As cardiac surgeons, in clinical practice, we often encounter children/patients who are diagnosed with congenital heart disease (hereafter referred to as “congenital heart disease”) combined with pulmonary hypertension and are told that they have lost the chance of surgical correction. So, how does congenital heart disease cause pulmonary hypertension, what types of congenital heart disease may cause pulmonary hypertension, and are there really no surgical opportunities for these patients? This article attempts to answer these questions through a question and answer format. As in the past, this article is aimed at patients and families suffering from this disease as a guide in their medical search and treatment; therefore, I do not intend to reproduce the contents of textbooks, but will try to focus on the description of the treatment process. I hope that the prescriptions will be corrected. 1.What congenital heart diseases may cause pulmonary artery hypertension (hereinafter referred to as PAH, Pulmonary Artery Hypertension)? Theoretically, all congenital heart diseases with “left-to-right shunt” may cause PAH, the so-called “left-to-right shunt” refers to the pathophysiological process in which blood from the body circulation is shunted to the pulmonary circulation through a congenital abnormal channel; correspondingly, it is “right-to-left shunt” precordial disease. The “left-to-right shunt” preconditioning includes many of the most common types of preconditioning anatomy, such as ventricular septal defect, atrial septal defect, arteriovenous ductus arteriosus, and to a lesser extent, permanent arterial trunks, main pulmonary windows, and certain types of aortic dislocation; the total number of these is more than 2/3 of all preconditioning. 2. Why Why does “left-to-right shunt” preconditioning cause PAH? As the name implies, the main pathophysiological feature of “left-to-right shunt” preconditioning is the transfer of blood from the body circulation to the pulmonary circulation, which leads to a significant increase in the volume of blood in the pulmonary circulation and a constant congestion of the pulmonary vascular bed. This leads to a significant increase in blood volume in the pulmonary circulation and a constant congestion of the pulmonary vascular bed, resulting in an increase in pulmonary artery pressure. We call this PAH due to congestion “dynamic” pulmonary arterial hypertension. At this stage, as long as the heart malformation is corrected and the left-to-right shunt is eliminated, the pulmonary blood volume will return to normal and PAH will be reduced. However, if the precordial disease is not corrected in time, the pulmonary vessels will gradually increase, thicken and harden under the influence of long-term congestion, and lose their normal elasticity; the pulmonary circulation pressure will also increase progressively, thus evolving from “dynamic” to “organic” PAH. “When the development reaches a certain level, pulmonary hypertension will be irreversible; even if the heart malformation is corrected at this time, the pulmonary artery pressure can no longer be reduced. To use an inappropriate analogy, this is like an arrow off the string; once it is sent, it is no longer meaningful to rewind the “bow” (precordial disease), and the “arrow” (PAH) will still run according to the established track. This stage is called “Eissenmenger Syndrome” in professional terminology. 3.What are the dangers of severe PAH? The immediate consequences of PAH are twofold. ①Decrease in pulmonary blood. As the pulmonary artery pressure continues to rise, the pressure step difference between the body circulation and the pulmonary circulation gradually decreases, and the shunt flow through the congenital anomalous channels will gradually decrease, from the original left-to-right shunt to a bidirectional shunt, or even a “right-to-left shunt” (from the pulmonary circulation to the body circulation). More importantly, the development of the pulmonary vascular lesions themselves will inevitably lead to a decrease in pulmonary vascular capacity. In advanced stages, the patient’s pulmonary blood volume will be significantly lower than normal, thus causing severe hypoxic symptoms; ② right heart insufficiency. The increase of pulmonary artery pressure means that the resistance of pulmonary circulation will increase, and the burden on the heart will become bigger and bigger, which will eventually lead to right heart insufficiency (also known as heart failure). (iii) Indirect consequences. The development of pulmonary hypertension may initiate a series of complex pathologies. For example, long-term hypoxia will lead to an increase in hematocrit and blood viscosity, making the patient susceptible to thrombosis, especially pulmonary embolism; at the same time, the lesion of the pulmonary vasculature itself may also cause pulmonary vascular rupture, leading to hemoptysis, etc. In short, severe PAH is a great threat to human health, and the quality of life of patients will be seriously reduced, their mobility will be gradually reduced, and their life expectancy will inevitably be significantly shortened. 4.What are the possible symptoms of severe PAH? PAH itself does not have specific clinical manifestations, but when it causes the above-mentioned pathophysiological changes, it will produce corresponding symptoms. The most common symptoms when patients visit the clinic include: decreased activity tolerance, especially shortness of breath and weakness after activity; chest pain, syncope, hemoptysis, palpitations, and lower extremity edema, chest tightness, dry cough, angina, abdominal distention and hoarseness. Shortness of breath often marks the development of right heart insufficiency in patients with PAH. And when syncope or blackout occurs, it often marks that the patient’s cardiac blood output has significantly decreased. 5. Does it mean that once PAH is detected, no more surgery or treatment of precordial disease is possible? I have spent a lot of time on the mechanism of PAH caused by precordial disease, but many readers may still have a partial understanding of it. I just hope you can understand: congenital heart disease is not correctable at any age, and for left-to-right shunt preconditioning, you must strive to receive surgery or interventional treatment before the development of PAH reaches a severe stage, so as to eliminate the heart malformation in time and block the motivation of PAH development. This timing is what we image as the “window of time” for surgery. Once the window is removed, surgery is not only unhelpful, but may be harmful, and the patient falls into the inevitable fate of PAH. However, as mentioned earlier, the elevation of pulmonary artery pressure due to precordial disease is also a dynamic evolutionary and progressive process. In the stage of dynamic pulmonary hypertension, it is entirely possible for the pulmonary artery pressure to return to normal after correcting the precordial disease; whereas, if organic pulmonary hypertension has fully developed, the surgery loses its meaning. Therefore, it is important not to give up the hope of surgical treatment once PAH is diagnosed. The key is to correctly determine the stage of PAH development, or to clarify whether PAH is reversible, in order to reasonably formulate the next treatment plan. The rate of PAH progression is related to the specific anatomical type of the precordial disease and also correlates with the severity of the malformation. For example, small ventricular septal defects, even if left untreated, may not cause PAH, while larger ventricular defects (so-called “non-restrictive” ventricular defects) are often recommended to be surgically treated at least before the age of 2 years in order for PAH to be completely reversible; at the same time, many children with permanent arterial trunks can only be operated before the age of 1 year in order not to develop severe PAH. At the same time, many children with permanent arterial trunks do not develop severe PAH until surgery is performed before the age of 1 year. 6. I was examined at the primary hospital and the doctor told me that I have preexisting heart disease and that my pulmonary hypertension is now too severe for surgery. Do I still have a chance for surgery? This is a critical question and the reason that prompted me to write this article. Objectively speaking, there is no method that can determine with certainty the stage of development (or reversibility) of PAH. For example, echocardiography (also known as “cardiac ultrasound”) is the most commonly used diagnostic tool, but ultrasound alone cannot accurately assess pulmonary vascular resistance and its recoverability, which is the most important basis for determining the feasibility of surgery. The most authoritative test currently recognized is lung biopsy. However, due to the heterogeneous nature of the lesion, it is difficult to define whether the biopsied lung tissue is representative of the vascular disease status of the whole lung. With the growing understanding of PAH, we have found that many patients with PAH, previously thought to be irreversible, do have a decrease in pulmonary artery pressure after surgery. In other words, their PAH can still be reversed, or at least significantly reduced. A number of assessment methods have now been developed to help determine more accurately the extent of PAH progression and the feasibility of surgery. Getting these methods right will allow more patients/children to have a chance at saving their lives. I will describe them in detail in the next section.