Clinical experience with fetal echocardiography

Current ultrasound technology allows for accurate evaluation of the fetal heart. To evaluate the importance and accuracy of the routine clinical use of fetal echocardiography at our center, a consecutive series of 338 fetal cardiac studies of 323 patients was reviewed. Average gestational age was 24 weeks (range, 17 to 39 weeks). Forty-seven (15%) patients with abnormal conditions were detected. The most common indication for fetal cardiac scan was a family history of congenital heart disease (28%). Other indications were maternal diabetes mellitus (25%), fetal dysrhythmia (14%), other major defect (10%), drug exposure (10%), and obstetrician suspicion of fetal congenital heart disease on routine scan (10%). The highest yield of significant abnormal findings was among those referred for dysrhythmia (31%) and obstetrician suspicion of congenital heart disease (29%). Five fetuses with sustained supraventricular tachycardia and hydrops were successfully treated. The combination of fetal bradycardia and structural heart disease was the most ominous finding. Fifteen (4.6%) patients had clear changes in management based on the fetal echocardiogram. Our experience suggests that the routine use of fetal echocardiography is accurate and an important part of the overall management of the pregnancy considered at risk for producing an infant with congenital heart disease.

Response of upper limb blood flow to handgrip exercise after Blalock-Taussig operation (for tetralogy of Fallot) or subclavian flap operation (for aortic isthmic coarctation)

To evaluate the effects of long-term reductions in perfusion pressure on blood flow responses to increased functional demand, 5 patients (aged 12 to 26 years) without normal aortic to subclavian artery blood flow to 1 arm as a result of surgery to treat congenital heart disease were studied. Five age- and sex-matched healthy (control) subjects were also studied. In the patients, forearm blood flow was not different in the surgical and normal arms at rest (3.6 +/- 0.6 vs 4.0 +/- 0.7 ml/min/100 ml, respectively, mean +/- standard error, difference not significant) despite lower systolic blood pressure in the surgical arm (87 +/- 2 vs 115 +/- 2 mm Hg, p less than 0.05). The increases in heart rate, systolic blood pressure, forearm electromyographic activity (index of muscle fatigue) and postexercise forearm blood flow (index of muscle oxygen deficit) were not different in response to 2.5 minutes of submaximal rhythmic handgrip exercise (50% of maximal force) performed with the surgical versus the normal arms. Peak forearm blood flow elicited by combined ischemia and maximal isometric handgrip exercise was not significantly different in surgical and normal arms in the group as a whole (39 +/- 4 vs 43 +/- 3 ml/min/100 ml, difference not significant), although some bilateral deficit (20 to 38%) was observed in 2 patients. No bilateral differences were observed in the control subjects under any condition. The finding of normal physiologic adjustments to submaximal rhythmic handgrip exercise with the surgical arm suggests that oxygen delivery during exercise was adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal cardiac Doppler flow studies in prenatal diagnosis of heart disease

The prenatal diagnosis of fetal cardiac disease has become increasingly accurate as the technology of ultrasound has improved. Although two-dimensional real-time ultrasound remains the primary method of diagnosis, Doppler blood flow velocity estimates can provide valuable pathophysiologic information to support the anatomic diagnosis. We present six cases in which Doppler studies contributed to the accuracy of the diagnosis of fetal heart disease, including tetralogy of Fallot, right and left ventricular hypoplasia, atrioventricular canal defect, double-outlet right ventricle, and pulmonic stenosis. Velocities in these cases are compared with those in normal fetuses. If Doppler flow velocities are not consistent with the observed morphologic changes, further observations are indicated. Inasmuch as most anatomical heart lesions result in altered flow patterns, Doppler investigations of intracardiac and extracardiac flow should be a routine component of the fetal echocardiogram when structural abnormalities are found.

Noninvasive assessment of hemodynamic responses to exercise in pulmonary regurgitation after operations to correct pulmonary outflow obstruction

The influence of pulmonary regurgitation (PR) on exercise capacity is unknown. The hemodynamic responses to exercise in postoperative patients with PR was determined using Doppler-measured regurgitant fraction to indicate PR severity. Maximal heart rate, oxygen consumption and workload capacity were measured during upright cycle ergometry. Cardiac output was measured at rest and during submaximal supine cycle ergometry by pulsed Doppler echocardiography. Oxygen consumption was simultaneously measured and exercise factor was calculated as the change in cardiac output per change in oxygen consumption. Twenty-seven patients were compared with 17 age-, size- and sex-matched control subjects. Patients with PR had larger right ventricles (p less than or equal to 0.001), lower heart rate response (p less than or equal to 0.05), lower maximal oxygen consumption (p less than or equal to 0.005) and lower workloads (p less than or equal to 0.005) when compared with normal control subjects during maximal exercise testing. Exercise factor was the same for both groups. Patients with PR were then separated into mild, moderate and severe groups. Patients with mild PR had a normal response to exercise. However, patients with moderate and severe PR had lower maximal oxygen consumptions and maximal workloads than control subjects. Control, mild and moderate PR groups had similar exercise factors. Patients with severe PR had markedly low cardiac output responses. PR is associated with reduced exercise capability, which is related to the severity of the PR.

Measurement of cardiac output and exercise factor by pulsed Doppler echocardiography during supine bicycle ergometry in normal young adolescent boys

The purposes of this study were to determine the ability of pulsed Doppler echocardiography to consistently and accurately measure cardiac output during exercise, and to measure the exercise factor by Doppler methodology when oxygen consumption was simultaneously measured. Thirty-four healthy young adolescent male volunteers (mean age 13 years) were recruited. Submaximal exercise was performed by supine bicycle ergometry. Cardiac output was calculated as mean velocity X cross-sectional area. Successful rest and exercise determinations of cardiac output were obtained in 81% (n = 52) of the studies. Mean cardiac output increased from 4.6 to 8.9 liters/min (p less than 0.001) during exercise and mean oxygen consumption increased from 212 to 899 ml/min (p less than 0.001). Doppler-estimated rest and exercise cardiac outputs correlated well with simultaneously measured oxygen consumption (r = 0.89, SEE = 1.2 liters/min; y = 0.006 X 3.2 liters/min). Mean exercise factor was 6.4 (1.2 SD). Twenty-six pairs of rest and exercise cardiac output determinations by Doppler technique and indirect Fick method were simultaneously compared in a subset population (r = 0.86, SEE = 1.4 liters/min; slope = 0.93, y intercept = 1.4 liters/min). Results of this study demonstrate that cardiac output and exercise factor can be estimated by pulsed Doppler echocardiography during exercise.

Does transducer selection affect aortic arch velocities?

The hypothesis tested was that transducers of different types and shapes would produce different peak and mean ascending aortic (AAo) velocities. Additionally, we sought to determine if mean and peak velocity recorded from the descending aorta (DAo) were similar to velocities in the AAo. Twenty-eight consecutive individuals who had normal hearts were studied. AAo velocities were measured with four transducers including a nonimaging device that transmitted Doppler at right angles to the transducer handle, a 30-degree angled continuous wave transducer, an imaging transducer that transmitted Doppler in line with the transducer handle, and a second imaging transducer that sectored at 25 degrees to the transducer handle. DAo was studied with a standard in-line imaging transducer. Results showed that mean and peak AAo velocities recorded by transducers that transmitted off the axis of the transducer handle were similar, but the transducer that imaged along the transducer handle axis produced significantly lower peak and mean velocities. The problem that caused lower velocity for the on-axis transducer was inability to image the area immediately posterior to the sternum to permit alignment in the azimuthal dimension. The continuous wave transducer provided a wide spectral dispersion. Mean DAo velocity was similar to mean AAo velocity, but variability was large.

Doppler echocardiographic observations of pulmonary and transvalvular velocity changes after birth and during the early neonatal period

To evaluate the qualitative and quantitative changes in Doppler velocities in the normal fetus and newborn, 61 echo Doppler studies were performed in 18 neonates, nine of whom were also studied as fetuses. Four studies were inadequate in fetuses (one pulmonary artery, two mitral, and one tricuspid) and some post natal studies were inadequate due to inability to separate atrioventricular valve E and A velocity component waveforms (one tricuspid, three mitral). Heart rates for fetuses and newborns more than 24 hours of age and less than 24 hours of age were similar. Pulmonary artery diastolic velocities consistent with patent ductus arteriosus were present in 11 of 12 examinations at less than 6 hours of age, in 5 of 13 examined at 6 to 24 hours of age, and in 2 of 27 examined after 24 hours of age. Pulmonary artery times to peak velocity were similar in fetuses, m = 46, SD = 3 msec, and in neonates less than 6 hours of age, m = 51, SD = 13 msec, but lengthened significantly, p less than 0.05, at 6 to 24 hours (m = 69, SD = 14 msec). These changes are probably due to the dramatic changes in pulmonary vascular pressure that occur after birth. Data from 6 to 24 hours and greater than 24 hours (m = 78, SD = 13 msec) were similar. Significant differences existed for transmitral valve E/A ratios, which increased from m = 0.85 in utero to m = 1.17 (p less than 0.05) after birth, with no significant change thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation of Still's murmur, small aortic diameter and high aortic velocity

The origin of Still's innocent murmur, first described in 1909, is obscure. Seventy normal children and young adults, 29 with Still's murmur and 41 with no murmur, were studied. Pulsed Doppler and 2-dimensional echocardiography were used to evaluate possible causes, including tricuspid regurgitation, left ventricular bands, ascending and descending aortic and pulmonary velocities, ascending aortic diameter, and magnitude of spectral widths. Mean ascending aortic diameter relative to body surface area was significantly smaller for the group with Still's murmur (p less than 0.001). Since cardiac output was similar for the 2 groups, the average peak ascending velocity (133 cm/s) and average peak descending aortic velocity (118 cm/s) were significantly higher in the innocent murmur group as compared to similar respective means in the control group without the murmur (107 and 104 cm/s, respectively) (p less than 0.001 and p less than 0.01, respectively). No significant differences were found when the 2 groups were compared with respect to mean peak pulmonary artery velocity adjusted for body size, spectral widths in the ascending and descending aorta and in the pulmonary artery, and the presence of tricuspid regurgitation or ventricular bands. These observations suggest that the origin of Still's murmur is related to a small ascending aortic diameter with concomitant high aortic blood flow velocity.

Accuracy and pitfalls of Doppler evaluation of the pressure gradient in aortic coarctation

Although the pressure gradient in aortic coarctation can usually be obtained by comparison of upper and lower limb blood pressures measured by sphygmomanometry, some patients may have upper or lower limb arterial compromise as a result of prior procedures or anomalous origin of the subclavian arteries, either of which may preclude accurate gradient measurement. To determine whether Doppler echocardiography could predict the pressure gradient, the Doppler method was used to predict transcoarctation gradients in 35 studies and the data were compared with the gradients measured at catheterization. Jet velocities were not adequately obtained by Doppler recording in three neonates with coarctation and patent ductus arteriosus, leaving 32 studies for analysis. The mean age of the study patients was 6 +/- 5.8 years. The mean Doppler-estimated gradient, calculated using only jet velocities distal to the obstruction (V2) in the modified Bernoulli equation, was 44 +/- 17 mm Hg, and the mean catheterization gradient was 36 +/- 21 mm Hg (p = NS; r = 0.91, SEE = 7.0 mm Hg; slope = 0.75, y = 17.3 mm Hg). The mean Doppler-estimated gradient using both the pre- and postcoarctation velocities (V1 and V2) in the modified Bernoulli equation (n = 26) was 36 +/- 20 mm Hg, and the mean catheterization gradient was 36 +/- 21 mm Hg (p = NS; r = 0.98, SEE = 4.2 mm Hg; slope = 0.91, y = 2.8 mm Hg). Doppler echocardiography closely estimated the pressure gradient in aortic coarctation, and estimation of the gradient improved when the velocities proximal as well as distal to the obstruction were included in the modified Bernoulli equation.

Can the technique for Doppler estimate of pulmonary stenosis gradient be simplified?

Although Doppler echocardiography has been demonstrated to accurately predict the pressure drop across the pulmonary valve in patients with pulmonary valve stenosis, prior reports have stressed the need to correct for beam-flow intercept angles, to use simultaneous imaging, and to utilize the subcostal approach. The purpose of this study was to determine the accuracy of estimating the pressure drop in pulmonary stenosis patients by means of nonimaging Doppler applied without angle correction from precordial examination. Pressure drop estimated by Doppler was compared to that measured by strain gauge manometry at catheterization. Data for 39 patients (21 simultaneous measurements; 18 nonsimultaneous) were evaluated. Results for the entire group showed a good correlation (r = 0.94; SEE = 7.9 mm Hg). The correlation for simultaneous measurement improved somewhat (r = 0.95; SEE = 5.9), but the difference was not significant. Comparison of the slope and intercept of data of this study to those of prior studies, which advocated more complex methodology, indicated that results were essentially similar and that use of the additional steps did not confer a significantly improved result. We conclude that the simplified methodology utilized in this study provides accurate Doppler estimates of pressure gradient in patients with pulmonary stenosis.

Hemodynamic responses of the acutely stressed neonatal right ventricle: a maturational study in lambs

Right ventricular Starling responses to acute volume infusion in newborn lambs were compared to those in older groups of lambs. When peak stroke volume/kg was reached during infusion, right ventricular end-diastolic pressures for the newborn group were significantly lower (p less than 0.001) than those obtained for older groups, in spite of significantly higher resting and peak stroke volumes in the two younger groups. Newborn lambs developed tricuspid regurgitation and right-to-left foraminal shunting, demonstrated by echocardiography, at a mean end-diastolic pressure of 7.5 mm Hg. No right-to-left shunting was noted in older lambs. This study demonstrated a blunted Starling response in the newborn lamb's right ventricle. The response to volume loading improved with maturation, but was still less than that reported for the left ventricle. Clinical implications regarding right ventricular immaturity and inadequate response to altered hemodynamic situations are raised.

Doppler echocardiographic estimation of systolic pulmonary artery pressure in patients with aortic-pulmonary shunts

The objective of this study was to determine if the pressure drop across various types of aortic-pulmonary shunts could be accurately estimated by Doppler echocardiography, and if systolic pulmonary pressure could be estimated by referencing the pressure drop across the aortic-pulmonary shunt to systolic systemic arterial pressure measured by cuff sphygmomanometry. This was done in 22 patients and Doppler results were compared with pulmonary artery pressure measured directly by strain gauge manometry. Adequate Doppler waveforms were obtained in 21 of 22 patients; 3 had a Waterston shunt, 10 had a Blalock-Taussig shunt, 1 had a left pulmonary artery-aortic anastomosis, 6 had a patent ductus arteriosus and 1 had an aortic-pulmonary window. Systolic pulmonary artery pressure estimated by Doppler echocardiography ranged from 12 to 90 mm Hg (mean 41.3 +/- 21.4 [SD] ), and measured by strain gauge manometry ranged from 20 to 90 mm Hg (mean 44.7 +/- 20.7) (p = NS, r = 0.94, SEE = 7.4 mm Hg; slope = 0.90, y intercept = 7.4 mm Hg). Systolic pulmonary artery to aortic pressure ratios predicted by Doppler recording ranged from 0.1 to 1.0 (mean 0.4 +/- 0.2 [SD] ); when calculated from direct measurement it ranged from 0.2 to 1.0 (mean 0.4 +/- 0.2) (p = NS, r = 0.92; SEE = 0.08, slope = 0.80, y intercept = 0.09). This study demonstrates that Doppler echocardiography provides an estimation of pressure drop across aortic-pulmonary shunts, and that the data can be used to estimate systolic pulmonary artery pressure by subtracting the estimated pressure drop from the systolic systemic arterial pressure.

Balloon dilation angioplasty for coarctation of the aorta

Eleven patients with coarctation of the aorta (C of A) underwent balloon dilation angioplasty at the University of Arizona from November 1983 to January 1985. Eight had previously undergone surgery and 3 had native C of A. Two operations were considered unsuccessful: 1 in a patient who underwent tube graft--descending aortic anastomosis narrowing and 1 in a patient with a native wedge type of C of A. Overall mean gradient fell from 47 to 13 mm Hg immediately after the procedure. Mean gradient at repeat catheterization in 7 patients (mean 8 months after angioplasty) was 6 mm Hg. Five patients showed a transient increase in the gradient measured on the day after angioplasty, with 3 showing a fairly marked increase. Values returned to levels equal to or less than gradients measured immediately after the procedure. Angiographic findings at follow-up catheterization in 7 patients showed no evidence of aneurysm formation in either the operative group or in the 2 patients with native C of A who had a membrane type of deformity. Mean C of A to ascending aortic diameter ratios increased from 0.44 to 0.80. At repeat angiography, the mean ratio was 0.76 in the 7 patients studied. Further longitudinal studies in these patients are necessary before reaching conclusions about the advantage of this procedure over surgery, but these early longitudinal results are encouraging for the populations studied: postoperative patients and patients with native membrane types of C of A.

Maturational changes in myocardial pump performance in newborn lambs

We examined the left ventricular stroke volume response to fluid loading in 24 acutely instrumented newborn lambs and the right ventricular response in 12 lambs. Newborn lambs (group 1, ages 2 to 4 days) demonstrated a limited response to acute volume loading for both left and right ventricles. With maturation, the left ventricle exhibited a progressively greater ability to respond to acute volume loading, with greater peak stroke volumes achieved at higher end-diastolic pressures. The response of the right ventricle remained limited at all ages examined, with peak stroke volume achieved at lower end-diastolic pressures. We conclude that postnatal maturation of the left ventricle results in a progressively greater stroke volume response in older lambs, while the response of the right ventricle remains limited.

Ruptured mitral chordae tendineae may be a frequent and insignificant complication in the mitral valve prolapse syndrome

In this study, we performed 512 echocardiographic studies on 264 consecutive unselected patients with the idiopathic mitral valve prolapse syndrome. Twenty-eight patients (10.6%) had evidence of ruptured chordae tendineae of the mitral valve on M-mode examination and in 24 the diagnosis was confirmed by two-dimensional echocardiography. Mild to severe mitral insufficiency was proven in all of them by left ventriculography during cardiac catheterization. Eight patients underwent surgery to relieve symptomatic severe mitral regurgitation. At operation all had myxomatous degeneration of the mitral valve, two patients were found to have rupture of anterior mitral chordae, and six had rupture of posterior mitral chordae. Twenty (71%) patients with chordal rupture had either mild symptoms or were completely asymptomatic. It is concluded that chordal rupture in patients with the mitral valve prolapse syndrome may be present in asymptomatic patients and go undetected clinically in a substantial number of patients unless a high index of suspicion is maintained. Serial M-mode and two-dimensional echocardiographic studies are of importance in identifying the progression of prolapse findings and may reveal the natural history of this pathologic condition in asymptomatic patients.

Doppler echocardiographic estimation of systolic pulmonary artery pressure in pediatric patients with interventricular communications

The purpose of this study was to evaluate a noninvasive method for estimation of pulmonary artery pressures in infants and children with interventricular communications. Systolic pulmonary artery pressures measured by cardiac catheterization were compared with those estimated by Doppler echocardiography. Pressure drops were measured by Doppler study (modified Bernoulli equation) and were referenced to systolic systemic arterial pressure measured by sphygmomanometry. All 25 patients in this study had either a ventricular septal defect or a single ventricle. The systolic pulmonary artery pressure measured by cardiac catheterization ranged from 15 to 100 mm Hg (mean +/- SD 44 +/- 26) and that measured by Doppler echocardiography ranged from 5 to 100 mm Hg (mean 43 +/- 26) (p = NS; r = 0.92; SEE = 9.9; slope = 0.92; y intercept = 4.7). Systolic pulmonary artery to aortic pressure ratio measured by cardiac catheterization ranged from 0.2 to 1.0 (mean 0.5 +/- 0.3) and that measured by Doppler echocardiography ranged from 0.1 to 1.0 (mean 0.5 +/- 0.3) (p = NS; r = 0.94; SEE = 0.09; slope = 0.90; y intercept = 0.04). This study demonstrates that Doppler echocardiography can closely approximate systolic pulmonary artery pressure in patients with interventricular communications.