What does a respiratory variation in the Transverse Relaxation (TR) gradient greater than 50% indicate?

From the Guidelines

A respiratory variation in the tricuspid regurgitation (TR) gradient greater than 50% indicates that the severity of tricuspid valve leakage significantly changes during the respiratory cycle, suggesting right heart hemodynamic changes that vary with breathing, and should prompt further cardiac evaluation to determine the underlying cause of the right heart pressure changes. This finding is crucial in clinical practice as it may indicate right ventricular pressure overload conditions such as pulmonary hypertension, right ventricular dysfunction, or constrictive pericarditis 1. The management of tricuspid regurgitation has been extensively reviewed in recent clinical practice guidelines, including a systematic review published in the European Heart Journal in 2022 1. Some key points to consider in the evaluation of TR include:

• The use of quantitative metrics to assess TR severity, which may provide a more accurate assessment and allow for earlier treatment 1
• The role of multimodality cardiovascular imaging, including 3D echocardiography and cardiac magnetic resonance (CMR), in the quantitative assessment of TR severity and the evaluation of right ventricular function 1
• The importance of considering the location of the tricuspid valve in the mediastinum and the potential for assessment with transthoracic echocardiography (TTE) 1
• The use of CMR to provide complementary and highly accurate information about valve morphology, severity of the regurgitant lesion, cardiac remodeling, and right ventricular function 1. It is essential to integrate these parameters with clinical findings to determine the severity of TR and guide management decisions, as outlined in the 2014 AHA/ACC guideline for the management of patients with valvular heart disease 1. In clinical practice, a respiratory variation in the TR gradient greater than 50% should prompt a comprehensive evaluation, including:
• Comprehensive echocardiography to assess TR severity and right ventricular function
• Right heart catheterization to evaluate pulmonary artery pressures and right ventricular function
• Additional imaging, such as CMR, to provide further information on valve morphology and cardiac remodeling
• Consideration of the patient's symptoms, medical history, and other clinical findings to guide management decisions.

From the Research

Respiratory Variation in TR Gradient

• Respiratory variation in the TR gradient is a significant indicator of the severity of tricuspid regurgitation (TR) 2, 3.
• A variation of more than 50% in the TR gradient suggests that the TR might be influenced by changes in respiration, indicating a dynamic and complex pathophysiology 2.
• This respiratory dependence of TR is characterized by changes in TR peak velocity, duration, and time-velocity integral during expiration and inspiration 2.

Clinical Implications

• Excessive respiratory changes in TR velocities are diagnostic of severe TR, with a sensitivity of 66% and specificity of 94% for a difference in TR velocity ≥0.6 m/s 3.
• Patients with severe TR often have multiple comorbidities and present with advanced tricuspid valve and right ventricular remodelling, limiting treatment options and prognosis 4.
• Early diagnosis and mechanical correction of TR are essential in impacting the natural history of this valvular condition, but this is complicated by the fact that the majority of patients are asymptomatic despite having moderate-to-severe TR 4.

Pathophysiology

• The pathophysiology of TR is complex, with almost universal respiratory changes of large magnitude, and is influenced by factors such as inspiratory valvular-to-annular ratio, right ventricular shape widening, and valve tenting area 2.
• During inspiration, a large increase in effective regurgitant orifice causes, despite a decline in regurgitant gradient, a notable increase in regurgitant volume 2.
• The effective regurgitant orifice changes are independently linked to inspiratory annular enlargement and to inspiratory right ventricular shape widening with increased valvular tenting 2.