Faculty Bibliography

PURPOSE OF REVIEW: Sleep disorders represent a significant comorbidity in the heart failure population, and there is mounting evidence that treatment of sleep disorders such as obstructive sleep apnea can significantly improve cardiac function. However, the link between these two disorders is still not entirely clear. RECENT FINDINGS: Recently, a novel neurohormonal pathway has been elucidated involving signaling molecules now collectively known as the orexins, which have been implicated in regulating autonomic function during sleep/wake cycles. Further evidence has mounted that orexin signaling is deeply perturbed in the setting of sleep disorders, and furthermore that abnormal orexin signaling may be implicated in the pathology of heart failure. The orexin signaling pathway represents an enticing novel target for both the treatment of sleep disorders as well as heart failure, and may represent one facet of the "missing link" between these two prevalent and often comorbid diseases.

Ventricular arrhythmias are common after left ventricular assist device implantation. Malposition of the inflow cannula is one of the few etiologies with a mechanically correctable defect. We present a case of intractable ventricular tachycardia that resolved after surgical repositioning of a HeartMate II inflow cannula. The diagnosis and management of this case demonstrate the utility of imaging studies for detecting inflow cannula malposition and the efficacy of inflow cannula repositioning for treatment.

BACKGROUND: This study evaluated current trends in incidence and outcomes of left ventricular assist device (LVAD)-related thromboembolic (LVAD-TE) and LVAD malfunction (LVAD-M) complications among heart transplant (HT) candidates supported with continuous-flow LVADs. LVAD-TE and LVAD-M are potentially catastrophic complications that may require status upgrade on the HT waiting list. An increased incidence of device thrombosis has been recently observed; however, whether similar trends of LVAD-TE and LVAD-M are observed on the HT waiting list and their effect on outcomes is unknown. METHODS: We analyzed 3,821 HT candidates on continuous-flow LVADs who were registered on the United States waiting list from 2008 to 2014. We evaluated the incidence of LVAD-TE and LVAD-M as well as survival before and after HT. RESULTS: LVAD-TE occurred in 249 patients (6.5%) and LVAD-M in 210 patients (5.5%). The incidence of LVAD-TE was highest in regions 1, 2, and 9, whereas LVAD-M was highest in regions 9, 1, and 7. The incidence of LVAD-TE and LVAD-M increased after 2011 from 0.04 to 0.10 and from 0.03 to 0.08 events per patient-year (p < 0.0001 for both comparisons). Survival on the waiting list at 2 years was lower in candidates with LVAD-TE (45% vs 72%, p < 0.0001) and LVAD-M (56% vs 71%, p = 0.003) compared with candidates without complications. Post-HT survival was similar between patients with and without LVAD-TE and LVAD-M (p > 0.43 for both outcomes). In patients with LVAD-TE, mortality risk was highest among candidates managed conservatively (hazard ratio, 8.07; p < 0.0001), whereas patients who underwent HT only (hazard ratio, 0.10; p < 0.0001) had the lowest mortality risk and similar to that of patients without LVAD-TE (p = 0.34). CONCLUSIONS: The incidence of LVAD-TE and LVAD-M on the United States waiting list has increased since 2011, with significant regional variation. LVAD-TE and LVAD-M have a detrimental effect on waiting list survival and transplant candidacy. In candidates who develop an LVAD-TE, a conservative approach, without LVAD exchange or HT, carries the highest risk of death. These results should be considered in the ongoing efforts to optimize the allocation of donor hearts.

BACKGROUND: The genetic determinants of heart failure (HF) and response to medical therapy remain unknown. We hypothesized that identifying genetic variants of HF that associate with response to medical therapy would elucidate the genetic basis of cardiac function. OBJECTIVES: This study sought to identify genetic variations associated with response to HF therapy. METHODS: This study compared extremes of response to medical therapy in 866 HF patients using a genome-wide approach that informed the systems-based design of a customized single nucleotide variant array. The effect of genotype on gene expression was measured using allele-specific luciferase reporter assays. Candidate gene transcription-deficient mice underwent echocardiography and treadmill exercise. The ability of the target gene agonist to rescue mice from chemically-induced HF was assessed with echocardiography. RESULTS: Of 866 HF patients, 136 had an ejection fraction improvement of 20% attributed to resynchronization (n = 83), revascularization (n = 7), tachycardia resolution (n = 2), alcohol cessation (n = 1), or medications (n = 43). Those with the minor allele for rs7767652, upstream of hypocretin (orexin) receptor-2 (HCRTR2), were less likely to have improved left ventricular function (odds ratio: 0.40 per minor allele; p = 3.29 x 10(-5)). In a replication cohort of 798 patients, those with a minor allele for rs7767652 had a lower prevalence of ejection fraction >35% (odds ratio: 0.769 per minor allele; p = 0.021). In an HF model, HCRTR2-deficient mice exhibited poorer cardiac function, worse treadmill exercise capacity, and greater myocardial scarring. Orexin, an HCRTR2 agonist, rescued function in this HF mouse model. CONCLUSIONS: A systems approach identified a novel genetic contribution to human HF and a promising therapeutic agent efficacious in an HF model.

BACKGROUND: Re-endothelialization is delayed after drug-eluting stent (DES) implantation. In this setting, neointima is more prone to become lipid laden and develop neoatherosclerosis (NA), potentially increasing plaque vulnerability. METHODS AND RESULTS: Optical coherence tomography and near-infrared spectroscopy with intravascular ultrasound were used to characterize NA in 65 (51 DES and 14 bare-metal stents) consecutive symptomatic patients with in-stent restenosis. Median duration poststent implantation was 33 months. Optical coherence tomography-verified NA was observed in 40 stents with in-stent restenosis (62%), was more prevalent in DES than bare-metal stents (68% versus 36%; P=0.02), and demonstrated significantly higher prevalence of thin-cap neoatheroma (47% versus 7%; P=0.01) in DES. Near-infrared spectroscopy assessment demonstrated that the total lipid core burden index (34 [interquartile range, 12-92] versus 9 [interquartile range, 0-32]; P<0.001) and the density of lipid core burden index (lipid core burden index/4 mm, 144 [interquartile range, 60-285] versus 26 [interquartile range, 0-86]; P<0.001) were higher in DES compared with bare-metal stents. Topographically, NA was classified as I (thin-cap NA), II (thick-cap NA), and III (peri-strut NA). Type I thin-cap neoatheroma was more common in DES (20% versus 3%; P=0.01) and in areas of the stented segment without significant in-stent restenosis (71%). Periprocedural myocardial infarction occurred only in DES (11 versus 0; P=0.05), of which 6 (55%) could be attributed to segments with >70% in-stent restenosis. By logistic regression, prior DES was the only independent predictor of both NA (odds ratio, 7.0; 95% confidence interval, 1.7-27; P=0.006) and periprocedural myocardial infarction (odds ratio, 1.8; 95% confidence interval, 1.1-2.4; P=0.05). CONCLUSIONS: In-stent thin-cap neoatheroma is more prevalent, is distributed more diffusely across the stented segment, and is associated with increased periprocedural myocardial infarction in DES compared with bare-metal stents. These findings support NA as a mechanism for late DES failure.

Microscale and nanoscale structures can spatially pattern endothelial cells (ECs) into parallel-aligned organization, mimicking their cellular alignment in blood vessels exposed to laminar shear stress. However, the effects of spatial patterning on the function and global transcriptome of ECs are incompletely characterized. We used both parallel-aligned micropatterned and nanopatterned biomaterials to evaluate the effects of spatial patterning on the phenotype of ECs, based on gene expression profiling, functional characterization of monocyte adhesion, and quantification of cellular morphology. We demonstrate that both micropatterned and aligned nanofibrillar biomaterials could effectively guide EC organization along the direction of the micropatterned channels or nanofibrils, respectively. The ability of ECs to sense spatial patterning cues were abrogated in the presence of cytoskeletal disruption agents. Moreover, both micropatterned and aligned nanofibrillar substrates promoted an athero-resistant EC phenotype by reducing endothelial adhesiveness for monocytes and platelets, as well as by downregulating the expression of adhesion proteins and chemokines. We further found that micropatterned ECs have a transcriptional signature that is unique from non-patterned ECs, as well as from ECs aligned by shear stress. These findings highlight the importance of spatial patterning cues in guiding EC organization and function, which may have clinical relevance in the development of vascular grafts that promote patency.

Spurred by large-scale public and private efforts as well as technological developments, the last few years have seen a major leap forward in our understanding of the genetic basis of cardiovascular disease. This revolution is in its infancy and will continue to alter the medical landscape for years to come. There is a need within the general cardiology community to develop a better understanding about how these developments may alter routine clinical care. In this review, we will provide an overview of the current state of genetics as pertains to rare cardiovascular diseases and then review advances in the discovery of the genetic basis of common disease with the potential for improved risk assessment and drug development. We will also outline a few recent examples of pharmacogenetic advances that are already starting to become a part of clinical management and finally discuss the promise as well as the challenges in using next-generation sequencing technologies to provide personalized cardiovascular care.