Noninvasive assessment of cardiac mechanics and clinical outcome after partial left ventriculectomy

Surgical ventricular restoration for the treatment of heart failure

Heart failure (HF) is an emerging epidemic affecting 15 million people in the USA and Europe. HF-related mortality was unchanged between 1995 and 2009, despite a decrease in the incidence of cardiovascular disease. Conventional explanations include an aging population and improved treatment of acute myocardial infarction and HF. An adverse relationship between structure and function is the central theme in patients with systolic dysfunction. The normal elliptical ventricular shape becomes spherical in ischemic, valvular, and nonischemic dilated cardiomyopathy. Therapeutic decisions should be made on the basis of ventricular volume rather than ejection fraction. When left ventricular end-systolic volume index exceeds 60 ml/m², medical therapy, CABG surgery, and mitral repair have limited benefit. This form-function relationship can be corrected by surgical ventricular restoration (SVR), which returns the ventricle to a normal volume and shape. Consistent early and late benefits in the treatment of ischemic dilated cardiomyopathy with SVR have been reported in >5,000 patients from various international centers. The prospective, randomized STICH trial did not confirm these findings and the reasons for this discrepancy are examined in detail. Future surgical options for SVR in nonischemic and valvular dilated cardiomyopathy, and its integration with left ventricular assist devices and cell therapy, are described.

Automated motion estimation for 2-D cine DENSE MRI

Cine displacement encoding with stimulated echoes (DENSE) is a magnetic resonance (MR) method that directly encodes tissue displacement into MR phase images. This technique has successfully interrogated many forms of tissue motion, but is most commonly used to evaluate cardiac mechanics. Currently, motion analysis from cine DENSE images requires manually delineated anatomical structures. An automated analysis would improve measurement throughput, simplify data interpretation, and potentially access important physiological information during the MR exam. In this paper, we present the first fully automated solution for the estimation of tissue motion and strain from 2-D cine DENSE data. Results using both simulated and human cardiac cine DENSE data indicate good agreement between the automated algorithm and the standard semi-manual analysis method.

MR assessment of regional myocardial mechanics

Regional myocardial function can be measured by several MR techniques including tissue tagging, phase velocity mapping, and more recently, displacement encoding with stimulated echoes (DENSE) and strain encoding (SENC). Each of these techniques was developed separately and has undergone significant change since its original implementation. As a result, in the current literature, the common features and the differences between the techniques and what they measure are often unclear and confusing. This review article delivers an extensively referenced introductory text which clarifies the current methodology from the starting point of the Bloch equations. By doing this in a consistent way for each method, the similarities and differences between them are highlighted. In addition, their capabilities and limitations are discussed, together with their relative advantages and disadvantages. While the focus is on sequence design and development, the principal parameters measured by each technique are also summarized, together with brief results, with the reader being directed to the extensive literature on data processing and clinical applications for more detail.

Myocardial tagging by cardiovascular magnetic resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging.

Imaging three-dimensional myocardial mechanics using navigator-gated volumetric spiral cine DENSE MRI

A navigator-gated 3D spiral cine displacement encoding with stimulated echoes (DENSE) pulse sequence for imaging 3D myocardial mechanics was developed. In addition, previously described 2D postprocessing algorithms including phase unwrapping, tissue tracking, and strain tensor calculation for the left ventricle (LV) were extended to 3D. These 3D methods were evaluated in five healthy volunteers, using 2D cine DENSE and historical 3D myocardial tagging as reference standards. With an average scan time of 20.5 ± 5.7 min, 3D data sets with a matrix size of 128 × 128 × 22, voxel size of 2.8 × 2.8 × 5.0 mm(3), and temporal resolution of 32 msec were obtained with displacement encoding in three orthogonal directions. Mean values for end-systolic mid-ventricular mid-wall radial, circumferential, and longitudinal strain were 0.33 ± 0.10, -0.17 ± 0.02, and -0.16 ± 0.02, respectively. Transmural strain gradients were detected in the radial and circumferential directions, reflecting high spatial resolution. Good agreement by linear correlation and Bland-Altman analysis was achieved when comparing normal strains measured by 2D and 3D cine DENSE. Also, the 3D strains, twist, and torsion results obtained by 3D cine DENSE were in good agreement with historical values measured by 3D myocardial tagging.

Review of surgical ventricular restoration: A procedure to treat cardiac failure

Severe heart failure refractory to medical treatment necessitates the use of other modalities of treatment. Surgical ventricular restoration (SVR) surgery can provide relief until donour hearts are available or when transplantation is contraindicated. In this review we look at the physiological basis for improvement in cardiac function and cardiac and haemodynamic changes that occur after SVR. We also compile the reported factors affecting surgical outcome, criteria for patient selection and predictors of postoperative mortality. NYHA class, presence of diastolic failure, severe impairment of contractile function and presence of mitral regurgitation were the most important determinants. Various different procedures for achieving SVR are briefly discussed. Importance of mitral valve repair/replacement, coronary artery bypass grafting and intraoperative echocardiography in improving postoperative result is highlighted. Role of perioperative medication (anti-arrhythmics, ACE inhibitors and β-blockers) is briefly studied at the end of the review.

Myocardial tissue tagging with cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional function that provides a detailed and comprehensive examination of intra-myocardial motion and deformation. Given the current advances in gradient technology, image reconstruction techniques, and data analysis algorithms, CMR myocardial tagging has become the reference modality for evaluating multidimensional strain evolution in the human heart. This review presents an in depth discussion on the current clinical applications of CMR myocardial tagging and the increasingly important role of this technique for assessing subclinical myocardial dysfunction in the setting of a wide variety of myocardial disease processes.

Myocardial strain and torsion quantified by cardiovascular magnetic resonance tissue tagging: studies in normal and impaired left ventricular function

Accurate quantification and timing of regional myocardial function allows early identification of dysfunction, and therefore becomes increasingly important for clinical risk assessment, patient management, and evaluation of therapeutic efficacy. For this purpose, the application of tissue Doppler echocardiography has rapidly increased. However, echocardiography has some major inherent limitations. Cardiovascular magnetic resonance imaging with tissue tagging provides highly reproducible data on myocardial function, not only in longitudinal and radial directions, but also in the circumferential direction. Because of the development of faster imaging protocols, improved temporal resolution, less time-consuming postprocessing procedures, and the potential of quantifying myocardial deformation in 3 dimensions at any point in the heart, this technique may serve as an alternative for tissue Doppler echocardiography and is now ready for more widespread clinical use. This review discusses the clinical use of cardiovascular magnetic resonance tissue tagging for quantitative assessment of regional myocardial function, thereby underlining the specific features and emerging role of this technique.

Role of Site Selection for Left Ventriculoplasty to Treat Idiopathic Dilated Cardiomyopathy

Ventriculoplasty was introduced to treat patients with chronic progressive heart failure from end-stage non ischemic dilated cardiomyopathy, which was presumed to be a homogeneous disease. However ventriculoplasty is not commonly used today, because variable results follow using only lateral ventriculoplasty as the treatment tool. This report traces our evolution in surgical management, defines that the homogeneous disease concept is not correct, and centers upon the importance of site selection, appropriate timing, and methods of patient selection. Left ventriculoplasty by either partial left ventriculoplasty (PLV) or septal anterior ventricular exclusion (SAVE or Pacopexy) was performed in 96 high risk (44% NYHA Class III, and 56% Class IV) patients with idiopathic dilated cardiomyopathy over the past 8 years. Overall hospital mortality was 8% in elective operations and 57% in emergency operations. Hemodynamic and functional improvement was evident from ejection fraction rising from 20% to 31%, and improved NYHA Class 3.6 to 1.8. The global series showed 1, 5 and 7 year survival rate was 66.4, 44.7 and 41.3%, respectively. However surgical results improved as experience allowed development of a strategy for timing, and defining proper exclusion site selection. Non homogeneous ventricular disease was identified, and 69% 4 year survival resulted from our intraoperative definition of the most diseased segment (septum or lateral wall), and then exclusion of this site. This evolving experience indicates that left ventriculoplasty is effective treatment for patients with end-stage cardiomyopathy, provided proper patient selection, appropriate timing of the operation, and choice of procedure are used as keys to a successful outcome.

Left ventricular volume reduction

The 'left volume ventricular reduction' operation was originally proposed by Dr Batista to reduce the diameter of the dilated left ventricle by excising a sizable amount of the ventricular free wall. Batista explains that the mechanism of cardiac improvement totally depends on La Place's law, therefore left ventricular wall tension is decreased by reducing the diameter leading to an increase in ejection fraction. Questions, however, still remain on diastolic function, preoperative judgement of left ventricular wall characteristics and late re-dilatation of the left ventricle. The operation was originally performed using normothermic cardiopulmonary bypass on the beating heart. Additional techniques with cardioplegic arrest, concomitant mitral valve repair, and closure of the left ventricle for improvement of hemostasis are shown.