Coronary microvascular disease in hypertrophic and infiltrative cardiomyopathies

Pathologic hypertrophy of the cardiac muscle is a commonly encountered phenotype in clinical practice, associated with a variety of structural and non-structural diseases. Coronary microvascular disease is considered to play an important role in the natural history of this pathological phenotype. Non-invasive imaging modalities, most prominently positron emission tomography and cardiac magnetic resonance, have provided insights into the pathophysiological mechanisms of the interplay between hypertrophy and the coronary microvasculature. This article summarizes the current knowledge on coronary microvascular dysfunction in the most frequently encountered forms of pathologic hypertrophy. Keywords: CMD; CMR; Coronary microvascular disease; cardiac PET; coronary flow reserve; left ventricular hypertrophy

Non-invasive nuclear myocardial perfusion imaging improves the diagnostic yield of invasive coronary angiography

Aims Several studies reported on the moderate diagnostic yield of elective invasive coronary angiography (ICA) regarding the presence of coronary artery disease (CAD), but limited data are available on how prior testing for ischaemia may contribute to improve the diagnostic yield in an every-day clinical setting. This study aimed to assess the value and use of cardiac myocardial perfusion single photon emission computed tomography (MPS) in patient selection prior to elective ICA. Methods and results The rate of MPS within 90 days prior to elective ICA was assessed and the non-invasive test results were correlated with the presence of obstructive CAD on ICA (defined as stenosis of ≥50% of a major epicardial coronary vessel). Multivariate logistic regression analysis was performed to identify predictors of obstructive CAD. A total of 7530 consecutive patients were included. At catheterization, 3819 (50.7%) were diagnosed as having obstructive CAD. Patients with a positive result on MPS (performed in 23.5% of patients) were significantly more likely to have obstructive CAD as assessed by ICA than those who did not undergo non-invasive testing (74.4 vs. 45.6%, P < 0.001). Furthermore, a pathological MPS result was a strong, independent predictor for CAD findings among traditional risk factors and symptoms. Conclusion In an every-day clinical setting, the use of MPS substantially increases the diagnostic yield of elective ICA and provides incremental value over clinical risk factors and symptoms in predicting obstructive CAD, thus emphasizing its importance in the decision-making process leading to the use of diagnostic catheterizatio

Fully automated deep learning powered calcium scoring in patients undergoing myocardial perfusion imaging

BACKGROUND To assess the accuracy of fully automated deep learning (DL) based coronary artery calcium scoring (CACS) from non-contrast computed tomography (CT) as acquired for attenuation correction (AC) of cardiac single-photon-emission computed tomography myocardial perfusion imaging (SPECT-MPI). METHODS AND RESULTS Patients were enrolled in this study as part of a larger prospective study (NCT03637231). In this study, 56 Patients who underwent cardiac SPECT-MPI due to suspected coronary artery disease (CAD) were prospectively enrolled. All patients underwent non-contrast CT for AC of SPECT-MPI twice. CACS was manually assessed (serving as standard of reference) on both CT datasets (n = 112) and by a cloud-based DL tool. The agreement in CAC scores and CAC score risk categories was quantified. For the 112 scans included in the analysis, interscore agreement between the CAC scores of the standard of reference and the DL tool was 0.986. The agreement in risk categories was 0.977 with a reclassification rate of 3.6%. Heart rate, image noise, body mass index (BMI), and scan did not significantly impact (p=0.09 - p=0.76) absolute percentage difference in CAC scores. CONCLUSION A DL tool enables a fully automated and accurate estimation of CAC scores in patients undergoing non-contrast CT for AC of SPECT-MPI

Diagnosis and Management of Anomalous Coronary Arteries with a Malignant Course

Although the prevalence of anomalous coronary artery from the opposite sinus (ACAOS) in the general population is low, more frequent use of invasive and non-invasive imaging to rule out coronary artery disease has seen an increase in absolute numbers of ACAOS. ACAOS are traditionally classified as malignant (with an interarterial course) and benign variants. Malignant variants have been recognised in autopsy studies to be an underlying cause of sudden cardiac death in young athletes. Conversely, it seems that older people with ACAOS are less predisposed to adverse cardiac events. Non-invasive anatomic imaging is complementary to invasive imaging and helps to further identify high-risk anatomic features. Using functional non-invasive perfusion imaging can assess potential ischaemia induced by dynamic compression of malignant ACAOS. Information gained from clinical imaging guides the management of these patients

Myocardial perfusion imaging with real-time respiratory triggering: Impact of inspiration breath-hold on left ventricular functional parameters

Background: The latest gamma-camera generation with cadmium-zinc-telluride (CZT) detectors allows myocardial perfusion imaging (MPI) with respiratory triggering at breath-hold. We assessed its impact on functional left ventricular (LV) parameters. Methods: Twenty-eight consecutive patients underwent a one-day 99mTc-tetrofosmin pharmacologic stress/rest imaging protocol on a novel CZT camera. Electrocardiogram-gated high-dose (rest) MPI was performed without and with real-time respiratory triggering by intermittent scanning confined to breath-hold at deep inspiration. We studied the effect of respiratory triggering at deep inspiration levels on LV wall motion, wall thickening, LV volumes and ejection fraction (LVEF) compared to regular MPI without respiratory triggering. Results: Compared to regular MPI without respiratory triggering, systolic and diastolic LV volumes and stroke volumes decreased significantly (P<0.05) when respiratory triggering was applied. By contrast, there was no significant change in LVEF, with a high correlation (r=.939, P<0.001) between the two measurements. Furthermore, respiratory triggering introduced a significant change (P<0.05) in regional LV wall motion. Conclusions: Respiratory-triggered MPI with breath-hold at deep inspiration levels introduces significant changes to the measured LV volumes, stroke volumes and regional wall motion but does not significantly affect global LVEF when compared to regular MPI with normal breathin

Non-invasive assessment of coronary artery disease with CT coronary angiography and SPECT: a novel dose-saving fast-track algorithm

Purpose: To validate a new low-dose and rapid stepwise individualized algorithm for non-invasive assessment of ischemic coronary artery disease by sequential use of prospectively ECG-triggered low-dose CT coronary angiography (CTCA) and low-dose single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI). Methods: Forty patients referred for elective invasive coronary angiography (CA) were prospectively enrolled to undergo a comprehensive non-invasive evaluation with low-dose CTCA and a dose-reduced stress/rest SPECT-MPI scan (using dedicated reconstruction algorithms for low count scans). The following algorithm was reviewed: CTCA first, followed by a stress-only MPI if a coronary stenosis (≥ 50% diameter narrowing) or equivocal findings were observed. Only abnormal stress MPI scans were followed by rest MPI. The accuracy of the individualized algorithm to predict coronary revascularization and its mean effective radiation dose were assessed. Results: CTCA documented CAD in 18 and equivocal findings in two patients, thus, requiring additional stress MPI scans. Of these, 16 were abnormal, therefore requiring a rest MPI scan, revealing ischemia in 15 patients. Sensitivity, specificity, negative and positive predictive value, and accuracy of the individualized algorithm for predicting coronary revascularization was 93.3%, 96.0%, 96.0%, 93.3% and 95.0% on a per-patient base. The mean effective radiation dose was significantly lower for the individualized (4.8 ± 3.4mSv) versus the comprehensive method (8.1 ± 1.5mSv) resulting in a total population radiation dose reduction of 132.6mSv. Conclusion: This new individualized low-dose algorithm allows rapid and accurate prediction of invasive CA findings and of treatment decision with minimized radiation dos

Impact of CT attenuation correction on the viability pattern assessed by 99mTc-tetrofosmin SPECT/18F-FDG PET

SPECT myocardial perfusion imaging (MPI) is commonly used for comprehensive interpretation of metabolic PET FDG imaging in ischemic dysfunctional myocardium. We evaluated the difference in scan interpretation introduced by CT attenuation correction (CTAC) of SPECT MPI in patients undergoing viability characterization by 99mTc SPECT MPI/PET FDG. In 46 consecutive patients (mean age 64, range 36-83 years) with dysfunctional myocardium, we analyzed viability from combined SPECT MPI and PET FDG scanning without attenuation correction (NC) and with CTAC for SPECT MPI. FDG uptake was classified in groups of percent uptake using the segment with maximum tracer in SPECT perfusion uptake as reference. Viability patterns were categorized as normal, mismatch, mild match and scar by relative comparison of SPECT and PET. Applying CTAC introduced a different reference segment for the normalization of PET FDG study in 57% of cases. As a result, the flow-metabolism pattern changed in 28% of segments, yielding a normal, mismatch, mild match and scar pattern in 462, 150, 123, and 47 segments with NC and 553, 86, 108, and 35 with CTAC, respectively (P=0.001). Thus, by introducing CTAC for SPECT MPI 25% of segments originally classified as scar were reclassified and the number of normal segments increased by 20%. Introducing CTAC decreased by 54% the number of patients with possible indication for revascularization, from 26/46 to 12/46 (P<0.001). Different interpretation of myocardial viability can be observed when using CTAC instead of NC SPECT MPI as reference for PET FDG scan

Coronary calcium score scans for attenuation correction of quantitative PET/CT 13N-ammonia myocardial perfusion imaging

Purpose: The aim of this study was to evaluate whether ECG-triggered coronary calcium scoring (CCS) scans can be used for attenuation correction (AC) to quantify myocardial blood flow (MBF) and coronary flow reserve (CFR) assessed by PET/CT with 13N-ammonia. Methods: Thirty-five consecutive patients underwent a 13N-ammonia PET/CT scan at rest and during standard adenosine stress. MBF values were calculated using AC maps obtained from the ECG-triggered CCS scan during inspiration and validated against MBF values calculated using standard non-gated transmission scans for AC. CFR was calculated as the ratio of hyperaemic over resting MBF. In all 35 consecutive patients intraobserver variability was assessed by blinded repeat analysis for both AC methods. Results: There was an excellent correlation between CT AC and CCS for global MBF values at rest (n = 35, r = 0.94, p < 0.001) and during stress (n = 35, r = 0.97, p < 0.001) with narrow Bland-Altman (BA) limits of agreement (−0.21 to 0.10ml/min per g and −0.41 to 0.30ml/min per g) as well as for global CFR (n = 35, r = 0.96, p < 0.001, BA −0.27 to 0.34). The excellent correlation was preserved on the segmental MBF analysis for both rest and stress (n = 1190, r = 0.93, p < 0.001, BA −0.60 to 0.50) and for CFR (n = 595, r = 0.87, p < 0.001, BA −0.71 to 0.74). In addition, reproducibility proved excellent for global CFR by CT AC (n = 35, r = 0.91, p < 0.001, BA −0.42-0.58) and CCS scans (n = 35, r = 0.94, p < 0.001, BA −0.34-0.45). Conclusion: Use of attenuation maps from CCS scans allows accurate quantitative MBF and CFR assessment with 13N-ammonia PET/C