Biomedical subjects
B H Roberts
Publications and source records attributed to B H Roberts.
Student nurse ambassadors spark interest in recruitment.
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Coronary-artery spasm and myocardial infarction associated with cocaine use.
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Beneficial effect of dexamethasone on the "no reflow" phenomenon in canine myocardium.
The purpose of the present study was to determine if pretreatment with dexamethasone 6 mg.kg-1 would preserve coronary artery blood flow during reperfusion, thus preventing the no reflow phenomenon. Blood flow to small segments of the left ventricle was measured by the use of 15 micrometer tracer microspheres in intact dog hearts. During 2 hours of occlusion of the anterior descending coronary artery by balloon catheter, dexamethasone produced a small increase of the blood flow to perfused myocardium, when compared with untreated animals; this effect was not seen in underperfused segments of the myocardium. In nontreated animals, reperfusion of the underperfused portion of the left ventricle did not lead to a restoration of flow to normal when measured 1 hour later. In fact, the "no reflow" phenomenon resulted in a post reperfusion left ventricular segment which was similar to that measured during coronary arterial occlusion. However in the dexamethasone treated animals there was a decrease in the extent of left ventricular underperfusion from 19 to 6%. It is concluded that dexamethasone protects the border zone of canine myocardium during occlusion, and prevents the no reflow phenomenon in underperfused regions during reperfusion
Evolution of left ventricular dysfunction in coronary artery disease. Serial cineangiographic studies without surgery.
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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.
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.
Angina pectoris. Diagnosis and treatment.
The physician who understands the pathophysiology of angina pectoris can apply rational therapeutic measures based on an appreciation of the determinants of myocardial oxygen supply and demand. Most patients with angina secondary to coronary atherosclerosis can be treated conservatively using a systematic approach that includes correction or removal of underlying causes or precipitating factors and the judicious use of sublingual nitroglycerin. In patients with more resistant angina, use of oral or topical nitroglycerin or sublingual isosorbide dinitrite as well as propranolol can be advised. Aortocoronary bypass surgery can offer significant improvement in carefully selected patients with frequent angina poorly controlled by medical therapy. The most important consideration in the treatment of angina is protection of coronary blood flow reserve by primary prevention of the atherosclerotic process itself. All individuals from families prone to coronary artery disease should be evaluated for alterable risk factors, the most important being cigarette smoking, hypertension, and hypercholesterolemia. Considering the high risk of unheralded sudden death in previously asymptomatic patients with coronary atherosclerosis, angina can, in a sense, be considered a fortunate harbinger of coronary stenosis, identifying candidates for secondary preventive measures aimed at retarding the progression of vascular disease. More importantly, angina serves as an index for detecting families at high risk of coronary artery disease, in whom early application of primary prevention may afford a more promising outlook.
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.