Beyond the Mehran Risk Score: Predictive Value of Total Ischemic Time for Contrast-Induced Nephropathy in ST Segment Elevation Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention.

Background:

Contrast-Induced Nephropathy (CIN) remains one of the most significant complications following primary percutaneous coronary intervention (PPCI) in patients presenting with ST-segment elevation myocardial infarction (STEMI). The traditional Mehran Risk Score utilizes static baseline parameters (such as hypotension, IABP, CHF, age, anemia, diabetes, contrast volume, and baseline eGFR) to stratify CIN risk. However, it omits the duration of acute myocardial ischemia. Prolonged total ischemic time (the interval from symptom onset to first balloon inflation/device placement) triggers severe systemic inflammatory cascades, hemodynamic instability, and transient renal hypoperfusion, which may independently increase susceptibility to contrast-induced acute kidney injury.

Objectives:

To evaluate the independent predictive value of Total Ischemic Time for Contrast-Induced Nephropathy (CIN) in acute STEMI patients undergoing primary PCI.

To investigate whether integrating total ischemic duration into the classic Mehran Risk Score enhances its predictive performance, discrimination, calibration, and risk reclassification capacity.

Methods & Procedure:

This prospective observational validation cohort study will recruit consecutive adult STEMI patients presenting to Assiut University Heart Hospital undergoing primary PCI within 12 hours of symptom onset. Total ischemic time (symptom-to-balloon time) will be precisely documented upon presentation. Baseline laboratory tests including serum creatinine, blood urea nitrogen (BUN), complete blood count (CBC), and blood glucose will be drawn prior to PCI. Serum creatinine will be re-evaluated at 24, 48, and 72 hours post-PCI to detect CIN (defined as an absolute increase in serum creatinine of ≥ 0.5 mg/dL or a relative increase of ≥ 25% from baseline within 48-72 hours post-contrast administration).

Statistical modeling will compare the performance of the classic Mehran Risk Score against a modified model incorporating total ischemic time using Area Under the Receiver Operating Characteristic Curve (AUROC), Net Reclassification Improvement (NRI), and Integrated Discrimination Improvement (IDI).

Inclusion criteria

• Inclusion Criteria:

• Patients aged >=18 years at the time of presentation.
• Definitive diagnosis of acute ST-segment elevation myocardial infarction (STEMI) presenting within 12 hours of symptom onset, characterized by typical ischemic symptoms (e.g., retrosternal chest pain) and electrocardiographic criteria: persistent ST-segment elevation >=1 mm in >=2 contiguous limb leads, or >=2 mm in >=2 contiguous precordial leads (V2-V3 thresholds: >=2.5 mm in men <40 years, >=2.0 mm in men >=40 years, and >=1.5 mm in women), or a validated new or presumably new left bundle branch block (LBBB).
• Selection for immediate mechanical reperfusion via emergency primary percutaneous coronary intervention (PPCI) according to current guidelines.
• A reliable and verifiable chronological timeline regarding the exact onset of chest pain or ischemic symptoms to ensure precise calculation of the total ischemic duration.
• Willingness to participate, demonstrated by signed, informed consent obtained from the patient or an authorized family representative prior to data collection under approved institutional protocols.

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Exclusion criteria

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• Pre-existing end-stage renal disease (ESRD) requiring long-term peritoneal dialysis or hemodialysis, or an admission baseline eGFR <15 mL/min/1.73m2.
• Prior exposure to iodinated contrast media within the past 7 days, or scheduled elective contrast procedures within the subsequent 72 hours.
• Intentional pre-procedural administration of structured, high-volume intravenous fluid hydration regimens specifically designed to prevent contrast nephropathy (e.g., sodium bicarbonate protocols), which would confound baseline renal kinetics.
• Known active treatment with high-potency nephrotoxic drugs within the 48 hours prior to admission (e.g., cisplatin, high-dose aminoglycosides, amphotericin B).
• Active pregnancy, ongoing breastfeeding, or severe non-cardiac co-morbidities associated with a life expectancy <30 days (e.g., advanced terminal malignancies)