Pathophysiology of tricuspid regurgitation: quantitative Doppler echocardiographic assessment of respiratory dependence.

BACKGROUND: Respiratory dependence of tricuspid regurgitation (TR), a long-held concept suggested by murmur variation, remains unproven and of unclear mechanisms. METHODS AND
RESULTS: In 41 patients with mild or greater TR (median age, 67 years), we performed triple Doppler echocardiographic quantification (TR severity, right ventricular, and right atrial quantification) with simultaneous respirometer recording of respiratory phases. Expiration to inspiration changes (median) affected TR peak velocity (-40 cm/s; 25th to 75th percentile, -60 to -30 cm/s), duration (-12 milliseconds; 25th to 75th percentile, -45 to 2 milliseconds), and time-velocity integral (-17 cm; 25th to 75th percentile, -23.4 to -10 cm; all P<0.001), consistent with decreased TR driving force. Nevertheless, inspiratory TR augmentation was demonstrated by increased effective regurgitant orifice (0.21 cm(2); 25th to 75th percentile, 0.09 to 0.34 cm(2)) and volume (18 mL per beat; 25th to 75th percentile, 10 to 25 mL per beat; all P<0.001) infrequently detected clinically (2 of 41, 5). As a result of reduced TR driving force, regurgitant volume increased less than effective regurgitant orifice (120 [25th to 75th percentile, 78.6 to 169] versus 169 [ 25th to 75th percentile, 12.9 to 226.1]; P<0.001). During inspiration, right ventricular area increased (diastolic, 27.8 [25th to 75th percentile, 22.6 to 36.3] versus 26.5 [21.1 to 31.9]; P<0.0001) with widening of right ventricular shape (length-to-width ratio, 1.6 [ 25th to 75th percentile, 1.37 to 1.95] versus 1.7 [1.46 to 2.1]; P<0.0001), increased systolic annular diameter (P=0.003), valve tenting height (P<0.0001) and area (P<0.0001), and reduced valvular-to-annular ratio (P=0.006). Effective regurgitant orifice during inspiration was independently determined by inspiratory valvular-to-annular ratio (P=0.026) and inspiratory change in right ventricular length-to-width ratio (P=0.008) and valve tenting area (P=0.015).
CONCLUSIONS: TR is dynamic with almost universal respiratory changes of large magnitude and complex pathophysiology. During inspiration, a large increase in effective regurgitant orifice causes, despite a decline in regurgitant gradient, a notable increase in regurgitant volume. Effective regurgitant orifice changes are independently linked to inspiratory annular enlargement (decreased valvular coverage) and to inspiratory right ventricular shape widening with increased valvular tenting. These novel physiological insights into TR respiratory dependence underscore right-side heart plasticity and are important for clinical TR severity evaluation.