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Biomedical subjects

J R See

Publications and source records attributed to J R See.

At least 19 recordsLinked to original sources
PubMed1979

Significance of reduced regional myocardial blood flow in asynergic areas evaluated with intervention ventriculography. Results of studies combining washout of xenon-133 and postextrasystolic potentiation.

Nineteen patients with coronary artery disease were studied to determine the significance of reduced regional myocardial blood flow (50 ml/min per 100 g or less) in areas of abnormal wall motion. Regional myocardial blood flow was measured in four regions of the left ventricle with an Anger camera after the injection xenon-133 into the left main coronary artery. Abnormal wall motion was evaluated with biplane left ventriculography at rest and during postextrasystolic potentiation, a potent inotropic stimulus. Abnormal wall motion was defined as hemiaxis shortening of less than 20 percent. Four hemiaxes were designated as corresponding to the four regions of myocardial blood flow. Of 76 hemiaxes evaluated in the 19 patients, 54 manifested normal wall motion and 22 abnormal wall motion; 8 of the 22 hemiaxes had reduced regional myocardial bood flow. In these 8, hemiaxis shortening increased 6 +/- 2 percent (mean +/- standard error of the mean) above values at rest during postextrasystolic potentiation (with normalization of hemiaxis shortening in only 1 of the 8), compared with an increase of 19 +/- 4 percent (P less than 0.001) in the 12 hemiaxes with borderline regional myocardial blood flow (with normalization of hemiaxis shortening in 9 of the 12, P less than 0.05). These results indicate that the presence of reduced regional myocardial blood flow in areas of abnormal wall motion usually predicts a poor response to post-extrasystolic potentiation, whereas abnormal wall motion without reduced regional myocardial blood flow usually predicts a good response. The combination of reduced regional myocardial blood flow and abnormal wall motion suggests scarred and nonviable myocardium.

Adult↗
PubMed1978

Regional myocardial blood flow in regions of prior myocardial infarction before and after revascularization.

In 30 patients who received 102 saphenous vein bypass grafts, 91 were patent. Preoperative intracoronary injection of 99mTc-labeled albumin particles suspended in contrast revealed 81 regions of perfusion deficit which subsequently received successful revascularization. With postoperative graft injection of isotope, 48 of these regions no longer showed a perfusion deficit (59%), while 33 showed no change (41%). In these 30 patients, 16 of 17 (94%) revealed perfusion defects in regions of prior transmural myocardial infarction. Conversely, only 55 of 96 regions distal to coronary artery stenosis of greater than 50% revealed perfusion defects (57%). Thus, 99mTc-labeled microsphere studies seem to be valuable in detecting regions of prior infarction. After angiographically documented revascularization, the method continued to reveal perfusion deficits in 41% of abnormal regions noted preoperatively, even though almost half of these same specific regions showed improved postoperative regional contractility after postextrasystolic potentiation.

Cardiac Catheterization↗
PubMed1977

Effect of sublingually administered nitroglycerin on regional myocardial blood flow in patients with coronary artery disease.

The effect of sublingually administered nitroglycerin on regional myocardial specific blood flow (in ml/min per 100 g tissue) was evaluated with a xenon-133 washout technique in 31 patients in a resting nonstressed state. Eight patients had normal coronary arteriograms (Group 1), 12 had coronary artery disease without collateral vessels (Group 2) and 11 had coronary artery disease with collateral vessels (Group 3). Although nitroglycerin caused a similar decrease in mean arterial blood pressure and blood pressure-heart rate product in all three groups, the decrease in regional myocardial blood flow was significantly less in Group 3 (-8+/-6% [mean+/-standard error of the mean]) than in Group 1 (-31+/-5%), P less than 0.05); an intermediary decrease occurred in Group 2 (-23+/-5%). Within Group 3, there was a mean increase in regional myocardial blood flow after nitroglycerin in the five patients whose collateral vessels were of a higher angiographic grade and arose from non-stenosed coronary arteries, whereas a reduction was observed in the six patients with none or only one of these findings (+10+/-7% versus -23+/-3%, P less than 0.001). This study suggests that even in the resting state, in some patients with coronary artery disease enhancement of regional myocardial blood flow can occur after sublingual administration of nitroglycerin and is probably mediated through well functioning collateral vessels. It is possible that the drug's effects on both the coronary and systemic circulation may relieve angina in some patients with coronary artery disease.

Administration, Oral↗
PubMed1977

Comparison between regional myocardial blood flow measurements and results of exercise tests.

The relationship between regional myocardial blood flow and the results of exercise tests were evaluated in 54 patients, 40 of whom had angiographically demonstrated coronary artery disease (CAD) and 14 had normal angiograms. After 20 patients had 2-step tests, 20 had bicycle ergometry, and 14 had treadmill tests, regional myocardial specific blood flow (RMBF) at rest was determined by selective injections of xenon-133 into the left coronary artery and quadrantic washout measured with an Anger camera. RMBF (ml/min/100 gm, mean +/- SE) was significantly lower in patients with coronary artery disease (72 +/- 3) than in normals (91 +/- 7, p less than .05) but RMBF in 12 CAD patients with negative exercise tests (75 +/- 6) was similar to regional myocardial blood flow in 28 coronary artery disease patients with positive exercise tests (71 +/- 4). Degree of ST depression did not influence results. Although measurement of RMBF and exercise testing are both useful procedures in the evaluation of patients with CAD, the data in the present study indicate the RMBF measurements at rest cannot predict the result of the postexercise ECG and vice versa.

Coronary Angiography↗
PubMed1976

Regional myocardial blood flow during hyperemia induced by contrast agent in patients with coronary artery disease.

Regional myocardial specific blood flow (regional specific flow) was measured at rest and during contrast hyperemia after the intracoronary injection of xenon-133. The changes in regional specific flow were transient, resulting in some compromise in one of the underlying restraints of the inert gas washout method, namely, the presence of a steady state. Therefore, to determine the clinical utility of this technique, regional specific flow values obtained with this method were correlated with the presence and severity of coronary artery disease as assessed from the coronary arteriogram and left ventriculogram. Regional specific flow during contrast hyperemia was 186+/- 11 (mean +/- 1 standard error of the mean) ml/min per 100 g in control patients and 115+/-5 in patients with coronary artery disease. There was an inverse relation between regional specific flow during contrast hyperemia and the percent coronary stenosis when the stenosis was 40 percent or greater (r = 0.70, P less than 0.001). Regional specific flow was significantly less in patients with asynergy (77 +/- 10 ml/min per 100 g) than in patients with normal ventricular function (105 +/- 5) distal to coronary stenoses of greater than 75 percent. Thus regional specific flow measured during contrast hyperemia using the xenon washout technique and the Anger camera differentiated patients with normal coronary arteriograms from those with coronary artery disease. With this technique, good correlation was shown between regional specific flow and the percent coronary stenosis and presence of ventricular wall abnormalities. The information obtained with this method may provide prognostic information concerning suitability for surgical intervention.

Angiocardiography↗
PubMed1976

Angiographic abnormalities associated with alterations in regional myocardial blood flow in coronary artery disease.

To evaluate the association between alterations in myocardial blood flow and angiographic findings, myocardial blood flow was compared in 26 patients with asymergy, 15 patients with a similar extent of coronary artery disease but without asynergy, and 10 patients without coronary artery disease or obvious myocardial or valvular disease. Myocardial blood flow was measured at rest with an Anger camera and PDP-11/20 computer after the intracoronary injection of 133xenon. In comparison with the normal subjects, whole heart blood flow was significantly reduced in patients with asynergy. In addition, myocardial blood flow in regions of anteroapical asynergy was reduced (85-7 +/- 7-0 ml/min per 100 g3 in controls to 65-4 +/- 4-5, P less than 0-05) and a similar reduction was noted in regions of posterolateral asymergy (91-5 +/- 8-8 in controls to 66-8 +/- 5-0, P less than 0-05). In general, regional myocardial blood flow was reduced distal to left anterior descending or left circumflex stenosis of less than 50 per cent, with a trend toward further reduction distal to less than 75 per cent stenosis. In these same patients, the presence of anteroapical or posterolateral asynergy resulted in a similar trend to even greater reduction of flow. The effect of collaterals was variable: 7 of 8 patients without asynergy but with less than 75 per cent left anterior descending stenosis and collateral circulation to the lower left anterior descending quadrant had minimally reduced flows. However, in the 17 patients with anteroapical asynergy, regional myocardial blood flow was very similar in the 9 patients with collaterals compared with the 8 patients without them. This study suggests that the degree of coronary artery stenosis and presence of asynergy are both important in evaluating alterations in myocardial blood flow in coronary artery disease, while the role of collaterals remains uncertain.

Adult↗
PubMed1975

Effect of direct revascularization surgery on coronary collateral circulation in man.

In 63 consecutive patients with significant coronary artery disease (more than 75 percent stenosis), the effects of direct myocardial revascularization on coronary collateral channels were studied 6 to 29 days (mean 13.4 days) after operation. Collateral vessels were identified preoperatively and their angiographic regression or reappearance after operation was noted. In 15 patients (23 percent), there was no evidence of collateral flow before or after operation. The remaining 48 patients had 186 collateral channels preoperatively. Postoperatively, 84 (45 percent) of these collateral vessels were no longer apparent, 75 (40 percent) were unchanged and 27 (15 percent) were identical with the preoperative vessels but the pattern of blood flow was reversed. The findings suggest that in the presence of established collateral channels, direct revascularization acutely alters existing flow and pressure gradients in a complex manner. Collateral channels disappear or remain unchanged when a gradient is decreased or maintained; collateral flow is reversed when a gradient is increased. These data may permit (1) objective preoperative estimation of distal vessel runoff in vessels with collateral channels, and (2) evaluation of the completeness of revascularization in assessing long-term postoperative results.

Collateral Circulation↗
PubMed1975

Left ventricular dyskinesia in infarction and angina.

In 29 patients, the site and extent of coronary artery obstruction were related to the position and area of abnormally contracting segments of the left ventricle, both in patients with a history of angina without myocardial infarction (group I) and in patients with prior documented myocardial infarction (group II). The degree of coronary artery obstructive disease was estimated in the standard manner and also by a coronary artery index which considered not only the degree of obstruction but also the total length of the obstructed segment. A kinetic or dyskinetic segments were present in 22 of the 29 patients. An abnormally contracting segment was present in 12 or 18 patients without prior myocardial infarction in comparison with 10 of the 11 patients with prior infarction. Complete obstruction of a coronary vessel and resultant dyskinesia were more frequent in the right coronary artery than in either the left anterior descending or the circumflex artery. There was a significant correlation between total per cent of vessel obstruction and degree of ventricular asynergy in both groups; consideration of length of obstructed segment did not improve this correlation.

Adult↗