Amedeo Chiribiri

Quantification of absolute myocardial perfusion in patients with coronary artery disease: comparison between cardiovascular magnetic resonance and positron emission tomography

OBJECTIVES The aim of this study was to compare fully quantitative cardiovascular magnetic resonance (CMR) and positron emission tomography (PET) myocardial perfusion and myocardial perfusion reserve (MPR) measurements in patients with coronary artery disease (CAD). BACKGROUND Absolute quantification of myocardial perfusion and MPR with PET have proven diagnostic and prognostic roles in patients with CAD. Quantitative CMR perfusion imaging has been established more recently and has been validated against PET in normal hearts. However, there are no studies comparing fully quantitative CMR against PET perfusion imaging in patients with CAD. METHODS Forty-one patients with known or suspected CAD prospectively underwent quantitative (13)N-ammonia PET and CMR perfusion imaging before coronary angiography. RESULTS The CMR-derived MPR (MPR(CMR)) correlated well with PET-derived measurements (MPR(PET)) (r = 0.75, p < 0.0001). MPR(CMR) and MPR(PET) for the 2 lowest scoring segments in each coronary territory also correlated strongly (r = 0.79, p < 0.0001). Absolute CMR perfusion values correlated significantly, but weakly, with PET values both at rest (r = 0.32; p = 0.002) and during stress (r = 0.37; p < 0.0001). Area under the receiver-operating characteristic curve for MPR(PET) to detect significant CAD was 0.83 (95% confidence interval: 0.73 to 0.94) and for MPR(CMR) was 0.83 (95% confidence interval: 0.74 to 0.92). An MPR(PET) ≤1.44 predicted significant CAD with 82% sensitivity and 87% specificity, and MPR(CMR) ≤1.45 predicted significant CAD with 82% sensitivity and 81% specificity. CONCLUSIONS There is good correlation between MPR(CMR) and MPR(PET.) For the detection of significant CAD, MPR(PET) and MPR(CMR) seem comparable and very accurate. However, absolute perfusion values from PET and CMR are only weakly correlated; therefore, although quantitative CMR is clinically useful, further refinements are still required.

High-Resolution Magnetic Resonance Myocardial Perfusion Imaging at 3.0-Tesla to Detect Hemodynamically Significant Coronary Stenoses as Determined by Fractional Flow Reserve

OBJECTIVES The objective of this study was to compare visual and quantitative analysis of high spatial resolution cardiac magnetic resonance (CMR) perfusion at 3.0-T against invasively determined fractional flow reserve (FFR). BACKGROUND High spatial resolution CMR myocardial perfusion imaging for the detection of coronary artery disease (CAD) has recently been proposed but requires further clinical validation. METHODS Forty-two patients (33 men, age 57.4 ± 9.6 years) with known or suspected CAD underwent rest and adenosine-stress k-space and time sensitivity encoding accelerated perfusion CMR at 3.0-T achieving in-plane spatial resolution of 1.2 × 1.2 mm(2). The FFR was measured in all vessels with >50% severity stenosis. Fractional flow reserve <0.75 was considered hemodynamically significant. Two blinded observers visually interpreted the CMR data. Separately, myocardial perfusion reserve (MPR) was estimated using Fermi-constrained deconvolution. RESULTS Of 126 coronary vessels, 52 underwent pressure wire assessment. Of these, 27 lesions had an FFR <0.75. Sensitivity and specificity of visual CMR analysis to detect stenoses at a threshold of FFR <0.75 were 0.82 and 0.94 (p < 0.0001), respectively, with an area under the receiver-operator characteristic curve of 0.92 (p < 0.0001). From quantitative analysis, the optimum MPR to detect such lesions was 1.58, with a sensitivity of 0.80, specificity of 0.89 (p < 0.0001), and area under the curve of 0.89 (p < 0.0001). CONCLUSIONS High-resolution CMR MPR at 3.0-T can be used to detect flow-limiting CAD as defined by FFR, using both visual and quantitative analyses.

Direct Comparison of Cardiac Magnetic Resonance and Multidetector Computed Tomography Stress-Rest Perfusion Imaging for Detection of Coronary Artery Disease

OBJECTIVES This study sought to compare the diagnostic performance of a multidetector computed tomography (MDCT) integrated protocol (IP) including coronary angiography (CTA) and stress-rest perfusion (CTP) with cardiac magnetic resonance myocardial perfusion imaging (CMR-Perf) for detection of functionally significant coronary artery disease (CAD). BACKGROUND MDCT stress-rest perfusion methods were recently described as adjunctive tools to improve CTA accuracy for detection of functionally significant CAD. However, only a few studies compared these MDCT-IP with other clinically validated perfusion techniques like CMR-Perf. Furthermore, CTP has never been validated against the invasive reference standard, fractional flow reserve (FFR), in patients with suspected CAD. METHODS 101 symptomatic patients with suspected CAD (62 ± 8.0 years, 67% males) and intermediate/high pre-test probability underwent MDCT, CMR and invasive coronary angiography. Functionally significant CAD was defined by the presence of occlusive/subocclusive stenoses or FFR measurements ≤ 0.80 in vessels >2mm. RESULTS On a patient-based model, the MDCT-IP had a sensitivity, specificity, positive and negative predictive values of 89%, 83%, 80% and 90%, respectively (global accuracy 85%). These results were closely related with those achieved by CMR-Perf: 89%, 88%, 85% and 91%, respectively (global accuracy 88%). When comparing test accuracies using noninferiority analysis, differences greater than 11% in favour of CMR-Perf can be confidently excluded. CONCLUSIONS MDCT protocols integrating CTA and stress-rest perfusion detect functionally significant CAD with similar accuracy as CMR-Perf. Both approaches yield a very good accuracy. Integration of CTP and CTA improves MDCT performance for the detection of relevant CAD in intermediate to high pre-test probability populations.

Visualization of the Cardiac Venous System Using Cardiac Magnetic Resonance

We sought to investigate the value of cardiac magnetic resonance to depict cardiac venous anatomy. For cardiac resynchronization therapy the lead for the left ventricle is usually placed by transvenous approach into a tributary of the coronary sinus (CS). Knowledge of the anatomy and variations of the cardiac venous system may facilitate the positioning of the left ventricle lead. The cardiac magnetic resonance examinations of 23 subjects (16 volunteers and 7 patients) were retrospectively analyzed. All examinations were performed using navigator-gated whole-heart steady-state free precession coronary artery imaging after administration of intravascular contrast agents (gadofosveset in volunteers; Gadomer-17 in patients). The cardiac venous system was visualized in all subjects. The most frequent anatomical variant observed (in 12 subjects [52%]) was a connection of the small cardiac vein to the CS at the crux cordis. In 10 subjects (44%) the small veins entered the right atrium independently from the CS, and the posterior interventricular vein was connected to the CS at the crux cordis. Only one subject had a disconnection between the CS and posterior interventricular vein, which entered into the right atrium independently. The mean distance of the posterior vein of the left ventricle and the left marginal vein to the ostium of the CS was 15.2+/-4.7 mm and 49.7+/-14.1 mm, respectively. In conclusion, the anatomy of the cardiac venous system and its anatomical variability can be described using cardiac magnetic resonance. Its preimplantation visualization may help to facilitate the implant procedure and to reduce fluoroscopy time.

Cardiovascular magnetic resonance myocardial feature tracking for quantitative viability assessment in ischemic cardiomyopathy

BACKGROUND Low dose dobutamine stress magnetic resonance imaging is valuable to assess viability in patients with ischemic cardiomyopathy. Analysis is usually qualitative with considerable operator dependency. The aim of the current study was to investigate the feasibility of cine images derived quantitative cardiac magnetic resonance (CMR) myocardial feature tracking (FT) strain parameters to assess viability in patients with ischemic cardiomyopathy. METHODS 15 consecutive patients with ischemic cardiomyopathy referred for viability assessment were studied at 3T at rest and during low dose dobutamine stress (5 and 10μg/kg/min of dobutamine). Subendocardial and subepicardial circumferential (Eccendo and Eccepi) and radial (Err) strains were assessed using steady state free precession (SSFP) cine images orientated in 3 short axis slices covering 16 myocardial segments. RESULTS Dysfunctional segments without scar (n=75) improved in all three strain parameters: Eccendo (Rest: -10.5±6.9; 5μg: -12.1±6.9; 10μg: -14.1±9.2; p<0.05), Eccepi (Rest: -7±4.8; 5μg: -8.2±5.5; 10μg: -9.1±5.9; p<0.05) and Err (Rest: 11.7±8.3; 5μg: 16±10.9; 10μg: 16.5±12.8; p<0.05). There was no response to dobutamine in dysfunctional segments with scar transmurality above 75% (n=6): Eccendo (Rest: -4.7±3.0; 5μg: -2.9±2.5; 10μg: -6.6±3.3; p=ns), Eccepi (Rest: -2.9±2.9; 5μg: -5.4±3.9; 10μg: -4.5±4.2; p=ns) and Err (Rest:9.5±5; 5μg:5.4±6.2; 10μg:4.9±3.3; p=ns). Circumferential strain (Eccendo, Eccepi) improved in all segments up to a transmurality of 75% (n=60; p<0.05). Err improved in segments <50% transmurality (n=45; p<0.05) and remained unchanged above 50% transmurality (n=21; p=ns). CONCLUSIONS CMR-FT is a novel technique, which detects quantitative wall motion derived from SSFP cine imaging at rest and with low dose dobutamine stress. CMR-FT holds promise of quantitative assessment of viability in patients with ischemic cardiomyopathy.

Imaging in the Management of Ischemic Cardiomyopathy Special Focus on Magnetic Resonance

Heart failure of ischemic origin has become increasingly common over the last decade because of the improved survival of patients with acute myocardial infarction. Revascularization with coronary bypass grafting or percutaneous coronary intervention plays a pivotal role in patients with ischemic cardiomyopathy, although these interventions are often associated with relatively high peri-procedural risk. The pathophysiological substrate of ischemic cardiomyopathy is heterogeneous, varying from predominantly hibernating myocardium to irreversible scarring. There is evidence to suggest that patients with hibernating myocardium benefit most from revascularization, whereas medical therapy is associated with an adverse prognosis. Therefore, noninvasive testing is recommended by relevant guidelines to guide optimal management in these patients. However, the role of noninvasive testing has recently been challenged. There are various imaging modalities available that provide information on different aspects of the disease, and therefore, they differ significantly in sensitivity and specificity. In clinical practice, choosing among the different imaging modalities can be difficult. Cardiac magnetic resonance has evolved into a comprehensive modality that can accurately determine the amount of hibernating myocardium as well as the presence and degree of myocardial ischemia and the extent of the scar. This paper reviews the indications, accuracy, and clinical utility of the available imaging techniques, with a special focus on cardiac magnetic resonance in ischemic cardiomyopathy, and provides an outlook on how this field might evolve in the future.

Cardiac magnetic resonance and electroanatomical mapping of acute and chronic atrial ablation injury: a histological validation study

AIMS To provide a comprehensive histopathological validation of cardiac magnetic resonance (CMR) and endocardial voltage mapping of acute and chronic atrial ablation injury. METHODS AND RESULTS 16 pigs underwent pre-ablation T2-weighted (T2W) and late gadolinium enhancement (LGE) CMR and high-density voltage mapping of the right atrium (RA) and both were repeated after intercaval linear radiofrequency ablation. Eight pigs were sacrificed following the procedure for pathological examination. A further eight pigs were recovered for 8 weeks, before chronic CMR, repeat RA voltage mapping and pathological examination. Signal intensity (SI) thresholds from 0 to 15 SD above a reference SI were used to segment the RA in CMR images and segmentations compared with real lesion volumes. The SI thresholds that best approximated histological volumes were 2.3 SD for LGE post-ablation, 14.5 SD for T2W post-ablation and 3.3 SD for LGE chronically. T2-weighted chronically always underestimated lesion volume. Acute histology showed transmural injury with coagulative necrosis. Chronic histology showed transmural fibrous scar. The mean voltage at the centre of the ablation line was 3.3 mV pre-ablation, 0.6 mV immediately post-ablation, and 0.3 mV chronically. CONCLUSION This study presents the first histopathological validation of CMR and endocardial voltage mapping to define acute and chronic atrial ablation injury, including SI thresholds that best match histological lesion volumes. An understanding of these thresholds may allow a more informed assessment of the underlying atrial substrate immediately after ablation and before repeat catheter ablation for atrial arrhythmias.

Quantification of left atrial strain and strain rate using Cardiovascular Magnetic Resonance myocardial feature tracking: a feasibility study

BackgroundCardiovascular Magnetic Resonance myocardial feature tracking (CMR-FT) is a quantitative technique tracking tissue voxel motion on standard steady-state free precession (SSFP) cine images to assess ventricular myocardial deformation. The importance of left atrial (LA) deformation assessment is increasingly recognized and can be assessed with echocardiographic speckle tracking. However atrial deformation quantification has never previously been demonstrated with CMR. We sought to determine the feasibility and reproducibility of CMR-FT for quantitative derivation of LA strain and strain rate (SR) myocardial mechanics.Methods10 healthy volunteers, 10 patients with hypertrophic cardiomyopathy (HCM) and 10 patients with heart failure and preserved ejection fraction (HFpEF) were studied at 1.5 Tesla. LA longitudinal strain and SR parameters were derived from SSFP cine images using dedicated CMR-FT software (2D CPA MR, TomTec, Germany). LA performance was analyzed using 4- and 2-chamber views including LA reservoir function (total strain [εs], peak positive SR [SRs]), LA conduit function (passive strain [εe], peak early negative SR [SRe]) and LA booster pump function (active strain [εa], late peak negative SR [SRa]).ResultsIn all subjects LA strain and SR parameters could be derived from SSFP images. There was impaired LA reservoir function in HCM and HFpEF (εs [%]: HCM 22.1 ± 5.5, HFpEF 16.3 ± 5.8, Controls 29.1 ± 5.3, p < 0.01; SRs [s-1]: HCM 0.9 ± 0.2, HFpEF 0.8 ± 0.3, Controls 1.1 ± 0.2, p < 0.05) and impaired LA conduit function as compared to healthy controls (εe [%]: HCM 10.4 ± 3.9, HFpEF 11.9 ± 4.0, Controls 21.3 ± 5.1, p < 0.001; SRe [s-1]: HCM -0.5 ± 0.2, HFpEF -0.6 ± 0.1, Controls -1.0 ± 0.3, p < 0.01). LA booster pump function was increased in HCM while decreased in HFpEF (εa [%]: HCM 11.7 ± 4.0, HFpEF 4.5 ± 2.9, Controls 7.8 ± 2.5, p < 0.01; SRa [s-1]: HCM -1.2 ± 0.4, HFpEF -0.5 ± 0.2, Controls -0.9 ± 0.3, p < 0.01). Observer variability was excellent for all strain and SR parameters on an intra- and inter-observer level as determined by Bland-Altman, coefficient of variation and intraclass correlation coefficient analyses.ConclusionsCMR-FT based atrial performance analysis reliably quantifies LA longitudinal strain and SR from standard SSFP cine images and discriminates between patients with impaired left ventricular relaxation and healthy controls. CMR-FT derived atrial deformation quantification seems a promising novel approach for the study of atrial performance and physiology in health and disease states.

Design and rationale of the MR-INFORM study: stress perfusion cardiovascular magnetic resonance imaging to guide the management of patients with stable coronary artery disease

BackgroundIn patients with stable coronary artery disease (CAD), decisions regarding revascularisation are primarily driven by the severity and extent of coronary luminal stenoses as determined by invasive coronary angiography. More recently, revascularisation decisions based on invasive fractional flow reserve (FFR) have shown improved event free survival. Cardiovascular magnetic resonance (CMR) perfusion imaging has been shown to be non-inferior to nuclear perfusion imaging in a multi-centre setting and superior in a single centre trial. In addition, it is similar to invasively determined FFR and therefore has the potential to become the non-invasive test of choice to determine need for revascularisation.Trial designThe MR-INFORM study is a prospective, multi-centre, randomised controlled non-inferiority, outcome trial. The objective is to compare the efficacy of two investigative strategies for the management of patients with suspected CAD. Patients presenting with stable angina are randomised into two groups: 1) The FFR-INFORMED group has subsequent management decisions guided by coronary angiography and fractional flow reserve measurements. 2) The MR-INFORMED group has decisions guided by stress perfusion CMR. The primary end-point will be the occurrence of major adverse cardiac events (death, myocardial infarction and repeat revascularisation) at one year. Clinical trials.gov identifier NCT01236807.ConclusionMR INFORM will assess whether an initial strategy of CMR perfusion is non-inferior to invasive angiography supplemented by FFR measurements to guide the management of patients with stable coronary artery disease. Non-inferiority of CMR perfusion imaging to the current invasive reference standard (FFR) would establish CMR perfusion imaging as an attractive non-invasive alternative to current diagnostic pathways.

Long-Term Prognostic Value of Dobutamine Stress CMR

OBJECTIVES The aim of this study was to assess the long-term value of high-dose dobutamine cardiac magnetic resonance (DCMR) for the prediction of cardiac events in a large cohort of patients with known or suspected coronary artery disease. BACKGROUND High-dose DCMR has been shown to be a useful technique for diagnosis and intermediate-term prognostic stratification. METHODS Clinical data and DCMR results were analyzed in 1,463 consecutive patients undergoing DCMR between 2000 and 2004. Ninety-four patients were lost to follow-up. The remaining 1,369 patients were followed up for a mean of 44 ± 24 months. Cardiac events, defined as cardiac death and nonfatal myocardial infarction, were related to clinical and DCMR results. RESULTS Three-hundred fifty-two patients underwent early revascularization (≤ 3 months of DCMR) and were excluded from analysis. Of the remaining 1,017 patients, 301 patients (29.6%) experienced inducible wall motion abnormalities (WMA). Forty-six cardiac events were reported. In those with and without inducible WMA, the proportion of patients with cardiac events was 8.0% versus 3.1%, respectively, p = 0.001 (hazard ratio: 3.3; 95% confidence interval: 1.8 to 5.9 for the presence of inducible WMA; p < 0.001). A DCMR without inducible WMA carried an excellent prognosis, with a 6-year cardiac event-free survival of 96.8%. In all 1,369 patients in the patient group with stress-inducible WMA, those patients with medical therapy demonstrated a trend to a higher cardiac event rate (8.0%) than those with early revascularization (5.4%) (p = 0.234). Patients with normal DCMR and medical therapy or early revascularization demonstrated similar cumulative cardiac event rates (3.1% vs. 3.2%, p = 0.964). CONCLUSIONS In a large cohort of patients, DCMR has an added value for predicting cardiac events during long-term follow-up, improving the differentiation between high-risk and low-risk patients. Patients with inducible WMA and following early revascularization, demonstrate lower cardiac event rates than patients with medical therapy alone.