Unsuitability of evacuated tubes for monitoring heparin therapy by activated partial thromboplastin time.

Activated partial thromboplastin times (APTT) for monitoring heparin therapy for venous thromboembolism tended to be inappropriately short if blood was collected in commercially available evacuated glass tubes. Five types of evacuated tubes marketed under the trade names Vacutainer and Venoject were examined. The APTT of heparinized blood collected in these tubes correlated poorly (r = 0.04 to 4 = 0.25) with that of blood samples from the same patients collected in plastic tubes. Most of the evacuated tube APTT were shorter than that of blood collected in plastic or siliconised glass tubes, but the results were unpredictable and varied from tube to tube and from batch to batch. This effect on heparin is apparently due to an unidentified substances which is eluted from the rubber stoppers of the tubes. Heparin control according to the APTT blood collected in these evacuated tubes is hazardous.

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.

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.

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.

A correlative study of serum digoxin levels and electrocardiographic measurements.

The ST-segment appearance, PR interval, corrected QU time and T-wave amplitude from standard electrocardiograms of 70 patients were correlated with serum digoxin levels done on the same day. The absence of a digtalis effect on ST segments, upright T waves and PTQ scores (a combination function of PR, QT and T) of one or less, correlated well with the absence of "toxic" serum digoxin levels (greater than 1,8 ng/ml). PTQ scores showed a significant linear correlation with serum digoxin levels, and PTQ scores of more than 3,0 were in all instances associated with "toxic" serum digoxin levels. These observations merit futher investigation and could be useful in clinical situations.

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.

Global and regional assessment of cardiac performance by ECG-gated radionuclide blood pool imaging.

A non-invasive method for evaluation of regional and global ventricular function by ECG-gated radionuclide blood pool imaging was developed. Cinematic image display is a sensitive method for evaluating wall motion to detect regional ventricular abnormalities and chamber size. A value of r = 0,86 and 0,85 was found for both fixed and variable area radionuclide methods when these ejection fraction values were correlated with cardio-angiographic ejection fraction values in normal subjects and in patients with myocardial infarction. The fixed area method underestimated the ejection fraction in patients with mitra valve stenosis, but this problem can be overcome with the variable area method. The technique developed cannot be used in patients with severe arrhythmias (r = 0,49 and 0,44).

[Intracoronary thrombolysis. A case report]. / Intrakoronêre trombolise. 'n Gevalbespreking.

Restoration of blood flow in an occluded right coronary artery of a patient with an acute myocardial infarction was achieved with intracoronary administration of streptokinase. Patency of the vessel was restored within 15 minutes after starting the infusion. The dose of streptokinase used was 3000 U/min. The patient's pain was relieved and the raised ST segments returned to normal after patency was achieved. Cardiac output and stroke volume increased fro 3,6 to 6,3 1/min and from 61 to 70 ml respectively. No complications occurred during the infusion of streptokinase. Intracoronary thrombolysis might well establish itself as the treatment of choice for acute myocardial infarction in selected patients.

Coronary artery bypass surgery at the University of the Orange Free State Medical School.

Fifty patients underwent aortocoronary bypass grafting, and 48 of these survived and are alive at present. Seventy-four per cent of these patients were relieved of angina, 16% were improved, and 10% remained the same, and 72% of these patients have resumed their normal daily work. The morbidity of the operation was negligible. The problems that emerged in this small series were involvement of the perforator artery, sudden occlusion of a major vessel during coronary angiography, preservation of the myocardium during surgery for multiplevessel disease, and lastly the question of when a ventricle is too damaged to be operated on. These problems are discussed and suggestions are made as to how to handle them. On the whole, we see this procedure as a useful adjunct in the treatment of occlusive coronary artery disease.

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.

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.

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).

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.

[Cycling, fitness and the prevention of ischemic heart disease]. / Fietsry, Fiksheid en die voorkoming van iskemiese hartsiekts.

A short review of the prevalence of ischaemic heart disease in South African Whites is given, and primary prevention, which entails an alteration in life style, is emphasised. The role of increased physical activity in primary prevention is discussed. Any programme to increase the fitness status of a population based on activities that must be performed outside the daily routine, willhave limited impact. The possible role of cycling is discussed and it is shown that ordinary cycling to work probably causes sufficient stimulation of the cardiovascular system to produce an acceptable standard of physical fitness.

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.

Determination of right ventricular ejection fraction utilising a radionuclide washout technique.

A radionuclide washout technique (WO), for calculation of the right ventricular ejection fraction (RVEF) which is independent of the exact position of the right ventricular region of interest was evaluated and results compared with first pass (FP) and equilibrium gated blood pool (GBP) values. Regression analysis between RVEF values of 24 patients obtained from FP and WO yielded a correlation coefficient (r) of 0.89, while a slightly poorer correlation coefficient was obtained when FP and GBP were compared (r = 0.79) and between WO and GBP (r = 0.71). No significant difference between RVEF values calculated from the three techniques was found (P less than 0.05) on inter- and intraobserver level. The radionuclide washout technique yields an accurate determination of RVEF without the necessity of outlining the RV accurately.

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.

The imaging of myocardial perfusion with 81mKr during coronary arteriography.

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.