Jana G. Delfino

Cardiovascular magnetic resonance at 3.0T: Current state of the art

There are advantages to conducting cardiovascular magnetic resonance (CMR) studies at a field strength of 3.0 Telsa, including the increase in bulk magnetization, the increase in frequency separation of off-resonance spins, and the increase in T1 of many tissues. However, there are significant challenges to routinely performing CMR at 3.0T, including the reduction in main magnetic field homogeneity, the increase in RF power deposition, and the increase in susceptibility-based artifacts.In this review, we outline the underlying physical effects that occur when imaging at higher fields, examine the practical results these effects have on the CMR applications, and examine methods used to compensate for these effects. Specifically, we will review cine imaging, MR coronary angiography, myocardial perfusion imaging, late gadolinium enhancement, and vascular wall imaging.

It's Time for a Paradigm Shift in the Quantitative Evaluation of Left Ventricular Dyssynchrony

The acute adverse effects of left ventricular (LV) dyssynchrony on cardiac performance were first described in 1925 by Carl Wiggers1. In recent years, the accurate diagnosis of LV dyssynchrony has become the focus of a myriad of publications, driven by the advent of cardiac resynchronization therapy (CRT) to treat heart failure due to severe LV dysfunction in the setting of marked prolongation of the QRS interval2–4. In the initial large clinical trials of CRT, QRS duration was used as a measure of dyssynchrony to select patients for treatment2, 3. However, sensitivity5 and specificity6 of QRS duration to predict response to CRT were less than optimal. Subsequently, numerous “time-to-peak” parameters based directly on the motion of the LV walls were developed to diagnose LV mechanical dyssynchrony with echocardiography in an attempt to improve CRT selection criteria7. Echocardiographic mechanical dyssynchrony parameters initially showed promise in predicting response to CRT in single-center studies8–12. However, the multicenter Predictors of Response to CRT (PROSPECT) study recently reported that no echocardiographic dyssynchrony parameter could be recommended to improve patient selection for CRT beyond current guidelines13. In addition, the Resynchronization Therapy in Narrow QRS (RETHINQ) trial recently reported that patients with narrow QRS and evidence of mechanical dyssynchrony do not benefit from CRT14. So where do we go from here? Should selection of patients for CRT based on mechanical dyssynchrony be abandoned in the wake of the negative results from PROSPECT and RETHINQ? We believe that techniques to quantify LV mechanical dyssynchrony need to be refined, not forgotten, and will still play a role in improving CRT selection criteria in the future. This refinement of dyssynchrony quantification requires a paradigm shift. First, time-to-peak methods for quantifying dyssynchrony utilize only a single time point on the velocity or strain curves and should be replaced with more quantitatively sophisticated methods. Utilizing more data reduces variability and increases accuracy. Second, “response to CRT” should no longer be considered synonymous with “presence of left ventricular dyssynchrony”. There is no method based on LV dyssynchrony measures that by itself will predict response to CRT with high accuracy.

Cross-Correlation Delay to Quantify Myocardial Dyssynchrony From Phase Contrast Magnetic Resonance (PCMR) Velocity Data

To apply cross‐correlation delay (XCD) analysis to myocardial phase contrast magnetic resonance (PCMR) tissue velocity data and to compare XCD to three established “time‐to‐peak” dyssynchrony parameters.

Method to create regional mechanical dyssynchrony maps from short-axis cine steady-state free-precession images

To develop a robust method to assess regional mechanical dyssynchrony from cine short‐axis MR images. Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and evidence of left‐ventricular (LV) dyssynchrony. Patient response to CRT is greatest when the LV pacing lead is placed in the most dyssynchronous segment. Existing techniques for assessing regional dyssynchrony require difficult acquisition and/or postprocessing. Our goal was to develop a widely applicable and robust method to assess regional mechanical dyssynchrony.

Quantification of left ventricular internal flow from cardiac magnetic resonance images in patients with dyssynchronous heart failure

To develop a method for quantifying left ventricular (LV) internal flow as a measure of dyssynchrony using standard cine cardiac magnetic resonance (CMR) images.

Method to create regional mechanical dyssynchrony maps from short-axis cine steady-state free-precession images: Mechanical Dyssynchrony Maps From SSFP Images

To develop a robust method to assess regional mechanical dyssynchrony from cine short‐axis MR images. Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and evidence of left‐ventricular (LV) dyssynchrony. Patient response to CRT is greatest when the LV pacing lead is placed in the most dyssynchronous segment. Existing techniques for assessing regional dyssynchrony require difficult acquisition and/or postprocessing. Our goal was to develop a widely applicable and robust method to assess regional mechanical dyssynchrony.

A Method to Create Regional Mechanical Dyssynchrony Maps from Short-Axis Cine SSFP Images

To develop a robust method to assess regional mechanical dyssynchrony from cine short‐axis MR images. Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and evidence of left‐ventricular (LV) dyssynchrony. Patient response to CRT is greatest when the LV pacing lead is placed in the most dyssynchronous segment. Existing techniques for assessing regional dyssynchrony require difficult acquisition and/or postprocessing. Our goal was to develop a widely applicable and robust method to assess regional mechanical dyssynchrony.

A New Method to Diagnose Left Ventricular Dyssynchrony With Analysis of Heart Wall Thickening From Cardiac CT

Left ventricular (LV) dyssynchrony is a pathological condition in which segments of the myocardial wall contract at different times. This dyssynchrony results in a decreased LV ejection fraction (EF) and an increased level of mitral regurgitation. LV dyssynchrony has been linked to higher rates of morbidity, mortality, and arrhythmic susceptibility in patients with congestive heart failure. Cardiac resynchronization therapy (CRT) with biventricular pacemakers has benefited patients with drug-refractory heart failure and signs of ventricular dyssynchrony. Patients are currently selected for CRT therapy if they have a prolonged QRS complex (> 120 msec) on a surface electrocardiogram as well as an EF of less than 35%. However, recent data suggests that these criteria are insufficient, as 30% of patients do not respond to CRT treatments.Copyright