Daily Cardiology Research Analysis
Three impactful cardiology studies stood out: (1) macrotroponin markedly distorts sex-specific 99th percentile thresholds in a widely used hs-cTnI assay, with minimal impact in hs-cTnT, redefining diagnostic interpretation; (2) dephosphorylation of Connexin43 at serine-282 drives reperfusion arrhythmias via PP2A, offering a druggable mechanistic target; and (3) private equity acquisition of U.S. hospitals did not improve 30-day heart failure outcomes, with equity concerns for Black patients and
Summary
Three impactful cardiology studies stood out: (1) macrotroponin markedly distorts sex-specific 99th percentile thresholds in a widely used hs-cTnI assay, with minimal impact in hs-cTnT, redefining diagnostic interpretation; (2) dephosphorylation of Connexin43 at serine-282 drives reperfusion arrhythmias via PP2A, offering a druggable mechanistic target; and (3) private equity acquisition of U.S. hospitals did not improve 30-day heart failure outcomes, with equity concerns for Black patients and increased catheterization use.
Research Themes
- Diagnostic biomarker reliability and assay interference
- Mechanistic arrhythmia biology and therapeutic targeting
- Health systems and equity in heart failure care
Selected Articles
1. Influence of Macrotroponin on the 99th Percentile Threshold in 2 High-Sensitivity Cardiac Troponin Assays.
In a healthy reference cohort, macrotroponin was present in most high-end hs‑cTnI samples (Siemens) but absent in hs‑cTnT (Roche). Excluding macrotroponin reduced sex-specific hs‑cTnI 99th percentiles by 4–5 fold (men 117→22 ng/L; women 37→9 ng/L). The authors propose the 99th/50th percentile ratio as a practical indicator of macrotroponin interference and call for prospective validation.
Impact: These results directly question current hs‑cTnI reference limits and highlight assay-specific interference that can misclassify myocardial injury. It provides an actionable metric (99th/50th ratio) and a roadmap for assay re-evaluation.
Clinical Implications: Laboratories should consider screening for macrotroponin in elevated hs‑cTnI (e.g., via IgG depletion or orthogonal assays), reassess sex-specific 99th percentiles, and interpret hs‑cTnI elevations cautiously when discordant with clinical context. The 99th/50th percentile ratio could flag assays with probable interference.
Key Findings
- Macrotroponin detected in 76% (67/88) of top Siemens hs‑cTnI samples but 0% (0/70) in Roche hs‑cTnT.
- Excluding macrotroponin lowered Siemens hs‑cTnI 99th percentiles: men 117→22 ng/L; women 37→9 ng/L.
- The Siemens 99th/50th percentile ratio dropped from 12–29× to 3–7×, approximating Roche ratios, suggesting a tool to detect interference.
Methodological Strengths
- Two orthogonal confirmation methods (IgG depletion and sucrose gradient) aligned with IFCC recommendations
- Large healthy reference cohort with sex-specific analysis and assay comparison
Limitations
- Macrotroponin testing was limited to the top 10% of cTn values; full-spectrum prevalence is unknown
- Analytical constraints prevented complete sucrose analysis for all Siemens samples; prospective clinical validation is lacking
Future Directions: Prospective multicenter studies should quantify macrotroponin prevalence across the full distribution, standardize screening workflows, and reassess assay-specific 99th percentiles; evaluate clinical decision thresholds using interference-aware algorithms.
BACKGROUND: Cardiac troponin (cTn) levels exceeding the 99th percentile upper reference limit and a rise/fall pattern are key for diagnosing myocardial injury and infarction. Macrotroponins, formed by patient anti-cTn antibodies targeting cTn, can cause persistently elevated cTn levels without ongoing myocardial injury. The frequency and impact of macrotroponin interference on cTn 99th percentiles are unclear. This study compares sex-specific 99th percentiles for 2 cTn assays, before and after excluding macrotroponin-positive samples, focusing on the top 10% of cTn levels. METHODS: We examined 1058 plasma samples from healthy individuals previously used for Danish cTn 99th percentiles. Following International Federation of Clinical Chemistry and Laboratory Medicine educational recommendations, macrotroponin presence was assessed in the top 10% cTn samples using immunoglobulin G (IgG) depletion screening and a reference sucrose gradient, confirming macrotroponin when both methods concurred. Due to analytical dilution constraints, [the highest] 88 of 135 Siemens Atellica high-sensitivity cTnI (hs-cTnI) samples were analyzed with both methods. All 106 Roche hs-cTnT samples were negative using IgG depletion, and sucrose analysis was limited to the highest 70 samples. RESULTS: Macrotroponin was found in 76% (67/88) of Siemens samples but in none of the Roche samples (0/70). Excluding macrotroponin-affected samples lowered the Siemens 99th percentiles from 117 ng/L to 22 ng/L in men and from 37 ng/L to 9 ng/L in women. The 99th/50th percentile ratio for Siemens decreased from 12- to 29-fold to 3- to 7-fold, approaching the Roche ratios. CONCLUSIONS: Macrotroponin significantly influenced the Siemens Atellica hs-cTnI 99th percentiles, suggesting important clinical implications that warrant further prospective studies. The 99th/50th percentile ratio may help evaluate macrotroponin interference in troponin assays.
2. A potential therapeutic target at Connexin 43 serine phosphorylation against ischaemia/reperfusion arrhythmia.
The study identifies Cx43 serine‑282 dephosphorylation as a causal driver of reperfusion arrhythmias. PP2A inhibition (LB100) restored Cx43 S282 phosphorylation and suppressed arrhythmias, while a Cx43 loop‑mimetic peptide (TAT‑HA‑L2) mitigated arrhythmogenicity, revealing a druggable Cx43 intramolecular interaction.
Impact: It provides mechanistic clarity linking Cx43 S282 dephosphorylation to conduction abnormalities and arrhythmogenesis, and demonstrates two intervention strategies, advancing translational anti-arrhythmic targets for reperfusion injury.
Clinical Implications: While preclinical, the data support therapeutic development aimed at preserving Cx43 phosphorylation or modulating PP2A/L2–CT interactions to prevent reperfusion arrhythmias during acute myocardial infarction care and revascularization.
Key Findings
- Ischaemia/reperfusion increased PP2A activity and reduced Cx43 S282 phosphorylation, with ventricular tachycardia/fibrillation in rats.
- Cx43‑S282A/+ mice exhibited spontaneous ventricular arrhythmias despite normal structure and function, indicating a causal role.
- LB100 (PP2A inhibitor) restored Cx43 S282 phosphorylation and reduced arrhythmias; a Cx43 L2-mimetic peptide (TAT‑HA‑L2) mitigated arrhythmogenicity and conduction abnormalities.
Methodological Strengths
- Convergent evidence from rat I/R model, genetic knock-in mice, pharmacologic inhibition, and peptide intervention
- Electrophysiological mapping corroborating mechanistic effects on conduction and hemichannel behavior
Limitations
- Preclinical animal and cellular models; absence of human validation
- Potential off-target effects and safety concerns with PP2A inhibition not addressed
Future Directions: Validate the Cx43 S282 axis in large-animal and human tissues; develop selective modulators of PP2A–Cx43 interactions; assess safety/efficacy in reperfusion settings.
BACKGROUND AND PURPOSE: Dephosphorylation of several phosphor residues in connexin 43 (Cx43) is critically involved in ischaemia/reperfusion (I/R) arrhythmias. Here, we sought to identify constitutive Cx43-serine 282 (S282) dephosphorylation as an independent and targetable substrate to delineate reperfusion arrhythmogenesis. EXPERIMENTAL APPROACH: Reperfusion arrhythmias were induced by rat I/R (15/45 min), identified in heterozygous knock-in mice with S282 to alanine (Cx43-S282A/+) and rescued by LB100, a specific protein phosphatase 2A (PP2A) inhibitor, via surface electrocardiogram and epicardial mapping detections. TAT-HA-L2, a mimic of Cx43-cytoplasmic-loop domain (L2), was assessed in mitigating Cx43-S282 dephosphorylation-associated arrhythmogenicity. KEY RESULTS: Upon I/R, rats exeperienced myocardium injury, ventricular tachycardia/fibrillation, increased PP2A activity and Cx43-S282 hypophosphorylation, whereas Cx43-S282A/+ mice had spontaneous ventricular arrhythmias with normal cardiac function/morphology. LB100 significantly attenuated these arrhythmias by restoring PP2A-C and Cx43-S282 phosphorylation. Slow and irregular electrical conduction, premature Ca CONCLUSIONS AND IMPLICATIONS: Cx43-S282 dephosphorylation can trigger reperfusion arrhythmias by impairing gap junction intercellular communication while favouring hemichannel permeability. An up-regulated intramolecular interaction between L2 and Cx43-carboxyl-terminus is associated with this arrhythmogenicity, providing a novel and targetable mechanism to preserve the heart from ischaemia/reperfusion arrhythmias.
3. Heart Failure Care and Outcomes After Private Equity Acquisition of U.S. Hospitals.
In a difference‑in‑differences analysis of Medicare heart failure admissions at 41 private equity–acquired vs 192 control hospitals (2012–2019), 30‑day mortality and revisit rates did not improve post‑acquisition, despite a lower clinical risk case mix. Transfers overall were unchanged, but transfers increased among Black patients, and cardiac catheterization use rose.
Impact: This policy-relevant study provides rigorous quasi-experimental evidence that private equity ownership did not improve short-term heart failure outcomes and may exacerbate disparities, informing regulators and health systems.
Clinical Implications: Health systems and payers should monitor HF quality metrics post-acquisition, scrutinize procedural utilization increases, and implement safeguards to prevent inequitable transfer patterns, especially for Black patients.
Key Findings
- No significant change in 30-day mortality (DiD +0.7 pp; 95% CI −0.4 to 1.8) or 30-day revisits (DiD −0.2 pp; 95% CI −0.9 to 0.5) after PE acquisition.
- Black patients experienced a significant increase in transfers out (DiD +7.1 pp; 95% CI 0.7–13.4), not seen in other racial groups.
- Cardiac catheterization rates increased (DiD +0.7 pp; 95% CI 0.1–1.2) at PE-acquired hospitals compared with controls.
Methodological Strengths
- Quasi-experimental difference-in-differences design with matched controls across 2012–2019
- National Medicare cohort and stratified analyses including race-specific effects
Limitations
- Observational design with potential residual confounding and unmeasured hospital-level changes
- Findings pertain to older Medicare patients; generalizability to other populations is uncertain
Future Directions: Investigate mechanisms behind utilization shifts and transfer patterns, evaluate long‑term outcomes and cost‑effectiveness, and test policy interventions to ensure equitable, value‑based HF care under new ownership structures.
BACKGROUND: Private equity firms have rapidly acquired U.S. hospitals and increasingly invested in cardiology over the past decade. However, little is known about how private equity acquisition of hospitals affects care and outcomes for patients with heart failure. OBJECTIVES: The purpose of this study was to evaluate whether clinical care and outcomes changed for patients with heart failure after the acquisition of U.S. hospitals by private equity firms compared with matched control hospitals. METHODS: This study identified U.S. hospitals acquired by private equity firms and matched control hospitals from 2012 through 2019. A quasiexperimental difference-in-differences analysis was used to evaluate changes in clinical outcomes, the case mix of admissions and transfers, as well as cardiac procedure utilization among Medicare fee-for-service beneficiaries aged 65 years or older with heart failure. RESULTS: There were 41 private equity-acquired hospitals and 192 matched control hospitals. After private equity acquisition of hospitals, there was no change in 30-day mortality rates (difference-in-differences [DiD] +0.7 percentage points [95% CI: -0.4 to 1.8]) or 30-day hospital revisit rates (DiD -0.2 percentage points [95% CI: -0.9 to 0.5]), despite a significant decrease in the clinical risk of patients with heart failure when compared with those at matched control (nonacquired) hospitals. Overall hospital transfer rates did not change, but Black patients were significantly more likely to be transferred out to another site after private equity acquisition (DiD +7.1 percentage points [95% CI: 0.7-13.4]), a change not observed across other racial groups. In addition, there was a significant increase in cardiac catheterization rates (DiD estimate, +0.7 percentage points [95% CI: 0.1-1.2]) among heart failure patients at private equity-acquired vs control hospitals. CONCLUSIONS: These findings suggest that private equity acquisitions of U.S. hospitals do not improve outcomes among older adults with heart failure, despite a decrease in the clinical risk of patients admitted to these sites.