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Biomedical subjects

M Canny

Publications and source records attributed to M Canny.

At least 19 recordsLinked to original sources
PubMed2001

Contributions to the debate on water transport.

The useful criticisms of my theory of water transport by Comstock (American Journal of Botany 86: 1077-1081) and by Stiller and Sperry (American Journal of Botany 86: 1082-1086) are acknowledged and reviewed. I make the following responses. (1) Tensile stresses to contain tissue pressure are kept within modest limits by the organization of vascular tissues into cylindrical bundles with small ratios of radius/boundary thickness. (2) The balance of pressures within tissues of a nontranspiring leaf is best understood by treating it as a single compartment containing several pressure-generating engines whose resultant is the pressure throughout the compartment. An error in the published notional balances for a transpiring leaf is corrected. (3) The argument against a valve in the transpiring leaf, which allows water out but not in, is not convincing. (4) The "robust and extremely consistent" cohesion theory gains this status by neglecting large bodies of experimental fact, once well known to plant physiologists. (5) The demonstration that living cells are not involved in the refilling of embolisms in birch stems is welcomed as an important advance. However, the major questions remain unresolved. (6) Proof is still needed that embolisms in vessels are not refilled by the collapse of gas bubbles under small positive pressures during conductance measurement. (7) The survival of unbroken water threads in vessels under centrifugal stress has still not been demonstrated. (8) Both questions 6 and 7 can be easily answered by direct observation of gas/liquid volumes in frozen stems in the cryo-scanning electron microscope.

Journal Article↗
PubMed2001

Embolisms and refilling in the maize leaf lamina, and the role of the protoxylem lacuna.

The proportion of embolized vessels in the veins of maize leaf laminas was measured during 24 h by direct counting in snap-frozen samples in the cryo-scanning electron microscope. All vessels were sap filled at night. Vessels of intermediate and small veins, and the small tracheary elements of lateral veins, were sap filled throughout the 24 h. The large metaxylem vessels of lateral veins were embolized during the day. The percentage of these vessels embolized was maximum (>70%) at 1400, and declined during the afternoon to 20% at dusk. Leaf water potential reached a minimum (-1.2 MPa) at dusk. The protoxylem lacuna of the lateral veins was much less embolized than the large vessels, although it was of comparable diameter. The observations are interpreted in terms of the refilling hypothesis that is part of the compensating pressure theory of water transport.

Journal Article↗
PubMed2000

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Aged↗
PubMed1991

Coronary blood flow reserve measured by contrast media injection depends on myocardial viability.

Coronary blood flow reserve may be affected by several physiological variables besides hydraulic impediment to flow. A hyperaemic response induced by hyperosmolar radiopaque contrast medium was recorded in the left anterior descending and left circumflex arteries with a steerable pulsed Doppler system in four patients with Q wave anterior myocardial infarction chronic scar and non-stenotic coronary arteries. Resting flow velocities were similar in both arteries. The magnitude of the hyperaemic response induced by contrast media in the circumflex artery (mean flow velocity increase from 5.9 +/- 2.5 baseline to 12.2 +/- 0.6 cm s-1 at peak flow, P less than 0.05) was almost twice that induced in the left anterior descending artery (mean flow velocity increase from 6.1 +/- 2.2 baseline to 7.4 +/- 2.6 cm s-1 at peak flow, P = N.S.). The peak flow to baseline flow velocities ratios were 1.22 +/- 0.15 in the left anterior descending artery vs 2.23 +/- 0.75 in the circumflex artery. Thus when a post-myocardial infarction chronic scar is supplied by a non-stenotic coronary artery, the coronary blood flow hyperaemic response to contrast media-induced transient ischaemia is decreased, suggesting that coronary blood flow reserve depends on a myocardial metabolic stimulus which is impaired by ischaemic cell death.

Adult↗
PubMed1989

Results of percutaneous valvuloplasty for calcific aortic stenosis with different balloon catheters.

Percutaneous aortic valvuloplasty is a palliative treatment for patients with calcific aortic stenosis who would be poor candidates for surgical treatment. The results and associated complications of this procedure were analysed in a series of 47 patients in which different types of dilating catheters were used. In 25 patients a single balloon (19 mm) was used (group A), in 13 patients a bifoil balloon (2 x 15mm) (group B), and in the remaining nine patients (group C) a trefoil balloon (3 x 10mm) was used. An increase in aortic valve area was achieved in all patients. The results obtained with the bifoil balloon were better than with the other types of balloon catheter, with an increase in aortic area of + 118% vs. + 74% (monofoil) and + 76% (trefoil) (P less than 0.05). The tolerance of the inflation procedure was also better with this type of balloon, as it allowed for shorter inflation and deflation times. These results show that balloon aortic valvuloplasty, when indicated, is best performed with a bifoil balloon dilating catheter, and undue complications usually do not occur.

Aged↗
PubMed1989

Diagnosis of coronary aneurysms in siblings: treatment with a new surgical procedure.

We report the cases of two brothers who simultaneously developed myocardial infarction, and in whom we found coronary artery aneurysms at echocardiography. In one case a new surgical procedure was performed. The aneurysm was bypassed by an aorto-coronary vein graft and the coronary ostium of the related coronary artery was closed. Thus, perfusion of the dependent vessels of the aneurysm was maintained, and the risk of distal embolism was prevented. The aetiologies of coronary artery aneurysms are discussed. In our patients the aneurysms were probably congenital, but we cannot exclude the possibility of previously undiagnosed Kawasaki's disease.

Adult↗
PubMed1989

[Evolution of the primary successes of percutaneous aortic valvuloplasty].

Between November 1985 and August 1988, we performed 89 percutaneous aortic valvuloplasties. Sixty-two of these were considered a primary success on the basis of two main criteria: stage I or II on discharge and greater than 50 p. 100 increase in aortic valve area. The mean age of these patients was 78.4 +/- 6.1 years. On actuarial analysis, after 5 months 98 p. 100 of the patients with primary success were alive and 89 p. 100 were in stage I or II and had not been operated upon or redilated. At 15 months 79 p. 100 of the patients with primary success were alive, but only 48 p. 100 were in stage I or II and neither operated upon or redilated. Ultrasonic data obtained one and twelve months after dilatation were compared in 8 patients who had kept the full functional benefit of angioplasty for 14.6 +/- 4.3 months (group 1) and 9 patients who had lost this initial benefit (group 2). In group 1 patients the aortic valve area had moderately and non significantly diminished from 0.92 to 0.72 cm2. In group 2 patients the aortic valve area had gone down from 0.89 to 0.63 cm2 (p less than 0.01), indicating restenosis. We conclude that after the 4th post-valvuloplasty month the medium-term success of the procedure undergoes some degradation, and in these patients the echocardiographic signs of stenosis are clear-cut.

Aged↗
PubMed1988

[Doppler study of phasic variations of blood flow velocity in the anterior interventricular artery].

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.

Angioplasty, Balloon↗
PubMed1988

[Treatment by redilatation and thrombolysis of occlusion occurring during percutaneous coronary angioplasty].

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.

Adult↗
PubMed1988

[Reproducibility of myocardial ischemia induced by atrial stimulation].

Reproducibility of myocardial ischemia induced by atrial pacing (P) was investigated in 25 patients (pts) without previous anterior myocardial infarction and showing a positive exercise stress test. The second period of atrial pacing (P2) was exerted 20 minutes after the first (P1). During P2, a reduction in the parameters reflecting myocardial oxygen requirements (maximal left ventricular pressure, dp/dt max, TTI*HR values) was noted, while the signs of ischemia were less pronounced (ST depression decreasing from 2.3 +/- 1 mm to 1.6 +/- 1.0 mm; % of lactate extraction (%L) decreasing from - 6.4 +/- 25.5 to + 8.5 +/- 19.2; p less than 0.5). The 25 pts were divided into 2 groups according to the ejection fraction (EF greater than .55 16 pts Gr.F+; EF less than .55 9 pts Gr.F-). The distribution of coronary lesions was the same for the 2 groups. During P1 GR.F+ registered a negative % L as opposed to Gr.F-. During P2, the difference in the % L between the 2 groups was also significant (2.6 +/- 19.9% F+ vs 18.9 +/- 14.3% F-; p less than .05). Collateral circulation had no effect upon the results, neither for P1 or P2. This study shows that a second period of atrial pacing, 20 minutes after the first, induced lesser ischemia than the first period of atrial pacing. This phenomenon could explain the paradoxical improvement observed in certain patients after a first episode of angina. These results have implications as regards the necessity of double blind studies compared to placebo when using this technique in the evaluation of the effects of anti-ischemic drugs.

Coronary Disease↗
PubMed1987

[Results of percutaneous valvuloplasty in calcified aortic stenosis in the adult].

Aortic valvuloplasty by percutaneous valve dilatation was attempted in 52 patients aged from 60 to 88 years, 20 of whom were in functional stage IV with pulmonary oedema at the time of the procedure. Forty-seven stenoses could be dilated, with haemodynamic success (50 p. 100 increase of aortic valve area) in 44 patients. Among these 44 patients, 3 had to be operated upon because of persistent functional symptoms and 3 died during their stay in hospital (2 as a result of the procedure or the cardiopathy, 1 of heart failure unrelated to the aortic stenosis or the dilatation). The primary success rate therefore was 38/52 attempts, or 72.9 p. 100. The first 11 patients regarded as initial success could be followed up for at least 6 months: functional improvement with moderate myocardial alteration persisted in 9 of them, but Doppler examination in one showed restenosis. Two patients with severe myocardial dysfunction relapsed into cardiac failure; restenosis could be dilated in one of them. Percutaneous aortic valvuloplasty is an effective treatment of calcified aortic stenosis in elderly people who remain improved for at least 6 months when myocardial lesions are mild or moderate. The procedure incompletely reduces the aortic stenosis, which may account for the left of improvement in left ventricular function in patients with severe myocardial damage prior to dilatation. For this subgroup of patients, the choice lies between percutaneous valvuloplasty, which avoids surgery, and surgery which ensures a more complete haemodynamic result in the valve.

Aged↗
PubMed1986

Percutaneous coronary angioplasty of a left anterior descending artery implanted on a Dacron coronary prosthesis on an aortic conduit.

Certain surgical techniques may make it difficult to catheterize the coronary ostia and perform percutaneous coronary angioplasty. We report the case of a 48 year old patient who developed unstable angina four years after a Bentall's procedure with reimplantation of the coronary arteries on a Dacron coronary prosthesis. The anginal pain was related to very severe stenosis of the proximal segment of the left anterior descending artery. The difficulties encountered during the dilatation procedure were due to: (a) the ectopic position of the ostium of the prosthesis on the anterior aortic wall; (b) the forces exerted on the aortic prosthesis wall and on the valvular prosthesis during positioning of the guiding catheter which were poorly tolerated and induced a vagal reaction; (c) the direction taken by the distal tip of the guiding catheter, perpendicular to the wall of the aortic prosthesis; (d) the sinuosity of the arterial trajectory: the left coronary segment of the coronary prosthesis was directed towards the left circumflex artery rather than towards the left anterior descending artery. Coronary angioplasty succeeded after relatively complex technical procedures: special guiding catheter, unusual intra-aortic manoeuvres for positioning the guiding catheter, dilatation catheter change on a 3-metre long guide wire in order to cross the stenotic segment; this was performed with a super low-profiled dilatation catheter. There were no complications and anginal pain disappeared.

Angina Pectoris↗
PubMed1986

[Phase variations in the left coronary transstenotic pressure gradient before and after dilatation by percutaneous coronary angioplasty].

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.

Adult↗
PubMed1984

[Interatrial septal aneurysm. Echocardiographic diagnosis].

Interatrial septal aneurysm is a rare abnormality and can now be diagnosed by echocardiography. We report the case of a 52 year old woman in whom this condition was diagnosed after an embolic cerebrovascular accident. M mode recordings showed a linear echo in the left atrial cavity in early and mid systole. The aneurysm was directly visualised by 2D echo as a hemispherical bulge in the mid portion of the interatrial septum, which was mobile and had a to-and-fro motion between the two atria in relation to the different phases of the cardiac cycle. The diagnosis was confirmed by angiography, and at surgery. A feature of this case was the close correlation between echocardiographic, angiographic and operative findings. The pathogenesis of this type of aneurysm remains conjectural as does its role in the production of cerebral embolism, the evidence for which was circumstantial in the absence of other demonstrable causes and in the light of previously reported cases.

Angiography↗
PubMed1984

[Differential diagnosis between constrictive pericarditis and cardiac amyloidosis by computerized M-mode echocardiography].

A diastole is a non specific haemodynamic syndrome which may result from constrictive pericarditis or from a restrictive cardiomyopathy. The aim of this study was to differentiate these two types of condition by analysis of computerised M mode recordings of the left ventricle. Three groups of patients were studied: 5 cases of confirmed cardiac amyloidosis (Am); 5 cases of constrictive pericarditis confirmed surgically (CP) and 10 normal subjects (NL). The study was based on analysis of parameters of ventricular filling and of diastolic thinning of the LV free wall. A significant difference was observed between AM and CP but not between PC and NL. Amyloidosis was characterised by a reduction in the maximum velocity of endocavitary diameter lengthening (AM 0,84 +/- 0,56 cir/sec; PC 3,95 +/- 0,77, p less than 0,01), prolongation of the rapid filling phase (AM 0,42 +/- 0,17 sec; PC 0,16 +/- 0,06 sec, p less than 0,02) and a decrease in maximum velocity of free wall thinning (AM 0,45 +/- 0,23 th/syst/sec; PC 4,79 +/- 2,1, p less than 0,01). The diastolic thickness of the free wall was greater in the amyloidosis group (AM 1,73 +/- 0,61 cm; PC 1,05 +/- 0,21, p less than 0,05) and correlated with the reduction of maximum velocity of free wall thinning. Parameters of global diastolic filling did not distinguish the two conditions. The M mode recordings were therefore digitalised to provide graphs of chamber filling and wall thinning and their derivatives.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

[Are post-infarction left ventricular aneurysms distensible? Volumetric study using angiography].

During left ventriculography, post-infarction left ventricular aneurysms present as diastolic deformations of the ventricular contour which, when accentuated during systole, give rise to paradoxical systolic expansion. The volumic consequences of thie parietal dyskinesia were studied in 10 cases of chronic anterior wall aneurysm. The borders of the aneurysm were determined by Watson's technique: diastolic and systolic volumes and endocardial surface areas were measured using a computer. In 9 out of 10 cases, neither volume nor endocardial surface area of the aneurysm varied from diastole to systole. Systolic distension of the aneurysm was observed in only one case. In the remainder, paradoxical systolic expansion was related to a charge in the shape of the aneurysm and to overall movement of the heart. The angiographic observations are important for the understanding of the physiopathology of post-infarction aneurysm and for choice of techniques for surgical treatment.

Adult↗