A critical review of patent foramen ovale detection using saline contrast echocardiography: when bubbles lie

Formation of the interatrial septum: Insights obtained from cardiac computed tomographic angiography

We previously described a septal variant termed left atrial septal pouch (LASP). Present in a third of hearts, it results from incomplete fusion of the septum primum (SP) and septum secundum (SS). We assessed the prevalence of LASP using 64-section multidetector computed tomography and further characterized the different variants. Among 864 scans, 770 were of sufficient quality for assessment (428 male, aged 59.2 ± 11.7 years). They were classified on the basis of the degrees of fusion of the SP and SS into a completely fused septum (CFS), patent foramen ovale (PFO), or LASP. The lengths of the SS, SP, and overlapping SP, the maximal length of the foramen ovale (FO) floor, and the atrial dimensions were compared. A PFO was seen in 181 patients (23.5%), a LASP in 242 (31.4%), and a CFS in 339 (44.0%). There were significant differences in the length of the SS (PFO-13.6 ± 4.3 mm, LASP-17.6 ± 4.8 mm, CFS-14.3 ± 7.7 mm, p < 0.001). Hearts with LASPs had a longer overlapping SP than those with PFOs (PFO-6.3 ± 4.5 mm, LASP-13.1 ± 5.2 mm, p < 0.001). The maximal lengths of the FO floor showed differences in short axis (SAX) view (PFO-21.7 ± 4.5 mm, LASP-15.3 ± 4.3 mm, CFS-16.3 ± 4.3 mm, p < 0.001). Hearts with PFO and LASP showed similar SP lengths (27.3 ± 6.6 mm vs. 26.4 ± 6.6 mm, p = 0.10). There was a positive linear correlation between the length of the SS and the overlapping SP (R2 = 0.28, p < 0.001) with a weaker negative correlation between the SS length and maximal length of the FO floor (R2 = 0.02, p < 0.001). The groups showed similar atrial dimensions and volumes. Present in a third of patients, hearts with LASP have longer SS and overlapping SP.

Atrial septal pouches and ridges: Morphological features and potential implications in clinical practice

Incomplete or irregular fusion of the interatrial septum may result in several anatomic variants, including atrial septal pouches and ridges, whose knowledge and recognition are still poorly widespread in clinical practice. An educational review focused on the definition, clinical significance and diagnostic work-up of these anatomic findings was performed using PubMed, MEDLINE, Embase and Cochrane Central databases up to June 2023. Atrial septal pouches and ridges have been associated with an increased difficulty of catheter-based interventions requiring a transseptal approach, due to procedural challenges for transseptal puncture and the restricted motion of guidewires and catheters through the transseptal access. Additionally, left atrial septal pouch may serve as a thrombogenic nidus and a source of systemic embolism, mostly in the presence of factors leading to higher left atrial pressure and/or atrial blood stasis, which increase the risk of thrombus formation and embolic events, rather than for the only presence of left atrial septal pouch itself. Further investigations are needed in order to better elucidate the implications of such anatomic findings in daily clinical practice, and to provide the most appropriate decision-making strategies.

Respiratory-resolved five-dimensional flow cardiovascular magnetic resonance : In-vivo validation and respiratory-dependent flow changes in healthy volunteers and patients with congenital heart disease

BACKGROUND

This study aimed to validate respiratory-resolved five-dimensional (5D) flow cardiovascular magnetic resonance (CMR) against real-time two-dimensional (2D) phase-contrast MRI, assess the impact of number of respiratory states, and measure the impact of respiration on hemodynamics in congenital heart disease (CHD) patients.

METHODS

Respiratory-resolved 5D flow MRI-derived net and peak flow measurements were compared to real-time 2D phase-contrast MRI-derived measurements in 10 healthy volunteers. Pulmonary-to-systemic flow ratios (Qp:Qs) were measured in 19 CHD patients and aortopulmonary collateral burden was measured in 5 Fontan patients. Additionally, the impact of number of respiratory states on measured respiratory-driven net flow changes was investigated in 10 healthy volunteers and 19 CHD patients (shunt physiology, n = 11, single ventricle disease [SVD], n = 8).

RESULTS

There was good agreement between 5D flow MRI and real-time 2D phase-contrast-derived net and peak flow. Respiratory-driven changes had a good correlation (rho = 0.64, p < 0.001). In healthy volunteers, fewer than four respiratory states reduced measured respiratory-driven flow changes in veins (5.2 mL/cycle, p < 0.001) and arteries (1.7 mL/cycle, p = 0.05). Respiration drove substantial venous net flow changes in SVD (64% change) and shunt patients (57% change). Respiration had significantly greater impact in SVD patients compared to shunt patients in the right and left pulmonary arteries (46% vs 15%, p = 0.003 and 59% vs 20%, p = 0.002). Qp:Qs varied by 37 ± 24% over respiration in SVD patients and 12 ± 20% in shunt patients. Aortopulmonary collateral burden varied by 118 ± 84% over respiration in Fontan patients. The smallest collateral burden was measured during active inspiration in all patients and the greatest burden was during active expiration in four of five patients. Reduced respiratory resolution blunted measured flow changes in the caval veins of shunt and SVD patients (p < 0.005).

CONCLUSIONS

Respiratory-resolved 5D flow MRI measurements agree with real-time 2D phase contrast. Venous measurements are sensitive to number of respiratory states, whereas arterial measurements are more robust. Respiration has a substantial impact on caval vein flow, Qp:Qs, and collateral burden in CHD patients.

Percutaneous suture-based patent foramen ovale closure: A state-of-the-art review

Percutaneous closure of a patent foramen ovale (PFO), a common variation of interatrial septum anatomy, is a commonly performed procedure in the catheterization laboratory to reduce the risk of recurrent stroke in selected patients and to treat other PFO-related syndromes. In the last twenty years, disc-based devices have represented the armamentarium of the interventional cardiologist; recently, suture-based devices have become an attractive alternative, despite limited data regarding their long-term performance. The present review gives an overview of the current evidence regarding suture-based PFO closure, the device's characteristics, the echocardiographic evaluation of the PFO anatomy, and recommendations for patient selection. A detailed procedural guide is then provided, and potential complications and future developments in the field are discussed.

Left Atrial Septal Pouch (LASP) and Cryptogenic Stroke: A Narrative Review

Over 20% of ischemic strokes are cardioembolic strokes, necessitating research into thrombus formation locations, particularly the left atrial appendage (LAA). The left atrial septal pouch (LASP), which is linked to thrombus development and stasis, has drawn attention recently as a possible thromboembolic location, especially in atrial fibrillation (AF). The primary aim of this review is to explore LASP's role in cryptogenic strokes and to discuss the methods used to assess LAA anatomy. Imaging modalities such as cardiac computed tomography (CT) and transesophageal echocardiography (TEE) are crucial for diagnosing and characterizing LASP. LASP, found in about one-third of individuals, provides an additional site for thrombus development in the left atrium. The potential clinical implications of LASP-related thromboembolic events include the need for targeted therapeutic strategies, such as anticoagulant medication and, in some cases, consideration of LASP closure to prevent recurrent strokes. Further investigation is required to elucidate LASP's involvement in thromboembolic events and to guide stroke prevention in at-risk patients.

The size distribution of the agitated saline microbubbles for contrast transcranial Doppler generated using standard manual methods

Agitated saline microbubbles (MBs) are a common contrast agent for determining right-to-left shunt (RLS) by the contrast transcranial Doppler (c-TCD). The size of the generated bubbles is not standardized in clinical practice. MBs were generated using the recommended manual method by reciprocating motion through two syringes. The bubble size distributions (BSD) were measured using the microscopic shadow imaging technique. The results show that the diameter of MBs is mainly distributed between 10 and 100 μm, the mean bubble size is between 21 and 34 μm, the Sauter mean diameter (D32) is primarily between 50 and 300 μm, and the standard deviation (SD) is between 6 and 17 μm in 80 experiments. It provides a more accurate basis for the recommended manual method instability. The high variance values of the BSD indicate that the manual method has low stability and repeatability. The results of this study can be useful for further improvement of the reliability of c-TCD in detecting RLS. RESEARCH HIGHLIGHTS: This study provided the first detailed descriptions of the MBs size distribution in a flowing contrast agent by the microscopic shadow imaging technique. It reveals significant differences in the bubble size of manual foaming during repeated manipulations for each individual and between individuals.

Left Atrial Septal Pouch (LASP) and cryptogenic stroke risk: An updated systematic review and meta-analysis of observational studies

BACKGROUND

The left atrial septal pouch (LASP) is a small anatomical septal recess in the heart that has been linked with cardioembolic events. A systematic appraisal of the existing literature is necessary to establish a better understanding of the risk as studies continue to indicate a correlation between LASPs and cryptogenic strokes.

OBJECTIVES

To determine the level of association between the presence of LASP and the risk of developing cryptogenic stroke.

METHODS

We searched PubMed, EMBASE and Scopus for studies comparing the prevalence of LASP in patients with cryptogenic stroke against non-cryptogenic stroke control groups from inception till December, 2023. The Newcastle Ottawa scale was used for quality assessment and Comprehensive Meta-Analysis Version 3.3 was used for data analysis with odds ratio (OR) as the effect measure.

RESULTS

Our review included a total of 10 retrospective, observational studies published between 2010 to 2022. A total of 683 cases of cryptogenic strokes were identified, out of which 33.1 % (n = 271) were associated with a LASP. Among the non-cryptogenic stroke controls (n = 2641), LASP was present in 20.6 % cases (n = 476). The aggregate OR for cryptogenic stroke was 1.618 times greater than non-cryptogenic stroke (p < 0.001) among LASP cases, CONCLUSION: The presence of a septal pouch in the left atrium is significantly linked to a higher risk of developing cryptogenic strokes. As a potential site of thrombus formation and subsequent dislodgement, further large-scale studies are necessary to establish the guidelines for management and prophylaxis to prevent embolic events.

Pearls and Pitfalls in the Transesophageal Echocardiographic Diagnosis of Patent Foramen Ovale

Large randomized controlled trials have shown the benefits of percutaneous closure of patent foramen ovale (PFO) in patients with cryptogenic stroke and PFO. Recent studies have highlighted the clinical significance and prognostic implication of various anatomical features of PFO and the adjacent atrial septum, such as atrial septal aneurysm (ASA), PFO size, large shunt, and hypermobility. Transthoracic echocardiography with contrast study is used for the indirect diagnosis of PFO, as it reveals the passage of the contrast into the left atrium. In contrast, transesophageal echocardiography (TEE) offers a direct demonstration of PFO by measuring its size using the maximum separation distance between the septum primum and septum secundum. Furthermore, TEE enables the acquisition of detailed anatomical features of the adjacent atrial septum including ASA, hypermobility, and PFO tunnel length, which carry significant prognostic implications. Transesophageal echocardiography also facilitates the diagnosis of pulmonary arteriovenous malformation, a relatively rare cause of paradoxical embolism. This review provides evidence for supporting TEE as a useful screening test for patients with cryptogenic stroke to identify suitable candidates for percutaneous device closure of PFO. Additionally, cardiac imaging specialists with proficiency in comprehensive TEE examination should be part of the heart-brain team for proper evaluation of and decision-making in patients with cryptogenic stroke.

Embolic Stroke Associated With a Pulmonary Arteriovenous Fistula: An Unignorable Rare Causes of Stroke

INTRODUCTION

Here, we described a patient with ischemic stroke due to embolism, through an isolated pulmonary arteriovenous fistula (PAVF). Our case could be a paradigm of embolic stroke of undetermined source (ESUS) with an uncommon cause, providing an etiologic investigation process in addition to diagnostic pitfalls and pearls, eventually raising neurologists' ability to treat ESUS.

CASE REPORT

A 37-year-old right-handed woman presented to our emergency department with sudden onset left upper limb and lower limb weakness. She denied a past medical history of hypertension, diabetes, heart diseases, and other cerebrovascular disease risk factors, and she is without a family history of stroke, previous trauma, toxic exposure, or drug use. On admission, her physical and neurological examinations were negative, except for left-sided hemiparesis. Her routine evaluations, serum autoantibody testing, and digital subtraction angiography were negative. Subsequent diffusion-weighted brain magnetic resonance imaging demonstrated acute infarction in the right frontoparietal lobe. To find the etiology of this case, more detailed examinations were performed. Finally, she was diagnosed with ESUS, which was caused by the PAVF.

CONCLUSIONS

This case raises the awareness of a potential important emboligenic mechanism, the existence of an isolated PAVF as a right-to-left shunt in patients with a stroke of unknown origin should not be overlooked, even if a PAVF is not suggested by the initial physical findings or chest x-ray.

Interatrial septal aneurysm associated with patent foramen ovale in a dog - case report

ABSTRACT Atrial septal aneurysm (ASA) is a rare congenital deformity of variable clinical relevance, often reported in association with patent foramen ovale (PFO). Transthoracic Doppler echocardiography (TTE) is the first choice for diagnosis, but complementary techniques, such as microbubble contrast, should be used. Despite its importance, in Veterinary Medicine, there is little information related to the subject, and the present study is the second report of this condition in dogs. The objective was to report a case of ASA type IV LR associated with PFO in a Shar Pei bitch, diagnosed by a combined approach of transthoracic echocardiography backed by agitated saline solution (microbubbles). During clinical care, the owners reported episodes of seizures as their main complaint. Echocardiographic examination revealed a type 4 LR atrial septal aneurysm and left ventricular systolic dysfunction. The use of microbubble contrast showed right-to-left shunt, confirming PFO. The recommended treatment was medication. It was concluded that the rarity of ASA in dogs may be due to incomplete diagnoses and the transthoracic echocardiographic examination allows its analysis and classification. Furthermore, ASA can be found in animals with or without evidence of heart disease and it should be investigated in patients with neurological alterations.

Recurrent Episodes of Acute Myocardial Infarction Secondary to Paradoxical Coronary Artery Embolism

Coronary artery embolism is a rare cause of acute myocardial infarction, attributed to approximately 10% of all paradoxical embolisms. It is a condition that should be considered in patients who present with chest pain and have a low overall risk of coronary heart disease. A major risk of coronary artery embolism is the existence of a patent foramen ovale (PFO), which can be shown on bubble transthoracic echocardiography. Here we describe a case report of a 68-year-old Caucasian lady who presented with recurrent episodes of myocardial infarction secondary to a paradoxical coronary artery embolism which was likely due to a PFO. We emphasize the need for more research on the role of PFO percutaneous device closure compared to just medical therapy in those with recurrent episodes of acute myocardial infarction secondary to paradoxical coronary artery embolism. This, in turn, should provide clearer guidance in managing such patients with high risk of mortality.

Physiological fetal vascular shunts and failure to regress: what the radiologist needs to know

The fetal circulation is characterized by the presence of three physiological vascular shunts - the ductus arteriosus, the foramen ovale and the ductus venosus. Acting in concert, these shunts preferentially stream blood flow in a pattern that maximizes efficiency of blood oxygenation by the maternofetal unit. Shortly following the transition to extrauterine life, a quick and predetermined succession of events results in closure of these embryological structures with consequent establishment of postnatal vascular flow patterns. While this transition is often seamless, the physiological shunts of the fetus occasionally fail to regress. Such failure to regress can occur in isolation or in association with other congenital malformations. This failed regression challenges the circulatory physiology of the neonate and might have implications for the optimum functioning of several organ systems. When symptomatic, these shunts are treated. Interventions, when undertaken, might be medical, endovascular or surgical. The radiologist's role continues to expand in the assessment of these shunts, in providing a roadmap for treatment and in prompt identification of treatment-related complications. This review is to familiarize radiologists with the embryology, pre- and post-treatment imaging appearances, and associated complications of persistent fetal vascular shunts.

How Old is Too Old? Closure of Patent Foramen Ovale in Older Patients

Percutaneous closure of a patent foramen ovale (PFO) reduces the risk of recurrent cryptogenic stroke specifically in younger patients. The three randomized controlled trials that led to the widespread adoption of PFO closure excluded patients over the age of 60 years. Older patients frequently have other cardiac and vascular conditions that are common risk factors for stroke, whereas paradoxical embolism through a PFO is relatively rare. Younger patients theoretically benefit the most from closure due to longer lifetime exposure risk and absence of other traditional risk factors. PFO in older patients with cryptogenic strokes is often encountered in clinical practice, making up an increasing number of cardiology referrals, yet cardiologists lack guidelines and evaluation tools for these patients. This review explores the history of PFO closure – emphasizing data in older adults – and discusses the evaluation and treatment of older people with cryptogenic stroke and PFO while further trials in this important population are awaited.

The evolving role of echocardiography in the assessment of patent foramen ovale in patients with left-side thromboembolism

Patent foramen ovale (PFO) is the most common congenital cardiac abnormality found approximately in 25% of the adult population The pathophysiological role of paradoxical embolization through the PFO in ischemic stroke is well established. "Self-expanding double disk" and, more recently, suture-based "deviceless" systems are used for PFO closure in the setting of secondary prevention after ischemic stroke likely related to paradoxical embolization. Ultrasound plays a significant role in PFO assessment, indication to treatment, intra-procedural guidance, and follow-up for those undergoing PFO closure. Three different techniques are frequently used for these purposes: transesophageal echocardiography, transthoracic echocardiogram, and transcranial Doppler. In this review, advantages and limits of these techniques are discussed in detail to improve our skills in detection and treatment of this important condition by using ultrasound.

Prevalence of patent foramen ovale in the Greek population is high and impacts on the interpretation of the risk of paradoxical embolism (RoPE) score

Background:

The risk of paradoxical embolism (RoPE) score calculates the probability that patent foramen ovale (PFO) is causally related to stroke (PFO attributable fraction, PFOAF), based on PFO prevalence in patients with cryptogenic stroke (CS) compared with that in the general population. The latter has been estimated at 25%; however, PFO prevalence in nonselected populations varies widely.

Methods:

Since PFO prevalence in Greece remains unknown, we evaluated it and we calculated PFOAF stratified by RoPE score in a cohort of patients with CS ⩽55 years old. PFO was detected according to the international consensus transcranial Doppler (TCD) criteria in 124 healthy subjects (H), in 102 patients with CS, and in 56 patients with stroke of known cause (nonCS). Each subject underwent unilateral middle cerebral artery recording after infusion of agitated saline, at rest, and after a controlled Valsalva maneuver. We characterized PFO as large (>20 microbubbles or curtain), moderate (11–20), and small (⩽10).

Results:

PFO was detected in 42.7% of H, 49% of CS, and 25% of nonCS (p = 0.013). Large PFOs were numerically higher in CS [28.4% (29/102)] compared with H [19.3% (24/124); p = 0.1] and to nonCS [7.1% (4/56), p = 0.04]. The median RoPE score in patients with CS and PFO was seven. Even patients with very high RoPE score (9–10) had moderate PFOAF (57%). For any individual stratum up to RopE score 8, PFOAF was <33%.

Conclusions:

PFO prevalence in the Greek population is much higher than the widely accepted 25%. PFO may be the cause of stroke in one out of nine Greek patients with CS. Among Greek CS patients who harbor a PFO, the latter is causal in one out of five. The established RoPE score cutoff of ⩾7 for having a probable PFO-associated stroke may overestimate the probability in patients deriving from populations with high PFO prevalence.

Echocardiographic diagnosis of right-to-left shunt using transoesophageal and transthoracic echocardiography

Background

The diagnosis and quantification of right-to-left shunt (RLS) using transthoracic echocardiography (TTE) as well as transoesophageal echocardiography (TOE) have not been well established. We aimed to diagnose RLS by TOE using direct visualisation of the shunt and to compare the diagnosis with TTE diagnosis using conventional methods.

Methods and results

We evaluated 141 patients with ischaemic stroke for RLS by both non-sedation TOE and TTE using saline contrast and Valsalva manoeuvre. The amount (graded as 0 to IV) and timing of RLS were demonstrated. All patients were classified into four groups by TOE based on direct visualisation of shunt through a patent foramen ovale (PFO) or either pulmonary vein: no shunt (group 1: n=11), PFO (group 2: n=47), pulmonary RLS (group 3: n=25) and indeterminate RLS (group 4: n=58). All cases in group 3 showed delayed shunt, and all cases in group 4 had small shunt. On TTE findings, all cases with early appearing large shunt (cardiac cycles ≤3 and shunt grade ≥III) were group 2. Six of the eight patients with delayed appearing large shunt on TTE were group 3. TTE diagnosis of PFO using criteria of cardiac beats ≤3 and grade ≥II had a sensitivity of 85% and a specificity of 98% compared with TOE diagnosis using shunt visualisation.

Conclusions

Compared with TOE using shunt visualisation, TTE accurately diagnosed large PFO using criteria of cardiac cycles ≤3 and shunt grade ≥III. TTE possibly diagnosed pulmonary shunt using criteria of cardiac cycles >3 and shunt grade ≥III. Both modalities showed limitations in diagnosing small amount of RLS.

Review: Detection of patient foramen ovale using transcranial Doppler or standard echocardiography

A patent foramen ovale (PFO) is a common remnant of fetal circulation present in up to 25% of the worldwide adult population. Paradoxical embolism occurs when venous blood crosses the PFO into the arterial system, bypassing the pulmonary circulation. This allows for the direct passage of microemboli into cerebral blood vessels, increasing the risk of cryptogenic stroke. This review investigates the current diagnostic procedures used to detect and grade a PFO, including transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE) and transcranial Doppler (TCD). Only a few studies have directly compared the use of TTE with TCD for PFO detection but several have compared TTE and TCD independently against the clinical gold standard TOE. Known pitfalls of TTE and TCD are also discussed, including the difficulty of differentiating between intracardiac shunts and intrapulmonary shunts. This review also discusses methods to optimise imaging, such as performing an adequate Valsalva manoeuvre, the role of abdominal compression and the choice of the injection site for the contrast agent and how these may increase the diagnostic success of detecting a right-to-left shunt when prompted by a clinician.

Atrium Septal Pouch: An Anatomic Variant of the Interatrial Septum

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SP originates by partial fusion of the septum primum and septum secundum.

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SP may be a site of thrombus formation.

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SP may predispose to thromboembolic events.

Point-of-care echocardiography for the evaluation of right-to-left cardiopulmonary shunts: a narrative review

Right-to-left pulmonary and cardiac shunts (RLS) are important causes of refractory hypoxia in the critically-ill perioperative patient. Using a point-of-care ultrasound (POCUS) agitated saline bubble study for an early diagnosis allows patients with clinically significant RLSs to receive expedited therapy. This narrative review discusses the principles of agitated saline ultrasonography as well as the role of POCUS in detecting the most common RLS types seen in the intensive care unit, including patent foramen ovale, atrial septal defects, and pulmonary arterio-venous malformations. An illustrated discussion of the procedure, as well as shunt-enhancing maneuvers (Valsalva or lung recruitment maneuver with subsequent rapid release) is provided. With the wide dissemination of bedside ultrasound within the perioperative and critical care arena, POCUS practitioners should be knowledgeable of the potential pitfalls leading to both false-positive and false-negative studies. False-positive studies may be due to congenital abnormalities, mischaracterization of intrapulmonary shunts as intracardiac shunts (and vice versa), or evidence of the Valsalva effect. False negatives are typically due to respiratory-phasic variation, performing an inadequate shunt-enhancing maneuver, inadequate injection of agitated saline, or pathophysiologic states of elevated left atrial pressure. Finally, alternative POCUS methods for determining presence of an RLS in patients with poor echocardiographic windows are discussed, with a focus on pulsed-wave Doppler interrogation of arterial signals.

A new dimension in patent foramen ovale size estimation

BACKGROUND

Detailed multidimensional assessment of patent foramen ovale (PFO) size with transesophageal echocardiography (TOE) may help to determine PFO pathogenicity in cryptogenic stroke patients. We explored the potential additive value of Live xPlane and three-dimensional (3D) TOE anatomical PFO sizing techniques.

METHODS

Imaging data of 45 patients who underwent a 3D TOE-assisted percutaneous PFO closure were studied. The two-dimensional (2D) PFO separation distance and right-to-left (RL) contrast shunt magnitude were assessed on preprocedural TOE recordings. Peri-procedural measurements of the triangular anatomical PFO opening (base, height, and area) were performed after positioning of a stiff guidewire (SW) through the PFO, using Live xPlane imaging and 3D Zoom mode.

RESULTS

The PFO SW base appeared on average 5 times larger than the preprocedural 2D PFO separation (median difference [IQR] = 13[5] mm; P < .001). For a same PFO separation, the width of the PFO base may vary significantly. The PFO SW base was significantly larger in patients with a large versus a small-to-moderate PFO RL contrast shunt (18 vs 15 mm; P = .007) and in those with a spontaneous versus a provoked shunt (18 vs 14 mm; P = .003).

CONCLUSION

Live xPlane and 3D Zoom TOE allow peri-procedural measurement of the largest dimension of a PFO, which is the PFO base. Patients with a large or spontaneous RL contrast shunt appear to have a larger PFO base. The anatomical PFO base dimension may be taken into account for optimization of device and patient selection strategies.

The Efficacy of Contrast Transthoracic Echocardiography and Contrast Transcranial Doppler for the Detection of Patent Foramen Ovale Related to Cryptogenic Stroke

Background

Patent foramen ovale (PFO) has been linked to the pathophysiology of cryptogenic stroke. Contrast transesophageal echocardiography (cTEE) is the current gold standard for PFO diagnosis, but it has the disadvantage of being semi-invasive and does not exempt from risks. As a diagnostic test, the efficacy of contrast transthoracic echocardiography (cTTE) and contrast transcranial Doppler (cTCD) is controversial. This study is aimed at investigating the efficacy of cTTE and cTCD versus cTEE in PFO detection, exploring a more cost-effective and reliable method for the diagnosis of PFO related to cryptogenic stroke.

Methods

From August 2019 to January 2020, a total of 213 patients with suspected PFO were included in our study. All patients underwent cTEE, cTCD, and cTTE examinations. cTTE3 was named for using a cutoff of 3 beats to detect PFO during cTTE, and cTTE5 represented a cutoff of 5 beats. A cutoff of cTCD grade III was named cTCD III. A cutoff of grade IV was named cTCD IV. cTTE3+cTCD IV was used for the combination of a cutoff of 3 beats during cTTE with grade IV of cTCD. cTTE5+cTCD III combined a cutoff of 5 beats during cTTE with cTCD grade III. Taking cTEE as the gold standard, we compared the sensitivity, specificity, negative likelihood ratio (-LR), and misdiagnosis rate for PFO detection among the above methods.

Results

A total of 161 of 213 (76%) patients had PFO confirmed by cTEE. With the spontaneous Valsalva maneuver, the sensitivity, specificity, negative likelihood ratio (-LR), and misdiagnosis rate of cTTE3 in PFO diagnosis were 60%, 90%, 44%, and 10%, respectively, and those for cTTE5 were 76%, 78%, 31% and 22%, respectively. The sensitivity, specificity, negative likelihood ratio (-LR), and misdiagnosis rate of cTCD III were 80%, 71%, 29%, and 29%, respectively, while those for cTCD IV were 55%, 90%, 49%, and 10%, respectively. When cTTE and cTCD were combined to diagnose PFO, the specificity and misdiagnosis rate were significantly improved, especially cTTE3+cTCD IV, with 100% specificity and a misdiagnosis rate of 0.

Conclusion

cTTE or cTCD can be used for preliminary PFO related to cryptogenic stroke findings. The combination of the two methods can improve the specificity of PFO diagnosis, especially using the cutoff of cTTE3+cTCD IV.

Hypoxia due to intrapulmonary vascular dilatation in a toddler with a congenital portacaval shunt: case report

Background

The term hepatopulmonary syndrome typically applies to cyanosis that results from “intrapulmonary vascular dilatation” due to advanced liver disease. Similar findings may result from a congenital portosystemic shunt without liver disease. An adverse consequence of such shunts is intrapulmonary vascular dilatation, which affects the microvascular gas exchange units for oxygen.

Case presentation

Here, we describe a toddler with chronic cyanosis, exercise intolerance, and finger clubbing due to a malformation shunt between the portal vein and the inferior vena cava. A transcatheter embolization of the shunt resulted in resolution of his findings.

Conclusions

Congenital portosystemic shunts need to be considered in the differential diagnosis of cyanosis.

Electronic supplementary material

The online version of this article (10.1186/s12890-019-0788-8) contains supplementary material, which is available to authorized users.

The Left Atrial Appendage, Including LAA Occlusion Devices Line Watchman, Amulet, and Lariat

Atrial fibrillation is a very common arrhythmia whose prevalence is expected to increase significantly as the population ages. The associated stroke risk is a major cause of morbidity and mortality. Stroke prevention by anticoagulation carries its own risks, leading to the search for alternative strategies. Multiple techniques have been developed to exclude the left atrial appendage (the main source of thromboembolism in atrial fibrillation) from the circulation. Such techniques offer the hope of stroke prevention without the risks of anticoagulation. This article describes the percutaneous approaches being currently performed in the United States. Particular emphasis is placed on the use of transesophageal echocardiography to guide these procedures.

Reproducibility of right-to-left shunt quantification using transthoracic contrast echocardiography in hereditary haemorrhagic telangiectasia

Aim

Transthoracic contrast echocardiography (TTCE) is recommended for screening of pulmonary arteriovenous malformations (PAVMs) in hereditary haemorrhagic telangiectasia. Shunt quantification is used to find treatable PAVMs. So far, there has been no study investigating the reproducibility of this diagnostic test. Therefore, this study aimed to describe inter-observer and inter-injection variability of TTCE.

Methods

We conducted a prospective single centre study. We included all consecutive persons screened for presence of PAVMs in association with hereditary haemorrhagic telangiectasia in 2015. The videos of two contrast injections per patient were divided and reviewed by two cardiologists blinded for patient data. Pulmonary right-to-left shunts were graded using a three-grade scale. Inter-observer and inter-injection agreement was calculated with κ statistics for the presence and grade of pulmonary right-to-left shunts.

Results

We included 107 persons (accounting for 214 injections) (49.5% male, mean age 45.0 ± 16.6 years). A pulmonary right-to-left shunt was present in 136 (63.6%) and 131 (61.2%) injections for observer 1 and 2, respectively. Inter-injection agreement for the presence of pulmonary right-to-left shunts was 0.96 (95% confidence interval (CI) 0.9–1.0) and 0.98 (95% CI 0.94–1.00) for observer 1 and 2, respectively. Inter-injection agreement for pulmonary right-to-left shunt grade was 0.96 (95% CI 0.93–0.99) and 0.95 (95% CI 0.92–0.98) respectively. There was disagreement in right-to-left shunt grade between the contrast injections in 11 patients (10.3%). Inter-observer variability for presence and grade of the pulmonary right-to-left shunt was 0.95 (95% CI 0.91–0.99) and 0.97 (95% CI 0.95–0.99) respectively.

Conclusion

TTCE has an excellent inter-injection and inter-observer agreement for both the presence and grade of pulmonary right-to-left shunts.

Electronic supplementary material

The online version of this article (10.1007/s12471-018-1094-4) contains supplementary material, which is available to authorized users.

Comparison of Different Contrast Agents in Detecting Cardiac Right-to-Left Shunt in Patients with a Patent Foramen Ovale during Contrast-Transthoracic Echocardiography

The aim of this study is to evaluate the ability of two different contrast agents to detect cardiac right-to-left shunting in patients with a patent foramen ovale during contrast transthoracic echocardiography and transesophageal echocardiography. Eighty-four patients who had migraines or experienced cryptogenic stroke were prospectively enrolled. Contrast echocardiography of the right portion of the heart was performed using an injection of either (i) 8 ml of agitated saline, 1 ml of blood, and 1 ml of air (ASB) or (ii) 4 ml of vitamin B₆ and 6 ml of sodium bicarbonate solution (VSBS). All patients underwent contrast echocardiography with different contrast agents successively before undergoing transesophageal echocardiography. The diagnostic sensitivity of VSBS and ASB for cardiac shunting diagnosis was 94.23% and 78.85%, respectively. The diagnostic sensitivity in the VSBS group was significantly higher than that in the ASB group (χ² = 5.283, P = 0.022). The observed semiquantitative shunt grading suggests that the positive rate in the VSBS group was higher than that in the ASB group (Z = −1.998, P = 0.046). The use of vitamin B₆ and sodium bicarbonate solution as a TTE contrast agent yielded a high sensitivity compared with ASB. However, further trials with large sample size are required to confirm this finding.

Assessing the kinetics of microbubble appearance in cirrhotic patients using transthoracic saline contrast-enhanced echocardiography

BACKGROUND

The number of cardiac cycles that need to be reviewed by echocardiography before a significant intrapulmonary shunt can be excluded remains unclear.

METHODS

We retrospectively identified patients with cirrhosis who underwent technetium-99 m-labeled macroaggregated albumin scanning. The kinetics of bubble appearance after the injection of agitated saline during transthoracic echocardiograms were assessed in these patients.

RESULTS

For the 64 eligible patients, the mean ± SD age was 56 ± 9 years. The median (IQR) shunt fraction by radionuclide scanning was 7.7% (2.8%-19.9%). Microbubbles were seen in the left atrium (LA) and left ventricle (LV) at a median (IQR) of 4 (2-5) and 4 (2-5) beats, respectively. The number of heart cycles before microbubbles appeared in the LA or LV was inversely associated with the nuclear scanning shunt fraction (R = -0.42, P = .001, R = -0.46, P < .001, respectively). If no microbubbles were detected by heart cycle 7, the shunt fraction was uniformly less than 3%. Patients with arterial oxygen <60 mm Hg, compared to ≥60 mm Hg, had earlier appearance of microbubbles in the left heart chambers (2.6 ± 1.9 vs 4.0 ± 2.3 beats, P = .046).

CONCLUSIONS

In patients with advanced cirrhosis suspected of having hepatopulmonary syndrome, a greater shunt fraction during nuclear scanning was associated with more pronounced hypoxemia and a prompt and more intense appearance of microbubbles in the left-sided heart chambers. Patients with a shunt fraction above 3% have microbubbles in the LA or LV at some point during the first seven heart cycles.

Relationship between quantitative and descriptive methods of studying blood flow through intrapulmonary arteriovenous anastomoses during exercise

Several methods exist to study intrapulmonary arteriovenous anastomoses (IPAVA) in humans. Transthoracic saline contrast echocardiography (TTSCE), i.e., bubble scores, is minimally-invasive, but cannot be used to quantify the magnitude of blood flow through IPAVA (Q_IPAVA). Radiolabeled macroaggregates of albumin (^99mTc-MAA) have been used to quantify Q_IPAVA in humans, but this requires injection of radioactive particles. Previous work has shown agreement between ^99mTc-MAA and TTSCE, but this has not been tested simultaneously in the same group of subjects. Thus, the purpose of this study was to determine if there was a relationship between Q_IPAVA quantified with ^99mTc-MAA and bubble scores obtained with TTSCE. To test this, we used ^99mTc-MAA and TTSCE to quantify and detect Q_IPAVA at rest and during exercise in humans. Q_IPAVA significantly increased from rest to exercise using ^99mTc-MAA and TTSCE and there was a moderately-strong, but significant relationship between methods. Our data suggest that high bubble scores generally correspond with large Q_IPAVA quantified with ^99mTc-MAA during exercise.

When to use femoral vein injection for diagnosis of patent foramen ovale-Effect of a persistent eustachian valve on right atrial flow patterns during contrast transesophageal echocardiography

Contrast echocardiography using agitated saline injected into the antecubital vein is the most common method used for the diagnosis of patent foramen ovale. We describe a case whereby the presence of a persistent eustachian valve and a "negative contrast sign" during contrast transesophageal echocardiography raised suspicion of a false-negative result. Femoral vein injection of contrast successfully demonstrated a patent foramen ovale. Femoral vein injection should be considered if this scenario is recognized because the eustachian valve directs blood preferentially from the inferior vena cava toward the interatrial septum and this route may prove to be more reliable.

Transthoracic contrast echocardiography using vitamin B6 and sodium bicarbonate as contrast agents for the diagnosis of patent foramen ovale

To evaluate the utility of transthoracic contrast echocardiography (cTTE) using vitamin B6 and sodium bicarbonate as contrast agents for diagnosing right-to-left shunt (RLS) caused by patent foramen ovale (PFO) compared to that of transesophageal echocardiography (TEE). We investigated 125 patients admitted to our neurology department with unexplained cerebral infarction and migraine. All patients underwent cTTE using vitamin B6 and sodium bicarbonate as contrast agents, after which they underwent transthoracic echocardiography. The Doppler signal was recorded during the Valsalva maneuver, and TEE examinations were performed. The feasibility, diagnostic sensitivity, and safety of cTTE and TEE for PFO recognition were compared. Evidence of PFO was found in 49 (39.20%) patients with cTTE, more than were detected with TEE (39, 31.20%) (χ²=5.0625, P=0.0244). cTTE had a sensitivity of 92.31% and a specificity of 84.88% for diagnosing PFO, showing high concordance with TEE for PFO recognition (κ=0.72). Further, results of a semi-quantitative evaluation of PFO-RLS by cTTE were better than those with TEE (Z=-2.011, P=0.044). No significant adverse reaction was discovered during cTTE examination. cTTE using vitamin B6 and sodium bicarbonate as contrast agents has relatively good sensitivity and specificity for diagnosing RLS caused by PFO when compared with those for TEE. Using vitamin B6 and sodium bicarbonate as contrast agents to perform cTTE is recommended for detecting and diagnosing the PFO due to its simplicity, non-invasive character, low cost, and high feasibility.

Increased prevalence of potential right-to-left shunting in children with sickle cell anaemia and stroke

'Paradoxical' embolization via intracardiac or intrapulmonary right-to-left shunts (RLS) is an established cause of stroke. Hypercoagulable states and increased right heart pressure, which both occur in sickle cell anaemia (SCA), predispose to paradoxical embolization. We hypothesized that children with SCA and overt stroke (SCA + stroke) have an increased prevalence of potential RLS. We performed contrasted transthoracic echocardiograms on 147 children (aged 2-19 years) with SCA + stroke) mean age 12·7 ± 4·8 years, 54·4% male) and a control group without SCA or stroke (n = 123; mean age 12·1 ± 4·9 years, 53·3% male). RLS was defined as any potential RLS detected by any method, including intrapulmonary shunting. Echocardiograms were masked and adjudicated centrally. The prevalence of potential RLS was significantly higher in the SCA+stroke group than controls (45·6% vs. 23·6%, P < 0·001). The odds ratio for potential RLS in the SCA + stroke group was 2·7 (95% confidence interval: 1·6-4·6) vs controls. In post hoc analyses, the SCA + stroke group had a higher prevalence of intrapulmonary (23·8% vs. 5·7%, P < 0·001) but not intracardiac shunting (21·8% vs. 18·7%, P = 0·533). SCA patients with potential RLS were more likely to report headache at stroke onset than those without. Intrapulmonary and intracardiac shunting may be an overlooked, independent and potentially modifiable risk factor for stroke in SCA.

Evaluation of Arteriovenous Shunting in Patients With End-Stage Liver Disease: Potential Role of Early Right Heart Catheterization

BACKGROUND

In patients with end-stage liver disease (ESLD), the presence of hypoxemia suggests the presence of intrapulmonary oxygen shunting (IPS) and/or transatrial shunting. Early identification of each is imperative to avoid potentially fatal peritransplantation complications and appropriately prioritize patients for liver transplantation (LT). The aim of this work was to compare the sensitivity of transthoracic echocardiography (TTE) and right heart catheterization (RHC) with intracardiac echocardiography (ICE) for identifying the etiologies of resting hypoxemia in patients with ESLD being evaluated for LT.

METHODS

Records of 28 patients with ESLD and resting hypoxemia who underwent TTE with bubble study and RHC/ICE were reviewed. Patients with a patent foramen ovale (PFO) were compared with non-PFO patients to determine diagnostic accuracy of TTE with bubble study versus RHC/ICE.

RESULTS

TTE with bubble study diagnosed PFO, IPS, and pulmonary hypertension (PH), respectively, with sensitivities of 46%, 41%, and 25% and specificities of 46%, 45%, and 80% compared with RHC/ICE. Although IPS detected by RHC/ICE was more common in patients without a PFO (92%), 5 patients with a PFO (33%) also had IPS (P = .002). Isolated PH was detected exclusively in patients with a PFO (5/15; 33%).

CONCLUSIONS

TTE with bubble study is neither sensitive nor specific to exclude a PFO in patients with ESLD. RHC/ICE is a safe and accurate diagnostic/interventional modality in this group of patients and is useful to diagnose other comorbidities, such as IPS and PH, that may coexist and contribute to resting hypoxemia.

Transcranial Doppler ultrasonography: From methodology to major clinical applications

Non-invasive Doppler ultrasonographic study of cerebral arteries [transcranial Doppler (TCD)] has been extensively applied on both outpatient and inpatient settings. It is performed placing a low-frequency (≤ 2 MHz) transducer on the scalp of the patient over specific acoustic windows, in order to visualize the intracranial arterial vessels and to evaluate the cerebral blood flow velocity and its alteration in many different conditions. Nowadays the most widespread indication for TCD in outpatient setting is the research of right to left shunting, responsable of so called “paradoxical embolism”, most often due to patency of foramen ovale which is responsable of the majority of cryptogenic strokes occuring in patients younger than 55 years old. TCD also allows to classify the grade of severity of such shunts using the so called “microembolic signal grading score”. In addition TCD has found many useful applications in neurocritical care practice. It is useful on both adults and children for day-to-day bedside assessment of critical conditions including vasospasm in subarachnoidal haemorrhage (caused by aneurysm rupture or traumatic injury), traumatic brain injury, brain stem death. It is used also to evaluate cerebral hemodynamic changes after stroke. It also allows to investigate cerebral pressure autoregulation and for the clinical evaluation of cerebral autoregulatory reserve.

A Case of Complex PFO Leading to Ischemic Stroke: A Practical Clinical Pearl for Neurohospitalists

Patent foramen ovale (PFO) has been proposed as a mechanism for cardioembolic stroke, especially in younger patient populations. Complex PFOs, with tunnel lengths exceeding 8 mm, lead to a higher risk of neurological sequelae than simple PFOs and may also be harder to detect with transthoracic echocardiography (TTE). In this article, we present a 29-year-old woman who, after polypharmacy overdose, developed deep venous thrombosis and multiple pulmonary emboli (PE) and subsequent cardioembolic stroke. Initial TTE showed intact interatrial septum with late appearance of agitated saline in the left atrium after the seventh cardiac cycle. Subsequent transesophageal echocardiography, after treatment of PE with an intravenous thrombolytic (alteplase) and anticoagulation with heparin, showed a complex PFO with a 19-mm overlap of the septum primum and secundum without active flow. It is suggested that this PFO allowed for flow only in the situation of elevated right heart strain with PE, causing cardioembolic stroke and detection of agitated saline in the left atrium on TTE. However, under normal physiological situations, which resumed after treatment of PE with alteplase and heparin, the PFO did not allow for flow. This case demonstrates the potential importance of recognition of complex PFOs in diagnosis and management of cardioembolic stroke.

Decreased arterial PO2, not O2 content, increases blood flow through intrapulmonary arteriovenous anastomoses at rest

KEY POINTS

The mechanism(s) that regulate hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) are currently unknown. Our previous work has demonstrated that the mechanism of hypoxia-induced QIPAVA is not simply increased cardiac output, pulmonary artery systolic pressure or sympathetic nervous system activity and, instead, it may be a result of hypoxaemia directly. To determine whether it is reduced arterial PO2 (PaO2) or O2 content (CaO2) that causes hypoxia-induced QIPAVA , individuals were instructed to breathe room air and three levels of hypoxic gas at rest before (control) and after CaO2 was reduced by 10% by lowering the haemoglobin concentration (isovolaemic haemodilution; Low [Hb]). QIPAVA , assessed by transthoracic saline contrast echocardiography, significantly increased as PaO2 decreased and, despite reduced CaO2 (via isovolaemic haemodilution), was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA , although where and how this is detected remains unknown.

ABSTRACT

Alveolar hypoxia causes increased blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) in healthy humans at rest. However, it is unknown whether the stimulus regulating hypoxia-induced QIPAVA is decreased arterial PO2 (PaO2) or O2 content (CaO2). CaO2 is known to regulate blood flow in the systemic circulation and it is suggested that IPAVA may be regulated similar to the systemic vasculature. Thus, we hypothesized that reduced CaO2 would be the stimulus for hypoxia-induced QIPAVA . Blood volume (BV) was measured using the optimized carbon monoxide rebreathing method in 10 individuals. Less than 5 days later, subjects breathed room air, as well as 18%, 14% and 12.5% O2 , for 30 min each, in a randomized order, before (CON) and after isovolaemic haemodilution (10% of BV withdrawn and replaced with an equal volume of 5% human serum albumin-saline mixture) to reduce [Hb] (Low [Hb]). PaO2 was measured at the end of each condition and QIPAVA was assessed using transthoracic saline contrast echocardiography. [Hb] was reduced from 14.2 ± 0.8 to 12.8 ± 0.7 g dl(-1) (10 ± 2% reduction) from CON to Low [Hb] conditions. PaO2 was no different between CON and Low [Hb], although CaO2 was 10.4%, 9.2% and 9.8% lower at 18%, 14% and 12.5% O2 , respectively. QIPAVA significantly increased as PaO2 decreased and, despite reduced CaO2, was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA . Whether the low PO2 is detected at the carotid body, airway and/or the vasculature remains unknown.

The Role of TEE in Diagnosing Hepatopulmonary Syndrome and Cryptogenic Cirrhosis

In the vast majority of cases, ongoing hypoxemia in a cirrhotic patient is usually hepatopulmonary syndrome (HPS) until proven otherwise; in this case, HPS was suspected prior to any known diagnosis of cirrhosis. This is the first reported case in the literature whereby HPS and cirrhosis were diagnosed after the fact, rather than with the preexisting knowledge of liver cirrhosis.

Transcranial Doppler Ultrasound: Incremental Diagnostic Role in Cryptogenic Stroke Part II

Transcranial Doppler (TCD) ultrasonography is a noninvasive ultrasound study, which has been extensively applied in both outpatient and inpatient settings. Its main use in current clinical practice is the research for “Paradoxical Embolism,” due to migration of thromboembolic material from systemic venous circulation to the left cardiac chambers and arterial circulation through cardiopulmonary shunts such as patent foramen ovale which represents an important cause of cryptogenic stroke, especially in patients under 55 years of age. In this review, we shall describe the incremental diagnostic role in cryptogenic stroke for this imaging modality. TCD not only can be used to detect right-left cardiopulmonary shunts but it also allows to classify the grade of severity of such shunts using the so-called “Microembolic Signals grading score.”

Transcranial Doppler is Complementary to Echocardiography for Detection and Risk Stratification of Patent Foramen Ovale

BACKGROUND

In patients with patent foramen ovale (PFO), strategies are needed to identify patients at higher risk, who might benefit from PFO closure.

METHODS

We studied the frequency of detection of a right-to-left shunt (RLS) using transesophageal echocardiography (TEE) among patients with cryptogenic stroke and transcranial Doppler (TCD) to detect RLS, and analyzed the prediction of recurrent stroke according to TCD shunt grade, by detection of RLS on TEE, and by atrial septal aneurysm or mobility.

RESULTS

Among 334 patients with TCD, 69.8% were female, with a mean (SD) age of 53 (14) years, with a median follow-up of 420 days. There were 284 cases with TCD and TEE; 54 (19%) had atrial septal aneurysm or mobility. Echocardiography failed to show a RLS in 43 (15.1%) of the patients who had TCD and TEE, even in some patients with high-grade shunts on TCD: 18 (42%) were grade 3 or higher on TCD. Survival free of stroke or transient ischemic attack was predicted significantly by TCD shunt grade < 2 (P = 0.028), shunt grade < 3 (P = 0.03), and shunt grade < 4 (P < 0.0001); this was attenuated by adjustment for risk factors in Cox regression (P = 0.08). Neither RLS on TEE (P = 0.47), or atrial septal aneurysm or mobility (P = 0.08), predicted events.

CONCLUSIONS

Our findings suggest that TCD might be more sensitive than TEE for detection of RLS, which misses some cases with substantial RLS, and might be valuable for prediction of recurrent stroke or transient ischemic attack in patients with PFO. TCD complements TEE for management of suspected paradoxical embolism.

Saline Contrast Echocardiography in the Era of Multimodality Imaging--Importance of "Bubbling It Right"

Saline contrast echocardiography is an established imaging modality. Logical interpretation of a carefully performed study is vital to realize its diagnostic potential. In this review, we discuss utility of saline contrast echocardiography in evaluation of various pathologies within and outside the heart other than a patent foramen ovale.

Importance of an adequately performed Valsalva maneuver for detecting a right-to-left shunt indicating foramen ovale reopening

OBJECTIVES

The purpose of this study was to investigate the importance of an adequately performed Valsalva maneuver for detecting a right-to-left shunt indicating reopening of the functional closure of the foramen ovale.

METHODS

We prospectively analyzed 260 patients (102 women and 158 men; mean age ± SD, 41 ± 19 years; range, 13-83 years) who underwent transesophageal echocardiography and agitated saline injection. Two-dimensional echocardiography, color Doppler imaging, and microbubbles were used to detect right-to-left shunts, and the Valsalva maneuver was performed to determine whether the functional closure of the foramen ovale had reopened.

RESULTS

Transesophageal echocardiography with color Doppler imaging identified a patent foramen ovale in 20 patients: 18 patients with a patent foramen ovale had left-to-right shunts, and 2 patients with atrial septal defects had bidirectional shunts. Both patients with atrial septal defects showed right-to-left shunt microbubbles without and with the Valsalva maneuver, whereas all 18 patients with a patent foramen ovale showed right-to-left shunt microbubbles only after the Valsalva maneuver. Foramen ovale reopening was identified by transesophageal echocardiography in an additional 40 patients with no shunt during rest on agitated saline injection and in whom the right-to-left shunt appeared only after the Valsalva maneuver. The Valsalva maneuver could cause an atrial septal swing, and its sensitivity and specificity were 100%.

CONCLUSIONS

An adequately performed Valsalva maneuver is important for detecting a right-to-left shunt indicating reopening of the functional closure of the foramen ovale.

AltitudeOmics: impaired pulmonary gas exchange efficiency and blunted ventilatory acclimatization in humans with patent foramen ovale after 16 days at 5,260 m

A patent foramen ovale (PFO), present in ∼40% of the general population, is a potential source of right-to-left shunt that can impair pulmonary gas exchange efficiency [i.e., increase the alveolar-to-arterial Po2 difference (A-aDO2)]. Prior studies investigating human acclimatization to high-altitude with A-aDO2 as a key parameter have not investigated differences between subjects with (PFO+) or without a PFO (PFO-). We hypothesized that in PFO+ subjects A-aDO2 would not improve (i.e., decrease) after acclimatization to high altitude compared with PFO- subjects. Twenty-one (11 PFO+) healthy sea-level residents were studied at rest and during cycle ergometer exercise at the highest iso-workload achieved at sea level (SL), after acute transport to 5,260 m (ALT1), and again at 5,260 m after 16 days of high-altitude acclimatization (ALT16). In contrast to PFO- subjects, PFO+ subjects had 1) no improvement in A-aDO2 at rest and during exercise at ALT16 compared with ALT1, 2) no significant increase in resting alveolar ventilation, or alveolar Po2, at ALT16 compared with ALT1, and consequently had 3) an increased arterial Pco2 and decreased arterial Po2 and arterial O2 saturation at rest at ALT16. Furthermore, PFO+ subjects had an increased incidence of acute mountain sickness (AMS) at ALT1 concomitant with significantly lower peripheral O2 saturation (SpO2). These data suggest that PFO+ subjects have increased susceptibility to AMS when not taking prophylactic treatments, that right-to-left shunt through a PFO impairs pulmonary gas exchange efficiency even after acclimatization to high altitude, and that PFO+ subjects have blunted ventilatory acclimatization after 16 days at altitude compared with PFO- subjects.