This article is more than 5 years old. Information may no longer be current.

Recent advances in cardiovascular imaging

Issue: September 2015

ByChristopher Kramer, MD

ByDavid DeMaria, MD

Add topic to email alerts

Receive an email when new articles are posted on

Please provide your email address to receive an email when new articles are posted on .

Subscribe

Added to email alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

Back to Healio

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

Back to Healio

In the past year, there have been significant advances in each of the major CV imaging modalities. Many key developments were highlighted at the 2015 American College of Cardiology Scientific Sessions in March and are reviewed in this commentary.

Echocardiography

A systematic review of studies including 1,504 patients examined the utility of strain imaging to predict chemotherapy-induced cardiotoxicity. A 10% to 15% early reduction in global longitudinal strain by speckle-tracking echocardiography was noted to be the most useful parameter for the prediction of subsequent cardiotoxicity. This study supports the value of reduced global longitudinal strain to predict subsequent development of chemotherapeutic cardiotoxicity.

Another study examined the role of exercise echocardiography in 426 asymptomatic or minimally symptomatic patients with hypertrophic cardiomyopathy (HCM) followed for 9 ± 3 years. The researchers found that reduced exercise capacity and abnormal heart rate recovery on exercise echocardiography independently predicted death, appropriate implantable cardioverter defibrillator discharge and HF exacerbations. They demonstrated that patients who achieved at least 100% of age- and sex-predicted metabolic equivalents had excellent long-term outcomes, with an event rate of 1% as compared with 12% in those achieving less than 85% of age- and sex- predicted metabolic equivalents. Consequently, in asymptomatic or minimally symptomatic patients with HCM, exercise stress echocardiography can be considered an important technique for risk stratification.

Nuclear imaging

PET was used to determine the prognostic implications of coronary microvascular dysfunction in a large cohort of patients without clinical evidence of obstructive CAD. The study group contained 405 men and 813 women, all referred for rest/stress PET myocardial perfusion imaging for evaluation of suspected CAD. Coronary flow reserve (CFR) was quantified, using a value less than 2 to define the presence of coronary microvascular dysfunction. After following patients for a median of 1.3 years, the researchers noted that CFR was a strong predictor of major adverse cardiac events in the absence of obstructive CAD, regardless of gender.

The same group assessed the association between PET-measured CFR, angiographic CAD and CV outcomes. The cohort included 329 patients who were referred for invasive coronary angiography (ICA) after stress testing with myocardial perfusion PET and followed for a median of 3.1 years for CV death and HF admissions. After adjustment, CFR and CAD prognostic index were independently associated with major cardiac events, and patients with low CFR or high CAD prognostic index showed the highest risk of events. CFR was associated with outcomes independent of angiographic CAD and modified the effect of early revascularization.

Another important study using cardiac PET and the tracers 18F-sodium fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG) aimed to identify ruptured and high-risk atherosclerotic plaques. The cohort included 40 patients with a recent MI and another 40 patients with stable angina, all of whom underwent 18F-NaF and 18F-FDG PET-CT, and ICA. The highest coronary 18F-NaF uptake was seen in culprit plaques, whereas coronary 18F-FDG uptake was generally obscured by myocardial uptake. Plaques in patients with stable angina with higher tissue-to-background ratios of 18F-NaF were associated with more high-risk features on IVUS. 18F-NaF identified using PET-CT, thus, is a promising noninvasive imaging modality to identify and localize high-risk coronary plaques.

Cardiac MRI

As HCM is the most common cause of sudden cardiac death in the young, identifying patients at risk who would benefit from an ICD is critical. The role of late gadolinium enhancement (LGE) by cardiac MRI in stratifying sudden cardiac death in patients with HCM is being defined. In a retrospective study, 1,293 patients with HCM referred for cardiac MRI with LGE were followed for a median of 3.3 years. The extent of LGE was associated with an increased risk for sudden cardiac death events with an adjusted HR of 1.46/10% increase in LGE and predicted the development of end-stage HCM (ejection fraction < 50%; HR of 1.8/10% increase in LGE). These results suggest that the extent of LGE aids in prognostication in HCM.

A greater emphasis has been placed on understanding the role of the extracellular matrix to design new therapeutic strategies for HF. Extracellular matrix expansion is known to be associated with mechanical, electrical and vasomotor dysfunction and adverse outcomes. Advances in cardiac MRI with T1 mapping now allow quantification of extracellular volume fraction (ECV) by exploiting the extracellular nature of gadolinium. Understanding the role of increased ECV in various disease states may provide a new method to assess prognosis and aid in the development of novel therapeutics.

The association between diffuse myocardial fibrosis and impaired diastolic function in systolic HF and HF with preserved ejection fraction (HFpEF) could not be previously examined without a myocardial biopsy. Noninvasive assessment of interstitial fibrosis is now possible with T1 mapping and ECV measurement. Using ECV as a surrogate for diffuse myocardial fibrosis, a recent study found higher ECV in patients with systolic HF (31.2%) and HFpEF (28.9%) compared with controls (27.9%). Myocardial ECV was significantly correlated with peak filling rate only in the HFpEF group, thus demonstrating a link between diffuse myocardial fibrosis and impaired diastolic function in this important group of patients.

Coronary CTA

The FACTOR-64 randomized clinical trial examined whether routine screening for CAD by CTA in patients with diabetes followed by CTA-directed therapy would reduce the risk for death and nonfatal coronary outcomes. The study included 900 patients with type 1 or 2 diabetes without symptoms of CAD. Patients were randomly assigned to CTA or to standard guidelines-based optimal diabetes care. Based on CTA findings, patients were assigned to either standard therapy, aggressive therapy or aggressive therapy with ICA and then followed for composite outcomes including all-cause mortality, nonfatal MI or unstable angina. After 4 years, the primary outcome event rates were not different between the CTA and control groups (6.2% vs. 7.6%). Therefore, the use of CTA to screen for CAD among asymptomatic patients with diabetes is not supported.

The CORE320 study sought to examine the diagnostic power of integrating CTA and CT myocardial perfusion (CTP) in the identification of flow-limiting CAD. The latter was defined as a flow-limiting coronary artery stenosis by ICA causing a perfusion defect by single-photon emission CT. Sixteen centers enrolled 381 patients. For the combination of a CTA stenosis of at least 50% and a CTP deficit, the sensitivity, specificity, positive predictive and negative predicative values were 80%, 74%, 65% and 86%, respectively. For flow-limiting disease defined by ICA-SPECT, the accuracy of CTA was significantly increased by the addition of CTP at both the per-patient and per-vessel levels.

The NXT trial enrolled 254 patients to determine the diagnostic performance of noninvasive fractional flow reserve derived from coronary CTA (FFRCT). The trial aimed to use FFRCT to diagnose myocardial ischemia with suspected stable CAD using FFR at the time of ICA as the gold standard. FFRCT provided high diagnostic accuracy with a sensitivity and specificity of 86% and 79% vs. 94% and 34% for coronary CTA, and 64% and 83% for ICA, respectively.

The PROMISE trial examined outcomes of patients presenting with new symptoms suggestive of CAD that required further evaluation, specifically with either anatomical testing by CTA or by functional testing with exercise ECG, nuclear stress testing or stress echocardiography. The study included 10,003 patients who were followed for a median of 2 years. The results indicated that rates of death, MI, hospitalization for unstable angina or major procedural complication (which were lower than expected in both groups) were similar between the CTA group and functional-testing group. Thus, an initial strategy of CTA is a reasonable approach in such patients with low-intermediate risk for CAD.

Multimodality imaging and appropriate use

The American College of Cardiology Foundation Appropriate Use Criteria Task Force reviewed common clinical presentations for stable ischemic heart disease, concentrating on the appropriate use of different stress and anatomic diagnostic procedures. The use of these procedures in 80 clinical scenarios were scored by a rating panel as “appropriate,” “may be appropriate” or “rarely appropriate.” This is the first multimodality appropriate use criteria document and supersedes many of the older single modality documents for these scenarios. Multimodality documents on left ventricular structure, function and valvular heart disease are presently under development.

• References:
• Chan RH, et al. Circulation. 2014;doi:10.1161/CIRCULATIONAHA.113.007094.
• Desai MY, et al. JACC Cardiovasc Imaging. 2014;doi:10.1016/j.jcmg.2013.08.010.
• Douglas PS, et al. N Engl J Med. 2015;doi:10.1056/NEJMoa1415516.
• Joshi NV, et al. Lancet. 2014;doi:10.1016/S0140-6736(13)61754-7.
• Muhlestein JB, et al. JAMA. 2014;doi:10.1001/jama.2014.15825.
• Murthy VL, et al. Circulation. 2014;doi:10.1161/CIRCULATIONAHA.113.008507.
• Nørgaard BL, et al. J Am Coll Cardiol. 2014;doi:10.1016/j.jacc.2013.11.043.
• Rochitte CE, et al. Eur Heart J. 2014;doi:10.1093/eurheartj/eht488.
• Schelbert EB, et al. J Am Coll Cardiol. 2014;doi:10.1016/j.jacc.2014.01.068.
• Su MY, et al. JACC Cardiovasc Imaging. 2014;doi:10.1016/j.jcmg.2014.04.022.
• Taqueti VR, et al. Circulation. 2015;doi:10.1161/CIRCULATIONAHA.114.011939.
• Thavendiranathan P, et al. J Am Coll Cardiol. 2014;doi:10.1016/j.jacc.2014.01.073.
• Wolk MJ, et al. J Am Coll Cardiol. 2014;doi:10.1016/j.jacc.2013.11.009.

• For more information:
• David DeMaria, MD, is from the department of medicine at University of Virginia Health System, Charlottesville, Virginia. Christopher Kramer, MD, is from the department of medicine and the department of radiology and medical imaging at University of Virginia Health System. Kramer can be reached at University of Virginia Health System, Departments of Medicine and Radiology, Lee Street, Box 800170, Charlottesville, VA 22908; email: ckramer@virginia.edu.

Disclosures: DeMaria reports no relevant financial disclosures. Kramer reports receiving research equipment support from Siemens Healthcare; consulting for Merck, Myokardia and St. Jude Medical; and receiving research grants from the NHLBI and Novartis.