1,329 calculators and references across 60 specialties, with formula confidence shown up front.
LF/HF Ratio (Autonomic Tone): Explanation and Clinical Context The LF/HF ratio is a key heart rate variability (HRV) parameter reflecting autonomic nervous system balance. LF (low frequency) power represents both sympathetic and parasympathetic activity, while HF (high frequency) power is primarily a marker of parasympathetic (vagal) activity. The LF/HF ratio quantifies the relative contribution of sympathetic vs par
LGE % Fibrosis Index (CMR): Explanation and Clinical Context The Late Gadolinium Enhancement (LGE) % Fibrosis Index is a quantitative measure of myocardial fibrosis obtained from cardiac magnetic resonance (CMR) imaging. It is calculated as the ratio of LGE mass to total left ventricular (LV) mass multiplied by 100, expressed as a percentage. Normal myocardium typically has minimal or no LGE; a value >5% suggests sig
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
Lights Criteria for Pleural Effusion Explanation and Clinical Context Lights Criteria is a well established diagnostic framework used to differentiate exudative pleural effusion from transudative pleural effusion based on biochemical comparison of pleural fluid and serum. Exudative effusion indicates increased capillary permeability usually due to inflammatory or malignant processes while transudative effusion occurs
Age Albumin day zero g per dL Bilirubin day zero mg per dL Bilirubin day seven mg per dL Prothrombin time seconds Lille Alcoholic Hepatitis Prognosis Score Explanation and Clinical Context The Lille Alcoholic Hepatitis Prognosis Score is an evidence based tool used to evaluate treatment response in patients with severe alcoholic hepatitis who are receiving corticosteroid therapy. The score combines age albumin biliru
Lipid Accumulation Product (LAP): Explanation and Clinical Context LAP is an index that quantifies lipid overaccumulation based on waist circumference and fasting triglyceride levels. It is designed to identify individuals with excess visceral fat and elevated cardiometabolic risk. The formula differs by sex: for men, LAP = (waist circumference [cm] - 65) × triglycerides [mmol/L]; for women, LAP = (waist circumferenc
: Explanation and Clinical Context This calculator estimates the expected benefit of lipid-lowering therapy using data derived from the Cholesterol Treatment Trialists’ (CTT) Collaboration. The model is based on large meta-analyses demonstrating that for each 1 mmol/L reduction in LDL-C, there is an approximate 22% relative reduction in major vascular events, including myocardial infarction, stroke, and cardiovascula
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Liver Function Recovery Index (LFRI) Post-VAD: Explanation and Clinical Context The Liver Function Recovery Index (LFRI) is a predictive tool used to estimate the likelihood of hepatic recovery in patients after ventricular assist device (VAD) implantation. It incorporates pre-VAD biochemical markers including total bilirubin, AST, ALT, and INR to quantify liver dysfunction severity and potential for post-operative r
Hematoma percent Laceration depth centimeter Liver Injury Grading Score Explanation and Clinical Context Liver injury grading score is part of the organ injury scale developed to standardize the assessment of hepatic trauma severity in clinical practice. The score is based on hematoma size and laceration depth which reflect the extent of anatomical disruption of hepatic tissue. Grade one typically represents minor co
Liver Stiffness Index (Elastography, Cardiovascular Implications): Explanation and Clinical Context Liver stiffness, measured by transient elastography, is a non-invasive marker of liver fibrosis. Elevated liver stiffness is not only associated with progression of chronic liver disease but also with increased cardiovascular risk. Multiple studies have shown that higher liver stiffness values correlate with subclinica
LMNA Mutation Risk Model (Sudden Cardiac Death in DCM): Explanation and Clinical Context The LMNA Mutation Risk Model predicts the 5-year risk of sudden cardiac death (SCD) in patients with dilated cardiomyopathy (DCM) carrying LMNA gene mutations. Key predictors include the presence of non-sustained ventricular tachycardia (NSVT), reduced left ventricular ejection fraction (LVEF < 45%), male sex, and the presence of
LMNA Mutation Risk Score: Explanation and Clinical Context The LMNA mutation risk score is a clinical tool developed to predict the 5-year risk of life-threatening ventricular tachyarrhythmias (VTA) in patients with LMNA gene mutations. This score incorporates factors such as sex, presence of non-missense mutations, degree of atrioventricular block, occurrence of non-sustained ventricular tachycardia (NSVT), and left
Explanation and Clinical Context Log reduction describes the degree of decrease in microbial or particulate count after a decontamination process. It quantifies how many powers of ten the original concentration has been reduced. A one log reduction represents a ten fold decrease while a two log reduction represents a one hundred fold decrease. In clinical and biomedical research settings log reduction is widely used
Logistic EuroSCORE: Explanation and Clinical Context Logistic EuroSCORE is a validated risk prediction model for estimating perioperative mortality in patients undergoing cardiac surgery, including CABG, valve surgery, and aortic procedures. It uses multiple preoperative patient factors, cardiac function parameters, and operation-related variables in a logistic regression model to calculate a precise probability of m
Long Term Dual Antiplatelet Therapy Extension Consideration Tool Explanation and Clinical Context This tool provides a structured approach to consider extension of dual antiplatelet therapy beyond the first year after an acute coronary syndrome. It is intended for patients who have completed at least several months of dual antiplatelet therapy with aspirin and a P2Y12 inhibitor and who are now being evaluated for con
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Low Cardiac Output Syndrome (LCOS) Score: Explanation and Clinical Context Low Cardiac Output Syndrome (LCOS) is a major postoperative complication after adult cardiac surgery, associated with increased morbidity and mortality. This scoring system was developed by Kang et al. (2017) to predict the probability of LCOS based on preoperative and intraoperative variables, including age, left ventricular ejection fraction
Calculator Explanation and Clinical Context This calculator provides noninvasive echocardiographic estimates that support interpretation of pulmonary artery pressures and pulmonary vascular resistance in clinical practice. Systolic pulmonary artery pressure is estimated from the peak tricuspid regurgitation velocity using the modified Bernoulli equation and an estimate of right atrial pressure. Use this estimate as o
Explanation and Clinical Context This calculator uses the Brock University Model which is one of the most validated prediction tools for estimating the probability of malignancy in pulmonary nodules detected on computed tomography. It integrates clinical variables and radiologic features to produce a numerical estimate of cancer probability that supports decision making in surveillance imaging biopsy or surgical eval
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
LV End-Systolic Volume Reduction Index (LVESVRI): Explanation and Clinical Context LVESVRI is a measure of left ventricular reverse remodeling, calculated as the percentage reduction in LV end-systolic volume (LVESV) from baseline to follow-up after cardiac resynchronization therapy (CRT). A reduction of >15% in LVESV is considered a marker of positive response to CRT and is associated with improved clinical outcomes
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)
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)
LV Global Strain Abnormality Index (HCM/DCM): Explanation and Clinical Context The LV Global Strain Abnormality Index quantifies the extent of segmental myocardial dysfunction in patients with hypertrophic cardiomyopathy (HCM) or dilated cardiomyopathy (DCM). It combines global longitudinal strain (GLS) assessment and segmental strain abnormalities to provide a percentage score reflecting myocardial involvement. GLS
LV GLS Drop >15% Rule: Explanation and Clinical Context The LV GLS (Left Ventricular Global Longitudinal Strain) Drop >15% Rule is used for early detection of subclinical cardiotoxicity, particularly in patients receiving potentially cardiotoxic chemotherapy, such as anthracyclines or trastuzumab. GLS is a sensitive echocardiographic parameter reflecting myocardial deformation. A relative reduction of more than 15% f
LV Lead Position Index (LVLPI): Explanation and Clinical Context The LV Lead Position Index (LVLPI) is a quantitative measure used to assess the position of the left ventricular (LV) lead relative to the apical and basal segments of the LV in patients undergoing cardiac resynchronization therapy (CRT). It is calculated by dividing the distance from the LV lead to the apex of the left ventricle by the distance to the
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
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Left Ventricular (LV) Scar Burden: Explanation and Clinical Context LV Scar Burden (%) represents the proportion of left ventricular myocardial mass affected by fibrosis or infarction, typically quantified using Late Gadolinium Enhancement (LGE) on cardiac MRI. This parameter is clinically significant as higher LV scar burden is associated with an increased risk of ventricular arrhythmias, sudden cardiac death, and a
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
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
LV Wall Thickness Z-score: Explanation and Clinical Context The LV Wall Thickness Z-score is a standardized metric to assess left ventricular hypertrophy (LVH) relative to body size in children and adolescents. It compares the measured interventricular septal (IVS) and posterior wall thickness (LVPW) to age- and body size–specific normative data, providing a Z-score that indicates how many standard deviations the mea
LVEF Decline Hazard Ratio Model: Explanation and Clinical Context Left ventricular ejection fraction (LVEF) decline is a significant predictor of adverse outcomes in heart failure patients. A decline of > 5% in LVEF is associated with a 2.2-fold increased risk of mortality. This model assists clinicians in identifying patients at higher risk due to LVEF deterioration, enabling timely interventions and management stra
: Explanation and Clinical Context This tool classifies patients for implantable cardioverter-defibrillator (ICD) therapy based on Left Ventricular Ejection Fraction (LVEF), using widely recognized thresholds. A reduced LVEF < 35% is associated with a significantly higher risk of sudden cardiac death (SCD), making these patients candidates for ICD implantation for primary prevention. Patients with LVEF between 36-40%
LVEF-Based Surgical Risk Index: Explanation and Clinical Context The LVEF-Based Surgical Risk Index is a validated tool to estimate perioperative mortality in patients undergoing non-cardiac surgery, incorporating left ventricular ejection fraction (LVEF), patient age, and type of surgery. A lower LVEF reflects impaired cardiac function and is associated with higher perioperative risk. Age is a modifying factor, with
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 Gradient Severity Index: Explanation and Clinical Context The LVOT Gradient Severity Index is a composite tool used to assess the severity of left ventricular outflow tract (LVOT) obstruction in patients, especially those with hypertrophic cardiomyopathy. It incorporates peak LVOT gradient, NYHA functional class, and presence of syncope to stratify patients into mild, moderate, or severe obstruction risk. This i
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
Lyme Carditis AV Block Risk Score: Explanation and Clinical Context The Lyme Carditis Suspicious Index (LCI)—also referred to as the Lyme Carditis AV Block Risk Score—was developed by Besant et al. (Circulation: Arrhythmia and Electrophysiology, 2018) to identify patients with high-grade atrioventricular (AV) block secondary to Lyme carditis. The tool assists clinicians in differentiating reversible Lyme carditis fro
Lysholm Knee Score Explanation and Clinical Context The Lysholm Knee Score is a validated clinical instrument created to evaluate knee function especially following ligament injury and reconstruction. It measures key functional dimensions that patients commonly experience including limp pain instability swelling mechanical symptoms stair climbing ability and squatting capability. The structure of this scoring system
M-Boston Score (Mitral Arcade Surgical Outcome): Explanation and Clinical Context This scoring model is designed to predict surgical outcomes in patients with mitral arcade anomaly undergoing mitral valve surgery. It incorporates preoperative and intraoperative variables such as leaflet involvement, annular dimension, chordal extension, and ventricular function. A higher score indicates a (worse/better) surgical outc
MacNew Heart Disease Health-Related Quality of Life (HRQOL) Score: Explanation and Clinical Context The MacNew Heart Disease HRQOL questionnaire is a validated patient-reported outcome tool designed to assess the impact of heart disease on a patient’s physical, emotional, and social functioning. It consists of 27 items rated on a 7-point Likert scale (1 = poor, 7 = excellent), which are grouped into three domains: Ph
Explanation and Clinical Context A macro diet ratio describes the proportion of daily calories that come from carbohydrate protein and fat. These three macronutrients support different physiologic functions. Carbohydrate serves as the primary energy source for most tissues and supports high intensity metabolic activity. Protein maintains lean body mass supports immune regulation and contributes to hormone production.
MADIT II Risk Model: Explanation and Clinical Context The MADIT II Risk Score is a validated tool designed to estimate the 2-year mortality risk in patients with ischemic cardiomyopathy and severely reduced left ventricular ejection fraction (<30%). It uses easily obtainable clinical variables including age >70 years, NYHA functional class >I, presence of diabetes, QRS duration >120 ms, atrial fibrillation, BUN >26 m
MADIT-CRT Responder Score: Explanation and Clinical Context The MADIT-CRT Responder Score was developed from the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) to identify heart failure patients most likely to experience reverse left ventricular remodeling and clinical benefit from CRT. This score integrates key predictors including female sex, non-ischemic e
MADIT-CRT Response Score: Explanation and Clinical Context The MADIT-CRT Response Score is a clinical tool developed to predict the likelihood of a favorable response to cardiac resynchronization therapy with defibrillator (CRT-D) in patients with heart failure and mild symptoms. The score is based on seven baseline clinical and echocardiographic variables: female sex, non-ischemic etiology, left bundle branch block
MADIT-ICD Benefit Score — Explanation and clinical context The MADIT-ICD Benefit Score (Younis et al., 2021) integrates two competing risk scores to predict the likelihood that a patient with low LVEF will derive survival benefit from a prophylactic implantable cardioverter-defibrillator (ICD). The first component estimates the risk of life-threatening ventricular tachyarrhythmia (VT/VF) using eight clinical predicto
MADIT-II Risk Model: Explanation and Clinical Context The MADIT-II Risk Model is a validated tool to estimate the potential survival benefit of an implantable cardioverter-defibrillator (ICD) in patients with prior myocardial infarction and reduced left ventricular ejection fraction (LVEF <30%). It incorporates clinical variables including age, NYHA class, QRS duration, serum creatinine, history of myocardial infarct
— Explanation and Clinical Context The MADIT-RIT (Multicenter Automatic Defibrillator Implantation Trial–Reduce Inappropriate Therapy) randomized trial compared three ICD programming strategies designed to minimize unnecessary device therapy: conventional programming (treating tachyarrhythmias starting at ~170 bpm with short detection), high-rate programming (treat only arrhythmias ≥200 bpm), and delayed/duration pro
MAGGIC (Meta-Analysis Global Group in Chronic Heart Failure) score: explanation and clinical context The MAGGIC score is an integer-based risk score derived from an individual patient data meta-analysis of >39,000 heart-failure patients and uses 13 routinely available clinical variables to estimate medium-term mortality. The model assigns integer points to age (with points varying by EF band), LVEF categories, systol
MAGGIC Mortality Risk Score: Explanation and Clinical Context The MAGGIC (Meta-Analysis Global Group in Chronic Heart Failure) Risk Score is a validated prognostic model that estimates all-cause mortality in patients with heart failure, developed from data pooled from over 39,000 patients across 30 studies. It incorporates simple, readily available clinical variables such as age, sex, NYHA class, LVEF, systolic blood
MAGGIC Risk Score: Comprehensive Explanation and Clinical Context The MAGGIC (Meta-Analysis Global Group in Chronic Heart Failure) Risk Score is a validated clinical tool developed from over 39,000 patients with heart failure across 30 cohort studies. It predicts all-cause mortality in both HFrEF and HFpEF patients by integrating 13 routinely available variables such as age, sex, NYHA class, LVEF, blood pressure, BMI
Performance Status Select PS 0 PS 1 PS 2 PS 3 PS 4 Serum Sodium (mmol per L) Serum Lactate Dehydrogenase (U per L) Alkaline Phosphatase (U per L) Serum Albumin (g per L) TNM Stage Group Select Limited Extensive Manchester SCLC Staging Score Comprehensive Explanation and Clinical Context The Manchester SCLC Staging Score is a validated prognostic model created to classify patients with small cell lung cancer into grou