“Currently the hottest area in nuclear cardiology is the integration of multi-slice computed tomography and myocardial perfusion imaging, allowing combination of anatomy and function” says Jeroen Bax, pictured right.
In this interview for the ESC e-News, Jeroen Bax provides a preview on the content of ICNC-8 here, unravels the latest innovations in Nuclear Cardiology and anticipates the future in Nuclear Cardiology (NC). Read on:
ESC: What area of imaging in Nuclear Cardiology today is emerging rapidly?
JJB: Over the past years, positron emission tomography (PET) has attracted a lot of attention; with this technique absolute quantification of cardiac perfusion and metabolism is possible.
At present, absolute quantification of these processes is only feasible with positron emission tomography. In addition, this technique has become more widely available in the recent years. Assessment of cardiac metabolism has been used with PET more than 2 decades; assessment of metabolism is important in the detection of viable myocardium in patients with left ventricular dysfunction and chronic coronary artery disease.
Interest in perfusion imaging with PET is attracting attention
More recently, interest in perfusion imaging with PET has attracted attention, because, for the detection of coronary disease, this technique most likely will have the highest accuracy. In addition, data on the prognostic value are emerging with excellent initial results reported.
ESC: What area of equipment in Nuclear Cardiology is the newest today?
JJB: Undoubtedly, the integration between multi-slice CT and positron emission tomography is the area of most technical development. Multi-slice CT has gained enormous attention over the last years. This technique allows non-invasive imaging of the coronary arteries.
The strength of multi-slice CT
Initially, 4-slice CT systems were used, and recently 64-slice CT systems have been introduced. With high accuracy it is possible to assess non-invasively coronary artery calcium and coronary artery stenoses.
The strength of multi-slice CT is currently related to the high negative predictive value, indicating that a normal CT study virtually excludes coronary artery disease.
On the other hand, the presence of coronary artery calcium indicates coronary artery disease or rather, atherosclerosis.
However, the presence of atherosclerosis does not necessarily indicate obstructive coronary artery disease causing ischemia. Accordingly, the main problem is currently related to the precise place of multi-slice CT in clinical cardiology.
Initially, 4-slice CT systems were used, and recently 64-slice CT systems have been introduced. With high accuracy it is possible to assess non-invasively coronary artery calcium and coronary artery stenoses. The strength of multi-slice CT is currently related to the high negative predictive value, indicating that a normal CT study virtually excludes coronary artery disease. On the other hand, the presence of coronary artery calcium indicates coronary artery disease or rather, atherosclerosis. However, the presence of atherosclerosis does not necessarily indicate obstructive coronary artery disease causing ischemia. Accordingly, the main problem is currently related to the precise place of multi-slice CT in clinical cardiology.
MSCT and PET complement each other
In contrast to the anatomic evaluation of MSCT, nuclear myocardial perfusion imaging allows assessment of ischemia. With the introduction of PET-CT systems, it is now possible to integrate the anatomic information from MSCT with the hemodynamic information from PET. Fusion of the 2 image sets allows integrated evaluation of coronary artery stenoses.
Indeed, MSCT and PET provide complementary information; the techniques should be considered as complementary, rather than competing.
In addition, fusion between MSCT and SPECT is also possible. Sequential imaging of MSCT, followed by SPECT can also be envisioned. Patients will first undergo MSCT; if the MSCT is normal, coronary artery disease can be excluded. If the MSCT is abnormal however, then atherosclerosis is present. Perfusion imaging can then be performed and provide to information on whether the stenoses are hemodynamically important, i.e. whether they cause ischemia or not.
ESC: Is NC implemented in the daily management of patients with known or suspected coronary artery disease?
In contrast to the anatomic evaluation of MSCT, nuclear myocardial perfusion imaging allows assessment of ischemia. With the introduction of PET-CT systems, it is now possible to integrate the anatomic information from MSCT with the hemodynamic information from PET. Fusion of the 2 image sets allows integrated evaluation of coronary artery stenoses. Indeed, MSCT and PET provide complementary information; the techniques should be considered as complementary, rather than competing.In addition, fusion between MSCT and SPECT is also possible. Sequential imaging of MSCT, followed by SPECT can also be envisioned. Patients will first undergo MSCT; if the MSCT is normal, coronary artery disease can be excluded. If the MSCT is abnormal however, then atherosclerosis is present. Perfusion imaging can then be performed and provide to information on whether the stenoses are hemodynamically important, i.e. whether they cause ischemia or not.
JJB: NC has become completely integrated in the daily management of patients with known or suspected coronary artery disease. In the diagnostic and prognostic work-up of these patients NC has been established as a highly accurate technique for diagnosis of coronary artery disease, with sensitivity of 80-90% and specificity (or normalcy rate) of 80-90%.
In addition, the prognostic value has been validated in 70.000 patients; the event-rate of a normal NC study was less than 1%.
NC is now extensively used in the evaluation of high-risk groups
Moreover, NC is extensively used in the evaluation of high-risk groups, such as patients with diabetes. An increasing prevalence of obesity is expected to drive the number of individuals with diabetes worldwide to more than 330 million by the year 2025. Patients with type 2 diabetes have a 2–4-fold higher risk of a cardiovascular event than non-diabetic patients, and cardiovascular disease is the principal cause of death in patients with type 2 diabetes. There is thus a clear need to identify patients with type 2 diabetes who are at risk of cardiovascular events before the onset of symptoms. Accordingly, early identification of atherosclerosis and ischemia is needed; the recently reported DIAD trial by Professor Frans Wackers (chair ICNC-6 and ICNC-7) has highlighted the central role of NC in the detection of silent ischemia in patients with diabetes 2.
The results revealed that the prevalence of silent ischemia was 22% (one in 5) in asymptomatic patients with diabetes.
ERASE trial in the emergency room
Similarly, the ERASE trial has demonstrated the role of NC for evaluation and risk stratification of patients presenting with chest pain to the emergency room. NC imaging improved emergency room triage decision making for patients with symptoms suggestive of acute cardiac ischemia without obvious abnormalities on initial ECG. With the use of NC, unnecessary hospitalizations were reduced among patients without acute ischemia, without reducing appropriate admission for patients with acute ischemia.
ESC: What technical innovations are important in NC?
JJB: The integration of function and perfusion with NC imaging, using gated SPECT has matured. The majority of centers do now routinely perform gated SPECT and information on ischemia, scar tissue on the one hand and left ventricular ejection fraction and volumes on the other hand is derived.
Also, attenuation correction has matured and can be applied in the clinical setting.
ESC: Which direction in research is important?
JJB: There is strong interest to evaluate different aspects of coronary artery disease (from atherosclerosis to heart failure) on the molecular level. Many nuclear cardiology centres are presently investigating novel ways to image cardiac disease by applying a radiolabeled tracers to visualize pathophysiological processes on the molecular level.
Imaging and detection of the vulnerable plaque
One area of particular interest is imaging of the vulnerable plaque, that is detection of coronary artery plaques that are likely to rupture and result in an acute coronary syndrome. In this field in particular, NC and molecular imaging will play a major role. Also the use of PET-CT providing the integrated information on coronary anatomy (stenoses, plaques) with MSCT in combination with functional imaging with PET will be important in the detection of the vulnerable plaque.
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Want to know more about the 8th International Conference of Nuclear Cardiology (ICNC-8)? The ICNC-8 website is under construction, however you may download a print version of the First Announcement
here (PDF 233 Kb).
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Also make sure you read
Jeroen Bax's preview of ICNC-8 here...