Echocardiography
All patients underwent a screening echocardiographic examination within 6-72 h of CICU admission. Relevant data were collected from the clinical echocardiographic exam reports. Echocardiography was performed by Philips IE-33 equipped with S5-1 transducers (Philips Healthcare, Andover, MA, USA), and GE Vivid 7 model equipped with M4S transducer.
RV qualitative size and function assessment were based on multiple views of the right ventricle (short-axis parasternal at basal, mid, and apical levels; lower parasternal RV inflow view; apical four-chamber view and, if possible, RV long-axis view; and subcostal short-axis and four-chamber views). Using these multiple views, an integrative qualitative grading was
formulated by the physician responsible for the echocardiographic study. From four-chamber views encompassing the entire right ventricle, end-systolic and end-diastolic RV areas and the tricuspid annulus were measured. Apart from qualitative grading, RV function was evaluated by tricuspid annular plane systolic excursion (TAPSE) 12.
TR severity was determined using an integrative, semiquantitative approach as recommended by the American Society of Echocardiography13.
Regarding the gravity of tricuspid regurgitation, we first assessed the severity of valve regurgitation by evaluating specific signs that would point to either less than mild or severe regurgitation, including color jet area (thin small central vs large >50% jet area), vena contracta (VC) width (<0.2 cm or ≥7 mm), density of continuous Doppler jet (faint or dense and triangular), hepatic vein flow pattern (systolic dominant vs systolic reversal), trans tricuspid inflow pattern (A-wave dominant or high-velocity E-wave dominant), annular diameter (normal vs dilated annulus with lack of valve coaptation), and RV and right atrial (RA) size (normal vs dilated). If all of the signs and indices were concordant, we defined TR as less than mild or severe. If the signs or values of the qualitative or semiquantitative parameters were in the intermediate range between mild and severe, we defined TR as at least moderate to severe if the majority (five or more) of the signs and indices were concordant with severe TR13.
In patients with measurable tricuspid regurgitation jet on Doppler echocardiography peak systolic pulmonary artery pressure (SPAP) was estimated using the modified Bernoulli formula (4 × TRV2max) + RAP, where TRVmax is the peak systolic tricuspid regurgitation velocity at end expiration, and RAP is the right atrial pressure. Left ventricular (LV) diameters and interventricular septal and posterior wall width were measured from the parasternal short axis by means of a 2-dimensional (2D or a 2D-guided M-mode echocardiogram of the LV at the papillary muscle level using the parasternal short-axis view14. LV ejection fraction was calculated by the Biplane method of disks (modified Simpson’s rule). Early trans mitral flow velocity (E) was measured in the apical 4-chamber view to provide an estimate of LV diastolic function 15. Early diastolic mitral annular velocity (e′) was measured using spectral tissue Doppler imaging in both septal and lateral positions. The ratio of peak E to peak e′ was calculated (E/e′ ratio) from the average of at least 3 cardiac cycles. In patients with atrial fibrillation we have used the average measured from 5-7 cardiac cycles. Left atrial volume was calculated using the biplane area length method at end systole 16. Cardiac output was calculated as the product of aortic stroke volume and heart rate as demonstrated on pulse wave Doppler. Valvular regurgitation was qualitatively assessed using color Doppler according to the guidelines of the American Society of Echocardiography (normal/trivial = 1, mild = 2, moderate = 3,severe = 4) 17. Diastolic function was assessed by integrating measurements of the mitral inflow, left atrial volume, and Doppler tissue imaging of the mitral annulus using the average annulus velocity, and classified into four categories: normal diastolic function = 0, impaired relaxation = 1, pseudo-normal = 2 and restrictive pattern = 3, based on recent guidelines15. Right atrial (RA) pressure was estimated by the inferior vena cava diameter as well as its response to inspiration as previously described 18. Briefly, expiratory and inspiratory inferior vena cava (IVC) diameters and percent collapse were measured in subcostal views within 2 cm of the right atrium. IVC diameter <2.1 cm that collapsed >50% with a sniff suggested a normal RA pressure (assigned as 5 mmHg), whereas an IVC diameter >2.1 cm that collapsed <50% with a sniff suggested a high RA pressure (15 mmHg). In patients with IVC diameter <2.1 cm and no collapse (<20%) with a sniff, RA pressure was upgraded to 20 mmHg. In indeterminate cases in which the IVC diameter and collapse did not fit this paradigm, secondary indices of elevated RA pressure were integrated. If uncertainty remained, RA pressure was left as intermediate value of 10 mmHg.