The structure and function of the helical heart and its buttress wrapping. IV. Concepts of dynamic function from the normal macroscopic helical structure

Physiological Changes in QRS Fragmentation in Athletes and Nonathletes without Cardiac Disease

Background/Objectives: QRS fragmentation has not been linked with increased mortality in individuals without known cardiac disease. We aimed to investigate the physiological determinants of QRS fragmentation in individuals without cardiac disease. Methods: Study participants were 163 (54 athletes, 109 nonathletes) asymptomatic individuals with QRS fragmentation but without cardiac disease. QRS fragmentation was assessed in the supine position after deep inspiration or standing up and during exercise. The changes in QRS fragmentation were evaluated over a median follow-up period of 2.3 (0.8-4.9) years. Results: The most common lead with QRS fragmentation was III (63.0% in athletes, 61.5% in nonathletes), immediately followed by V1 (50.0%) and aVF (42.6%) in athletes and aVF (55.0%) in nonathletes. QRS fragmentation in V1 was more frequent in athletes compared to nonathletes (p < 0.001). Among athletes, the presence of QRS fragmentation in V1 could be independently predicted by increased RVOTproxi (right ventricular outflow tract proximal diameter indexed to body surface area) (p < 0.001). Among individuals with QRS fragmentation in V1, deep inspiration resulted in disappearance of QRS fragmentation more frequently in nonathletes compared to athletes (100% vs. 20%, p = 0.003). Deep inspiration resulted in disappearance of QRS fragmentation in aVF (p < 0.001). The presence of QRS fragmentation in II or aVF was associated with increased body mass index (BMI) (p = 0.003). Among athletes without QRS fragmentation in V1 at baseline, the appearance of QRS fragmentation in V1 at the end of follow-up was associated with greater training age (p = 0.034). Among individuals with QRS fragmentation in aVF at baseline, the disappearance of QRS fragmentation in aVF at the end of follow-up was associated with greater reduction in BMI (p = 0.008). Conclusions: The characteristic feature of QRS fragmentation in athletes was the presence of QRS fragmentation in V1, which was associated with RVOTproxi. The persistence of QRS fragmentation in V1 after deep inspiration could serve as a specific marker of exercise-training-related cardiac adaptation. The presence of QRS fragmentation in the leads of the frontal plane was influenced by BMI and respiration phase.

Morphogeometric Evaluation of the Left Ventricle and Left Atrioventricular Ring in Dogs: A Computerized Anatomical Study

In veterinary, there is scarce availability of morphogeometric studies in normal and remodeled hearts; furthermore, ventricular geometry acts as an indicator of cardiac function. It is a highly necessary field of knowledge for the development of therapeutic protocols, especially surgical ones. The objectives of this study were: to obtain measurements of the left atrioventricular valve ring and left ventricle, to analyze the proportionality between the segments of the left cardiac chamber of normal hearts and to describe reference values for morphogeometric analysis of the left ventricle. For this, 50 hearts from small (Group 1-G1) and medium to large (Group 2-G2) dogs were laminated in the apical, basal and equatorial segments, and submitted to computer analysis to identify the perimeter of each segment and the left atrioventricular ring, wall thickness and distance from the atrioventricular sulcus to the apex. The largest internal perimeter was that of the equatorial. The basal segment had the highest mean for ventral parietal wall thickness, suggesting greater contractile reserve at that location. Considering the proportionality relationships, there was no statistical difference between the intersegmental perimeter indices for the two groups. This suggests that despite the animals' weight variations, the proportions between the left ventricular segments are maintained. Therefore, it is concluded that the data can be used as a standard of comparison for cardiac geometric assessments, as well as a basis for the development of therapeutic measures in the context of adverse cardiac remodeling.

The surgical technique of the convergent procedure

The convergent procedure is a newly developed hybrid ablation procedure that involves extensive epicardial ablation of the posterior left atrial wall followed by endocardial mapping and addition of pulmonary vein isolation. It is a team-based approach that provides a promising option for patients with persistent and permanent atrial fibrillation. In this manuscript, we present a detailed description of the surgical component of this procedure and include potential pitfalls based on our experience in performing it.

Effect of pericardial incision on left ventricular morphology and systolic function in patients during coronary artery bypass grafting

Background

Accurate assessment of left ventricular (LV) systolic function is important after coronary artery bypass grafting (CABG). LV ejection fraction (LVEF) is conventionally used to evaluate LV systolic function; deformation parameters can be used to detect subtle LV systolic dysfunction. It is unclear whether an incised pericardium without sutures during CABG could affect LV morphology and function. We investigated the effect of pericardial incision on LV morphology and systolic function during CABG.

Methods

Intraoperative transesophageal echocardiography was performed in 27 patients during elective off-pump beating heart CABG 5 min before and after pericardial incision. LV longitudinal and mid-cavity transversal diameters, sphericity index, volumes, and LVEF were measured. LV global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and twist obtained by two-dimensional speckle tracking echocardiography were measured simultaneously.

Results

LV mid-cavity transversal diameter increased, while the LV sphericity index decreased (P < 0.001) immediately after pericardial incision. The GLS, GCS, and twist significantly decreased, while the GRS notably increased (P < 0.001). The LV volumes and LVEF remained unchanged.

Conclusions

Pericardial incision immediately transformed LV morphology from an ellipsoid to sphere, with decreased longitudinal and circumferential strain and twist, and increased radial strain, while LVEF remained unchanged. This should be considered when evaluating LV systolic function in patients after CABG.

The Pacopexy procedure for left ventricular aneurysm: a 10-year clinical experience

PURPOSE

To evaluate our 10-year clinical experience of performing the Pacopexy procedure for left ventricular aneurysm (LVA).

METHODS

Between January, 1998 and November, 2015, a cohort of 92 patients with LVA underwent surgery to reshape the left ventricle. Fifty-seven patients underwent the Dor procedure and 35 underwent the Pacopexy procedure to emphasize the conical shape, whereby patch placement followed an oblique trajectory between the left ventricular apex and the septum below the aortic valve.

RESULTS

The early-mortality rate was 4.34% (4/92; n = 2 in each group). The 10-year survival rate was 70.4 ± 7.9% in the Pacopexy group vs 41.7 ± 7.2% in the Dor group (p < 0.05), and the rate of freedom from hospital re-admission for heart failure (HF) or cardiac death was 60.0 ± 8.6% vs 28.8 ± 6.8%, respectively (p < 0.05). The Dor procedure and left ventricular end systolic volume index (LVESVI) ≥ 60 ml/m2 were strongly and significantly associated with long-term mortality and hospital re-admission for HF.

CONCLUSIONS

The Pacopexy procedure is a reproducible surgical option for the treatment of LVA. The improved configuration achieved by the Pacopexy procedure has resulted in good long-term survival and a high degree of freedom from re-admission for HF in patients with advanced LVA.

Repair versus replacement of mitral valves in cases of severe rheumatic mitral stenosis: mid-term clinical outcomes

Background

We compared and analyzed differences between repair vs. replacement of mitral valves on severe rheumatic mitral stenosis by looking at mid-term clinical outcomes.

Methods

Patients with severe rheumatic mitral stenosis (mitral valve area ≤1.5 cm², with or without mitral valve regurgitation) from January 2011 to September 2017 were divided into two groups: a mitral valve repair group (MVP) and a mitral valve replacement group (MVR). After propensity score matching between the two groups, we compared changes in post-operation clinical outcomes. We also monitored changes in left ventricular longitudinal and circumferential strain in successfully matched patients (20 pairs) by echocardiography speckle tracing.

Results

A total of 921 patients were recruited (221 in MVP and 700 in MVR). After a propensity score matching, 216 cases were selected with 108 patients in each group. With a follow-up period of 3 months to 7.1 years, the incidence of heart failure was observed to be significantly higher in the MVR group than in the MVP group (P<0.05). Echocardiographic speckle tracking imaging analysis showed that left ventricular longitudinal strain decreased in the MVR group, suggesting that a change of cardiac structure may affect the cardiac function.

Conclusions

Selecting suitable patients for mitral valve repair is feasible even for patients with severe rheumatic mitral stenosis. In our study, compared with prosthetic valve replacement in these patients, valve repair still significantly reduced the valve-related complications rates and improved the quality of life during the follow-up.

The Memory of the Heart

The embryological development of the heart is one of the most fascinating phenomena in nature and so is its final structure and function. The various ontogenetic passages form the evolutive basis of the final configuration of the heart. Each key step can be recognized in the final features, as the heart maintains a kind of “memory” of these passages. We can identify the major lines of development of the heart and trace these lines up to the mature organ. The aim of this review is to identify these key parameters of cardiac structure and function as essential elements of the heart’s proper functioning and bases for its treatment. We aim to track key steps of heart development to identify what it “remembers” and maintains in its final form as positively selected. A new vision based on the whole acquired knowledge must guide an in-depth scientific approach in future papers and guidelines on the topic and a complete, farsighted therapeutic conduct able to ensure the physiological correction of cardiac pathologies. The application of this modern, functional vision of the heart could improve the clinical treatment of heart disease, filling the gaps still present.

Human gingival fibroblast feeder cells promote maturation of induced pluripotent stem cells into cardiomyocytes

The use of human induced pluripotent stem (iPS) cells has been investigated in multiple regenerative medicine studies. However, although methods for efficient differentiation of iPS cells into heart tissues have been devised, it remains difficult to obtain cardiac tissue with high contractility. Herein, we established a method for differentiating iPS cells into highly contractile cardiomyocytes (CMs), and demonstrate that the use of human gingival fibroblasts (HGFs) as a feeder cells promotes maturation of iPS-derived CMs (iPS-CMs) in vitro. After CM differentiation of iPS cells, iPS-CMs showed increased mRNA expression of the CM specific maker cardiac troponin T (cTnT) in the absence and presence (on-feeder condition) of cocultured HGFs, and decreased expression of pluripotent markers was observed under both conditions. Protein expression of cTnT was also observed in immunocytochemical analyses, although on-feeder CMs showed comparatively robust sarcomere structure and significantly stronger contractility than feederless cardiomyocytes, suggesting that HGF feeder cells facilitate CM differentiation of iPS cells.

The Heart as a Psychoneuroendocrine and Immunoregulatory Organ

The heart can be viewed not just as muscle pump but also as an important checkpoint for a complex network of nervous, endocrine, and immune signals. The heart is able to process neurological signals independently from the brain and to crosstalk with the endocrine and immune systems. The heart communicates with the psyche through the neuro-endocrine-immune system in a highly integrated way, in order to maintain the homeostasis of the whole body with peculiarities specific to males and females.

Detecting impaired myocardial relaxation in sepsis with a novel tissue Doppler parameter (septal e'/s')

Background

Left ventricular diastolic dysfunction is associated with mortality outcomes in severe sepsis and septic shock. There are ongoing issues with diagnosing diastolic dysfunction in this cohort, partly owing to the poor applicability of traditional parameters in the hyperdynamic circulation. In this feasibility study, we sought to assess the utility of a novel parameter (septal e′/s′) to identify diastolic dysfunction in patients with severe sepsis and septic shock who had normal systolic function against the 2016 American Society Echocardiography and European Association of Cardiovascular Imaging (ASE/EACI) guidelines on diastolic dysfunction.

Methods

In this prospective observational pilot study, patients identified as having severe sepsis and septic shock underwent transthoracic echocardiography on day 1 and day 3 of their intensive care unit admission. In patients with normal systolic function, septal e′/s′ was calculated using the peak modal velocity of the s′ compared with the e′ from the septal annulus tissue Doppler imaging and compared with their diastolic grade according to the 2016 ASE/EACI guidelines on diastolic dysfunction.

Results

On day 1 of admission, 44 of 62 patients with severe sepsis and septic shock had normal systolic function. There was a strong association of those with diastolic dysfunction having a reduced septal e′/s′ compared with patients with normal diastolic function (AUC 0.91). A similar relationship was seen with patients who had indeterminate diastolic dysfunction. On day 3, 37 patients had normal systolic function. Again, there was a strong association of those with diastolic dysfunction and a reduced septal e′/s′ (AUC 0.95).

Conclusions

A reduction in septal e′/s′ may indicate diastolic dysfunction in patients with severe sepsis and septic shock who have normal systolic function. As opposed to limited traditional measures of diastolic dysfunction, it is applicable in those with hyperdynamic systolic function.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1727-9) contains supplementary material, which is available to authorized users.

Strain Imaging Echocardiography: What Imaging Cardiologists Should Know

Despite recent advances in clinical imaging, echocardiography remains as the most accessi-ble and reliable noninvasive. Since knowledge of left ventricular systolic function remains so critically important in determining prognosis; every effort should be made to prevent subjective estimations. The advent of strain imaging echocardiography now offers a readily available and portable imaging tool that not only offers an objective characterization of myocardial dynamics; but also allows for early detection of subclinical left ventricular dysfunction. This review outlines the basic concepts of strain imaging to better understand the mechanism of myocardial function as well their applicability in the least common cardiac diagnosis among current clinical practice.

Assessment of the rotation motion at the papillary muscle short-axis plane with normal subjects by two-dimensional speckle tracking imaging: a basic clinical study

Background

The aim of this study was to observe the rotation patterns at the papillary muscle plane in the Left Ventricle(LV) with normal subjects using two-dimensional speckle tracking imaging(2D-STI).

Methods

We acquired standard of the basal, the papillary muscle and the apical short-axis images of the LV in 64 subjects to estimate the LV rotation motion by 2D-STI. The rotational degrees at the papillary muscle short-axis plane were measured at 15 different time points in the analysis of two heart cycles.

Results

There were counterclockwise rotation, clockwise rotation, and counterclockwise to clockwise rotation at the papillary muscle plane in the LV with normal subjects, respectively. The ROC analysis of the rotational degrees was performed at the papillary muscle short-axis plane at the peak LV torsion for predicting whether the turnaround point of twist to untwist motion pattern was located at the papillary muscle level. Sensitivity and specificity were 97% and 67%, respectively, with a cut-off value of 0.34°, and an area under the ROC curve of 0.8. At the peak LV torsion, there was no correlation between the rotational degrees at the papillary muscle short-axis plane and the LVEF in the normal subjects(r = 0.000, p = 0.998).

Conclusions

In the study, we conclude that there were three rotation patterns at the papillary muscle short-axis levels, and the transition from basal clockwise rotation to apical counterclockwise rotation is located at the papillary muscle level.

Computational modeling of electromechanical propagation in the helical ventricular anatomy of the heart

The classical interpretation of myocardial activation assumes that the myocardium is homogeneous and that the electrical propagation is radial. However, anatomical studies have described a layered anatomical structure resulting from a continuous anatomical helical disposition of the myocardial fibers. To further investigate the sequence of electromechanical propagation based on the helical architecture of the heart, a simplified computational model was designed. This model was then used to test four activation patterns, which were generated by propagating the action potential along the myocardial band from different activation sites.

Models of ventricular structure and function reviewed for clinical cardiologists

The architectural arrangement of cardiomyocytes aggregated together within the ventricular walls remains controversial. Two models currently attract clinical attention, with neither model standing rigorous anatomical scrutiny. The first is based on the notion that ventricular mass can be unraveled consistently to produce a unique myocardial band. The second model was initially based on the notion that cardiomyocytes were bundled together in uniform fashion, with fibrous shelves interposed in transmural fashion. This concept was subsequently modified to accept the fact that the fibrous matrix supporting the cardiomyocytes within the ventricular walls does not form transmural sheets. Current observations demonstrate that not all cardiomyocytes are aggregated together in tangential fashion. A significant netting component is aligned in obliquely intruding and transversal fashion. The interaction between the tangential and transversal chains of cardiomyocytes with the fibrous matrix produces antagonistic forces, with both unloading and auxotonic forces necessary to explain normal and abnormal cardiodynamics. This article is part of a JCTR special issue on Cardiac Anatomy.

Optimizing electrode placement for hemodynamic benefit in cardiac resynchronization therapy

BACKGROUND

Research is needed to explore the relative benefits of alternative electrode placements in biventricular and left ventricular (LV) pacing for heart failure with left bundle branch block (LBBB).

METHODS

A fast computational model of the left ventricle, running on an ordinary laptop computer, was created to simulate the spread of electrical activation over the myocardial surface, together with the resulting electrocardiogram, segmental wall motion, stroke volume, and ejection fraction in the presence of varying degrees of mitral regurgitation. Arbitrary zones of scar and blocked electrical conduction could be modeled.

RESULTS

Simulations showed there are both sweet spots and poor spots for LV electrode placement, sometimes separated by only a few centimeters. In heart failure with LBBB, pacing at poor spots can produce little benefit or even reduce pumping effectiveness. Pacing at sweet spots can produce up to 35% improvement in ejection fraction. Relatively larger benefit occurs in dilated hearts, in keeping with the greater disparity between early and late activated muscle. Sweet spots are typically located on the basal to midlevel, inferolateral wall. Poor spots are located on or near the interventricular septum. Anteroapical scar with conduction block causes little shift in locations for optimal pacing. Hearts with increased passive ventricular compliance and absence of preejection mitral regurgitation exhibit greater therapeutic gain. The durations and wave shapes of QRS complexes in the electrocardiogram can help predict optimum electrode placement in real time.

CONCLUSIONS

Differences between poor responders and hyperresponders to cardiac resynchronization therapy can be understood in terms of basic anatomy, physiology, and pathophysiology. Computational modeling suggests general strategies for optimal electrode placement. In a given patient heart size, regional pathology and regional dynamics allow individual pretreatment planning to target optimal electrode placement.

Maze Procedures for Atrial Fibrillation, From History to Practice

Atrial fibrillation may result in significant symptoms, (systemic) thrombo-embolism, as well as tachycardia-induced cardiomyopathy with cardiac failure, and consequently be associated with significant morbidity and mortality. Nowadays symptomatic atrial fibrillation can be treated with catheter-based ablation, surgical ablation or hybrid approaches. In this setting a fairly large number of surgical approaches and procedures are described and being practised. It should be clear that the Cox-maze procedure resulted from building up evidence and experience in different steps, while some of the present surgical approaches and techniques are being based only on technical feasibility with limited experience, rather than on a process of consequent methodology. Some of the issues still under debate are whether or not the maze procedure can be limited to the left atrium or even to isolation of the pulmonary veins or that bi-atrial procedures are indicated, whether or not cardiopulmonary bypass is to be applied and which route of exposure facilitates an optimal result. In addition, maze procedures are not procedures guide by electrophysiological mapping. At least in theory not in all patients all lesions of the maze procedures are necessary. A history and aspects of current practise in surgical treatment of atrial fibrillation is presented.

Assessment of left ventricular relaxation by untwisting rate based on different algorithms

BACKGROUND

This study was performed in both animals and human subjects to test whether different approaches to calculate untwisting rate may lead to different results in the assessment of left ventricular (LV) relaxation.

METHODS

In animal experiments, congestive heart failure was successfully induced in 8 adult dogs. Transthoracic echocardiography was performed with simultaneous LV pressure recording at baseline and the stage of heart failure. In the clinical study, 72 patients undergoing right-sided heart catheterization were studied by transthoracic echocardiography. LV twist was calculated as the difference between apical and basal rotations measured using two-dimensional speckle tracking. Untwisting rate was calculated using 3 different algorithms as the peak negative time derivative of twist (UR(max)) during early diastole, the slope of the linear regression of untwisting over time (UR(slope)), or the average untwisting over the isovolumic relaxation period (UR(mean)).

RESULTS

UR(max) significantly correlated with tau and -dP/dt in dogs (r=-0.81 and 0.77, respectively, both P < .001) and was reduced at the stage of heart failure (P < .01). In 55 patients (76%) with adequate image quality, only UR(max) among untwisting rates calculated by 3 different algorithms was significantly related to tau (r=-0.51, P < .001). UR(max) was significantly lower in patients with tau>/=48 ms than in patients with tau<48 ms (P=.004), most of whom had a depressed LV ejection fraction.

CONCLUSION

UR(max) best reflects LV relaxation in comparison with the 2 other algorithms.

Models versus established knowledge in describing the functional morphology of the ventricular myocardium

The myocytes comprising the ventricular mass are arranged so as to function in antagonistic fashion, the walls having the capacity to generate both constrictive and dilatory forces. This dualistic activity is organized on the basis of a site-specific morphologic pattern, permitting marked regional specificity for mural motion and providing a target for regional therapy. Diseased regions can be removed surgically without danger of jeopardizing the remaining healthy mural segments. The sensitivity of the intruding population of myocytes to positive and negative inotropic medication is markedly more pronounced than that of the prevailing tangentially aligned myocytes. This asymmetrical action of inotropes in the setting of global ventricular imbalance promotes the potential to restore constrictive as opposed to dilatory actions.

Decreased left ventricular torsion and untwisting in children with dilated cardiomyopathy

The purpose of this study was to analyze left ventricular (LV) torsion and untwisting, and to evaluate the correlation between torsion and other components of LV contraction in children with dilated cardiomyopathy (DCM). Segmental and global rotation, rotational rate (Vrot) were measured at three levels of LV using the two dimensional (2D) speckle tracking imaging (STI) method in 10 DCM patients (range 0.6-15 yr, median 6.5 yr, 3 females) and 17 age- and sex-matched normal controls. Global torsion was decreased in DCM (peak global torsion; 10.9 +/- 4.6 degrees vs. 0.3 +/- 2.1 degrees , p<0.001). Loss of LV torsion occurred mainly by the diminution of counterclockwise apical rotation and was augmented by somewhat less reduction in clockwise basal rotation. In DCM, the normal counterclockwise apical rotation was not observed, and the apical rotation about the central axis was clockwise or slightly counterclockwise (peak apical rotation; 5.9 +/- 4.1 degrees vs. -0.9 +/- 3.1 degrees , p<0.001). Systolic counterclockwise Vrot and early diastolic clockwise Vrot at the apical level were decreased or abolished. In DCM, decreased systolic torsion and loss of early diastolic recoil contribute to LV systolic and diastolic dysfunction. The STI method may facilitate the serial evaluation of the LV torsional behavior in clinical settings and give new biomechanical concepts for better management of patients with DCM.

The contribution of left ventricular muscle bands to left ventricular rotation: assessment by a 2-dimensional speckle tracking method

BACKGROUND

Torsion is an essential component of left ventricular (LV) function. Systolic rotation, as a component of torsion, winds the heart muscle up like a spring, setting up recoil for early diastole. We used a new 2-dimensional speckle tracking strain method to study differences in twisting in subendocardial and subepicardial layers of the LV in open-chest pigs. Our aim was to identify the relative contributions of the inner or outer layers of the LV wall to rotation and, hence, systole.

METHODS

A total of 23 juvenile pigs were imaged in the short axis, epicardially, to obtain images at a level just below the papillary muscles with high-frequency (14 MHz) ultrasound. Speckle tracking software using scanline files was used to measure the torsional contribution of septum, anterior, posterior, and inferior LV wall segments. Two zones on the septum were evaluated separately: one with apparent circumferential fiber orientation in the inner layer and one with a speckle pattern suggesting longitudinal fiber orientation on the right ventricular aspect of the septum. Pressure rate changes (dP/dt) during the cardiac cycle were measured as an index of LV function and correlated with the regional torsion.

RESULTS

Mean peak rotations measured by speckle tracking echocardiography at the apex showed counterclockwise rotation of LV septal wall (10.68 +/- 2.67 degrees for the inner layer and 8.27 +/- 1.73 degrees for the outer layer). The time difference for time to peak rotation was 213.22 +/- 77.95 and 241.17 +/- 54.67 milliseconds for inner and outer layers, respectively. Significant differences were shown between the inner and outer layer of the LV for both rotation (P = .000) and timing of rotation (P = .02). The dP/dt measurements correlated well with the inner rotation magnitude of the LV and with the difference of short-axis rotation between inner and outer layers of the LV wall.

CONCLUSIONS

Inner and outer layers of the LV wall, especially at the septum, have different rotational behaviors. When used with very high-resolution imaging, this method could contribute to the understanding of functional contributions of the LV wall and their relative contribution to cardiac segmental twisting.

How are the myocytes aggregated so as to make up the ventricular mass?

Of late, it has become fashionable in the surgical literature to describe the ventricular mass as though arranged in the form of a continuous myocardial band, which starts at the aorta and ends at the pulmonary trunk. On the basis of this concept, its supporters have produced revisionist accounts of cardiac development and ventricular function, as well as using it as the basis for proposed surgical maneuvers. They seem unaware, however, that the original concept itself has never been supported by independent anatomic studies, while, to the best of our knowledge, they have not themselves performed anatomic investigations to prove its substance. Furthermore, the current proponents of the "unique myocardial band" ignore a large body of previous anatomic study which showed that the ventricular mass is arranged in the form of a modified blood vessel, with each myocyte anchored to its neighbor within a 3-dimensional myocardial mesh, rather than being arranged in a fashion analogous to skeletal muscles, with discrete origins and insertions of myocardial bands or tracts. In this review, we summarize the evidence showing that there are no anatomic structures within the ventricular myocardium that permit it to be unraveled in systematic fashion so as to produce the purported myocardial band. We also re-visit our own previous investigations, which supported the conventional approach, namely that the myocytes are aggregated together within a supporting fibrous matrix in the form of a 3-dimensional meshwork.

Mitral valve repair: critical analysis of the anatomy discussed

In this brief review, we discuss the anatomy of the mitral valve pertinent to surgical repair. First, we emphasise the need for diagnosticians to describe the valve in the context of the position of the heart within the body, following the standard rules of anatomy, and using attitudinally appropriate descriptions. It has become customary to describe cardiac structures as if the heart is positioned on its apex. This cannot be good in the current era, when the tomographic techniques increasingly used for diagnosis demonstrate the heart as seen in the body. We then discuss the overall valvar structure in terms of a complex made up of the annulus, the leaflets, their tendinous cords, and the supporting papillary muscles. After providing accounts of the salient structure of each part of the complex, we discuss potentially divisive issues, such as the number of leaflets, and the categorisation of the tendinous cords. We explain how most of the disagreements stem not from differences in observation, but rather from differences in definitions. We suggest that these can largely be dissipated if the valve is analysed in its closed, rather than its open, position. When seen in the closed position, it becomes obvious that the key feature is the solitary zone of apposition between the major components of the skirt of leaflet tissue, this being the major functional part of the valvar complex. Finally, we discuss the relationships of the valvar complex to the other cardiac structures, concentrating on the other cardiac valves, the conduction tissues, and the coronary arteries and veins.

The embryonic vertebrate heart tube is a dynamic suction pump

The embryonic vertebrate heart begins pumping blood long before the development of discernable chambers and valves. At these early stages, the heart tube has been described as a peristaltic pump. Recent advances in confocal laser scanning microscopy and four-dimensional visualization have warranted another look at early cardiac structure and function. We examined the movement of cells in the embryonic zebrafish heart tube and the flow of blood through the heart and obtained results that contradict peristalsis as a pumping mechanism in the embryonic heart. We propose a more likely explanation of early cardiac dynamics in which the pumping action results from suction due to elastic wave propagation in the heart tube.

Heuristic problems in defining the three-dimensional arrangement of the ventricular myocytes

There is lack of consensus concerning the three-dimensional arrangement of the myocytes within the ventricular muscle masses. Bioengineers are seeking to model the structure of the heart. Although the success of such models depends on the accuracy of the anatomic evidence, most of them have been based on concepts that are far from anatomical reality, which ignore many significant previous accounts of anatomy presented over the past 400 years. During the 19th century, Pettigrew emphasized that the heart was built on the basis of a modified blood vessel rather than in the form of skeletal muscles. This fact was reemphasized by Lev and Simkins as well as Grant in the 20th century, but the caveats listed by these authors have been ignored by proponents of two current concepts, which state either that the myocardium is arranged in the form of a "unique myocardial band," or that the walls of the ventricles are sequestrated in uniform fashion by laminar sheets of fibrous tissue extending from epicardium to endocardium. These two concepts are themselves incompatible and are further at variance with the majority of anatomic studies, which have emphasized the regional heterogeneity to be found in the three-dimensional packing of the myocytes within a supporting matrix of fibrous tissue. We reemphasize the significance of this three-dimensional muscular mesh, showing how the presence of intruding aggregates of myocytes extending in oblique transmural fashion also contends against the notion that all myocytes are orientated with their long axes parallel to the epicardial and enodcardial surfaces.

Real-time fusion of endoscopic views with dynamic 3-D cardiac images: a phantom study

Minimally invasive robotically assisted cardiac surgical systems currently do not routinely employ 3-D image guidance. However, preoperative magnetic resonance and computed tomography (CT) images have the potential to be used in this role, if appropriately registered with the patient anatomy and animated synchronously with the motion of the actual heart. This paper discusses the fusion of optical images of a beating heart phantom obtained from an optically tracked endoscope, with volumetric images of the phantom created from a dynamic CT dataset. High quality preoperative dynamic CT images are created by first extracting the motion parameters of the heart from the series of temporal frames, and then applying this information to animate a high-quality heart image acquired at end systole. Temporal synchronization of the endoscopic and CT model is achieved by selecting the appropriate CT image from the dynamic set, based on an electrocardiographic trigger signal. The spatial error between the optical and virtual images is 1.4 +/- 1.1 mm, while the time discrepancy is typically 50-100 ms. Index Terms-Image guidance, image warping, minimally invasive cardiac surgery, virtual endoscopy, virtual reality.

Cardiac torsion and electromagnetic fields: The cardiac bioinformation hypothesis

Although in physiology the heart is often referred to as a simple piston pump, there are in fact two additional features that are integral to cardiac physiology and function. First, the heart as it contracts in systole, also rotates and produces torsion due to the structure of the myocardium. Second, the heart produces a significant electromagnetic field with each contraction due to the coordinated depolarization of myocytes producing a current flow. Unlike the electrocardiogram, the magnetic field is not limited to volume conduction and extends outside the body. The therapeutic potential for interaction of this cardioelectromagnetic field both within and outside the body is largely unexplored. It is our hypothesis that the heart functions as a generator of bioinformation that is central to normative functioning of body. The source of this bioinformation is based on: (1) vortex blood flow in the left ventricle; (2) a cardiac electromagnetic field and both; (3) heart sounds; and (4) pulse pressure which produce frequency and amplitude information. Thus, there is a multidimensional role for the heart in physiology and biopsychosocial dynamics. Recognition of these cardiac properties may result in significant implications for new therapies for cardiovascular disease based on increasing cardiac energy efficiency (coherence) and bioinformation from the cardioelectromagnetic field. Research studies to test this hypothesis are suggested.

The surgical treatment of heart failure. A new frontier: nontransplant surgical alternatives in heart failure

Heart failure may affect 500,000 new people each year. Heart transplantation has leveled off at approximately 2,500-3,000 cases per year in the United States. Thus, new nontransplant surgical alternatives may be necessary to treat many of the patients who progress to intractable Class III, or especially Class IV heart failure. In addition to left ventricular assist devices, other operations have been used and are now being developed for this purpose. These include left ventricular resection (Batista operation), mitral valve repair, autologous skeletal muscle cardiac assist, splint and compression devices, as well as left ventricular reconstruction by the Dor procedure. All of these procedures have been, and are currently being, evaluated for the surgical treatment of congestive heart failure and they will be reviewed in this article. Although many appear very promising, ongoing trials and retrospective reviews will be increasingly necessary to vigorously define which of the nontransplant surgical alternatives are the best procedures going forward for the large numbers of patients with congestive failure.

The structure and function of the helical heart and its buttress wrapping. V. Anatomic and physiologic considerations in the healthy and failing heart

A macroscopic structure of an elliptic heart, formed by the helix provided by the apical loop, is defined and related, initially, to normal function. To define the sequence of normal progressive muscular activity, cardiac pressure, magnetic resonance imaging (MRI), and multiple gated acquisition (MUGA) records are reviewed. This novel format of structure for the helical heart is then compared with historic studies of ventricular structure. New concepts will show how the basal loops cause initial isovolumetric contraction, together with factors responsible for contractile ventricular lengthening responsible for filling by suction. The interaction of these muscular-functional changes are correlated to basic studies of electrophysiology (excitation-contraction) to set the stage for alterations produced by changing the helical apex to a sphere during congestive heart failure. Macroscopic changes in heart failure, which convert the ellipse to a globe, are defined as the underpinning of dilated cardiomyopathy. It is our hypothesis that the commonality of this spheric left ventricular substrate becomes responsible for ischemic, idiopathic, and dilated ventricular cardiomyopathy.