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Biomedical subjects

S Foussas

Publications and source records attributed to S Foussas.

18 recordsLinked to original sources
PubMed2001

Comparative haemodynamic responses to the first dose of short- and long-acting ACE inhibitors in patients with congestive heart failure.

BACKGROUND: Angiotensin Converting Enzyme inhibitors (ACEi's) confer significant mortality and morbidity benefits in all functional grades of chronic heart failure (CHF). However, physicians' concerns regarding the possible occurrence of first-dose hypotension appear to be a contributing factor to their under-utilisation in both hospital and primary care settings. We investigated whether long-acting and short-acting ACEi's differ in their haemodynamic responses to the first-dose in patients with CHF. METHOD: This was a multicentre, randomised, open, two-parallel-group study of captopril 6.25 mg and perindopril 2 mg. 240 patients with CHF, age 68.9 +/- 8.9 years, of whom 66% were male, NYHA II-IV, with average blood pressure baseline values of 132.2 +/- 16.2/78.5 +/- 10.5 mmHg for systolic and diastolic blood pressure, and left ventricular ejection fraction (LVEF) of 31.3 +/- 7.4% received either captopril (n = 124) or perindopril (n = 116). Blood pressure was continuously monitored during the 8 h following drug intake. Minimum levels and maximum decreases in systolic, diastolic and mean arterial pressures were measured, along with the incidence of hypotensive episodes defined as mean blood pressure (MBP) fall > 20 mmHg, whether symptomatic or not. Subgroups of patients distributed according to age, baseline blood pressure (BP) and LVEF were subsequently analysed. RESULTS: Overall, a statistically significant treatment effect in favour of perindopril was observed. First-dose hypotension was observed more frequently following captopril than perindopril administration, with lower MAP minimal levels (78.0 +/- 8.9 vs. 84.5 +/- 10.1 mmHg, p < 0.0001), greater maximum falls (17.6 +/- 8.3 vs. 12.8 +/- 7.3 mmHg, p < 0.0001) and more frequent hypotensive episodes (42% vs. 15%, p < 0.0001). The incidence of at least one symptomatic episode was also significantly higher with captopril (10 patients vs. one patient, p = 0.029). Subgroup analyses according to age (< or = 70 years or > 70 years) or LVEF (< or = 30% or > 30%) reflected the main result. CONCLUSION: Initiation of treatment with ACE inhibitors is associated with different haemodynamic and clinical tolerances in CHF patients, regardless of their risk for hypotension, with possible clinical implications.

Aged↗
PubMed2000

The role of strict metabolic control by insulin infusion on fibrinolytic profile during an acute coronary event in diabetic patients.

BACKGROUND: Many clinical and laboratory observations give support to the hypothesis that strict metabolic control by insulin infusion during acute coronary events may improve the ischemic damage and prognosis. HYPOTHESIS: We investigated the impact of intensive insulin treatment on fibrinolytic parameters during an acute ischemic myocardial event (unstable angina or acute myocardial infarction) in patients with type 2 diabetes mellitus. METHODS: The study group consisted of 48 type 2 diabetic patients, of whom 24 were randomized to conventional therapy plus intensive insulin treatment (Group 1) and 24 to conventional therapy only (Group 2). The two groups were comparable according to gender, age, body mass index, waist:hip ratio, duration of diabetes, previous antidiabetic treatment, type of ischemic events, concomitant therapy, and the classic risk factors for coronary disease. Insulin-treated patients were excluded from the study. Plasma levels of fibrinogen, tissue plasminogen activator (t-PA), and plasminogen activator inhibitor-1 (PAI-1) were measured on admission and discharge. Fibrinogen (fibr) was measured using the photometric method. PAI-1 and t-PA were measured by enzyme-linked immunosorbent assays. RESULTS: T-PA increased in both groups during hospitalization (t-PA(admission) vs. t-PA(discharge): Group 1: 15.42 +/- 4.4 ng x ml(-1) vs. 21.2 +/- 5.74 ng x ml(-1), p = 0.000037; Group 2: 14.47 +/- 6.31 ng x ml(-1) vs. 19.18 +/- 6.88 ng x ml(-1), p = 0.001). On the other hand, fibr and PAI-1 levels increased remarkably in controls (Group 2, fibr(admission) vs. fibr(discharge): 2.98 +/- 1.04 g x l(-1) vs. 3.59 +/- 1.01 g x l(-1), p = 0.002, and PAI-1admission vs. PAI-1 discharge: 30.6 +/- 17.34 ng x ml(-1) vs. 40.62 +/- 23.48 ng x ml(-1), p = 0.003). This finding was not observed in the intensive insulin treatment group (Group 1, fibr(admission) vs. fibr(discharge): 2.87 +/- 0.73 g x l(-1) vs. 2.67 +/- 0.72 g x l(-1), p = 0.101, and PAI-1 admission vs. PAI-1 discharge: 30.75 +/- 15.81 ng x ml(-1) vs. 27.75 +/- 6.43 ng x ml(-1), p = 0.484). CONCLUSION: Intensive insulin treatment during an acute coronary event improves fibrinolytic profile in patients with diabetes mellitus. This is a possible mechanism for the reduced short- and long-term mortality in diabetic patients treated with intensive insulin treatment protocol.

Aged↗
PubMed2000

Antiplatelet is superior to anticoagulant treatment after coronary stenting: fewer coronary and other events within 30 days after stenting.

Stent prosthesis is a high efficacious method with low complication rates. However, the ideal adjunctive therapy following stent implantation remains controversial. The authors compared the effectiveness and complication rates of aspirin-ticlopidine antiplatelet therapy vs. anticoagulant therapy with acenocoumarol within 30 days following stent prosthesis. They prospectively studied 404 patients following stent prosthesis while randomly receiving anticoagulant (Group A: 201 patients) vs. antiplatelet treatment (Group B: 203 patients). Groups A and B were similar in demographic data (age, gender), stent location, clinical presentation, indication of stenting, and type of implanted stent. Chi-square test, t test, and Wilcoxon test for two samples were used for statistical analysis of the results. Stent implantation was attempted in 434 cases. This was successful in 70/85 (82%) of the bailout, 122/135 (90%) of the suboptimal, and 212/214 (99%) of the elective cases. In 201 patients anticoagulant treatment with acenocoumarol was administered for 4 weeks (group A), while 203 received antiplatelet treatment with ticlopidine (group B). The need for reintervention was less and total cardiac events were fewer in group B than in group A: three (1.5%) and nine (4.4%) vs 18 (9%) and 29 (14.4%), p<0.0008 and p<0.006 respectively. Hemorrhagic complications and total noncardiac events were fewer in group B than in group A: six (3%) and six (3%) vs. 18 (9%) and 19 (9.5%), p<0.01 and p<0.007 respectively. The length of hospital stay was shorter in group B than in A, p<0.0001. In conclusion, in this study of intracoronary stenting the authors had a high success rate in 434 attempted cases. Antiplatelet therapy was accompanied by fewer cardiac and noncardiac 1 month events when compared with anticoagulant therapy, supporting its role as the adjunctive treatment of choice post-stenting for the time being.

Acenocoumarol↗
PubMed1999

Comparison of coronary collateral circulation in diabetic and nondiabetic patients suffering from coronary artery disease.

BACKGROUND AND HYPOTHESIS: Although it is well established that diabetes mellitus (DM) induces more severe coronary artery disease (CAD), it is not known whether it contributes to the development of coronary collateral circulation. The present study examines coronary collateral circulation in diabetic and nondiabetic patients with angiographically verified CAD. METHODS: The study group consisted of 463 diabetic patients (382 men, 81 women) with a mean age of 60.3 +/- 8.8 years, and 227 nondiabetic subjects (159 men, 68 women) with a mean age of 59.2 +/- 9 years. The extension and functional capacity of coronary collateral circulation was assessed according to the Cohen and Rentrop grading system of 0 to III. RESULTS: We found that diabetic patients had grade III collateral circulation more frequently than nondiabetic subjects (13.2 vs. 8.5%, p < 0.01). This finding was even more pronounced in diabetic men aged < 55 years compared with both nondiabetic men (20 vs. 3.4%, p < 0.001) and diabetic women (20 vs. 2.2%, p < 0.001). Grade III collateral circulation was found to develop mainly at the left anterior descending (LAD) coronary artery and the right coronary artery (RCA), where complete occlusions of coronary arteries usually occur. CONCLUSIONS: Diabetic patients with CAD develop more extensive coronary collateral circulation than nondiabetic subjects, especially men aged < 55 years. The collateral circulation mainly develops at the LAD and RCA.

Adult↗
PubMed1999

Angiographic study of coronary artery disease in diabetic patients in comparison with nondiabetic patients.

Diabetes mellitus is known to be a major risk factor for the development of coronary artery disease (CAD). The aim of this study was to investigate angiographically the coronary arteries of diabetic persons, focusing on the type and distribution of CAD, sex differences in CAD anatomy, and the size of the coronary vessels. This was a randomized study and included two groups of patients with angiographically demonstrated CAD. Group A included 463 diabetics, aged 60.3 years, and Group B 210 nondiabetic patients, aged 58.5 years. The two groups were matched by age, sex, weight, and classic risk factors. The authors evaluated the regional location of CAD, left ventricular (LV) function, and the width of the lumen of coronary arteries. The diabetics had three-vessel disease more frequently (p<0.001) and one-vessel disease less frequently (p<0.001). The CAD was more extensive in Group A (mean 2.2 vessels, compared to 1.8 vessels in Group B, p<0.01). The right coronary artery was affected more often in diabetics (p<0.01), as was the anterior descending artery in three-vessel disease (p<0.05). The male diabetics had the same angiographic CAD severity as the females, although the latter had a better LV ejection fraction (p<0.05). The female diabetics < 55 years old had CAD findings comparable with those from women 4 years older in Group B. Diabetics show more diffuse and severe CAD than the general population. There are no sex-related differences in the severity of CAD.

Coronary Angiography↗
PubMed1998

Comparison of angiographic findings, risk factors, and long term follow-up between young and old patients with a history of myocardial infarction.

We compared the angiographic findings, coronary risk factors and five years prognosis in 200 patients < or =45, and 260 patients >45 years old who where admitted with an acute myocardial infarction. We found that family history and smoking were the most common risk factors in patients < or =45 years old P<0.04, P<0.0001, respectively, and hypertension and diabetes mellitus were more prevalent in patients >45 years, P<0.00001 for both. Young patients had a higher incidence of normal coronary arteries and a lesser one of triple vessel disease in comparison with old ones P<0.001 and P<0.04, respectively. There was also a tendency for young patients to have a higher frequency of single vessel disease. The long-term prognosis was favourable in the younger age group since the survival rate was much better, as well as the quality of life. Death in the young patients seems to be very often electrical owing to sudden ventricular fibrillation, whereas death in the elderly is more often associated with congestive heart failure.

Adult↗
PubMed1998

Comparison of spirapril, isradipine, or combination in hypertensive patients with left ventricular hypertrophy: effects on LVH regression and arrhythmogenic propensity.

This study was designed to evaluate in 45 hypertensive patients with left ventricular hypertrophy (LVH) the effects of a 6-month course with one of three different antihypertensive regimens (the calcium channel blocker isradipine, the angiotensin converting enzyme inhibitor spirapril in monotherapy, or a combination of the two drugs, n = 15 per group) on blood pressure, LVH regression, and various functional correlates of LVH. All three treatment modalities decreased significantly LV mass index by an average of 10%, although the combination had the greatest blood pressure-lowering effect and spirapril had the least, as assessed by office resting pressures, ambulatory monitoring, and isometric grip testing. There was no correlation between magnitude of blood pressure lowering and degree of LVH regression. The effects of treatment on pressor hormone profiles differed among groups, as spirapril tended to suppress angiotensin II and norepinephrine, whereas isradipine had opposite effects. Exercise tolerance was prolonged by all three regimens, but significantly more by the combination. All three regimens decreased significantly the double product by 10% to 15%. Indices of electrophysiologic stability calculated from analysis of ambulatory electrocardiogram exhibited significant improvement in several parameters such as QRS duration, presence of late potentials, and measures of heart rate variability, resulting in fewer episodes of simple or complex ventricular arrhythmia. We conclude that all three regimens produce significant LVH regression associated with improved functional capacity and electrical stability. These results reflect the sum of the differential hemodynamic and hormonal effects exerted by each treatment modality.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Dissection During Restenotic Lesion Balloon Angioplasty: Comparison with Initial Angioplasty.

The aim of this study was to assess the frequency and severity of dissection during repeat angioplasty for restenosis, to correlate the occurrence of this event with the lesion characteristics and the procedure-related factors and to examine if dissection during initial angioplasty predisposes to dissection during the repeat procedure. Sixty-nine significant lesions in native coronary arteries were treated with balloon angioplasty (A«PTCA) and retreated for restenosis with balloon angioplasty (B«PTCA). Dissection was detected less frequently during B«PTCA (7/69 vs. 18/69, p < 0.05). Anatomic variables did not differ significantly between A« and B«PTCA. Balloon to artery ratio (B/A ratio) was slightly but significantly higher during B«PTCA (1.03 +/- 0.13 vs. 0.97 +/- 0.14, p < 0.05) and duration of inflation was shorter (377 +/- 218 vs. 473 +/- 305 sec, p < 0.05). In 17 out of the 18 lesions which were dissected during A«PTCA, dissection did not occur during B«PTCA, despite the application of a higher B/A ratio (1.05 +/- 0.13 vs. 0.97 +/- 0.17, p < 0.05). Duration of inflation was shorter during B«PTCA (390 +/- 227 vs. 639 +/- 394 sec, p < 0.05). Six out of seven lesions which were dissected during B«PTCA had not been dissected during A«PTCA. In this subgroup, lesion characteristics did not differ between the two interventions and duration of inflation was shorter during B«PTCA (340 +/- 101 vs. 458 +/- 128, p < 0.05). CONCLUSIONS: Dissection occurred less frequently during restenotic lesion PTCA. Dissection during A«PTCA did not predispose to dissection during B«PTCA. These findings may be ascribed to the proliferative nature of the restenotic process.

Journal Article↗
PubMed1997

Hemodynamic and humoral correlates in essential hypertension: relationship between patterns of LVH and myocardial ischemia.

While evaluating 45 hypertensive patients with left ventricular hypertrophy (LVH) for enrollment in a clinical research protocol, we had the opportunity to compare anatomic and functional characteristics of those with LVH and ischemia on an exercise tolerance test (ETT), but without coronary artery disease by angiography (group I, n=8), versus those with a normal ETT (group II, n=37). There were no differences in age, sex, severity, and duration of hypertension between the two groups, but group I patients were significantly more overweight and had a worse lipid profile. Blood pressure at peak ETT was higher in group I despite shorter exercise duration, although resting and ambulatory pressures were similar. Group I patients had evidence of more pronounced cardiac enlargement and LVH by both ECG and echo criteria and a characteristic pattern of more pronounced thickening at the apex, but both groups had equally good systolic function and similar degrees of mild diastolic dysfunction. Analysis of 24-hour ambulatory ECG showed a significantly greater propensity to ventricular arrhythmias in group I, as shown by the presence of late potentials in 4 patients, the presence of couplets in 3, runs of ventricular tachycardia in 2 (while none of group II patients had late potentials or complex arrhythmias), and an average frequency of isolated premature ventricular contractions approximately three times higher in group I than group II patients. Our data demonstrate that hypertensives with LVH associated with myocardial ischemia at stress but with normal coronary arteriograms tend to be more overweight, attain a higher systolic blood pressure at ETT despite a shorter duration, have a higher propensity for severe arrhythmias, and have an adverse lipid profile. LVH in these subjects is more pronounced by both ECG and echo criteria and is characterized by predominantly apical hypertrophy with left atrial and ventricular dilatation rather than overall LV wall thickening.

Adult↗
PubMed1996

Hyperventilation test in syndrome X.

The hyperventilation (HV) test has been extensively used in different forms of coronary artery disease. The purpose of this work was to investigate the response to HV in patients with syndrome X and compare HV with exercise (EX) test. The authors studied 20 patients with syndrome X (angina, a positive EX test, and normal coronary angiogram) and 20 healthy subjects who underwent HV and EX tests. In 7 patients, all women, angina and electrocardiographic (ECG) changes occurred during HV but in none of the controls. Patients with syndrome X and controls had a similar rate-pressure product (RPP) at rest and achieved a similar RPP with HV. The RPP achieved with HV in patients with syndrome X without ECG changes was significantly lower, 121.8 +/-29.1(mean +/-SD), than what was achieved by those with changes, 167.9 +/-42.9, P < 0.01. In patients with an abnormal response to HV the RPP at which angina and ECG changes occurred was similar to that where similar changes were observed during EX. There was a significant correlation of the RPPs between the two tests, r=0.82, P < 0.02. In contrast, in patients in whom no angina or ECG changes occurred, the RPP they achieved with HV was significantly lower than the anginal threshold during EX 204 +/- 47.4, P < 0.0001. In conclusion, a significant proportion of patients with syndrome X, mainly women, who achieve a high RPP with HV, develop angina and ECG changes during overbreathing. The close relation between EX and HV RPPs where these changes occur suggests an increased myocardial oxygen demand as the most likely underlying mechanism for this behavior.

Electrocardiography↗
PubMed1996

Usefulness of Renal Arteriography Following Coronary Angiography.

PURPOSE: To determine the usefulness of renal angiography in patients that underwent coronary angiography because of clinically suspected coronary artery disease. METHODS: Selective arteriography of the renal arteries was performed in 205 patients (mean age 60 +/- 8 years; 80% males) at the time after coronary angiography with the use of right coronary Judkins catheter. RESULTS: Two-hundred renal angiographies were judged technically adequate. Average additional fluoroscopy time was 3 +/- 2 min and 30 +/- 8 ml of additional contrast medium was used. Coronary artery disease (³ 50% narrowing) was found in 158 (79%). Renal arterial disease was found in 17 (8.5%) patients. Reduction in lumen diameter was < 50% in 11 patients (5.5%) including 3 patients with bilateral stenosis, and ³ 50% in 6 patients (3%). The only clinical variable associated with renal artery stenosis was peripheral vascular disease. CONCLUSION: There is no justification for doing routine renal angiography for patients undergoing coronary arteriography because the prevalence of severe renal artery stenosis is low.

Journal Article↗
PubMed1995

Effect of preload and afterload on ventricular arrhythmogenesis.

To examine whether it is an increase in preload or afterload that may cause ventricular arrhythmias, the ventricles of 13 anesthetized open-chest dogs were bandaged. Next, metaraminol, an almost pure alpha stimulator, was given, followed by removal of the bandage. The ventricles were then sucked in a plastic cup, which was finally removed. The systolic and diastolic ventricular pressures were measured, and the presence of arrhythmias (ventricular ectopic beats or ventricular tachycardia) was observed. Banding the ventricles caused a significant diminution of systolic pressure (-42 +/- 38.0 mmHg; mean +/- SD) and a rise in diastolic pressure (+3.5 +/- 3.7), starting from control values of 126 +/- 36/6.5 +/- 3.0, but no arrhythmia. Metaraminol raised both pressures (+122 +/- 58 and +9.0 +/- 10.3) and caused ventricular arrhythmias in 6 of 13 experiments. Removing the bandage further increased the systolic pressure (+45 +/- 42) and reduced the diastolic pressure (-7.2 +/- 10.3), but made the arrhythmia worse in 10 of 13 experiments. Suction reduced both pressures (-166 +/- 96 and -5.4 +/- 14) and stopped all arrhythmias. Removing the cup increased both pressures (+133 +/- 68 and +15.5 +/- 15.3, respectively) and worsened the arrhythmia in seven of eight experiments. In general, deterioration of ventricular arrhythmias was observed in 23 of 25 maneuvers with either an increase or no change in systolic pressure, but in none of the maneuvers was there a decrease (P < .0001) in systolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Hyperinsulinaemia in syndrome X: a marker of the syndrome?

BACKGROUND: Stimulated hyperinsulinaemia is observed in some patients with syndrome X, defined as angina, positive stress test and normal coronary arteriography, and may be involved in the pathogenesis of the syndrome. An increased sympathetic response to exercise may also be pathogenetically involved. However, the diagnostic value of hyperinsulinaemia as a marker of this syndrome has not been defined. METHODS: We determined blood glucose and immunoreactive insulin during fasting, at 60 and 120 min after a glucose load of 75g in 21 patients (eight men, 13 women, 53.9 +/- 7.1 years old) with syndrome X and in 21 healthy volunteers matched to the patients for age, sex and body mass index (eight men, 13 women, 51.6 +/- 9.3 years old). Insulin values were related to the rate-pressure product increase at first exercise stage. RESULTS: The glucose values as well as the insulin values during fasting were similar in syndrome X patients and in controls. However, significantly higher insulin values (mU/l) were observed at 60 (P < 0.01) and 120 min (P < 0.005) in syndrome X patients (median 75.5 and 52, range 43-290 and 6.1-212, respectively) than in controls (median 47.5 and 24.5, range 8-195.6 and 5.2-164, respectively). A considerable overlap of insulin values, however, was observed between the two groups, with abnormal values even during fasting. For a specificity of 95%, an abnormal insulin value had a sensitivity of between 19 and 24% and a diagnostic accuracy of 57-60%. A significant positive correlation was found between insulin levels after the glucose load and the rate-pressure product increment with exercise (60 min, r = 0.60; 120 min, r = 0.65). CONCLUSION: Hyperinsulinaemia may be pathogenetically involved in syndrome X patients, in close relation to the higher sympathetic drive that characterizes this syndrome. However, the wide range of insulin values, frequently overlapping with normal values, limits the usefulness of this abnormality as a marker of the syndrome.

Blood Glucose↗
PubMed1994

[Single coronary artery].

A single coronary artery is a rare abnormality of the coronary circulation (0.09% in the authors' experience), a fortuitous finding on coronary angiography. The authors report three new cases of this abnormality, including one with a ventricular septal defect and another with ischaemic heart disease. Exercise stress testing was positive in two patients.

Adult↗
PubMed1994

Intracoronary Palmaz-Schatz stent placement after complicated angioplasty: medium term follow-up.

Acute or impending coronary artery occlusion during percutaneous coronary balloon angioplasty represents a serious and potentially life-threatening complication. We studied the clinical and angiographic outcome in 21 patients who underwent emergent intracoronary Palmaz-Schatz stent implantation (11 due to persistent residual stenosis and 10 due to flow-limiting dissection) during complicated balloon angioplasty and who were followed for a mean period of 7.9 +/- 5.7 months. Excluding one patient lost to follow-up, the event-free survival rate was 70%. Six (30%) patients developed adverse clinical events. One died and 3 required elective revascularization procedures. One subacute stent thrombosis was documented. Acute Q-wave myocardial infarction occurred in 2 patients. Among 9 patients studied angiographically 5.6 +/- 2.5 months after stent placement, 2 had developed restenosis (> 50% luminal narrowing). Eleven have remained essentially symptom free. For selected patients, emergent deployment of a Palmaz-Schatz coronary stent, following complicated balloon angioplasty, offers satisfactory long-term results, thus obviating the need for a high risk emergency bypass surgery.

Angioplasty, Balloon, Coronary↗
PubMed1992

Effect of successful coronary angioplasty on the signal-averaged electrocardiogram.

The effect of successful coronary artery angioplasty on the signal-averaged electrocardiogram (SAECG) was examined in 50 patients (41 men, 9 women, aged 55 +/- 8 years) with stable (26 patients) or unstable angina (24 patients) and good overall left ventricular function (ejection fraction = 55% +/- 8%). The SAECG was recorded before and within 24-48 hours after the angioplasty and was filtered at 40-250 Hz, with 250 beats averaged. The noise level averaged 0.57 +/- 0.15 microV before and 0.56 +/- 0.17 microV after the procedure. There was no overall significant difference between pre- and postangioplasty SAECGs. Subgroup analysis showed that 14 patients had a significant increase of the root mean square voltage of the last 40 msec of the filtered QRS that was independent of noise level changes, previous myocardial infarction, stable or unstable angina status, positive or negative baseline SAECG, or vessel being dilated. Eleven patients (22%) had late potentials at baseline, of whom four (36%) lost them after angioplasty, while one patient developed them after the procedure, all due to root mean square voltage changes. Thus, successful angioplasty exerted no significant overall effect on the SAECG, suggesting that the substrate of late potentials was not grossly altered by the procedure in our patients. However, there appear to be some patients, constituting approximately one third of this study population, who derive a favorable influence on the SAECG from angioplasty, a subgroup that needs to be further defined in future studies.

Angina Pectoris↗
PubMed1990

Laser thermal angioplasty probe ("hot tip") temperature: effects of flow.

The temperature developed by the laser thermal ("hot tip") probe during arterial recanalisation is primarily dependent on the rate of energy delivery and the rate of dissipation to the surrounding medium. While higher probe tip temperatures enhance the efficacy of atheroma ablation, so too is the incidence of adverse effects increased. We studied the temperature developed in the probe tip in an artificial circulation using both saline and blood. In saline the peak probe temperatures were limited to 100 degrees C (boiling point), falling with each increment in flow. Small discrepancies in probes at different times and may be due to malalignment of the optical fibre-metal cap coupling, temperature measurement inaccuracy, tip insulation, or generator output instability. In blood, charring and clot formation insulated the tip raising the temperature (up to 700 degrees C within 5 seconds at 10 W) but also retarded dissipation of heat to the surroundings. The degree of clot and char formation was critical in determining subsequent thermal responses in any particular probe. The unknown rate and quantity of char buildup and changing blood flow during in vivo angioplasty are likely to be important obstacles to developing a reliable thermal feedback control system.

Angioplasty, Balloon↗