Myocardial Torsion. Jorge C. Trainini
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Название: Myocardial Torsion
Автор: Jorge C. Trainini
Издательство: Bookwire
Жанр: Медицина
isbn: 9789876917971
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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 СКАЧАТЬ