Diagnosis of pulmonary arteriovenous fistula by contrast echocardiography

Paradoxical Embolism in Juveniles and Young Adults With Severe-to-Profound Sudden Sensorineural Hearing Loss

Objective: Paradoxical embolism from right-to-left shunting is a common cause of cryptogenic stroke in the young. Circulatory ischemia of the cochlea is closely connected with severe-to-profound sudden sensorineural hearing loss. This study aimed to explore the role of paradoxical embolism in severe-to-profound sudden sensorineural hearing loss in juveniles and young adults. Methods: From August 2021 to September 2022, consecutive outpatients under 35 years of age with severe-to-profound sudden hearing loss were included in the study. Routine auditory electrophysiological testing and contrast transcranial Doppler ultrasonography (c-TCD) were conducted, and the results were retrospectively analyzed. Results: Seven patients (age: 19.4 ± 6.5 years) were enrolled, including 5 juveniles and 2 young adults. Three patients had severe deafness, and 4 patients had profound deafness. Right-to-left shunting was detected in all patients through c-TCD. Patent foramen ovale was found in 2 patients while pulmonary arteriovenous fistula was found in 1 patient through contrast transthoracic echocardiography or cardiac catheterization. No patients had precipitating factors for sudden sensorineural hearing loss, and none had abnormalities on head magnetic resonance imaging. Six patients underwent whole-exome sequencing, and no known deafness gene variant was detected. After standard treatment for 1 month, 2, 3, and 2 patients had complete, slight, and no hearing recovery, respectively. Conclusions: Paradoxical embolism is a possible cause of severe-to-profound sudden sensorineural hearing loss in juveniles and young adults. In young patients, c-TCD is an effective screening tool to detect right-to-left shunting, while contrast transthoracic echocardiography is a complementary examination to c-TCD.

A large pulmonary arteriovenous malformation causing cerebrovascular accidents

The incidence of pulmonary arteriovenous malformations (PAVMs) is 2.5 in 100,000. 80% are associated with Osler-Weber-Rendu syndrome or hereditary haemorrhagic telangiectasia. We report the case of a 70-year-old man with a 6 cm spherical mass incidentally found on chest X-ray. There was a localised systolic bruit over the right lower zone posteriorly; however, he was asymptomatic. He had suffered a stroke, affecting his right hand and his speech, from which he recovered. He experienced regular transient ischaemic attacks, on an average of every 2 months. He underwent a right lower lobectomy and on ligating the right lower lobe pulmonary artery the saturations of oxygen rose from 92% to 97%, demonstrating a significant right to left extracardiac shunt. Postoperative recovery was excellent and 1 year later the patient reports no further neurological symptoms. 40% of such lesions exhibit symptoms, however, only one-third are neurological. Treatment should be by percutaneous embolisation.

Effect of a patent foramen ovale on pulmonary gas exchange efficiency at rest and during exercise

The prevalence of a patent foramen ovale (PFO) is ~30%, and this source of right-to-left shunt could result in greater pulmonary gas exchange impairment at rest and during exercise. The aim of this work was to determine if individuals with an asymptomatic PFO (PFO+) have greater pulmonary gas exchange inefficiency at rest and during exercise than subjects without a PFO (PFO-). Separated by 1 h of rest, 8 PFO+ and 8 PFO- subjects performed two incremental cycle ergometer exercise tests to voluntary exhaustion while breathing either room air or hypoxic gas [fraction of inspired O(2) (FI(O(2))) = 0.12]. Using echocardiography, we detected small, intermittent boluses of saline contrast bubbles entering directly into the left atrium within 3 heart beats at rest and during both exercise conditions in PFO+. These findings suggest a qualitatively small intracardiac shunt at rest and during exercise in PFO+. The alveolar-to-arterial oxygen difference (AaDo(2)) was significantly (P < 0.05) different between PFO+ and PFO- in normoxia (5.9 ± 5.1 vs. 0.5 ± 3.5 mmHg) and hypoxia (10.1 ± 5.9 vs. 4.1 ± 3.1 mmHg) at rest, but not during exercise. However, arterial oxygen saturation was significantly different between PFO+ and PFO- at peak exercise in normoxia (94.3 ± 0.9 vs. 95.8 ± 1.0%) as a result of a significant difference in esophageal temperature (38.4 ± 0.3 vs. 38.0 ± 0.3°C). An asymptomatic PFO contributes to pulmonary gas exchange inefficiency at rest but not during exercise in healthy humans and therefore does not explain intersubject variability in the AaDO(2) at maximal exercise.

Intrapulmonary shunting and pulmonary gas exchange during normoxic and hypoxic exercise in healthy humans

Exercise-induced intrapulmonary arteriovenous shunting, as detected by saline contrast echocardiography, has been demonstrated in healthy humans. We have previously suggested that increases in both pulmonary pressures and blood flow associated with exercise are responsible for opening these intrapulmonary arteriovenous pathways. In the present study, we hypothesized that, although cardiac output and pulmonary pressures would be higher in hypoxia, the potent pulmonary vasoconstrictor effect of hypoxia would actually attenuate exercise-induced intrapulmonary shunting. Using saline contrast echocardiography, we examined nine healthy men during incremental (65 W + 30 W/2 min) cycle exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 0.12). Contrast injections were made into a peripheral vein at rest and during exercise and recovery (3–5 min postexercise) with pulmonary gas exchange measured simultaneously. At rest, no subject demonstrated intrapulmonary shunting in normoxia [arterial Po2 (PaO2) = 98 ± 10 Torr], whereas in hypoxia (PaO2 = 47 ± 5 Torr), intrapulmonary shunting developed in 3/9 subjects. During exercise, ∼90% (8/9) of the subjects shunted during normoxia, whereas all subjects shunted during hypoxia. Four of the nine subjects shunted at a lower workload in hypoxia. Furthermore, all subjects continued to shunt at 3 min, and five subjects shunted at 5 min postexercise in hypoxia. Hypoxia has acute effects by inducing intrapulmonary arteriovenous shunt pathways at rest and during exercise and has long-term effects by maintaining patency of these vessels during recovery. Whether oxygen tension specifically regulates these novel pathways or opens them indirectly via effects on the conventional pulmonary vasculature remains unclear.

Left atrial volume: a novel predictor of hepatopulmonary syndrome

OBJECTIVES

We studied patients with hepato-pulmonary syndrome (HPS). We found that HPS is frequently present in patients with left atrial enlargement. The aim of this prospective study was to evaluate the possible correlation between left atrial volume and HPS.

METHODS

Adult patients (>18 yr old) with biopsy proven liver cirrhosis who were referred for liver transplantation were enrolled in the study. Diagnosis of HPS was established when the following points were fulfilled: (a) the presence of chronic liver disease, (b) increased alveolar-arterial difference (AaDO(2)), (c) intrapulmonary vascular dilatation, and (d) absence of primary cardiac or pulmonary disease.

RESULTS

We enrolled 41 patients (mean age 47.1 +/- 10.6 yr) diagnosed with HPS. Also 108 Child-Pugh score matched cirrhotic patients (mean age 49.2 +/- 9.3 yr) who have negative contrast echocardiography and normal age-related AaDO(2) were selected as a control group for the purpose of comparison of left atrial volume (LAV). LAV was significantly greater in patients with HPS compared to the control group (55.1 +/- 7.5 mL vs 37.1 +/- 9.3 mL, P < 0.05). The area under the receiver-operating characteristic (ROC) curve for LAV was 0.903 (Cut point >/= 50 mL, sensitivity 86.3%, specificity 81.2%).

CONCLUSION

In the context of liver cirrhosis, LAV >/= 50 mL is a simple and feasible parameter to detect HPS.

Intrapulmonary shunt during normoxic and hypoxic exercise in healthy humans

This review presents evidence for the recruitment of intrapulmonary arteriovenous shunts (IPAVS) during exercise in normal healthy humans. Support for pre-capillary connections between the arterial and venous circulation in lungs of humans and animals have existed for over one-hundred years. Right-to-left physiological shunt has not been detected during exercise with gas exchange-dependent techniques. However, fundamental assumptions of these techniques may not allow for measurement of a small (1-3%) anatomical shunt, the magnitude of which would explain the entire A-aDO2 typically observed during normoxic exercise. Data from contrast echocardiograph studies are presented demonstrating the development of IPAVS with exercise in 90% of subjects tested. Technetium-99m labeled macroaggregated albumin studies also found exercise IPAVS and calculated shunt to be approximately 2% at max exercise. These exercise IPAVS appear strongly related to the alveolar to arterial PO2 difference, pulmonary blood flow and mean pulmonary artery pressure. Hypoxic exercise was found to induce IPAVS at lower workloads than during normoxic exercise in 50% of subjects, while all subjects continued to shunt during recovery from hypoxic exercise, but only three subjects demonstrated intrapulmonary shunt during recovery from normoxic exercise. We suggest that these previously under-appreciated intrapulmonary arteriovenous shunts develop during exercise, contributing to the impairment in gas exchange typically observed with exercise. Future work will better define the conditions for shunt recruitment as well as their physiologic consequence.

Pulmonary nodular opacities in children with hereditary hemorrhagic telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a rare inherited disorder of vascular endothelium that can result in the formation of pulmonary arteriovenous malformations (pAVMs). We observed that small pulmonary nodules, possibly representing early vascular malformations, are more common in these children than in the general population.

OBJECTIVE

To describe and characterize the small pulmonary nodules seen on chest CT examination in the lungs of children with HHT.

MATERIALS AND METHODS

We followed 19 children who had undergone chest CT as part of their initial diagnostic evaluation in the HHT clinic of a pediatric hospital. Chest CT scans were reviewed independently by two radiologists blinded to clinical data. Pulmonary nodules were analyzed according to lobar distribution, anatomic position in the lung (outer, mid, inner third), shape (round, linear, V- or Y-shaped, ill-defined), presence of overt AVMs, and nodule size (<or= or >5 mm). We also reviewed a control group of chest CT scans performed on 25 age-matched children.

RESULTS

A total of 35 pulmonary nodules were identified on the CT scans in 15 of the 19 children. Multiple nodules were seen in eight children (42%), solitary nodules were seen in seven children (37%) and no nodules were seen in the remaining four children (21%). The nodules were found to be nonspecific with regard to multiple factors other than their anatomic position within the lung. The chest CT scans of 2 of the 25 age-matched controls revealed a total of only four nodules, a significantly lower total (P = 0.0001 vs. children with HHT).

CONCLUSION

Nonspecific nodules are commonly seen in children with HHT.

Exercise-induced intrapulmonary arteriovenous shunting in healthy humans

We hypothesized that increasing exercise intensity recruits dormant arteriovenous intrapulmonary shunts, which may contribute to the widened alveolar-arterial oxygen difference seen with exercise. Twenty-three healthy volunteers (13 men and 10 women, aged 23-48 yr) with normal lung function and a wide range of fitness (mean maximal oxygen uptake = 126% predicted; range = 78-200% predicted) were studied by agitated saline contrast echocardiography (4-chamber apical view). All 23 subjects had normal resting contrast echocardiograms without evidence of intracardiac or intrapulmonary shunting. However, with cycle ergometer exercise, 21 of 23 (91%) of the subjects showed a delayed (>3 cardiac cycles) appearance of contrast bubbles in the left heart. This pattern is consistent with passage of contrast bubbles through the pulmonary circulation. Because the contrast bubbles are known to be significantly larger than pulmonary capillaries, we propose that they are traveling through direct arteriovenous intrapulmonary shunts. In all cases, the intrapulmonary shunting developed at submaximal oxygen uptakes [%maximal oxygen uptake = 59 +/- 20 (SD)] and once evident persisted at all subsequent work rates. Within 3 min of exercise termination, the contrast echocardiograms with bubble injection showed no evidence of intrapulmonary shunting. These dynamic shunts will contribute significantly to the widened alveolar-arterial oxygen difference seen with exercise. They may also act as a protective parallel vascular network limiting the rise in regional pulmonary vascular pressure while preserving cardiac output during exercise.

Pulmonary arteriovenous malformations: screening procedures and pulmonary angiography in patients with hereditary hemorrhagic telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is a dominantly inherited disease with a high prevalence of pulmonary arteriovenous malformations (PAVMs). The first symptom of HHT may be stroke or fatal hemoptysis associated with the presence of PAVM.

OBJECTIVE

To evaluate different screening methods applied for the identification of PAVMs.

SETTING

Odense University Hospital.

SUBJECTS

HHT patients with positive findings on contrast echocardiography (CE) who participated in a screening investigation and underwent pulmonary angiography (PA).

METHODS

Different screening methods were evaluated against the results of PA. In a group of patients with positive findings on CE, we compared results of PA with the following: severity of dyspnea; results of pulse oximetry arterial oxygen saturation (SaO2) supine and upright; supine PaO2 in room air and while breathing 100% oxygen; size of arteriovenous shunt in supine position; chest radiograph; and intensity of contrast at CE.

RESULTS

PA was performed in 25 HHT patients with positive findings on CE, 15 of whom had PAVM. Embolization therapy was recommended in 12 patients, and 3 patients had small PAVMs not accessible for therapy. In 10 patients, PAVM could not be demonstrated at PA. The sensitivity and specificity calculated for the screening procedures are as follows: 53% and 90%, respectively, for SaO2; 60% and 100%, respectively, for chest radiograph; 73% and 80%, respectively, for PaO2 in room air; 100% and 40%, respectively, for PaO2 breathing 100% oxygen; and 64% and 80%, respectively, for shunt measurement.

CONCLUSION

Initial screening with CE followed by measurement of PaO2 while breathing 100% oxygen seemed to be the best screening procedure for identification of patients with PAVM. Screening with chest radiograph and pulse oximetry was shown to be insufficient.

Frequency and significance of intrapulmonary right-to-left shunting in end-stage hepatic disease

Intrapulmonary vascular abnormalities consisting of arteriovenous malformations and capillary dilatations have been described in patients with severe liver disease. These intrapulmonary vascular abnormalities can result in intrapulmonary right-to-left shunting and hypoxemia. Twenty-five of 53 patients (47%) with end-stage hepatic disease were found to have contrast echocardiographic evidence of intrapulmonary right-to-left shunting. There was no difference in mean age, gender distribution, or severity of hepatic disease in those with and without evidence of such shunting. Although there was no difference in mean partial arterial oxygen pressure (PaO2) values in the 2 groups (82 +/- 11 vs 76 +/- 11 mm Hg), the mean PaO2 value of those with at least 2+ left ventricular opacification (2 to 4+) was significantly lower (66 +/- 3 mm Hg, n = 8; p less than 0.01). Unexpectedly, patients with evidence of intrapulmonary shunting had a lower mortality rate before transplantation (3 of 25, 12%) than those without evidence of shunting (10 of 28, 36%) resulting in a significant difference in actuarial survival (p less than 0.05) by the end of the follow-up period. It is concluded that intrapulmonary right-to-left shunting occurs frequently in patients with end-stage liver disease and may be a marker of a positive biologic process that, in some way, leads to improved short-term survival.

Contrast Two-Dimensional Echocardiography Provides Clinical Information Not Available with Color Flow Imaging

Contrast two-dimensional (2D) echocardiography using peripheral venous injections of agitated saline provides useful clinical information not available with standard 2D Doppler and color flow imaging techniques. Intraor extracardiac right-to-left shunting in patients with atrial or ventricular septal defects and patent ductus arteriosus can be identified in this manner, and the relative degree of shunt can be assessed. Other conditions, such as left superior vena cava to the coronary sinus or pulmonary arteriovenous malformation, are accurately detected only when contrast 2D echo is incorporated during the noninvasive examination. Recent work has also demonstrated that venous injections of agitated saline can be used to enhance continuous wave Doppler recordings of tricuspid regurgitant jet envelopes when poorly defined, or with color flow imaging to characterize the jet area. Twodimensional visualization of the needle placed in the pericardial sac for drainage of pericardial effusion may be difficult. Injection of agitated saline through the needle may be used to verify proper location in the pericardial sac and not in the ventricular chambers. The role of contrast 2D echocardiography with new agents has been used to assess myocardial perfusion. All of these applications of contrast echo contribute to standard echocardiographic techniques to provide a better characterization of flow dynamics not seen with color flow imaging.

Two-dimensional contrast echocardiography in the detection and follow-up of congenital pulmonary arteriovenous malformations

Pulmonary arteriovenous (A-V) malformation is frequently a manifestation of Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasia). We identified 14 patients (9 men and 5 women) with A-V malformation by contrast echocardiography; 10 patients with atrial right-to-left shunt served as control subjects. Agitated saline solution (10 ml) was injected through a peripheral vein during echocardiographic imaging. The delay in the appearance of microcavitations in the left atrium was measured (in number of frames) after right atrial appearance. The degree of left ventricular opacification was graded 1 to 4+ (where 4+ = intense left ventricular endocardial outline, and 1+ = minimal opacification). Results indicated patients with A-V malformation had a significant delay (p less than 0.001) in left atrial appearance of microcavitations compared with those with atrial right-to-left shunt (66 +/- 27 vs 21 +/- 7 frames, mean +/- 1 standard deviation). In the group with A-V malformation, abnormal blood gases were present in only 6 of 14 patients and chest x-ray was positive in 7. Pulmonary angiography was performed in 11 of 14 patients with positive contrast echocardiography, and all 11 had A-V malformation identified. In patients with 3 to 4+ left ventricular opacification (n = 8), large (greater than 5 mm feeding vessel) or multiple malformations were present, whereas patients with small or isolated malformation had 1 to 2+ left ventricular opacification. Balloon occlusion of malformations was performed in all 11 of these patients; repeat contrast echocardiography revealed significant diminution of right-to-left shunt in 9, and 2 required repeat embolotherapy for an additional previously undetected A-V malformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary arteriovenous fistula: ultrasonographic approach

Report of a pediatric case with pulmonary arteriovenous fistula (PAVF) in hereditary hemorrhagic teleangiectasia (HHT), primary suspected by ultrasound. There is a characteristic sonographic feature of the complex type of PAVF revealing septations in contrast of the simple type. The diagnosis was established by angiography.

Contrast two-dimensional echocardiography in congenital heart disease: techniques, indications and clinical utility

Saline contrast echocardiography was performed in 889 children from June 1976 through February 1988. One-third of these studies were in postoperative patients. A patent foramen ovale was identified by finding right to left shunting on venous contrast injection in 37% of 127 children studied with a structurally normal heart. The incidence of such shunting was greater at younger ages (55% younger than 1 month versus 22% older than 1 month). In most patients with an atrial or ventricular septal defect, some right to left shunting was demonstrable. The technique was useful in distinguishing different forms of atrial septal defect and identifying muscular ventricular septal defects that were difficult to image directly. The technique was used in the catheterization laboratory to aid in the identification of congenital coronary artery fistulas and was diagnostic in two cases of pulmonary arteriovenous malformation. In patients with situs abnormalities, the technique was useful in identifying the systemic venous connections to the atria. Contrast echocardiography was also used in postoperative evaluations. The technique was useful in identifying patch leaks and residual defects after Senning, Mustard and Fontan operations, and after closure of atrial and ventricular septal defects. Most patients were found to have no superior vena cava obstruction by contrast echocardiography after the Senning or Mustard procedure. Contrast echocardiography continues to be a useful technique in the diagnosis of a wide spectrum of congenital heart disease, as well as in the postoperative evaluation of congenital heart surgery.

Combined radiological and surgical management of arteriovenous malformation of the lung

Multiple, bilateral arteriovenous malformations (AVMs) of the lung are diagnostically and therapeutically challenging. In staged procedures over seven days, a 19-year-old woman underwent blocking of the feeding artery to six moderate-sized AVMs in the left lower lobe, embolization of three more AVMs in the left lower lobe, and resection of a large AVM in the right lower lobe through a right-sided thoracotomy. These procedures preserved maximal lung tissue, and one year later the patient is essentially symptom free.

Arteriovenous fistula of the lung

Pulmonary arteriovenous fistula is an unusual but not rare abnormality with more than 450 cases reported in the literature. Studies during the last 30 years have established the effective prevention of morbidity and relief of symptoms by operative excision. During the last 25 years, the Vanderbilt University Affiliated Hospitals have seen 7 patients with pulmonary arteriovenous fistula. This experience prompted a review of the literature. Particular emphasis is placed on current means of diagnosis and therapy.

Right pulmonary artery to left atrium communication. An unusual cause of cyanosis in the newborn

A one-day-old newborn infant presented with intense cyanosis, a continuous murmur, and mild congestive heart failure. The chest roentgenogram showed an abnormal right-heart border, and the echocardiogram demonstrated enlargement of the left ventricle and left atrium. Cardiac catheterization and angiography demonstrated a right pulmonary artery to left atrium communication. The infant responded favorably to medical management and is asymptomatic with the exception of mild cyanosis with crying. Right pulmonary artery to left atrium communication is a rare but potentially correctable cause of cyanosis in the newborn.

Contrast echocardiography

Contrast echocardiography is the technique of injecting an echo-producing, biologically compatible solution into the bloodstream and using M-mode and/or two-dimensional echocardiography to observe intracardiac bloodflow patterns revealed by the resulting cloud of echoes. This information was previously available only from angiocardiography. Contrast echocardiography has become a well-established adjunct to M-mode and two-dimensional echocardiographic examination and is valuable in the identification and validation of normal and abnormal cardiac structures, for the demonstration (and exclusion) of intracardiac as well as extracardiac shunts, and in the diagnosis of valvular regurgitation. In addition many clinical applications are being developed. Future research directions include development of videodensitometric techniques for contrast quantitation, finding contrast agents capable of passing the lung capillary bed and measurement of right heart pressures using microbubble resonance techniques.