| Irregular fetal heart rhythms are common in clinical practice. Most ofthem are paroxysmal, and heart anatomies are normal. They can restoresinus rhythm without treatment. A few of them may be associated withfetal hydrops, structural heart disease, neurological complications, andfetal demise. So they usually require aggressive treatment to eliminate therisk of cardiac failure. To identify fetuses with arrhythmia, normal valuesfirst have to be obtained.The aim of present study was to establish reference values of normalfetal heart conduction time intervals by spectral tissue Doppler and pulseDoppler methods, and to assess the influence of both gestational age andfetal heart rate on those intervals.STUDY POPULATION AND METHODSFrom December, 2006 to June, 2007, we randomly enrolled 201consecutive pregnant women, of whom 189 were recruited into study group (age 28±3 years, range 19～38 years, gestation age 30±6 weeks,range 16～41 weeks). Twelve were ruled out because of congenital heartdisease, sustained arrhythmia or bigeminal pregnancy.A detailed echocardiographic examination was performed with GEVivid-7, Siemens Sequoia 512, or IE 33 ultrasound system with 1.7～8.0MHz sector transducers.1. General obstetrics examination: Fetal position was assessed andfetal gestational age was estimated by measuring biparetal diameter andfemur length.2. Left or right ventricle was distinguished by fetal position, spine,liver, aerogastria, descending aorta or the blood direction of foramenovale. In a 5-chamber view with the septum in a vertical position,velocities generated by both the inflow of blood through the mitral valveduring the diastole and by the outflow through the left ventricular outletduring systole were recorded. All TDI measures were obtained fromannulus of mitral valve. Care was taken to direct the transducer beam asclose as possible to the Doppler beam at <20°in selected planes.2.1 Measure atrio-ventricular conduction time intervals (AV) and thetime intervals from onset of ventricular contraction to the onset of atrialcontraction of next cardiac cycle (VA).Using TDI approach, the start of the Aa wave which represented themovement of annulus of mitral valve during lated diastolic stage was taken as onset of atrial contraction, and the start of the Sa wave duringsystolic phase was taken as onset of ventricular contraction. TDI-AV wascalculated from the beginning of Aa wave to the beginning of the Sawave, and TDI-VA was from the beginning of the Sa wave to thebeginning of next Aa wave.Using the pulse Doppler technique, flow-velocity waveforms throughthe mitral valve were recorded with ejection waves toward the aorta byplacing the sample volume in the lower part of the outflow tract of the leftventricle. On these tracings, atrial contraction corresponded to the start ofthe Doppler A wave, and ventricular contraction to the beginning of theventricular ejection wave (S wave) going in the opposite direction. Withthat approach, PD-AV was measured between the start of A wave to thestart of S wave, and PD-VA was between the start of S wave to the startof next A wave.2.2 To account for slight variations in measurements, each parameterwas measured in 3 consecutive beats and the values averaged to obtaineach interval duration. In fetuses with intermittent arrhythmia, AV andVA measured when arrhythmia were compared with normal sinusrhythm.3. Statistic analysisAll statistics were carried out using SPSS 13.0 software. A probabilityvalue <0.05 was considered as statistically significant. RESULTS1. Two hundred and one fetal echocardiogaphic examinations wereperformed in 201 fetuses, among them 172with normal cardiac structureand normal rhythm, 17 with intermittent arrhythmia, and 12 withcongenital heart disease, sustained arrhythmia or bigeminal pregnancy.2. TDI-AV is (126.56±15.33) ms, 95%CI: (124.10～129.03) ms.TDI-VAis (285.22±24.53) ms, 95%CI: (281.27～289.16) ms.PD-AVis (127.42±12.88) ms, 95%CI: ( 125.35～129.49) ms. PD-VA is(287.42±25.19)ms, 95%CI: (283.37～291.47)ms. A paired t test directlycompared two approaches used to measure AV and VA, which revealedno systematic difference (t value is 0.306,1.363, respectively, P>0.05).3. AV and VA were significantly positively correlated with gestationalage, and negatively correlated with fetal heart rate. We divided all fetusesinto different group according to the gestational age or fetal heart rate.The results revealed that VA had significantly difference among differentheart rate groups. AV had no significantly difference among differentheart rate groups. AV, VA had no significantly difference among differentage groups.4. Heart conduction time intervals were altered in fetus withparoxysmal arrhythmia.CONCLUTIONSThis study established the normal values of fetal heart conduction times. AV and VA were significantly positively correlated withgestational age, and significantly negatively correlated with fetal heartrate. This investigation suggests important potential clinical utility of fetalheart conductional times in assessing congenital atrio-ventricular block.Further study is warranted.
|
PDF Full Text Request