Isovolumic relaxation time
Encyclopedia
Cardiac cycle
The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next. The frequency of the cardiac cycle is described by the heart rate. Each beat of the heart involves five major stages...
, from the aortic component of the second heart sound, that is, closure of the aortic valve
Aortic valve
The aortic valve is one of the valves of the heart. It is normally tricuspid , although in 1% of the population it is found to be congenitally bicuspid . It lies between the left ventricle and the aorta....
, to onset of filling by opening of the mitral valve. It can be used as an indicator of diastolic dysfunction
Diastolic dysfunction
Diastolic heart failure or diastolic dysfunction refers to decline in performance of one or both ventricles of the heart during the time phase of diastole...
.
It can be measured by simultaneous Doppler echocardiography
Doppler echocardiography
Doppler echocardiography is a procedure which uses ultrasound technology to examine the heart. An echocardiogram uses high frequency sound waves to create an image of the heart while the use of Doppler technology allows determination the speed and direction of blood flow by utilizing the Doppler...
and M-mode sonography, or better still, by simultaneous phonocardiogram
Phonocardiogram
A Phonocardiogram or PCG is a plot of high fidelity recording of the sounds and murmurs made by the heart with the help of the machine called phonocardiograph, or "Recording of the sounds made by the heart during a cardiac cycle." The sounds are thought to result from vibrations created by closure...
and transmitral Doppler.
Prolonged IVRT indicates poor myocardial relaxation. A normal IVRT is about 70 ± 12 ms, and approximately 10ms longer in people over forty years. In abnormal relaxation, IVRT is usually in excess of 110ms. With restrictive ventricular filling, it is usually under 60 ms.