Mita Patel

Non-invasive assessment of the haemodynamic significance of coronary stenosis using fusion of cardiac computed tomography and 3D echocardiography

Aims Abnormal computed tomography coronary angiography (CTCA) often leads to stress testing to determine haemodynamic significance of stenosis. We hypothesized that instead, this could be achieved by fusion imaging of the coronary anatomy with 3D echocardiography (3DE)-derived resting myocardial deformation. Methods and results We developed fusion software that creates combined 3D displays of the coronary arteries with colour maps of longitudinal strain and tested it in 28 patients with chest pain, referred for CTCA (256 Philips scanner) who underwent 3DE (Philips iE33) and regadenoson stress CT. To obtain a reference for stenosis significance, coronaries were also fused with colour maps of stress myocardial perfusion. 3D displays were used to detect stress perfusion defect (SPD) and/or resting strain abnormality (RSA) in each territory. CTCA showed 56 normal arteries, stenosis <50% in 17, and >50% in 8 arteries. Of the 81 coronary territories, SPDs were noted in 20 and RSAs in 29. Of the 59 arteries with no stenosis >50% and no SPDs, considered as normal, 12 (20%) had RSAs. Conversely, with stenosis >50% and SPDs (haemodynamically significant), RSAs were considerably more frequent (5/6 = 83%). Overall, resting strain and stress perfusion findings were concordant in 64/81 arteries (79% agreement). Conclusions Fusion of CTCA and 3DE-derived data allows direct visualization of each coronary artery and strain in its territory. In this feasibility study, resting strain showed good agreement with stress perfusion, indicating that it may be potentially used to assess haemodynamic impact of coronary stenosis, as an alternative to stress testing that entails additional radiation exposure.

Role of Perfusion at Rest in the Diagnosis of Myocardial Infarction Using Vasodilator Stress Cardiovascular Magnetic Resonance

In clinical practice, perfusion at rest in vasodilator stress single-photon emission computed tomography is commonly used to confirm myocardial infarction (MI) and ischemia and to rule out artifacts. It is unclear whether perfusion at rest carries similar information in cardiovascular magnetic resonance (CMR). We sought to determine whether chronic MI is associated with abnormal perfusion at rest on CMR. We compared areas of infarct and remote myocardium in 31 patients who underwent vasodilator stress CMR (1.5 T), had MI confirmed by late gadolinium enhancement (LGE scar), and coronary angiography within 6 months. Stress perfusion imaging during gadolinium first pass was followed by reversal with aminophylline (75 to 125 mg), rest perfusion, and LGE imaging. Resting and peak-stress time-intensity curves were used to obtain maximal upslopes (normalized by blood pool upslopes), which were compared between infarcted and remote myocardial regions of interest. At rest, there was no significant difference between the slopes in the regions of interest supplied by arteries with and without stenosis >70% (0.31 ± 0.16 vs 0.26 ± 0.15 1/s), irrespective of LGE scar. However, at peak stress, we found significant differences (0.20 ± 0.11 vs 0.30 ± 0.22 1/s; p <0.05), reflecting the expected stress-induced ischemia. Similarly, at rest, there was no difference between infarcted and remote myocardium (0.27 ± 0.14 vs 0.30 ± 0.17 1/s), irrespective of stenosis, but significant differences were seen during stress (0.21 ± 0.16 vs 0.28 ± 0.18 1/s; p <0.001), reflecting inducible ischemia. In conclusion, abnormalities in myocardial perfusion at rest associated with chronic MI are not reliably detectable on CMR images. Accordingly, unlike single-photon emission computed tomography, normal CMR perfusion at rest should not be used to rule out chronic MI.

Fusion of Three-Dimensional Echocardiographic Regional Myocardial Strain with Cardiac Computed Tomography for Noninvasive Evaluation of the Hemodynamic Impact of Coronary Stenosis in Patients with Chest Pain

Background Combined evaluation of coronary stenosis and the extent of ischemia is essential in patients with chest pain. Intermediate‐grade stenosis on computed tomographic coronary angiography (CTCA) frequently triggers downstream nuclear stress testing. Alternative approaches without stress and/or radiation may have important implications. Myocardial strain measured from echocardiographic images can be used to detect subclinical dysfunction. The authors recently tested the feasibility of fusion of three‐dimensional (3D) echocardiography–derived regional resting longitudinal strain with coronary arteries from CTCA to determine the hemodynamic significance of stenosis. The aim of the present study was to validate this approach against accepted reference techniques. Methods Seventy‐eight patients with chest pain referred for CTCA who also underwent 3D echocardiography and regadenoson stress computed tomography were prospectively studied. Left ventricular longitudinal strain data (TomTec) were used to generate fused 3D displays and detect resting strain abnormalities (RSAs) in each coronary territory. Computed tomographic coronary angiographic images were interpreted for the presence and severity of stenosis. Fused 3D displays of subendocardial x‐ray attenuation were created to detect stress perfusion defects (SPDs). In patients with stenosis >25% in at least one artery, fractional flow reserve was quantified (HeartFlow). RSA as a marker of significant stenosis was validated against two different combined references: stenosis >50% on CTCA and SPDs seen in the same territory (reference standard A) and fractional flow reserve < 0.80 and SPDs in the same territory (reference standard B). Results Of the 99 arteries with no stenosis >50% and no SPDs, considered as normal, 19 (19%) had RSAs. Conversely, with stenosis >50% and SPDs, RSAs were considerably more frequent (17 of 24 [71%]). The sensitivity, specificity, and accuracy of RSA were 0.71, 0.81, and 0.79, respectively, against reference standard A and 0.83, 0.81, and 0.82 against reference standard B. Conclusions Fusion of CTCA and 3D echocardiography–derived resting myocardial strain provides combined displays, which may be useful in determination of the hemodynamic or functional impact of coronary abnormalities, without additional ionizing radiation or stress testing. HighlightsWe studied patients with chest pain.CT angiography fusion with 3D echocardiography derived resting myocardial strain.Strain abnormalities correlated with perfusion defects on vasodilator stress CT.Strain abnormalities correlated with reduced noninvasive fractional flow reserve.Image fusion may help determine the hemodynamic impact of coronary artery disease.

A fast, noniterative approach for accelerated high‐temporal resolution cine‐CMR using dynamically interleaved streak removal in the power‐spectral encoded domain with low‐pass filtering (DISPEL) and modulo‐prime spokes (MoPS)

Purpose To introduce a pair of accelerated non‐Cartesian acquisition principles that when combined, exploit the periodicity of k‐space acquisition, and thereby enable acquisition of high‐temporal cine Cardiac Magnetic Resonance (CMR). Methods The mathematical formulation of a noniterative, undersampled non‐Cartesian cine acquisition and reconstruction is presented. First, a low‐pass filtering step that exploits streaking artifact redundancy is provided (i.e., Dynamically Interleaved Streak removal in the Power‐spectrum Encoded domain with Low‐pass filtering [DISPEL]). Next, an effective radial acquisition for the DISPEL approach that exploits the property of prime numbers is described (i.e., Modulo‐Prime Spoke [MoPS]). Both DISPEL and MoPS are examined using numerical simulation of a digital heart phantom to show that high‐temporal cine‐CMR is feasible without removing physiologic motion vs aperiodic interleaving using Golden Angles. The combined high‐temporal cine approach is next examined in 11 healthy subjects for a time–volume curve assessment of left ventricular systolic and diastolic performance vs conventional Cartesian cine‐CMR reference. Results The DISPEL method was first shown using simulation under different streak cycles to allow separation of undersampled radial streaking artifacts from physiologic motion with a sufficiently frequent streak‐cycle interval. Radial interleaving with MoPS is next shown to allow interleaves with pseudo‐Golden‐Angle variants, and be more compatible with DISPEL against irrational and nonperiodic rotation angles, including the Golden‐Angle‐derived rotations. In the in vivo data, the proposed method showed no statistical difference in the systolic performance, while diastolic parameters sensitive to the cines temporal resolution were statistically significant (P < 0.05 vs Cartesian cine). Conclusions We demonstrate a high‐temporal resolution cine‐CMR using DISPEL and MoPS, whose streaking artifact was separated from physiologic motion.

3D late gadolinium enhanced cardiovascular MR with CENTRA-PLUS profile/view ordering: Feasibility of right ventricular myocardial damage assessment using a swine animal model

AIMS To develop a high-resolution, 3D late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (MRI) technique for improved assessment of myocardial scars, and evaluate its performance against 2D breath-held (BH) LGE MRI using a surgically implanted animal scar model in the right ventricle (RV). METHODS AND RESULTS A k-space segmented 3D LGE acquisition using CENTRA-PLUS (Contrast ENhanced Timing Robust Acquisition with Preparation of LongitUdinal Signal; or CP) ordering is proposed. 8 pigs were surgically prepared with cardiac patch implantation in the RV, followed in 60days by 1.5T MRI. LGE with Phase-Sensitive Inversion Recovery (PSIR) were performed as follows: 1) 2DBH using pneumatic control, and 2) navigator-gated, 3D free-breathing (3DFB)-CP-LGE with slice-tracking. The animal heart was excised immediately after cardiac MR for scar volume quantification. RV scar volumes were also delineated from the 2DBH and 3DFB-CP-LGE images for comparison against the surgical standard. Apparent scar/normal tissue signal-to-noise ratio (aSNR) and contrast-to-noise ratio (aCNR) were also calculated. 3DFB-CP-LGE technique was successfully performed in all animals. No difference in aCNR was noted, but aSNR was significantly higher using the 3D technique (p<0.05). Against the surgical reference volume, the 3DFB-CP-LGE-derived delineation yielded significantly less volume quantification error compared to 2DBH-derived volumes (15±10% vs 55±33%; p<0.05). CONCLUSION Compared to conventional 2DBH-LGE, 3DFB-LGE acquisition using CENTRA-PLUS provided superior scar volume quantification and improved aSNR.

NONINVASIVE ASSESSMENT THE HEMODYNAMIC SIGNIFICANCE OF CORONARY STENOSIS USING FUSION OF CARDIAC COMPUTED TOMOGRAPHY AND 3D ECHOCARDIOGRAPHY

Abnormal coronary CT angiography (CCTA) often leads to stress testing to determine hemodynamic significance of stenosis. We hypothesized that instead this could be achieved by fusion of the coronary anatomy with 3D echocardiography (3DE) derived resting myocardial deformation. We developed fusion

Operator-guided Navigator Gating for Real-Time Interactive Coronary Cardiovascular Magnetic Resonance

Background Real-time interactive (RTI) MRI parameter manipulation during the scan [1] may potentially address challenges imposed by respiratory motion during a free-breathing cardiovascular magnetic resonance (CMR) acquisition. In this study, we propose an operator-guided processing that allows manipulation of navigator gating parameters in real-time. This approach was evaluated in healthy volunteers, where coronary CMR (CCMR) with and without RTI manipulation was examined to assess acquisition failure rates, scan time reduction, and vessel sharpness. Methods The proposed RTI framework employs a custom communication protocol between the scanner host and the waveform generation hardware that allows non-time-critical operator tasks (ie. made changes are reflected in the next collected heart beat without overtasking the scan runtime). The custom front-end (Figure 1a) shows the operator-interactive navigator control that allows manipulation of the diaphragm navigator gating window in real-time (Figure 1b). This RTI approach was incorporated into a CCMR sequence with view/profile order compatible with

Vasodilator stress cardiovascular magnetic resonance imaging in post-orthotopic heart transplant recipients: evaluation of safety, hemodynamics, and myocardial perfusion

Background Long-term survival after orthotopic heart transplant (OHT) is limited by coronary allograft vasculopathy and its associated myocardial perfusion abnormalities. Little is known how post-OHT patients respond to vasodilator stress cardiovascular magnetic resonance imaging (vsCMR). This study aimed (1) to evaluate the safety and hemodynamic response of post-OHT patients undergoing vsCMR with regadenoson and (2) to determine whether these patients have abnormalities in myocardial perfusion detectable by vsCMR.

Novel 3-Dimensional K-Space segmented acquisition scheme (CENTRA-PLUS) for enhanced coronary imaging

Background Bright-blood coronary artery imaging by cardiovascular magnetic resonance remains a challenge due to several factors including coronary tortuosity, cardiac and respiratory motion, and high demands in spatial resolution and image contrast. Cartesian CENTRA-PLUS for high-resolution 3D k-space acquisition sorts the different regions of segmented k-space at different timepoints of the ~5 minute scan (figure 1). This strategy is well-suited for various acceleration methods including GRAPPA, compressed sensing, and navigator strategies for scan time reduction that conventional centric acquisition strategies do not easily allow. The aim of this study is to perform a direct comparison of CENTRAPLUS against the conventional centric acquisition for coronary CMR.

Diagnostic performance of regadenoson stress CMR for detection of coronary artery disease.

Background The diagnostic performance of cardiovascular magnetic resonance (CMR) utilizing adenosine for detection of myocardial ischemia is well established. However, adenosine requires continuous infusion, which is challenging in the CMR environment, and has frequent side effects. The diagnostic accuracy of stress CMR using regadenoson, a newer vasodilator agent that is administered as a single bolus injection and has fewer side effects, has not been well studied. The aims of this study were: (1) to determine the diagnostic accuracy of regadenoson stress CMR when compared to coronary angiography in patients with suspected coronary artery disease (CAD), and (2) to study outcomes in patients with negative stress CMR perfusion studies to confirm that there are not a significant number of “abnormal studies” that are undetected.