Advanced heart failure patients supported with ambulatory inotropic therapy: What defines success of therapy?

OBJECTIVE: The objective of this study was to describe the profiles and outcomes of a cohort of advanced heart failure patients on ambulatory inotropic therapy (AIT). BACKGROUND: With the growing burden of patients with end-stage heart failure, AIT is an increasingly common short or long-term option, for use as bridge to heart transplant (BTT), bridge to ventricular assist device (BTVAD), bridge to decision regarding advanced therapies (BTD) or as palliative care. AIT may be preferred by some patients and physicians to facilitate hospital discharge. However, counseling patients on risks and benefits is critically important in the modern era of defibrillators, durable mechanical support and palliative care. METHODS: We retrospectively studied a cohort of 241 patients on AIT. End points included transplant, VAD implantation, weaning of inotropes, or death. The primary outcomes were survival on AIT and ability to reach intended goal if planned as BTT or BTVAD. We also evaluated recurrent heart failure hospitalizations, incidence of ventricular arrhythmias (VT/VF) and indwelling line infections. Unintended consequences of AIT, such reaching unintended end point (e.g. VAD implantation in BTT patient) or worse than expected outcome after LVAD or HT, were recorded. RESULTS: Mean age of the cohort was 60.7 ± 13.2 years, 71% male, with Class III-IV heart failure (56% non-ischemic). Average ejection fraction was 19.4 ± 10.2%, pre-AIT cardiac index was 1.5 ± 0.4 L/min/m2 and 24% had prior ventricular arrhythmias. Overall on-AIT 1-year survival was 83%. Hospitalizations occurred in 51.9% (125) of patients a total of 174 times for worsening heart failure, line complication or ventricular arrhythmia. In the BTT cohort, only 42% were transplanted by the end of follow-up, with a 14.8% risk of death or delisting for clinical deterioration. For the patients who were transplanted, 1-year post HT survival was 96.7%. In the BTVAD cohort, 1-year survival after LVAD was 90%, but with 61.7% of patients undergoing LVAD as INTERMACS 1-2. In the palliative care cohort, only 24.5% of patients had a formal palliative care consult prior to AIT. CONCLUSIONS: AIT is a strategy to discharge advanced heart failure patients from the hospital. It may be useful as bridge to transplant or ventricular assist device, but may be limited by complications such as hospitalizations, infections, and ventricular arrhythmias. Of particular note, it appears more challenging to bridge to transplant on AIT in the new allocation system. It is important to clarify the goals of AIT therapy upfront and continue to counsel patients on risks and benefits of the therapy itself and potential unintended consequences. Formalized, multi-disciplinary care planning is essential to clearly define individualized patient, as well as programmatic goals of AIT.

Electrocardiographic Findings in Female Professional Basketball Athletes.

Importance: Previous studies of professional basketball athletes have characterized manifestations of athletic remodeling by echocardiography and electrocardiography (ECG) in males and echocardiography in females. There is a paucity of female, basketball-specific ECG data. Objective: To generate reference range ECG data for female professional basketball athletes. Design, Setting, and Participants: This is a cross-sectional study of ECGs performed on female professional basketball athletes. The Women's National Basketball Association mandates annual preseason ECGs and echocardiograms for each athlete and has partnered with Columbia University Irving Medical Center to annually review these studies. Data for this study were collected during preseason ECG and echocardiography cardiac screening between April and May 2022. Data analysis was performed between February and July 2023. Exposure: Athlete ECGs and echocardiograms were sent to Columbia University Irving Medical Center for core lab analysis. Main Outcomes and Measures: Quantitative ECG variables were measured. ECG data were qualitatively analyzed for training-related and abnormal findings using the International Recommendations for Electrocardiographic Interpretation in Athletes. Findings from ECGs were compared with corresponding echocardiographic data. Results: There were a total of 173 athletes (mean [SD] age 26.5 [4.1] years; mean [SD] height, 183.4 [9.1] cm; mean [SD] body surface area, 2.0 [0.2] m2), including 129 Black athletes (74.5%) and 40 White athletes (23.1%). By international criteria, 136 athletes (78.6%) had training-related ECG changes and 8 athletes (4.6%) had abnormal ECG findings. Among athletes with at least 1 training-related ECG finding, left ventricular structural adaptations associated with athletic remodeling were present in 64 athletes (47.1%). Increased relative wall thickness, reflecting concentric left ventricular geometry, was more prevalent in athletes with the repolarization variant demonstrating convex ST elevation combined with T-wave inversions in leads V1 to V4 (6 of 12 athletes [50.0%]) than in athletes with early repolarization (5 of 42 athletes [11.9%]) (odds ratio, 7.40; 95% CI, 1.71-32.09; P = .01). Abnormal ECG findings included T-wave inversions (3 athletes [1.7%]), Q waves (2 athletes [1.2%]), prolonged QTc interval (2 athletes [1.2%]), and frequent premature ventricular contractions (1 athlete [0.6%]). Conclusions and Relevance: This cross-sectional study provides reference ECG data for elite female basketball athletes. International criteria-defined training-related findings were common, whereas abnormal ECG findings were rare in this athlete group. These reference data may assist basketball programs and health care professionals using ECGs in screening for female athletes and may be used as a stimulus for future female-specific ECG inquiries.

A membrane-associated phosphoswitch in Rad controls adrenergic regulation of cardiac calcium channels.

The ability to fight or flee from a threat relies on an acute adrenergic surge that augments cardiac output, which is dependent on increased cardiac contractility and heart rate. This cardiac response depends on ß-adrenergic-initiated reversal of the small RGK G protein Rad-mediated inhibition of voltage-gated calcium channels (CaV) acting through the Cavß subunit. Here, we investigate how Rad couples phosphorylation to augmented Ca2+ influx and increased cardiac contraction. We show that reversal required phosphorylation of Ser272 and Ser300 within Rad's polybasic, hydrophobic C-terminal domain (CTD). Phosphorylation of Ser25 and Ser38 in Rad's N-terminal domain (NTD) alone was ineffective. Phosphorylation of Ser272 and Ser300 or the addition of 4 Asp residues to the CTD reduced Rad's association with the negatively charged, cytoplasmic plasmalemmal surface and with CaVß, even in the absence of CaVα, measured here by FRET. Addition of a posttranslationally prenylated CAAX motif to Rad's C-terminus, which constitutively tethers Rad to the membrane, prevented the physiological and biochemical effects of both phosphorylation and Asp substitution. Thus, dissociation of Rad from the sarcolemma, and consequently from CaVß, is sufficient for sympathetic upregulation of Ca2+ currents.

Potassium Channels as Therapeutic Targets in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a devastating disease with high morbidity and mortality. Deleterious remodeling in the pulmonary arterial system leads to irreversible arterial constriction and elevated pulmonary arterial pressures, right heart failure, and eventually death. The difficulty in treating PAH stems in part from the complex nature of disease pathogenesis, with several signaling compounds known to be involved (e.g., endothelin-1, prostacyclins) which are indeed targets of PAH therapy. Over the last decade, potassium channelopathies were established as novel causes of PAH. More specifically, loss-of-function mutations in the KCNK3 gene that encodes the two-pore-domain potassium channel KCNK3 (or TASK-1) and loss-of-function mutations in the ABCC8 gene that encodes a key subunit, SUR1, of the ATP-sensitive potassium channel (KATP) were established as the first two potassium channelopathies in human cohorts with pulmonary arterial hypertension. Moreover, voltage-gated potassium channels (Kv) represent a third family of potassium channels with genetic changes observed in association with PAH. While other ion channel genes have since been reported in association with PAH, this review focuses on KCNK3, KATP, and Kv potassium channels as promising therapeutic targets in PAH, with recent experimental pharmacologic discoveries significantly advancing the field.

Loss-of-Function ABCC8 Mutations in Pulmonary Arterial Hypertension.

BACKGROUND: In pulmonary arterial hypertension (PAH), pathological changes in pulmonary arterioles progressively raise pulmonary artery pressure and increase pulmonary vascular resistance, leading to right heart failure and high mortality rates. Recently, the first potassium channelopathy in PAH, because of mutations in KCNK3, was identified as a genetic cause and pharmacological target. METHODS: Exome sequencing was performed to identify novel genes in a cohort of 99 pediatric and 134 adult-onset group I PAH patients. Novel rare variants in the gene identified were independently identified in a cohort of 680 adult-onset patients. Variants were expressed in COS cells and function assessed by patch-clamp and rubidium flux analysis. RESULTS: We identified a de novo novel heterozygous predicted deleterious missense variant c.G2873A (p.R958H) in ABCC8 in a child with idiopathic PAH. We then evaluated all individuals in the original and a second cohort for rare or novel variants in ABCC8 and identified 11 additional heterozygous predicted damaging ABCC8 variants. ABCC8 encodes SUR1 (sulfonylurea receptor 1)-a regulatory subunit of the ATP-sensitive potassium channel. We observed loss of ATP-sensitive potassium channel function for all ABCC8 variants evaluated and pharmacological rescue of all channel currents in vitro by the SUR1 activator, diazoxide. CONCLUSIONS: Novel and rare missense variants in ABCC8 are associated with PAH. Identified ABCC8 mutations decreased ATP-sensitive potassium channel function, which was pharmacologically recovered.

The Impact of Heterozygous KCNK3 Mutations Associated With Pulmonary Arterial Hypertension on Channel Function and Pharmacological Recovery.

BACKGROUND: Heterozygous loss of function mutations in the KCNK3 gene cause hereditary pulmonary arterial hypertension (PAH). KCNK3 encodes an acid-sensitive potassium channel, which contributes to the resting potential of human pulmonary artery smooth muscle cells. KCNK3 is widely expressed in the body, and dimerizes with other KCNK3 subunits, or the closely related, acid-sensitive KCNK9 channel. METHODS AND RESULTS: We engineered homomeric and heterodimeric mutant and nonmutant KCNK3 channels associated with PAH. Using whole-cell patch-clamp electrophysiology in human pulmonary artery smooth muscle and COS7 cell lines, we determined that homomeric and heterodimeric mutant channels in heterozygous KCNK3 conditions lead to mutation-specific severity of channel dysfunction. Both wildtype and mutant KCNK3 channels were activated by ONO-RS-082 (10 µmol/L), causing cell hyperpolarization. We observed robust gene expression of KCNK3 in healthy and familial PAH patient lungs, but no quantifiable expression of KCNK9, and demonstrated in functional studies that KCNK9 minimizes the impact of select KCNK3 mutations when the 2 channel subunits co-assemble. CONCLUSIONS: Heterozygous KCNK3 mutations in PAH lead to variable loss of channel function via distinct mechanisms. Homomeric and heterodimeric mutant KCNK3 channels represent novel therapeutic substrates in PAH. Pharmacological and pH-dependent activation of wildtype and mutant KCNK3 channels in pulmonary artery smooth muscle cells leads to membrane hyperpolarization. Co-assembly of KCNK3 with KCNK9 subunits may provide protection against KCNK3 loss of function in tissues where both KCNK9 and KCNK3 are expressed, contributing to the lung-specific phenotype observed clinically in patients with PAH because of KCNK3 mutations.

Characterization of KCNQ1 atrial fibrillation mutations reveals distinct dependence on KCNE1.

The I(Ks) potassium channel, critical to control of heart electrical activity, requires assembly of α (KCNQ1) and ß (KCNE1) subunits. Inherited mutations in either I(Ks) channel subunit are associated with cardiac arrhythmia syndromes. Two mutations (S140G and V141M) that cause familial atrial fibrillation (AF) are located on adjacent residues in the first membrane-spanning domain of KCNQ1, S1. These mutations impair the deactivation process, causing channels to appear constitutively open. Previous studies suggest that both mutant phenotypes require the presence of KCNE1. Here we found that despite the proximity of these two mutations in the primary protein structure, they display different functional dependence in the presence of KCNE1. In the absence of KCNE1, the S140G mutation, but not V141M, confers a pronounced slowing of channel deactivation and a hyperpolarizing shift in voltage-dependent activation. When coexpressed with KCNE1, both mutants deactivate significantly slower than wild-type KCNQ1/KCNE1 channels. The differential dependence on KCNE1 can be correlated with the physical proximity between these positions and KCNE1 as shown by disulfide cross-linking studies: V141C forms disulfide bonds with cysteine-substituted KCNE1 residues, whereas S140C does not. These results further our understanding of the structural relationship between KCNE1 and KCNQ1 subunits in the I(Ks) channel, and provide mechanisms for understanding the effects on channel deactivation underlying these two atrial fibrillation mutations.