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Biomedical subjects

A S Most

Publications and source records attributed to A S Most.

At least 73 records · Page 4Linked to original sources
PubMed1980

Restoration of normal coronary hemodynamics and myocardial metabolism after percutaneous transluminal coronary angioplasty.

Regional coronary blood flow and myocardial metabolism were evaluated in a patient who underwent percutaneous transluminal coronary angioplasty (PTCA). Angioplasty increased coronary luminal diameter and reduced trans-stenotic gradient. Before PTCA, angina pectoris developed during sustained rapid atrial pacing and was associated with abnormal lactate metabolism and a mild increase in coronary flow and myocardial oxygen consumption. After PTCA, angina was absent during pacing and lactate extraction was preserved. Coronary flow and oxygen consumption were increased to a greater degree than before PTCA. The temporal response of changes in coronary blood flow due to an abrupt increase in heart rate was also evaluated. Floow reached peak value more rapidly after PTCA. These observations suggest that PTCA may result in improved regional coronary blood flow and restoration of normal flow regulatory mechanism and myocardial metabolism.

Angina Pectoris↗
PubMed1979

Significance of the negative exercise test in evaluation of patients with chest pain.

Fifty-three patients with chest pain and a negative exercise test at greater than 85% predicted maximal heart rate underwent coronary arteriography. Twenty-one patients (40%) had significant luminal narrowing in one or two vessels. No patient had left main disease. Pathologic electrocardiographic Q waves were present in only coronary heart disease patients (p less than 0.001). There was no difference (p greater than 0.05) in prevalence of T wave abnormalities, chest pain or ventricular beats during exercise in patients with or without coronary disease. Analysis of sex distribution revealed that typical angina pectoris was uncommon in the women (p less than 0.001) and all twenty-one coronary patients were men (p less than 0.001). We conclude that in patients with chest pain and a negative exercise test, three vessel or left main coronary artery disease is unlikely. Also, women with atypical chest pain and a negative exercise test are unlikely to have a fixed coronary obstruction.

Adult↗
PubMed1979

The single precordial lead for ST segment monitoring: comparison with the multiple lead map.

ST segment elevation, used as an index of the relative extent of myocardial ischemic injury, was measured using a single precordial lead located at the point of maximum ST elevation. ST changes were followed for two hours after acute coronary occlusion in pigs, and were compared to the sum of ST elevation recorded with an 18 lead precordial map. Some animals were subjected to Reperfusion (n = 12), others to infarct extension (n = 10), while a control group (n = 9) was followed without an ST-modifying intervention. Correlation between sigmaST and ST in the single lead was good, with a correlation coefficient of 0.844 at 360 points of comparison. Time to peak ST elevation using the single lead technique was comparable to that using the 18 lead map. Changes in the ST elevation using both techniques were similarly reduced following reperfusion, increased following extension, and followed a similar downslope pattern in the unmodified infarct group. This single lead technique offers the advantage of simplicity of use without sacrifice of accuracy. Its use can facilitate clinical studies of myocardial ischemic injury and its modification.

Animals↗
PubMed1979

Effective treatment of supraventricular arrhythmias with acebutolol.

To evaluate the antiarrhythmic efficacy of the new beta adrenergic blocking agent acebutolol, 15 monitored patients with supraventricular arrhythmias received, in double-blind fashion, an intravenous infusion of either acebutolol or saline solution after a control period. Patients treated with saline solution demonstrated no change (P greater than 0.05) in heart rate or arterial blood pressure or conversion to sinus rhythm. After administration of acebutolol, significant (P less than 0.05) reductions in heart rate were noted at 5 minutes. Peak reduction occurred at 10 to 30 minutes and correlated with maximal acebutolol plasma concentrations, antiarrhythmic activity persisted for 24 hours. Mild reductions in systolic blood pressure were observed in the majority of patients. Two patients with atrial fibrillation and one with multifocal atrial tachycardia had conversion to sinus rhythm. Frequent premature atrial complexes noted in one patient were greatly suppressed after administration of the drug. In the nine patients with clinical evidence of chronic obstructive lung disease acebutolol was well tolerated. Adverse reactions were limited to transient dyspnea in one patient with prior heart failure and a decrease in systolic blood pressure to less than 90 mm Hg in three patients who remained asymptomatic. In the patients studied, acebutolol was an effective agent for the treatment of supraventricular arrhythmias and appeared to be of special value in those with chronic obstructive lung disease.

Acebutolol↗
PubMed1978

Acute coronary occlusion in the pig: effect of nitroglycerin on regional myocardial blood flow.

Myocardial blood flow was studied in 10 closed chest, anesthetized pigs after an acute balloon catheter occlusion of the left anterior descending coronary artery. With use of radioactive microspheres (15 mu), myocardial blood flow was measured before and during an intravenous nitroglycerin infusion and during a combined nitroglycerin-phenylephrine infusion. A significant zone of ischemis (myocardial blood flow less than 50 percent of normal zone flow) was produced by the occlusion and involved 15 percent of the combined left ventricular and interventricular septal mass. More than 50 percent of this ischemic zone was intensely ischemic (myocardial blood flow 0 to 3 percent of normal). Nitroglycerin resulted in a 20 to 30 mm Hg decrease in systolic blood pressure. Myocardial blood flow was unchanged in intensely ischemic areas but varied directly with the product of heart rate and systolic blood pressure in the moderately ischemic area (myocardial blood flow 26 to 50 percent of normal). S-T segment elevation was significantly increased during nitroglycerin infusion and returned to control level with the added infusion of phenylephrine sufficient to restore the systemic blood pressure to prenitroglycerin values. No improvement in ischemic zone perfusion could be demonstrated during the infusion of nitroglycerin alone or with phenylephrine. The endocardial-epicardial flow ratio in moderately ischemic areas was slightly lower than the normal zone flow ratio and decreased slightly during infusion of nitroglycerin. With the addition of phenylephrine, the ratios rose slightly and no longer differed from prenitroglycerin values. Blood flow distribution in acutely ischemic pig myocardium differs considerably from that observed in the dog. Nitroglycerin was not shown to have any beneficial effects with or without its relative hypotensive effect. More extensive study in animal models other than the dog is needed.

Animals↗
PubMed1977

Complete heart block as a cause of syncope in asymmetric septal hypertrophy.

This case report presents a young adult with asymmetric septal hypertrophy (ASH) and syncope. Infranodal complete heart block was demonstrated as his cause for syncope. Therapy consisted of implantation of a A-V sequential pacemaker. Cardiac output determinations and systolic time intervals demonstrated the beneficial effects of properly timed atrial contractions.

Adult↗
PubMed1977

Free fatty acids and arrhythmias following acute coronary artery occlusion in pigs.

The arrhythmogenic potential of elevated serum free fatty acids (FFA) was investigated in closed-chest pigs following acute coronary artery occlusion. Animals both with and without ventricular irritability before the FFA rise were studied. No significant increase in PVC frequency occurred and only 1 out of 17 animals developed ventricular fibrillation in the 60 min following acute FFA elevation. In this situation, FFA did not significantly influence the appearance of arrhythmias.

Animals↗
PubMed1976

Failure of hyaluronidase to alter the early course of acute myocardial infarction in pigs.

The effect of hyaluronidase on the early course of acute myocardial infarction was evaluated in closed chest anesthetized pigs. One hour after balloon catheter occlusion of the left anterior descending coronary artery, hyaluronidase (500 units/kg body weight) was rapidly infused in 10 animals while 9 received no treatment. The animals were than observed over the next 4 hours. Cardiac output, heart rate, mean arterial pressure and left atrial pressure were not significantly affected by treatment. Heart rate increased and arterial pressure decreased in each group to a comparable degree of 5 hours, but left atrial pressure and cardiac output were unaffected. Precordial S-T segment mapping revealed no significant difference between the two groups. S-T segments rose to a comparable degree in each group and peaked before 1 hour. Hyaluronidase had no acute effects on the S-T segment map in the first 30 minutes after infusion or during the subsequent return of the map toward control level. Slightly lower S-T segments in the hyaluronidase-treated group at 5 hours was of borderline significance but was attributed to factors other than the drug intervention. Changes in ventricular wall motion were assessed angiographically, and all animals manifested akinetic or dyskinetic segments. A significant reduction in shortening fraction of involved segments was seen after occlusion, but no difference was observed between the two groups at 5 hours. Shortening fraction of the combined anterior and anteropical segments decreased from 66 +/- 10 to 20 +/- 6 percent at 5 hours in the hyaluronidase group (no. = 7) whereas in the control group (no. = 6) it decreased from 68 +/- 6 to 28 +/- 9 percent. Comparable increases in end-diastolic volume were also present at 5 hours in each group. Volumes increased from 80.6 +/- 5.1 to 97.5 +/- 6.4 ml3 at 5 hours (P less than 0.05) in the hyaluronidase-treated group (no. = 10) compared with 86.9 +/- 8.9 to 104.8 +/- 11.0 ml3 (P less than 0.05) in the control group (no. = 8). Hyaluronidase did not alter the early course of acute myocardial infarction in pigs. Species differences may contribute to different results reported to date.

Acute Disease↗
PubMed1975

Precordial ST segment mapping. A sensitive technique for the evaluation of myocardial injury?

Myocardial ischemic injury was created acutely in pigs by a closed-chest technique utilizing an intracoronary balloon occluder for the interruption of flow in the left anterior descending coronary artery and ST-segment elevation was followed over a two hour period using an 18 lead precordial map. In an experimental group of 10 animals, occlusion was carried out within the left anterior descending coronary artery 8.3 plus or minus 0.5 cm distal to the origin of the main left coronary. Mean ST segment elevation (ST) showed a peak rise of 0.16 mV 10 minutes after occlusion. The balloon was moved proximally 1.6 plus or minus 0.2 cm giving a significant secondary rise of 0.16 mV within 5 minutes, despite indications of a generally small area of additional myocardial involvement, as judged from anatomic distribution of additional vessels occluded as well as a lack of significant change in hemodynamic parameters. In a control group of 5 additional pigs, a single distal occlusion at 6.4 plus or minus 0.9 cm from the origin of the main left coronary was produced by an identical technique. The ST rose to a peak of 0.20 mV at 15 minutes and was followed by a steady decline. Unlike the experimental group, no additonal rise in ST was seen. The technique of precordial mapping thus appears to be a sensitive index of myocardial injury. In addition, it appears from this study that the magnitude of ST elevation is a direct reflection of the extent of myocardial injury.

Animals↗
PubMed1974

Failure of free fatty acids to influence degree of myocardial injury following acute coronary artery occlusion in pigs.

Elevation of circulating free fatty acids (FFA) has been implicated as a deleterious influence during conditions of myocardial ischemia. To further explore this question, acute coronary artery occlusion was produced in closed-chest, anesthetized pigs. FFA levels were elevated by injecting heparin and then infusing a lipid emulsion at 1 or 2 h following occlusion. Precordial ECG mapping was used to assess the degree of myocardial injury. At both 1 and 2 h following occlusion the lipid infusion elevated the mean FFA level to over 2,500 muM. ST segment levels failed to indicate any concomitant increase in degree of myocardial injury. By contrast, an isoproterenol infusion (30 min, 4-8 mug/min) under similar conditions did result in ST segment changes suggestive of extended myocardial injury. Augmented arterial FFA levels do not influence the degree of myocardial injury following acute coronary artery occlusion.

Acute Disease↗