The effect of atropine used in dobutamine stress echocardiography on pupil diameter.

BACKGROUND: The use of atropine during dobutamine stress echocardiography (DSE) is contraindicated in persons with narrow angle glaucoma though there is limited evidence that low doses of intravenous atropine do not cause pupillary dilation. OBJECTIVE: The aim of this study is to investigate whether atropine when administered in persons without glaucoma during dobutamine stress echocardiography causes pupillary dilation. METHODS AND RESULTS: Out of 144 patients without a history of glaucoma referred for DSE for clinical indications, 105 patients received intravenous atropine doses ranging from 0.1 mg to 1.25 mg (most patients received 0.25-0.75 mg). Pupil diameter of both eyes was measured under the same light conditions before and after the DSE using a CP-30 Optical Digital PD Ruler. For the total of 210 examined eyes pupil diameter remained unaltered after each DSE test (3.65 ± 0.799 mm before vs 3.63 ± 0.766 mm after, p = .737). Similarly, pupil diameter remained unchanged when left and right eyes were assessed separately (right eye: 3.770 ± 0.812 before vs 3.752 ± 0.745 mm after, p = .821 and left eye: 3.521 ± 0.770 before vs 3.499 ± 0.770 mm after, p = .806). Diameter of right and left pupil were also unaltered after grouping patients by sex and iris pigmentation. Age, weight, atropine dose and propranolol dose were not correlated with changes in pupil diameter. CONCLUSION: Intravenous atropine in usual doses administered in DSE does not cause mydriasis in adults without glaucoma. Future studies need to confirm our findings and expand the investigation regarding safety of atropine use during DSE in patients with narrow angle glaucoma.

A minor experimental stenosis in porcine descending thoracic aorta affects the spectral content of pressure pulse wave.

OBJECTIVE: To carry out research into the possible changes of the spectral content of pressure pulse wave after the creation of an experimentally induced stenosis in the pig descending thoracic aorta. METHODS: Eight healthy, normotensive Landrace pigs were subjected to thoracotomy under sterile conditions. At the upper segment of the descending thoracic aorta, a 5-mm-long circumferential symmetric constriction was imposed and stabilized; hence, a 15-20 mm Hg pressure gradient was established. Pressure tip catheters were used in order to monitor the pressure gradient. Blood flow disturbances were recorded through a bidirectional Doppler flow meter at pre- and poststenotic areas (A and B, respectively). Measurements were carried out before, 10 min after, and 90 days after the creation of the stenosis. The recorded waveforms were analyzed mathematically by using Fourier Transform, in order to determine their spectral component. Eight sham-operated pigs were used as controls. RESULTS: Fourier Transform analysis showed a significant increase (P < 0.05) of spectral content in A and B areas. Also, the "relative" harmonic amplitudes in nonstenotic subjects were higher than in stenotic animals (P < 0.05). CONCLUSIONS: A minor experimental constriction located at the level of the descending thoracic aorta increased the spectral content of the pressure pulse wave, indicating that spectral analysis may detect slight flow disturbances before developing remarkable signs of an impaired circulation system.

Effect of an experimental stenosis in the porcine descending thoracic aorta.

OBJECTIVE: To investigate the alterations of mechanical properties in pre- (A) and post- (B) stenotic aortic regions after an experimentally induced stenosis in the descending thoracic aorta. METHODS: Eight healthy, normalipemic and normotensive Landrace pigs were subjected to thoracotomy under sterile conditions. In the upper segment of the descending thoracic aorta a circumferential symmetric constriction 5 mm in length was imposed and stabilized; thus, a 15-20 mm Hg pressure gradient was established. The pressure gradient was verified via catheterization of the vessel with pressure tip catheters. Pre- and poststenotic hemodynamic disturbances were recorded by the use of a bidirectional Doppler flowmeter. Pressure and flow measurements were carried out before, 10 min after, and 90 days after the creation of the stenosis. Euthanasia was performed after 90 days, and the descending thoracic aorta removed. In the A and B regions serial sections of aorta (5 mm in length) create appropriate aortic "rings," to test in a uniaxial tension device, in order to determine the mechanical properties of the vessel. Histological analysis was performed, so as to estimate the content (%) of collagen and elastin fibers within the aortic wall. Eight sham-operated pigs were used as controls. RESULTS: Reverse blood flow was recorded at both the A and B sites, and was maintained until euthanasia. Reverse flow in the poststenotic region B was greater than that in the prestenotic region. Mechanical analysis showed that the aortic wall in A and B regions became stiffer particularly at high strains (P < 0.05). Histological analysis indicated that the percentage of elastin fibers remained almost the same in both regions while the percentage of collagen fibers increased considerably, especially in the B region (P < 0.05). CONCLUSIONS: A nonhemodynamically significant experimental stenosis located at the level of the descending thoracic aorta induced reverse blood flow before and after the stenosis. The higher the reverse flow, the more collagen fibers were produced and the stiffer the aortic wall. Since hypercholesterolemia can be ruled out as a hardening factor in the present study, disturbed flow seems to be an independent factor which activates fibroblasts to overproduce collagen and to eventually reduce the aorta's compliance.