Kitabı oku: «Myocardial torsion»
MYOCARDIAL TORSION
Myocardial Torsion is a book different from others, simply because this book is unique, unusual, and I dare say with admiration, it is a curious book, partly magical, full of personality, for initiatory readers, revealing, provocative, challenging. The book has the infrequent peculiarity of being based, to a great extent, on original personal and multidisciplinary investigations, granting it an important extra value. The authors define their purpose since the first pages of the book: to provide solidity, validity and even more to Torrent Guasp’s concepts.
This is certainly a different book in its structure, content and elaboration. It is a text that the reader may admire or criticize, that may create skepticism or surprise at the new data it proposes, but which undoubtedly will leave nobody indifferent, and that is something few books can achieve.
Prof. Miguel Ángel García Fernández
Department of Medicine,
Universidad Complutense de Madrid, Spain
JORGE C. TRAININI - JORGE LOWENSTEIN - MARIO BERAUDO - ALEJANDRO TRAININI - VICENTE MORA LLABATA - MARIO WERNICKE
MYOCARDIAL TORSION
ANATOMO-FUNCTIONAL INTERPRETATION OF CARDIAC MECHANICS
Contents
Cover page
About Myocardial Torsion
Title page
Epigraph
Prologue
Working Hypothesis
Chapter 1. Functional Anatomy of the Myocardium 1. Preliminary considerations 2. Myocardial architecture 3. Segmentation of the myocardial band 4. Anatomy of the cardiac band. Dissection 5. Interpretation of the origin and end of the muscle band. The cardiac fulcrum 6. Ventricular free walls 7. Ventricular friction and vortex 8. The cardiac apex 9. Phylogenetic aspects of the circulatory system
Chapter 2. Research on the Electrical Propagation of the Heart 1. Historical concepts of myocardial electrical activation 2. Cardiac electrical activation 3. Conclusions
Chapter 3. The Three-Stage Heart. The Suction Pump 1. Chronology of the suction mechanism concept 2. Active suction in the diastolic isovolumic phase 3. Intraventricular pressure and suction mechanism 4. Experimental research on left ventricular suction 5. Electrocardiographic correlation
Chapter 4. Cardiac Mechanics 1. Previous considerations 2. How is diastolic suction produced? 3. Clinical model of left ventricular diastolic restraint in the suction mechanism 4. Systolic residual volume 5. Echocardiography of myocardial torsion 6. Functional aspects of the cardiac muscle band
Synthesis of Myocardial. Torsion Demonstration
References
The Authors
Credits
The heart is a stately city of well-known boundaries with hidden, mysterious and unexplored pathways.
Prologue
Probably only because of my age, I have had the fortune of making the leading prologue for a dozen books, generally of disciples and friends. It has always been an inspiring and personal pleasure rather than an obligation, a diversion in which one tries to give the future readers a global and necessary synoptic view of its virtues. I have to acknowledge that the work of making a prologue for the book of Professor Jorge Trainini et al.: Myocardial Torsion has been different from others, simply because this book is unique, unusual, and I dare say with admiration, it is a curious book, partly magical, full of personality, for initiatory readers, revealing, provocative, challenging, as a book about the knights of the Round Table presenting the reasons and pathways followed searching and perhaps finding the Holy Grail.
The book by Professor Jorge Trainini bonds with one of the most beautiful, romantic and for a long time misunderstood stories of the world of cardiology of the last hundred years: the life and work of Francisco Torrent Guasp (1931-2005), which would deserve in itself a film or better the production of a great opera, as was the life of the master, with its scientific zeals, its sufferings, its incomprehensible pathways, and an end that, unexpected and strangely striking, would be unbelievable in real life, as we would only see it as the exaggeration of the writer, passionate admirer of the hero.
Added to the attraction of a book with these characteristics is the unusual prose of professor Trainini, leader of this work. The book has the infrequent peculiarity of being based, to a great extent, on original personal and multidisciplinary investigations led by Professor Trainini, granting it an important extra value.
The text deals essentially with the anatomy and dynamic function of the heart clarified by the revolutionary anatomical studies of Torrent Guasp who, with his famous dissections, described how the ventricular myocardium was formed by muscle fibers which twisted unto themselves like a rope and flattened laterally as a band, shaped a helix that limited the two ventricular chambers defining their function. All his studies converged in the great outstanding and revolutionary contribution of diastolic suction as an active process due to the contraction of the myocardial band ascending segment.
The authors define their purpose since the first pages of the book: to provide solidity, validity and even more to the master’s concepts. The book attempts to answer a series of questions on cardiac physiology, which emerge when this is approached with the same anatomy of Torrent Guasp, and which are its essence: Do the bands surrounding the ventricles have a point of support similar to most muscles or are they supported by blood itself? How is ventricular torsion produced? Cardiac torsion implies friction mechanisms: is there an organic lubricating source? What is the relationship between ventricular vortex and myocardial torsion mechanisms? How is the mechanically active early diastolic ventricular suction explained? To answer these questions, among others, means fitting together many of the separate pieces that provide even greater strength to Torrents Guasp’s anatomy.
The book is originally organized into four chapters. In chapter 1 the authors write throughout nine sections, one of the most wonderful and original descriptions of myocardial functional anatomy that one could have possibly read. I wish to highlight, because I think it is especially interesting and surprisingly new, the concept of the cardiac fulcrum. The master Torrent Guasp considered that the cardiac band lacked a fixed point of support as the muscles in the musculoskeletal system, and which is the basis for their ability to develop force. The authors describe the structure of the origin and end of the myocardial band, which they call cardiac fulcrum in a parallelism and tribute to the concept of point of support to provide leverage expressed by Archimedes of Syracuse. It is amazing that in the first quarter of the 21st century they show us for the first time the existence of this structure with proper anatomical and histological entity, even more amazing in animal dissections. It is like finding an unknown island not represented in current maps. Only for this, one should be recreated and surprised in reading this book.
In chapter 2 the authors elegantly demonstrate, with 3D mapping electrophysiological studies of cardiac activation in human hearts, the propagation of the electrical stimulus in Torrent Guasp’s myocardial band, surpassing the theoretical ideas of the master.
In chapter 3, they express the theoretical and historical considerations of the cardiac suction pump, with a general vision obtained through the experimental models they developed to confirm the hypothesis.
Finally, in chapter 4 the book ends with a global synthesis of the complex cardiac functional mechanics dominated by the explanation of cardiac suction, the cornerstone of the master´s theory. This section stands out by the beautiful and difficult synthesis of cardiac torsion with myocardial strain echocardiographic techniques, for which the authors show exquisite proficiency.
This is certainly a different book in its structure, content and elaboration. It is a text that the reader may admire or criticize, that may create skepticism or surprise at the new data it proposes, but which undoubtedly will leave nobody indifferent, and that is something few books can achieve… My congratulations.
Madrid, 2019
Prof. Miguel Ángel García Fernández
Professor of Medicine-Cardiac Imaging
School of Medicine, Department of Medicine
Universidad Complutense de Madrid, Spain
Working Hypothesis
The function of the heart corresponds to a mechanical dimension that should be addressed in terms of its structure, which is where we find the origin of the idea that led our research to explain its organic-functional integrity. If we stop in classical descriptions of the heart we realize that anatomical attention was focused on its external and internal surfaces, granting scant importance to the intimate muscle conformation. This was believed to be of a homogeneous solid nature with global uniform contraction, not considering that its mechanical capacity demanded a reinterpretation of its spatial anatomy and motions, leading us into other topics of its functioning that were completely disregarded by cardiology.
The anatomy of the heart was traditionally thought to be formed by spiraling muscle bundles, but these were never described in association with their physiology. Even though R. F. Shaner in 1923 expresses that the “myocardium is characterized by two flattened muscles shaped as a figure of 8. These muscles twist in opposite directions during systole, emptying its content”, it was the Spaniard Torrent Guasp who in 1970 initiated the description and interpretation of the myocardial muscle band, starting point to understand its motions. This was demonstrated in multiple dissections showing that the ventricular myocardium is made up of a group of muscle fibers coiled unto themselves, resembling a rope, flattened laterally as a band, which by giving two spiral twists describes a helix that limits the two ventricles and defines their performance.
An explanation for this muscle homogenization with an intricate anatomical arrangement that hides the myocardial band, implies considering that its structural solidity is required in birds and mammals so that blood is ejected at high speed in a limited time span by an organ that must serve two circulations (systemic and pulmonary). Currently, the myocardial band can be confirmed by the anatomical study of the heart via an adequate dissection, histological examination, magnetic resonance diffusion tensor imaging procedures, echocardiographic analysis and electrophysiological studies with three-dimensional electroanatomical mapping.
Despite all these considerations leading to discern the real internal myocardial anatomy, and contrary to the classical concept, dissection finds a structure with defined planes that allows successive and concatenated physiological motions of narrowing, shortening-twisting, lengthening-untwisting and expansion depending on the propagation of the electrical stimulus along its muscle pathways.
The anatomical evolutionary state of the heart agrees with ventricular mechanics but lacked the understanding of an electrical propagation that could accurately explain the physiology. The studies on this topic aim to show the integrity of an essential cardiac structure-function. The left ventricular endocardial and epicardial electrical activation performed in patients with three-dimensional electroanatomical mapping allowed considering this fundamental topic to analyze it. The circulatory duct of annelids works with a peristaltic mechanism in its contractile progression. The impulse along its length preserves a pattern of axial transmission, but after the cardiac duct twists in birds and mammals, radial transmission of the impulse is added, allowing the helical motion indispensable to produce the successive twisting-shortening motions during systole and untwisting-lengthening in the subsequent suction phase.
This pathway leading from structure to function induced the understanding of topics poorly explained by their mechanical organization, but which should be considered complementary among them and essential for the physiology of the heart.
1 Anatomical and histological investigation of the segmental sequence of the myocardial band.
2 Support and insertion of the myocardial band. The inevitable emerging question is that in order for the bands surrounding the ventricles to twist they should have a supporting point, similarly to a muscle in a rigid insertion. Do they exist in the heart? If this support is real, how does the myocardial muscle band insert in this structure?
3 Myocardial torsion represents the functional solution to eject the ventricular blood content with the necessary energy to supply the whole organism. This situation is implicit in the study of ventricular activation in order to analyze: How is ventricular torsion produced?
4 Muscle friction. The sliding motion between the band segments during ventricular twisting-untwisting assumes that there must be an anti-friction mechanism that avoids the dissipation of the energy used by the heart. Is there a histological explanation for this fact? Do Thebesian and Langer venous conduits play a role in this mechanism? Is there an organic lubricating source?
5 Intraventricular vortex. The development of this vortex studied by echocardiography is the consequence of torsion and the impulse the blood flow needs to eject. The physical theory of dissipative structures currently explains the production of this intraventricular turbulence.
6 Active protodiastolic ventricular suction. A phase of passive ventricular filling would be impossible due to the small difference with peripheral pressure. Ventricular filling was studied as an active phenomenon with energy consumption generated by a myocardial contraction that tends to lengthen the left ventricular base-apex distance after the ejective phase producing a suction effect by an action similar to a “suction cup”. Could this mechanism be explained by the persistent contraction of the ascending segment during the isovolumic diastolic phase?
7 The restitution of sufficient negative pressure in a cardiomyopathy to generate left ventricular suction and adequately draw blood could be achieved with cardiac resynchronization, provided the stimulation is performed in the right region of the myocardial wall.
8 As a result of the last two points: Is it possible to consider in the heart a coupling phase between systole and diastole where cardiac suction takes place?
9 In this three-stage heart (systole, suction, diastole): which is the energy mechanism in the active suction phase?
The methods used in this study to explain the hypothesis of the anatomo-functional integrity of the heart were:
1 Cardiac dissection in bovids and humans.
2 Histological and histochemical analysis of anatomical samples.
3 Left ventricular endocardial and epicardial electrical activation in humans by means of three-dimensinal electroanatomical mapping.
4 The study of left ventricular suction physiology in animals after removal of the right ventricle.
5 Measurement of left intraventricular pressure by ventricular resynchronization.
6 Cardiac function analogy with common medical therapeutic strategies and their reinterpretation (right ventricular bypass surgery, cardiomyoplasty, ventricular restraint techniques, cardiac resynchronization therapy, univentricular mechanical assistance).
7 Echocardiography to corroborate previous studies and the usefulness of these knowledge in clinical practice.
Findings and clinical data presented are the result of experimental tests performed under the approval of all the required regulatory authorities and under the informed consent of all patients following the principles described in the current World Medical Association Declaration of Helsinki (2013). The experiments were carried out according to the 1996 Law of scientific procedures in animals of the United Kingdom and the “National Institutes of Health” guide for the care and use of laboratory animals (NIH Publication No. 8023, updated in 1978).
CHAPTER 1
Functional Anatomy of the Myocardium
1. Preliminary considerations
Classical anatomy of the heart considered that the muscle structure forming the myocardium was homogeneous and compact. Based on this concept, it was described by an external and internal surface limiting a solid, uniform muscle mass. Andreas Vesalius, in his work De Humanis Corporis Fabrica (1543), referred to the difficulty in identifying the layers forming the myocardium. He literally expressed “Whichever way you perform a dissection of the heart meat, either raw or cooked…, you can hardly remove a portion with only one type of fiber, because they have multiple and different directions, mainly transversal”. Three centuries after (1864), J. B. Pettigrew also referred to this situation: “About the complexity of the arrangement I need not say more than Vesalius, Haller and De Blainville, who all confessed their inability to elucidate it”. (81, 114)
This classical structural notion does not explain cardiac mechanics; hence, it is essential to establish its true internal anatomy. Historically, very little importance was attributed to the spatial arrangement of the muscle bundles forming the myocardium. (23) In1970 Francisco Torrent Guasp (102-108) defines the anatomy of the heart adapted to physiological reality. This study approach correlates with a cardiac structure presenting the remarkable characteristic of being adriving-suction pump with the size equivalent to a human fist and an average weight of 270 grams, which ejects 4-6 liters/minute at a speed of 300 cm/s, consuming only 10 watts, and working without interruption for 80 years without maintenance, almost without noise, and no smoke. Its work is equivalent to the daily withdrawal of 1 ton of water 1 m deep with a mechanical efficiency (work/energy relationship) of 50%, not achieved by man-made machines which only attain 30% efficacy. This allows ejecting 70% of the left ventricular volume with only 12% shortening of its contractile unit, the sarcomere.
Torrent Guasp demonstrated through numerous dissections of hearts from different species, including humans, that the ventricular myocardium is formed by an assembly of fibers coiled unto themselves similarly to a rope (rope model) (Figures 1.1 to 1.4) and flattened laterally as a band, which by giving two spiral turns defines a helix limiting both ventricles and setting their performance. (2, 3) This structure is supported by the evolutionary process taking place from the primitive circulatory duct of the annelids to that of mammals, whose arterial circuit forms a loop or fold that twists unto itself giving rise to the ventricular chambers. The primary duct lumen establishes a secondary communication between both adjacent chambers (ventricles) formed by the loop, assuming that the side of the duct where the interconnection takes place must have cleaved all along the duct to achieve this purpose.
Based on these facts, we find that the spatial organization and the rotational motion of the ventricular fibers in their anatomical arrangement, both at the base and apical region levels, find correspondence with the myocardial band. However, after its original description, this anatomy which allows unfolding the heart to form a muscle band has not been considered valid until now by the medical culture.
Figure 1.1. Myocardial band.
Figure 1.2. Origin of myocardial band unfolding.
Figure 1.3. Myocardial band prior to its
complete unfolding (See Figure 1.12).
Figure 1.4. Rope model of the myocardial band. It illustrates the different segments that form the band. In blue: Basal loop. In red: Apical loop.
In view of the criticism or indifference met by the helical myocardial band proposed by Torrent Guasp due to lack of information on the necessary anatomical technique to unfold it, we can currently obtain its confirmation through:
1 Anatomical and histological study of the heart. (128)
2 The evolutionary concept emerging from phylogeny.
3 New imaging procedures obtained with magnetic resonance imaging by diffusion tensor. (17, 24, 82, 142)
4 Echocardiography. (59, 70, 71)
5 Electrophysiological studies performed with three-dimensional electroanatomical mapping. (121-127, 131, 132)
Regarding the argued difficulty to dissect the myocardium, which is more apparent than real (128), we should consider that once the myocardial band originated as a loop in the arterial semicircle of amphibians and reptiles to adapt to the physiological demands of aerial life, the muscle bundles became firmly attached to their contact surfaces, hampering the necessary cleavage planes necessary for their anatomical dissection. The evolutionary goal was to develop a sufficiently solid hemodynamic structure with the strength to generate the suction and pumping of the blood volume that supplied the whole organism. Thus, every attempt to dissect an anatomical segment from the rest of the myocardium, avoiding the real cardiac arrangement, always turns into an obstacle due to the structural plan of the axes where the orientation of the myocardial band courses.
An explanation for this muscular homogeneity hiding the myocardial band, implies considering the required functioning in birds and mammals to achieve blood ejection at a high speed in a limited time span by an organ that must supply two circulations (systemic and pulmonary). Despite these considerations and the classical concept about myocardial anatomy, its dissection finds a structure with defined planes where the successive and related physiological heart motions of narrowing, shortening-twisting, lengthening-untwisting and expansion take place depending on the propagation of the electrical stimulus along its muscle pathways (chapter 1). (125)
The myocardial fibers forming the myocardium cannot be considered as absolutely independent entities within a defined space. Despite the intricacy of fiber bundles with polygonal shape, which in addition receive and give off collateral fibers, a predominant course of central fibers is defined with sliding planes, which together form the myocardial muscle band. It should be recalled that the myocardium constitutes a spiraling continuum in its fibers responding to the helical pattern in its muscle bundles. This arrangement indicates the need of generating a mechanical work that dissipates little energy. Therefore, the fiber layers very gradually shift their orientation, with more or less acute angles, to avoid that abrupt changes in the spatial organization dissipate the necessary work for cardiac function. The fan of fibers that is formed reduces the stress among them.
This situation generates a tangle of fibers that allows the band to behave as a continuous transmission chain with the epicardial fibers taking an oblique direction, the intermediate fibers a transverse course and the endocardial fibers also an oblique direction, but contrary to that of the epicardial plane. The endocardial and epicardial plane access angle is approximately 60 degrees in relation to the transverse fibers. Fiber orientation defines function and thus the ejection fraction is 60% when the normal helical fibers contract and falls to nearly 30% if only the transverse fibers shorten. This occurs when the left ventricle dilates in cardiac remodeling and the fibers miss their oblique orientation, loosing muscular and mechanical efficiency.
It should therefore be acknowledged that a gradual change in orientation is generated from the superficial to the deep fibers that form the different segments of the muscle band. In the progression from the ventricular base to the apex, the number of horizontal fibers decreases in relation to the oblique fibers, showing that the heart is organized as a continuous muscle helix. The ventricular mechanical activity must be heterogeneous during diastole with subendocardial-subepicardial relaxation gradients. During systole, the muscle layers of the myocardial band evidence pronounced and opposite torsion in the subendocardium in relation to the subepicardium, whereas in the apex the subepicardial fiber rotation acquires more relevance.
Beyond this complexity it is necessary to establish the concept of linear and laminar trajectories. Myocardial muscle bundles and bands, which derive from phylogenetic development, essentially shape a master axis of precise dynamic requirement. The spatial muscle structure adopted by the myocardial muscle band has a double function: a) to limit the ventricular chambers and b) to fulfill the suction and driving action in its role of cardiac pump.
