpEF. Mechanical efficiency was similar in HFpEF and controls. In a post hoc analysis, HFpEF patients with LV hypertrophy (n=10) had significant reductions in LV mechanical efficiency relative to controls. Conclusions: In HFpEF during submaximal dobutamine stress, there is myocardial mechanical-, energetic- and flow-reserve dysfunction with impaired coupling of blood flow to demand and slight increases in myocardial O 2 extraction. These findings provide evidence that coronary microvascular dysfunction is present in HFpEF, limits O 2 supply relative to demand, and is associated with reserve dysfunction.

Background: Mitral stenosis frequently coexists in patients with severe aortic stenosis. Mitral stenosis severity evaluation is challenging in the setting of combined aortic stenosis and mitral stenosis because of hemodynamic interactions between the 2 valve lesions. The impact of aortic valve replacement (AVR) for severe aortic stenosis on mitral stenosis is unknown. This study aimed to assess the effect of AVR on mitral stenosis hemodynamics and the clinical outcomes of patients with severe aortic stenosis with and without mitral stenosis. Methods: We retrospectively investigated patients who underwent surgical AVR or transcatheter AVR for severe aortic stenosis from 2008 to 2015. Mean transmitral gradient by Doppler echocardiography ≥4 mm Hg was identified as mitral stenosis; patients were then stratified according to mitral valve area (MVA, by continuity equation) as >2.0 cm 2 or ≤2.0 cm 2 . MVA before and after AVR in patients with mitral stenosis were evaluated. Clinical outcomes of patients with and without mitral stenosis were compared using 1:2 matching for age, sex, left ventricular ejection fraction, method of AVR (surgical AVR versus transcatheter AVR) and year of AVR. Results: Of 190 patients with severe aortic stenosis and mitral stenosis (age 76±9 years, 42% men), 184 were matched with 362 with severe aortic stenosis without mitral stenosis. Among all mitral stenosis patients, the mean MVA increased after AVR by 0.26±0.59 cm 2 (from 2.00±0.50 to 2.26±0.62 cm 2 , P <0.01). MVA increased in 105 (55%) and remained unchanged in 34 (18%). Indexed stroke volume ≤45 mL/m 2 (odds ratio [OR] 2.40; 95% CI, 1.15–5.01; P =0.020) and transcatheter AVR (OR, 2.36; 95% CI, 1.17–4.77; P =0.017) were independently associated with increase in MVA. Of 107 with significant mitral stenosis (MVA ≤2.0 cm 2 ), MVA increased to >2.0 cm 2 after AVR in 52 (49%, pseudo mitral stenosis) and remained ≤2.0 cm 2 in 55 (51%, true mitral stenosis). During follow-up of median 2.9 (0.7–4.9) years, true mitral stenosis was an independent predictor of all-cause mortality (adjusted hazard ratio, 1.88; 95% CI, 1.20–2.94; P <0.01). Conclusions: MVA improved after AVR in nearly half of patients with severe aortic stenosis and mitral stenosis. MVA remained ≤2.0 cm 2 (true mitral stenosis) in nearly half of patients with severe aortic stenosis and significant mitral stenosis; this was associated with worse survival among patients undergoing AVR for severe aortic stenosis.