In a healthy heart, all activities and rest during each individual heart cycle or heartbeat are initiated and orchestrated by signals from the heart`s electrical conduction system, which is the heart`s “wiring” that carries electrical impulses through the body of cardiomyocytes, the heart`s specialized muscle cells. These impulses eventually stimulate the heart muscle to contract, thereby expelling blood from the heart chambers into the arteries and cardiovascular system; And they provide a complex and persistent signal system that controls the rhythmic beat of heart muscle cells, especially the generation of complex impulses and muscle contractions in the ear chambers. The rhythmic sequence (or sinus rhythm) of this signal transmission through the heart is coordinated by two groups of specialized cells, the sinus node (AS), located in the upper wall of the right atrium, and the atrioventricular (AV) node, located in the lower wall of the right heart between the atrium and ventricle. The sinus node, often called a pacemaker, is the starting point for generating a wave of electrical impulses that stimulates atrial contraction by creating an action potential via myocardial cells.   The “new” epidemiology of diastolic LGV dysfunction was discussed in Chapter 6 of this volume. Diastolic heart failure is now recognized as a major national health problem, especially in older adults who have a high incidence of LV hypertrophy (LVH). Despite a normal VL injection fraction (LVEF), these patients have symptomatic heart failure and have morbidity and mortality almost equal to those of patients with reduced systolic function. Patients with diastolic heart failure also have a risk of first-onset atrial fibrillation and a higher incidence of stroke. Although LVEF is normal in diastolic heart failure, the ventricular contractile mechanics have been modified to prolong the period of isovolume contraction and relaxation, so that the diastolic filling period becomes shorter and may be insufficient. In systolic and diastolic heart failure, the degree of diastolic dysfunction is a powerful predictor of prognosis. The cardiac cycle refers to all the events that occur from the beginning of a heartbeat to the beginning of the next and can be divided into two parts: a period of relaxation known as diastole and a period of contraction known as systole.
The changes in pressure and volume that occur during the cardiac cycle of the left ventricle are illustrated in Figure 6.2 and serve as a platform to describe important events. It is important that these changes for the left ventricle shown here also occur simultaneously in the right side of the heart in the right atrium, in the right ventricle and in the pulmonary artery. Temporal increases and decreases in the heart`s blood volume (see Wiggers diagram) are also instructive to follow. The red line of the “ventricular volume” provides an excellent trace of the two periods and four stages of a cardiac cycle. Starting with the diastole period: the low-volume plateau of the “Isovolum Relaxations” stage, followed by a rapid climb and two slower climbs, all the components of the “entry phase” – up to the high volume plateau of the “Isovolum Contractions” stage; (Find the legend on the left side of the chart.) Then the systole, including the high stage of “isovolumic contraction”, until the rapid decrease in blood volume (i.e. the vertical fall of the red line tracking), which indicates the emptying of the ventricles during the “sputum” phase of the completed cycle – all equal to a heartbeat. [Citation needed] Valve closure and rapid filling phases are audible with a stethoscope on the chest and can be recorded phonocardiographically after electronic amplification. The first cardiac tone resulting from cardiohema vibrations with closure of the AV valves (mitral valves, tricuspids) announces a ventricular systole.
The second heart tone, shorter and composed of higher frequencies than the first, is associated with the closure of the crescent-shaped valves (aorta and pulmonary) at the end of the ventricular sputum. The sounds of the third and fourth cores are low-frequency vibrations caused by rapid early filling and late diastolic anterior contractile filling, respectively. These sounds can be heard in normal children, but in adults they usually indicate a disease. Isovolumic contraction: the short period of early contraction, when pressure accumulates in the ventricle, but has not yet increased enough to allow sputum, the heart is a four-chamber organ consisting of the right and left halves, called the right heart and left heart. The two upper chambers, the left and right atria, are entry points into the heart for blood flow back from the circulatory system, while the two lower chambers, the left and right ventricles, perform the contractions that expel blood from the heart to flow through the circulatory system. Circulation is divided into a pulmonary circulation, in which the right ventricle pumps oxygen-poor blood through the pulmonary trunk and arteries into the lungs; or systemic circulation – in which the left ventricle pumps/expels freshly oxygenated blood through the body through the aorta and all other arteries. [Citation needed] Figure 11. a) Left ventricular pressure-volume loop (P-V), whose segments correspond to cardiac cycle events: diastolic ventricular filling along the passive P-V curve (phase I), isovolumetric contraction (phase II), ventricular exclusion (phase III) and isovolumetric relaxation (phase IV).
(b) the ventricle emits a final systolic volume determined by the highest isovolumetric P-V line; an isovolumetric contraction (large arrowheads) of different terminal diastolic volumes (preload). Throughout the cardiac cycle, the atria collect oxygen-depleted blood that returns to the heart from the peripheral circulation and coronary circulation (right atria) or pulmonary circulation (left atriums). During diastole, the accumulation of blood in the atria creates a pressure gradient that forces the opening of the AV valves, so that about 75% of this blood can enter the ventricle, which leads to a gradual increase in ventricular diastolic pressure (point A). In late diastole, the contraction of the atria leads to the remaining 25% of the blood in the ventricles, which leads to a further increase in ear and ventricular pressure (point B). This is followed by a contraction of the ventricle, which signals the appearance of mechanical systole. When the ventricles contract, the pressures they contain quickly exceed the ear pressure. This pressure gradient pushes back the brochures of the AV valves and forces them to close (point C). The appearance of ventricular contraction also creates tension on the papillary muscles, which exert additional force on the edges of the leaves to ensure proper alignment of the valves, which helps in their closure. Another ventricular contraction causes the ventricular pressure to exceed the diastolic pressures in the pulmonary artery and aorta, forcing the crescent valves to open (point D). This allows the ventricles to empty their contents into the lung and circulation of the system. Because the crescent-shaped valves are open, the continuous contraction of the ventricles increases the pressure in the pulmonary artery and aorta.
Completion of ventricular sputum causes the pressure in the ventricles to fall below that of the pulmonary artery and aorta. This allows blood in the pulmonary artery and aorta to push back the crescent-shaped valves and close them (point E). The cardiac cycle then begins again with the ventricles filling with blood that has accumulated in the atria. The heart cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and replenishes into blood, called diastole, after a period of robust contraction and pumping of blood, called systole. After emptying, the heart immediately relaxes and expands to receive another influx of blood that returns from the lungs and other body systems before contracting again to pump blood into the lungs and these systems. A core with normal performance must be completely dilated before it can pump again effectively. .