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Advanced Cardiac Imaging for the Internist

Advanced Cardiac Imaging for the Internist. Matthew Newman MD FACC LCDR MC USN. Disclosures . Financial Disclosures: None (much to my wife’s dismay)

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Advanced Cardiac Imaging for the Internist

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  1. Advanced Cardiac Imaging for the Internist • Matthew Newman MD FACC • LCDR MC USN

  2. Disclosures • Financial Disclosures: None (much to my wife’s dismay) • The views expressed in this lecture are those of the author and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.

  3. Objectives • Understand how radiation exposure is reported, the relative doses associated with certain studies and the relative risks of exposure • Understand the utility of coronary calcium scoring (CAC) in 2011 • Understand some of the indications and limitations of coronary CT angiography (CCTA) • Understand the major indications for Cardiac MRI

  4. Outline • Radiation Basics • What is the role of CAC? • What is the role of CCTA for daignosis and prognosis? • What is the role of Cardiac MRI?

  5. Radiation Concerns “The FDA began looking into problems with CT scanning in October after patients at Cedars-Sinai Medical Center in Los Angeles reported losing hair or skin redness. The hospital last month said 260 patients were exposed to excess radiation, up from prior reports of 206.”

  6. Imaging Decision Making = Clinical Decision Making • “An individualized assessment of potential risks and benefits of each imaging procedure is required that incorporates the patient's age and gender, clinical presentation, the health risks implied by the tentative diagnosis for which imaging is to be performed, and the types of imaging modalities that are appropriate to address the clinical question at hand.”

  7. Radiation Basics • The effective dose (E, mSv), estimates of the risk of biologic detriment from a partial body exposure to ionizing radiation that allows comparisons between studies • There is no measurable physical gold standard for E. • Given the complex modeling and many assumptions involved with the estimation of E, E should generally be reported as ranges, not at specific values with decimal precision

  8. Are we “ CT Happy?” • The highest proportion of the collective dose of non-therapeutic medical radiation (49 percent) in 2006 was related to CT • Use increased by 10 - 11 percent per year from 1993 (18.3 million studies) to 2006 (62 million). • Nuclear medicine studies represented 26 percent of the collective dose in 2006. • The use of nuclear medicine studies increased over fourfold from 7.6 million in 1982 to an estimated 18.1 million in 2006. • The highest increase in utilization was related to cardiac imaging. • In 2005, 57% nuclear medicine visits (increased from 1 percent in 1973) and 85 % of the collective dose received from nuclear medicine studies Health Phys. 2008;95(5):502.

  9. Comparative Doses • Avg annual background radiation in the US is approx 3 mSv (range 1 to 10 mSv) • Radiation dose received during a six-hour commercial airline flight approx 0.03 mSv

  10. Radiation in Typical Cardiac Procedures • The mean duration of fluoroscopy in EP intevntional procedures was 41 minutes in one report, with a range of 15 to 67 minutes. • A typical procedure resulted in a total effective dose of 8.3 mSv per hour of fluoroscopy. • Mean fluoroscopy longer for paroxysmal atrial fibrillation than for common atrial flutter or accessory pathway ablation: • 57 versus 20 to 22 minutes in one report  and 130 versus 30 and 17 minutes in another. • Patient-specific factors can also affect radiation dose. • 85 patients undergoing AF ablation, obese patients received more than twice the effective radiation dose of normal-weight patients (mean 39 versus 15 mSv). Circulation. 2001;104(1):58 JACC 2007;50(3):234.

  11. Radiation in Cardiac CT:True or False • In CVCT, examinations performed for CAC impart a lower dose than examinations performed for coronary CT angiography (CCTA). • Among the multidetector row scanners (MDCT or MSCT) used for CCTA, scanners with a higher number of detector rows or "slices" (4 in 1999, 16 in 2003, 64 in 2005, and most recently as many as 320) typically impart a higher radiation dose FALSE FALSE

  12. Patients often get more than one test . . . • Retrospective cohort study of 1097 consecutive patients undergoing radionuclide myocardial perfusion imaging (rMPI) • During an approximately 20 year period, the patients underwent a median of 15 procedures involving radiation exposure. • Of these, a median of 4 were high dose procedures (≥3 mSv) including 1 (mean, 1.8) rMPI study per patient. The cumulative estimated effective dose from all medical sources exceeded 100 mSv in 31.4 percent of patients. Einstein AJ, et al. JAMA 2010; 304:2137.

  13. Appropriateness Criteria “An appropriate imaging study is one in which the expected incremental information, combined with clinical judgment, exceeds the expected negative consequences by a sufficiently wide margin for a specific indication that the procedure is generally considered acceptable care and a reasonable approach for the indication.”

  14. What is the role of Calcium Scoring (CAC) these days? • Use a calcium score to screen patients with moderate (intermediate) Framingham risk • Positive CAC scans indicate incremental risk • Alters therapeutic goal (LDL, BP, etc) • Identify patients who do not need further cardiac evaluation (scores of zero) • Track Progression of Atherosclerosis non-invasively • Improve Compliance (Adherence)

  15. St Francis Heart StudyCAC score = 0, 10 year risk <1% Cannot make a lower risk assessment on any other single screening tests 10x more likely to suffer an event with CAC > 100

  16. CAC to “Reclassify”Heinz Nixdorf Recall Study JACC 2010 • CAC independent predictor of risk, and helpful in re-classifiyng risk 62 % down classified and 14 % up classifiedCRP only able to reclassify 10%

  17. CAC to “Reclassify”Rotterdam Heart study JACC 2010

  18. Treatment reduced low-density lipoprotein cholesterol by 39% (p < 0.0001), while reducing clinical endpoints by 30% (6.9% vs. 9.9%), and MI/ Death by 44% • Event rates were more significantly reduced in participants with baseline calcium score >400 (8.7% vs. 15.0%, p=0.046 [42% reduction])

  19. New Guidelines

  20. New Guidelines

  21. Appropriateness Criteria

  22. CAC: Final Points • Event free survival higher in non progressors in all cohorts of calcium score • Typically < 1 mSV, Mammogram 0.7 or 0.8 mS • Cost of CAC: $96.45, Mammo $101.70 per CMS • Problems: • 12% interscan variability • Inability to scan and evaluate soft plaque • Does not evaluate stenosis

  23. CCTA: Evolving Technologies • The radiation dose for this study was 0.84mSv, which is comparable with the dose from a CXR Eur Heart J 2010;31:340

  24. CCTA: Evolving Technologies • MDCT technology is evolving continuously and rapidly. Most acquire at least 64 slices (also known as rows) simultaneously with a collimation of 0.6 mm with a temporal resolution of approximately 167 msec • The newest single-source MDCT scanners can acquire 256 or 320 slices with each gantry rotation. • With dual source/dual energy MDCT scanners reduce temporal resolution by 50 percent to 83 msec • In a feasibility study,(Circulation 2009;120:867–75.) CCTA in 30 patients scheduled for clinically indicated invasive coronary angiography (CA). • 320-detector row CTA technique showed excellent sensitivity and specificity on both a per patient and a per segment basis. • The average coronary CTA radiation dose was low at 4.2 mSv, which was lower than the average radiation dose of invasive angiography, which was 8.5mSv (p < 0.05). • Coronary CTA also required less contrast than CA (80 ml vs. 111 ml, p < 0.001).

  25. What are the the limitations of CCTA? • Heart rate greater than 60 or 70 beats/min • Irregular heart rhythm (atrial fibrillation or frequent atrial or ventricular extrasystoles) • Inability to sustain a breath hold for at least 5 to 10 seconds • Severe coronary calcification ( >400) or the presence of coronary artery stents, CAN obscure th elumen ( possible to image some stents > 2.5mm) • Segments with a diameter <1.5 mm can usually not be assessed for stenosis.

  26. CCTA: Dose Reduction Techniques • ECG-controlled tube current modulation (ECTCM) reduces the output of the x-ray tube during certain portions of the cardiac cycle when so-called retrospective gating is used. • Prospectively triggered sequential scanning is a newer scan mode on multidetector scanners that produces radiation only during predetermined portions of the cardiac cycle, getting a single, non helical dataset of the heart • High-pitch helical scanning: The main difference between this technique and other prospectively triggered techniques is that a helical, rather than sequential, CT acquisition is performed during a single R-R interval, rather than across multiple heart beats. • Tube Voltage Reduction: By reducing tube voltage from 120 kV to 100 kV decrease amount of radiation while also increasing the visualization of iodinated contrast

  27. CCTA: Dose Reduction Prospective Scanning • Not all patients encountered in clinical practice have stable, low heart rates, and not all patients with elevated heart rates will tolerate or respond to pharmacologic rate control. • 56 patients whose prospectively triggered coronary CT angiograms were not of diagnostic quality received additional conventional spiral CT scans. • 11/56 required repeat scanning , BUT overall radiation dose significantly lower than that of the control group, which underwent single retrospectively gated CT scans. • Pt’s did receive an extra 75ml of contrast. Eur Radiol 2010;20: 1197–206.

  28. CCTA: Indications • Left Bundle Branch Block • 64 slice MDCT in 66 patients without a history of CAD with new LBBB (non urgent) • The sensitivity and specificity on a per patient basis was 97 and 95 percent respectively Iskandrain JACC 2006 • Cardiac valve surgery • High sensitivity and specificity in low risk population

  29. CCTA: Diagnosis

  30. CCTA: Diagnosis

  31. CCTA: Prognosis Min et.al.Eur.Heart Jn 2010

  32. CCTA: Prognosis • 517/541 pts with an interpretable MSCT, 158 (31%) CAD (≥50% stenosis), • 168 (33%) abnl MPI (SSS ≥4), • 439 FU mean 672 days: 2 cardiac death, 8 MI, 6 noncardiac deaths, 7 hospitalizations van Werkhoven et al. JACC 2009; 53:623-32.

  33. Prognostic value of CCTA extends the ‘at-risk’ paradigm beyond obstructive coronary stenosis Min, JACC 2011

  34. Prognostic value of CCTA extends the ‘at-risk’ paradigm beyond obstructive coronary stenosis • >6-fold higher mortality for patients with 3-vessel mild CAD Increased risk of death for non-obstructive CAD even in pts with lowFRS or no medically modifiable CAD RF Min, JACC 2011

  35. CCTA: Conclusions • In the past 5 years, an abundance of scientific evidence has been developed to support the prognostic value of anatomic identification of CAD by CCTA • Large, prospective, international multicenter registries are beginning to validate prior single center study findings • Prognostic value of CCTA findings include measures of stenosis severity, plaque location, plaque composition and plaque remodeling • In the near future, additional measures of the effects of CAD, including CT-derived measures of myocardial perfusion and fractional flow reserve, may enhance risk prediction in patients undergoing CCTA

  36. Cardiac MRI: Uses Kwang ACC 2011

  37. CARDIAC MRI: Appropriateness Criteria • Ventricular and Valvular Function (7) • Intra or Extra Cardiac Structures (4) • Evaluation of Myocardial Scar (3) • Stress CMR (3)

  38. What about the limitations of Cardiac MRI? • The procedure requires considerable skill on the part of the operator, the approaches are currently vendor specific, and the entire acquisition can be time-consuming (30 minutes or more). • CMRI is relatively contraindicated in the presence of certain implanted foreign bodies or medical devices that consist mostly or entirely of metal or contain electrical circuitry (eg, pacemakers, implantable cardioverter-defibrillators). • An important exception is the presence of a coronary artery stent. Irrespective of stent type and the time since implantation, stents are not a contraindication to MRI. • Irregular heart rhythms, poor breath holding (for breath holding approaches), and an irregular breathing pattern (free breathing approaches) will result in poor image quality. • Compared to CCTA, the spatial resolution of CMRI is lower, but the temporal resolution is more flexible: the length of the data acquisition window is based upon the patient's heart rate, rather than being fixed and determined by gantry rotation speed.

  39. CARDIAC MRI • Evaluation of Ventricular or Valvular Function • Cardiomyopathies: • Myocarditis/ARVC/infiltration • Complex congenital heart disease • Valvular heart disease • Currently the most common indication (40%) • LV function, only appropriate if: • Echo of bad quality and discordant from other tests

  40. Cardiac MRI • Evaluation of Intra/Extra Cardiac Structures • Cardiac Masses • Pericardial diseases • Constrictive physiology, R/O other dz • Preferred over CT • Aortic Dissection • CT preferred for acute cases, a few exceptions • Pulmonary vein anatomy • 3D mapping for RFA or PV dimensions (30% of all CMR) Serial imaging is anticipated, avoid radiation

  41. Cardiac MRI: HCM • Three separate retrospective studies examined the relationship of delayed enhancement to outcomes over a mean of about 3 years in hypertrophic cardiomyopathy • All 3 studies found a significant univariate association between delayed enhancement and outcome.

  42. Cardiac MRI: HCM

  43. Top five Things to remember about advanced Cardiac Imaging • Calcium scoring is a useful ADDITIONAL screening study for low to intermediate risk patients to determine need for more aggressive therapy or additional testing • Appropriate to use CCTA to evaluate patients who are low risk for CAD with a non-acute, new LBBB • CT and MRI are both excellent to visualize the complex relationships and anatomy seen in the growing Adult Congenital Heart Disease population • MRI can be very helpful in assisting with management of patients after an MI or who have HCM when considering scar burden and need for an ICD • Stents are safe in the MRI

  44. Superior Doctors prevent the disease • Mediocre Doctors treat the disease before evident • Inferior Doctors treat the full blown disease • Huang Di Nei Ching 2600 BC Chinese medical text Internists General Cardiologists Interventional Cardiologists

  45. Thank You Enjoy the next talk: Dr. Francisco Dr. Seidensticker Dr. Bennett

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