Right ventricular outflow tract (RVOT) dimensions were recorded from left parasternal short axis view at the level of aortic root (15). M-mode cursor was used. RVOT anterior wall thickness and cavity dimensions were measured in end-diastole and end-systole (Fig. 2a). Fractional shortening was calculated. Pulsed Doppler evaluation of pulmonary artery flow was performed in left parasternal short axis view at the level of aortic

root. Sample volume was kept just distal to pulmonary valve. Peak velocity and acceleration time were analyzed (Fig. 2b).

 

Tricuspid annulus plane systolic excursion was measured using M-mode cursor in apical four-chamber view (16). Lateral and septal parts of annulus were evaluated (Fig. 2c & d). Systolic excursion and slope were analyzed. Tricuspid flow velocities were recorded by pulsed Doppler method. Sample volume was placed at the level of tip of tricuspid leaflets in diastole. Early (E) and late (A) diastolic velocities were recorded

(Fig. 3a). Velocity time integral (VTI) of E- and A-wave were analyzed. E/A ratio was calculated. Deceleration time of E-wave and duration of A-wave were analyzed. When A-wave started before end of E-wave, deceleration time of E-wave was calculated by extrapolation of initial slope to base line. Tricuspid flow propogation velocity (Vp) was recorded in the same view using color Doppler and keeping M-mode cursor in the tricuspid flow. Slopes of early and late diastolic flow were measured (Fig. 3b). Tissue Doppler imaging was also performed in apical four-chamber view (9). Sample volume was kept over medial and lateral part of tricuspid annulus (Fig. 4a & b). Ultrasound beam was kept perpendicular to the plane of the annulus to minimize angle of incidence. Systolic velocity (Sa), early diastolic velocity (Ea), late diastolic velocity (Aa), their VTI, isovolumic contraction time (IVCT), isovolumic relaxation time (IVRT) and ejection time were analyzed and myocardial performance index (MPI) was calculated.

 

IVC dimension was 4.4±1.0 mm in expiration and 1.8±0.6 mm in inspiration. Inspiratory collapse was 66.5±13.5%. HV size was 4.6±1.1 mm. HV and SVC flow patterns are shown in Table 1. Systolic wave velocity was more than diastolic wave velocity. Atrial reversal wave had minimum velocity and VTI. Velocities were more in HV than in SVC. Tricuspid flow A-wave duration was more than duration of atrial reversal wave in HV. RVOT anterior wall thickness was 2.2±0.5 mm in end diastole and 3.2±0.8 mm in end systole. Systolic excursion was 3.9±0.8 mm. RVOT cavity dimensions were 10.8±1.9 mm in end diastole and 4.0±1.0 mm in end systole. Fractional shortening was 63.1±6.7%. Pulmonary artery flow peak velocity was 0.7±0.2 cm/sec. Acceleration time was 88.5±17.6 msec. Medial tricuspid annulus plane systolic excursion was 6.1±1.0 mm with a slope of 27.6±6.2 cm/sec. Lateral tricuspid annulus plane systolic excursion was 8.3±1.6 mm with a slope of 37.1±9.0 cm/sec. Pulsed Doppler parameters of tricuspid flow are shown in Table 2. A wave velocity and VTI were more than respective values of E-wave. E/A ratio was less than 1. Velocity of propogation of early tricuspid flow was 44.5±11.9 cm/sec. Vp of late tricuspid flow was 211.1±105.1 cm/sec. E/Vp was 3.2±1.6. Slope of late diastolic flow was rapid than slope of early diastolic flow. Tissue Doppler imaging velocities of medial and lateral part of tricuspid annulus are shown in Table 3. All velocities were more along lateral part of tricuspid annulus. Late diastolic velocity (Aa) was more than early diastolic velocity (Ea).

 

IVC showed inspiratory collapse of more than 50%. This reflects normal inspiratory fall in right ventricular and right atrial pressure (17,18).There is no previous literature about this parameter in neonates. In SVC and HV flow, systolic velocity was more than diastolic velocity with small reversal wave during atrial contraction. This suggests normal filling pattern of right atrium with greater filling in systole than in diastole (19,20). Flow velocities were greater in HV than in SVC. This could be because of closer proximity of HV to right atrium and also because of relatively less compliance of HV (21). Tricuspid flow A-wave duration was more than the duration of atrial reversal wave in HV. There is no previous literature on this parameter. This finding correlates with greater A-wave duration of mitral flow than duration of atrial reversal flow in pulmonary vein (PVa) in normal persons (22).

 

Evaluation of RVOT revealed good systolic thickening of anterior wall and fractional shortening of more than 50%. These findings are considered suggestive of normal RV systolic function (15). Pulmonary artery flow peak velocity was normal. Pulmonary flow acceleration time is the time interval between beginning of the flow and its peak velocity (23). It was slightly lower in neonates. It could be due to increased afterload caused by physiological pulmonary hypertension. Tricuspid annular excursion reflects longitudinal shortening of the right ventricle (24). Greater excursion of lateral part of the annulus is because the lateral wall of right ventricle is rich in longitudinal fibers. Interventricular septum has more of circumferencial fibers (16,25). Koestenberger et al. (26) evaluated lateral tricuspid annulus plane systolic excursion in infants, children and adolescents. They reported a mean value of 0.91 cm for lateral tricuspid annulus in neonates as a whole (0–30 days). Our observation during first week of life is 0.8±0.2 cm. Slight difference could be due to the effect of maturation with advancing age (7, 11). There is no literature about systolic excursion of medial tricuspid annulus in neonates. We observed a relatively lower value 0.6±0.1 cm for medial tricuspid annulus. This is understable because interventricular septum has less longitudinal fibers (25).

 

Doppler evaluation of tricuspid flow revealed that late diastolic flow (A) velocity was more than early diastolic (E) flow velocity. E/A ratio was less than 1. Increased A-wave velocity suggests impaired relaxation of right ventricle resulting in forceful right atrial contraction. This finding is in agreement with observation of previous workers (6–9). These observations suggest impaired relaxation of right ventricle in first week of life. This could be because of only partial regression of right ventricular dominance of fetal circulation. Velocity of propogation of late diastolic tricuspid flow was more than that of early diastolic flow suggesting impaired relaxation with rapid filling of RV during right atrial contraction.

 

Tissue Doppler imaging velocities revealed that all velocities were more along lateral part of tricuspid annulus. Late diastolic velocity (Aa) was more than early diastolic velocity (Ea). Previous studies on lateral tricuspid annulus in neonates had similar observations (9,27). These observations also suggest impaired relaxation of right ventricle during neonatal period. Systolic velocity (Sa) observed by us (6.4±1.0 cm/sec) is similar to values observed by Mori et al. (9) (6.2±1.1 cm/sec) and Alp et al. (6.5±1.4 cm/sec) (27) in neonates.

 

Ea/Aa ratio (0.9±0.2) and E/Ea ratio (7.1±2.3) of lateral tricuspid annulus are similar to values observed by Alp et al. on first day of life (Ea/Aa 0.72±0.14, E/Ea 7.9±1.6) (27). There is no literature about tissue Doppler imaging velocities of medial tricuspid annulus in neonates. Tissue Doppler imaging of medial tricuspid annulus is also important in evaluation of right ventricular function (28).We observed that Ea/Aa ratio of medial as well as lateral tricuspid annulus was less than 1. This finding also supports impaired relaxation of right ventricle in early neonatal period. We observed that IVRT of lateral tricuspid annulus was 45.3±14.9 msec in neonates. Right ventricular isovolumic relaxation time correlates with pulmonary artery pressure (29). IVCT in our subjects was 44.8±13.2 msec. There is no literature on this parameter in neonates. IVCT corelates with rate of systolic shortening of RV (30). Right ventricular MPI (Tei index) was 0.42±0.13 in our subjects. This could be due to prolonged IVRT. Tei index gives an overall impression about systolic and diastolic performance of RV(31).

 

 

At present, there is paucity of data on normal values of various echocardiographic parameters of right ventricular systolic and diastolic function in healthy neonates during first week of life. Right ventricle shows impaired relaxation pattern during this period. This could be due to only partial regression of right ventricular dominance of fetal circulation. Our data provide preliminary information on this topic.

 

 

Sample size is small. This was because we strictly followed exclusion criteria. Getting well-informed written concent from parents of healthy asymptomatic neonates was another difficulty. Study of larger number of neonates can priovide more information and reference values. Long-term follow-up of same neonates can provide more information about progressive changes in right ventricular function. Comparison with neonates with right ventricular overload, their long-term follow-up and post-operative results is needed to find clinical utility of our observations.

 

Nil

 

Nil

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