Pulmonary gas exchange
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson in Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
Another suggested source of right-to-left shunt is intrapulmonary arteriovenous anastomoses (Lovering et al. 2015). Following three weeks of acclimatization to 5050 m in volunteers without a PFO, it was reported that the bubble score, an index of blood flow through the intrapulmonary arteriovenous anastomoses assessed using transthoracic saline contrast echocardiography, was significantly reduced at maximal exercise when compared to sea level (Foster et al. 2014). These findings, in the absence of any changes in the (A-a)ΔO2, were confirmed upon measurement within a few hours of arrival to 5260 m; similar findings were also apparent in a chamber study in both normoxic and hypobaric hypoxia (Petrassi et al. 2018). The physiological significance of intrapulmonary arteriovenous anastomoses at altitude remain unclear but they do not seem important from the perspective of gas exchange efficiency.
Congenital heart disease
Swati Gupta, Alexandra Marsh, David Dunleavy, Kevin Channer in Cardiology and the Cardiovascular System on the move, 2015
SymptomsSymptoms depend on the degree of pulmonary stenosis: If severe there is little pulmonary blood flow and a large right to left shunt occurs.May present similar to a large VSD (left to right shunt): Eventually, there may be a reversal of the shunt leading to central desaturation.Hypercyanotic spells are caused by muscular spasm around the area of obstruction, which may lead to myocardial infarction or cerebrovascular accidents: These episodes may be alleviated by squatting.
Congenital Heart Disease in Pregnancy
Afshan B. Hameed, Diana S. Wolfe in Cardio-Obstetrics, 2020
Severe pulmonary arterial hypertension in the presence of an intra- or extracardiac shunt results in cyanosis due to right-to-left shunting, right ventricular hypertrophy and diastolic dysfunction, and variable right ventricular systolic dysfunction. However, Eisenmenger syndrome is also a multi-organ disease. Patients have a bleeding diathesis due to low platelets and dysfunction of von Willebrand factor but may also have in situ thrombosis in the pulmonary arteries and are predisposed to thromboembolic events such as strokes due to paradoxical embolism across the shunt. The right-to-left shunt also increases risk for infection, particularly endocarditis and brain abscesses from septic emboli. Renal dysfunction can occur due to a nephrotic syndrome, or due to cardiorenal syndrome.
Clinical outcomes for congenital heart disease patients presenting with infective endocarditis
Published in Expert Review of Cardiovascular Therapy, 2020
Imaging lesion(s) and cardiac location(s) is one of the major criteria for diagnosis of IE [37–40]. IEs of the right heart are more frequent in the population of patients with congenital heart disease, and mainly target left to right shunt (interventricular communication), or tricuspid and pulmonary valve disease, or prosthetic material (aortopulmonary anastomosis, ventriculopulmonary tube, pacemaker with endocavitary probe). In this case, the vegetations are located on the right side of the VSD and may also extend on the anterior wall of the right ventricle (LV to RV jet of the VSD), the tricuspid valve and/or the pulmonary valve. The left heart IE can spread to the right heart in case of a left to right shunt, the same as the right heart IE can reach the left heart in the presence of a right to left shunt (unrepaired tetralogy of Fallot in children for example, or complex CHD and univentricular heart in adults).
Posture Dependent Hypoxia Following Lobectomy: The Achilles Tendon of the Lung Surgeon?
Published in Journal of Investigative Surgery, 2022
Athanassios Krassas, Aikaterini Tzifa, Stavroula Boulia, Kosmas Iliadis
POS is a rare and complex phenomenon that is not clearly understood. Various congenital cardiac malformations can be responsible for right to left shunting across an interatrial communication, but pulmonary and abdominal conditions may also be responsible for POS symptomatology (table 4)11. It is usually linked with a right to left shunt either intracardiac or intrapulmonary. The presence of an anatomical defect is not linked to the symptom’s manifestations. PFO is the most associated anatomical defect but also other malformations such as atrial septal defect or atrial septal aneurysms have been found. Usually, the isolated PFO do not produce a right-to-left shunt, because the PLa is 1-3 mmHg higher than the PRa leading to functional closure. This is the reason why PFO is found in 27% of adults but POS is rare. The main explanation of this discrepancy lies in the fact that for the manifestation of the syndrome two distinct conditions must co-exist: an anatomical and a functional factor. Pulmonary resection (pneumonectomy/lobectomy), as well as pericardial effusion, constrictive pericarditis, ascending aorta aneurysm and compression of the right heart chambers by liver lesions) are amongst the anatomical causes for the phenomenon. Functional factors include an elevated PRa or a condition that permits the redirection of blood stream through the shunt when the patient is moving from a recumbent to a sitting or standing position, thus producing positional hypoxia and dyspnea.
Cough maneuver is superior to Valsalva maneuver for detecting mild-extent right-to-left shunt
Published in Scandinavian Cardiovascular Journal, 2020
Yun-Xia Zhang, Xiao-Yong Zhang, Qi Zhang
A total of 149 patients had right-to-left shunt. All detected right-to-left shunt with microbubbles were seen in the left atrium within the first 3–5 cardiac cycles after the opacification of the right atrium, and were confirmed a PFO by routine transthoracic echocardiography or TEE, with a slit-like shunt between septum primum and septum secundum, obliquing to atrial septum. The right-to-left shunt detection rates differed significantly among patients using quiet respiration, Valsalva maneuver, and cough maneuver (16%, 33%, and 38%, respectively) (p < .001). The detection rate for Valsalva maneuver was significantly higher than that for quiet respiration(p < .001), while the detection rate for cough maneuver was significantly higher than that for Valsalva maneuver (p < .001) (Table 1).
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