NT-proBNP levels in the evaluation of right ventricular dysfunction in patients with coronary artery disease and abnormal left ventricular wall motion: a magnetic resonance imaging study

BACKGROUND: Data available on the correlation of N-terminal probrain natriuretic peptide (NT-proBNP) levels and right ventricular (RV) function in patients with coronary artery disease (CAD) are limited. OBJECTIVE: To determine the relation between plasma NT-proBNP and RV function in patients with CAD and abnormal left ventricular (LV) wall motion. METHODS: This is a cross-sectional study. We studied 176 patients with CAD and abnormal LV wall motion. All patients underwent cardiac magnetic resonance imaging for the assessment of LV and RV function and plasma NT-proBNP analysis on the same day. Multivariable analysis was performed to evaluate the independent factors associated with RV dysfunction. Receiver-operating characteristic analysis was used to assess the use of NT-proBNP levels for the diagnosis of LV and RV dysfunction. RESULTS: Average LV ejection fraction (LVEF) and RV ejection fraction were 37.6 and 52.0%, respectively. Median levels of NT-proBNP were 978 pg/ml. Log NT-proBNP levels had a positive correlation with age, LV and RV volume, LV and RV mass, and had a negative correlation with body size, creatinine clearance, LVEF, and RV ejection fraction. From a multivariable analysis, log NT-proBNP levels and LVEF were independently associated with RV dysfunction. From receiver-operating characteristic analysis, NT-proBNP at the levels of 1706 and 378 pg/ml was shown to detect RV dysfunction and LV dysfunction at an accuracy of 80.7 and 77.8% and area under the curve of 0.837 and 0.765, respectively. CONCLUSION: NT-proBNP levels can be used to diagnose RV dysfunction in patients with CAD and abnormal LV wall motion.     

Magnetic resonance imaging abnormalities in right ventricular outflow tract tachycardia and the prediction of radiofrequency ablation outcome

BACKGROUND: Recent reports have shown abnormalities on cardiac magnetic resonance imaging (MRI) in patients with right ventricular outflow tract (RVOT) tachycardia. Objectives: Objectives of this study were to demonstrate abnormalities on MRI and signal-averaged ECG (SAECG) in patients with RVOT tachycardia and their correlation with the outcome of radiofrequency (RF) ablation. METHODS: We studied 41 patients with symptomatic RVOT tachycardia and 15 controls. SAECG and cardiac MRI were performed on every subject. An evaluation of structural abnormality, chamber size, function, and wall motion abnormality of the left and right ventricle was performed by MRI. Focal wall thinning was evaluated by the black blood technique and fatty infiltration was evaluated by the T1 image with and without fat suppression. RESULTS: MRI abnormalities were demonstrated in 24 (58.5%) patients with RVOT tachycardia. The abnormalities included localized wall bulging in 22 (53.7%), focal wall thinning in 10 (24.4%), and fatty replacement in 9 (22%) patients. MRI abnormality was found in only one patient in the control group (P < 0.001). Late potentials from SAECG were demonstrated in six (10.7%) patients but none in the controls (P = 0.117). Among 29 patients who underwent RF ablation, 3 patients had a failed procedure and 3 having arrhythmia recurrence needed repeated ablation. MRI abnormalities and late potentials were associated with an unfavorable outcome of RF ablation. CONCLUSIONS: MRI abnormalities were frequently found in patients with RVOT tachycardia. MRI abnormalities and late potentials can predict outcomes of RF ablation.     

Prevalence and prognosis of myocardial scar in patients with known or suspected coronary artery disease and normal wall motion

Background

Some patients may have normal wall motion after myocardial infarction. The aim of this study was to determine the prevalence and prognosis of patients with myocardial scar in the absence of abnormal wall motion. We studied patients with suspected or known coronary artery disease (CAD) who were referred for cardiovascular magnetic resonance (CMR) for the assessment of global and regional cardiac function and late gadolinium enhancement (LGE) and had normal left ventricular wall motion. Prognostic value was determined by the occurrence of hard endpoints (cardiac death and nonfatal myocardial infarction) and major adverse cardiac events (MACE) which also included hospitalization due to unstable angina or heart failure or life threatening ventricular arrhythmia.

Results

A total 1148 patients (70.3%) were studied. LGE was detected in 104 patients (9.1%). Prevalence of LGE increased in patients with increased left ventricular mass. Average follow-up time was 955 ± 542 days. LGE was the strongest predictor for hard endpoints and MACE.

Conclusion

LGE was detected in 9.1% of patients with suspected or known CAD and normal wall motion. LGE was the strongest predictor of significant cardiac events.     

MRI monitoring of laser ablation using optical flow

The optical flow method is used for visualizing and quantifying the dynamics of tissue changes observed by MRI during thermal ablations. An approach was implemented for parallel two-dimensional optical flow calculations including the replacement of spurious velocities. Velocity magnitude results were found to be accurate in low-noise cases in tests using series of synthetic images. Optical flow results are presented from thermal ablation experiments utilizing a homogeneous polyacrylamide gel phantom and heterogeneous rabbit liver tissue in vivo, exhibiting heating and cooling with the accompanying quantitative characterization of the dilation and contraction of the thermally affected region. Results demonstrate that optical flow is capable of noninvasive real-time monitoring and control of interstitial laser therapy (ILT).     

Digital wavelet-encoded MRI: A new wavelet-encoding methodology

A new digital wavelet-encoding method for MRI is described. The method differs from previously described wavelet-encoding approaches, because the pointspread function is made independent of the wavelet basis used. This has a significant practical advantage, because wavelet bases can now be considered that would otherwise be excluded due to the difficulty of precisely exciting wavelet-shaped RF profiles. The method has been implemented on a clinical MRI system, and human images are presented.     

Monitoring and visualization techniques for MR-guided laser ablations in an open MR system

Our purpose was to develop temperature-sensitive MR sequences and image-processing techniques to assess their potential of monitoring interstitial laser therapy (ILT) in brain tumors (n = 3) and liver tumors (n = 7). ILT lasted 2 to 26 minutes, whereas images from T1-weighted fast-spin-echo (FSE) or spoiled gradient-recalled (SPGR) sequences were acquired within 5 to 13 seconds. Pixel subtraction and visualization of T1-weighted images or optical flow computation was done within less than 110 msec. Alternating phase-mapping of real and imaginary components of SPGR sequences was performed within 220 msec. Pixel subtraction of T1-weighted images identified thermal changes in liver and brain tumors but could not evaluate the temperature values as chemical shift-based imaging, which was, however, more affected by susceptibility effects and motion. Optical flow computation displayed the predicted course of thermal changes and revealed that the rate of heat deposition can be anisotropic, which may be related to heterogeneous tumor structure and/or vascularization.     

Interactive 3-dimensional segmentation of MRI data in personal computer environment.

We describe a method of interactive three-dimensional segmentation and visualization for anatomical magnetic resonance imaging (MRI) data in a personal computer environment. The visual feedback necessary during 3-D segmentation was provided by a ray casting algorithm, which was designed to allow users to interactively decide the visualization quality depending on the task-requirement. Structures such as gray matter, white matter, and facial skin from T1-weighted high-resolution MRI data were segmented and later visualized with surface rendering. Personal computers with central processing unit (CPU) speeds of 266, 400, and 700 MHz, were used for the implementation. The 3-D visualization upon each execution of the segmentation operation was achieved in the order of 2 s with a 700 MHz CPU. Our results suggest that 3-D volume segmentation with semi real-time visual feedback could be effectively implemented in a PC environment without the need for dedicated graphics processing hardware.