Rajanbabu Balram Babu, Chigullapally Raviraju
Department of Pediatric Cardiac Surgery, Apollo Hospitals, Hyderabad, 500033 India.
Indian J Thorac Cardiovasc Surg. 2019 Oct;35(4):548-556. doi: 10.1007/s12055-019-00816-z. Epub 2019 Apr 26.
Late presentation of large left to right shunts is a major problem in developing countries and evaluating the operability is a challenge during preoperative evaluation. The factors that determine the development and progression of the pulmonary vascular disease are still largely unknown, though there is evidence to show that increased pulmonary flow is the main contributing factor. We have found cases of operability despite late presentation of ventricular septal defect (VSD). In some of these cases, the reason for operability may lie in associations. We herein attempt to provide a mathematical explanation for their operability.
To assess the effect of different levels of obstruction and elevated ventricular end-diastolic pressure on pulmonary flow.
Mathematical flow analogy models were constructed and analysed based on Ohm's law and the laws governing flow in series and parallel flow circuits.
Any narrowing in the pulmonary circulation produces a reduction in pulmonary blood flow and the pulmonary to systemic blood flow ratio, irrespective of its position. This increases the systemic flow and blood pressure if the ventricular performance remains constant. A rise in ventricular end-diastolic pressure reduces the total cardiac output, pulmonary flow and systemic blood flow with a preserved pulmonary to systemic flow ratio. The absolute reduction in pulmonary flow will exceed the absolute reduction in systemic flow, with its ratio being in proportion to the ratio of systemic to pulmonary vascular resistance. However, a higher pressure will be transmitted distally in these settings. These mechanisms of flow reduction may prevent irreversible pulmonary vascular disease.
Distal pulmonary obstruction or elevated ventricular end-diastolic pressure can reduce pulmonary blood flow and may prevent irreversible pulmonary vascular disease. Clinical studies in this direction are recommended for validation.
在发展中国家，大型左向右分流的延迟就诊是一个主要问题，并且在术前评估期间评估手术可行性是一项挑战。尽管有证据表明肺血流量增加是主要促成因素，但决定肺血管疾病发展和进展的因素仍 largely 未知。我们发现了室间隔缺损（VSD）延迟就诊但仍具有手术可行性的病例。在其中一些病例中，手术可行性的原因可能在于相关因素。我们在此试图为其手术可行性提供一种数学解释。
评估不同程度的梗阻和升高的心室舒张末期压力对肺血流量的影响。
基于欧姆定律以及串联和并联流动回路中的流动规律构建并分析数学流动类比模型。
无论其位置如何，肺循环中的任何狭窄都会导致肺血流量和肺循环与体循环血流量之比降低。如果心室功能保持不变，这会增加体循环血流量和血压。心室舒张末期压力升高会降低总心输出量、肺血流量和体循环血流量，同时保持肺循环与体循环血流量之比。肺血流量的绝对减少将超过体循环血流量的绝对减少，其比例与体循环与肺循环血管阻力之比成正比。然而，在这些情况下，更高的压力会向远端传递。这些血流量减少的机制可能会预防不可逆的肺血管疾病。
远端肺梗阻或升高的心室舒张末期压力可减少肺血流量，并可能预防不可逆的肺血管疾病。建议在这个方向进行临床研究以进行验证。
