In my book Nixonland, I describe how the tacking between uplifting rhetoric and snarling rhetoric, between the "old Nixon" who slashed and burned and the "new Nixon," when he reinvented himself in the image of America's hopes instead of its fears, was the systole and diastole of Nixon's political heartbeat.
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19(4): 481–90. Background of this approach is that pulsatile tissue impedance changes according to differences in the filling of blood vessels between systole and diastole, particularly when injecting saline as contrasting agent.
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Windkessel physiology remains a relevant yet dated description of important clinical interest. The historic mathematical definition of Systole and Diastole in the model are obviously not novel but are here elementally staged to four degrees. Reaching five would be original work.
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Cardiac action potential consists of two cycles, a rest phase, and an active phase. These two phases are commonly understood as systole and diastole. The rest phase is considered polarized. The resting potential during this phase of the beat separates the ions such as sodium, potassium, and calcium.
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As an early sympathetic historian of the Gaelic world in English, O'Halloran has faced criticism for being too sympathetic. In the 1770s a critic suggested he should: :drop any more scribbling, and mind the Systole and Diastole of the human body, which I suppose you are more acquainted with than history.Lyons, op cit., page 68.
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Cardiac rhythmicity is the spontaneous depolarization and repolarization event that occurs in a repetitive and stable manner within the cardiac muscle. Rhythmicity is often abnormal or lost in cases of cardiac dysfunction or cardiac failure. It is the ability of the heart to maintain a relatively stable relation between its systole and diastole. Not increasing one on the expense of the other.
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Flow- independent NEMRA methods are not based on flow, but exploit differences in T1, T2 and chemical shift to distinguish blood from static tissue. Gated subtraction fast spin-echo: An imaging technique that subtracts two fast spin echo sequences acquired at systole and diastole. Arteriography is achieved by subtracting the systolic data, where the arteries appear dark, from the diastolic data set, where the arteries appear bright. Requires the use of electrocardiographic gating.
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Cardiac systole and diastole Blood flow velocity waveforms in the central retinal artery (red) and vein (blue), measured by alt= During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure. The blood pressure in the circulation is principally due to the pumping action of the heart. Differences in mean blood pressure drive the flow of blood around the circulation. The rate of mean blood flow depends on both blood pressure and the resistance to flow presented by the blood vessels.
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Cardiac cycle shown against ECG The period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle. The period of contraction that the heart undergoes while it pumps blood into circulation is called systole. The period of relaxation that occurs as the chambers fill with blood is called diastole. Both the atria and ventricles undergo systole and diastole, and it is essential that these components be carefully regulated and coordinated to ensure blood is pumped efficiently to the body.
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The oblique vein of the left atrium (oblique vein of Marshall) is a small vessel which descends obliquely on the back of the left atrium and ends in the coronary sinus near its left extremity; it is continuous above with the ligament of the left vena cava (lig. venæ cavæ sinistræ vestigial fold of Marshall), and the two structures form the remnant of the left Cuvierian duct. This obscure region of cardiac perfusion adjacent to the SA node rocks back and forth under systole and diastole thus further influencing cardiac autonomic innervation. Ablation of this channel seems reasonable to many observers.
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Several imaging methods can be used to assess the anatomy and function of the heart, including ultrasound (echocardiography), angiography, CT scans, MRI and PET. An echocardiogram is an ultrasound of the heart used to measure the heart's function, assess for valve disease, and look for any abnormalities. Echocardiography can be conducted by a probe on the chest ("transthoracic") or by a probe in the esophagus ("transoesophageal"). A typical echocardiography report will include information about the width of the valves noting any stenosis, whether there is any backflow of blood (regurgitation) and information about the blood volumes at the end of systole and diastole, including an ejection fraction, which describes how much blood is ejected from the left and right ventricles after systole.
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