Isovolumic relaxation is an interval in the cardiac cycle that occurs between aortic component (second heart sound) closure and mitral valve opening (the starting point of filling). Diastolic dysfunction can be detected by measuring this value.
M-mode sonography along with Doppler echocardiography as well as phonocardiogram and transmitral Doppler, can be used to measure it.
A prolonged IVRT shows a poor relaxation of the myocardium. People under the age of forty have IVRTs that are roughly 10 ms longer than those over forty, with an average of 70 12 ms. IVRT is typically greater than 110 ms in aberrant relaxation. It is usually less than 60 ms when there is limited ventricular filling.
Isovolumic Relaxation: Meaning
-
With Isovolumic relaxation, early diastolic filling of the left ventricle decreases, and late diastolic filling of the left ventricle increases with ageing. Increased systolic blood pressure, increased thickness of the left ventricular wall, decreased early diastolic filling, prolonged diastolic relaxation, increased size of the left atrium, and increased late diastolic filling are all common ageing changes that affect left ventricular diastolic function.
-
End-of-phase 4 pressure drops cause an abrupt closure (the aortic valve closes before the pulmonic valve closes) that results in the second heart sound (S2) and the commencement of isovolumetric relaxation. Backflow into the ventricles is related to valve closure, which results in a distinct “incisura or dicrotic” (incisor or dicrotic) in the pressure readings of the ventricles and the aorta, and the pulmonary vessels.
-
Diarrhoea occurs after the closure of the aortic and pulmonary valves and is followed by a gradual decrease in pressure.
-
The pace at which muscle fibres relax, known as lusitropy, determines the rate at which pressure decreases in the ventricles. After contraction, calcium is promptly re-sequestered by the sarcoplasmic reticulum, which regulates this relaxation (see excitation-contraction coupling).
Cardiac Cycle
-
Volumes do not alter even as ventricular pressures fall since all valves are closed. End-systolic volume is the volume of blood remaining in a ventricle, and in the left ventricle, it is approximately 50 ml. When comparing diastolic and systolic volumes, the stroke volume is around 70 ml.
-
Vein return from the lungs continues to raise the left atrial pressure (LAP) in the patient. The v-wave is the name given to the final LAP peak in this phase.
Measuring Isovolumic Relaxation
-
In a study, the Isovolumic Relaxation Period (IRP) was monitored noninvasively from the beginning of the aortic component of second heart sound until the point of separation of mitral leaflets. 83 patients with various forms of heart illness had their IRP assessed. In normal participants, the IRP lasted 58 +/-11 msec.
-
Hypertension (p 0.001), heart failure (HOCM) (p 0.001), aortic stenosis (p 0.05), and aortic incompetence (p 0.001) all contributed to its extension, while congestive cardiomyopathy and mitral stenosis all contributed to its diminution.
-
There was a significant increase in IRP in patients with coronary artery disease and normal systolic LV function (p 0.001); however, IRP decreased in four patients with severe LV dysfunction and severe extra mitral incompetence due to severe coronary disease. There was a connection between IRP and the mitral EF slope, LV systolic shortening, and systemic blood pressure.
-
Normal subjects’ IRP could be predicted using a regression equation that took into account both their blood pressure and heart rate. The PR-Ac time and isovolumic contraction time do not correlate. LV dynamics in the early diastolic phase can be assessed using the IRP.
When is IVRT most helpful?
It is best to use the IVRT interval when it is at one of its extremes, i.e., the furthest from predicted norms, i.e., less than 60 msec or more than 110 msec. In the middle of these two extremes, it is of less use. A middle-aged adult’s typical IVRT lasts about 80 milliseconds. The early mitral valve opening is indicated by an IVRT of less than 60 milliseconds; a long IVRT of more than 100 milliseconds is indicative of delayed left ventricular relaxation and a delayed valve opening.
Conclusion
The time from aortic valve closure to mitral valve opening artefact is called isovolumic relaxation time (IVRT). Isovolumic relaxation changes in length with age in healthy people. It is shorter in the young because of the fast relaxation of the LV, which causes the mitral valve to open earlier.