Evolving Developments in Cardiac CT.

In this review, the authors describe some of the latest cardiac CT advances in the evaluation of cardiovascular disease. This includes automated coronary plaque quantification and subtyping, and cardiac CT fractional flow reserve and CT perfusion as techniques to noninvasively assess the physiologic significance of coronary stenosis. The authors also focus on noncoronary applications involving the expanding role of cardiac CT in structural heart disease interventions. Developments in cardiac CT for the evaluation of diffuse myocardial fibrosis and infiltrative cardiomyopathy and for functional analysis of myocardial contractile dysfunction are discussed. Finally, the authors review studies evaluating photon-counting CT in cardiac disease.

Conventional versus modified delivery system technique in commissural alignment from the Evolut low-risk CT substudy.

OBJECTIVES: We assessed the impact of conventional delivery system (DS) insertion technique on "Hat-marker" orientation/commissural alignment in patients who underwent transcatheter aortic valve replacement (TAVR) in the Evolut Low Risk Trial CT substudy versus a modified technique. BACKGROUND: Unlike surgical aortic valve replacement, where alignment of the surgical valve commissures with native commissures can be achieved virtually 100% of the time, commissural alignment during TAVR is not achieved consistently. This may subsequently impact the feasibility of both coronary access and reintervention after TAVR. METHODS: "Hat-marker" orientations during deployment were characterized as outer curve (OC), center front (CF), inner curve, and center back. Severe commissure-to-CA overlap was 0-20°. "Hat-marker" orientations and CA overlap were compared to 240 patients from a single center using the modified 3-o'clock flush port DS technique. RESULTS: In the CT substudy in which conventional DS insertion was performed (flush port at 12 o'clock); 154/249 had both analyzable CT and procedural fluoroscopy to validate "Hat-marker" to C-tab/commissural orientation. On post-TAVR CT, Evolut valve commissural orientation and coronary artery (CA) ostia were identified. Compared to conventional DS technique in the CT substudy, the modified technique had higher rates of "Hat-marker" at OC/CF orientation, improved commissural alignment and reduced severe CA overlap; (left main, 14.2 vs. 27.9%; right coronary artery, 11.7 vs. 27.3% both, 5.0 vs. 13.6%; 1 or both CA, 20.8 vs. 41.6%, all p < 0.01). CONCLUSIONS: The modified technique improved initial "Hat-marker" orientation during Evolut deployment and resulted in better commissural alignment and reduced CA overlap.

Comparison Between the Performance of Quantitative Flow Ratio and Perfusion Imaging for Diagnosing Myocardial Ischemia.

OBJECTIVES: This study compared the performance of the quantitative flow ratio (QFR) with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) myocardial perfusion imaging (MPI) for the diagnosis of fractional flow reserve (FFR)-defined coronary artery disease (CAD). BACKGROUND: QFR estimates FFR solely based on cine contrast images acquired during invasive coronary angiography (ICA). Head-to-head studies comparing QFR with noninvasive MPI are lacking. METHODS: A total of 208 (624 vessels) patients underwent technetium-99m tetrofosmin SPECT and [15O]H2O PET imaging before ICA in conjunction with FFR measurements. ICA was obtained without using a dedicated QFR acquisition protocol, and QFR computation was attempted in all vessels interrogated by FFR (552 vessels). RESULTS: QFR computation succeeded in 286 (52%) vessels. QFR correlated well with invasive FFR overall (R = 0.79; p < 0.001) and in the subset of vessels with an intermediate (30% to 90%) diameter stenosis (R = 0.76; p < 0.001). Overall, per-vessel analysis demonstrated QFR to exhibit a superior sensitivity (70%) in comparison with SPECT (29%; p < 0.001), whereas it was similar to PET (75%; p = 1.000). Specificity of QFR (93%) was higher than PET (79%; p < 0.001) and not different from SPECT (96%; p = 1.000). As such, the accuracy of QFR (88%) was superior to both SPECT (82%; p = 0.010) and PET (78%; p = 0.004). Lastly, the area under the receiver operating characteristics curve of QFR, in the overall sample (0.94) and among vessels with an intermediate lesion (0.90) was higher than SPECT (0.63 and 0.61; p < 0.001 for both) and PET (0.82; p < 0.001 and 0.77; p = 0.002), respectively. CONCLUSIONS: In this head-to-head comparative study, QFR exhibited a higher diagnostic value for detecting FFR-defined significant CAD compared with perfusion imaging by SPECT or PET.

Canadian Cardiovascular Society/Canadian Association of Radiologists consensus training standards for cardiac computed tomography.

With the goal of optimizing patient care, standards for training in cardiac computed tomography have been developed collaboratively by the Canadian Association of Radiologists and the Canadian Cardiovascular Society. These standards apply to both radiologists and cardiologists.