The Role of Cardiovascular Magnetic Resonance in Cardiac Resynchronization Therapy. Card Electrophysiol Clin. 2015;7:619-633. [PMID: 26596807 DOI: 10.1016/j.ccep.2015.08.003]

Mechanical dyssynchrony in patients with heart failure and reduced ejection fraction: how to measure?

PURPOSE OF REVIEW

This article summarizes the most recent imaging techniques to assess left ventricular mechanical dyssynchrony and discusses their value to predict response to cardiac resynchronization therapy (CRT) together with assessment of myocardial scar and cardiac venous anatomy.

RECENT FINDINGS

Left ventricular mechanical dyssynchrony has been associated with prognosis of heart failure patients and has been shown to influence the efficacy of CRT. Although current guidelines do not recommend the assessment of left ventricular mechanical dyssynchrony to select heart failure patients for CRT, technological advances in echocardiography, cardiac magnetic resonance, nuclear imaging and computed tomography have provided powerful tools to characterize left ventricular mechanical dyssynchrony and predict response to CRT. Most important, these imaging techniques permit integration of additional information that is relevant for the efficacy of CRT, such as the extent and location of myocardial scar and the anatomy of the coronary sinus and tributaries where the left ventricular pacing lead may be positioned.

SUMMARY

Left ventricular mechanical dyssynchrony is an important parameter to select heart failure patients who are candidates for CRT. The integration of this parameter together with extent and location of myocardial scar and cardiac venous anatomy is a key to optimize the efficacy of CRT.

Cardiac magnetic resonance imaging: Which information is useful for the arrhythmologist?

Cardiac magnetic resonance (CMR) is a non-invasive, non-ionizing, diagnostic technique that uses magnetic fields, radio waves and field gradients to generate images with high spatial and temporal resolution. After administration of contrast media (e.g., gadolinium chelate), it is also possible to acquire late images, which make possible the identification and quantification of myocardial areas with scar/fibrosis (late gadolinium enhancement, LGE). CMR is currently a useful instrument in clinical cardiovascular practice for the assessment of several pathological conditions, including ischemic and non-ischemic cardiomyopathies and congenital heart disease. In recent years, its field of application has also extended to arrhythmology, both in diagnostic and prognostic evaluation of arrhythmic risk and in therapeutic decision-making. In this review, we discuss the possible useful applications of CMR for the arrhythmologist. It is possible to identify three main fields of application of CMR in this context: (1) arrhythmic and sudden cardiac death risk stratification in different heart diseases; (2) decision-making in cardiac resynchronization therapy device implantation, presence and extent of myocardial fibrosis for left ventricular lead placement and cardiac venous anatomy; and (3) substrate identification for guiding ablation of complex arrhythmias (atrial fibrillation and ventricular tachycardias).