Identification and Validation of a Prediction Model for CARDIOvascular Events

Background: Cardiovascular risk stratification is a cornerstone of modern preventive medicine, particularly in patients with multiple comorbidities, where risk estimation is inherently complex. Existing tools such as SCORE2 and the CUORE project provide important insights into cardiovascular risk but are limited in their ability to account for the interplay of multiple coexisting conditions.

Objective: The primary aim of this prospective cohort study is to develop and validate a novel cardiovascular risk prediction model specifically tailored for patients with at least two concomitant chronic diseases. Secondary objectives include comparing the predictive performance of the new model with that of SCORE2 and the CUORE project, and quantifying the incidence of venous thromboembolism (VTE), bleeding, and overall mortality in this high-risk population.

Methods: This is a prospective, monocentric, observational cohort study with an expected duration of 144 months. Patients ≥18 years with at least two of a predefined list of chronic conditions will be recruited at the Thrombosis Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS. Clinical, laboratory, and instrumental data will be collected at baseline and during annual follow-up visits, for a maximum follow-up period of 10 years. Major cardiovascular events, VTE, bleeding, and mortality will be recorded. A Fine \& Gray competing risks model will be applied for risk modeling, with subsequent validation in an independent cohort. Model discrimination and calibration will be evaluated using time-dependent ROC curves and calibration plots.

Expected Outcomes: The study aims to generate a robust and clinically applicable cardiovascular risk prediction model that better reflects the complexity of patients with multimorbidity. The model is expected to improve individualized prevention strategies and optimize resource allocation in clinical practice.

Ethical Considerations: The study will be conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. Informed consent will be obtained from all participants.

Introduction Cardiovascular risk assessment is of fundamental importance in medicine, especially given the high prevalence of cardiovascular diseases and their association with a wide range of comorbidities. Cardiovascular diseases are a major cause of morbidity and mortality worldwide, and correct risk assessment is essential for prevention, early diagnosis and optimal management of patients. Cardiovascular risk stratification allows physicians to identify high-risk subjects who could benefit from targeted preventive interventions, thus improving clinical outcomes and reducing healthcare costs associated with acute cardiovascular events.

Currently available cardiovascular risk assessment tools, such as SCORE2 and the CUORE project, represent significant steps towards preventive and personalized medicine. However, despite their usefulness, these scores have some intrinsic limitations that reduce their effectiveness in considering the entire spectrum of risk factors, especially in patients with multiple comorbidities.

SCORE2 (Systematic Coronary Risk Evaluation 2) is an evolution of the original SCORE model, developed to improve the estimation of cardiovascular risk in several European populations2. This tool takes into account variables such as age, sex, blood pressure, total cholesterol and cigarette smoking to calculate the 10-year risk of a fatal cardiovascular event. Despite the update compared to the previous model, SCORE2 continues to be based on a limited number of risk factors and may not accurately reflect the clinical complexity of patients with multiple conditions, such as diabetes, obesity, chronic kidney disease and other comorbidities.

The CUORE project, developed in Italy, aims to provide a cardiovascular risk assessment tool specific to the Italian population. It also uses traditional risk factors such as age, sex, blood pressure, cholesterol, diabetes and smoking to estimate the 10-year risk of major cardiovascular events, such as myocardial infarction and stroke. Although the CUORE project represents an important contribution to preventive medicine, its limitations are similar to those of SCORE2: a partial view of risk factors that does not always capture the complexity of patients with multiple comorbidities.

The importance of cardiovascular risk estimation lies in the possibility of adopting effective and personalized preventive strategies. However, the accuracy of these tools is crucial for the success of preventive measures. Comorbidities, such as diabetes mellitus, hypertension, dyslipidemia, obesity, chronic kidney disease and neoplastic diseases, are often present simultaneously in patients and can interact with each other, amplifying cardiovascular risk in a non-linear way. Current tools tend to consider these factors in isolation, failing to adequately represent the complex interaction between different comorbidities.

To address these limitations, it is necessary to develop new cardiovascular risk models that can integrate a greater number of variables and consider the interactions between different risk factors.

The aim of this prospective cohort study is therefore to evaluate the incidence of cardiovascular events in a population consisting of patients with more than one comorbidity, evaluating the possible determinants of cardiovascular risk in this context, in order to create a cardiovascular risk prediction model applicable in patients with multiple comorbidities.

OBJECTIVES OF THE STUDY Primary objective The primary objective of the study is the identification and validation of a cardiovascular risk prediction model in patients with at least two concomitant diseases.

Secondary objectives

The secondary objectives of the study are:

* Comparison of the predictive value of the identified model with respect to currently validated risk prediction models, such as SCORE2 or the CUORE project.
* Description of the incidence rate of venous thromboembolism, bleeding and mortality in patients with at least two concomitant diseases.

STUDY DESIGN A prospective, drug-free, device-free, single-center, non-profit cohort study. The study involves recording data regarding the patient's medical history, instrumental and blood tests performed according to current clinical practice, collected through review of the personal clinical documentation provided during the enrollment and follow-up visit and through examination of the Trakcare medical record. The expected duration of the study is 144 months. This duration includes an estimated enrollment period of 2 years and a maximum follow-up period of 10 years. The study will begin after approval by the Ethics Committee.

This study protocol has been designed and will be conducted in accordance with the principles established by the Good Clinical Practice (GCP) guidelines and in compliance with the Declaration of Helsinki and the current guidelines regarding observational studies.

Population The study population will consist of patients already affected by at least two pathologies at the time of the visit, prospectively recruited at the time of the first outpatient visit at the U.O.S.D. Percorso Trombosi of the I.R.C.C.S. Fondazione Policlinico Universitario Agostino Gemelli in Rome

Inclusion criteria

* Positive history of at least two of the following pathologies: arterial hypertension, dyslipidemia, type 2 diabetes mellitus, ischemic heart disease, heart failure with reduced or preserved ejection fraction, atrial fibrillation, cardiac valvular disease, cerebral vasculopathy, obesity, chronic obstructive pulmonary disease, chronic kidney disease, neoplasia (with the exception of localized basal cell or squamous cell skin neoplasms), active or previous venous thromboembolism.
* Age greater than 18 years.
* Expression of Informed Consent. Exclusion criteria
* Inability or unwillingness to perform follow-up visits.
* Life expectancy \< 3 months.

Screening phase Before enrolling in the study, patients will undergo a medical examination in person. During this visit, anamnesis will be collected and an objective examination will be performed, aimed at finding signs and symptoms of cardiovascular diseases or risk factors. If diseases are found that are not adequately managed from a medical point of view, the patient will be referred to the appropriate Medical Specialist. All patients will be given recommendations on the correct lifestyle to follow and on how to reduce cardiovascular risk factors according to current Guidelines.

Follow-up Follow-up begins after enrollment and ends in the event of an expression of the will to discontinue participation in the study or in the event of death. The maximum overall duration of the follow-up is 10 years.

Follow-up modalities The study includes at least one in-person medical evaluation every 12 months for a maximum follow-up duration of 10 years. Depending on the needs of the individual patient, the patient will be re-evaluated when appropriate according to clinical judgment. Patients will also be evaluated through an in-person or telematic medical visit in the event of a cardiovascular event. In the event of changes in the clinical picture, patients may contact the investigators at the email addresses or telephone numbers indicated in the documentation.

Outcome variables

The diagnosis of a major cardiovascular event will be defined as:

* New episode of acute coronary syndrome (STEMI, NSTEMI, unstable angina) diagnosed by electrocardiographic examination and/or diagnostic coronary angiography and/or plasma biomarkers (TnI, CK-MB).
* New episode of transient ischemic attack (TIA) diagnosed by a neurologist specialist.
* New episode of ischemic stroke diagnosed by CT of the skull without or with contrast medium and/or MRI of the brain and/or selective angiography of the cerebral vessels.
* New episode of heart failure requiring hospitalization and/or intravenous diuretic therapy.
* New episode of acute ischemia of the lower limb diagnosed by CT angiography of the lower limbs and/or selective arteriography of the lower limbs vessels and/or arterial color Doppler ultrasound.
* New lower limb revascularization procedure and/or surgical amputation of the lower limbs due to worsening of the symptoms of obliterating arterial disease of the lower limbs.
* Death from cardiovascular causes.

The diagnosis of venous thromboembolism (VTE) will be assigned if documentation is obtained by venous echo-color Doppler examination and/or CT and/or MRI with contrast medium and/or lung scintigraphy with ventilation/perfusion.

In patients who die during follow-up, the clinical documentation and/or autopsy results, if available, will be reviewed to assess the presence of a possible diagnosis of fatal pulmonary embolism and/or cardiovascular event.

Bleeding will be assigned if the criteria for major or non-major clinically relevant bleeding according to the definitions of the International Society on Thrombosis and Haemostasis ISTH5 are met through the acquisition and review of the clinical documentation related to the bleeding event.

ENDPOINTS Primary endpoints

• Incidence rate of cardiovascular events (acute coronary syndrome, coronary revascularization, ischemic or hemorrhagic stroke, acute ischemic stroke of the lower limbs or need for revascularization of the lower limbs, deep vein thrombosis or pulmonary embolism).

Secondary endpoints

* Incidence rate of venous thromboembolism (pulmonary embolism, deep vein thrombosis of the lower limbs, deep vein thrombosis at unusual sites).
* Incidence rate of major bleeding and clinically relevant non-major bleeding according to ISTH definitions5.
* Mortality rate.

STATISTICAL METHODS Sample size calculation Cardiovascular diseases are the main cause of death and hospitalization in almost all European countries and account for almost 40% of all deaths6. In the population aged 35-70 years, the estimated incidence rate of stroke in Italy is 3.4/1000 person-years in men and 0.9/1000 person-years in women7, while the incidence rate of acute coronary events is 2.9/1000 person-years in men and 1.25/1000 person-years in women8; the annual incidence of cardiovascular or cerebrovascular events in the general population has therefore been estimated to be 0.6%9.

The sample size of this study was therefore identified based on a weighted average incidence of major cardiovascular events, estimated in light of the above-mentioned evidence equal to 3% over an average follow-up of 60 months, and using the criterion of the minimum number of events per predictive variable equal to 10. A sample of approximately 1,600 patients in the derivation cohort was therefore considered sufficient for the determination of a risk model that includes up to 5 predictive variables.

The derivation and validation of the model will be based on two consecutive prospective cohorts, in which two thirds of the study participants will be enrolled in the model derivation cohort (n = 1,600) and one third (n = 800) will instead be assigned to the subsequent independent validation cohort. The total number of patients enrolled in the study will therefore be 2,400 participants.

Statistical analysis A Fine \& Gray model will be used for survival analysis and the study of the association between prognostic factors and the onset of cardiovascular events, taking into account death as a competing risk. The variables that will present an association in the univariate analysis with p\<0.10 will be selected for the development of the risk score model. In order to reduce the risk of so-called overfitting, the model will be identified through a bootstrap approach. The risk model will subsequently be validated in an independent validation cohort, consisting of 800 patients. The discriminatory power of the derived risk prediction model will be evaluated using the time-dependent receiver operating characteristic (ROC) curve and the relative area under the ROC curve (AUC). In the validation cohort, the calibration of the model will be evaluated, defined as the agreement between the risk of events predicted by the model itself and the observed one. The calibration will be evaluated graphically through a calibration curve, with calculation of the relative calibration slope. The ratio between observed and expected events (observed/expected ratio, O/E) will also be calculated.

The analyses will be conducted with the statistical software R (R,cran).

INFORMED CONSENT All subjects enrolled in the study will have to sign an informed consent (attached) and a consent to the processing of personal data (attached). All patients will be invited to participate voluntarily in the study. They will be explained the purpose and follow-up methods envisaged by the study. The patient will be given the opportunity to ask questions and receive satisfactory and clear answers.

ETHICAL CONSIDERATIONS The study will be conducted according to the Guidelines of Good Clinical Practice and the principles of the Declaration of Helsinki. This is an observational study and any prescription of drugs or tests is completely independent of the study, at the discretion of the attending physician, in line with current clinical practice. No costs to the Regional or National Health Systems are envisaged by the study.

DATA MANAGEMENT All data will be entered, in pseudonymized form, in a database specifically prepared on the REDCap® (Research Electronic Data Capture) web application. To guarantee anonymity, each patient will be assigned a unique identification code.

DATA OWNERSHIP The data is owned by Fondazione Policlinico Universitario A. Gemelli IRCCS.

CONFLICT OF INTEREST The investigators declare that they have no conflicts of interest related to the study protocol.

Eligibility Criteria:
Inclusion Criteria:

* History of at least two of the following conditions: arterial hypertension, dyslipidemia, type 2 diabetes mellitus, ischemic heart disease, heart failure with reduced or preserved ejection fraction, atrial fibrillation, cardiac valvular disease, cerebrovascular disease, obesity, chronic obstructive pulmonary disease, chronic kidney disease, neoplasia (except localized basal cell or squamous cell skin neoplasms), active or previous venous thromboembolism.
* Age greater than 18 years.
* Expression of Informed Consent.

Exclusion Criteria:

* Unable or unwilling to perform follow-up visits.
* Life expectancy \< 3 months.