A focused collection of 40 calculators, scores, and clinical references.
Agatston Calcium Score (CT): Explanation and Clinical Context The Agatston Score is a quantitative measure of coronary artery calcium (CAC) obtained from non-contrast CT scans. It is calculated by multiplying the area of each calcified lesion by a density factor derived from the peak Hounsfield Unit (HU) within that lesion. The sum of all lesions' scores gives the total Agatston Score. Higher scores correlate with gr
Aortic Distensibility Index (ADI): Explanation and Clinical Context The Aortic Distensibility Index (ADI) is a measure of aortic elasticity, calculated using the change in aortic diameter during the cardiac cycle relative to pulse pressure. It reflects the ability of the aorta to expand and recoil with each heartbeat. Higher ADI values indicate a more compliant aorta, while lower values suggest increased stiffness, w
Aortic Stiffness Index (ASI): Explanation and Clinical Context The Aortic Stiffness Index (β) is a non-invasive echocardiographic measure of the intrinsic stiffness of the ascending aorta. It reflects the mechanical properties of the aortic wall and is calculated using systolic and diastolic blood pressures and the corresponding aortic diameters. An increased ASI indicates reduced aortic compliance and is associated
Cornell Voltage–Duration Product (CVDP): Explanation and Clinical Context The Cornell Voltage–Duration Product (CVDP) is a refined electrocardiographic index developed to improve the detection of left ventricular hypertrophy (LVH) by integrating both voltage magnitude and QRS duration. It was proposed by Molloy et al. (Circulation, 1992) based on data from the Cornell and Framingham studies. Formula: CVDP = (R in aVL
Coronary Artery Calcium (CAC) Percentile Ranking: Explanation and Clinical Context CAC percentile ranking provides an age- and sex-specific comparison of an individual's coronary artery calcium score to a reference population, as defined in the Multi-Ethnic Study of Atherosclerosis (MESA). It helps to stratify atherosclerotic cardiovascular disease (ASCVD) risk beyond traditional risk factors. A higher percentile ind
Coronary Artery Volume Score (CAVS): Explanation and Clinical Context The Coronary Artery Volume Score quantifies the total volume of the main coronary arteries (Left Main, Left Anterior Descending, Left Circumflex, Right Coronary Artery) as measured on coronary computed tomography angiography (CCTA). It is used to assess the overall burden of atherosclerosis within the coronary circulation. Higher values indicate gr
CT Fractional Flow Reserve (FFRct): Explanation and Clinical Context CT FFR is a non-invasive imaging-derived estimate of the pressure drop across a coronary stenosis, simulating the fractional flow reserve obtained by invasive measurement. It integrates coronary CT angiography data with computational fluid dynamics (CFD) or simplified algorithms to predict lesion-specific ischemia. FFRct values <0.75 generally indic
E/A Ratio Grading (Diastolic Function): Explanation and Clinical Context The E/A ratio is obtained from Doppler echocardiography by dividing the peak early (E) mitral inflow velocity by the peak atrial (A) contraction velocity. It is a cornerstone for evaluating left ventricular diastolic function. Grade I (E/A < 0.8) represents impaired relaxation, commonly seen in early diastolic dysfunction and aging. Grade II (E/
E over e Ratio: Clinical Explanation and Interpretation The E over e ratio provides an indirect estimation of left ventricular filling pressures by combining transmitral inflow velocity with myocardial relaxation velocity measured through tissue Doppler imaging. The early transmitral flow velocity rises when left atrial pressure increases, while the e prime velocity decreases when myocardial relaxation is impaired. T
E/e' Ratio: Explanation and Clinical Context The E over e prime ratio is one of the most widely used echocardiographic indices to estimate left ventricular filling pressure. The E wave represents early diastolic transmitral flow velocity which increases when the left atrial pressure rises. The e prime velocity is measured at the mitral annulus and reflects the intrinsic rate of myocardial relaxation. Since e prime de
Epicardial Fat Volume (CT Quantification): Explanation and Clinical Context Epicardial fat volume (EFV) represents the total volume of adipose tissue located between the myocardium and the visceral layer of the pericardium, quantifiable via non-contrast or contrast-enhanced cardiac CT. EFV is calculated by summing the areas of epicardial fat on each slice (cm²) multiplied by the slice thickness (cm) and the number of
Extracellular Volume Fraction (ECV) by MRI: Explanation and Clinical Context Extracellular Volume Fraction (ECV) quantifies the proportion of the myocardial tissue that is extracellular space, providing a non-invasive estimate of diffuse myocardial fibrosis and infiltration. The calculation uses pre- and post-contrast T1 values of myocardium and blood, corrected for the patient's hematocrit: ECV = (1 - Hct) × (ΔR1_my
e' Average: Explanation and Clinical Context The e prime average value represents the combined early diastolic mitral annular velocity obtained from the lateral and septal annulus using tissue Doppler imaging. This index provides a quantitative assessment of myocardial relaxation, which is a key determinant of left ventricular diastolic function. Because the lateral annulus typically exhibits higher velocities and th
Global Longitudinal Strain (GLS): Explanation and Clinical Context Global Longitudinal Strain (GLS) by speckle-tracking echocardiography measures the percentage deformation (shortening) of the left ventricular myocardium in the longitudinal direction during systole. GLS is reported as a negative percentage (for example, −20% represents greater shortening than −15%) and is a sensitive measure of longitudinal systolic
Gubner–Ungerleider Index — explanation and clinical context The Gubner–Ungerleider voltage index is an early electrocardiographic voltage criterion intended to detect left ventricular hypertrophy (LVH). It is calculated as the algebraic sum of the amplitude of the R wave in lead I plus the amplitude of the S wave in lead III (R(I) + S(III)). Classic sources and many contemporary reviews report a commonly used thresho
Left Atrial Volume Index (LAVI): Explanation and Clinical Context LAVI represents the left atrial volume indexed to body surface area and serves as a reliable marker of chronic diastolic burden. Enlargement of the left atrium occurs gradually as a consequence of prolonged elevation of left ventricular filling pressure. Because of this, LAVI is considered a structural biomarker that reflects chronic diastolic dysfunct
LGE Extent (% Myocardium Scarred): Explanation and Clinical Context LGE (Late Gadolinium Enhancement) imaging by cardiac MRI allows quantification of myocardial scar tissue, expressed as a percentage of total left ventricular (LV) myocardial mass. The LGE extent is calculated as (Scar Mass / Total LV Myocardial Mass) × 100. Low values (0–5%) represent minimal or no fibrosis, while higher percentages indicate signific
Left Ventricular Diastolic Dysfunction Grade (ASE 2016): Explanation and Clinical Context LV diastolic dysfunction refers to abnormal filling and relaxation of the left ventricle. ASE 2016 recommends an integrative approach using four parameters: E/e' ratio, septal e', TR velocity, and left atrial volume index (LAVI). Grade I represents impaired relaxation with normal filling pressures, Grade II represents pseudonorm
LV End-Diastolic Volume Index (LVEDVI): Explanation and Clinical Context LV End-Diastolic Volume Index (LVEDVI) represents the volume of blood in the left ventricle at the end of diastole, normalized to body surface area (BSA). It is a fundamental echocardiographic parameter to assess left ventricular size and remodeling. In clinical practice, LVEDVI helps detect dilated cardiomyopathy, monitor heart failure progress
Left Ventricular Mass (LVM) by MRI: Explanation and Clinical Context Left ventricular mass (LVM) is a crucial parameter reflecting the myocardial muscle mass of the left ventricle. Accurate assessment using cardiac MRI provides precise volumetric measurements and is considered the gold standard compared to echocardiography. The Devereux formula adapted for MRI calculates LVM using the cube method based on left ventri
Left Ventricular Mass Index (LVMI): Explanation and Clinical Context Left ventricular mass index is a key echocardiographic parameter used to quantify the extent of cardiac structural remodeling associated with pressure or volume overload. The Devereux formula is the most validated method for estimating left ventricular mass using linear measurements obtained from parasternal long axis imaging. The resulting left ven
Left Ventricular Sphericity Index (LVSI): Explanation and Clinical Context The Left Ventricular Sphericity Index (LVSI) is a ratio of the left ventricular short-axis diameter to the long-axis length measured at end-diastole. It quantifies the geometric remodeling of the left ventricle from a normal ellipsoid shape toward a more spherical form. A higher LVSI indicates a more spherical ventricle, which is often associa
Sokolow–Lyon Index (SV1 + tallest R in V5 or V6): Explanation and Clinical Context The Sokolow–Lyon Index is a classic electrocardiographic voltage criterion for detecting left ventricular hypertrophy (LVH). It is calculated as the depth of the S wave in lead V1 plus the amplitude of the tallest R wave in lead V5 or V6 (measured in millimetres). A summed value > 35 mm (3.5 mV) is the conventional cut-off suggesting L
LVOT VTI (Stroke Volume) Estimation: Explanation and Clinical Context The LVOT VTI (Left Ventricular Outflow Tract Velocity Time Integral) combined with the LVOT diameter allows estimation of stroke volume (SV) by calculating the LVOT cross-sectional area and multiplying it by the VTI. Stroke volume represents the volume of blood ejected from the left ventricle during a single cardiac cycle. Accurate estimation is im
MAPSE (Mitral Annular Plane Systolic Excursion): explanation, clinical significance and references MAPSE measures the longitudinal displacement of the mitral annulus toward the apex during systole; it is commonly measured by M-mode at the septal and lateral annulus and reported in millimetres. Typical average values reported in contemporary reference studies are approximately 12–15 mm; lower values indicate reduced l
Myocardial Perfusion Index (MPI): Explanation and Clinical Context The Myocardial Perfusion Index (MPI) quantifies the ratio of myocardial blood flow during stress to resting myocardial blood flow, serving as a non-invasive marker of coronary microvascular function and myocardial perfusion reserve. An MPI value near 2.0–3.0 is generally considered normal, reflecting adequate perfusion reserve. Reduced MPI values indi
Myocardial Strain MRI (Feature Tracking, FT) : Explanation and Clinical Context Myocardial strain imaging using cardiac MRI feature tracking (FT) allows non-invasive quantification of myocardial deformation in three directions: longitudinal (GLS), circumferential (GCS), and radial (GRS). It provides early detection of subclinical myocardial dysfunction even when left ventricular ejection fraction (LVEF) is preserved.
PCAT Attenuation Index: Explanation and Clinical Context PCAT Attenuation Index measures the mean CT attenuation of pericoronary adipose tissue surrounding coronary arteries in Hounsfield Units (HU). It serves as a non-invasive biomarker of coronary inflammation, with higher (less negative) values reflecting greater inflammatory activity in the vessel wall. It is derived from coronary CT angiography by averaging the
Peguero–Lo Presti Index — explanation and clinical context The Peguero–Lo Presti index is an electrocardiographic voltage measurement calculated as the sum of the amplitude of the deepest S wave in any lead (Sdeepest) plus the amplitude of the S wave in lead V4 (SV4). The index is expressed in millivolts (mV). In the original derivation and subsequent validations, sex-specific cutoffs were recommended: a value > 2.3
Pulmonary Artery Systolic Pressure (PASP) Estimate: Explanation and Clinical Context The PASP estimate is derived from Doppler echocardiography using the peak tricuspid regurgitation (TR) velocity and an estimate of right atrial (RA) pressure. The formula 4 × (TR velocity)^2 + RA pressure provides an approximation of pulmonary artery systolic pressure in mmHg. Elevated PASP may indicate pulmonary hypertension, right
Pulmonary Vascular Resistance (PVR) Estimate Using TRV/VTIRVOT: Explanation and Clinical Context Pulmonary vascular resistance (PVR) is a critical parameter in assessing pulmonary hypertension. The TRV/VTIRVOT method provides a non-invasive echocardiographic estimate of PVR, based on the relationship between the peak tricuspid regurgitation velocity (TRV) and the right ventricular outflow tract time-velocity integral
Pulse Wave Velocity (PWV): Explanation and Clinical Context Pulse Wave Velocity is a non-invasive measure of arterial stiffness and a strong independent predictor of cardiovascular events and mortality. It reflects the speed at which the blood pressure pulse propagates through the arterial tree, with higher values indicating stiffer arteries. Clinical assessment of PWV provides early detection of vascular aging and h
Right Atrial (RA) Area Index: Explanation and Clinical Context The RA Area Index is calculated by dividing the right atrial area (measured by echocardiography) by the patient’s body surface area (BSA), providing a standardized measurement to assess right atrial enlargement. Normal RA area index is typically < 10.5 cm²/m². Values above this threshold indicate right atrial dilation, often associated with chronic pressu
Romhilt–Estes Point-Score System: Explanation and Clinical Context The Romhilt–Estes (R-E) point-score system is a composite electrocardiographic method developed to improve ECG detection of left ventricular hypertrophy by combining six ECG features (P-terminal force in V1, high QRS voltages, ST-T changes consistent with “strain”, left axis deviation, prolonged QRS duration, and delayed intrinsicoid deflection). Each
Right Ventricular Fractional Area Change (FAC): definition, clinical meaning and evidence-based context RV FAC quantifies global right ventricular systolic function from an RV-focused apical four-chamber view by tracing the RV endocardial border in end-diastole and end-systole and applying the equation: FAC (%) = 100 × (RV end-diastolic area − RV end-systolic area) / RV end-diastolic area. The American Society of Ech
Right Ventricle to Left Ventricle (RV/LV) Ratio on Echocardiography: Explanation and Clinical Context The RV/LV ratio is a measurement derived from echocardiography that compares the end-diastolic diameter of the right ventricle (RV) to the left ventricle (LV). It is widely used to assess right ventricular dilation, which can occur in conditions such as acute pulmonary embolism, pulmonary hypertension, right heart fa
RVOT VTI Cardiac Output Estimation in Pulmonary Hypertension: Explanation and Clinical Context RVOT VTI (Right Ventricular Outflow Tract Velocity Time Integral) is a Doppler echocardiography parameter used to estimate stroke volume and cardiac output, particularly in patients with pulmonary hypertension (PH). The stroke volume is calculated as the product of the RVOT cross-sectional area and the VTI, then multiplied
Simpson’s biplane method: explanation, clinical context and references The biplane method of disks (the modified Simpson’s rule) estimates left ventricular end-diastolic and end-systolic volumes from apical 4-chamber and apical 2-ch views; the ejection fraction (LVEF) is then calculated as EF = [(EDV − ESV) / EDV] × 100%. In routine practice the machine may report volumes from each apical view and clinicians commonly
T1/T2 Mapping Index: Explanation and Clinical Context The T1/T2 Mapping Index is derived from cardiac MRI T1 and T2 relaxation times, providing a quantitative assessment of myocardial tissue characteristics. T1 mapping reflects interstitial fibrosis, edema, or infiltration, while T2 mapping is sensitive to myocardial edema. The index (T1/T2 ratio) allows clinicians to detect early myocardial abnormalities and differe
Explanation — TAPSE, physiology, clinical meaning, and prognostic context TAPSE (tricuspid annular plane systolic excursion) quantifies the longitudinal displacement of the lateral tricuspid annulus toward the apex during systole and therefore serves as a simple surrogate of right ventricular longitudinal systolic function. It is measured in M-mode aligned with the lateral tricuspid annulus in the apical four-chamber