DOPPLER ULTRASOUND SCREENING FOR SIGNIFICANT CAROTID ARTERY STENOSIS IN CARDIAC SURGERY PATIENTS, PRESENTING TO HAYATABAD MEDICAL COMPLEX, PESHAWAR, PAKISTAN

Background: This study aimed to determine the frequency of significant carotid artery stenosis by Doppler Ultrasound screening in patients undergoing open heart surgery. Method: From January 2019 to April 2019, 125 consecutive patients who were booked for open heart surgery, in Hayatabad Medical Complex Peshawar Pakistan, were included in this study. Adult patients aging more than 18years were studied irrespective of the planned cardiac surgical procedure, while pediatric and adolescent patients below the age of 18years were excluded. Using Mindray® DC 70 Color Doppler Ultrasound Scanner, significant carotid artery stenosis was determined by a Radiologist as stenosis of more than 50 % luminal diameter of the carotid artery under study. Results: We studied 250 carotid arteries of 125 patients (87 males and 38 females with age range 19 to 80 years (mean 57.47 years). Significant stenosis was found in 13 patients (10.40 %) with slight male preponderance (7:6). Conclusion: Doppler ultrasound study is a good modality, free of radiation hazards for screening carotid arteries in patients undergoing open Heart surgery. Patients with significant carotid artery stenosis on Doppler ultrasound study may be objectively confirmed by subsequent CT carotid angiography. However, further studies are required to assess the efficiency of Doppler ultrasound study in carotid artery stenosis in comparison to CT carotid angiography. Routine Doppler ultrasound screening in adult cardiac surgical patients can identify significant carotid artery stenosis and can help in subsequently reducing the risk of operative stroke in patients undergoing open heart surgery.

Early detection of CAS with screening CUS can decrease incidence of stroke in patients undergoing open heart surgery.
This study aimed to determine the presence and frequency of significant carotid artery stenosis in patients undergoing Open Heart Surgery.

METHODS
The study aimed to determine the presence and frequency of significant carotid artery stenosis in patients undergoing Open Heart Surgery. We conducted a single institution prospective study from January 2019 to April 2019, in Medical Teaching Institute Hayatabad Medical Complex (MTI-HMC), Peshawar. During this course, we included all adult patients more than 18 years old, who had consulted cardiac surgeon for any type of open heart surgery including CABG, valve replacement, congenital defects, or mixed/complex cardiac diseases. Pediatric and adolescent patients below the age of 18 years were excluded from the study.
The carotid Doppler ultrasound was performed by a Radiologist using Mindray ® DC 70 Color Doppler ultrasound scanner. Patients were put in supine position with the head tilted to the opposite side of the carotid artery being examined. Proper carotid preset was selected on the machine and Scan started with high resolution cross sectional gray scale view of the CCA from its origin to its bifurcation and continued up the ICA and ECA as far as their visible extent in the neck. This was then followed by longitudinal view of the same arteries. The vessels were examined for presence of any anatomical variations, increased IMT, wall calcification, plaque, stenosis or occlusion. Color Doppler technique was employed to assess flow status, luminal filling along with any flow void areas, direction of blood flow and color aliasing. Spectral Doppler was used to measure peak systolic velocities, end diastolic velocities and ICA/CCA PSV Ratio. Percent stenosis was calculated by measuring the size of plaque and diameter of the remainder patent lumen along with presence of color aliasing at the stenotic site and measurement of peak systolic velocity, End Diastolic velocity and ICA to CCA PSV ratio. (Fig 1). The carotid Doppler scan also included examination of the vertebral arteries. Data was collected and stored in computer software from where it was retrieved upon completion of the study. A diagnosis of CAS made and its severity graded as per the Society of Radiologists in Ultrasound criteria according to which the patients were classified into the groups as shown in Table 1. [7] The results were discussed with the referring cardiac surgeon.

RESULTS
In the three months period, a total of 125 consecutive patients were included in the study, of which 87 were males (69.60 %) while 38 were female (30.40 %).  Finally, no patient in the group 1 had significant carotid stenosis amongst a total of 13 (10.40%) patients. Only 1 (7.69%) patient was in group 2 while 6 (46.15%) were in group 3 and 6 (46.15%) were in group 4. These results are summarized in Table-3 & Table-4.

DISCUSSION
Atherosclerosis involves large and medium sized arteries such as carotid, coronary, and peripheral arteries, and is one of the leading cause of death. [8] Cina et al reported that significant carotid stenosis greater than 50% was associated with stroke. [9] CUS is a valuable and cost effective screening imaging tool to identify significant carotid disease and improve the quality-adjusted life years. [10] In a study by da Rosa and Portal, prevalence of CAS  [11] Mahmoudi et al. included 878 patients in their study before isolated CABG and found that 13% had a carotid stenosis >75%. [12] Rath et al. stated a high prevalence of CAS as 84.5% whereas Cirilo et al reported 61.6% in their study. [13,14] Shirani et al. reported the prevalence of CS >60% as 6.6% and 12.5% in patients who were 65 years and older. [15] The prevalence of severe ACAS in the general population was reported by Weerd et al to range from 0% to 3.1%, and its prevalence increases with age and with risk factor levels. [16] Hyuk et al determined 15.2% of severe ICA stenosis in patients with Peripheral Arterial disease by routine screening CUS. These results implicate 15.2% such patients can be protected from stroke by carotid endarterectomy. [17] Yun et al found that critical ICA stenosis was more common in patients with coronary artery disease. [18] Kayani et al., conducted a cross sectional study, where 140 patients were evaluated. Insignificant CAS (<50% lesion) was found in 56.6% of patients, while 10.7% of patients had significant carotid stenosis (>50% lesion), and only 8.5% of patients had critical (>70%lesion) carotid stenosis. [19] In our study, the prevalence of significant CAS was found to be 10.40 % which is lower than some of the above cited references. The reason for this difference may be that there was no specific selection criteria in our study however in most of the studies mentioned above, specific group of patients were selected and studies for example Da Rosa and Portal [11] studied prevalence of CAD in patients undergoing elective CABG and all patients undergoing other type of cardiac surgery were excluded. daWeerd et al [16] studied prevalence of severe ACAS in general population and its relation with the risk factors. While Hyuk et al [17] studied patients with peripheral arterial disease with which CAD is a common association. Another reason for this difference may be small sample size and results of study on a larger sample size may agree with other studies. We also found that a large proportion of patients i.e 12/13 (92.30%) with significant CAS were above 40 years of age.
Carotid artery stenosis is a major cause of ischemic stroke and consequently high morbidity and mortality especially during cardiac surgery, and the efficacy of carotid endarterectomy in stroke prevention in patients with asymptomatic high-grade ICA stenosis is well established. [19][20][21][22][23] Hence it becomes quite reasonable to screen all the adult patients with carotid Doppler ultrasound studies to exclude significant carotid artery disease prior to their cardiac surgical procedure.
Limitations of the study 1. Risk factors were not analyzed in this study. 2. This is a single center study and results consulted with one cardiac surgeon.

CONCLUSION
Pre-operative screening carotid Doppler ultrasound is important and provides valuable information about significant carotid artery disease. So we recommend the use of this readily available technique in routine preoperative practice as the standard of care in all adult patients undergoing open heart surgery, especially those older than 40 years of age. Doppler ultrasound study is a good modality for screening and it is free of radiation hazards. Patients with significant carotid artery disease on Doppler ultrasound study may be objectively confirmed by subsequent CT carotid angiography. However, further studies are required to assess the efficacy of Doppler ultrasound study in carotid artery disease in comparison to CT carotid angiography.
Routine carotid arteries Doppler ultrasound screening identifies significant carotid artery disease and can help in planning to subsequently reduce the risk of operative stroke in patients undergoing open heart surgery.