Harrells C index
Reading File
Searching the Web
Harrell's concordance index survival analysis definition censoring
Searching PubMed
concordance index survival analysis
Harrell's C-index (concordance index) measures how well a survival model discriminates between people who experience an event earlier versus later.
It is the probability that, for a usable pair of patients, the patient predicted to be at higher risk actually has the event first.
[
C = \frac{\text{concordant pairs} + 0.5 \times \text{tied prediction pairs}}{\text{comparable pairs}}
]
Interpretation
- 1.00: perfect discrimination
- 0.50: no better than random ordering
- < 0.50: predictions are ordered in the wrong direction
- For example, C = 0.72 means that in about 72% of comparable patient pairs, the model correctly ranks who has the earlier event.
In survival data
Harrell's C-index accounts for right censoring by using only comparable pairs:
- If patient A has an observed event before patient B's observed time, the pair can generally be compared.
- If the earlier observed time is censored, the true order of event times is unknown, so that pair is excluded.
For a Cox proportional-hazards model, a larger predicted linear predictor or hazard typically means higher risk and therefore a shorter predicted survival time. The prediction is concordant if that patient actually experiences the event first.
Limitation
With substantial censoring, Harrell's C-index may be biased because it discards non-comparable pairs and can depend on the censoring pattern. In such settings, Uno's C-index, which uses inverse-probability-of-censoring weighting, is often considered a useful alternative. A survival-model performance review discusses this limitation, and this methods paper gives the formal comparable-pair definition.
What is HOMA-IR
Reading File
Searching the Web
HOMA-IR formula fasting glucose insulin interpretation official medical source
Searching PubMed
HOMA-IR insulin resistance
Finding Sources
Reading File
HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It is a calculated estimate of how resistant the body is to insulin, using fasting blood glucose and fasting insulin levels.
Formula
If glucose is in mg/dL:
[
\text{HOMA-IR}=\frac{\text{fasting insulin (µU/mL)} \times \text{fasting glucose (mg/dL)}}{405}
]
If glucose is in mmol/L:
[
\text{HOMA-IR}=\frac{\text{fasting insulin (µU/mL)} \times \text{fasting glucose (mmol/L)}}{22.5}
]
Example: fasting insulin 12 µU/mL and glucose 90 mg/dL:
[
\frac{12 \times 90}{405}=2.67
]
Meaning
- A higher HOMA-IR generally indicates greater insulin resistance.
- A lower result generally indicates better insulin sensitivity.
- It is mainly used in research and sometimes in clinical metabolic assessment. The reference standard for measuring insulin resistance is the euglycemic insulin clamp; HOMA-IR is a simpler surrogate measure. Fuster and Hurst's The Heart, 15th Edition, p. 1226.
There is no universal diagnostic cut-off. Thresholds differ by population, laboratory assay, age, ethnicity, and clinical setting. Values around 2 to 2.5 or higher are sometimes used as possible indicators of insulin resistance, but a result should not be interpreted alone or used to diagnose diabetes.
For formula background, Diabetes Care's HOMA review gives the standard mmol/L-based equation.
Framingham risk score
Reading File
Searching the Web
Framingham Risk Score cardiovascular disease calculator variables 10 year official
Searching PubMed
Framingham risk score cardiovascular risk
Framingham Risk Score (FRS) is a cardiovascular risk prediction tool. It estimates a person's likelihood of developing cardiovascular disease over the next 10 years, based on data from the Framingham Heart Study.
Common inputs
The exact inputs depend on which Framingham equation is used, but commonly include:
- Age and sex
- Total cholesterol and HDL cholesterol
- Systolic blood pressure
- Whether blood-pressure treatment is being used
- Current smoking
- Diabetes status
Some versions use body mass index instead of cholesterol measurements.
What it predicts
Different Framingham models predict different outcomes, such as:
- General cardiovascular disease (CVD): may include coronary heart disease, stroke, heart failure, peripheral arterial disease, and cardiovascular death.
- Coronary heart disease (CHD): angina, myocardial infarction, or coronary death.
- Hard CHD: myocardial infarction or coronary death only.
So, a reported Framingham score should always specify which outcome it estimates.
Interpretation
If the 10-year result is, for example, 15%, it means an estimated 15 in 100 chance of the defined cardiovascular outcome within 10 years, assuming the individual resembles the population used to develop the model.
A commonly used CHD categorization is:
- Low risk: <10%
- Intermediate risk: 10% to 20%
- High risk: >20%
These cutoffs are not interchangeable with all current treatment guidelines. In the United States, lipid-treatment decisions often use the ACC/AHA pooled cohort equations rather than Framingham, depending on the clinical context.
The Framingham Heart Study CVD equation provides sex-specific coefficients and uses age, BMI or lipids, systolic BP and treatment status, smoking, and diabetes.
SCORE 2
Reading File
Searching the Web
SCORE2 cardiovascular risk estimation age 40 69 low moderate high very high risk regions ESC 2021 guideline
Searching PubMed
SCORE2 cardiovascular risk prediction
SCORE2 is the European Society of Cardiology (ESC) tool for estimating an apparently healthy person's 10-year risk of a first fatal or non-fatal atherosclerotic cardiovascular disease (ASCVD) event, specifically myocardial infarction or stroke.
It was introduced in the 2021 ESC prevention guidelines and updates the older SCORE model, which predicted cardiovascular death only.
Who it is for
- Adults aged 40 to 69 years
- No established cardiovascular disease, diabetes, or major inherited lipid disorder
- Mainly calibrated for European populations
For people aged 70 years or older, use SCORE2-OP (Older Persons).
Inputs
- Age
- Sex
- Smoking status
- Systolic blood pressure
- Non-HDL cholesterol
- Country/region cardiovascular-risk category
Age-specific 10-year risk categories
| Age | Low to moderate | High | Very high |
|---|---|---|---|
| <50 years | <2.5% | 2.5% to <7.5% | ≥7.5% |
| 50-69 years | <5% | 5% to <10% | ≥10% |
| ≥70 years, SCORE2-OP | <7.5% | 7.5% to <15% | ≥15% |
Risk thresholds rise with age because an identical absolute risk has different clinical meaning in a younger versus older person.
Key limitation
SCORE2 is calibrated to four European risk regions. It may not be well calibrated for people living outside Europe unless a locally adapted version is used. It is also not intended for people already at very high risk, such as those with established ASCVD or diabetes with major risk factors.
The ESC SCORE2 overview provides the age-based thresholds, and the ESC calculator page links to HeartScore.
MACCE risk
Reading File
Searching the Web
MACCE major adverse cardiac and cerebrovascular events definition clinical trials
Searching PubMed
MACCE major adverse cardiac cerebrovascular events definition
MACCE stands for Major Adverse Cardiac and Cerebrovascular Events.
It is not one fixed risk score. It is a composite clinical outcome used in cardiovascular studies and after procedures such as PCI, CABG, or major surgery.
Common MACCE components
Usually includes:
- All-cause or cardiovascular death
- Myocardial infarction (heart attack)
- Stroke
Depending on the study, it may also include:
- Repeat revascularization, such as repeat PCI or CABG
- Target-vessel revascularization
- Hospitalization for heart failure
- Other cardiovascular events
Important point
The exact definition must be checked in the specific study or risk model. For example, one study may define MACCE as death + MI + stroke, while another adds repeat revascularization. Therefore, MACCE event rates from different studies cannot automatically be compared.
In perioperative research, a common definition is in-hospital death, acute MI, or ischemic stroke, as described in this perioperative MACCE study.
SYNTAX score
Reading File
Searching the Web
SYNTAX score coronary artery disease lesion complexity calculation official consensus
Searching PubMed
SYNTAX score coronary artery disease
SYNTAX score is an angiographic scoring system that quantifies the anatomical complexity of coronary artery disease (CAD). It is mainly used in patients with left-main or multivessel CAD when deciding between:
- PCI: percutaneous coronary intervention, such as stenting
- CABG: coronary artery bypass graft surgery
How it is calculated
On coronary angiography, each lesion with:
- ≥50% diameter stenosis
- in a coronary vessel ≥1.5 mm diameter
is scored. Points reflect the lesion's location and complexity, including:
- Left-main involvement
- Proximal LAD disease
- Number of diseased vessels/lesions
- Bifurcation or trifurcation lesion
- Chronic total occlusion
- Severe tortuosity
- Heavy calcification
- Thrombus
- Long lesion
- Diffuse small-vessel disease
The individual lesion scores are added to give the total SYNTAX score.
Usual categories
| SYNTAX score | Anatomical complexity |
|---|---|
| 0-22 | Low |
| 23-32 | Intermediate |
| ≥33 | High |
A higher score means more extensive and technically complex disease, and usually a higher chance of adverse outcomes after PCI.
Clinical use
In general:
- Low score: PCI and CABG may have more comparable outcomes, depending on clinical factors.
- High score, especially complex multivessel or left-main disease: CABG is often favored because PCI may have greater subsequent risk of repeat revascularization and some adverse events.
Treatment should not be based on the anatomical score alone. The Heart Team also considers symptoms, ventricular function, diabetes, kidney disease, surgical risk, vessel suitability, and patient preference.
SYNTAX Score II
SYNTAX Score II combines the anatomical SYNTAX score with clinical factors such as age, creatinine clearance, left-ventricular ejection fraction, sex, COPD, peripheral arterial disease, and presentation. It estimates mortality with PCI versus CABG to support individualized treatment selection.
The official SYNTAX calculator includes the lesion-definition tutorial and calculators.
GRACE
Reading File
Finding Sources
Searching the Web
GRACE risk score acute coronary syndrome variables in hospital 6 month mortality official guideline
Searching PubMed
GRACE score acute coronary syndrome
GRACE score stands for Global Registry of Acute Coronary Events score. It is a validated risk-stratification tool for patients with acute coronary syndrome (ACS), including NSTEMI, unstable angina, and STEMI.
It estimates the risk of:
- In-hospital death
- Death after discharge, commonly at 6 months
- In newer versions, risk over longer follow-up periods
Variables used
The GRACE score uses eight admission variables:
- Age
- Heart rate
- Systolic blood pressure
- Serum creatinine
- Killip class, reflecting heart-failure severity
- Cardiac arrest at presentation
- ST-segment deviation on ECG
- Elevated cardiac biomarkers, such as troponin
Higher age, tachycardia, hypotension, renal impairment, heart failure, cardiac arrest, ST deviation, and raised troponin raise the estimated risk.
Clinical use
It helps determine the urgency of invasive management in NSTE-ACS:
- GRACE score >140 indicates high risk and is commonly used to support an early invasive strategy, if clinically appropriate. Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice, lines 3333-3345.
- A lower score does not rule out ACS. It only estimates prognosis after ACS has been diagnosed or is strongly suspected.
Difference from other scores
- GRACE: predicts mortality risk in confirmed/suspected ACS.
- TIMI score: a simpler ACS risk score, often used at the bedside.
- HEART score: mainly used in emergency chest-pain evaluation to estimate short-term major cardiac-event risk.
The GRACE predictors include age, heart rate, systolic BP, Killip class, cardiac arrest, creatinine, ST-segment deviation, and cardiac enzymes, as described in this European Heart Journal analysis.
MINOCA
Reading File
Finding Sources
Searching the Web
MINOCA definition diagnostic criteria causes cardiac MRI AHA ESC
Searching PubMed
MINOCA diagnosis management
Reading File
MINOCA means Myocardial Infarction with Non-Obstructive Coronary Arteries.
It is a working diagnosis, not a final disease diagnosis. The patient has a true acute MI, but coronary angiography does not show an obstructive coronary stenosis.
Diagnostic criteria
MINOCA requires all three:
-
Evidence of acute myocardial infarction
- Rise/fall in troponin, with symptoms, ECG changes, imaging evidence, or coronary thrombus consistent with MI.
-
No obstructive coronary artery disease on angiography
- Usually defined as <50% stenosis in all major epicardial coronary arteries.
-
No alternative clear explanation at the time of angiography.
- Conditions such as myocarditis and Takotsubo syndrome may mimic MI and should be actively assessed and excluded before confirming MINOCA.
Possible causes
- Plaque disruption or erosion without severe narrowing
- Coronary vasospasm
- Coronary microvascular dysfunction or microvascular spasm
- Spontaneous coronary artery dissection (SCAD)
- Coronary embolism or thrombosis
- Supply-demand mismatch, such as severe anemia, tachyarrhythmia, or hypoxia
Evaluation
After angiography, testing is aimed at identifying the mechanism:
- Echocardiography
- Cardiac MRI, especially to distinguish infarction from myocarditis or Takotsubo syndrome
- Intracoronary imaging, such as OCT or IVUS, for plaque disruption or SCAD
- Coronary vasoreactivity/functional testing in selected patients
Treatment
Treatment is cause-specific:
- Vasospasm: calcium-channel blocker and nitrates
- Plaque-mediated MI: secondary prevention such as antiplatelet therapy and statin, as clinically appropriate
- SCAD: often conservative management
- Embolic cause: investigate and treat the embolic source
MINOCA is not benign and needs cardiology follow-up. Braunwald notes that it is a heterogeneous syndrome requiring further evaluation, with mechanisms including vasospasm, microvascular dysfunction, embolism/thrombosis, SCAD, and supply-demand mismatch. Braunwald’s Heart Disease, 12th ed., lines 231-249. The ESC MINOCA overview provides the current criteria and diagnostic approach.
Chronic microvascular dysfunction and chronic coronary syndrome ... relation between them
Reading File
Searching the Web
2024 ESC chronic coronary syndromes coronary microvascular dysfunction relationship INOCA guideline
Searching PubMed
coronary microvascular dysfunction chronic coronary syndrome
Chronic coronary syndrome (CCS) is the broad clinical umbrella for stable or recurrent myocardial ischemia, including chronic angina. It is not limited to large-vessel obstructive coronary artery disease.
Coronary microvascular dysfunction (CMD) is one important mechanism that can cause CCS.
Relationship
| Term | Meaning |
|---|---|
| CCS | A chronic clinical syndrome of myocardial ischemia or angina, with or without obstructive epicardial coronary artery disease |
| CMD | Abnormal function of the coronary microcirculation, the small coronary arterioles that regulate myocardial blood flow |
| INOCA | Ischemia with no obstructive coronary arteries |
| ANOCA | Angina with no obstructive coronary arteries |
CMD can impair vasodilation and/or cause abnormal microvascular constriction. Consequently, blood flow cannot increase enough during exercise, stress, or tachycardia, leading to myocardial ischemia and angina despite an angiogram showing no flow-limiting stenosis in the main coronary arteries.
Therefore:
[
\text{CMD} \rightarrow \text{myocardial ischemia/angina} \rightarrow \text{CCS phenotype, often ANOCA/INOCA}
]
CMD occurs in two CCS settings
-
CCS without obstructive epicardial CAD
- CMD may be the primary explanation for chronic angina or demonstrable ischemia.
- This is often called microvascular angina, an INOCA endotype.
-
CCS with obstructive epicardial CAD
- CMD can coexist with a stenosis.
- It may worsen ischemia, explain persistent symptoms after PCI/CABG, and contribute to poorer prognosis.
- Treating the large-vessel stenosis alone does not necessarily correct microvascular dysfunction.
Main mechanisms of CMD
- Reduced ability of arterioles to dilate, causing reduced coronary flow reserve
- Endothelial dysfunction
- Microvascular spasm
- Structural remodeling or rarefaction of small vessels
- Raised microvascular resistance
Contributors include hypertension, diabetes, dyslipidemia, smoking, obesity, chronic kidney disease, systemic inflammation, and sometimes no clear conventional risk factor.
Diagnosis
A normal coronary angiogram does not exclude ischemic heart disease. In a person with suspected CCS and non-obstructive arteries, CMD may be assessed by:
- Stress PET, cardiac MRI, or Doppler echocardiography to measure impaired myocardial blood flow or coronary flow reserve
- Invasive coronary function testing, including coronary flow reserve, index of microcirculatory resistance, and acetylcholine testing to identify microvascular or epicardial spasm
Treatment principle
Management is based on the identified mechanism:
- Aggressive control of cardiovascular risk factors
- Statin and ACE inhibitor/ARB when indicated
- Antianginal therapy tailored to the endotype
- Calcium-channel blockers for vasospastic disease
- Beta-blockers are often considered for impaired vasodilator reserve without vasospasm, while they may be avoided in isolated vasospastic syndromes
Thus, CMD is a pathophysiological mechanism, whereas CCS is the clinical syndrome. CMD is a major cause of chronic angina and ischemia in people with non-obstructive coronary arteries, and it can also coexist with classic obstructive CAD. The 2024 ESC CCS guideline overview specifically expands the CCS framework to include ANOCA-INOCA.
Intracranial arterial stenosis and extra cranial arterial stenosis
Reading File
Finding Sources
Searching the Web
AHA guideline intracranial atherosclerotic stenosis extracranial carotid vertebral artery stenosis diagnosis treatment
Searching PubMed
intracranial extracranial arterial stenosis
Searching Images
diagram intracranial and extracranial carotid and vertebral arteries anatomy
Arterial stenosis means narrowing of an artery, most often from atherosclerotic plaque. The difference is the artery's location in relation to the skull.
| Feature | Intracranial arterial stenosis | Extracranial arterial stenosis |
|---|---|---|
| Location | Inside the skull | Outside the skull, usually neck arteries |
| Common vessels | Intracranial internal carotid, middle cerebral, anterior cerebral, vertebral, basilar, posterior cerebral arteries | Carotid bifurcation/proximal internal carotid, common carotid, vertebral artery origin |
| Main consequence | Ischemic stroke/TIA in the artery's brain territory | Embolic or low-flow ischemic stroke/TIA, often from carotid plaque |
| Main imaging | CTA/MRA, transcranial Doppler, catheter angiography if needed | Carotid duplex ultrasound first, CTA/MRA for confirmation or treatment planning |
| Revascularization role | Usually not initial treatment. Medical management is first-line; intracranial angioplasty/stenting is reserved for selected cases | Symptomatic severe carotid stenosis may benefit from carotid endarterectomy or, in selected patients, carotid stenting, in addition to medical treatment |
Intracranial arterial stenosis
This is narrowing in the arteries within the cranial cavity. Atherosclerosis is common, though vasculitis, dissection, moyamoya disease, or other arteriopathies can also cause narrowing.
For symptomatic intracranial atherosclerotic stenosis, treatment generally emphasizes:
- Antiplatelet therapy, sometimes short-term dual antiplatelet therapy in appropriate patients
- High-intensity statin therapy and LDL lowering
- Blood-pressure, diabetes, smoking, diet, and exercise management
Routine intracranial stenting is generally not first-line because of procedural stroke risk. The AHA/ASA guideline notes that identifying symptomatic intracranial disease supports aggressive anti-atherosclerotic treatment and often dual antiplatelet therapy; CTA and MRA can reliably exclude high-grade disease in appropriate settings. AHA/ASA secondary prevention guideline
Extracranial arterial stenosis
This is narrowing in arteries before they enter the skull, most commonly at the carotid bifurcation or proximal internal carotid artery in the neck. It can release plaque material or thrombus that embolizes to the brain, causing TIA, amaurosis fugax, or ischemic stroke.
Management includes:
- Intensive vascular risk-factor treatment for everyone
- Carotid endarterectomy in suitable patients with recently symptomatic, significant carotid stenosis
- Carotid artery stenting for selected patients, depending on anatomy, age, surgical risk, and local expertise
The benefit of intervention depends on whether the stenosis is symptomatic, the degree of narrowing, timing after symptoms, and procedural risk. For recently symptomatic carotid stenosis, there is no established benefit from endarterectomy when internal-carotid narrowing is <50%. AHA/ASA guideline evidence summary
Simple way to remember
- Extra-cranial = neck arteries, especially carotid disease. Surgery or stenting may be considered in selected severe symptomatic cases.
- Intra-cranial = brain arteries. Medical therapy is the usual initial approach; stenting is much more selective.
Both can coexist and both raise stroke risk. New sudden facial droop, arm weakness, speech difficulty, vision loss, severe imbalance, or sudden severe headache requires emergency assessment.
Low extremity arterial disease
Reading File
Finding Sources
Searching the Web
2024 ACC AHA guideline lower extremity peripheral artery disease diagnosis ABI management
Searching PubMed
lower extremity peripheral artery disease treatment
Searching Images
diagram lower extremity peripheral artery disease ankle brachial index arterial anatomy
Lower-extremity arterial disease (LEAD), also called lower-extremity peripheral artery disease (PAD), is narrowing or blockage of arteries supplying the legs, most commonly due to atherosclerosis.
It is a manifestation of systemic vascular disease. A person with LEAD also has a higher risk of myocardial infarction, stroke, and cardiovascular death.
Main clinical presentations
| Presentation | Typical features |
|---|---|
| Asymptomatic PAD | Reduced pulses or abnormal ankle-brachial index, without typical leg symptoms |
| Intermittent claudication | Reproducible calf, thigh, buttock, or foot discomfort on walking that resolves within minutes of rest |
| Chronic limb-threatening ischemia (CLTI) | Rest pain, non-healing ulcer, gangrene, or tissue loss due to severely impaired arterial perfusion |
| Acute limb ischemia | Sudden arterial blockage causing abrupt pain, pallor, pulselessness, coldness, numbness, or weakness. This is an emergency. |
Usual sites of disease
- Aortoiliac arteries: buttock or thigh claudication
- Femoropopliteal arteries: calf claudication
- Tibial and pedal arteries: foot ischemia, ulcers, poor wound healing, especially in diabetes
Risk factors
- Smoking
- Diabetes mellitus
- Hypertension
- Dyslipidemia
- Chronic kidney disease
- Older age
- Established coronary, carotid, or cerebrovascular disease
Diagnosis
The first test is usually the ankle-brachial index (ABI):
[
\text{ABI}=\frac{\text{highest ankle systolic pressure}}{\text{highest brachial systolic pressure}}
]
Typical interpretation:
- 1.00 to 1.40: normal
- 0.91 to 0.99: borderline
- ≤0.90: PAD
- >1.40: non-compressible, calcified arteries, often in diabetes or CKD. Toe-brachial index or other perfusion testing may be needed.
Duplex ultrasound, CT angiography, or MR angiography is used to define anatomy if revascularization is being considered. The 2024 ACC/AHA PAD guideline summary recommends resting ABI to establish the diagnosis when history or examination suggests PAD.
Treatment
For most patients, care includes:
- Stop smoking
- Structured or supervised walking exercise
- Statin therapy and control of blood pressure and diabetes
- Antiplatelet therapy when indicated
- Foot inspection and wound care, particularly in diabetes
- Cilostazol may improve walking distance in selected patients with claudication, but is avoided in heart failure
- Revascularization by endovascular treatment or bypass surgery for lifestyle-limiting claudication despite medical and exercise therapy, or urgently for CLTI to preserve the limb
Red flags
Urgent assessment is needed for:
- Sudden painful, cold, pale, numb, or weak leg
- New foot ulcer, black tissue, or gangrene
- Rest pain in the foot, especially at night
- A non-healing wound in a person with diabetes
The 2024 guideline divides LEAD into asymptomatic disease, chronic symptomatic PAD, chronic limb-threatening ischemia, and acute limb ischemia, emphasizing early diagnosis to reduce cardiovascular events and amputation risk. AHA guideline announcement
This is a shared conversation. Sign in to Orris to start your own chat.