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Biomedical subjects

T J Ryan

Publications and source records attributed to T J Ryan.

At least 271 records · Page 15Linked to original sources
PubMed1986

The treatment of cutaneous vascular lesions with the infra-red coagulator: a preliminary report.

The treatment of vascular naevi with lasers is widely practised. The concept of specific vascular damage was an early ideal but it is much harder to attain than had been anticipated. The favourable results achieved by coagulation necrosis of the epidermis and upper dermis with the argon and CO2 lasers prompted us to try to produce the same changes with non-laser radiation. We have used an infra-red coagulator to treat flat vascular naevi and ectatic blood vessels. The handpiece which looks like a gun has a light guide capped by a 6 mm diameter sapphire. This size combined with a pulse duration of less than 1.0 second enables large areas of skin to be treated quickly. Preliminary results are presented.

Humans↗
PubMed1986

Percutaneous coronary laser thermal angioplasty.

Percutaneous coronary laser thermal angioplasty was successfully performed before conventional balloon angioplasty in a 55 year old white man with a 90% left anterior descending artery stenotic lesion and angina at rest (Canadian Heart Association class IV). The lesion was reduced to 50% residual stenosis using a 1.7 mm laser-heated metallic capped fiber and two pulses of 8 W of argon laser energy, each delivered for 5 seconds. With subsequent balloon angioplasty, the lesion was further decreased to 10% residual stenosis. The entire procedure was well tolerated without chest pain or burning, vessel perforation or spasm, thrombus formation or embolization of debris. The patient was free of pain at 1 month follow-up. This case demonstrates the feasibility of safely performing percutaneous coronary laser thermal angioplasty. Additional studies are indicated to determine the clinical role and potential benefits of coronary laser thermal angioplasty in relation to the established procedures of bypass surgery and conventional balloon angioplasty.

Angiography↗
PubMed1986

Contribution of vasopressin to vasoconstriction in patients with congestive heart failure: comparison with the renin-angiotensin system and the sympathetic nervous system.

Ten patients with advanced congestive heart failure were treated with an arginine vasopressin V1 antagonist during hemodynamic monitoring to determine the contribution of vasopressin to vasoconstriction in this disorder. The vasopressin antagonist caused a decrease in systemic vascular resistance in the three patients whose plasma vasopressin was greater than 4.0 pg/ml (average for the group was 2.4 +/- 0.6). Plasma vasopressin concentration correlated with the percent decrease of systemic vascular resistance (r = 0.70, p less than 0.025), serum sodium (r = 0.72, p less than 0.02) and serum creatinine (r = 0.85, p less than 0.005). To compare the relative roles of vasopressin, the renin-angiotensin system and the sympathetic nervous system, these patients also received captopril and phentolamine. Captopril decreased systemic vascular resistance by 20% (p less than 0.05), mostly in patients with high plasma renin activity. Levels of plasma renin activity ranged between 1 and 46 ng/ml per h (average 14.7 +/- 5.7) and correlated with serum sodium (r = 0.77, p less than 0.025), serum creatinine (r = 0.73, p less than 0.025) and right atrial pressure (r = 0.67, p less than 0.05). Phentolamine decreased systemic vascular resistance in all patients (average 34%, p less than 0.01), but the decrease did not correlate with the pretreatment norepinephrine concentration. Norepinephrine levels were elevated in all patients (694 +/- 110 pg/ml) and correlated with baseline stroke volume index (r = 0.75, p less than 0.025) and plasma renin activity (r = 0.67, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

The role of exercise testing in identifying patients with improved survival after coronary artery bypass surgery.

To determine whether exercise testing can identify patients whose survival might be prolonged by coronary artery bypass surgery, the results of bypass surgery were compared with those of medical therapy alone in 5,303 nonrandomized patients from the Coronary Artery Surgery Study registry who underwent exercise testing. Patients in the two treatment groups differed substantially with regard to important baseline variables. Analysis of 32 variables by Cox's regression model for survival revealed an independent beneficial effect of bypass surgery on survival (p less than 0.00001). Patients were then stratified into subsets according to the results of exercise testing. Surgical benefit was greatest in the 789 patients who exhibited at least 1 mm of ST segment depression and who could exercise only into stage 1 or less. Among the 398 patients with three vessel coronary disease showing these characteristics, 7 year survival was 58% for the medical group and 81% for the surgical group (p less than 0.001). There was no difference in survival between the surgical and medical groups among the 1,545 patients without ischemic ST segment depression who were able to exercise into stage 3 or greater. Thus, in patients who demonstrate ischemia on exercise testing and whose exercise capacity is limited, coronary bypass surgery appears to improve survival in comparison with medical therapy alone.

Coronary Artery Bypass↗
PubMed1986

Precise dermal damage with an infrared coagulator.

Using an infrared coagulator, we have shown, in pigskin, a direct relationship between depth of injury and the duration of infra-red pulses, which was highly reproducible at a particular site. This has been related to the clinical results achieved in one patient whose three tattoos were treated with different pulse times.

Adult↗
PubMed1986

The influence of surgery on the natural history of angiographically documented left ventricular aneurysm: the Coronary Artery Surgery Study.

Coronary artery bypass surgery with or without aneurysmectomy has been used to treat patients with angiographically defined left ventricular aneurysm. To evaluate whether surgery benefits such patients, we analyzed the data from 1131 patients who were enrolled in the registry of the Coronary Artery Surgery Study. Four hundred sixty-seven patients underwent bypass surgery, of which 238 also had left ventricular resection, and 30 had resection alone. The overall operative mortality was 7.9%; the operative mortality was 7% for bypass alone compared with 9% for bypass surgery plus left ventricular resection (NS). Long-term survival by life-table analysis was similar for both medically and surgically treated patients (69% vs 67%, respectively). Cox survival analysis identified congestive heart failure score, duration of chest pain, extent of coronary disease, left ventricular end-diastolic pressure, age, and surgical therapy as important predictors of outcome. Patient subsets that showed improved survival with surgical therapy after adjustment for inequities in baseline characteristics were patients with three-vessel disease and those patients in moderate- and high-risk subgroups. Surgical therapy significantly reduced symptoms of angina and use of cardiac medications but the incidence of recurrent infarction was similar for both therapies.

Age Factors↗
PubMed1986

Effect of externally applied skin surface forces on tissue vasculature.

The effect of surface forces on the morphologic pattern of skin capillaries was examined on the anterior surface of the forearm of healthy volunteers. A rig was designed to permit the application of uniaxial forces between two pads attached to the skin surface. A grid was printed onto the skin surface, and mechanical data are presented in terms of force intensity versus strain. During force application the skin capillaries were monitored using vital capillary microscopy. Mean values of force intensity and strain of 1.33N/mm and 10%, respectively, were sufficient to produce virtual obliteration of the blood flow to the capillaries. A simplified finite element model of the tissue was also employed to illustrate the effect of surface forces at different depths within the tissue. This study emphasizes the potentially damaging effects of surface forces on the integrity of the skin vasculature. If these forces are maintained or repeated, cell necrosis and eventual tissue damage would result.

Adolescent↗
PubMed1986

Acquired port-wine stain.

The development of a capillary hemangioma in adult life is an unusual event. These lesions normally occur as congenital cutaneous nevi. We describe the history and histologic findings in a man who developed such a lesion after a cricket ball injury to the right cheek at age 46 years. The literature on acquired port-wine stain is reviewed. Discussion is centered on whether there are factors predisposing to this response to injury and whether damage to autonomic nerves is important.

Facial Injuries↗
PubMed1986

Early experience with in situ saphenous vein bypass for distal arterial reconstruction.

During a 36-month period 74 patients underwent infrainguinal in situ saphenous vein bypass to the popliteal or tibial vessels. The first 54 operations were performed with standard valvulotomes and valve-cutting scissors, while in the last 20 operations a new intraluminal valve-cutting device was used to incise the valves. Ninety-four percent of bypasses were performed for limb salvage, 80% of all operations were done to the tibial vessels, and 31% of bypasses were done to the ankle vessels. The operation was attempted in 81 patients and completed in 74 patients, for a vein utilization rate of 91%. Fifty-five percent of all veins had a distal diameter of less than 4 mm (average 3.6 mm). The patency rates were 92% at 3 months and 90% at 12 and 36 months for all grafts. There were six failed grafts, all within the first 6 months, and eight diabetic patients required reoperation, two for missed valve leaflets, and three needed revision of the distal anastomosis; however, all these grafts were patent at the time of reexploration. There were four perioperative deaths and two patients had nonfatal postoperative myocardial infarctions. This study demonstrates that in situ saphenous vein grafting provides for a high vein utilization rate and suggests that the technique provides for higher graft patency and limb salvage rates than do more traditional types of procedures.

Actuarial Analysis↗
PubMed1985

Coronary sinus occlusion pressure and its relation to intracardiac pressure.

The hemodynamic components of coronary sinus (CS) occlusion pressure in humans have not been well described. If no other outflow for venous blood were present, then after acute occlusion of the coronary sinus the pressure would increase and equal aortic pressure. However, if thebesian vein drainage between the left ventricle and the coronary veins has an important role in humans, then CS occlusion pressure might reflect left ventricular (LV) pressure through transmitted LV pressure or intramyocardial pressure. To study this relation, 27 patients who underwent routine diagnostic cardiac catheterization were evaluated. Occlusion was accomplished by sudden inflation of a No. 7Fr balloon-tipped catheter placed into the CS. LV end-diastolic pressure and end-diastolic CS occlusion pressure were simultaneously recorded at rest. LV end-diastolic pressure (16.7 +/- 5.6 mm Hg) was not significantly different from end-diastolic CS occlusion pressure (15.9 +/- 5.4 mm Hg). LV end-diastolic and end-diastolic CS occlusion pressures were positively correlated (p less than 0.001) over the entire range of pressures (9 to 27 mm Hg). In contrast, systolic CS occlusion pressure was significantly lower than LV systolic pressure and unrelated to right-sided heart pressures. It is concluded that in humans, end-diastolic CS occlusion pressure closely parallels LV end-diastolic pressure, and measurement of CS occlusion pressure to assess LV end-diastolic pressure may have clinical use. These findings also suggest the existence of hemodynamically important thebesian vessel connections that may have implications for retroperfusion or pressure-controlled intermittent CS occlusion in humans.

Blood Pressure↗
PubMed1985

Photoaffinity labeling of functionally different lysine-binding sites in human plasminogen and plasmin.

Photoaffinity labeling of human plasmin using 4-azidobenzoylglycyl-L-lysine inhibits clot lysis activity, while the activity toward the active-site titrant, p-nitrophenyl-p'-guanidinobenzoate, or alpha-casein are maintained. Photoaffinity labeling of native Glu-plasminogen with the same reagent causes incorporation of approximately 1.5 mol label per mol plasminogen. This labeled plasminogen can be activated to plasmin by either urokinase or streptokinase. The resulting plasmin has full clot lysis activity and can be subsequently photoaffinity labeled with a loss of clot lysis activity. The rate of activation of labeled plasminogen by urokinase is increased relative to that of native plasminogen. epsilon-Aminocaproic acid blocks incorporation of photoaffinity label into both plasminogen and plasmin, indicating that the labeling is specific to the lysine-binding sites. The labels are located in the kringle 1+2+3 fragment in either photoaffinity-labeled plasminogen or plasmin. These results indicate that the specific lysine-binding site blocked in plasmin acts in concert with the active-site in binding and using fibrin as a substrate. This clot lysis regulating site is not available for labeling in plasminogen, but is exposed or changed upon activation to plasmin. The different lysine-binding sites labeled in plasminogen may regulate the conformation of the molecule as evidence by an enhanced rate of activation to plasmin.

Affinity Labels↗
PubMed1985

Comparison of coronary artery bypass surgery and medical therapy in patients 65 years of age or older. A nonrandomized study from the Coronary Artery Surgery Study (CASS) registry.

We compared the results of coronary artery bypass surgery with those of medical therapy alone in 1491 nonrandomized patients 65 years of age or older. Cumulative survival at six years (adjusted for major differences in important base-line characteristics) was 79 per cent in the surgical group and 64 per cent in the medical group (P less than 0.0001). At five years, chest pain was absent in 62 per cent of the surgical group and 29 per cent of the medical group (P less than 0.0001). Analysis by the Cox proportional-hazards model suggested an independent beneficial effect of surgery on survival (P less than 0.0001). Patients were divided into risk quartiles on the basis of preoperative predictors of survival identified by the Cox model. Surgical benefit was greatest in "high-risk" patients (those in the two quartiles containing patients with the poorest prognosis). Among 234 "low-risk" patients with mild angina, relatively good ventricular function, and no left main coronary artery disease, there was no survival difference between those treated medically and those treated surgically. We conclude that in specific higher-risk subsets of non-randomized patients 65 years of age or older, coronary bypass surgery appeared to improve survival and symptoms in comparison with medical therapy alone. These conclusions must be tempered by consideration of the limitations of nonrandomized studies, particularly since patients in the two treatment groups differed substantially with regard to important base-line characteristics.

Aged↗
PubMed1985

Value of arm exercise testing in detecting coronary artery disease.

Alternative methods of exercise testing are needed for patients with vascular, orthopedic or neurologic conditions who cannot perform leg exercise. To determine the sensitivity of arm exercise in detecting coronary artery disease (CAD), 30 patients with angina pectoris performed both arm ergometry and treadmill testing before coronary angiography. All patients had at least 70% diameter reduction in 1 or more major coronary arteries. Ischemic ST depression (greater than or equal to 1 mm) or angina occurred more frequently (86%, 26 patients) with leg exercise than with arm exercise (40%, 12 patients). There was no significant difference in peak rate-pressure product achieved with either test, although the peak oxygen consumption was greater during leg exercise than during arm exercise (18 vs 13 ml/kg/min, respectively, p less than 0.001). For concordantly positive tests, the oxygen consumption at onset of ischemia was significantly lower during arm testing than during leg testing (12 vs 17 ml/kg/min, respectively, p less than 0.001). There was no significant difference in heart rate during either test at onset ischemia. Thus, arm exercise testing is a reasonable, but not equivalent, alternative to leg exercise testing in patients who cannot perform leg exercise.

Aged↗