The TIMI (Thrombolysis in Myocardial Infarction) Risk Score for Unstable Angina/NSTEMI was developed by Antman and colleagues at Brigham and Women's Hospital in 2000, from the TIMI 11B and ESSENCE trial populations (1,957 patients). It was the first widely validated, bedside risk score for the entire spectrum of unstable coronary syndromes and remains the most-cited ACS risk score in the literature. The TIMI UA/NSTEMI score uses seven equally weighted binary variables, each contributing 1 point, to predict the composite endpoint of all-cause mortality, new or recurrent MI, or severe recurrent ischaemia requiring urgent revascularisation at 14 days. It fundamentally changed how emergency physicians and cardiologists approach ACS triage.

The Global Registry of Acute Coronary Events (GRACE) score was developed from a multinational registry of 11,389 patients hospitalised with ACS across 94 hospitals in 14 countries from 1999-2001. Unlike the TIMI score (which uses binary yes/no criteria), GRACE uses continuous variables and weighted regression coefficients to generate a more precise prognostic score. The GRACE score was designed to predict both in-hospital and 6-month post-discharge mortality and has become the preferred ACS risk score in the European Society of Cardiology guidelines. GRACE 2.0 (2014) extended prediction to 1-year and 3-year mortality and removed the creatinine clearance calculation requirement, making it more accessible.

The HEART Score (History, ECG, Age, Risk factors, Troponin) was developed by Six and colleagues in the Netherlands in 2008 and validated by Backus and colleagues in 2010. It was specifically designed for use in the emergency department to rapidly risk-stratify patients presenting with chest pain for major adverse cardiac events (MACE) within 6 weeks. Unlike the TIMI score which was derived from high-risk ACS trial populations, the HEART score was derived from an unselected chest pain population — making it more applicable to general emergency department practice where the majority of patients do not have ACS. The HEART score enables safe early discharge of low-risk patients (score ≤3) without further testing.

The ACC/AHA Pooled Cohort Equations (PCE) were developed in 2013 by Goff and colleagues as the official cardiovascular risk estimation tool for the 2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk. The PCE were derived from pooling data from multiple large, diverse US cohorts (ARIC, CHS, CARDIA, Framingham Original and Offspring) including 24,626 individuals. Unlike the Framingham score, the PCE were specifically validated in White and African American populations separately and predict a harder cardiovascular endpoint — 10-year risk of first atherosclerotic cardiovascular disease (ASCVD) event, defined as nonfatal MI, coronary heart disease death, or fatal or nonfatal stroke.

The TIMI Risk Score for ST-Elevation Myocardial Infarction (STEMI) was developed by Morrow and colleagues at Brigham and Women's Hospital in 2000, derived from the InTIME II trial of 14,114 STEMI patients treated with fibrinolytic therapy (lanoteplase vs alteplase). It was designed to rapidly stratify 30-day mortality risk in STEMI patients, particularly to identify those who would derive the greatest absolute mortality benefit from aggressive reperfusion therapy. The TIMI STEMI score is a continuous 0-14 point scale using eight variables, all available at the bedside before reperfusion therapy is initiated.

Brain Natriuretic Peptide (BNP) was discovered in 1988 in porcine brain tissue by Sudoh and colleagues, though it is predominantly synthesised and secreted by ventricular cardiomyocytes in response to increased wall stress, volume overload, and elevated filling pressures. BNP and its biologically inactive cleavage product NT-proBNP are the most sensitive and specific biomarkers for heart failure diagnosis in the acute setting. The landmark ProBNP Investigation of Dyspnoea in the Emergency Department (PRIDE) study (2002) established NT-proBNP as the gold standard for AHF diagnosis, with an AUC of 0.94. BNP and NT-proBNP were subsequently incorporated into ESC 2021, ACC/AHA 2022, and NICE 2018 heart failure guidelines as diagnostic and prognostic cornerstones.

The New York Heart Association (NYHA) Functional Classification was first published in 1928 by the New York Heart Association and has been revised multiple times (1964, 1973, 1994). It is the oldest and most universally used system for quantifying functional limitation due to heart failure, providing a simple 4-class ordinal scale based on physical activity and symptom burden. Despite being entirely subjective and having poor inter-rater reliability (kappa ~0.56), NYHA class has been the primary functional endpoint or stratification variable in virtually every major heart failure clinical trial for nearly a century, including RALES (spironolactone), COPERNICUS (carvedilol), PARADIGM-HF (sacubitril-valsartan), and EMPEROR-Reduced (empagliflozin).

The classification of heart failure by left ventricular ejection fraction (LVEF) has evolved significantly over the past two decades. Originally divided into HFrEF (reduced EF, <40%) and HFpEF (preserved EF, ≥50%), the ESC 2016 guidelines introduced a third category — HFmrEF (mildly reduced EF, 40-49%) — recognising the distinct phenotype and treatment considerations of this intermediate group. The ESC 2021 guidelines further refined this, with LVEF classification now driving four distinct evidence-based treatment pathways. This classification system is fundamental because GDMT benefit is LVEF-dependent — sacubitril-valsartan, CRT, and ICD therapy have only been shown to reduce mortality in HFrEF (LVEF <40%).

Hypertension affects approximately 1.28 billion adults globally and is the single most important preventable cause of premature cardiovascular disease, stroke, and death worldwide. The blood pressure thresholds and treatment targets have been debated extensively, with notable differences between the ACC/AHA 2017 guidelines (≥130/80 mmHg defines Stage 1 hypertension) and the ESC/ESH 2023 guidelines (≥140/90 mmHg for treatment initiation in most patients). The ESC 2023 guidelines represent a major update incorporating the SPRINT (systolic target <120 mmHg) and STEP (elderly Chinese patients) trial data, along with substantial evidence on combination therapy, fixed-dose combinations (FDCs), and SGLT2 inhibitors in hypertensive patients with CKD or HF.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting over 59 million people globally. Its prevalence doubles with each decade of age after 55. AF-related stroke accounts for approximately 30% of all ischaemic strokes — the majority preventable with anticoagulation guided by CHA₂DS₂-VASc risk stratification. The management of AF has been transformed by three major evidence bases: (1) DOACs (direct oral anticoagulants) replacing warfarin for stroke prevention, (2) catheter ablation becoming first-line rhythm control for symptomatic paroxysmal AF (EARLY-AF, STOP-AF trials), and (3) EAST-AFNET 4 demonstrating mortality benefit of early rhythm control vs rate control in patients with AF <1 year.

The continuity equation for aortic valve area (AVA) is the echocardiographic gold standard for quantifying aortic stenosis severity, derived from the hydrodynamic principle of conservation of mass — stroke volume must be equal at the LVOT and at the aortic valve orifice. Developed as a clinical tool in the 1980s by Hakki and colleagues (simplified formula) and refined by Otto and colleagues, the continuity equation-derived AVA is incorporated into all major AS guidelines as the primary quantitative measure of stenosis severity. Accurate AVA calculation is essential because clinical decision-making (valve replacement timing) is heavily dependent on AVA ≤1.0 cm² as the threshold for severe stenosis.

The Pressure Half-Time (PHT) method for calculating mitral valve area (MVA) was first described by Hatle and colleagues in 1979, based on the principle that the rate of equalisation of pressure between the left atrium and left ventricle during diastole is inversely proportional to the degree of mitral stenosis. The empirical constant 220 (MVA = 220/PHT) was derived from cardiac catheterisation data and validated in early echocardiographic studies. The PHT method is simple, reproducible, and operator-independent compared to the planimetry method — making it the most widely used echocardiographic tool for MVA quantification globally.

Haemodynamic monitoring — measurement of cardiac output, filling pressures, and vascular resistance — forms the foundation of advanced heart failure and critical care cardiology. The pulmonary artery catheter (PAC/Swan-Ganz catheter), introduced by Swan and Ganz in 1970, remains the gold standard for invasive haemodynamic profiling. The Forrester classification (1977) used PCWP and cardiac index to define four haemodynamic profiles in acute MI, which evolved into the Stevenson clinical profiles (warm-dry, warm-wet, cold-dry, cold-wet) used today for ADHF management. Non-invasive estimates using echocardiography (LVOT VTI, IVC collapsibility) have largely replaced PAC in many settings.