Mehran Score for Post-PCI Contrast-Induced Nephropathy

The Mehran score for CIN risk

Since contrast-induced nephropathy is the third most common cause of hospital acquired renal impairment, risk stratification scores such as the Mehran score can be used for clinical and investigational purposes and aid clinicians in decision making about managing procedure-related risk factors as well as the use of renal protective measures in patients at high risk of CIN.

The 8 risk factors used in the Mehran score to stratify risk of CIN (and their weightings) are described in the table below:

* The original study includes serum creatinine (as a dichotomous variable) as an alternative to eGFR, and adds 4 points for Creatinine >1.5 mg/dL. eGFR was chosen instead as a more accurate measure of renal function than creatinine alone.

The Mehran score cannot be used in patients with pre-existing end-stage renal disease on dialysis or patients with contrast exposure within 1 week of the index procedure.

The table below summarizes the risk of post-PCI contrast induce nephropathy and percentage of cases requiring dialysis, based on the Mehran CIN risk scores:

About the original study

Following a study on a total of 8,357 patients, Mehran et al. developed a simple risk score that cumulates the risk factors and can be used to determine the risk of contrast-induced nephropathy (CIN), following percutaneous coronary intervention (PCI).

5,571 were part of the development dataset, considered candidate univariate predictors of CIN (increase ≥25% and/or ≥0.5 mg/dl in serum creatinine at 48 h after PCI vs. baseline).

The study identified eight variables through multivariate logistic regression, each being assigned a weighted integer based on the odds ratio. The sum of the integers gave out the total risk score.

The study showed that the rate of CIN increased exponentially with increasing risk score (Cochran Armitage chi-square, p < 0.0001).

The risk score was then validated in the 2,786 patients dataset and demonstrated good discriminative power (cstatistic = 0.67).

Subsequent validations

One of the validation studies (by Wi et al.) analysed a dataset of 1,041 acute myocardial infarction (AMI) patients undergoing percutaneous coronary intervention (PCI). Patients were categorized into 4 groups according to risk scores: low (≤ 5, n = 596), moderate (6-10, n = 265), high (11-15, n = 111), and very high (≥16, n = 69).

148 patients went on to develop CIN (out of which 68 presented with persistent renal dysfunction). Patients in higher-risk groups experienced significantly more MACCE and mortality 2 years after PCI.

The Mehran score was found to consistently predict CIN with persistent renal dysfunction and long-term clinical outcomes in the AMI patient cohort.

CIN risk factors, prevalence and prevention

CIN is most commonly defined as an increase ≥0.5 mg/dL (or ≥25%) in pre-PCI serum creatinine at 48 -72 hours after intravenous contrast administration of iodinated solution. However, for kidney impairment to be attributed to post PCI, it should not be related to any other identifiable cause of nephropathy such as nephrotoxins, hypotension, urinary obstruction, or atheromatous emboli.

CIN is usually a transient, self-limiting form of acute renal failure, with serum creatinine levels peaking in 3-5 days and gradually returning to baseline levels within 7-10 days.

The incidence of CIN after PCI varies between 0 and 24% depending on patient's risk factors but with higher incidence after emergency PCI. In patients with normal renal function, incidence is low (0-5%) but increases to 12-24% in patients with pre-existing renal impairment.

Development of CIN is associated with a longer hospital stay, an increased morbidity and mortality. Treatment of CIN is mainly supportive, consisting mainly of fluid and electrolyte management, although dialysis may be required in some cases.

Patient related factors include pre-existing chronic kidney disease, advanced age, diabetes, peripheral heart failure, peripheral vascular disease, hypertension, and a left ventricular ejection fraction (LVEF) of less than 40%.

Procedure related risk factors include the use of high osmolarity contrast agents or large volumes, intra-arterial administration or repeat procedures, especially within a short period of time.

Accounting for individual patient’s CIN risk factors, may help clinicians weigh the benefits of contrast based diagnostics against the risk of CIN and further complications.

With respect to CIN prevention, especially in high risk patients, repeated exposure to CM should be avoided, along with minimizing the volume of CM and avoiding activation of renal vasoconstriction.

The concomitant use of diuretics or nephrotoxins (e.g. nonsteroidal anti-inflammatory drugs (NSAIDs), cytotoxic drugs, and aminoglycosides) should be avoided.

References

Original reference

Mehran R, Aymong ED, Nikolsky E, et al. A simple risk score for prediction of contrast-induced nephropathy after percutaneous coronary intervention: development and initial validation. J Am Coll Cardiol. 2004; 44(7):1393-9.

Validation

Wi J, Ko YG, Shin DH, et al. Prediction of Contrast-Induced Nephropathy With Persistent Renal Dysfunction and Adverse Long-term Outcomes in Patients With Acute Myocardial Infarction Using the Mehran Risk Score. Clin Cardiol. 2013; 36(1):46-53.

Sgura FA, Bertelli L, Monopoli D, Leuzzi C, Guerri E, Spartà I, Politi L, Aprile A, Amato A, Rossi R, Biondi-Zoccai G, Sangiorgi GM, Modena MG. Mehran contrast-induced nephropathy risk score predicts short- and long-term clinical outcomes in patients with ST-elevation-myocardial infarction. Circ Cardiovasc Interv. 2010; 3(5):491-8.

Raingruber B, Kirkland-Walsh H, Chahon N, Kellermann M. Using the Mehran Risk Scoring Tool to Predict Risk for Contrast Medium–Induced Nephropathy in Patients Undergoing Percutaneous Angiography. Crit Care Nurse 1 February 2011; 31 (1): e17–e22.