1,329 calculators and references across 60 specialties, with formula confidence shown up front.
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
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RAAS Activation Index (Plasma Renin Activity): Explanation and Clinical Context The RAAS Activation Index reflects the activity of the renin–angiotensin–aldosterone system (RAAS), which plays a crucial role in regulating blood pressure, sodium, and fluid balance. Plasma Renin Activity (PRA) measures the enzymatic activity of renin, expressed in ng/mL/h, which indicates how strongly the RAAS system is activated. Low P
RACHS-1 (Risk Adjustment in Congenital Heart Surgery): Explanation and clinical context The RACHS-1 method groups pediatric congenital heart surgical procedures into six categories (1–6) of increasing expected operative risk to allow comparisons of in-hospital mortality between case mixes, institutions, or time periods. RACHS-1 was developed by consensus using the Pediatric Cardiac Care Consortium (PCCC) dataset and
RACHS-1 (Risk Adjustment for Congenital Heart Surgery) Surgical Complexity Score: Explanation and Clinical Context RACHS-1 is a validated classification system to estimate in-hospital mortality risk for patients undergoing congenital heart surgery. It stratifies procedures into six categories based on surgical complexity, from Category 1 (lowest risk) to Category 6 (highest risk). This tool helps clinicians, research
: Explanation and Clinical Context This calculator estimates the potential cardiovascular risk associated with chronic occupational exposure to ionizing radiation among medical professionals such as interventional cardiologists, electrophysiologists, and radiologic technologists. The model integrates traditional cardiovascular risk modifiers (age, sex, smoking, hypertension) with cumulative radiation dose to approxim
Radiation-Induced Heart Disease (RIHD) Dose Index: Explanation and Clinical Context RIHD Dose Index (RIHD-DI) is a predictive measure used to estimate the risk of cardiac complications in patients receiving thoracic radiotherapy. The index incorporates key dosimetric parameters: Mean Heart Dose, Maximum Heart Dose, and the percentage of heart volume receiving >25 Gy (V25). This model is based on epidemiological and c
Radiomics-Derived Ischemia Burden Score (R-IBS): Explanation and Clinical Context This calculator estimates global ischemic burden by blending per-vessel radiomics probabilities of functional ischemia with optional CT-derived fractional flow reserve (CT-FFR). Radiomics “Rad-signature” values represent the probability that a given coronary vessel supplies an ischemic territory; these were derived from pericoronary tis
: Explanation and Clinical Context The RALES Score is a clinical tool designed to estimate the survival benefit and safety of spironolactone therapy in patients with advanced heart failure (NYHA class III–IV) and reduced ejection fraction. It is conceptually derived from the Randomized Aldactone Evaluation Study (RALES), published in the New England Journal of Medicine in 1999. The RALES trial demonstrated that addin
Ranson Score for Acute Pancreatitis Explanation and Clinical Context The Ranson score is a prognostic scoring system developed to estimate severity and mortality risk in acute pancreatitis. It uses five clinical and laboratory criteria at admission and six criteria assessed within 48 hours. One point is assigned for each criterion met. A total score of three or greater indicates a high probability of severe disease.
RASS Sedation Scale Explanation and Clinical Context The RASS sedation scale is a validated and widely used instrument to assess level of sedation and agitation in critical care settings. The scale spans from minus five to plus four and is oriented on the presence and degree of arousal and purposeful movement. A score of minus five indicates an unarousable state. Values from minus four to minus one denote progressive
Rautaharju QT Correction Formula: Explanation and Clinical Context The Rautaharju QT correction formula is a regression-based method developed to correct the QT interval for heart rate more accurately than traditional formulas such as Bazett or Fridericia. It was derived from large population-based ECG studies to provide a less biased estimate of QTc across a wide range of heart rates. It uses the RR interval (in sec
RCPCH Myocarditis Prognosis Score: Explanation and Clinical Context The RCPCH Myocarditis Prognosis Score is a clinical risk tool developed to estimate the probability of adverse outcomes, including death or requirement for mechanical circulatory support, in children presenting with acute myocarditis. It uses variables available at presentation, including age, heart rate, systolic blood pressure, left ventricular eje
RDW-CV Index: Explanation and Clinical Context The RDW-CV Index is derived from the Red Cell Distribution Width (RDW) coefficient of variation relative to Mean Corpuscular Volume (MCV). It reflects the degree of anisocytosis (variability in red blood cell size) and is increasingly recognized as a prognostic biomarker in cardiovascular diseases. Elevated RDW-CV Index has been associated with higher risk of mortality a
: Explanation and Clinical Context Re-exploration for bleeding after cardiac surgery is one of the most feared complications, associated with increased morbidity, mortality, prolonged ICU stay, and higher transfusion requirements. Accurate preoperative and intraoperative risk prediction is therefore critical to guide preventive strategies and optimize surgical planning. This prediction model is derived from the analy
ABC-bleeding score (biomarker-based) echo "The ABC-bleeding score (Hijazi et al.) uses age, prior bleeding history and biomarkers (hemoglobin, high-sensitivity cardiac troponin, and GDF-15 or alternative renal markers). This model was shown to outperform traditional clinical scores in derivation/validation cohorts, but requires specific assays (hs-cTn, GDF-15). If you would like, provide numeric values for hs-cTnT (n
REACH Index: Explanation and Clinical Context The REACH Index is a predictive tool developed to estimate the likelihood of a patient's attendance in a cardiac rehabilitation program. It incorporates various factors such as age, gender, smoking status, marital status, and anxiety levels. The index is calculated using a logistic regression model, where each factor is assigned a coefficient based on its impact on attend
RECHARGE Score: Explanation and Clinical Context The RECHARGE (Registry of CrossBoss and Hybrid Procedures) score is a modern angiographic scoring system developed to predict the risk of technical failure in complex percutaneous coronary interventions of chronic total occlusion (CTO-PCI) performed with hybrid techniques. It incorporates six angiographic lesion characteristics: blunt stump, severe calcification, tortu
Redin-SCORE: Explanation and Clinical Context Redin-SCORE is a validated tool designed to predict 1-year risk of heart failure hospitalization or cardiovascular death in patients with chronic heart failure. It incorporates key clinical and laboratory parameters including age, NYHA class, left ventricular ejection fraction (LVEF), previous heart failure hospitalization, B-type natriuretic peptide (BNP), and serum crea
REDUCE Trial PFO Selection Criteria Model — Explanation and Clinical Context This tool first reproduces the original REDUCE trial eligibility logic (age 18–59 years, cryptogenic non-lacunar ischemic stroke within ≤180 days, and patent foramen ovale with a right-to-left shunt) and screens out key exclusions (atrial fibrillation or another high-risk cardioembolic source, ≥50% relevant arterial stenosis/occlusion, hyper
Coronary Artery Territories
Right ventricle (Size) Guidelines for the Echocardiographic Assessment of the Right Heart in Adults: ASE, EACVI, ESC, CSE (2010) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Guidelines for the diagnosis and management of acute pulmonary embolism ESC, ERS (2019) Right ventricle (Area, Volume) Recommendations for Cardiac Chamber Quantification
REHAB-HF Functional Recovery Index: Explanation and Clinical Context The REHAB-HF trial evaluated a tailored, multi-domain rehabilitation intervention in older patients hospitalized with acute decompensated heart failure (ADHF), focusing on improving physical function including endurance, mobility, strength, and balance. While the primary outcome was change in the Short Physical Performance Battery (SPPB) at 3 months
About This Calculator Relative Wall Thickness (RWT) is a geometric index used in echocardiography to assess the pattern of left ventricular remodeling. It is calculated as: RWT = (2 × PWd) / LVEDD Interpretation commonly used in clinical practice: - RWT ≤ 0.42 → Normal geometry or eccentric hypertrophy - RWT > 0.42 → Concentric remodeling or concentric hypertrophy References 1. Lang RM et al. Recommendations for Card
RELAX-AHF Mortality Prediction Score: Explanation and Clinical Context The RELAX-AHF (Relaxin in Acute Heart Failure) Mortality Prediction Score was developed from the RELAX-AHF trial to estimate the risk of all-cause mortality in patients with acute decompensated heart failure. This tool combines routine clinical variables available at admission to provide individualized risk estimates. Key predictors include age, b
Renal Angina Index (RAI): Explanation and Clinical Context The Renal Angina Index (RAI) is a validated tool to predict the development of severe acute kidney injury (AKI) in critically ill patients, especially pediatric ICU patients. It is calculated by multiplying a Risk Score (based on underlying condition severity) with an Injury Score (based on early signs such as fluid overload or rise in creatinine). RAI > 8 in
Renal Failure Index Explanation and Clinical Context Renal Failure Index is a calculated parameter used to differentiate prerenal azotemia from intrinsic renal tubular injury. It incorporates urine sodium urine creatinine and plasma creatinine into a single ratio that reflects tubular sodium handling. A low value reflects preserved tubular sodium conservation which often indicates prerenal physiology. A higher value
Renal Recovery Probability (after HF hospitalization): Explanation and Clinical Context The Renal Recovery Probability (RRP) score is a clinical tool developed to predict the likelihood of kidney function recovery within 90 days and 12 months after dialysis initiation in patients with end-stage kidney disease due to acute kidney injury (AKI). It incorporates factors such as age, sex, body mass index (BMI), hemoglobin
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
REPLACE DARE Risk Score: Explanation and Clinical Context The REPLACE DARE (Death After Replacement Evaluation) Risk Score is a predictive tool developed to estimate the 6-month all-cause mortality risk following cardiac implantable electronic device (CIED) replacement. It incorporates factors such as heart failure history, NYHA class, chronic kidney disease stage, anti-arrhythmic drug use, cerebrovascular disease hi
RER Peak Index (Respiratory Exchange Ratio): Explanation and Clinical Context The RER Peak Index is calculated as the ratio of carbon dioxide production (VCO₂) to oxygen consumption (VO₂) at peak exercise. It serves as an objective measure of exercise intensity and maximal effort during cardiopulmonary exercise testing (CPET). A normal RER at rest is approximately 0.8, reflecting primarily fat metabolism. During prog
Age Height in cm Sex Select Male Female Explanation and Clinical Context Residual Lung Volume represents the amount of air that remains in the lungs after a maximal exhalation and reflects the mechanical properties of the respiratory system including elastic recoil and airway closure. A higher Residual Lung Volume may indicate air trapping caused by conditions such as chronic obstructive pulmonary disease asthma or s
Resistant Hypertension Predictive Score: Explanation and Clinical Context The Resistant Hypertension Predictive Score is a clinical tool developed to estimate the likelihood of a patient having resistant hypertension, defined as blood pressure that remains above goal despite the concurrent use of three antihypertensive agents of different classes, one of which is a diuretic. The score incorporates five key parameters
RESP Score (Respiratory ECMO Survival Prediction) for VV-ECMO: Explanation and Clinical Context The RESP Score is a validated tool developed to predict in-hospital survival in patients receiving veno-venous ECMO for severe respiratory failure. It incorporates patient age, immunocompromised status, duration of mechanical ventilation before ECMO, central nervous system dysfunction, presence of acute non-pulmonary infec
: explanation and clinical context This page implements a proposed heuristic index to estimate the likelihood of left ventricular ejection fraction (LVEF) recovery after acute myocarditis. The index integrates several clinical and imaging features that have repeatedly been associated with myocardial recovery in published myocarditis and myocardial-injury cohorts: baseline LVEF (higher baseline LVEF associated with be
Return-to-Play Post-Myocarditis: Explanation and Clinical Context This calculator applies current expert consensus for evaluating return-to-play (RTP) readiness after myocarditis. Clearance requires a minimum restriction period of 3–6 months, complete symptom resolution, normalized cardiac biomarkers (troponin, CRP), recovery of ventricular function (LVEF ≥ 50%), and absence of ventricular arrhythmias on resting or e
Return-to-Work Prognostic Score (post-MI/CABG): Explanation and Clinical Context The Return-to-Work (RTW) Prognostic Score is a validated tool to estimate the likelihood that patients will successfully resume occupational activities after myocardial infarction (MI) or coronary artery bypass grafting (CABG). It incorporates patient age, gender, job physical demand, left ventricular ejection fraction (LVEF), and comorb
Return-to-Work After COVID Cardiac Event: Explanation and Clinical Context This calculator translates expert consensus recommendations to guide return-to-work (RTW) evaluation following COVID-19–related cardiac events. It focuses on readiness assessment, symptom resolution, biomarker normalization, and absence of active myocardial injury or arrhythmia. It is not a predictive mortality or reinjury risk model but a str
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REVEAL 2.0 Risk Score: Explanation and Clinical Context The REVEAL 2.0 Risk Score (Registry to Evaluate Early and Long-term PAH Disease Management 2.0) is a validated and widely used prognostic model developed to estimate 1-year mortality in patients with pulmonary arterial hypertension (PAH). It is based on the large U.S. REVEAL registry and integrates demographic, clinical, laboratory, echocardiographic, and hemody
REVEAL 2.0: Explanation and Clinical Context REVEAL 2.0 is a validated, weighted risk model for pulmonary arterial hypertension (PAH) that integrates demographics, hemodynamics, and biomarkers to estimate 1-year mortality. Each parameter contributes positive or negative points depending on risk direction. The final score stratifies patients into low (0–6), intermediate (7–8), and high (=9) risk. The calculator above
REVEAL Lite 2 Risk Score: Explanation and Clinical Context REVEAL Lite 2 is a simplified, non-invasive risk assessment tool for patients with pulmonary arterial hypertension (PAH). It is derived from the original REVEAL 2.0 registry and validated to provide reliable prediction of 1-year mortality using only six readily available clinical variables: WHO Functional Class, systolic blood pressure, heart rate, 6-minute w
REVERSE Trial Responder Index: Explanation and Clinical Context The REVERSE (Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction) trial introduced a multidimensional framework to identify cardiac resynchronization therapy (CRT) responders. It evaluated both structural reverse remodeling—quantified as ≥15% reduction in LVESVi—and clinical improvement—defined by changes in exercise capacity,
Revised Cardiac Risk Index (RCRI): Explanation and Clinical Context The Revised Cardiac Risk Index (RCRI) is a validated preoperative tool used to predict the risk of major cardiac complications in patients undergoing noncardiac surgery. It was originally proposed by Lee et al. (Circulation, 1999) as a simplified alternative to the Goldman Index, using six independent predictors of risk derived from multivariate anal
Revised Cardiac Risk Index RCRI Explanation and Clinical Context The Revised Cardiac Risk Index is one of the most widely used bedside tools for estimating the probability of perioperative major adverse cardiac events in patients undergoing non cardiac surgery. The score was derived from a large cohort and validated in multiple populations. It relies on six predictors that represent structural cardiac disease, myocar
Revised Geneva Score (RGS): Explanation and Clinical Context The Revised Geneva Score is a validated clinical prediction rule used to estimate the pre-test probability of pulmonary embolism (PE) in patients presenting with suspected PE. It uses objective clinical variables including age >65 years, previous DVT or PE, recent surgery or fracture, active cancer, unilateral lower limb pain, hemoptysis, heart rate, pain o
Glasgow Coma Scale GCS Systolic Blood Pressure SBP Select SBP more than 89 SBP 76 to 89 SBP 50 to 75 SBP 1 to 49 SBP 0 Respiratory Rate RR Select RR 10 to 29 RR more than 29 RR 6 to 9 RR 1 to 5 RR 0 Revised Trauma Score Explanation and Clinical Context Revised Trauma Score is a physiological scoring system created to evaluate trauma severity and predict outcomes in injured patients. It uses three fundamental clinical
Reynolds Risk Score (RRS): Comprehensive Explanation and Clinical Context The Reynolds Risk Score is a 10-year cardiovascular risk prediction model developed by Ridker PM and colleagues (2007). It estimates the probability of major cardiovascular events (myocardial infarction, ischemic stroke, or coronary revascularization) among individuals without existing cardiovascular disease or diabetes. The RRS combines tradit
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Explanation and Clinical Context This calculator estimates the volume of fetal whole blood and the number of 300 microgram vials of Rh immune globulin required after a positive Kleihauer Betke test or after counting fetal and total red blood cells on a stained smear. The calculation uses the conventional relation where the volume of fetal whole blood in milliliters equals the fetal cell percent multiplied by 50. Each
RI-AF Score: Explanation and Clinical Context The RI-AF Score is a clinical tool developed to predict the risk of recurrent atrial fibrillation (AF) following device implantation, such as pacemakers or implantable cardioverter-defibrillators (ICDs). It incorporates several clinical parameters: age, history of congestive heart failure (CHF), left ventricular (LV) hypertrophy, aortic atherosclerosis, withdrawal of ACE
RIETE Score (for VTE Recurrence): Explanation and Clinical Context The RIETE Score is a clinical tool designed to estimate the risk of recurrent venous thromboembolism (VTE) after an initial episode of deep vein thrombosis or pulmonary embolism. It incorporates patient factors such as age, sex, prior history of VTE, presence of active cancer, whether the initial VTE was unprovoked, and recent surgery or immobilizatio
Right Atrial Pressure Estimation Using IVC Diameter and Collapse Estimating right atrial pressure is an essential part of echocardiographic assessment because it directly influences the calculation of pulmonary artery systolic pressure and provides insight into right sided cardiac filling. The widely adopted method is based on the diameter of the inferior vena cava and its collapsibility with inspiration. A small ven
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Right Ventricular Apical Pacing Risk Index (RVAPRI): Explanation and Clinical Context RVAPRI is a clinical tool designed to assess the risk of adverse outcomes in patients undergoing right ventricular apical pacing. The scoring system incorporates factors such as age, left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) functional class, and QRS duration. A higher risk score indicates a greate
Right Ventricular Global Longitudinal Strain (RV-GLS): Explanation and Clinical Context RV-GLS quantifies right ventricular systolic deformation along the longitudinal axis from an RV-focused apical four-chamber view using 2D speckle-tracking. Two reporting conventions exist: a 6-segment global value that includes free wall and septum (RV-GLS), and a 3-segment free-wall-only value (RVFWLS). Because septal motion is i
References American Heart Association. Twenty twenty five Acute Coronary Syndromes Guideline. Journal of the American College of Cardiology. Twenty twenty five Zellweger M J et al. Right ventricular involvement in inferior myocardial infarction. European Heart Journal. Two thousand four Goldstein J A. Pathophysiology and management of right ventricular infarction. Current Cardiology Reports. Two thousand seven
Risk of Sudden Death in Brugada (RB Score): Explanation and Clinical Context The RB Score is a clinical scoring system designed to estimate the risk of sudden cardiac death in patients with Brugada Syndrome. It incorporates key risk factors: spontaneous Type 1 ECG, history of syncope, family history of sudden cardiac death, and inducible ventricular arrhythmias on electrophysiologic study. A total score of 0–5 points
RISK-E (Endocarditis Surgery Mortality) Score: Explanation and Clinical Context The RISK-E score is a validated risk prediction tool for estimating operative mortality in patients undergoing surgery for infective endocarditis. It uses preoperative clinical variables, including age, renal failure, NYHA class III-IV heart failure, diabetes mellitus, critical preoperative state, prosthetic valve involvement, emergency s
RISK-HF Readmission Score: Explanation and Clinical Context The RISK-HF Readmission Score is a prognostic model designed to estimate the risk of hospital readmission for patients discharged after an episode of heart failure decompensation. It utilises easily available clinical variables (such as age, prior heart failure hospitalisation, chronic kidney disease, COPD/OSA, atrial fibrillation, anaemia, diabetes mellitus