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Situational syncope is often triggered by urination, swallowing, or coughing. [2] Carotid sinus syncope is due to pressure on the carotid sinus in the neck. [2] The underlying mechanism involves the nervous system slowing the heart rate and dilating blood vessels, resulting in low blood pressure and thus not enough blood flow to the brain. [2]
Venous return curves showing the normal curve when the mean systemic filling pressure (Psf) is 7 mm Hg and the effect of altering the Psf to 3.5, 7, or 14 mm Hg. Hemodynamically, venous return (VR) to the heart from the venous vascular beds is determined by a pressure gradient (venous pressure - right atrial pressure) and venous resistance (RV ...
The Bainbridge reflex is most strong when heart rate is low; when heart rate is already high, additional venous return to the right atrium (i.e. additional increases in blood volume) will indirectly cause relatively greater stimulation of arterial baroreceptors which will reduce the heart rate.
The pressure on the chest is released, allowing the pulmonary vessels and the aorta to re-expand, causing a further initial slight fall in stroke volume (20 to 23 seconds) due to decreased left atrial return and increased aortic volume, respectively. Venous blood can once more enter the chest and the heart; cardiac output increases. Return of ...
The horizontal axis of Guyton diagram represents right atrial pressure or central venous pressure, and the vertical axis represents cardiac output or venous return. The red curve sloping upward to the right is the cardiac output curve, and the blue curve sloping downward to the right is the venous return curve. A steady state is formed at the ...
Pulsus paradoxus, also paradoxic pulse or paradoxical pulse, is an abnormally large decrease in stroke volume, systolic blood pressure (a drop more than 10 mmHg) and pulse wave amplitude during inspiration. Pulsus paradoxus is not related to pulse rate or heart rate, and it is not a paradoxical rise in systolic pressure.
Return of spontaneous circulation (ROSC) is the resumption of a sustained heart rhythm that perfuses the body after cardiac arrest. It is commonly associated with significant respiratory effort. Signs of return of spontaneous circulation include breathing, coughing, or movement and a palpable pulse or a measurable blood pressure.
Due to the intrinsic property of myocardium that is responsible for the Frank-Starling mechanism, the heart can automatically accommodate an increase in venous return, at any heart rate. [1] [10] The mechanism is of functional importance because it serves to adapt left ventricular output to right ventricular output. [3]