1,329 calculators and references across 60 specialties, with formula confidence shown up front.
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
Apical HCM Index: Explanation and Clinical Context The Apical HCM Index is a simple echocardiographic metric calculated as the ratio of maximal apical wall thickness to the left ventricular end-diastolic diameter (LVEDD). It was first described by Kobayashi et al. to identify patients with apical hypertrophic cardiomyopathy (HCM), particularly in populations where this variant is more prevalent, such as in Japan. An
Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Recommendations for the Evaluation of LV Diastolic Function by Echocardiography: An Update from the ASE and EACVI (2016) ASE recommendations for the evaluation of LV diastolic function by echocardiography: Quick reference (2016)
— Explanation and Clinical Context This algorithm implements a pragmatic, clinic-level approach to interpreting daily pulmonary artery diastolic (PAD) and (optionally) mean pulmonary artery (PAM) pressure readings obtained from an implanted CardioMEMS™ sensor. The logic uses Merlin.net/Abbott default thresholds when available: a narrow "maintenance" band (PAD ±2 mmHg) where no immediate hemodynamic change is usually
CURB65 Pneumonia Severity Score Explanation and Clinical Context CURB65 assigns one point for each of five readily available clinical variables at initial assessment: new onset confusion, blood urea greater than 7 mmol per liter, respiratory rate of 30 breaths per minute or more, low blood pressure defined as systolic less than 90 mm Hg or diastolic 60 mm Hg or less, and age 65 years or older. The total score ranges
DeFeo Score: Explanation and Clinical Context The DeFeo Score is a validated tool to predict the surgical indication in patients with mitral valve disease. It incorporates functional, structural, and hemodynamic parameters: NYHA functional class, left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), and pulmonary artery pressure (PAP). Each parameter is assigned points based on t
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/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
ESC 2015 Pericarditis Risk Factors: Explanation and Clinical Context The 2015 ESC guideline identifies several predictors associated with an increased risk of complications and poorer prognosis in patients presenting with acute pericarditis. Major risk features include: high fever (>38 °C), a subacute clinical course (insidious or prolonged symptom onset), evidence of a large pericardial effusion (diastolic echo-free
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
Heart transplant, Atrioventrcular block and paced, and Atrial fibrillation (with impaired EF) Recommendations for the Evaluation of LV Diastolic Function by Echocardiography: An Update from the ASE and EACVI (2016) ASE recommendations for the evaluation of LV diastolic function by echocardiography: Quick reference (2016)
HFA-PEFF Score: Explanation and Clinical Context The HFA-PEFF algorithm is a stepwise diagnostic approach for suspected heart failure with preserved ejection fraction (HFpEF) that uses three domains — functional (diastolic function / filling pressure and longitudinal strain), morphological (left atrial enlargement, left ventricular hypertrophy/geometry), and biomarkers (natriuretic peptides). Each domain contributes
Hypertensive Heart Disease Severity Scale (HHDS): Explanation and Clinical Context HHDS is a validated tool to assess the severity of cardiac involvement in patients with chronic hypertension. It evaluates structural and functional parameters of the heart including left ventricular hypertrophy (LVH), left atrial enlargement (LAE), diastolic dysfunction, and systolic dysfunction (EF <50%). The cumulative score stratif
Kidney Damage Risk Index in Hypertension (KDRI-H): Explanation and Clinical Context KDRI-H is a validated concept for estimating the risk of chronic kidney damage in patients with hypertension. It incorporates clinical and laboratory parameters such as age, systolic and diastolic blood pressure, estimated glomerular filtration rate (eGFR), and proteinuria. The index allows clinicians to stratify patients into low, mo
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
Left Atrial (LA) Volume Severity Index in Hypertrophic Cardiomyopathy (HCM): Explanation and Clinical Context The Left Atrial Volume Index (LAVI) is calculated as the left atrial volume (LAV) divided by the body surface area (BSA), providing a body size–adjusted measure of LA enlargement. LA enlargement in HCM reflects chronic diastolic dysfunction, elevated left ventricular filling pressures, and contributes to risk
Left Atrial Pressure LAP Explanation and Clinical Context Left atrial pressure represents the pressure within the left atrium and provides an indirect assessment of left ventricular filling pressures. Echocardiography offers a non invasive method to estimate LAP through the ratio between transmitral early filling velocity and early diastolic mitral annular velocity. The E over e average ratio is strongly correlated w
Left Ventricular Cavity Size Index for Athletes (BSA-adjusted): Explanation and Clinical Context The Left Ventricular (LV) Cavity Size Index is calculated by dividing the LV end-diastolic dimension (LVEDD) by body surface area (BSA). This index normalizes cardiac size to body size, allowing better differentiation between physiological enlargement due to athletic training and pathological dilation seen in cardiomyopat
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 Diastolic Stress Test Index: Explanation and Clinical Context The Left Ventricular (LV) Diastolic Stress Test Index, primarily expressed as the ratio of early mitral inflow velocity (E) to early diastolic annular velocity (e′) during peak exercise, is a validated echocardiographic parameter to assess left ventricular filling pressures under stress conditions. A normal response (E/e′ < 10) suggests adequate relaxat
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
Assessment of LV filling pressures in Hypertrophic Cardiomyopathy Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Recommendations for the Evaluation of LV Diastolic Function by Echocardiography: An Update from the ASE and EACVI (2016) ASE recommendations for the evaluation of LV diastolic function by echocardiography: Quick reference (2016)
Assessment of Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Recommendations for the Evaluation of LV Diastolic Function by Echocardiography: An Update from the ASE and EACVI (2016) ASE recommendations for the evaluation of LV diastolic function by echocardiography: Quick reference (2016)
Assessment of Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Recommendations for the Evaluation of LV Diastolic Function by Echocardiography: An Update from the ASE and EACVI (2016) ASE recommendations for the evaluation of LV diastolic function by echocardiography: Quick reference (2016)
Mean Arterial Pressure MAP: Comprehensive Explanation and Clinical Context Mean Arterial Pressure represents the average pressure in the arteries throughout one cardiac cycle. MAP is considered a more reliable indicator of tissue perfusion compared to systolic or diastolic pressure alone because it incorporates both systole and diastole within a single integrated value. The commonly used clinical formula uses one thi
Calculate Global Longitudinal Strain (GLS), Global Circumferential Strain (GCS), and Global Radial Strain (GRS) Myocardial Strain (GLS, GCS, GRS): Comprehensive Explanation and Clinical Context Myocardial strain quantifies myocardial deformation as a percentage change from the end-diastolic state. Global Longitudinal Strain (GLS) reflects the shortening of subendocardial longitudinal fibers and is reported as a negat
Left ventricle (Size) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Left ventricle (Mass) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Left ventricle (Volume) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and
Left ventricular diastolic function LAP indeterminate if only 1 of 3 parameters available. Pulmonary vein S/D ratio <1 applicable to conclude elevated LAP in patients with depressed LV EF. Recommendations for the Evaluation of LV Diastolic Function by Echocardiography: An Update from the ASE and EACVI (2016)
Pulmonary Regurgitation (1) Unless there are other reasons for RV enlargement. (2) Exception: acute PR. (3) Identifies a CMR-derived PR fraction >40%. (4) Steep deceleration is not specific for severe PR. (5) Not reliable in the presence of high RV end diastolic pressure. (6) Defined as the duration of the PR signal divided by the total duration of diastole, with this cutoff identifying a CMR-derived PR fraction > 25
Tricuspid Regurgitation Bolded signs are considered specific for their tricuspid regurgitation grade. (1) RV and RA size can be within the “normal” range in patients with acute severe TR. (2) Signs are nonspecific and are influenced by many other factors (RV diastolic function, atrial fibrillation, RA pressure). (3) There are little data to support further separation of these values. ASE Recommendations for Noninvasi
Paravalvular Leak (PVL) Severity Score: Rationale, Calculations, and Clinical Use This tool consolidates validated catheter-based hemodynamic indices to grade PVL severity immediately after transcatheter aortic valve replacement (TAVR). The core metric is the Aortic Regurgitation Index (ARI), defined as ((DBP − LVEDP) / SBP) × 100. Lower values imply greater diastolic run-off into the LV and more severe PVL. In the s
Pulse Pressure: Explanation and Clinical Context Pulse pressure is the numerical difference between systolic and diastolic blood pressure. It reflects the interaction between stroke volume, aortic compliance, and ventricular function. A normal pulse pressure in healthy adults is approximately forty millimeters of mercury, although this value may vary with age. A widened pulse pressure may indicate increased arterial
Pulse Pressure Index (PPI): Explanation and Clinical Context Pulse Pressure Index (PPI) is the ratio of pulse pressure (PP) to systolic blood pressure (SBP), calculated as (SBP – DBP) / SBP. It provides a standardized measure of arterial stiffness and cardiovascular risk. Pulse pressure reflects the difference between systolic and diastolic blood pressure and serves as a surrogate for arterial compliance. Higher PPI
Renal Resistive Index (RRI) by Doppler Ultrasound: Explanation and Clinical Context The Renal Resistive Index (RRI) is a non-invasive Doppler ultrasound parameter used to evaluate renal arterial resistance and kidney perfusion. It is calculated using the formula: RRI = (PSV - EDV) / PSV, where PSV is the peak systolic velocity and EDV is the end diastolic velocity of intrarenal arteries. Normal RRI values range betwe
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
RVEDd Z-score: Explanation and Clinical Context The RVEDd Z-score expresses the deviation of measured right ventricular end-diastolic dimension (in mm) from the predicted mean value, normalized by the standard deviation (SD) of the reference population. A Z-score of 0 means that the measurement equals the population mean; positive values indicate enlargement relative to body size, negative values indicate smaller dim
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
Systolic Pressure Recovery Index (Post-Pulmonary Embolism Healing): Explanation and Clinical Context The Systolic Pressure Recovery Index (SPRI) is a hemodynamic ratio used to evaluate right ventricular and pulmonary arterial recovery after acute pulmonary embolism (PE). It quantifies the degree of pressure normalization across the pulmonary circulation, specifically reflecting how systolic and diastolic pressures re
White Coat Hypertension Risk Index: Explanation and Clinical Context The White Coat Hypertension (WCH) Risk Index estimates the likelihood that a patient’s elevated office blood pressure readings are due to the white coat effect rather than sustained hypertension. It integrates office systolic and diastolic BP, age, sex, family history, and patient anxiety during measurement to calculate a probabilistic risk using a
Z-Score for Left Ventricular End-Diastolic Dimension (LVEDD): Explanation and Clinical Context Z-Score LVEDD provides a standardized method to assess left ventricular size relative to body size. It is calculated as the difference between the measured LVEDD and the predicted LVEDD (adjusted for body surface area), divided by the standard deviation from reference data. This score allows clinicians to identify abnormal