Characterization of blood flow through intrapulmonary arteriovenous anastomoses and patent foramen ovale at rest and during exercise in stroke and transient ischemic attack patients

Abstract

Novel genetic predispositions reported here in PFO subjects should be investigated further in larger stroke and/or TIA patient datasets.

The Lung in Hereditary Hemorrhagic Telangiectasia

“…The key interpretive points for TTCE include: • TTCE is considered positive for intrapulmonary rightto-left shunting if microbubbles appear in the left atrium after a delay (usually 3-4 cardiac cycles is considered a cutoff) or ramp in intensity (in contrast to intracardiac shunts); the intrapulmonary shunt origin is certain if the bubble density is greater in the left heart than in the right, often requiring 30-60 s of recording [72] • PAVMs are one cause of intrapulmonary right-to-left shunting; intrapulmonary shunting demonstrable by TTCE is also evident in ∼ 10% of the general population at rest, and the majority of healthy individuals on exercise, and/or after adrenergic stimuli [22,73,74] • A positive intrapulmonary shunt study is also more likely after injury to the delicate pulmonary capillaries, for example, following a second injection of contrast medium [72] • TTCE is usually positive in HHT1 patients (85%) [21] , and often positive in HHT2 patients (35%) [21] ; semiquantification of the shunt may help distinguish from physiological shunting and enhance the positive predictive value for a PAVM amenable to treatment [75] or complication risk [76] • In the absence of PAVMs visible on CT scan, a contrast echocardiogram demonstrating an intrapulmonary shunt does not appear to be associated with an enhanced neurological risk in HHT patients [76] ; TTCE is therefore not indicated when the presence of a PAVM has already been established by CT or during follow-up of patients with treated PAVMs; there are also reassuring data for the general population indicating that very few exercise-induced arterialized gas bubbles reach the cerebral vasculature [77] , although it is not clear that the same applies to nongaseous paradoxical emboli Different algorithms have been proposed for the screening and follow-up of adult patients with HHT according to the degree of local expertise with CE ( Fig. 3 ).…”

British Thoracic Society Clinical Statement on Pulmonary Arteriovenous Malformations

“…Radiological differential diagnoses of a PAVM include a bronchocoele, bronchopulmonary sequestration, pulmonary varix, pulmonary arterial aneurysm and aberrant systemic to pulmonary communications 2. Other causes of right-to-left shunts detectable by contrast echocardiography include intermittent shunting through intracardiac defects (when right-side pressures exceed left, most commonly after a Valsalva manoeuvre61), the hepatopulmonary syndrome62 and functional shunting (present in ~10% of the general population at rest, rising on exercise,63 after adrenergic stimuli64 and in response to low PaO 2 65). …”

Neglected intrapulmonary arteriovenous anastomoses: A comparative study of pulmonary right-to-left shunts in patients with patent foramen ovale

“…The relationship between IPAVAs and stroke still remains questionable. Tobin et al and Rapp et al have proposed IPAVAs as a possible mechanism of stroke based on necropsy and animal experiments, while some scholars suggested IPAVAs are not considered eligible for thrombus passage causing the stroke ( 10 , 29 ). In our study, the incidence of P-RLS could be as high as 79.2% in patients without PFO and 41.6% of them with stroke.…”

“…However, the incidence of PAVMs in the population is 2–3/100,000 ( 9 ), therefore, the study of P-RLS has been neglected. In recent years, some studies showed that P-RLS is a potential facilitator of stroke; at the same time, there is indeed a problem that P-RLS is regarded as PFO-RLS leading to overtreatment of PFO, they all remind us that P-RLS should not be ignored, IPAVAs in particular ( 10 – 12 ). In this study, we used contrast transesophageal echocardiography (c-TEE) and contrast transthoracic echocardiography (c-TTE) to compare P-RLS and PFO-RLS in order to investigate the characteristics of P-RLS and the relationship between P-RLS and PFO-RLS, hoping to provide new ideas and references for clinical follow-up studies and management disposal decisions of PFO.…”