A comparison of the clinical relevance of thallium-201 and technetium-99m-methoxyisobutyl-isonitrile for the evaluation of myocardial blood flow.

Thallium-201 is at present the radiotracer of choice for the clinical evaluation of myocardial blood flow. Although different technetium-99m-isonitrile agents have been synthesised recently, only 99mTc-methoxyisobutyl-isonitrile (99mTc-MIBI) has proved to hold promise for clinical implementation. The myocardial distribution of 201Tl and 99mTc-MIBI was compared in a group of 20 patients, who underwent both 201Tl single photon emission computed tomography and 99mTc-MIBI study as well as coronary angiography. The sensitivity for predicting a lesion ranged from 25% to 88% in different areas of the heart and was comparable for the two radiopharmaceuticals. The specificity was greater than 80% for all regions except the inferior region where a specificity of 58% obtained by 99mTc-MIBI was better than the low specificity of 17% obtained with 201Tl (P less than 0.008).

99mTc ethoxy methylpropyl isonitrile: a radioactive tracer for myocardial perfusion imaging.

The initial experience with a new 99mTc labelled myocardial perfusion agent, ethoxy methylpropyl isonitrile (EMI), is described in the primate as model. Rapid biliary clearance of EMI ensures low radionuclide concentration in the liver and lungs after 60 min. Adequate visualization of the myocardium is therefore possible. Heart-to-lung and heart-to-liver ratios of 1.52 and 2.45 respectively were obtained. EMI is an efficient imaging agent to evaluate myocardial ischemia and infarction.

Intracoronary thrombolysis and coronary angioplasty for evolving myocardial infarction.

At present experience in South Africa with coronary reperfusion during the acute phase of myocardial infarction is limited. Acute reperfusion of an infarct-related coronary artery was attempted in 55 patients using intracoronary thrombolytic therapy and percutaneous transluminal coronary angioplasty (PTCA). Intracoronary streptokinase infusion had reopened 25 to 40 totally occluded lesions but usually a residual severe stenosis remained. PTCA was subsequently attempted in 36 severely stenotic coronary arteries and 19 totally occluded coronary arteries. PTCA was successful in 48 of the 55 cases (87%). After 1 week vessel patency was present in 36 of the 39 patients who had early coronary artery re-assessment. Late restenosis occurred in 4 out of 14 cases. There were no procedure-related deaths. Normal global as well as regional left ventricular function was present in 15 cases after 1 week. Emergency PTCA alone or in combination with intracoronary thrombolytic therapy is efficacious in achieving coronary reperfusion. On follow-up, left ventricular function appeared to be well preserved in 27% of patients with patent infarct-related arteries.

Daily serial evaluation of left ventricular function with equilibrium radionuclide ventriculography following thrombolysis during acute myocardial infarction.

The changes in ventricular function after reperfusion by coronary thrombolysis are important when deciding about further definitive treatment necessary to ensure long-term vessel patency. The purpose of this study was to evaluate the early changes in left ventricular function after reperfusion. Left ventricular function was serially evaluated for 10 days in a group of 18 patients receiving intracoronary thrombolytic therapy for an acute myocardial infarction. Comparison of the global ventricular function in the successfully and unsuccessfully reperfused groups of patients showed significantly better function in the successful group than the unsuccessful group after the first day, which was maintained for the entire study period. Global and regional ventricular function in the successfully reperfused patients showed significant early improvement during the initial 72 h with maintenance of this improvement for the study period of 10 days. In the patients in whom reperfusion was unsuccessful, regional ventricular function showed no change, while the global function declined from day 5 to day 8 of the study period. This study then confirms the significant improvement in ventricular function after successful reperfusion. The time course pattern of the change in ventricular function indicates that the most significant improvement occurs within the first 72 h after reperfusion. These changes are similar to those previously reported in experimental animals.

Myocardial bridging as a cause of myocardial infarction. A case report.

There is controversy over the clinical significance of myocardial bridging. A case of symptomatic bridging of the left anterior descending coronary artery resulting in myocardial infarction is reported.

Successful coronary reperfusion with intracoronary streptokinase in a patient with coronary ectasia.

A case in which successful coronary artery reperfusion was achieved during an acute inferior wall myocardial infarction by means of infusion of streptokinase (Kabikinase; Adcock Ingram) into an ectatic right coronary artery is described. The pathogenic mechanisms resulting in occlusion of ectatic coronary arteries and the incidence of the condition are discussed and the importance of anticoagulation therapy in these patients is stressed.

Absolute left ventricular volume changes after sublingual nitroglycerine and nifedipine intervention.

The haemodynamic effects of two vasodilators, sublingual nitroglycerine and nifedipine, on absolute end-diastolic volume, end-systolic volume, stroke volume (SV), heart rate, systolic blood pressure (SBP), cardiac output (CO) and corresponding cardiac indices were measured in two different groups, each consisting of 20 ischaemic heart disease patients, with gated blood pool scintigraphy. A control study was done in 5 ischaemic heart disease patients without intervention. Direct measurement of left ventricular (LV) volume was done by correcting LV activity for tissue attenuation utilising a geometric method. With nifedipine intervention only SBP (125.25 +/- 19.8 mmHg) showed a significant mean decrease (11 mmHg). The other measured parameters did not change significantly. With nitroglycerine all the parameters except LV ejection fraction showed significant changes. Mean CO decreased by 8% while mean SV decreased by 16%. The results in the control group showed excellent repeatability. The absolute haemodynamic changes of future cardiac drugs might easily be measured in vivo by this non-invasive technique.

Radionuclide evaluation of left ventricular function in a distantly located intensive coronary care unit.

Regular evaluation of left ventricular (LV) function is important in assessing patients in an intensive coronary care unit (ICCU). An adapted first-transit (FT) technique was applied to 21 patients for calculation of LV ejection fraction (LVEF). In this method the radionuclide is administered directly into the right pulmonary artery through a Swan-Ganz catheter. High-quality LV images are obtained because of minimal activity in the right ventricle and left lung. Data were acquired on a distantly located on-line computer system to restrict equipment in the ICCU. LVEF from FT compared well with LVEF from gated blood pool studies (r = 0.91) but gave consistently lower values. The adapted FT method ensures improved counting statistics during LVEF determination and facilitates evaluation of LV wall motion in the ICCU patient.

Left ventricular function evaluation using radionuclide methods in the intensive coronary care unit.

We describe an adapted first-transit (FT) technique to perform left ventricular ejection fraction (LVEF) measurements on patients with Swan-Ganz catheters in the intensive cardiac care unit (ICCU). The radionuclide is introduced directly into the right pulmonary artery through the catheter. High-quality images of the left ventricle are obtained owing to minimal activity in the right ventricle and left lung. LVEF measurements obtained by FT compared well with measurements obtained from gated blood pool studies (r = 0.91) but gave consistently lower values. The adapted FT method improves LVEF determination and left-ventricular wall motion evaluation in the ICCU patient.

Radionuclide determination of absolute LV volumes: interstudy, interobserver and intraobserver variances.

The results of 22 absolute left ventricular volume (LVV) determinations by a radionuclide (RN) method are compared to the results obtained by contrast ventriculography (CV). Another 10 patients were analysed in order to evaluate the interstudy, interobserver and intraobserver variances. Good correlation was shown between the RN and CV measurements of the end diastolic volume (EDV), end systolic volume (ESV), stroke volume (SV) and ejection fraction (EF), but the RN method overestimates the EDV and ESV. The EF was underestimated, but no difference could be shown for the SV. On the inter- and intraobserver levels, regression analysis yielded excellent correlation (r greater than 0.99 in all cases) with no statistically significant difference (P less than 0.05). The interstudy variance was minimal as indicated by regression analysis (r greater than 0.87) and no statistically significant difference (P less than 0.05) could be shown between studies. The results indicate that the RN method of LVV determination can be used in intervention studies over a limited period.

Traumatic aorta-vena cava fistula detected with radionuclide angiocardiography. A case report.

Diagnosis of a traumatic aorta-superior vena cava fistula in a 54-year-old man is reported, and the value of radionuclide angiocardiography in detecting and localizing the lesion is described.

Lysis of a coronary embolus by intracoronary streptokinase. A case report.

A patient presenting with an acute myocardial infarction, probably caused by a coronary artery embolus after aortic valve replacement, was treated by intracoronary thrombolysis with streptokinase. Restoration of antegrade flow in the previously totally occluded vessel was followed by an uncomplicated recovery and evidence of good preservation of left ventricular function.

Persistent left superior vena cava detected with radionuclide angiocardiography.

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.

Thrombolysis by intracoronary streptokinase infusion in patients with acute ischaemic syndromes.

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.

[Extensive endarterectomy of the left anterior descending artery]. / Uitgebreide endarterektomie van die afdalende tak van die linkerkoronêre arterie.

Diffuse obstructive disease of the left anterior descending coronary artery presents a new challenge to the surgeon especially if the heart and septal muscle supplied by this vessel is ischaemic but viable. Venous skips were utilized in the past to overcome this problem, but recently extensive endarterectomy of this system has been advocated. The case studies of 5 patients are presented who have undergone extensive endarterectomy of the left anterior descending artery and coronary bypass grafting.

Coronary artery bypass at the University of the Orange Free State Medical School. Medium-term follow-up of the first 100 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.

Variation in left ventricular ejection fraction determination at rest and during exercise.

The results of multi-gated blood pool imaging (MBPI) for determination of left ventricular ejection fraction (LVEF) in 48 patients at rest and during exercise were analysed in order to evaluate observer variance and interstudy variance. Twenty-three MBPI studies carried out with the patient at rest and 37 studies carried out during graded ergometer exercise were analysed by two independent observers in order to determine intra- and inter-observer variance. On the intra-observer level regression analysis yielded excellent correlation between rest and exercise studies (r = 0,998 at rest, r = 0,964 during exercise), and showed no statistically significant difference (P less than 0,01); this was also true of the inter-observer measurements (r = 0,999 at rest, r = 0,988 during exercise). In order to evaluate interstudy variance, MBPI was repeated in 15 patients at rest. Interstudy variation of the LVEF was minimal as indicated by regression analysis (r = 0,98), and showed no statistically significant difference (P less than 0,01). During the repeat study a mean increase in the LVEF of 2,1% was obtained, but this difference was not statistically significant.