Relief influence on the spatial distribution of the Atlantic Forest cover on the Ibiúna Plateau, SP.

Several studies suggest that, on a large scale, relief conditions influence the Atlantic Forest cover. The aim of this work was to explore these relationships on a local scale, in Caucaia do Alto, on the Ibiúna Plateau. Within an area of about 78 km(2), the distribution of forest cover, divided into two successional stages, was associated with relief attribute data (slope, slope orientation and altitude). The mapping of the vegetation was based on the interpretation of stereoscopic pairs of aerial photographs, from April 2000, on a scale of 1:10,000, while the relief attributes were obtained by geoprocessing from digitalized topographic maps on a scale of 1:10,000. Statistical analyses, based on qui-square tests, revealed that there was a more extensive forest cover, irrespective of the successional stage, in steeper areas (>10 degrees) located at higher altitudes (>923 m), but no influence of the slope orientation. There was no sign of direct influence of relief on the forest cover through environmental gradients that might have contributed to the forest regeneration. Likewise, there was no evidence that these results could have been influenced by the distance from roads or urban areas or with respect to permanent preservation areas. Relief seems to influence the forest cover indirectly, since agricultural land use is preferably made in flatter and lower areas. These results suggest a general distribution pattern of the forest remnants, independent of the scale of study, on which relief indirectly has a strong influence, since it determines human occupation.

[The value of active stents for coronary angioplasty in patients with chronic renal failure]. / Intérêt du stent actif dans l'angioplastie coronaire chez l'insuffisant rénal chronique.

UNLABELLED: The risk of intra-stent restenosis has diminished considerably with the advent of endoprostheses which actively release sirolimus or paclitaxel. Patients with chronic renal failure constitute a high cardiovascular risk population, in whom the incidence of coronary heart disease is particularly high, representing one of the principal causes of death. The aim of this study, which included 152 patients, was to quantify the value of active stents for coronary angioplasty in patients with chronic renal failure. Thirty eight patients with chronic renal failure who underwent angioplasty with active stents were matched for age, sex and the presence of diabetes with 3 other groups of patients: one group with active stents but without renal failure, one group with inactive stents and no renal failure, and one group with inactive stents and chronic renal failure. The average follow up was 16 +/- 5 months. The acute stent thrombosis rate (2%) was not elevated in cases of renal failure nor after active stent implantation. Chronic renal failure significantly increased the mortality rate 16 months after angioplasty, whichever type of stent was used: 8 versus 2% deaths in patients with an inactive stent (p = 0.001). In renal failure, the risk of death was lower with an active stent (8 vs 26% with an inactive stent, p<0.05). Similarly, there was a non-significant trend towards a lower risk of death and/or infarction in renal failure after active stents (8 vs 21% with an inactive stent, NS). CONCLUSIONS: In this study, coronary angioplasty with an active stent in patients with chronic renal failure was associated with a lower mortality rate compared with inactive stents, with no increase in the risk of acute thrombosis.

Impact of prior use or recent withdrawal of oral antiplatelet agents on acute coronary syndromes.

BACKGROUND: Oral antiplatelet agents (OAAs) can prevent further vascular events in cardiovascular disease. How prior use or recent discontinuation of OAA affects clinical presentation of acute coronary syndromes (ACS) and clinical outcomes (death, myocardial infarction [MI]) is unclear. METHODS AND RESULTS: We studied and followed up for up to 30 days a cohort of 1358 consecutive patients admitted for a suspected ACS; of these, 930 were nonusers, 355 were prior users of OAA, and 73 had recently withdrawn OAA. Nonusers were at lower risk, more frequently presented with ST-elevation MI on admission, and more frequently had Q-wave MI at discharge than prior users (36.6% versus 17.5%, P<0.001; and 47.8% versus 28.2%, P<0.001, respectively). However, there was no difference regarding the incidence of death or MI at 30 days between nonusers and prior users (10.3% versus 12.4%, P=NS). In addition, prior users experienced more major bleeds within 30 days compared with nonusers (3.4% versus 1.4%, respectively; P=0.04). Recent withdrawers were admitted on average 11.9+/-0.8 days after OAA withdrawal. Interruption was primarily a physician decision for scheduled surgery (n=47 of 73). Despite a similar cardiovascular risk profile, recent withdrawers had higher 30-day rates of death or MI (21.9% versus 12.4%, P=0.04) and bleedings (13.7% versus 5.9%, P=0.03) than prior users. After multivariate analysis, OAA withdrawal was found to be an independent predictor of both mortality and bleedings at 30 days. CONCLUSIONS: Among ACS patients, prior users represent a higher-risk population and present more frequently with non-ST-elevation ACS than nonusers. Although patients with a recent interruption of OAA resemble those chronically treated by OAA, they display worse clinical outcomes.

Stress myocardial scintigraphy and dobutamine echocardiography in the detection of coronary disease in asymptomatic patients with type 2 diabetes.

OBJECTIVE: The aims of this prospective study were: (1) to compare stress thallium-201 single photon emission computed tomography (SPECT) and dobutamine echocardiography (DE) in the detection of silent myocardial ischemia (SMI) in asymptomatic high risk diabetic patients; (2) to analyse long-term outcome after intensive care of SMI in these patients. METHODS: SPECT was performed in 100 high risk diabetic patients and DE in the first 75 patients. Coronary angiography was realized in patients with SMI, with revascularization for suitable lesions. Intensive treatment of atherosclerosis risk factors was performed in all patients. Patients were followed 2 +/- 0.5 years for the subsequent occurrence of cardiac death, myocardial infarction and revascularization. RESULTS: SMI was detected by SPECT in 62% and by DE in 10% of the patients (p < 0.0001), whereas significant coronary stenosis at angiography was detected by SPECT in 26% and by DE in 5% of the patients (p < 0.02). Independent predictive factors of significant coronary stenosis were male gender (p < 0.03) and peripheral arterial disease (p < 0.007). Nonfatal acute coronary syndrome occurred during follow-up in 2 patients (2%). Subsequent revascularization procedure was needed in 9 patients. Baseline patients' characteristics, as well as SMI, were not predictive of cardiac event during follow up. CONCLUSION: SPECT seems more accurate than DE to detect significant coronary stenosis in high risk asymptomatic diabetic patients. In this population, aggressive treatment of SMI with systematic revascularization combined with intensive care of risk factors is associated with a favorable long-term prognosis, similar in diabetic patients with and without initial SMI.

Influence of SIN-1 on platelet Ca2+ handling in patients with suspected coronary artery disease: ex vivo and in vitro studies.

The 3-morpholinosydnonimine (SIN-1) generates both nitric oxide (NO) and superoxide anion (O2-). It elicits dose-dependent vasodilation in vivo, in spite of the opposite effects of its breakdown products on vascular tone and platelet aggregation. This study was designed to investigate the influence of intravenous SIN-1 injection on platelet Ca2+ handling in patients undergoing coronary angiography. SIN-1 administration reduced cytosolic [Ca2+] in unstimulated platelets by decreasing Ca2+ influx. It attenuated Ca2+ mobilization from internal stores evoked by thrombin or thapsigargin. In vitro studies were used as an approach to investigate how simultaneous productions of NO and O2- from SIN-1 modify thrombin- or thapsigargin-induced platelet Ca2+ mobilization. Superoxide dismutase, the O2- scavenger, enhanced the capacity of SIN-1 to inhibit Ca2+ mobilization but catalase had no effect. This suggests that the effects of SIN-1 on platelet Ca2+ handling resemble those of NO, but are modulated by simultaneous O2- release, independently of H2O2 formation.

Relations of platelet Ca2+ handling and membrane microviscosity to vascular tone and restenosis after angioplasty in human coronary artery.

This study was designed to assess whether platelet Ca2+ handling or membrane microviscosity could be considered as indexes of vascular tone, or could help to predict an increased risk of restenosis after coronary angioplasty. Vascular tone was quantified in 21 patients with stable angina by the vasodilator response to sin-1 intracoronary injection in the reference coronary segment and by the importance of the acute recoil after angioplasty in the narrowed segment. The degree of restenosis was quantified by coronary angiography 6 months later. Individual values of relative sin-1-induced changes in the reference coronary diameter were positively correlated with cytosolic Ca2+ concentration in unstimulated platelets, irrespective of the extracellular Ca2+ concentration (p < 0.01). This relationship was also observed with the thrombin-evoked Ca2+ changes, measured in the absence of a Ca2+ influx (p = 0.01). No relationship was found between sin-1-induced coronary changes and membrane microviscosity evaluated by TMA-DPH and DPH anisotropies or platelet volume, or between degree of acute recoil and platelet characteristics. In conclusion, platelet Ca2+ reflects the vasodilating efficacy in response to sin-1, but cannot help to predict restenosis after coronary angioplasty.

Detection of coronary restenosis by exercise electrocardiography thallium-201 perfusion imaging and coronary angiography in asymptomatic patients after percutaneous transluminal coronary angioplasty.

Noninvasive detection of restenosis in patients remaining asymptomatic after percutaneous transluminal coronary angioplasty (PTCA) remains a major clinical problem. The value of exercise electrocardiography (ECG) and exercise-redistribution thallium-201 single-photon emission computed tomography (SPECT) in detecting restenosis in such patients remains uncertain. Discordances between these tests and coronary angiography is a common situation. We studied 179 consecutive patients remaining asymptomatic after successful PTCA (208 vessels), who underwent 6 +/- 2 months of exercise ECG, SPECT, and coronary angiography. We sought to assess the diagnostic value of the noninvasive tests compared with coronary angiography, and identify the determinants of discordances between the tests. Restenosis (diameter stenosis >50%) was detected in 39% of patients and in 37% of vessels. The overall sensitivity, specificity, and accuracy for exercise ECG and SPECT in detecting restenosis in individual vessels were, respectively, 53% versus 63% (p = 0.06), 59% versus 77% (p = 0.0001), and 57% versus 72% (p = 0. 0001). On multivariate analysis, positive exercise ECG was associated with higher heart rate response (p = 0.02), incomplete revascularization (p = 0.004), and angiographic restenosis (p = 0. 03), whereas positive SPECT was associated with incomplete revascularization (p = 0.02), infarct-related artery PTCA (p = 0.01), and angiographic restenosis (p = 0.0001). Accuracies of the 2 tests were not significantly different in patients with incomplete revascularization or PTCA of an infarct-related vessel. Overall, SPECT is more accurate than exercise ECG in detecting asymptomatic restenosis. Nevertheless, incomplete revascularization and PTCA of an infarct-related artery could cause reversible perfusion defects regardless of restenosis, reducing the diagnostic value of SPECT in such patients.

The effects of talking, reading, and silence on the "white coat" phenomenon in hypertensive patients.

To explore the mechanisms of the "white coat" phenomenon, the effects of talking, reading, and silence were analyzed. Fifty essential hypertensive patients were randomly allocated to periods of stress talking and relaxing reading, alternating with three periods of silence. While talking, systolic/diastolic blood pressure increased sharply, from 142 +/- 0.7/97.7 +/- 0.5 mm Hg to 159 +/- 0.7/111 +/- 0.5 mm Hg (P < .0001). While reading, systolic/diastolic blood pressure decreased (P < .0001). Moreover, talking and reading had opposite residual effects. The silence and reading periods gave the best approximations of the daytime ambulatory period. The predictive value of clinical blood pressure can be improved if measured during a period without talking, thus decreasing the "white coat" phenomenon.

The heparin management test: a new device for monitoring anticoagulation during coronary intervention.

Whole blood coagulation analysers are widely used during percutaneous coronary interventions. The precise degree of anticoagulation in patients is important in this setting. The aim of this investigation was to compare the results obtained with ACT (Hemochron) and HMT, the Heparin Management Test (TAS) in patients undergoing percutaneous coronary interventions. Patients (n = 100) were enrolled prospectively. Each patient received 10,000 units of heparin. At the end of the procedure, the mean ACT was 284+/-31 seconds and the mean HMT was 292+/-33 seconds. The correlation between the two methods was highly significant (r = 0.64, p<0.001). The HMT correlates well with ACT values in patients undergoing percutaneous coronary interventions. Its use in the management of these patients should be considered.

Usefulness of radionuclide ventriculography during transesophageal atrial pacing in the diagnosis of coronary artery disease.

Radionuclide ventriculography before, during, and after atrial transesophageal pacing was carried out in 15 patients with suspected coronary artery disease (CAD) and without myocardial infarction. All patients underwent coronary angiography. Ten patients (group 1) had a coronary lesion > 50% on at least one of the main coronary arteries. Five patients (group 2) had normal coronary arteries. Radionuclide left ventricular ejection fraction (LVEF) before pacing was 56 +/- 3% in group 1 and 59 +/- 3% in group 2 (NS). Radionuclide ventriculography during pacing was 45 +/- 4% in group 1 (P < 0.0001 vs basal in group 1) and 45 +/- 6% in group 2 (P < 0.01 vs basal in group 2, NS vs group 1 during pacing). Immediate postpacing ejection fraction did not differ in the two groups and was identical to the prepacing value. A quantitative regional wall motion analysis was performed in 105 segments. Regional radionuclide ventriculography was calculated in each segment as follows: end-diastolic counts-end-systolic counts/end-diastolic counts. The relative decrease in regional LVEF during pacing was more important in the 39 segments related to a narrowed vessel than in the 66 segments related to normal coronary artery (32 +/- 13% vs 13 +/- 10%, P < 0.0001). A more than 20% relative decrease in at least one segment during pacing occurred in 10 patients in group 1 (sensitivity 100%) and in 2 patients in group 2 (specificity 60%). In conclusion, global radionuclide ventriculography during transesophageal atrial pacing decreases in patients with and without CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Talking effect and "white coat" effect in hypertensive patients: physical effort or emotional content?

Talking has been shown to increase blood pressure instantaneously in hypertensive patients and to contribute to the white coat effect. The effects of talking were compared with those of counting aloud in 64 patients with essential hypertension who were randomly assigned to a period of stress talking and a period of counting aloud (active periods), alternating with three periods of silence (control). The same monitor was used for office measurements and 24-hour ambulatory blood pressure analysis. Systolic/diastolic blood pressures increased significantly more during talking (163/110 mmHg) than during counting aloud (152/102 mmHg, both p < .0001) in both treated and untreated patients and in sustained and clinical hypertension. Talking had a residual effect on systolic blood pressure that lasted 5.8 +/- 0.1 minutes. The emotional content seemed to be the only cause of the talking effect. Its instantaneous and residual effects on blood pressure and heart rate should be considered when measuring these variables.

Talking effect and white coat phenomenon in hypertensive patients.

Both white coat effect (the tendency of blood pressure to rise during a medical visit) and talking effect were analyzed in 42 patients with essential hypertension. Blood pressure was measured during the clinic visit and over the subsequent 24-hour ambulatory period, with the physician performing 49 +/- 4 measurements for each patient. Three silent periods and two talking periods (stress and relaxation) were randomly allocated in a crossover design and studied, using analysis of variance. During the initial 11-minute silent period, systolic/diastolic blood pressures increased by 6 mm Hg/5 mm Hg. During the subsequent talking periods, these variations were significantly greater: +22 mm Hg/+17 mm Hg. Measures of systolic/diastolic blood pressure were higher during stressful talking than during relaxed talking. The talking and its emotional contents seemed to explain 70% of the white coat phenomenon. To minimize the white coat phenomenon in the clinic, physicians, nurses, and clinicians are advised to measure blood pressure during an initial period of silence.

[Optimum flow of intravenous trinitrine during the acute stage of myocardial infarct with cardiac insufficiency: its effects on survival]. / Le débit optimal de trinitrine intraveineuse au stade aigu de l'infarctus du myocarde en insuffisance cardiaque. Action sur la survie.

Twenty-one patients were treated during the acute stage of a myocardial infarction for failure of the left or right ventricle. The systematic use of varying rates of flow of intravenous trinitrin (between 0.6 and 4.8 mg/h) was designed to find out for each patient the optimal effect on the cardiac index. The fall in pulmonary capillary pressure, obtained within 10 to 15 minutes, is proportional to the flow rate of trinitrin, and reaches 48% of its original value at a perfusion rate of 4.8 mg/h. The lowering of systemic arterial pressure is also proportional to the flow rate, and reaches 13% at a flow of 4.8 mg/h. The cardiac index and systolic index were significantly improved at flow rates of 1.2 to 2.4 mg/h, and lowered the pulmonary capillary pressure to levels of 17.6 mm of mercury and 15.3 mm of mercury respectively. Trinitrin given intravenously is very well tolerated, but it often become less effective after 24 hours of treatment, which implies that haemodynamic measurements must be made several times a day, and the speed of infusion often increased. The improvement in immediate and late prognosis is discussed relative to the initial values and Weber's index of survival.

[Coronary angioplasty in hemodialysis patients]. / Angioplastie coronaire chez l'hémodialysé.

The results of balloon coronary angioplasty are very disappointing in haemodialysis patients because of the high restenosis rate. On the other hand, the use of stents in this population had not previously been assessed. This retrospective study compared 63 coronary patients on haemodialysis with a référence group of 63 paired patients with respect to gender, age, and the necessity or not of stent implantation. There was a higher frequency of hypertension (79 vs 39%) and of hypertriglyceridaema (22 vs 8%) in the haemodialysis group than in the controls. However, there was no significant difference with respect to primary success rate of angioplasty (92 and 89% respectively), nor to the development of early cardiovascular complications (4% and 1.9% respectively). After a two-year follow-up, there was no significant difference in the restenosis rate in the haemodialysis patients (33%) compared with the controls (25%). Nevertheless, the mortality rate at 2 years was higher in the dialysis group (15%) compared with the reference group (3.5%, p = 0.03). However, this mortality rate was lower than that reported in the literature in haemodialysis patients after balloon angioplasty. Therefore, haemodialysis does not increase the risk of restenosis when an optimal angiographic results is obtained either by balloon angioplasty or by angioplasty with stenting. Coronary angioplasty is a safe and effective method of revascularisation in coronary haemodialysis patients when the lesions are accessible to stenting.

[Treatment of refractory unstable angina by transluminal coronary angioplasty]. / Traitement par angioplastie coronaire transluminale percutanée de l'angor instable réfractaire.

The aim of this retrospective study was to assess the value of percutaneous transluminal coronary angioplasty (PTCA) in unstable angina refractory to maximal medical therapy. The results of this procedure in these patients were compared with the results in unstable angina controlled by medication before angioplasty. Between january 1987 and january 1993, 30 patients underwent emergency PTCA for refractory unstable angina (group I). The clinical and angiographic features were compared with these of 30 patients with medically controlled unstable angina, paired for age and dilated artery (group II). The left ventricular ejection fraction was compared in the two groups (58 and 57%). The morphology of the coronary lesions according to the Ambrose classification, TIMI grading, number of lesions, degree of stenosis and severity of coronary calcification were comparable in the two groups. However, in group I, there was a significantly higher number of filling defects (30% compared with 10%, p = 0.05) and a greater number of per-PTCA complications, especially acute occlusions (23 compared with 13%, NS) with 3 deaths and 2 myocardial infarctions (compared with 1 death and 2 myocardial infarctions in group II). At long term, the restenosis, myocardial infarction and secondary death rates were comparable in the two groups with an average follow-up of 27 +/- 18 months. The poor prognosis of refractory unstable angina is therefore related to morbidity in the hospital period. These results confirm the physiopathological importance of the thrombotic process in unstable angina; the presence of "filling defect" is a poor prognostic factor associated with resistance to medical therapy. Coronary angioplasty is a valuable technique in this context but carries a higher risk of acute complications which can be reduced by an optimal platelet antiaggregant and anticoagulant therapy and in future by the use of new antithrombotic agents.

[Phase variations in the left coronary transstenotic pressure gradient before and after dilatation by percutaneous coronary angioplasty]. / Variations phasiques du gradient de pression transsténotique coronaire gauche avant et après dilatation par angioplastie coronaire percutanée.

The concept of significant coronary stenosis may be approached by studying the effects of the narrowing not in absolute values of pressure and flow but by studying the mode of blood flow across the stenosis. Ten patients with isolated stenosis of the LAD were studied for phasic variations of the transstenotic pressure gradient before and after dilatation. The material used was a ST 3.7 catheter with a 0.12 inch guide. Instantaneous pressure recording throughout the cardiac cycle were obtained using a computer. After dilatation, the area of the stenosis minus the area of transverse section of the dilating catheter increased from 0.5 +/- 0.3 to 2.2 +/- 0.3 mm2, the average gradient between the aorta and the post stenotic LAD decreased from 75 +/- 10 to 12 +/- 8 mmHg, and the ratio between the mean diastolic gradient and mean gradient increased from 75 +/- 7 to 245 +/- 30% (p less than 0.01 for the 3 parameters, paired t test). These results show that the LAD transstenotic pressure gradient is not phasic in severe stenosis. It becomes phasic, only in diastole, after dilatation of the stenosis (slight residual stenosis due to the catheter). This difference may be due to the type of flow, continuous and dependent on the stenosis before dilatation, or phasic dependent on the distal coronary circulation after dilatation. Analysis of the phasic changes of coronary flow may be useful for the evaluation of the severity of left coronary stenosis in the absence of pressure measurements.

[Tamponade without cardiac rupture after repetitive thrombolysis in acute myocardial infarction]. / Tamponnade sans rupture cardiaque après thrombolyse itérative dans l'infarctus aigu du myocarde.

The authors report the case of tamponade without cardiac rupture 48 hours after a second course of intravenous thrombolytic therapy undertaken for unstable angina in laterobasal infarction in a 72 year old woman. The outcome after ultrasonic guided pericardiocentesis and surgical drainage (700 cc) was favourable. This is a rare complication of thrombolytic therapy (10 cases) and usually observed after anterior myocardial infarction.

[Third angioplasty, and after that?]. / La troisième angioplastie, et après?

The authors studied retrospectively a series of 39 patients with a documented second restenosis after coronary angioplasty between January 1987 and November 1992, 33 of whom (31 men, 2 women) underwent a third procedure. The artery dilated was the left anterior descending (n = 17 including 9 proximal stenoses), the right coronary (n = 10), the left circumflex or its branches (n = 5) and the left main stem (n = 1). The lesions were confirmed to one vessel in 25 cases (75%) and affected two vessels in 8 cases (25%). The third angioplasty procedure was performed on a single artery in all cases. The average left ventricular ejection fraction was 60% (43%-75%). The diameter of the dilated artery was over 3.25 mm in 24% of cases (8/33). The primary success rate was 100% without any complications. The average period between the first and second angioplasties was 16 +/- 10 weeks, and between the second and third angioplasties 19 +/- 12 weeks. Angioplastic controls of the 3rd angioplasty were performed in 25 cases (75%). A third restenosis (n = 7) was treated by surgical bypass (n = 1), repeat angioplasty (n = 4), endocoronary stenting (n = 1) or medically (n = 1), with a global follow-up of 22 months (2-56 months), 2 patients underwent coronary bypass grafting, 2 have residual angina (contralateral lesion which could not be dilated), 1 had an infarct in the territory of an undilated artery, and 28 (85%) were asymptomatic. The restenosis rate after the third angioplasty procedure was 28% (7/25).(ABSTRACT TRUNCATED AT 250 WORDS)

[Treatment by redilatation and thrombolysis of occlusion occurring during percutaneous coronary angioplasty]. / Traitement par redilatation et thrombolyse des occlusions survenant lors des angioplasties coronaires percutanées.

In patients who develop acute coronary occlusion during or after percutaneous coronary angioplasty, surgery is not mandatory, and other treatments may be considered, namely redilatation and/or thrombolysis. Between June, 1984 and January, 1988 we performed 500 dilatations of coronary arteries, not counting the attempts made in the acute phase of myocardial infarction. Acute coronary occlusion without angiographic image of occlusive dissection occurred in 31 patients (6.2%) and was treated by attempted redilatation and intracoronary thrombolysis. In 10 patients (group A) either the occlusion could not be removed and emergency surgery was tried (5 cases with 2 infarctions and 1 death), or the occlusion was removed but myocardial infarction took place (5 cases). In 21 patients (group B), the occlusion was removed and the outcome was favourable without myocardial infarction. Altogether, myocardial infarction or death occurred in only 8 cases, or 26% of acute occlusions. The clinical and angiographic features of the two groups before and after angioplasty were compared; two of them differentiated group A from group B: (1) unstable angina, 7/10 in group A, 4/21 in group B (p less than 0.01), and (2) degree of stenosis, 93.1% in group A, 78% in group B (p less than 0.01). When coronary occlusion occurs during or after coronary angioplasty and is poorly tolerated with fall in blood pressure, surgery must be contemplated at once, even after recanalization of the vessel and subsidence of ischaemia. In all other cases, treatment with both redilatation and thrombolysis should restore the benefits of angioplasty without myocardial infarction.

[Doppler study of phasic variations of blood flow velocity in the anterior interventricular artery]. / Etude Doppler des variations phasiques des vitesses du sang dans l'artère interventriculaire antérieure.

Studies of changes in coronary blood flow during cardiac cycles may be a useful adjuvant to the measurement of coronary flow reserve to evaluate the hydraulic severity of coronary arterial stenoses. We used intracoronary pulsed Doppler velocimetry to measure phasic variations of blood flow in the anterior interventricular artery of 12 patients with angiographically identified stenosis of that vessel. The Doppler signal was obtained by means of a 20 MHz emission from a source placed at the tip of a catheter selectively positioned at the ostium of the anterior interventricular artery, upstream of the stenosis. The increase in severity of stenosis was paralleled by a relative decrease of diastolic blood flow velocity in relation to systolic blood flow velocity. The diastolic/systolic maximum velocities ratio was greater than 1 in 6 patients with a less than 70 p. 100 stenosis (group A) and inferior to 1 in 6 other patients with a 70 p. 100 or more stenosis (group B). In 5 patients of group B this ratio was reversed to normal after percutaneous transluminal angiography. Thus, measurement of intracoronary blood flow velocity may be helpful to evaluate the severity of stenosis, notably in the anterior interventricular artery where angiographic evaluation is difficult.