A BaleDoneen clinical review of our brief experience with CardioHealthIMT imaging.
The purpose of this statement is to provide our impressions of the CardioHealth carotid IMT imaging system from our perspective, based on a decade of clinical use of CIMT. CardioHealth recently introduced their machine into the US market. This has generated lots of excitement and interest from many of our BaleDoneen graduates. We began receiving numerous emails and phone calls asking for our opinion about this new device. Before responding we acquired some hands on experience with the equipment. We want to thank the individuals associated with CardioHealth who allowed us to utilize their machine in our clinic. Our perspective is free from bias and our intent is simply to share our thoughts. We are not giving a recommendation for or against its use. We lack the expertise to define the characteristics of the machine itself, the parameters for which it sets protocols and the durability of the machine. We simply took the opportunity to examine the report and interact with the trained, in-house sonographer that performed the testing.
Many clinicians will be excited about this ultrasound equipment due to its automatic image identification software. The implication given to our sonographer by the CardioHealth sales team was that it would be easy to train an operator to position the transducer in the correct spot to get the IMT image. Once in the right location, the machine will freeze the image and take the IMT measurement at the point in the cardiac cycle when the diameter of the artery is at its smallest –close to end-diastole. According to our certified vascular sonographer, it still requires a trained technician to position the transducer. In addition, she frequently had to freeze the image manually as the machine failed to recognize a satisfactory image. The CCA IMT is determined by this single image of the far wall. Their system has the capability of acquiring multiple measurements at different angles. If that is done, it will select the single largest measurement to represent the CCA IMT. Their final interpretation of risk is based on the greatest measurement from the left or right carotid. Per our experience, most IMT protocols suggest getting at least 3 angles of the far wall. Some protocols also include incorporating observations of the near wall, as there are individuals who have thicker IMT in the near wall. Utilizing a technique that utilizes a single angle assumes uniformity of IMT circumferentially which is not true. Therefore, even with this automated device, a trained sonographer should obtain multiple measurements from several angles to derive the final measurement felt to represent the greatest CCA IMT value for either the right or left carotid artery. The potential advantage of the CardioHealth system is acquiring the measurement after locking into a stable segment of IMT across several cardiac cycles. This may be more accurate than manually averaging several measurements from each angle used. However, if only a few images are utilized one may significantly under or over estimate CCA IMT.
The presence of carotid plaque is a strong predictive element of CIMT testing. CardioHealth does not have an automated plaque detector. This still requires a well-trained sonographer who follows strict protocols for proper scanning and reporting of ‘plaque’. With the CardioHealth machine the sonographer/clinician has the opportunity to place the word “absent” or “present” under the word “Plaque”, but there is no way to quantify the plaque. As we have long known from the work of Drs. Gene Bond, Zaccaro and Baldassarre, the size of the plaque carries some lifetime predictability of CV event risk. CardioHealth’s system does not possess a mechanism for manually measuring plaque thickness. The presence or absence of calcium in the plaque also carries some risk predictability. The CardioHealth machine does not measure this factor, but a well-trained sonographer may write into the report their impression of echogenicity of the plaque. The position of the plaque is left to the subjective outlining on a carotid drawing by the sonographer/clinician. A digital image is not saved, so it would be difficult to make any future comparisons of plaque in an individual patient.
CardioHealth’s failure to generate saved digital images is a significant drawback in terms of being able to make multiple measurements on site or to re-measure in a remote location by a trained reader. Most companies performing CIMT create digital images which can be re-measured on site and can also be sent to trained readers ‘off-site’ for their interpretation of the images. CardioHealth’s inability to do this is a significant issue which decreases confidence in the reliability of the IMT measurement and plaque report. This failure to capture data also interferes with the ability to compare serial CIMT measurements in the same patient.
Generation of a report requires the sonographer to enter various parameters such as lipid values, blood pressure, diabetes status, smoking status, age and gender. From this entry a Framingham Score (FRS) is created on the report. We must question the accuracy of this calculation as we performed a FRS score on numerous patients tested and found our results were always dramatically different from theirs. We also feel having the FRS on the IMT report is distracting. Our method makes a clear distinction between atherosclerosis structure versus atherosclerosis risk factors. We believe the report would be more impactful for the patient, if it just addressed the carotid artery findings.
Their report provides an IMT Percentile graph/image with a percentile arrow representing the patient’s result. No reference is given for the data from which the graph is created and no clinical meaning is provided with the image. The graph also fails to include disease (plaque). Their report separates the left and right mean CCA IMT measurements. They then utilize the greater value to determine the percentile of risk compared to the patients’ age, gender and ethnicity.
We have long embraced carotid IMT imaging as a valid and reproducible tool to follow disease over time. We anticipate much excitement to the upcoming publication of Baldassarre’s IMPROVE trial. Dr. Baldassarre’s early presentation on his research supports the opportunity to follow disease over time in the individual patient. As Dr. Baldassarre eluded during his presentation at the SAIP meeting (April 2011), several measurements with multiple angles are necessary to effectively follow disease over time in the individual patient. If Dr. Baldassarre’s work is validated, the CardioHealth report would need to generate and record multiple measurements from at least three angles. However, with the CardioHealth system those images could only be measured once by a single reviewer and they could not be digitally saved. This introduces a significant limitation for monitoring disease over time in an individual patient.
To avoid bias from the creators of CardioHealth, our comments have not been filtered through them. We welcome the opportunity to learn more from CardioHealth and we appreciate their desire to bring carotid IMT to the clinical forefront. We are also very appreciative of their wiliness to provide us with a machine to use in a real clinical setting. At this point, we conclude that the CardioHealth carotid IMT report and imaging protocol approach mitigates the tremendous value and integrity of carotid intima media thickness testing.
Amy Doneen and Bradley Bale