Special Issue of JACC: Cardiovascular Imaging Focuses on Advances A recent special issue of JACC: Cardiovascular Imaging reviews advances in the field through state-of-the art papers and imaging outcomes research. Here are some highlights from this issue. CAC Screening Coronary artery calcium (CAC) scans may be useful for screening for coronary artery disease. Risk scores have been somewhat useful, yet increasingly data indicate that a CAC scan is far more accurate for predicting risk. Currently there is no consensus among physician groups when to use cardiac imaging to screen for heart disease. It is first discovered at the time of a myocardial infarction or death in some 40-60 percent of cases. Alan Rozanski, MD, FACC, and colleagues evaluated five clinical trials with 4,615 participants without heart disease: one trial involved cardiac stress imaging, three involved CAC scanning and one involved non-invasive coronary CT angiography.The trials showed that because modern therapies have markedly reduced the frequency for developing the most serious consequences of heart disease, such as myocardial infarctions and sudden death, it may be difficult to prove that the use of imaging techniques reduce cardiac death in clinical trials. Instead, the focus is turning to determining if CAC scanning and other screening techniques can improve the overall cardiac risk profile of patients without increasing medical costs; this was shown in the EISNER trial, but more studies are needed. “There is now sufficient evidence to support the routine use of CAC scanning for screening in clinical practice,” Rozanski said. “Importantly, the CAC score has become one of our most robust predictors of patient risk. Patients are at very low risk when the CAC score is zero and at high risk when the CAC score is highly elevated. Any degree of CAC abnormality, however, even a CAC score of one or above, is sufficient reason for patients to adopt more heart-healthy behaviors.” “We believe this will not only help improve and save lives but that it can ultimately contribute to lower health costs since the earlier adoption of positive health habits can reduce patients clinical risk and potentially eliminate the need for more costly interventions later on,” he said. Carotid Plaque Lipid Content, Fibrous Cap Status To Predict Cardiovascular Outcomes In patients with atherosclerotic disease, carotid plaque lipid content and fibrous cap status were strongly associated with systemic cardiovascular outcomes. In the AIM-HIGH trial, Jie Sun, MD, et. Al., examined 214 patients with acceptable diagnostic image quality. The primary endpoint was fatal and nonfatal myocardial infarction, ischemic stroke, hospitalization for acute coronary syndrome and symptomdriven revascularization. During the median follow-up of 35. 1 months, 18 patients reached the primary endpoint; no significant association was seen between the traditional risk factors or the randomized treatment assignment. Even though there was a high rate of statin use, calcification, lipidrich necrotic core (LRNC), intraplaque hemorrhage (IPH) and thin/ruptured fibrous cap were detected by carotid MRI in 48 percent, 52 percent, 8 percent and 14 percent of the patients, respectively. Patients with thin/ ruptured fibrous cap had a 4.31-fold increased risk for the primary endpoint. Plaque lipid content also was significantly associated with the primary endpoint, while the association of plaque calcification content was not statistically significant. The association of IPH with the primary endpoint was positive, but did not reach statistical significance. “By leveraging the rigorously adjudicated outcome data of a contemporary clinical trial, we evaluated MRI measurements of carotid plaque characteristics as surrogate markers for systemic cardiovascular outcomes,” the authors write. “The observed associations between carotid plaque characteristics and systemic cardiovascular outcomes were not driven by traditional risk factors, plaque burden or AIM-HIGH treatment assignment, which did not significantly predict the primary endpoint by themselves and had little influence on the associations of plaque characteristics with outcomes in multivariate analyses.” Noninvasive Imaging Safe and Effective for Most Patients with Chest Pain In low- to intermediate-risk patients with acute chest pain, noninvasive imaging is safe and effective in expediting care and reducing hospital admissions. Every year, over eight million patients in the U.S. come to the emergency department for acute chest pain. Nearly 75 percent are diagnosed with non-cardiac or non-ischemic cardiac problems and less than 20 percent of the rest meet criteria for acute coronary syndrome (ACS). Patients at either end of the coronary risk spectrum are easily triaged, but those with low-to-intermediate cardiac risk and no clear evidence of diagnosis present a challenge. Over the last 20 years, cardiac imaging has played an increasing role in helping to diagnose these patients. In this review, Gilbert I. Raff, MD, FACC, and colleagues examined trials that evaluated different diagnostic strategies including radionuclide myocardial perfusion imaging (MPI), stress echocardiography, cardiac magnetic resonance (CMR) imaging, coronary computed tomographic angiography (CTA), and high-sensitivity troponin and imaging. Findings from the radionuclide MPI trials included the observation that MPI was safe and unnecessary admissions were lower compared with patients treated with standard-of-care diagnostic strategy, including electrocardiography (ECG). Stress echocardiography was found to have significant clinical and cost benefits compared with a stress ECG. CMR was also found to be cost-effective and a majority of cases were managed without hospitalization. The CMR studies also revealed the potential for this imaging technique to be incorporated into an evaluation strategy pathway for higher-risk emergency department patients. Coronary CTA shortened time to diagnosis, lowered cost and reduced length of stay; however some trials found that a greater number of patients had to undergo additional testing. While one study found increased radiation dose with CTA, another study found significantly lower doses. Finally, high-sensitivity troponin testing, which has become widely available in Europe and incorporated into the standard of care for patients with acute chest pain, was associated with lower costs and less outpatient testing. However, it does not shorten length of stay or allow more immediate discharge. The authors state that because anatomic stenosis cannot predict flow, invasive fractional flow reserve is required for optimal decision making regarding revascularization. “It is evident that combining functional and anatomic imaging in a single noninvasive imaging modality or session would be advantageous, particularly in higher-risk patients with acute chest pain who are more likely to have multiple plaques,” they write. “Three such tests are currently available: positron emission tomography or MPI combined with computed tomography angiography in a single scanner, computed tomography perfusion, and fractional flow reserve by computed tomography.” Greater Radiation Exposure With Radial Versus Femoral PCI Operators and patients are exposed to more radiation with the radial approach compared with the femoral approach to PCI for acute coronary syndrome, according to the results of a study presented at ACC.17 and simultaneously published in JACC: Interventions. The study – the largest so far on this topic – was conducted in Italy, the Netherlands, Spain and Sweden between October 2011 and November 2014. In RAD-MATRIX, a sub-study of the MATRIX study, 18 operators wore dosimeters and data were collected on fluoroscopy time and dose area product (DAP) from a total of 777 procedures performed in 767 patients. Dosimeters were worn on the left wrist, at mid-thorax, and at the head level to measure eye exposure. Patient exposure was measured indirectly using a conversion factor of 0. 20 mSv per Gy cm2. The primary endpoint of the radiation dose at the thorax of the operator was significantly higher with radial access (77 ìSv vs. 41 ìSv with femoral access; p = 0.02) – and did not differ by right or left radial access. The study did not achieve non-inferiority for the primary hypothesis of the radial access not being associated with a higher operator dose than the femoral access (p value for non-inferiority 0. 843). The difference in the primary endpoint remained significant after normalization of the operator dose by fluoroscopy time or DAP. There was no difference in the radiation dose at the wrist or head of the operator between the two strategies. For patients, the median fluoroscopy time was longer with radial than with femoral access (10. 2 min vs. 9.1 min; p < 0.0001). Likewise, the median DAP was higher with the radial access (64.7 Gy cm2 vs. 59.1 Gy cm2; p = 0.0001). Alessandro Sciahbasi, MD, PhD, et al., write that the average increase in radiation exposure was relatively small, at about 10 percent, for patients undergoing radial rather than femoral access PCI. However, for operators, there was a two-fold increase in radiation exposure at the thorax with the radial approach. Further, they state their results confirm DAP is a weak predictor of radiation exposure for operators. Of note, the incremental increase in the operator’s radiation exposure for a single procedure by radial access versus femoral access is in the range of 1.1 ìSv, corresponding to an additive 300 ìSv for every 300 procedures – similar to the additive radiation exposure of 17 chest X-rays. Schiahbasi A, Frigoli E, Sarandrea A, et al. JACC Cardiovasc Interv 2017;March 18:[Epub head of print]. Ambulatory Hemodynamic Monitoring Shows Reduction in HF Hospitalizations Use of ambulatory hemodynamic monitoring in clinical practice reduces heart failure (HF) hospitalizations and comprehensive HF costs, according to an oral abstract presented at ACC.17 and simultaneously published in the Journal of the American College of Cardiology. The study, led by Akshay S. Desai, MD, MPH, FACC, et. Al., retrospectively examined publicly available administrative claims data from the U.S. Centers for Medicare and Medicaid Services (CMS) to compare the rates of HF hospitalizations and the costs associated with HF care in the periods before and after pulmonary artery pressure (PAP) sensor implantation. According to the authors, the analysis of the CMS data suggests that reductions in HF hospitalizations and cost savings seen in trial populations may also be achievable in clinical practice. The 45 percent lower rate of cumulative HF hospitalizations observed at six months after PAP sensor implant versus the six months prior to implantation compares favorably with the 28 percent reduction seen with PAP-guided therapy over the same time period in the randomized CHAMPION study that supported initial U.S. Food and Drug Administration approval for the device. As such, the authors argue for clinical effectiveness of ambulatory hemodynamic monitoring as a strategy for HF management. In an accompanying editorial, Harlan M. Krumholz, MD, SM, FACC, and Sanket S. Dhruva, MD, FACC, commented that the paper “responds to the great need for evidence about CardioMEMS, but unfortunately does not have the evidentiary strength to inform clinical decisions.” They add that “the causal language in the authors’ conclusion is not commensurate with the data available and the methods employed.” Further, Krumholz and Dhruva suggest additional independent trials and more detailed observational studies. Desai AS, Bhimaraj A, Bharmi R, et al. JACC 2017;March19:[Epub ahead of print]. Shifts in Eligibility for CRT In Heart Failure Patients Characterized in Analysis of Guideline Criteria A smaller proportion of patients with heart failure and a left ventricular ejection fraction (LVEF) .35 percent were eligible for cardiac resynchronization therapy (CRT) using criteria from the current 2013 ACCF/American Heart Association (AHA) heart failure guidelines compared with those from the 2009 guidelines. The first analysis of the influence of the new CRT criteria on eligibility was presented by Kristin J. Lyons, MDCM, as an oral abstract at ACC.17 and simultaneously published in JACC: Heart Failure. In a population of 25,102 patients from 238 hospitals, identified in the Get With the Guidelines-HF database, eligibility for CRT was 33.1 percent and 49.1 percent, respectively, based on the 2013 and 2009 criteria (p < 0.0001). Of note, the 2013 guidelines expanded the criteria for CRT to include NYHA Class II patients, but limited the criteria to patients with LVEF .35 percent, sinus rhythm, and a left bundle branch block (LBBB) or a non-LBBB and a QRS .150 msec. QRS duration and morphology were the only significant differences in the baseline characteristics of the patients classified as eligible for CRT based on the 2013 and 2009 criteria. In both groups, patients were 73 years old and most were men and white (70 percent each). Their LVEF was 23 percent and 43 percent had atrial fibrillation/flutter; the etiology of heart failure was hypertension for 78 percent and ischemic for 70 percent. Among the 5,303 patients with a QRS duration of 120-149 msec, only 21.3 percent were eligible with the new criteria versus 78.7 percent with the old criteria. For a QRS .150 msec, nearly all patients were eligible for CRT using both criteria. Likewise, nearly all patients with a LBBB were eligible using both criteria. However, using the new criteria, non-LBBB limited eligibility to 56.8 percent versus nearly all patients using the old criteria. Low adherence to guideline recommendations for CRT was found using both criteria: only 57.8 percent and 54.9 percent of those eligible based on the 2013 and 2009 criteria respectively had a CRT prescribed or placed at the time of hospital discharge. The investigators stated that although there is the potential for health care costs to be reduced because fewer patients are eligible for CRT, improvement is needed in adherence to device therapy for eligible patients with heart failure. Lyons KJ, Ezekowitz JA, Liang L, et al. JACC: Heart Fail 2017;March 17:[Epub ahead of print]. Stress echocardiography was found to have significant clinical and cost benefits compared with a stress ECG. The incremental increase in the operator’s radiation exposure for a single procedure by radial access… similar to the additive radiation exposure of 17 chest X-rays.a Improvement is needed in adherence to device therapy for eligible patients with heart failure.
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