Coronary Artery Calcifications (CAC) are highly prevalent, usually asymptomatic and underestimated among maintenance hemodialysis patients (MHP) [1]. Furthermore CAC are strongly associated with diminished survival in MHP [1]. Identification of these high risk patients is important and might improve outcome [2]. Vascular calcification occurring both in the intima and the media of the vessel wall could have different consequences: Intima calcification leads to vascular occlusion whereas media calcification leads to vascular stiffening [1,3]. The aim of this study was the assessment of CAC in MHP by Multi Slice Cardio Tomography(MSCT) and their prevalence and risk factors [4-6].

Study Population

Cross-sectional study was conducted in the period from January to March 2013, including 49 MHP in Dialysis Unit of the First Medicosurgical Hospital in Agadir, Morocco. Inclusion criteria were chronic hemodialysis 3 times a week, age ≥ 18 years, hemodialysis vintage ≥ 6 months. Patients with previous coronarography with stents were excluded from study. In patients with a heart rate ≥ 65 beats per minute. Oral b-blockers (metroprolol 50 or 100 mg, single dose, 1 hour before examination) were administered.

Multi Slice Cardio Tomography (MSCT) Protocol

Detection and quantification of coronary calcifications were made by a high-speed scanner helical cardiac acquisition in retrospective mode without injection of contrast was performed from the carina to diaphragm with a slice thickness of 0.6 mm during a single inspiratory breathe hold with ECG synchronization. Forty to 64 slices were obtained for each acquisition.

MSCT Data Analysis

This technique allowed the visualization of the entire length of the coronary tree. The images obtained were interpretable when considered to not containing artifacts related to movement or heartbeat. Various reconstructions in different planes of space were then performed. A calcified coronary plaque was interpreted when comprised of at least three contiguous pixels having a density of ≥ 130 Hounsfield units. The total volume and the density of calcifications were assessed at the epicardial coronary arteries (left coronary artery (LCA) and right coronary artery (RCA)), the Circumflex Artery (Cx A), the Anterior Inter Ventricular Artery (AIVA), the Diagonal Artery (DA) and Posterior Inter Ventricular Artery (PIVA). The Calcium Coronary Agatston Score (CCAS) was achieved by software that incorporates density calcifications, by multiplying the volume of calcification to a weighted density coefficient. The data were interpreted by a single radiologist trained to this technique and uninformed by clinical and biological information (Figure 1). Patients were classified into 2 groups: (1) No or Moderate calcification with CCAS= 0–400; and (1) Severe calcification with CCAS >400.

Figure 1: Multi Slice Cardio Tomography

Demographic data

Age, sex, causal nephropathy, dialysis vintage, diabetes, hypertension and average serum levels of calcium, phosphorus, intact parathyroid hormone (iPTH), C-reactive protein (CRP), Low Density Lipoprotein (LDL) cholesterol, during six months.

Statistics SPSS 10.0 statistical software was used for statistical analysis. All variables were assessed by Kolmogrov-Smirnov test and were not normally distributed. Continuous variables were expressed as median ± (25^th, 75^th percentiles). Categorical variables were expressed as frequency and proportions. Non parametric test (Mann-Withney test) was used to find the relationship between CACS (<400 or >400) and other variables. The significance level was set at 0.05. Spearman test was used to assess correlation between high CACS and others variables.

Forty nine patients were enrolled in the study (26 men and 23 women), median age was 56.47 (57.00-65.00) years, and the median duration of dialysis was 80.43 (57.00-65.00) months.

Diabetes mellitus was the most frequent etiology of end stage renal disease (40.8%). Baseline demography and clinic characteristics of study patients are summarized in Table 1.

The median CCAS was 22, 00 (00-201.5), 38 patients (77.6%) showed no or moderate coronary calcification (CCAS=0-400) and severe calcification (CCAS >400) were found in 11 patients (22.4%). Positive correlation exists between Severe calcification (CCAS >400) and conventional cardiovascular risk factors such age (0.02), male gender (p=0.05), diabetes (p=0.03) and calcemia (p=0.03). Comparison between these two patients groups are summarized in Table 2.

Table 1: Baseline demography and clinic characteristics of study patients. Continuous variables are expressed as median ± (25^th, 75^th percentiles)

Table 2: Comparison between two patients groups No or Moderate calcification with CCAS= 0–400 and Severe calcification with CCAS >400. CCAS: Calcium coronary Agatston score. Non parametric test (Mann-Withney test) was used for comparison of Continuous variabl *Categorical variable were compared by Khi-deux test. The significance level was set at 0.05

The AIVA was the first site of calcification (69.4%) followed by the RCA (36.7%) and the Cx A (30.6%). Calcifications were present simultaneously in two coronary arteries in 66% of cases. The number of calcified arteries increased with age (r=0.396).

Vascular calcifications are an important cardiovascular risk factor in MHP [7]. Coronary artery calcifications are highly frequent and extensive disease in MHP population [8-11]. Detection of such calcifications may be helpful in clinical practice [12-14]. Multi Slice Cardio Tomography (MSCT) is a new non-invasive and sensitive image technique for assessment of density and volume of calcification at multiple sites and allows quantitative scoring of vascular calcification using calcium scores [15]. In this study 69.4% of MHP showed coronary calcifications at the IVA artery. The number of affected coronary arteries increased with age.

High calcium score may be associated with high risk of future adverse coronary events [1]. Several reviews support the predictive value of quantifying coronary artery calcification and the utility of screening for coronary calcification to stratify moderate-high risk individuals for future adverse coronary events [16-18]. However the precise contribution of intimal and medial calcification to the coronary artery calcification score seen on MSCT or Electron Beam Cardio-Tomgraphy among MHP is not well established [16]. Different reports showed correlation between severe coronary calcification score and age, diabetes and higher calcemia among MHP [16-18].

Forty-seven percent of CCAS in this study were classified beyond the 80th percentile rank. This means that only 20% of matched general population could have a CCAS superior to MHP. The CCAS performed by MSCT could add an additional prognostic value to traditional risk factors for coronary artery disease. High percentile ranks CCAS matched for age and sex could be a powerful predictor of myocardial infarction and death.

In conclusion MSCT could be a sensitive and non-invasive method to assess and quantify the progression of coronary artery calcification among MHP [16].