Biomedical subjects
Publications and source records attributed to J D Marx.
A 28-year-old man presented with paresthesias, fatigue, central cyanosis, and erythrocytosis. A first pass flow study with Tc-99m as free pertechnetate was done, among other tests, to exclude a central shunt when a persistent left superior vena cava was incidentally detected. The value of radionuclide angiocardiography to examine the central circulation noninvasively was again illustrated in this case.
Intracoronary streptokinase was administered to 40 patients with acute myocardial ischaemic syndromes in an effort to restore antegrade flow in the affected vessel by thrombolysis. This was successful, with total occlusion of the vessel, in 66% of cases. Restoration of antegrade flow by the intracoronary administration of nitroglycerin was successful in only 1 case (2%). Subsequent study showed that re-occlusion of an initially patent vessel had occurred in 43% of cases and that recanalization had occurred in 62% of cases in which the vessel had initially remained occluded. Complications comprised reperfusion arrhythmias (55%), serious haemorrhage (8%) and reinfarction (8%). Intracoronary thrombolysis with restoration of antegrade flow was safely achieved in the majority of cases.
The increasing number of patients undergoing coronary artery bypass surgery has made the investigation and evaluation of the results of the procedure imperative. The first 100 patients who underwent this type of surgery at the University of the Orange Free State Medical School were followed up for a period of 3-8 years in order to obtain a prognostic pattern. The results of the study indicate that the procedure carries a low mortality rate and that the medium- to long-term results are encouraging. Eighty-one per cent of the patients are still actively pursuing their usual daily activities and 50% are completely free of symptoms.
Long-term therapy with oral labetalol, an alpha- and beta-blocking agent, has been shown to effectively lower blood pressure and heart rate without decreasing cardiac output. We examined the hemodynamic effects of the acute intravenous administration of labetalol in nine hypertensive patients. Labetalol (0.6 +/- 0.1 mg/kg) promptly reduced arterial pressure, heart rate, and systemic vascular resistance without change in stroke volume. Heart rate responses to passive tilt and the Valsalva maneuver were significantly blunted. With isometric exercise, heart rate and mean arterial pressure increased significantly during labetalol therapy but less than in the pre-labetalol phase. In eight patients oral labetalol therapy was continued for six weeks (mean dose 1,050 +/- 105 mg/day), and hemodynamic evaluation was repeated. During oral labetalol therapy, decreases in arterial pressure and heart rate were sustained. Systemic vascular resistance was reduced in five of the eight patients. Hemodynamic responses to tilt, Valsalva maneuver, and handgrip were similar to those during intravenous administration. Coronary blood flow decreased, but coronary as well as pulmonary vascular resistances were unchanged. These data show the efficacy of intravenously administered labetalol in lowering blood pressure and systemic vascular resistance promptly. With long-term oral therapy, decreases in blood pressure are sustained. Labetalol does not appear to have significant effects on pulmonary or coronary vascular resistances.
The use of 81mKr was investigated for imaging myocardial perfusion during coronary arteriography using conventional catheters. When the significance of stenosis judged by arteriography is unclear, the effect on tissue perfusion can be established and the contribution to collateral flow by each artery separately evaluated. The distribution of 81mKr, due to its 13-s half-life, represents regional blood flow. In order to evaluate interventions, studies can be repeated at a low radiation risk to patients. A sterile pyrogen-free 81Rb-81Kr generator was developed. With slow infusion, inadequate mixing and streaming takes place due to laminar flow in coronary arteries. Fast intermittent 3-ml 81Kr-dextrose bolus injections convincingly eliminated streaming artefacts. Imaging was performed in 13 patients with a mobile scintillation camera and digital imaging system. Blood flow was calculated using the inert gas washout technique. There was good correlation (r = 0.91) between coronary blood flow determinations using 81mKr and 133Xe respectively. The perfusion images correlated well with the coronary angiograms. Total coronary arterial occlusions as demonstrated by arteriography were all shown as perfusion defects during rest. During atrial pacing myocardial flow was increased two-fold in normal coronary arteries and to a lesser extent in arteries with significant disease. The most critical lesion in a branch of a left coronary artery leads to a redistribution of perfusion during pacing.
The responses to cold in patients with exertional chest pain were studied by measuring coronary sinus and great cardiac vein flows, aortic and left ventricular pressure and diameters of epicardial and small (0.4 to 1.0 mm) intramyocardial coronary arteries before and after the left hand of 18 such patients was immersed in ice water. Coronary sinus and great cardiac vein flows were used as indexes of total and anterior left ventricular flows. Coronary sinus flow minus great cardiac vein flow was used as an index of inferior left ventricular flow. Perfusion of left ventricular regions was considered potentially "normal" or "abnormal" according to the presence or absence of 50 percent or greater stenosis of luminal diameter in the coronary artery supplying a given region. With cold stimulation, increases occurred in heart rate (6 beats/min), mean aortic pressure (22 mm Hg) and left ventricular end-diastolic pressure (8 mm Hg) (all p less than 0.05). Left ventricular flow in normally perfused regions increased as resistance decreased. Left ventricular flow in abnormally perfused regions increased slightly and resistance increased. Regional left ventricular flow increased more, and changes in resistance differed in normally and abnormally perfused regions. Coronary arterial diameter decreased only minimally (6 percent) in both normal and abnormal left ventricular regions. These data show that cold stimulation increases coronary resistance in abnormally perfused left ventricular regions. Cold stimulation-related increases in coronary resistance do not appear to be caused by coronary arterial "spasm."
We studied the degree of coronary artery dilation resulting from increasing doses of intracoronary nitroglycerin (NTG). Heart rate, aortic pressure and coronary artery angiograms were recorded before and after 5-, 50-, 150- and 250-microgram doses of NTG infused into the left main coronary artery. Coronary artery diameters were measured by a magnification angiographic technique. After intracoronary NTG, heart rate was unchanged 2 minutes after each dose. Mean aortic pressure was unchanged after 5 microgram (NS), but declined 5 mm Hg (mean) after 50 microgram, 9 mm Hg after 150 microgram and 18 mm Hg after 250 microgram (all p less than 0.05) compared with before NTG. The maximal increase in diameter occurred after 150 microgram, and no additional increase was seen after 250 microgram. After 5- and 50-microgram doses, 67% and 75% maximal dilation responses, respectively, were observed. Compared with coronary artery diameter before NTG, the 150-microgram dose increased the diameter of left main coronary artery by 5%, proximal coronary artery segments by 9%, middle segments by 19%, distal segments by 34%, collateral-filled coronary arteries by 38%, coronary artery stenoses by 5%, and small coronary arteries (0.4-1.0 mm) by 54%. These data indicate that relatively small doses of intracoronary NTG produce potentially important coronary artery dilation without important changes in heart rate and aortic pressure. These observations should prove helpful in choosing dosage schedules for intracoronary NTG.
Radionuclide left ventricular ejection fraction (LVEF) has been determined in a group of 14 female patients at rest and during graded supine bicycle exercise. One group consisted of 9 patients complaining of chest pain and demonstrating positive exercise electrocardiography (EECG), but with normal contrast angiographic results. The second group of 5 patients had a normal response to EECG and was used as a control group. LVEF increased markedly in both groups during exercise. This study confirms the known fact of high false-positive EECG in female patients and that exercise radionuclide LVEF response can be used as a final screening test for cardiac catheterization in female patients demonstrating positive EECG.
The electrocardiographic findings and certain biochemical observations in 48 male runners before and after participation in the Comrades Marathon race are presented. In 21 of the 48 runners electrocardiographic changes consistent with early ischaemic heart disease could be demonstrated before the race. In 2 runners who had normal tracings before the race, abnormalities could be shown after the race. The total serum creatine kinase activity was markedly elevated after the race in the majority of the 23 runners in whom this was measured. In 11 of these subjects, the Marsh-Bender (MB) fraction could be demonstrated after the race. It is concluded that an elevated MB fraction is probably not a reliable index of myocardial damage after strenuous exercise.
This article discusses the use of a medication kit at home for terminal symptoms. This innovation has been in place for more than two years at the Hospice of the Cleveland Clinic. There is no previously published information on this innovation in the literature.