To investigate the left ventricular systolic and diastolic function in patients with pulmonary atresia with intact ventricular septum without coronary-cardiac fistulas after a modified Blalock-Taussig shunt, 14 patients (age range 15 days-16.5 months, mean 4.03±5.6 months) and eight control subjects, matched for age, body surface area and heart rate were evaluated by cross-sectional and Doppler echocardiography. The follow-up interval after palliative procedures ranged from 12 days to 16.3 months (mean 3.67±5.6 months). Compared to controls, in the group of patients the ejection fraction was decreased (61±7% vs 68±5%, p=0.022) while the left ventricular end-diastolic volume indexed for body surface area was increased (72.7±10.8 cc/m2 46.1±12 cc/m2 p=0.0001) with normal values of left ventricular mass indexed for body surface area (67.88±20.9 g/m2 vs 76±10 g/m2 p=NS). Mass-to-volume ratio was lower in patients with pulmonary atresia (0.95±0.38 vs 1.24±0.3, p=0.031). The left ventricular shape index was increased in all patients with pulmonary atresia (1.27±0.26 vs 1±0.01, p=0.009). A significant inverse correlation was noted between the ejection fraction and follow-up (r=−0.71, p=0.04). as well as between the ejection fraction and shape index (r=−0.76, p=0.048). Moreover, the patients with pulmonary atresia had decreased E/A velocity ratio (0.65±0.16 vs 1.35±0.90, p=0.009), decreased normalized peak filling rate (4.16±0.13 sv/s vs 6.88±0.68 sv/s, p=0.0001), increased peak A velocity (0.95±0.17 m/s vs 0.51±0.16 m/s, p=0.0001) and prolonged isovolumic relaxation time (46±5.4 ms vs 34±6.2 ms, p=0.0001) and deceleration time (196.4±32.2 ms vs 116±21.4 ms, p=0.0001). There was a good correlation between the normalized peak filling rate and follow-up (r=−0.80, p=0.04). These data show a progressive compromise of the left ventricular systolic and diastolic function in patients with pulmonary atresia with intact ventricular septum without ventriculocoronary fistulas who had undergone systemic-to-pulmonary arterial shunting. Thus, an earlier biventricular or Fontan type procedure should be recommended.