ADVERTISEMENT
Validation of a Novel Monitoring System to Measure Contrast Volume Use During Invasive Angiography
Abstract: Background. Multiple studies have demonstrated the relationship between contrast volume (CV) and the risk of acute kidney injury (AKI). Quantification of total CV is often estimated and therefore may be inaccurate. We describe validation of a novel contrast monitoring system (CMS) (Osprey Medical), which is designed to detect and display injection by injection and total CV use on a monitor system in real time. Methods. Thirty patients undergoing a coronary or peripheral angiogram were included. Ten patients underwent procedures using the CMS only and 20 underwent procedures using both the CMS and the AVERT Plus contrast modulation system (Osprey Medical). Total CV used during these cases was measured using direct measurement via a graduated cylinder (CVDM). This was compared with the CMS-reported CV and with the operator’s assessment of CV (CVPE) used during the case. Intraclass correlation coefficient (ICC) and Pearson correlation coefficient (PCC) were used for analysis and the results displayed using Bland-Altman plots. Results. Twenty-one cases were diagnostic and 9 were interventional. The ICC/PCC (confidence interval [CI]) for the comparison of CVDM to CMS and CVPE were 0.96/0.97 [CI, 0.94-0.99] and 0.89/0.90 [CI, 0.80-0.95], respectively, with a P=.01 for difference between the correlations. The average absolute difference between the CVDM and CMS readout and the CVPE was 12.0 ± 13.7 mL and 22.8 ± 15.3 mL, respectively; P=.01. Conclusions. The CMS was accurate when compared with the direct measurement of CV used. This accuracy was superior to physician estimation of CV.
J INVASIVE CARDIOL 2017;29(3):105-108. Epub 2017 February 15
Key words: contrast media, contrast-induced nephropathy, new device
The quantification of total contrast volume (CV) used during invasive angiography is an important quality metric. The graded relationship between increasing total CV and the incremental risk of acute kidney injury (AKI) has been well established.1 Guideline recommendations emphasize minimizing total CV and the prospective determination of precatheterization contrast thresholds. Actual accounting of total CV varies in practice and is often estimated rather than directly measured.2 A contrast monitoring system (CMS) utilizing a monitor screen coupled to a “Smart Syringe” has recently been developed (Osprey Medical). The Smart Syringe attaches to existing manifold connections and provides a measurement of forward injection volume, which is displayed on the monitor. The purpose of the present study was to assess the accuracy of this novel technology in comparison with directly measured CV assessment in patients undergoing coronary or peripheral angiography. We further hypothesized that the CMS would be more accurate in measuring total CV than a physician estimate.
Methods
Description of technology. The CMS monitors and displays the CV injected toward the patient in real time. The CMS also allows the input and display of a CV threshold, as determined by the physician prior to the procedure. The CMS consists of a reusable touchscreen monitor screen with embedded software that connects via a cable to a mating, single-use Smart Syringe. The Smart Syringe replaces the physician’s manifold control syringe (Figure 1). The Smart Syringe tracks the position of the syringe plunger using infrared light sensing technology. During an injection, the software embedded in the CMS monitor converts the linear movement (L) of the syringe plunger directly to CV injected, utilizing the Smart Syringe internal diameter (d) per the following equation: CV = L • π • (d2/4).
The AVERT Plus Contrast Modulation/Monitoring System consists of both the CMS and the AVERT Contrast Modulation System (AVERT). With the AVERT Plus, when an injection is performed, a portion of the injected CV is delivered to the patient and the balance is diverted away from the patient to the modulation reservoir of the AVERT. Upon completion of the injection, the diverted (saved) contrast dye is returned from the AVERT back to the Smart Syringe. The mechanism of this device has been described in detail previously.3,4 The CMS automatically subtracts the diverted CV from the total attempted CV injection delivered from the Smart Syringe. The resulting volume actually delivered to the patient is displayed on the monitor in real time along with an end of case total of CV used.
Study design. Thirty consecutive patients undergoing clinically indicated coronary or peripheral angiography were prospectively enrolled. There were no exclusions based on renal function or type of procedure (diagnostic vs interventional). Subjects either underwent angiography using only the CMS or the CMS in combination with the AVERT (ie, the AVERT Plus System). The use of the AVERT system for a particular injection was left up to the physician performing the angiogram. Care was taken to avoid admixture of saline or blood into the Smart Syringe during any of the injections.
Iodixanol (Visipaque 320; GE Healthcare) was used as the contrast media for the study. Based on prior experience, it was noted that individual bottles of 150 mL Visipaque contrast had variable volumes of starting contrast media (range, 150-160 mL). At baseline, each bottle of contrast was inverted and the meniscus of the contrast-air interface was marked. At the end of each case, saline was filled to this meniscus level and subsequently this volume of saline was measured using a graduated cylinder. If more than one bottle of contrast was used during the case, the above process was repeated for each bottle. In addition, any contrast used to prime manifold lines was collected and quantified and added to the aforementioned total volume. This value was assigned as the starting volume. Measurement of the end of case remaining volume involved complete drainage of all contrast media from the manifold tubing, injection syringe, and bottle into a graduated cylinder. This total volume represented the residual volume. The CV used during the case was calculated as starting volume – residual volume. The CV used during the case was also recorded from the CMS readout. This CV was compared with the CV amount by direct measurement (CVDM). In addition to the CVDM and CMS readout, the physician performing the angiogram was asked to estimate the total CV used during the case (CVPE). The physician was blinded to the CMS readout during and after the procedure.
The study was approved by the institutional review board of the University of Texas Health Science Center at San Antonio. The study was registered at ClinicalTrials.gov (NCT02578173).
Data analysis. The correlations of the CMS readout and physician readouts were compared to the “gold standard” in this study using the CVDM. The correlations were made using intraclass correlation coefficient (ICC) and Pearson correlation coefficient (PCC) and displayed visually using Bland-Atman plots. Tests comparing correlations, accounting for the dependence induced by comparing each method against CVDM, were based on Hittner, May, and Silver’s modification of Dunn and Clark’s z-test.5 A signed rank was used to compare the absolute average differences between the CMS and CVDM and the CMS and CVPE. SAS system software version 9.3 and (R version 3.1.2) with the (“cocor” package)6 were used for analyses. A P-value <.05 was taken to indicate statistical significance.
Results
Subject and procedural details. The baseline clinical and procedural characteristics of the 30 subjects are demonstrated in Table 1. The majority of individuals underwent diagnostic procedures (n = 21). Ten subjects underwent angiography using only the CMS, while 20 subjects underwent angiography with the AVERT Plus system (CMS and the AVERT system).
CV data. The comparison of the mean total CV as recorded by the CMS readout, CVDM, and CVPE is shown in Figure 2. The average absolute difference (± standard deviation) between the CVDM and CMS readout and the CVPE was 12.0 ± 13.7 mL and 22.8 ± 15.3 mL, respectively (P=.01). In 16 of the cases, the CMS readout was greater than the CVDM (difference = 9.5 ± 9.4 mL), and in 14 cases was lower than the CVDM (difference = -14.9 ± 17.3 mL). In 13 of the cases, the CVPE was greater than the CVDM (difference = 15.2 ± 7.5 mL), and in 17 cases was lower than the CVDM (difference = -23.5 ± 23.2 mL).
The ICC and PCC (confidence interval [CI]) for the comparison of the CVDM to the CMS and CVPE were 0.96/0.97 (CI, 0.94-0.99) and 0.89/0.90 (CI, 0.80-0.95), respectively (P=.01). The comparisons of the CVDM and the CMS and CVPE are shown in Figures 3A and 3B. Total CV as recorded by the CMS for cases using the AVERT was 102.3 ± 72.1 mL, with a mean percent contrast diversion of 22.3 ± 11.7%.
Discussion
The present study demonstrates that the CMS was accurate when compared with direct measurement of CV use. In addition, the CMS was more accurate than physician estimation of total CV. The use of this technology has potential implications to improve practice in the cardiac catheterization laboratory. Both the preprocedure estimation of a CV limit and documentation of CV used post procedure are recommended by multiple society consensus guidelines.7,8 As such, an accurate determination of CV has multiple potential clinical advantages. First, the relationship between total CV – and more specifically, CV to creatinine clearance ratio – appears to be associated with increased risk of developing AKI.9 Reflecting this relationship, AKI risk scoring systems universally incorporate some measure of CV into their algorithm.10 Guidelines also emphasize that lowering of total CV should be a goal during angiography and therefore an accurate accounting of CV is a key quality metric. Despite these recommendations, as many as 40% of respondents in a recent survey of invasive cardiologists reported not using CV limits or measuring total CV used at the end of a case.2
The current methods for total CV vary widely in catheterization laboratories and include physician, nurse, or technologist estimation or using the number of angiographic images to guide approximation. The meticulous technique of direct CV quantification used in the present study is not practical in daily practice. The technique we have described is time consuming and also not ideal in catheterization laboratories, which use contrast-saver systems and therefore may not change bottles containing residual contrast in between cases.
Second, an intraprocedural running total of CV use has the potential to provide real-time feedback to physicians. Such data could help operators with adjusting number of injections to minimize total contrast dose and aid in decisions regarding staging versus ad hoc treatment of coronary or peripheral lesions. Whether such feedback actually improves outcomes or impacts operator behavior will need to be studied in a prospective manner. This conceptual framework, as described for CV, currently exists for radiation dose – which is displayed in real time in modern angiography suites and has been shown to acutely impact physician decisions in the catheterization laboratory.11
Study limitations. The study was relatively small and based on a single operator’s experience. The CVPE therefore could vary widely in practice. The current CMS (monitor used with the Smart Syringe) measures forward injection, therefore contamination with saline or blood may lessen the accuracy of the device. Although the CMS method was accurate, it was not perfect, which may reflect limitations of the device or also of the gold-standard CVDM technique employed in the study.
Conclusion
This study demonstrates that the CMS method of total CV assessment was accurate and outperformed physician estimation of CV used during angiography.
References
1. Gurm HS, Seth M, Mehran R, et al; for the Blue Cross Blue Shield of Michigan Cardiovascular C. Impact of contrast dose reduction on incidence of acute kidney injury (AKI) among patients undergoing PCI: a modeling study. J Invasive Cardiol. 2016;28:142-146.
2. Prasad A, Sohn A, Morales J, et al. Contemporary practice patterns related to the risk of acute kidney injury in the catheterization laboratory: results from a survey of Society of Cardiovascular Angiography and Intervention (SCAI) cardiologists. Catheter Cardiovasc Interv. 2016 Jun 17 (Epub ahead of print).
3. Prasad A, Ortiz-Lopez C, Kaye DM, et al. The use of the AVERT system to limit contrast volume administration during peripheral angiography and intervention. Catheter Cardiovasc Interv. 2015;86:1228-1233.
4. Kaye DM, Stub D, Mak V, Doan T, Duffy SJ. Reducing iodinated contrast volume by manipulating injection pressure during coronary angiography. Catheter Cardiovasc Interv. 2014;83:741-745.
5. Hittner JB, May K, Silver NC. A Monte Carlo evaluation of tests for comparing dependent correlations. J Gen Psychol. 2003;130:149-168.
6. Diedenhofen B, Musch J. Cocor: a comprehensive solution for the statistical comparison of correlations. PLoS One. 2015;10:e0121945.
7. Naidu SS, Aronow HD, Box LC, et al. SCAI expert consensus statement: 2016 best practices in the cardiac catheterization laboratory: (endorsed by the Cardiological Society of India, and Sociedad Latino Americana de Cardiologia Intervencionista; affirmation of value by the Canadian Association of Interventional Cardiology-Association Canadienne de Cardiologie D’intervention). Catheter Cardiovasc Interv. 2016;88:407-423. Epub 2016 May 2.
8. Bashore TM, Bates ER, Kern MJ, et al. American College of Cardiology/Society for Cardiac Angiography and Interventions clinical expert consensus document on cardiac catheterization laboratory standards: summary of a report of the American College of Cardiology task force on clinical expert consensus documents. Catheter Cardiovasc Interv. 2001;53:281-286.
9. Zhao JB, Liu Y, Wu DX, et al. Contrast volume to cystatin C-based glomerular filtration ratio predicts the risk of contrast-induced nephropathy after cardiac catheterization. Angiology. 2016 May 10 (Epub ahead of print).
10. 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;44:1393-1399.
11. Christopoulos G, Papayannis AC, Alomar M, et al. Effect of a real-time radiation monitoring device on operator radiation exposure during cardiac catheterization: the radiation reduction during cardiac catheterization using real-time monitoring study. Circ Cardiovasc Interv. 2014;7:744-750.
From the 1University of Texas Health Science Center at San Antonio, Department of Medicine, Division of Cardiology, San Antonio, Texas; and 2NAMSA, Minneapolis, Minnesota.
Funding: This work was supported by the Freeman Heart Association Endowment for Cardiovascular Disease, Osprey Medical, and UT Health Science Center San Antonio.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Prasad discloses research support from Osprey Medical. Dr Bailey discloses consultant fees from Osprey Medical. The remaining authors report no disclosures regarding the content herein.
Manuscript submitted October 18, 2016, final version accepted November 2, 2016.
Address for correspondence: Anand Prasad, MD, FACC, FSCAI, RPVI, Department of Medicine, Division of Cardiology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990. Email: prasada@uthscsa.edu
