Doppler and M-mode ultrasonography to time fetal atrial and ventricular contractions

Objective: To compare ease of recording and reliability of ultrasonographic approaches used to time fetal heart atrial and ventricular contractions. Methods: Seventeen consecutive fetuses seen at our fetal cardiology unit fo r possible fetal cardiac arrhythmia were included in this study. The same u ltrasonographer obtained M-mode tracings of atrial and ventricular free wal ls, atrial wall and opening of the aortic valves, a peak of the mitral valv e, and the opening of the aortic valves; and Doppler signals of now-velocit y waveforms in the outflow tract of the left ventricle and simultaneous flo w-velocity waveforms in the aorta and superior vena cava. The outcome measu res were rate of successful attempts and intra- and interobserver reliabili ty coefficients. Results: Valid recordings were made for all patients with one M-mode (atria l and ventricular free walls) and two Doppler (intraventricular, superior v ena cava, and ascending aorta) approaches. Atrioventricular intervals were significantly longer with M-mode compared with Doppler ultrasonography. Rel iability coefficients were excellent (at least 0.89) for all intraobserver measurements. Comparisons of atrioventricular and ventriculoatrial interval measurements made by two observers gave the following intraclass correlati on coefficients (95% confidence interval): atrioventricular = M-mode: 0.87 (0.79, 0.91), left ventricular outflow: 0.93 (0.89, 0.96), superior vena ca ve-aorta: 0.98 (0.97, 0.99); ventriculoatrial = M-mode: 0.79 (0.67, 0.87), left ventricular outflow: 0.97 (0.95, 0.98); superior vena cave-aorta: 0.99 (0.98, 0.99). Conclusion: Fetal atrioventricular intervals measured indirectly from M-mod e or Doppler tracings were equally reliable when measured by the same obser ver; the Doppler approaches had better correlation between measurements mad e by two different observers. (Obstet Gynecol 2000;96: 732-6. (C) 2000 by T he American College of Obstetricians and Gynecologists).