Performance of 3D, navigator echo-gated, contrast-enhanced, magnetic resonance coronary vein imaging in patients undergoing CRT

Cardiac magnetic resonance in patients with cardiac resynchronization therapy: is it time to scan with resynchronization on?

Cardiac resynchronization therapy (CRT) is recommended in international guidelines for patients with heart failure due to important left ventricular systolic dysfunction (or heart failure with reduced ejection fraction) and ventricular conduction tissue disease. Cardiac magnetic resonance (CMR) represents the most powerful imaging tool for dynamic assessment of the volumes and function of cardiac chambers but is rarely utilized in patients with CRT due to limitations on the device, programming and scanning. In this review, we explore the known utility of CMR in this cohort with discussion of the risks and potential benefits of scanning whilst CRT is active, including a practical strategy for conducting high quality scans safely. Our contention is that imaging in patients with CRT could be improved further by keeping resynchronization therapy active with resultant benefits on research and also patient outcomes.

Prediction of mitral regurgitation resolution after coronary bypass graft surgery and cardiac resynchronization therapy by late gadolinium enhancement magnetic resonance imaging: a case report

Background

Appropriate surgical management of moderate functional mitral regurgitation (MR) at the time of coronary artery bypass graft (CABG) surgery remains controversial. A recent study demonstrated no survival benefit from adding mitral repair to CABG for patients with moderate functional MR. Preoperative prediction of reverse remodelling is crucial in making the decision to add mitral valve repair to CABG. Late gadolinium-enhanced magnetic resonance imaging (LGE MRI) offers a reference method to assess myocardial viability.

Case summary

A 60-year-old man with ischaemic cardiomyopathy was admitted to our hospital with exacerbation of heart failure symptoms. Left ventricular (LV) dilatation, severe impairment of LV systolic function, and moderate MR due to tethering were noted on transthoracic echocardiography. The mitral regurgitant jet was central. Intravenous administration of furosemide and human atrial natriuretic peptide was initiated. The patient experienced an episode of ventricular tachycardia, and coronary angiography demonstrated triple-vessel disease. On LGE MRI, subendocardial infarction with a transmural extent of 25–50% was revealed in the inferior, posterior, and lateral walls. Findings from LGE MRI suggested that myocardial viability had been preserved. After performing CABG and cardiac resynchronization therapy, LV volume was substantially decreased and moderate MR was significantly improved without surgical mitral repair. On speckle tracking echocardiography before surgery, a significant difference in the times to peak radial strain between the lateral wall (462 ms) and inferior wall (17 ms) indicated the presence of LV dyssynchrony. Left ventricular dyssynchrony was substantially improved after CABG and cardiac resynchronization therapy defibrillator implantation.

Discussion

In patients with ischaemic cardiomyopathy and moderate functional MR, acquisition of LGE MRI of the LV should be considered to evaluate the viability of LV myocardium. Findings from LGE MRI of the LV can potentially influence the surgical strategy. In patients with preserved viability of LV myocardium, functional MR could be improved after CABG without any surgical repair.

Coronary Sinus Lead Positioning

Although cardiac resynchronization therapy improves morbidity and mortality in patients with cardiomyopathy, heart failure, and electrical dyssynchrony, the rate of nonresponders using standard indications and implant techniques is still high. Optimal coronary sinus lead positioning is important to increase the chance of successful resynchronization. Patient factors such as cause of heart failure, type of dyssynchrony, scar burden, coronary sinus anatomy, and phrenic nerve capture may affect the efficacy of the therapy. Several modalities are under investigation. Alternative left ventricular lead implantation strategies are occasionally required when the transvenous route is not feasible or would result in a suboptimal lead position.

Imaging left-ventricular mechanical activation in heart failure patients using cine DENSE MRI: Validation and implications for cardiac resynchronization therapy

PURPOSE

To image late mechanical activation and identify effective left-ventricular (LV) pacing sites for cardiac resynchronization therapy (CRT). There is variability in defining mechanical activation time, with some studies using the time to peak strain (TPS) and some using the time to the onset of circumferential shortening (TOS). We developed improved methods for imaging mechanical activation and evaluated them in heart failure (HF) patients undergoing CRT.

MATERIALS AND METHODS

We applied active contours to cine displacement encoding with stimulated echoes (DENSE) strain images to detect TOS. Six healthy volunteers underwent magnetic resonance imaging (MRI) at 1.5T, and 50 patients underwent pre-CRT MRI (strain, scar, volumes) and echocardiography, assessment of the electrical activation time (Q-LV) at the LV pacing site, and echocardiography assessment of LV reverse remodeling 6 months after CRT. TPS at the LV pacing site was also measured by DENSE.

RESULTS

The latest TOS was greater in HF patients vs. healthy subjects (112 ± 28 msec vs. 61 ± 7 msec, P < 0.01). The correlation between TOS and Q-LV was strong (r > 0.75; P < 0.001) and better than between TPS and Q-LV (r < 0.62; P ≥ 0.006). Twenty-three of 50 patients had the latest activating segment in a region other than the mid-ventricular lateral wall, the most common site for the CRT LV lead. Using a multivariable model, TOS/QRS was significantly associated with LV reverse remodeling even after adjustment for overall dyssynchrony and scar (P < 0.05), whereas TPS was not (P = 0.49).

CONCLUSION

Late activation by cine DENSE TOS analysis is associated with improved LV reverse remodeling with CRT and deserves further study as a tool to achieve optimal LV lead placement in CRT.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:887-896.

Coronary Sinus Lead Positioning

Although cardiac resynchronization therapy improves morbidity and mortality in patients with cardiomyopathy, heart failure, and electrical dyssynchrony, the rate of nonresponders using standard indications and implant techniques is still high. Optimal coronary sinus lead positioning is important to increase the chance of successful resynchronization. Patient factors such as cause of heart failure, type of dyssynchrony, scar burden, coronary sinus anatomy, and phrenic nerve capture may affect the efficacy of the therapy. Several modalities are under investigation. Alternative left ventricular lead implantation strategies are occasionally required when the transvenous route is not feasible or would result in a suboptimal lead position.