Isovolumic relaxation time

Wiggers Diagram

Isovolumic Relaxation Time (IVRT) is an important parameter in the field of cardiology and echocardiography used to assess the function of the heart's ventricles. IVRT refers to the interval between the closure of the aortic valve and the opening of the mitral valve, during which the ventricle relaxes but does not change in volume. This period is crucial for understanding diastolic function, as it provides insights into the relaxation properties of the ventricle and can indicate potential cardiac abnormalities.

Physiology

During the cardiac cycle, the heart undergoes a series of contractions and relaxations to pump blood throughout the body. The cycle can be divided into systolic and diastolic phases. Systole refers to the phase where the heart contracts to pump blood out, while diastole is when the heart relaxes to fill with blood. IVRT occurs at the beginning of the diastolic phase, after the systolic ejection of blood into the aorta, marked by the closure of the aortic valve, and ends when the mitral valve opens to allow blood to fill the ventricle.

The duration of IVRT can be affected by several factors, including heart rate, age, and various pathological conditions. A shortened IVRT may indicate increased filling pressures or diastolic dysfunction, whereas a prolonged IVRT can be a sign of impaired ventricular relaxation.

Measurement

IVRT is most commonly measured using Doppler echocardiography, a non-invasive imaging technique that utilizes sound waves to create images of the heart and assess its function. By placing the Doppler probe in specific positions on the chest, clinicians can measure blood flow velocities across the heart valves, from which IVRT can be calculated.

Clinical Significance

IVRT is a valuable diagnostic tool in assessing diastolic function. Abnormalities in IVRT can be indicative of various cardiac conditions, such as heart failure, restrictive cardiomyopathy, and hypertrophic cardiomyopathy. It is particularly useful in the early detection of diastolic dysfunction, a condition where the heart's ability to relax and fill with blood is impaired, often before symptoms develop.

In clinical practice, IVRT is used alongside other echocardiographic parameters, such as E/A ratio (the ratio of early to late ventricular filling velocities), deceleration time of early filling, and pulmonary venous flow patterns, to provide a comprehensive assessment of diastolic function.

Conclusion

Isovolumic Relaxation Time is a critical parameter in the evaluation of cardiac function, offering valuable insights into the diastolic phase of the cardiac cycle. Its measurement through Doppler echocardiography plays a pivotal role in diagnosing and managing various cardiac conditions, highlighting the importance of IVRT in the field of cardiology.