Ascending aortic curvature as an independent risk factor for type A dissection, and ascending aortic aneurysm formation: a mathematical model.

OBJECTIVE: To develop a mathematical model to demonstrate that ascending aortic curvature is an independent risk factor for type A dissections, in addition to hypertension, bicuspid aortic valve, aneurysm of ascending aorta, and intrinsic aortic tissue abnormalities, like Marfan's syndrome. METHODS: A steady state one-dimensional flow analysis was performed, utilising Newton's third law of motion. Five different clinical scenarios were evaluated: (1) effect of aortic curvature; (2) effect of beta-blockers, (3) effect of patient size, (4) forces on a Marfan's aorta, and (5) site of entry flap in aortic dissection. RESULTS: Aortic curvature increases the forces exerted on the ascending aorta by a factor of over 10-fold. Aortic curvature can cause patients with a systolic blood pressure of 8 0mmHg to have greater forces exerted on their aorta despite smaller diameters and lower cardiac outputs, than patients with systolic blood pressures of 120 mmHg. In normal diameter aortas, beta-blockers have minimal effect compared with aortic curvature. Aortic curvature may help to explain why normal diameter aortas can dissect, and also that the point of the entry tear may be potentially predictable. Aortic curvature has major effects on the forces exerted on the aorta in patients with Marfan's syndrome. CONCLUSIONS: Aortic curvature is relatively more important that aortic diameter, blood pressure, cardiac output, beta-blocker use, and patient size with regard to the force acting on the aortic wall. This may explain why some patients with normal diameter ascending aortas with or without Marfan's syndrome develop type A dissections and aneurysms. Aortic curvature may also help to explain the site of entry tear in acute type A dissection. Further clinical study is needed to validate this study's finding.

Survival of patients with or without symptoms undergoing potentially curative resections for primary lung cancer.

BACKGROUND: Numerous historical screening programs to detect lung cancer have been undertaken. With technologic advances, complimentary diagnostic tests have been developed; however, only the National Lung Cancer Trial has demonstrated increased survival. Following the success of this study, screening programs are being trialled in several countries. Screening should, in theory, reduce lung cancer deaths by identifying asymptomatic patients with earlier tumors. This study asked whether lung cancer patients who are asymptomatic at presentation have a better survival than those who present with symptoms. METHODS: This was a retrospective analysis of a validated prospective thoracic surgery database from a tertiary center in the Northwest of England. Included were 1,546 consecutive patients (826 men, 720 women) who received operative intervention for non-small cell lung cancer. The main outcome measures included 5-year survival and univariate and multivariate Cox regression analysis. RESULTS: Cancer stage, age, and operation type were confirmed as being of prognostic importance, validating previous studies. Survival between asymptomatic or symptomatic patients did not differ significantly (p = 0.489), regardless of stage. The hazard ratios (with 95% confidence intervals) for variables associated with poorer outcome identified by Cox's regression analysis were male sex, 1.34 (1.15 to 1.56); advancing age, 1.03 (1.02 to 1.04); advancing stage, 3.30 (2.69 to 4.04); and pneumonectomy, 1.24 (1.01 to 1.52). Symptoms were not a significant variable affecting survival on multivariate analysis. CONCLUSIONS: This retrospective study from the Northwest of England showed that in our subset of lung cancer patients undergoing resection, asymptomatic patients with non-small cell lung cancer do not have improved survival, implying it is a systemic disease in many at diagnosis. Care should be taken when generalizing the results of the National Lung Screening Trial to all populations until further validation has been performed.