1,329 calculators and references across 60 specialties, with formula confidence shown up front.
AFNet AI Prediction Model (Paroxysmal AF detection): explanation and context This tool provides two complementary approaches: (1) a CHARGE-AF–style clinical proxy estimator that uses demographic and common clinical predictors to compute an approximate probability of paroxysmal AF detection on prolonged monitoring, and (2) an optional slot to combine an external ECG-AI model probability (if you have a deployed ECG mod
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
AHEAD score - Explanation and clinical context The AHEAD score is a simple bedside risk classification tool developed to estimate short- and long-term prognosis in patients hospitalized for acute heart failure. It includes five binary items (each scores 1 point): Atrial fibrillation (present on admission or known AF), Haemoglobin below sex-specific thresholds (<130 g/L in men; <120 g/L in women), Elderly age (age > 7
AHEAD Score: Explanation and Clinical Context The AHEAD Score is a validated bedside tool to estimate short-term mortality risk in patients hospitalized for acute heart failure (AHF). It was derived from the Czech AHEAD (Acute HEart failure Database) registry, encompassing over 4,500 patients. The acronym AHEAD represents five independent risk predictors: Atrial fibrillation, Hemoglobin below normal, Elderly (>70 yea
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
AI-ECG Deep Learning Model for Left Ventricular Dysfunction — Explanation and Clinical Context This calculator implements the clinical screening logic described by Attia et al. (Nature Medicine 2019). The original model is a convolutional neural network trained on paired 12-lead ECG and echocardiogram pairs from tens of thousands of patients. The model was trained to detect reduced systolic function defined as left v
Selected references (evidence used to design index): Davies RH et al., "Precision measurement of cardiac structure and function in cardiovascular magnetic resonance using machine learning" (J Cardiovasc Magn Reson). This work shows automated algorithms can improve precision vs manual methods. Alabed S et al., "Quality of reporting in AI cardiac MRI segmentation studies" (Frontiers in Cardiovascular Medicine) — review
Air Pollution Short-term Cardiac Risk Index (PM2.5 Exposure): Explanation and Clinical Context Short-term exposure to fine particulate matter (PM₂.₅, particles with diameter ≤2.5 μm) has been shown to increase the risk of acute cardiovascular events such as myocardial infarction, arrhythmia, heart failure exacerbation, and sudden cardiac death. Epidemiological studies demonstrate that even transient exposure to eleva
AKI–KDIGO Stage Correlation with Heart Failure Mortality: Explanation and Clinical Context Acute Kidney Injury (AKI) defined by KDIGO criteria is strongly associated with increased mortality in patients hospitalized with heart failure. Stage 1 AKI is associated with a modest increase in in-hospital and short-term mortality, whereas Stage 2 and Stage 3 AKI significantly elevate the risk of death. Patients with severe
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
Aldrete Score Recovery Assessment Explanation and Clinical Context The Aldrete score is a structured bedside tool used to evaluate physiologic recovery after anesthesia or procedural sedation. It grades five domains that reflect the return of baseline neuromuscular function, respiratory stability, hemodynamic stability, level of consciousness and adequate oxygenation. Each domain receives a value from zero to two and
Allowable Blood Loss Calculator Explanation and Clinical Context Allowable Blood Loss represents the maximum amount of blood a patient can safely lose before reaching a predefined critical hematocrit threshold during surgery or acute bleeding. The calculation is based on the estimated blood volume multiplied by the proportional change in hematocrit from the initial value to the acceptable minimum value. This approach
Altitude Cardiac Stress Index (ACSI): Explanation and Clinical Context The ACSI is a pragmatic, heuristic tool intended to summarize cardiac stress loads for athletes training or competing at altitude. It integrates key determinants of hypoxic cardiac strain: absolute altitude and ascent rate (as proxies for ambient hypoxia burden), acclimatization time, resting oxygen saturation, heart rate, blood pressure, and hema
Alveolar Gas Equation Explanation and Clinical Context The alveolar gas equation estimates alveolar oxygen partial pressure PAO2 using inspired oxygen fraction FiO2, barometric pressure Patm, water vapor pressure PH2O, arterial carbon dioxide PaCO2 and respiratory quotient RQ. The formula used here is PAO2 equals FiO2 times Patm minus PH2O minus PaCO2 divided by RQ. Normal PAO2 depends on FiO2 and altitude. At sea le
Ambler Risk Score: Explanation and Clinical Context The Ambler Risk Score is a validated risk model designed to predict operative mortality following cardiac surgery. It incorporates patient demographics, clinical characteristics, and procedural factors into a logistic regression model. Key variables include age, sex, previous cardiac surgery, urgency of procedure, baseline renal function (creatinine), left ventricul
Ambler Score: Explanation and Clinical Context Ambler Score is a validated risk prediction model for estimating 30-day mortality after cardiac surgery, including CABG, valve procedures, and combined operations. It uses multiple preoperative patient characteristics, cardiac function parameters, and operation-related factors to calculate a probability of death using logistic regression. This tool allows clinicians to i
Ambulatory Blood Pressure Variability (ABPV) Index: Explanation and Clinical Context The Ambulatory Blood Pressure Variability (ABPV) Index quantifies the fluctuations of blood pressure over 24 hours using data from ambulatory blood pressure monitoring (ABPM). It provides several metrics including mean BP, standard deviation (SD), coefficient of variation (CV), and average real variability (ARV) to comprehensively as
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
Amplatzer Device Sizing Index (ADSI): Explanation and Clinical Context The Amplatzer Device Sizing Index (ADSI) is a validated tool to guide the selection of the optimal Amplatzer Septal Occluder (ASO) for closing Atrial Septal Defects (ASD). It is calculated as the ratio of the selected device diameter to the balloon-stretched ASD diameter. An ADSI value between 1.2 and 1.5 is generally considered optimal, ensuring
Amyloidosis Cardiac Stage (Mayo 2012): Explanation and Clinical Context The Mayo 2012 staging system is designed for patients with systemic light-chain (AL) amyloidosis and provides prognostic information based on cardiac involvement. It uses three biomarkers: NT-proBNP (>1800 pg/mL), Troponin T (>0.025 ng/mL), and difference in free light chains (dFLC >180 mg/L). Each abnormal biomarker counts as one risk factor. St
Anaerobic Threshold (AT) Value Index: Explanation and Clinical Context The Anaerobic Threshold (AT) represents the exercise intensity at which lactate begins to accumulate in the blood, signaling a shift from predominantly aerobic to anaerobic metabolism. AT Index is calculated using VO2 max and heart rate at AT, providing a relative measure of cardiovascular and metabolic efficiency during exercise. Normal AT occurs
Anesthesia Recovery Score Explanation and Clinical Context The Anesthesia Recovery Score also known as the Aldrete Score is a widely used clinical tool to evaluate patient readiness for discharge from the post anesthesia care unit. It assesses five physiological domains including activity respiration circulation consciousness and oxygen saturation. Each category is scored from zero to two with a maximum total score o
: Explanation and Clinical Context This tool combines the ASA Physical Status (ASA-PS) classification with cardiac-specific “risk modifiers” and the presence of active cardiac conditions to structure perioperative decision-making for patients with cardiovascular disease who are undergoing noncardiac surgery. The ASA-PS conveys baseline physiological reserve and comorbidity burden, and the emergency modifier “E” indic
Ankle Brachial Index For PAD Risk. Clinical Explanation and Context The Ankle Brachial Index is a simple and validated noninvasive test used to detect the presence and severity of peripheral artery disease. It is calculated by dividing the systolic blood pressure at the ankle by the highest systolic blood pressure measured in both arms. ABI provides an objective assessment of lower extremity perfusion and correlates
Anticoagulation Regimen Safety Index (Warfarin vs LMWH): Explanation and Clinical Context This tool estimates bleeding risk when choosing between Warfarin and Low Molecular Weight Heparin (LMWH) for anticoagulation therapy. The score incorporates key clinical variables known to influence bleeding risk, including advanced age, impaired renal function, prior history of major bleeding, and concurrent antiplatelet therap
Aortic Aneurysm Expansion Index (AAEI): Explanation and Clinical Context The Aortic Aneurysm Expansion Index (AAEI) quantifies the annual relative increase in aortic diameter, expressed as a percentage per year. It is calculated using the formula: (Follow-up Diameter - Baseline Diameter) / (Baseline Diameter × Time Interval) × 100%. AAEI helps clinicians identify patients at risk of rapid aneurysm growth and potentia
Aortic Compliance Index (ACI): Explanation and Clinical Context The Aortic Compliance Index (ACI) represents the ability of the aorta to expand and contract with each cardiac cycle in response to changes in blood pressure. It reflects the elastic properties of the aortic wall and serves as a surrogate marker of arterial stiffness. The formula used is: ACI = Stroke Volume / Pulse Pressure where Stroke Volume (SV) is t
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 Root Z-Score (Boston Formula): Explanation and Clinical Context The Aortic Root Z-score is a body size–adjusted measurement that quantifies how a patient’s aortic root dimension compares to population-based reference values. The Boston formula, derived from pediatric and young adult cohorts, provides a reliable way to normalize aortic root diameter according to body surface area (BSA). A Z-score represents the
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
Aortic Valve Area by Continuity Equation: Explanation and Clinical Context Aortic valve area is a fundamental parameter used to assess the severity of aortic stenosis. The continuity equation is the most widely endorsed method for calculating aortic valve area because it is grounded in the principle of conservation of mass. According to this principle, flow in the left ventricular outflow tract must equal flow across
APACHE II score explanation and clinical context APACHE II is a severity scoring system developed to estimate risk of hospital mortality for patients admitted to intensive care. The score is the sum of an acute physiology score derived from the worst value in the first 24 hours for twelve physiologic variables plus points for age plus points for chronic health status. A higher total score indicates greater physiologi
APACHE II Score: Explanation and Clinical Context The APACHE II (Acute Physiology And Chronic Health Evaluation II) score is a widely used ICU severity-of-disease classification system that sums abnormalities in 12 physiologic variables (the Acute Physiology Score, APS), adds age points, and adds chronic health points to provide an admission severity score (range 0–71). Higher scores correlate with higher hospital mo
APACHE IV calculation note APACHE IV is a validated severity scoring system published for hospital mortality assessment in critically ill adults. The original model uses many physiologic variables combined with spline terms and coefficients derived from a very large multicenter dataset. Reproducing the exact predicted mortality requires the original model coefficients or authorized software. This tool collects the da
APACHE-IV: Purpose, limitations, and clinical context APACHE-IV (Acute Physiology and Chronic Health Evaluation, version IV) is an updated severity-of-illness model developed from a very large multi-center ICU cohort to estimate hospital mortality and length of stay for critically ill adults. The original publication describes a multivariable logistic procedure using first-24-hour physiologic data, age, chronic healt
APACHE-Cardiac Subset: Explanation and Clinical Context The APACHE-Cardiac Subset is a risk stratification tool adapted from the APACHE III scoring system, specifically designed for cardiac intensive care patients. It incorporates variables including age, heart rate, mean arterial pressure, serum creatinine, PaO2/FiO2 ratio, and mechanical ventilation status to estimate mortality risk. The score allows clinicians to
APGAR Score Explanation and Clinical Context APGAR Score is a standardized clinical tool to rapidly assess the status of a newborn during the first moments of life. It evaluates Appearance Pulse Grimace Activity and Respiration each scored from zero to two resulting in a total score between zero and ten. Scores of seven to ten generally indicate good condition while four to six suggests moderate depression and may re
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
ApoB/ApoA1 Ratio: Explanation and Clinical Context The ApoB/ApoA1 ratio is a validated biomarker reflecting the balance between atherogenic and anti-atherogenic lipoproteins. ApoB represents the total number of atherogenic particles (including LDL, VLDL), while ApoA1 is the main protein in HDL, which is protective. A higher ApoB/ApoA1 ratio indicates a predominance of atherogenic lipoproteins and a higher risk for ca
APOE Genotype Risk Index (E2/E3/E4 variants): Explanation and Clinical Context The Apolipoprotein E (APOE) gene has three major alleles: E2, E3, and E4. The combination of these alleles determines an individual's genotype, which significantly influences lifetime risk for Alzheimer's disease and cardiovascular outcomes. E2 allele is generally protective, E3 is neutral, and E4 increases risk, particularly in homozygous
APRI (AST to Platelet Ratio Index): Explanation and Clinical Context The APRI score is a non-invasive index to predict the presence of liver fibrosis and cirrhosis, originally validated in patients with chronic hepatitis C. It is calculated using the formula: [(AST / Upper Limit of Normal AST) / Platelet Count (10^9/L)] × 100. Lower values (<0.5) indicate minimal or no fibrosis, intermediate values (0.5–1.5) suggest
Explanation and Clinical Context The Academic Research Consortium high bleeding risk construct was developed to provide a standardized binary definition of bleeding risk in patients undergoing percutaneous coronary intervention and receiving dual antiplatelet therapy. It organizes clinical characteristics into major and minor criteria that are based on expected one year incidence of serious bleeding events. Major cri
The audited source currently returns an empty page. This catalog entry is retained for coverage and monitoring, but no clinical content or calculation is asserted.
Explanation and Clinical Context The Berlin Criteria provides a standardized method to diagnose acute respiratory distress syndrome based on the degree of hypoxemia, the requirement of positive end expiratory pressure, and the presence of bilateral opacities not fully explained by cardiac failure. The PaO2 FiO2 ratio defines the severity group. A ratio of three hundred or less with mandatory positive end expiratory p
ARDS Severity Index (PaO₂/FiO₂): Explanation and Clinical Context The ARDS Severity Index uses the ratio of arterial oxygen partial pressure (PaO₂) to fractional inspired oxygen (FiO₂) to stratify patients with acute respiratory distress syndrome according to severity. A PaO₂/FiO₂ ratio >300 mmHg indicates no ARDS; 201-300 mmHg indicates mild ARDS; 101-200 mmHg indicates moderate ARDS; < 100 mmHg indicates severe ARD
ARIC Diabetes CVD Score: Explanation and Clinical Context The ARIC Diabetes CVD Score is a validated risk assessment tool to estimate the 10-year risk of cardiovascular disease in adults with type 2 diabetes. It was derived from the Atherosclerosis Risk in Communities (ARIC) study cohort and incorporates patient-specific variables including age, sex, systolic blood pressure, total cholesterol, HDL cholesterol, smokin
ARIC Hypertension Risk Model: Explanation and Clinical Context The ARIC Hypertension Risk Model is a validated tool developed from the Atherosclerosis Risk in Communities (ARIC) Study to estimate the 5-year risk of developing hypertension in middle-aged adults. It incorporates multiple clinical variables including age, sex, race, body mass index (BMI), smoking status, physical activity level, diabetes status, and cho
Aristotle Basic Complexity Score (ABCS): Explanation and Clinical Context The Aristotle Basic Complexity Score is a validated tool designed to estimate the procedural complexity for congenital heart surgery in pediatric and adult patients. It combines factors such as the type of surgical procedure, patient age, presence of noncardiac congenital abnormalities, and genetic abnormalities. Each factor is assigned a weigh
Aristotle Basic Complexity Score (ABCS): Explanation and Clinical Context The Aristotle Basic Complexity Score is a validated tool designed to estimate the procedural complexity for congenital heart surgery in pediatric and adult patients. It combines factors such as the type of surgical procedure, patient age, presence of noncardiac congenital abnormalities, and genetic abnormalities. Each factor is assigned a weigh
Aristotle Comprehensive Complexity (ACC) Score: Explanation and Clinical Context The ACC Score is designed to quantify the overall surgical complexity in congenital heart surgery by combining the Aristotle Basic Complexity (ABC) score with procedure-dependent modifiers and patient-dependent modifiers. The ABC score (range ~1.5 to 15) itself is derived from three domains: potential mortality, potential morbidity, and
Aristotle Comprehensive Complexity Score (CCS): Explanation and Clinical Context The Aristotle Comprehensive Complexity Score (CCS) is a validated scoring system designed to quantify the overall complexity of congenital heart surgery procedures. It integrates patient-related factors (e.g., comorbidities, age, weight), procedure-related factors (e.g., technical difficulty, expected mortality), and diagnosis-related fa
ARISTOTLE HF Subgroup Outcome Index: Rationale and clinical context The original ARISTOTLE trial (apixaban vs warfarin) and its biomarker substudies showed that age, a clinical history of heart failure, and circulating biomarkers — notably NT-proBNP, high-sensitivity cardiac troponin, and growth differentiation factor-15 (GDF-15) — were among the strongest predictors of death and heart-failure related events in patie