Isometric Contraction and Relaxation Times of Right and Left Ventricles in Normal Subjects and in Patients with Right Ventricular Overloading Measured with Bidirectional Echocardiography

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Abstract
With the use of bidirectional echocardiography, the isometric contraction (ICT) and relaxation times (IRT) of both ventricles were measured in 14 normal subjects (N), 6 cases with right ventricular (RV) diastolic overloading (DO) and 5 cases with RV systolic overloading (SO). The RVDO group consisted of patients with atrial septal defect of ostium secundum type who had large left-to-right shunting, and the RVSO group those with pulmonary hypertension of various origins. The mean ICT and IRT in N were 28.5 .+-. 4.8 and 43.8 .+-. 1.7 ms for RV, and 43.3 .+-. 5.6 and 60.9 .+-. 9.0 ms for left ventricle (LV), respectively. The RVDO group showed no significant change in the mean ICT and IRT of RV (29.7 .+-. 4.6 and 54.3 .+-. 11.8 ms, respectively), but significantly greater means of ICT and IRT of LV (58.5 .+-. 9.5 and 83.6 .+-. 14.1 ms, respectively). In the RVSO group, the mean ICT and IRT were 51.0 .+-. 4.1 and 86.8 .+-. 8.2 ms for RV, and 72.4 .+-. 12.2 and 116.0 .+-. 20.4 ms for LV, respectively. These values were all significantly greater than the means for both N and RVDO groups, except that the mean ICT of LV was insignificantly different between the RVDO and RVSO groups. Intervals of LV tended to increase with the increasing intervals of RV, suggesting the changes in LV function secondarily due to RV overloading. Measurement of ICT and IRT of both ventricles is of clinical value for evaluation of overall cardiac function in the patients with RV overloading.