Faculty Bibliography

BACKGROUND: The PGC-1alpha/PPAR axis has been proposed as a potential therapeutic target for several metabolic disorders. The aim was to evaluate the efficacy of the pan-PPAR agonist, bezafibrate, in tafazzin knockdown mice (TazKD), a mouse model of Barth syndrome that exhibits age-dependent dilated cardiomyopathy with left ventricular (LV) dysfunction. RESULTS: The effect of bezafibrate on cardiac function was evaluated by echocardiography in TazKD mice with or without beta-adrenergic stress. Adrenergic stress by chronic isoproterenol infusion exacerbates the cardiac phenotype in TazKD mice, significantly depressing LV systolic function by 4.5 months of age. Bezafibrate intake over 2 months substantially ameliorates the development of LV systolic dysfunction in isoproterenol-stressed TazKD mice. Without beta-adrenergic stress, TazKD mice develop dilated cardiomyopathy by 7 months of age. Prolonged treatment with suprapharmacological dose of bezafibrate (0.5% in rodent diet) over a 4-month period effectively prevented LV dilation in mice isoproterenol treatment. Bezafibrate increased mitochondrial biogenesis, however also promoted oxidative stress in cardiomyocytes. Surprisingly, improvement of systolic function in bezafibrate-treated mice was accompanied with simultaneous reduction of cardiolipin content and increase of monolysocardiolipin levels in cardiac muscle. CONCLUSIONS: Thus, we demonstrate that bezafibrate has a potent therapeutic effect on preventing cardiac dysfunction in a mouse model of Barth syndrome with obvious implications for treating the human disease. Additional studies are needed to assess the potential benefits of PPAR agonists in humans with Barth syndrome.

Cardiolipin is a specific mitochondrial phospholipid that has a high affinity for proteins and that stabilizes the assembly of supercomplexes involved in oxidative phosphorylation. We found that sequestration of cardiolipin in protein complexes is critical to protect it from degradation. The turnover of cardiolipin is slower by almost an order of magnitude than the turnover of other phospholipids. However, in subjects with Barth syndrome, cardiolipin is rapidly degraded via the intermediate monolyso-cardiolipin. Treatments that induce supercomplex assembly decrease the turnover of cardiolipin and the concentration of monolyso-cardiolipin, whereas dissociation of supercomplexes has the opposite effect. Our data suggest that cardiolipin is uniquely protected from normal lipid turnover by its association with proteins, but this association is compromised in subjects with Barth syndrome, leading cardiolipin to become unstable, which in turn causes the accumulation of monolyso-cardiolipin.

Anomalous aortic origin of the coronary artery (AAOCA) from the opposite sinus of Valsalva with an interarterial course has become a high-profile lesion as a result of its association with sudden cardiac death in otherwise young and healthy individuals. Despite our incomplete knowledge of its pathophysiology and natural history, surgical intervention is often recommended. Evidence now shows AAOCA to be relatively common, with lower than previously suspected rates of sudden cardiac death. Analysis of this information reveals that AAOCA is not always a surgical disease. Future multi-institutional studies will continue to define those subgroups best served by observation or surgery.

The mouse is the mammalian model of choice for investigating cardiovascular biology, given our ability to manipulate it by genetic, pharmacologic, mechanical, and environmental means. Imaging is an important approach to phenotyping both function and structure of cardiac and vascular components. This review details commonly used imaging approaches, with a focus on echocardiography and magnetic resonance imaging and brief overviews of other imaging modalities. We also briefly outline emerging imaging approaches but caution that reliability and validity data may be lacking. (c) 2016 by John Wiley & Sons, Inc.

BACKGROUND:Ebstein anomaly and tricuspid valve dysplasia are rare congenital tricuspid valve malformations associated with high perinatal mortality. The literature consists of small, single-center case series spanning several decades. We performed a multicenter study to assess the outcomes and factors associated with mortality after fetal diagnosis in the current era. METHODS AND RESULTS/RESULTS:Fetuses diagnosed with Ebstein anomaly and tricuspid valve dysplasia from 2005 to 2011 were included from 23 centers. The primary outcome was perinatal mortality, defined as fetal demise or death before neonatal discharge. Of 243 fetuses diagnosed at a mean gestational age of 27±6 weeks, there were 11 lost to follow-up (5%), 15 terminations (6%), and 41 demises (17%). In the live-born cohort of 176 live-born patients, 56 (32%) died before discharge, yielding an overall perinatal mortality of 45%. Independent predictors of mortality at the time of diagnosis were gestational age <32 weeks (odds ratio, 8.6; 95% confidence interval, 3.5-21.0; P<0.001), tricuspid valve annulus diameter z-score (odds ratio, 1.3; 95% confidence interval, 1.1-1.5; P<0.001), pulmonary regurgitation (odds ratio, 2.9; 95% confidence interval, 1.4-6.2; P<0.001), and a pericardial effusion (odds ratio, 2.5; 95% confidence interval, 1.1-6.0; P=0.04). Nonsurvivors were more likely to have pulmonary regurgitation at any gestational age (61% versus 34%; P<0.001), and lower gestational age and weight at birth (35 versus 37 weeks; 2.5 versus 3.0 kg; both P<0.001). CONCLUSION/CONCLUSIONS:In this large, contemporary series of fetuses with Ebstein anomaly and tricuspid valve dysplasia, perinatal mortality remained high. Fetuses with pulmonary regurgitation, indicating circular shunt physiology, are a high-risk cohort and may benefit from more innovative therapeutic approaches to improve survival.

Background: A recent multi-center study of perinatal outcome in fetuses with Ebstein anomaly or tricuspid valve dysplasia (EA/TVD) found that 1/3rd of live-born patients (pts) died prior to hospital discharge. The purpose of this study was to explore differences in postnatal management and the relationship to outcome. Methods: This 23-center, retrospective study included 243 fetuses with EA/TVD from 2005 to 2011. Neonatal procedure (NP) was defined as surgery or interventional catheterization (cath) prior to discharge. Associations between postnatal management and outcome at discharge were explored. Results: Of 176 live-born pts, 7 received comfort care only, 11 died <24 hrs of life, and 4 had insufficient data. Among 154 remaining pts, 38 (25%) did not survive to discharge. Pts who required ECMO at any point (n=18) had 83% mortality. More than half of pts (54%) did not have an NP, 34% had surgery, 8% had interventional cath, and 4% had both. The median age at 1st NP was 6 days (quartiles: 1-11). Survival did not differ between pts who had an NP and those who did not (70% vs. 80%; p=0.19) or between pts who had surgery and those who did not (68% vs. 80%; p=0.09). However, mortality differed by NP performed and whether pulmonary regurgitation, an indicator of high risk, was present prenatally (Figure). No pts with a right ventricular exclusion (RVE) died. Of 49 surviving neonates with >1 procedure, 28 (57%) were palliated with a shunt or RVE and 21 (43%) had a biventricular circulation. Thus, in total, 86 of 154 live-born pts (56%) survived with a biventricular circulation: 65 with medical management only and 21 with >1 NP. Conclusion: Among live-born pts diagnosed with EA/TVD in utero, a variety of postnatal management strategies were employed with overall poor outcomes. If surgery beyond PDA ligation is necessary, then RVE or other palliative procedure may need to be considered. A prospective, multi-center study utilizing a management algorithm would help elucidate the optimal strategy

Marfan syndrome (MFS) is an autosomal dominant disorder of connective tissue, caused by mutations of the microfibrillar protein fibrillin-1, that predisposes affected individuals to aortic aneurysm and rupture and is associated with increased TGFbeta signaling. TGFbeta is secreted from cells as a latent complex consisting of TGFbeta, the TGFbeta propeptide, and a molecule of latent TGFbeta binding protein (LTBP). Improper extracellular localization of the latent complex can alter active TGFbeta levels, and has been hypothesized as an explanation for enhanced TGFbeta signaling observed in MFS. We previously reported the absence of LTBP-3 in matrices lacking fibrillin-1, suggesting that perturbed TGFbeta signaling in MFS might be due to defective interaction of latent TGFbeta complexes containing LTBP-3 with mutant fibrillin-1 microfibrils. To test this hypothesis, we genetically suppressed Ltbp3 expression in a mouse model of progressively severe MFS. Here, we present evidence that MFS mice lacking LTBP-3 have improved survival, essentially no aneurysms, reduced disruption and fragmentation of medial elastic fibers, and decreased Smad2/3 and Erk1/2 activation in their aortas. These data suggest that, in MFS, improper localization of latent TGFbeta complexes composed of LTBP-3 and TGFbeta contributes to aortic disease progression.

Surgical repair of congenital ventricular septal defects (VSDs) in adults is quite rare. Most congenital VSDs are repaired in children. Of those adult patients diagnosed as having VSDs, many are not repaired due to irreversible pulmonary vascular disease. Repair in a patient with a VSD and fistula is even more uncommon. From a review of the literature, we found no other case reports with our unique combination of echocardiographic and surgical findings: a supracristal VSD, right and left sinus of Valsalva fistulas into the right ventricular outflow tract, and a pulmonary artery to pulmonary vein fistula in the context of an aseptic endocarditis lesion. We review the important aspects of anesthetic management in an adult with an intracardiac shunt. An adult patient with unrepaired congenital VSD may develop multiple fistulas as a consequence of endocarditis. This patient refused surgery until the progressive dyspnea was worsened by the endocarditis and the fistulas. At the time of surgery, his ventricular ejection fraction measured 47%, the ventricular chambers were enlarged, and the pulmonary to systemic flow ratio measured 2:1. He did well clinically after the VSD and fistulae repair.