Integrated SPECT/CT for assessment of haemodynamically significant coronary artery lesions in patients with acute coronary syndrome

A review of adherence to the guidelines for coronary CT angiography quantitative stenosis grading thresholds in published research

BACKGROUND

The degree of coronary stenosis of potential hemodynamic significance is central to the interpretation of coronary computed tomography angiography (CCTA), but has been variably defined in the literature. Societal guidelines have attempted to address this issue via recommended thresholds.

OBJECTIVES

We surveyed the various thresholds for defining significant coronary stenosis reported in research published since the introduction of the Society for Cardiovascular Computed Tomography guidelines regarding the interpretation and reporting of CCTA.

METHODS

We systematically reviewed the results of bibliographic searches of all original research articles on CCTA, focusing on studies reporting > 25 subjects, to assess the definitions of severity of coronary lesions as found on CCTA. To enable comparisons, we stratified the methods of reporting lesion severity into ≥ 50%, 50% to 69%, and "others" (including infrequent reporting methods).

RESULTS

Fifty-nine11 published studies were identified and met inclusion criteria. Eighteen studies reported the severity of coronary stenosis using a definition of 50% to 69% as moderate stenosis; 35 studies defined ≥ 50% coronary stenosis as "stenosis," "significant stenosis," or "obstructive lesion" without distinguishing a threshold for moderate versus severe stenosis. Six studies utilized other thresholds, such as 20% to 75%, 40% to 69%, 40% to 70%, 40% to 79%, and 50% to 75% to define moderate coronary stenosis.

CONCLUSIONS

Fifty-three of 59 studies were graded in accordance with the recommended threshold of ≥ 50% defining potentially significant stenosis, with 18 studies reporting precisely in accordance with the guidelines-recommended thresholds of ≥ 50% narrowing as defining moderate stenosis and ≥ 70% narrowing as defining severe stenosis. Six studies were reported using alternative thresholds for significant stenosis. However, a majority of research studies published since 2009 do not follow the societal guidelines for stenosis grading, since these studies do not clearly describe the degree of coronary stenosis.

Cardiac hybrid SPECT/CTA imaging to detect "functionally relevant coronary artery lesion": a potential gatekeeper for coronary revascularization?

OBJECTIVE

Combination of both morphological and functional information has gained more and more appreciation with the concept of "functionally relevant coronary artery lesion (FRCAL)" and "functional revascularization". This has paved the way for non-invasive single-photon emission computed tomography (SPECT)/computed tomography angiography (CTA) hybrid imaging. We aimed at assessing the value of cardiac hybrid imaging on the detection of FRCAL and its potential as a gatekeeper for invasive examination and treatment.

METHODS

In Two hundred and thirty-eight patients with known or suspected coronary artery disease (CAD) underwent CTA and myocardial perfusion imaging (MPI) using SPECT on a dual system scanner in one session before treatment. 78 patients underwent invasive coronary angiography (CAG) within 1 month. Detection of FRCAL by the combination of SPECT/CTA was compared with SPECT/CAG, which served as a standard of reference. According to the both combination results, treatment decision (revascularization or medical treatment) was chosen in the catheterization laboratory.

RESULTS

Sensitivity, specificity, accuracy, positive and negative prediction rate by SPECT/CTA vs. SPECT/CAG for the detection of flow-limiting coronary stenosis on patient- and vessel-based analysis were 94.33, 72.00, 87.18, 87.71, 85.71 % and 88.71, 92.44, 91.45, 80.89, 95.78 %, respectively. No revascularization procedures were performed in patients without flow-limiting stenosis. However, more than one-third (25/67, 37 %) of revascularized vessels were not associated with ischemia on MPI.

CONCLUSIONS

The cardiac SPECT/CTA hybrid imaging can accurately detect FRCAL and thereby it may be used as a gatekeeper for CAG and revascularization procedures.

Prometheus's heart: what lies beneath

A heart attack kills off many cells in the heart. Parts of the heart become thin and fail to contract properly following the replacement of lost cells by scar tissue. However, the notion that the same adult cardiomyocytes beat throughout the lifespan of the organ and organism, without the need for a minimum turnover, gives way to a fascinating investigations. Since the late 1800s, scientists and cardiologists wanted to demonstrate that the cardiomyocytes cannot be generated after the perinatal period in human beings. This curiosity has been passed down in subsequent years and has motivated more and more accurate studies in an attempt to exclude the presence of renewed cardiomyocytes in the tissue bordering the ischaemic area, and then to confirm the dogma of the heart as terminally differentiated organ. Conversely, peri-lesional mitosis of cardiomyocytes were discovered initially by light microscopy and subsequently confirmed by more sophisticated technologies. Controversial evidence of mechanisms underlying myocardial regeneration has shown that adult cardiomyocytes are renewed through a slow turnover, even in the absence of damage. This turnover is ensured by the activation of rare clusters of progenitor cells interspersed among the cardiac cells functionally mature. Cardiac progenitor cells continuously interact with each other, with the cells circulating in the vessels of the coronary microcirculation and myocardial cells in auto-/paracrine manner. Much remains to be understood; however, the limited functional recovery in human beings after myocardial injury clearly demonstrates weak regenerative potential of cardiomyocytes and encourages the development of new approaches to stimulate this process.