Background:
Repolarization alternans, defined as period-2 oscillation in the repolarization phase of the action potentials, provides a mechanistic link between cellular dynamics and ventricular fibrillation (VF). Theoretically, higher-order periodicities (e.g., periods 4, 6, 8,...) are expected but have minimal experimental evidence.
Methods:
We studied explanted human hearts obtained from recipients of heart transplantation at the time of surgery. Optical mapping of the transmembrane potential was performed after staining the hearts with voltage-sensitive fluorescent dyes. Hearts were stimulated at an increasing rate until VF was induced. Signals recorded from the right ventricle endocardial surface prior to induction of VF and in the presence of 1:1 conduction were processed using the Principal Component Analysis and a combinatorial algorithm to detect and quantify higher-order dynamics. Results were correlated to the underlying electrophysiological characteristics as quantified by restitution curves and conduction velocity.
Results:
A prominent and statistically significant global 1:4 peak (corresponding to period-4 dynamics) was seen in three of the six studied hearts. Local (pixel-wise) analysis revealed the spatially heterogeneous distribution of periods 4, 6, and 8, with the regional presence of periods greater than two in all the hearts. There was no significant correlation between the underlying restitution properties and the period of each pixel.
Discussion:
We present evidence of higher-order periodicities and the co-existence of such regions with stable non-chaotic areas in ex-vivo human hearts. We infer from the independence of the period to the underlying restitution properties that the oscillation of the excitation-contraction coupling and calcium cycling mechanisms is the primary mechanism of higher-order dynamics. These higher-order regions may act as niduses of instability that can degenerate into chaotic fibrillation and may provide targets for substrate-based ablation of VF.
Background: Aortic valve (AV) calcification preferentially occurs on the fibrosa side while the ventricularis side remains relatively unaffected. Here, we tested the hypothesis that side-dependent activation of bone morphogenic protein (BMP) pathway in the endothelium of the ventricularis and fibrosa is associated with human AV calcification.
Methods and Results: Human calcified AVs obtained from AV replacement surgeries and non-calcified AVs from heart transplantations were used for immunohistochemical studies. We found SMAD-1/5/8 phosphorylation (a canonical BMP pathway) was higher in the calcified fibrosa than the non-calcified fibrosa while SMAD-2/3 phosphorylation (a canonical TGFβ pathway) did not show any difference. Interestingly, we found that BMP-2/4/6 expression was significantly higher on the ventricularis endothelium compared to the fibrosa in both calcified and non-calcified AV cusps; however, BMP antagonists (crossvienless-2/BMPER and noggin) expression was significantly higher on the ventricularis endothelium compared to the fibrosa in both disease states. Moreover, significant expression of inhibitory SMAD-6 expression was found only in the non-calcified ventricularis endothelium.
Conclusions: SMAD-1/5/8 is preferentially activated in the calcified fibrosa endothelium of human AVs and it correlates with low expression of BMP antagonists and inhibitory SMAD6. These results suggest a dominant role of BMP antagonists in the side-dependent calcification of human AVs.
Background: Medicaid insurance in Georgia provides limited reimbursement for heart transplant (HT) and left ventricular assist devices (LVAD). We examined whether insurance type affects eligibility for and survival after receipt of HT or LVAD.
Methods and Results: We retrospectively identified patients evaluated for HT/LVAD from 2012 to 2016. We used multivariable logistic and Cox proportional hazards regression to examine the association of insurance type on treatment eligibility and 1-year survival. Of 569 patients evaluated, 282 (49.6%) had private, 222 (39.0%) had Medicare, and 65 (11.4%) had Medicaid insurance. Patients with Medicaid were younger, more likely to be Black, with fewer medical comorbidities. In adjusted models, Medicare and Medicaid insurance predicted lower odds of eligibility for HT, but did not affect survival after HT. Among those ineligible for HT, Medicaid patients were less likely to receive destination therapy (DT) LVAD (adj OR 0.08, 95% CI 0.01-0.66; P =.02) and had increased risk of death (adj HR = 2.03, 95% CI 1.13-3.63; P =.01).
Conclusions: Despite younger age and fewer comorbidities, patients with Medicaid insurance are less likely to receive DT LVAD and have an increased risk of death once deemed ineligible for HT. Medicaid patients in Georgia need improved access to DT LVAD.
BACKGROUND: Repolarization alternans, defined as period-2 oscillation in the repolarization phase of the action potentials, is one of the cornerstones of cardiac electrophysiology as it provides a mechanistic link between cellular dynamics and ventricular fibrillation (VF). Theoretically, higher-order periodicities (e.g., period-4, period-8,…) are expected but have very limited experimental evidence. METHODS: We studied explanted human hearts, obtained from the recipients of heart transplantation at the time of surgery, using optical mapping technique with transmembrane voltage-sensitive fluorescent dyes. The hearts were stimulated at an increasing rate until VF was induced. The signals recorded from the right ventricle endocardial surface just before the induction of VF and in the presence of 1:1 conduction were processed using the Principal Component Analysis and a combinatorial algorithm to detect and quantify higher-order dynamics. RESULTS: A prominent and statistically significant 1:4 peak (corresponding to period-4 dynamics) was seen in three of the six studied hearts. Local analysis revealed the spatiotemporal distribution of higher-order periods. Period-4 was localized to temporally stable islands. Higher-order oscillations (period-5, 6, and 8) were transient and primarily occurred in arcs parallel to the activation isochrones. DISCUSSION: We present evidence of higher-order periodicities and the co-existence of such regions with stable non-chaotic areas in ex-vivo human hearts before VF induction. This result is consistent with the period-doubling route to chaos as a possible mechanism of VF initiation, which complements the concordant to discordant alternans mechanism. The presence of higher-order regions may act as niduses of instability that can degenerate into chaotic fibrillation.
Aims: Outflow graft obstruction is a poorly described complication following left ventricular assist device (LVAD) surgery. We sought to define the incidence of LVAD outflow graft obstruction and assess clinical outcomes with a percutaneous treatment strategy. Methods and results: From January 2012 to October 2020, 322 patients with LVAD were managed at our institution. Patients with LVAD outflow graft obstruction were identified by cardiac computed tomography with angiography and invasive haemodynamic assessment and were subsequently treated with percutaneous intervention. Poisson regression was used to analyse time-dependent differences in the incidence of LVAD outflow graft obstruction. Kaplan–Meier analysis was used to estimate survival. Twenty patients (6.2%) developed haemodynamically significant LVAD outflow graft obstruction at a rate of 0.03 events per patient-year. Outflow graft obstruction presented a median of 33 (26–49) months after surgery. Patients presented with low estimated LVAD pump flow (95%), heart failure (90%), or both (85%), and 59% developed cardiogenic shock prior to intervention. The most common aetiology identified by cardiac computed tomography with angiography was external compression of the outflow graft (78%). On presentation, the median peak gradient in the outflow graft was 78 (64–100) mmHg. Outflow graft stenting was 100% successful with no in-hospital mortality, and it reduced the peak outflow graft gradient to 10 (2–17) mmHg (P < 0.001). Outflow graft stenting was durable with two patients (10%) requiring a repeat procedure over a median follow-up of 13 (7–20) months and did not impact survival. Conclusions: Left ventricular assist device outflow graft obstruction is a relatively common and underappreciated cause of recurrent heart failure and LVAD dysfunction. Outflow graft stenting can be achieved with low morbidity and provides a long-term solution to this complication.
Objectives:
We investigated sex-based differences in eligibility for and outcomes after receipt of advanced heart failure (HF) therapies.
Background:
Although women are more likely to die from HF than men, registry data suggest that women are less likely to receive heart transplant (HT) or left ventricular assist device (LVAD) for largely unknown reasons.
Methods:
We performed a single-center, retrospective cohort study of patients evaluated for advanced HF therapies from 2012 to 2016. Logistic regression was used to determine the association of sex with eligibility for HT/LVAD. Competing risks and Kaplan-Meier analysis were used to examine survival.
Results:
Of 569 patients (31% women) evaluated, 223 (39.2%) were listed for HT and 81 (14.2%) received destination (DT) LVAD. Women were less likely to be listed for HT (adjusted odds ratio [OR] 0.36, 95% confidence interval [CI] 0.21 – 0.61; P<0.0001), based on allosensitization (P<0.0001) and obesity (P=0.02). Women were more likely to receive DT LVAD (adjusted OR 2.29, 95% CI 1.23 – 4.29; P=0.01). Survival was similar between men and women regardless of whether they received HT, DT LVAD, or were ineligible for therapy.
Conclusion:
Women are less likely to be HT candidates, but more likely to receive DT LVAD.
The 2018 Revised United Network for Organ Sharing Heart Allocation System (HAS) was proposed to reclassify status 1A candidates into groups of decreasing acuity; however, it does not take into account factors such as body mass index (BMI) and blood group which influence waitlist (WL) outcomes. We sought to validate patient prioritization in the new HAS at our center. We retrospectively evaluated patients listed for heart transplantation (n = 214) at Emory University Hospital from 2011 to 2017. Patients were reclassified into the 6-tier HAS. Multistate modeling and competing risk analysis were used to compare outcomes of transplantation and WL death/deterioration between new tiers. Additionally, a stratified sensitivity analysis by BMI and blood group was performed. Compared with tier 4 patients, there was progressively increasing hazard of WL death/deterioration in tier 3 (HR: 2.52, 95% CI: 1.37-4.63, P =.003) and tier 2 (HR: 5.03, 95% CI: 1.99-12.70, P <.001), without a difference in transplantation outcome. When stratified by BMI and blood group, this hierarchical association was not valid in patients with BMI ≥30 kg/m2 and non-O blood groups in our cohort. Therefore, the 2018 HAS accurately prioritizes the sickest patients in our cohort. Factors such as BMI and blood group influence this relationship and iterate that the system can be further refined.
Human dilated cardiomyopathy (DCM) is characterized by congestive heart failure and altered myocardial gene expression. Epigenetic changes, including DNA methylation, are implicated in the development of DCM but have not been studied extensively. Clinical human DCM and nonfailing control left ventricle samples were individually analyzed for DNA methylation and expressional changes. Expression microarrays were used to identify 393 overexpressed and 349 underexpressed genes in DCM (GEO accession number: GSE43435). Gene promoter microarrays were utilized for DNA methylation analysis, and the resulting data were analyzed by two different computational methods. In the first method, we utilized subtractive analysis of DNA methylation peak data to identify 158 gene promoters exhibiting DNA methylation changes that correlated with expression changes. In the second method, a two-stage approach combined a particle swarm optimization feature selection algorithm and a discriminant analysis via mixed integer programming classifier to identify differentially methylated gene promoters. This analysis identified 51 hypermethylated promoters and six hypomethylated promoters in DCM with 100% cross-validation accuracy in the group assignment. Generation of a composite list of genes identified by subtractive analysis and two-stage computation analysis revealed four genes that exhibited differential DNA methylation by both methods in addition to altered gene expression. Computationally identified genes (AURKB, BTNL9, CLDN5, and TK1) define a central set of differentially methylated gene promoters that are important in classifying DCM. These genes have no previously reported role in DCM. This study documents that rigorous computational analysis applied to microarray analysis of healthy and diseased human heart samples helps to define clinically relevant DNA methylation and expressional changes in DCM.