Daily Cardiology Research Analysis
Three impactful cardiology studies stand out today: a mechanistic genetics paper links a noncoding enhancer variant near KCNB1 to familial ST-depression syndrome, potentially reframing arrhythmia genetics; a large binational cohort shows multiarterial grafting improves survival across all ejection fraction strata in CABG; and a cohort analysis after PCI highlights residual inflammatory risk—not residual LDL cholesterol—as the dominant driver of events under statin therapy.
Summary
Three impactful cardiology studies stand out today: a mechanistic genetics paper links a noncoding enhancer variant near KCNB1 to familial ST-depression syndrome, potentially reframing arrhythmia genetics; a large binational cohort shows multiarterial grafting improves survival across all ejection fraction strata in CABG; and a cohort analysis after PCI highlights residual inflammatory risk—not residual LDL cholesterol—as the dominant driver of events under statin therapy.
Research Themes
- Noncoding regulatory variants driving cardiac electrophysiology phenotypes
- Revascularization strategy (multiarterial grafting) and long-term survival
- Residual inflammatory risk vs cholesterol risk after PCI under statin therapy
Selected Articles
1. Gain-of-function enhancer variant near KCNB1 causes familial ST-depression syndrome.
Across 20 families (67 affected individuals), the authors identified a rare noncoding enhancer variant 18 kb downstream of KCNB1 that perfectly co-segregated with autosomal dominant ST-depression. The variant creates a MEF2-binding site, increases transcriptional activity, and regulates KCNB1 as confirmed by dCas9 perturbation and 4C assays, establishing KCNB1’s first implication in human cardiac electrophysiology and arrhythmogenesis.
Impact: This is a first-in-human demonstration that a gain-of-function noncoding enhancer variant can drive a familial ECG phenotype via KCNB1, reframing arrhythmia genetics beyond coding regions.
Clinical Implications: Genetic testing for noncoding regulatory variants near KCNB1 should be considered in familial ECG syndromes with ST-depression. Mechanistic insights open avenues for precision diagnosis and potential targeted modulation of enhancer–promoter interactions.
Key Findings
- Identified a rare noncoding enhancer variant 18 kb downstream of KCNB1 that perfectly co-segregates with FSTD across 20 families with full penetrance.
- The variant creates a de novo MEF2-binding site and enhances transcriptional activity; dCas9 activator/repressor assays implicate KCNB1 as the sole consistently regulated gene.
- Chromosome conformation capture (4C) confirmed physical interaction between the locus and the KCNB1 promoter in cardiomyocytes and human muscle tissue.
Methodological Strengths
- Combined linkage analysis, whole-genome sequencing, and multi-layer functional assays (luciferase, dCas9 perturbation, 4C).
- Demonstrated perfect co-segregation with full penetrance across 20 families.
Limitations
- Expression analysis in human endocardial tissue did not show differential expression, likely due to tissue heterogeneity.
- Lack of in vivo animal model confirmation of electrophysiologic phenotype.
Future Directions: Develop in vivo models to define KCNB1-driven arrhythmogenesis from enhancer perturbations, and evaluate diagnostic panels capturing regulatory variants in familial ECG syndromes.
BACKGROUND AND AIMS: Familial ST-depression syndrome (FSTD) is a recently identified inherited cardiac disease associated with arrhythmias and systolic dysfunction. The underlying genetic aetiology has remained elusive. This study aimed at finding the causative variant. METHODS: A total of 67 FSTD patients (20 families) were studied. Linkage analysis and whole-genome sequencing (WGS) were initially performed. An identified non-coding variant was functionally characterized in AC16 human cardiomyocytes, muscle tissue, and human myocardium. In silico analyses, luciferase and dCas9-activator/repressor assays, protein-DNA experiments, chromosome conformation capture (4C), and RNA sequencing were also performed. RESULTS: The electrocardiographic (ECG) phenotype was inherited in an autosomal dominant manner in all families. Linkage analysis revealed a single peak on chromosome 20, and WGS identified a single, rare, non-coding variant located 18 kb downstream of KCNB1 on chromosome 20 in all affected individuals. Perfect co-segregation with the ECG phenotype was observed together with full penetrance in all families. The variant creates a MEF2-binding site and presence of the variant allele or MEF2 co-expression enhanced transcriptional activity. dCas9-activator/repressor assays showed that KCNB1 was the only gene consistently regulated by the locus and 4C experiments in AC16 cells and human muscle tissue confirmed the locus-KCNB1 promoter interaction. Expression analysis in human endocardial tissue did not document any change in gene expression likely explained by expressional heterogeneity. CONCLUSIONS: A gain-of-function enhancer variant creates a hyperactive regulatory locus that interacts with the KCNB1 promoter and causes FSTD. This is the first time that KCNB1 has been implicated in human cardiac electrophysiology and arrhythmogenesis.
2. Survival Outcomes After Multiple vs Single Arterial Grafting Among Patients With Reduced Ejection Fraction.
In 59,641 CABG patients with a median follow-up of 5.0 years, multiarterial grafting reduced all-cause mortality versus single arterial grafting across normal to severely reduced ejection fractions, with no interaction by EF strata. Total arterial revascularization conferred additional survival benefit, especially when EF was preserved.
Impact: This large, contemporary binational analysis supports a shift toward multiarterial grafting in CABG for broad EF ranges, a practice area still dominated by single arterial strategies.
Clinical Implications: Surgeons should preferentially consider multiarterial (ideally total arterial) revascularization even in reduced EF patients, while individualizing approach in very low EF (<30%) where benefits may attenuate.
Key Findings
- Multiarterial grafting reduced all-cause mortality across normal, mild, moderate, and severe LV impairment (HR ~0.81–0.83).
- No significant interaction by ejection fraction (P=0.75), indicating consistent benefit across EF strata.
- Total arterial revascularization showed additional survival benefit compared to multiarterial plus saphenous vein grafts, except when EF <30%.
Methodological Strengths
- Very large, multicenter, population-based registry linked to national death index with long time horizon.
- Stratified analyses across EF categories with multivariable Cox models and interaction testing.
Limitations
- Retrospective observational design with potential selection and residual confounding.
- No randomization and limited procedural details on conduit quality and technical nuances.
Future Directions: Prospective pragmatic trials and advanced causal inference to validate benefits and define optimal conduit strategies by patient profile and comorbidity (e.g., diabetes, renal disease).
IMPORTANCE: Multiarterial coronary bypass procedures offer improved clinical outcomes compared with single arterial grafting with supplementary saphenous vein grafts. However, the survival advantage of multiarterial grafting across varying levels of left ventricular impairment remains uncertain. OBJECTIVE: To compare long-term survival outcomes of patients undergoing multiple vs single arterial grafting, stratified by preoperative ejection fraction. DESIGN, SETTING, AND PARTICIPANTS: A complete-case retrospective cohort study was conducted using data from a multicenter population-based cardiac registry established by the Australian & New Zealand Society of Cardiac & Thoracic Surgeons with linkage to the National Death Index. Participants were individuals who underwent primary isolated coronary bypass surgery between June 1, 2001, and January 31, 2020. Exclusion criteria were nonadults, reoperations, concomitant or previous cardiac surgical procedures, single-graft procedure, and cases without any arterial grafts. Statistical analyses were conducted in September 2024. EXPOSURES: Patients underwent either multiple or single arterial grafting, stratified by their preoperative left ventricular ejection fraction. MAIN OUTCOMES AND MEASURES: Long-term all-cause mortality. RESULTS: The study included 59 641 patients (mean [SD] age at the time of surgery, 65.8 [10.2] years; 48 321 men [81.0%]). The median follow-up duration was 5.0 years (IQR, 2.3-8.6 years). Multiarterial grafting was associated with a 19.0% relative reduction in all-cause mortality compared with single arterial grafting among patients with a normal left ventricular ejection fraction (hazard ratio [HR], 0.81; 95% CI, 0.75-0.87; P < .001). Similar survival benefits were observed among patients with mild (HR, 0.83; 95% CI, 0.77-0.90; P < .001), moderate (HR, 0.82; 95% CI, 0.74-0.90; P < .001), and severe left ventricular impairment (HR, 0.82; 95% CI, 0.71-0.96; P = .01). A multivariable Cox proportional hazards regression interaction-term analysis indicated no significant differences in the multiarterial survival benefit by ejection fraction stratification (P = .75). Multiarterial grafting with exclusively arterial conduits was associated with enhanced survival benefits compared with other multiarterial procedures with saphenous vein grafts, except when the left ventricular ejection fraction was below 30% (HR, 0.87; 95% CI, 0.67-1.13; P = .30). CONCLUSIONS AND RELEVANCE: In this retrospective cohort study using data from a binational database, multiarterial procedures were associated with reduced long-term mortality risk compared with single arterial grafting across the spectrum of preoperative left ventricular ejection fractions. Total arterial revascularization was associated with incrementally improved survival, particularly among patients with preserved ejection fraction. Because most coronary surgery practice continues to use single arterial grafting, consideration to alter grafting strategy to multiarterial procedures may be indicated.
3. Residual cholesterol and inflammatory risk in statin-treated patients undergoing percutaneous coronary intervention†.
In 15,494 statin-treated PCI patients, residual inflammatory risk (hs-CRP ≥2 mg/L) independently predicted 1-year MACE (aHR 1.78), whereas isolated residual cholesterol risk (LDL-C ≥70 mg/dL) did not (aHR 1.01). Combined residual inflammation and cholesterol also conferred elevated risk (aHR 1.56).
Impact: Findings redirect attention from LDL-centric goals to inflammation control for post-PCI residual risk under statin therapy, informing precision risk stratification and therapeutic targeting.
Clinical Implications: In statin-treated PCI patients, assess hs-CRP to identify high residual inflammatory risk; consider aggressive lifestyle and emerging anti-inflammatory strategies alongside lipid management.
Key Findings
- Isolated residual inflammatory risk (hs-CRP ≥2 mg/L) had the highest 1-year MACE rate (5.1%) and independently predicted MACE (aHR 1.78).
- Combined residual inflammatory and cholesterol risk also increased MACE risk (aHR 1.56).
- Isolated residual cholesterol risk (LDL-C ≥70 mg/dL) was not independently associated with MACE (aHR 1.01; P=0.92).
Methodological Strengths
- Large contemporary cohort with clinically meaningful stratification by LDL-C and hs-CRP.
- Adjusted Cox models and trend testing across four residual-risk strata.
Limitations
- Single-center tertiary cohort may limit generalizability; observational design with residual confounding.
- Single time-point biomarkers and exclusion of hs-CRP >10 mg/L may miss dynamic inflammatory states.
Future Directions: Randomized evaluation of anti-inflammatory therapies (e.g., IL-1β/IL-6 pathways) targeted by hs-CRP-defined residual risk in post-PCI statin-treated populations.
BACKGROUND AND AIMS: Elevated LDL-cholesterol levels and inflammation, as assessed by high-sensitivity C-reactive protein, correlate with cardiovascular risk. However, data on the relative impact of residual LDL-cholesterol and inflammatory risk among statin-treated patients undergoing percutaneous coronary intervention (PCI) is lacking. Hence, this study aimed to investigate the impact of residual cholesterol/inflammatory risk in patients on statin therapy undergoing PCI. METHODS: From 2012 to 2022, patients at a tertiary centre undergoing PCI were analysed. Patients were stratified according to LDL-cholesterol (≥70 vs <70 mg/dL) and high-sensitivity C-reactive protein (≥2 vs <2 mg/L) levels: no residual cholesterol or inflammatory risk, residual cholesterol risk, residual inflammatory risk, and combined residual cholesterol and inflammatory risk. Patients presenting with acute myocardial infarction, cancer, no statin treatment at admission, or high-sensitivity C-reactive protein levels >10 mg/L were excluded. The primary endpoint was major adverse cardiovascular events (MACEs), defined as the composite of all-cause mortality, spontaneous myocardial infarction, and stroke 1 year after the index PCI. RESULTS: A total of 15 494 patients were included. After 1-year follow-up, individuals with isolated residual inflammatory risk had the highest MACE rate (5.1%), followed by patients with combined cholesterol and inflammatory risk, no residual risk, and isolated residual cholesterol risk. After multivariable Cox regression analysis, patients with residual inflammatory risk had a 1.8-fold higher risk for MACE (adjusted hazard ratio: 1.78, 95% confidence interval 1.36-2.33, P < .001) compared with those with no residual cholesterol or inflammatory risk. This was similar in patients with combined residual cholesterol and inflammatory risk (adjusted hazard ratio: 1.56, 95% confidence interval 1.19-2.04, P = 0.001). Of note, no independent association of isolated residual cholesterol risk (adjusted hazard ratio: 1.01, 95% confidence interval .76-1.35, P-value = .920) with MACE was noted (P-trend across all groups <.001). CONCLUSIONS: Among statin-treated patients undergoing PCI, residual inflammation but not cholesterol risk was associated with an increased risk of MACE during follow-up.