MR velocity mapping of tricuspid flow in healthy children and in patients who have undergone Mustard or Senning repair.

PURPOSE: To determine the feasibility and accuracy of measuring tricuspid volume flow with magnetic resonance (MR) velocity mapping in healthy children and in patients after a Mustard or Senning repair. MATERIALS AND METHODS: MR studies were performed in 14 healthy children (mean age, 12 years +/- 3) and in 12 patients (mean age, 17 years +/- 5) late after a Mustard or Senning repair. MR measurements of tricuspid volume flow were validated against right ventricular stroke volumes measured tomographically. Diastolic filling parameters were derived from the flow measurements. RESULTS: Tricuspid volume flow and right ventricular stroke volume showed close agreement in the healthy children (r = .98) and in the patients (r = .94). Children after Senning repair, compared with healthy children, showed a delayed and higher peak tricuspid flow rate during early filling and a lower peak flow rate during atrial contraction (P < .05). CONCLUSION: MR measurement of tricuspid flow is feasible and accurate in healthy children and in patients after a Mustard or Senning operation, who often demonstrate abnormal tricuspid flow patterns.

Long-term results of atrial correction for transposition of the great arteries. Comparison of Mustard and Senning operations.

Few data exists on the differences in long-term outcome between Mustard and Senning operations. We reviewed available data of all hospital survivors of these operations and assessed risk factors for late death and sinus node dysfunction. Of those patients undergoing the Mustard operation, 60 were hospital survivors (46 simple transposition, 14 complex); of those patients undergoing the Senning operation, 62 were hospital survivors (43 simple, 19 complex). Median duration of follow-up was 16 years (maximum 25 years) for Mustard operation, 11 years (maximum 20 years) for Senning operation. No reoperations were done, except for pacemaker implantation. No differences were found between the two groups with regard to baffle-associated problems, right ventricular failure, sudden death (6% in both groups), and functional status at final follow-up (New York Heart Association class I or II, except for four patients). For patients undergoing the Mustard operation, survival at 16-year follow-up was 91% with simple transposition and 60% with complex transposition (p = 0.027); for both groups of patients undergoing the Senning operation, survival at 16-year follow-up was 78%. Survival in the absence of rhythm disturbance at 16-year follow-up was 18% for Mustard operation and 53% for Senning operation (p < 0.001). In multivariate analysis, significant independent risk factors for late death turned out to be complex transposition (versus simple) and active arrhythmias. The only significant risk factor for the occurrence of sinus node dysfunction was the Mustard operation. We conclude that apart from the difference in the loss of sinus rhythm, no differences were found in the long-term clinical results of the two types of operations.

Pulmonary regurgitation in the late postoperative follow-up of tetralogy of Fallot. Volumetric quantitation by nuclear magnetic resonance velocity mapping.

BACKGROUND: Pulmonary regurgitation frequently occurs after surgical correction of tetralogy of Fallot. To date, reliable quantitation of pulmonary regurgitation has not been possible, and therefore the clinical significance of pulmonary regurgitation is controversial. Nuclear magnetic resonance (NMR) velocity mapping allows accurate measurement of volumetric flow. The feasibility and accuracy of NMR velocity mapping to quantify pulmonary regurgitation volumes are studied in patients after Fallot repair. METHODS AND RESULTS: In 18 patients (mean age, 16.5 +/- 6.5 years), late (12.6 +/- 5.2 years) after Fallot surgery, forward and regurgitant volume flow was measured in the main pulmonary artery with NMR velocity mapping. To validate the measurements of pulmonary forward flow, right ventricular stroke volume was used as an internal reference standard. Pulmonary regurgitation volumes were compared with the differences between the corresponding right and left ventricular stroke volumes. Ventricular volumes were measured with a multisection gradient echo NMR method. In addition, the relation between pulmonary regurgitation and right ventricular volumes was studied. Measurements of pulmonary regurgitation volume with NMR velocity mapping closely corresponded with the tomographically determined volumes (r = .93). Forward pulmonary volume flow was nearly identical to right ventricular stroke volume (r = .98). Pulmonary regurgitation volume was significantly correlated with end-diastolic volume (r = .82, P < .0005), end-systolic volume (r = .63, P < .01), and stroke volume (r = .89, P < .0005) of the right ventricular but not with right ventricular ejection fraction (r = .41, P = NS). CONCLUSIONS: NMR velocity mapping is an accurate method for the noninvasive, volumetric quantification of pulmonary regurgitation after surgical correction of tetralogy of Fallot.

Postoperative pulmonary flow dynamics after Fontan surgery: assessment with nuclear magnetic resonance velocity mapping.

OBJECTIVES: This study was performed to assess the value of nuclear magnetic resonance (NMR) velocity mapping for the measurement of pulmonary blood flow after Fontan surgery. BACKGROUND: Echocardiographic studies of pulmonary flow after Fontan surgery are not always satisfactory. The newly developed technique of NMR velocity mapping may contribute to the elucidation of the Fontan circulation. METHODS: At frequent intervals during the cardiac cycle, forward and backward flow volumes in the pulmonary arteries of nine volunteers were measured, summed and compared with right ventricular stroke volume to validate the velocity mapping technique. In 14 patients after Fontan surgery, assessment of pulmonary flow volumes enabled the evaluation of atriopulmonary and atrioventricular (AV) Fontan connections. The findings were correlated with precordial echocardiography. RESULTS: Validation of the NMR technique, obtained from volunteer experiments, showed a high correlation (r = 0.97) between right ventricular stroke volume and volumetric pulmonary stroke flow. In all patients with an atriopulmonary Fontan connection (n = 8), forward flow in the pulmonary artery was biphasic, similar to normal venous flow. Monophasic systolic pulmonary flow curves indicating right ventricle-dependent pulmonary blood flow were found in three of six patients with an AV Fontan connection. In the remaining three patients, the pulmonary flow pattern did not reflect right ventricular contraction. Measurement of flow velocity alone may give a false impression of forward flow and thus of right ventricular contribution. Pulmonary regurgitation was demonstrated in six of eight patients with an atriopulmonary connection. CONCLUSIONS: Nuclear magnetic resonance velocity mapping provides accurate and valuable information on pulmonary flow volume and velocity after Fontan surgery. The success of AV Fontan surgery can be deduced from the presence of a monophasic systolic pulmonary flow pattern as demonstrated by NMR velocity mapping. With NMR flow volume analysis, substantial pulmonary regurgitation occurring after atriopulmonary Fontan surgery can be measured.

Levotransposition of the aorta: identification of segmental cardiac anatomy using MR imaging.

Several reports have shown that high-quality magnetic resonance (MR) images can be obtained in patients with congenital heart disease. However, little attention has been paid to the segmental analysis of cardiac MR images. The authors believe that this approach is essential in the evaluation of complex congenital cardiac abnormalities. The segmental approach is based on the morphologic identification of the different cardiac compartments and the type of connection among these compartments. The authors applied the basic principles of the segmental approach to the interpretation of MR images obtained in a group of patients with levotransposition of the aorta. Results indicate that this logical step-by-step method can be used to advantage in the accurate analysis of MR images obtained in patients with complex congenital cardiac disease. In this report, the authors discuss the results obtained when the segmental approach is used to interpret cardiac MR images.

Radionuclide angiocardiography in the clinical evaluation of cardiac malpositions in situs solitus in adults.

A right-sided position of the heart in the chest in situs solitus is an abnormal feature easily discernible from a plain chest radiograph. This cardiac malposition may be due to cardiac displacement (dextroposition), which is usually a feature of lung disease, or a structural abnormality of the heart (dextrocardia). Because each condition has different clinical pathologic implications, it is important to distinguish them. Chest films, however, often provide no conclusive information. We performed radionuclide angiocardiography (RNA) in six adults with a cardiac malposition in situs solitus. It was found that morphologic data obtained from the serial images may distinguish dextroposition from dextrocardia. In addition, these images permitted us to diagnose congenitally corrected transposition, a cardiac anomaly which occurs with increased frequency in situs solitus with dextrocardia. Quantitative shunt detection performed during this procedure is helpful in the differential diagnosis of dextroposition and able to distinguish uncomplicated dextrocardia from dextrocardia associated with other cardiac abnormalities. RNA therefore is a valuable and easily performed method in the analysis of cardiac malpositions in adults.

Technical aspects and clinical results of an esophageal pick-up for better recording of posteriorly generated heart sounds.

A miniature esophageal microphone has been constructed. It has a cylindrical shape with 5-mm outer diameter and 25-mm length. It is a type of accelerometer that detects vibration from the esophageal wall. It has a resonance frequency of 2.1 kHz and an acceleration charge sensitivity of 2.8 pCm-1s2. The upper limit of the useful frequency range is about 1 kHz. It has directional sensitivity which reaches a maximum perpendicular to the plane of the crystal. With the esophageal microphone cardiovascular sound is recorded simultaneously with other tracings: external phonocardiogram, E.C.G., carotid pulse and M-mode echocardiogram. The great advantage of the application of the esophageal microphone is that it can be positioned in the esophagus close to the mitral valve and the left atrium by use of fluoroscopy, so that sounds and murmurs originating from that part of the heart are recorded in detail. In a case of a shunt between aorta and pulmonary artery the microphone was used at different levels in the esophagus, showing different amplitudes of a continuous murmur. In all other cases the probe was situated in the esophagus just above the level of the mitral valve behind the left atrium. In 2 cases the advantage of the esophageal microphone (revealing signs of slight mitral incompetence) over the body surface microphone is shown. In 3 patients with artificial valves in the aortic and mitral orifices (where left heart catheterisation and left ventricular angiography is a considerable risk), the esophageal microphone also improved the postoperative evaluation and diagnosis of mitral valve regurgitation considerably.

Congenitally corrected transposition in the adult: detection by radionuclide angiocardiography.

Congenitally corrected transposition (CCT) of the great vessels is an uncommon anomaly usually detected in children because of associated severe cardiac malformations. When these are absent, patients may be hemodynamically normal, but associated cardiac abnormalities are usually present in CCT, leading to symptoms in adulthood. When CCT is suggested in an adult, diagnosis by means of ultrasound may be difficult. Radionuclide angiocardiography (RA) is a simple, noninvasive method by which to diagnose CCT. We found consistent morphologic scintigraphic results in 13 patients with proved CCT, leading to establishment of reliable diagnostic criteria. In all instances of situs solitus the aorta ascends and descends on the left with vertical orientation. In the case of situs inversus, the aorta ascends and descends on the right with vertical orientation. Our criteria are independent of the situs and cardiac position, unlike earlier reports by others. We believe images obtained in the anterior projection are sufficient for the study. The practical application of RA study in patient diagnosis is demonstrated, giving special attention to patients referred because of situs solitus and dextrocardia, in which CCT is known to be present in 50% of cases.

Congenitally corrected transposition in adults with left atrioventricular valve incompetence.

Congenitally corrected transposition of the great vessels (CCT) is usually detected in childhood owing to the presence of associated cardiac malformations. If such malformations are absent, the patient may remain asymptomatic until adulthood; such persons usually present with left atrioventricular valve incompetence and conduction disturbances. The chest radiograph may be the first clue to the diagnosis, demonstrating the typical cardiovascular silhouette produced by the convex left ascending aorta. The authors examined seven cases of CCT manifested in adulthood and found that in four of them the diagnosis was not apparent from the plain image because the ascending aorta instead followed a concave course. Hallmarks of this phenomenon are discussed, and two radiological signs are presented: the double mediastinal stripe and the straight left lower cardiac border.

Calcium ions and the regulation of NAD+-linked isocitrate dehydrogenase from the mitochondria of rat heart and other tissues.

The effects of Ca2+ on the activity of isocitrate dehydrogenase (NAD+) in extracts of rat heart mitochondria were explored in the presence of MgCl2 by using EGTA buffers. In the absence of ADP, Ca2+ (about 30 micrometer) resulted in a slight increase in apparent Km for threo-Ds-isocitrate; in the presence of ADP, Ca2+ (about 25 micrometer) greatly lowered the apparent Km for threo-Ds-isocitrate from 227 micrometer to 53 micrometer without changing the maximum velocity. At 100 micrometer-threo-Ds-isocitrate and 1 mM-ADP, there was an 8-fold activation by Ca2+, with a Km for Ca2+ of 1.2 micrometer. This activation was also observed with Sr2+ (Km 3.1 micrometer), but not with Mn2+ (at concentrations below 2.5 micrometer). Similar effects of Ca2+ were also observed on isocitrate dehydrogenase (NAD+) activity in extracts of mitochondria from liver, kidney, brown adipose tissue and white adipose tissue of the rat. The possible regulatory role of changes in the intramitochondrial concentration of Ca2+ is discussed.