Experimental study of the so called left ventricular isovolumic relaxation phase.

INTRODUCTION AND OBJECTIVES: Left ventricular filling begins in the ventricular isovolumic relaxation phase. According to the Torrent-Guasp myocardial band theory, this phase results from the contraction of the final portion of the myocardial band: the ascending segment of the apical loop. The objectives were to study the myocardial mechanisms influencing transmitral flow during early diastole and to determine whether the rapid ventricular filling phase involves contraction or relaxation. METHODS: An experimental in vivo pig model was used. Regional contractility in three segments of the myocardial band was assessed using piezoelectric crystals and mitral flow was measured by echo-Doppler ultrasonography at baseline and after akinesia had been induced in the ascending segment by 2.5% formaldehyde infusion. Changes in intracavitary pressure in the left ventricle and left atrium and flow alterations in the aortic root were recorded. The start of the isovolumic relaxation phase was identified using the time at which the ejection of blood ceases, as indicated by aortic flow measurements. RESULTS: During the left ventricular isovolumetric relaxation phase, the ascending segment of the apical loop was undergoing contraction. The infusion of formaldehyde into this segment affected the extent to which the intraventricular pressure could decrease, prolonged the isovolumic relaxation phase and resulted in a lower minimum pressure. It also produced a significant decrease in transmitral flow velocity in early diastole and an increase at end-diastole. CONCLUSIONS: The rapid ventricular filling phase is characterized by contraction.

Estudio experimental de la llamada fase de relajación isovolumétrica del ventrículo izquierdo / Experimental study of the so called left ventricular isovolumic relaxation phase

Introducción y objetivos. El llenado del ventrículo izquierdo se inicia con la fase de relajación isovolumétrica ventricular. En la teoría de la banda miocárdica de Torrent-Guasp, esta fase se produce como consecuencia de la contracción de la porción final de la banda muscular, el segmento ascendente de la lazada apexiana. El objetivo es estudiar los mecanismos miocárdicos involucrados en el flujo transmitral durante la protodiástole y discernir si la fase de llenado rápido ventricular es un proceso de relajación o de contracción. Métodos. Modelo experimental in vivo en cerdos. Se estudia la contractilidad regional con cristales piezoeléctricos en tres segmentos de la banda miocárdica y el flujo transmitral con eco-Doppler, en situación basal y tras la producción de acinesia del segmento ascendente mediante la infiltración con formaldehído al 2,5%. Se registran las curvas de presión intracavitarias del ventrículo izquierdo y la aurícula izquierda y el flujo en la raíz aórtica. Para determinar el inicio de la fase de relajación isovolumétrica, hemos identificado el final de la expulsión de sangre en la curva del flujo aórtico. Resultados. Durante la fase de relajación isovolumétrica del ventrículo izquierdo, el segmento ascendente de la lazada apexiana está contrayéndose. La infiltración con formaldehído de este segmento afecta a la capacidad de reducir la presión intraventricular, y la duración de la fase de relajación isovolumétrica se prolonga y se alcanza una menor presión mínima. Se produce un descenso significativo en las velocidades del flujo transmitral de la protodiástole y un incremento en la telediástole. Conclusiones. La fase de llenado rápido ventricular es un proceso de contracción (AU)

Introduction and objectives. Left ventricular filling begins in the ventricular isovolumic relaxation phase. According to the Torrent-Guasp myocardial band theory, this phase results from the contraction of the final portion of the myocardial band: the ascending segment of the apical loop. The objectives were to study the myocardial mechanisms influencing transmitral flow during early diastole and to determine whether the rapid ventricular filling phase involves contraction or relaxation. Methods. An experimental in vivo pig model was used. Regional contractility in 3 segments of the myocardial band was assessed using piezoelectric crystals and mitral flow was measured by echo-Doppler ultrasonography at baseline and after akinesia had been induced in the ascending segment by 2.5% formaldehyde infusion. Changes in intracavitary pressure in the left ventricle and left atrium and flow alterations in the aortic root were recorded. The start of the isovolumic relaxation phase was identified using the time at which the ejection of blood ceases, as indicated by aortic flow measurements. Results. During the left ventricular isovolumetric relaxation phase, the ascending segment of the apical loop was undergoing contraction. The infusion of formaldehyde into this segment affected the extent to which the intraventricular pressure could decrease, prolonged the isovolumic relaxation phase and resulted in a lower minimum pressure. It also produced a significant decrease in transmitral flow velocity in early diastole and an increase at end-diastole. Conclusions. The rapid ventricular filling phase is characterized by contraction (AU)

The helical ventricular myocardial band of Torrent-Guasp: potential implications in congenital heart defects.

The new concepts of cardiac anatomy and physiology, based on the observations made by Francisco Torrent-Guasp's discovery of the helical ventricular myocardial band, can be useful in the context of the surgical strategies currently used to manage patients with congenital heart defects. The potential impact of the Torrent-Guasp's Heart on congenital heart defects have been analyzed in the following settings: ventriculo-arterial discordance (transposition of the great arteries), double (atrio-ventricular and ventriculo-arterial) discordance (congenitally corrected transposition of the great arteries), Ebstein's anomaly, pulmonary valve regurgitation after repair of tetralogy of Fallot, Ross operation, and complex intra-ventricular malformations. The functional interaction of right and left ventricles occurs not only through their arrangements in series but also thanks to the structural spiral features. Changes in size and function of either ventricle may influence the performance of the other ventricle. The variety and complexity of congenital heart defects make the recognition of the relationship between form and function a vital component, especially when compared to acquired disease. The new concepts of cardiac anatomy and function proposed by Francisco Torrent-Guasp, based on his observations, should stimulate further investigations of alternative surgical strategies by individuals involved with the management of patients with congenital heart defects.

The helical ventricular myocardial band: global, three-dimensional, functional architecture of the ventricular myocardium.

We are currently witnessing the advent of new diagnostic tools and therapies for heart diseases, but, without serious scientific consensus on fundamental questions about normal and diseased heart structure and function. During the last decade, three successive, international, multidisciplinary symposia were organized in order to setup fundamental research principles, which would allow us to make a significant step forward in understanding heart structure and function. Helical ventricular myocardial band of Torrent-Guasp is the revolutionary new concept in understanding global, three-dimensional, functional architecture of the ventricular myocardium. This concept defines the principal, cumulative vectors, integrating the tissue architecture (i.e. form) and net forces developed (i.e. function) within the ventricular mass. Here we expose the compendium of Torrent-Guasp's half-century long functional anatomical investigations in the light of ongoing efforts to define the integrative approach, which would lead to new understanding of the ventricular form and function by linking across multiple scales of biological organization, as defined in ongoing Physiome project. Helical ventricular myocardial band of Torrent-Guasp may also, hopefully, allow overcoming some difficulties encountered in contemporary efforts to create a comprehensive mathematical model of the heart.

The sequence of regional ventricular motion.

OBJECTIVE: The chronology of electrical events that mechanically activate the myocardium has been described as initiating at the level of the septum, spreading to the apex, then to the bodies of both ventricles and eventually to the base of the heart (apex-to base activation). It has recently been suggested that the myocardium is a single muscular band that conforms a double-loop helicoid. Contraction of the myocardium would follow the trajectory of the muscular fibers that originate at the pulmonary artery towards the body of the left ventricle and to the aorta (base-to apex contraction). This would explain the movements of the base of the heart and the twisting motion of the ventricles seen at magnetic resonance studies. METHODS: Temporal Fourier analysis of equilibrium radionucleide angiocardiography, by studying the topography of the regional myocardial mechanical displacement corresponding to the wave front of electro-mechanical activation, provides information on the sequence of regional ventricular contraction was used in 29 normal individuals to observe the sequence of myocardial motion. RESULTS: Analysis disclosed that the base of the heart first moves (right then left ventricle) and mechanical movement later descends to involve the apex and the septum. These findings are in concordance with the proposed activation of the helical myocardium and open the way to more complex studies. CONCLUSIONS: Although electrical activation of the myocardium (QRS complex) follows a septum-apex-body-base of the left ventricle sequence, mechanical activation follows a base-to-apex sequence. This is likely to be related to anisotropic propagation of the electromechanical stimulus throughout the myocardial band once the electrical stimulus has been delivered at the base of the heart.

Towards new understanding of the heart structure and function.

Structure and function in any organ are inseparable categories, both in health and disease. Whether we are ready to accept, or not, many questions in cardiovascular medicine are still pending, due to our insufficient insight in the basic science. Even so, any new concept encounters difficulties, mainly arising from our inert attitude, which may result either in unjustified acceptance or denial. The ventricular myocardial band concept, developed over the last 50 years, has revealed unavoidable coherence and mutual coupling of form and function in the ventricular myocardium. After more than five centuries long debate on macroscopic structure of the ventricular myocardium, this concept has provided a promising ground for its final understanding. Recent validations of the ventricular myocardial band, reviewed here, as well as future research directions that are pointed out, should initiate much wider scientific interest, which would, in turn, lead to reconciliation of some exceeded concepts about developmental, electrical, mechanical and energetical events in human heart. The benefit of this, of course, would be the most evident in the clinical arena.

Systolic ventricular filling.

The evidence of the ventricular myocardial band (VMB) has revealed unavoidable coherence and mutual coupling of form and function in the ventricular myocardium, making it possible to understand the principles governing electrical, mechanical and energetical events within the human heart. From the earliest Erasistratus' observations, principal mechanisms responsible for the ventricular filling have still remained obscured. Contemporary experimental and clinical investigations unequivocally support the attitude that only powerful suction force, developed by the normal ventricles, would be able to produce an efficient filling of the ventricular cavities. The true origin and the precise time frame for generating such force are still controversial. Elastic recoil and muscular contraction were the most commonly mentioned, but yet, still not clearly explained mechanisms involved in the ventricular suction. Classical concepts about timing of successive mechanical events during the cardiac cycle, also do not offer understandable insight into the mechanism of the ventricular filling. The net result is the current state of insufficient knowledge of systolic and particularly diastolic function of normal and diseased heart. Here we summarize experimental evidence and theoretical backgrounds, which could be useful in understanding the phenomenon of the ventricular filling. Anatomy of the VMB, and recent proofs for its segmental electrical and mechanical activation, undoubtedly indicates that ventricular filling is the consequence of an active muscular contraction. Contraction of the ascendent segment of the VMB, with simultaneous shortening and rectifying of its fibers, produces the paradoxical increase of the ventricular volume and lengthening of its long axis. Specific spatial arrangement of the ascendent segment fibers, their interaction with adjacent descendent segment fibers, elastic elements and intra-cavitary blood volume (hemoskeleton), explain the physical principles involved in this action. This contraction occurs during the last part of classical systole and the first part of diastole. Therefore, the most important part of ventricular diastole (i.e. the rapid filling phase), in which it receives >70% of the stroke volume, belongs to the active muscular contraction of the ascendent segment. We hope that these facts will give rise to new understanding of the principal mechanisms involved in normal and abnormal diastolic heart function.

La mecánica agonista-antagonista de los segmentos descendente y ascendente de la banda miocárdica ventricular / Agonist-Antagonist Mechanics of the Descendent and Ascendent Segments of the Ventricular Myocardial Band

En este artículo se expone la estructura macroscópica del miocardio ventricular, que se halla configurada por una banda en la que pueden ser diferenciados cuatro segmentos. Tal banda miocárdica ventricular describe en el espacio, a lo largo de su trayectoria desde la raíz de la arteria pulmonar a la raíz aórtica, una helicoide con dos espirales mediante las que son delimitadas dos cavidades, los mal llamados ventrículo derecho y ventrículo izquierdo. El interés por alcanzar un entendimiento sobre la coherente relación necesariamente existente entre el referido hecho anatómico y la mecánica cardíaca, coherencia siempre habida entre la forma y función de todo órgano, ha inducido al desarrollo de unos estudios experimentales según los cuales la disminución del volumen de las cavidades ventriculares, acompañada de un descenso de la base de los ventrículos, tiene lugar gracias a la contracción agonista del segmento descendente de la banda, previamente sometido a una elongación rectilínea, mientras el aumento del volumen ventricular, acompañado de un ascenso de la base de los ventrículos, acaece a consecuencia de la contracción antagonista del segmento ascendente de la banda, previamente sometido a una elongación curvilínea (AU)