Biomedical subjects

T J Ryan

Publications and source records attributed to T J Ryan.

533 records · Page 30Linked to original sources

PubMedDate not supplied

Acute effects of transluminal angioplasty in three experimental models of atherosclerosis.

Transluminal angioplasty has shown promise as a nonoperative treatment of atherosclerotic obstruction. Despite its increasing clinical use and potential importance, little is known of its mechanism and acute effects. To evaluate transluminal angioplasty, three rabbit models of experimental atherosclerosis were developed: Group 1 (n = 20) = high cholesterol diet plus balloon de-endothelialization; Group 2A (n = 12) = high cholesterol diet plus an indwelling catheter; Group 2B (n = 10) = normal diet plus an indwelling catheter. After 6 weeks or 8 weeks, distinct angiographic and pathological lesions in the iliac artery were evident in all groups. Group 1 showed predominant foam cell lesions, while Group 2 showed eccentric mixed fibrous and foam cell or only fibrous lesions. Significant angiographic stenosis was present in 78% of the animals. Angioplasty of the highest grade iliac stenosis resulted in at least a 20% reduction in luminal diameter narrowing in 26 of 37 animals (70%). Histopathological examination 1 day following angioplasty in 17 animals showed two patterns. In Group 1 animals, neointimal fracture and dissection were evident, while in Group 2 animals thinning and stretching of the nonatherosclerotic portion of the vessel walls could be demonstrated. This study demonstrates that the New Zealand rabbit can be used to produce a spectrum of morphologically distinct atherosclerotic lesions that lend themselves to the study of transluminal angioplasty. The immediate consequences of angioplasty, which appear to depend upon the underlying histopathology and widening of the narrowed lumen, are frequently concurrent with intimal fracture, dissection, or thinning of the nonatherosclerotic portion of the vessel wall.

Angioplasty, Balloon↗

PubMedDate not supplied

Restenosis following transluminal angioplasty in experimental atherosclerosis.

Percutaneous transluminal angioplasty has received considerable attention in the treatment of obstructive atherosclerotic lesions in humans. However, restenosis frequently occurs and has limited the long-term effectiveness of this procedure. To study restenosis, a model of atherosclerosis was developed in 16 New Zealand rabbits. Atherosclerosis was induced in one or both iliac vessels by balloon deendothelialization followed by a 2% cholesterol diet for 6 weeks. Angiographic lesions were demonstrable in all animals. Fourteen iliac vessels served as controls, and nine underwent successful angioplasty with an increase in luminal diameter from 1.0 +/- 0.2 to 1.9 +/- 0.4 mm (p less than 0.01). After 4 weeks on a high cholesterol diet, all animals had another angiogram, which documented significant progression of disease in only six of 14 control iliac vessels, but in all nine dilated vessels. The average decrease in luminal diameter was 0.2 +/- 0.3 mm for the control group compared with 1.6 +/- 0.5 mm for the dilated group (p less than 0.01). Histopathological correlates revealed further remodeling of at various stages of organization and recanalization. In summary, this study demonstrates that restenosis occurs following transluminal angioplasty and is significantly more frequent than the natural progression of disease in a rabbit model of atherosclerosis. The mechanism of this restenosis appears to be related to intraluminal thrombosis and acceleration of atherosclerosis. Evaluation of antiplatelet drugs in the prevention of restenosis seems warranted.

Angioplasty, Balloon↗

PubMedDate not supplied

Indirect assessment of carotid occlusive disease by ocular pneumoplethysmography. 500 mm Hg vacuum pressure measurements and ocular pulse timing.

The interpretation and diagnostic value of the ophthalmic artery pressure measurement and ocular pulse timing modes of the 500 mm Hg vacuum OPG-Gee ocular pneumoplethysmograph were evaluated in 65 patients who underwent aortic arch and cerebral arteriography. Data analysis revealed the OPG-Gee differential tracing which electronically compares and amplifies differences between the right and left eye pulse waveforms to be of little value. In predicting the presence of a greater than or equal to 50 percent diameter unilateral stenosis, an eye-eye pulse interval of greater than 15 msec was 82 percent accurate, a greater than or equal to 5 mm Hg ophthalmic artery pressure difference was 77 percent accurate and when combined these two criteria were 84 percent accurate. Neither of the criteria intended to detect bilateral carotid lesions, eye-ear pulse interval nor ophthalmic/brachial pressure index, were reliable. Ocular pulse timing was found to be highly specific but insensitive to hemodynamically significant carotid disease. OPG-Gee pressure determinations were more sensitive but lacked specificity. In combination, these criteria allowed identification of unilateral hemodynamically significant lesions with a sensitivity of 83 percent and a specificity of 86 percent. If used to detect more severe degrees of arteriographic stenosis, 60 and 70 percent diameter reduction, the overall diagnostic accuracy of these techniques was not improved. These results do not justify the use of the OPG-Gee instrument as a single noninvasive test for carotid arterial disease.

Arterial Occlusive Diseases↗

PubMedDate not supplied

Applications of intra-aortic balloon counterpulsation.

Intra-aortic balloon counterpulsation (IABC) is the form of mechanical circulatory assistance in widest clinical use today. The clinical results with IABC employed in 63 patients over a four-year period are presented. The clinical conditions necessitating mechanical circulatory assistance were: cardiogenic shock following acute myocardial infarction; myocardial infarction complicated by mitral valyular regurgitation or ventricular septal defect; preinfarction angina syndrome; postcardiotomy cardiogenic shock with pump oxygenator dependence; postcardiotomy cardiogenic shock during the postoperative recovery period; and septic shock. Survival and discharge from hospital occurred with 32 of 63 patients (51%). Evaluations of left ventricular function were studied in 20 patients on IABC by construction of Frank Starling curves, with cardiac output determined by thermodilution techniques. In general, IABC shifted the curves to the left and increased their slope.

Acute Disease↗

PubMedDate not supplied