An experimental study of cardiac contractile force in myocardial infarction

The host-parasite relationship of HeLa M cells artificially infected with a bovine species of Mycoplasma was studied by light microscopy, transmission electron microscopy and scanning electron microscopy. The use of morphometry to quantitate some of the findings was explored. The parasites were seen in locations extracellular to the cell surface. The detection of small numbers of organisms by light microscopy was well demonstrated by use of the flurescent antibody technique. Scanning electron microscopy proved to be an excellent method for revealing the surface details of cell-parasite morphology. Ultra-thin sections showed that the parasites are aligned mostly parallel to the plasma membrane of the host cell but separated by a gap of 10nm. Morphometry indicated an average of 69 organisms per cell surface occupying 1.7% of the surface area. An increase of 26% in diameter of the HeLa cells, possibly as a result of infection, was observed.     

Transfer anxiety in patients with myocardial infarction

When patients are transferred from a coronary care unit to a general ward they often experience transfer anxiety. A structured pre-transfer teaching programme is suggested as a tool which may improve patient care.     

Impaired expression of atrial natriuretic peptide in diabetic rats with myocardial infarction

We evaluated the effects of myocardial infarction (MI) on the hemodynamics and the expression of atrial natriuretic peptide (ANP) mRNA in rats with streptozotocin-induced diabetes. Eight weeks after streptozotocin injection, the diabetic rats and age-matched nondiabetic controls underwent coronary artery ligation. One week later, the left ventricular end-diastolic pressure, systolic blood pressure, infarct size, and serum ANP levels did not differ significantly between the diabetic and nondiabetic rats. Compared with control animals without MI, the atrial ANP/beta-actin mRNA ratio in rats with MI was increased to 195% in diabetic animals and 213% in nondiabetic animals. In the left ventricle, however, the ANP/beta-actin mRNA ratio in diabetic animals with MI was increased to only 131% compared with control animals, whereas the corresponding increase in nondiabetic animals was 240% (p<0.05). Thus, the modulation of ANP mRNA expression after MI was impaired in the left ventricle, but not in the atria, of diabetic rats. A reduced myocardial expression of ANP could increase the morbidity and mortality associated with cardiovascular disorders in patients with diabetes.     

Wall thickening at rest and contractile reserve early after myocardial infarction: correlation with myocardial perfusion and metabolism

BACKGROUND: Abnormalities in wall thickening and their reaction to stimulation can be studied by magnetic resonance imaging. OBJECTIVE: To analyse the relationship between these abnormalities and changes in myocardial perfusion and fatty acid metabolism. METHODS: Fifteen patients with a myocardial infarction underwent low-dose dobutamine magnetic resonance imaging to assess their wall thickening and contractile reserve, and technetium-99m sestamibi (MIBI) and beta-methyl-iodophenyl-pentadecanoic acid (BMIPP) single-photon emission tomography to assess their myocardial perfusion and fatty acid uptake. For nine segments per patient, the wall thickening was scored as normal, hypokinetic or akinetic, and the myocardial perfusion as normal (> 65%), mildly to moderately reduced (35-65%) or severely reduced (< 35%). Abnormalities in fatty acid uptake were compared with the myocardial perfusion and defined as matched (difference < or = 10%) or mismatched (difference > 10%) reduction. RESULTS: Thirty-four segments had abnormal wall thickening (13 hypokinetic and 21 akinetic). The wall thickening at rest was significantly related to the uptake of MIBI (P < 0.001), but not to abnormalities in the uptake of BMIPP. All of the akinetic segments had an abnormal uptake of MIBI (15 severely and six mildly to moderately reduced), whereas 7 of 13 hypokinetic segments had a normal and five a midly to moderately reduced uptake. A significant relationship between abnormalities of fatty acid metabolism and the contractile reserve was also found (P < 0.002): 14 of 16 segments with and only six of 18 without contractile reserve had a mismatched reduction in uptakes of MIBI and BMIPP. CONCLUSION: This study confirms the relationship between the wall thickening at rest and the residual perfusion after infarction. On the other hand, the contractile reserve, which is an accepted indicator of the viability of the infarct region, is associated strongly with abnormalities of fatty acid metabolism.     

Warfarin reduces silent cerebral infarction in elderly patients with atrial fibrillation

A simple, fast, reliable, and specific immunoassay has been developed to detect and measure AD7C-NTP, a biochemical marker for Alzheimer's disease, in cerebrospinal fluid (CSF). This assay, called the AD7C Test, is an enzyme-linked sandwich immunoassay (ELSIA) using 96 well microtiter plates. The plate surface is coated with a monoclonal antibody (N3I4) which has a high affinity and specificity for AD7C-NTP, capturing it effectively from CSF samples. The detection was achieved using a polyclonal antibody (ADRI). Both N3I4 and ADRI were generated using recombinantly produced AD7C-NTP. The assay is highly sensitive (30-50 pg), linear to 2.0 ng (r2 > 0.99), and reproducible (C.V. < 10%). The utility of the assay has been demonstrated using CSF specimens from early Alzheimer's disease patients and age matched controls (sensitivity of 89% and specificity of 89%).     

Right ventricular radiofrequency ablation of ventricular tachycardia after myocardial infarction

Radiofrequency transcatheter ablation of ventricular tachycardia in the setting of a prior myocardial infarction is typically performed with application of energy to the left ventricular endocardium. In this article, two cases are described in which successful radiofrequency transcatheter ablation of ventricular tachycardia occurred with energy delivery to the right ventricular septum after failed ablation attempts from the left ventricle. Both patients had tachycardias with a left bundle branch block morphology and markedly presystolic activity recorded from the right ventricular septum. Right ventricular septal activation mapping during ventricular tachycardia should be performed in patients with left bundle branch block tachycardia morphology and coronary artery disease to maximize efficacy of the catheter ablation procedure.     

Right atrial isolation for atrial fibrillation associated with atrial septal defect

Two patients with atrial fibrillation associated with an atrial septal defect underwent simultaneous surgical correction of the atrial septal defect and right atrial isolation. The right atrium was surgically isolated while the continuity with the sinoatrial node was preserved in the remainder of the heart. After the operation, the patients maintained normal sinus rhythm for 99 and 65 months. Thus, right atrial isolation offers an alternative to the current surgical treatment for atrial fibrillation associated with an atrial septal defect.     

Exercise-induced T-wave normalization predicts recovery of regional contractile function after anterior myocardial infarction

AIMS: We investigated the ability of T-wave pseudonormalization and ST-segment elevation, which are demonstrated in infarct-related leads during submaximal exercise testing, to predict late recovery of contractile function. METHODS: We studied 88 consecutive patients (73 males, mean age 59 +/- 8 years) with anterior infarction, persistent T-wave inversion and a documented lesion of the proximal segment of the left anterior descending coronary artery. They all underwent 2D-echocardiography on admission, 4 weeks as well as 6 months after myocardial infarction to evaluate the dysfunction score and the ejection fraction. Submaximal (75% of maximal predicted heart rate) exercise testing was performed in 80 patients 2 weeks after myocardial infarction following discontinuation of treatment. RESULTS: During exercise testing, 59 of the 88 patients showing negative T-waves on the resting electrocardiogram exhibited pseudonormalization (group A) in at least three adjacent precordial leads, whilst 29 (group B) did not. Patients of group A more frequently exhibited an early creatine kinase peak (41% vs 24%, P < 0.05) and residual angiographic perfusion (97% vs 69%, P < 0.05). The dysfunction score did not change in group B (from 19 +/- 7 to 22 +/- 4), but decreased in group A (from 18 +/- 4 to 11 +/- 6 P < 0.05). The ejection fraction was similar in the two groups on admission (group A: 48 +/- 7%, group B: 45 +/- 10%), but was significantly different at 4-week (52 +/- 99 vs 42 +/- 11%, P < 0.05) and 6-month follow-up (58 +/- 9 vs 44 +/- 10%, P < 0.01). The concomitant presence of ST-segment elevation and T-wave normalization showed the highest positive predictive value for left ventricular function recovery (100%). CONCLUSIONS: T-wave normalization induced by submaximal exercise test is frequently associated with residual perfusion to the infarct area and predicts progressive improvement in regional wall motion, especially if associated with ST-segment elevation. Therefore, these electrocardiographic findings may be used as easily obtainable markers of residual viability that predict late recovery in contractile function.     

Withholding thrombolysis in patients with diabetes mellitus and acute myocardial infarction

The benefits of thrombolytic therapy in a patient with diabetes having a myocardial infarction are now well accepted but this treatment may be withheld inappropriately because of concerns about retinal haemorrhage. We therefore examined whether junior doctors alter their use of thrombolysis for the treatment of acute myocardial infarctions according to the type of diabetic retinopathy present. A questionnaire asking whether thrombolysis would be given to a 50-year-old male smoker with insulin-treated diabetes and an acute anterior MI was shown, with four unlabelled retinal photographs, to all doctors prescribing thrombolytic therapy in a south London teaching hospital and an affiliated district general hospital. In all, 24 medical SHOs, 16 medical registrars/specialist registrars, 3 medical senior registrars, and 23 casualty SHOs were interviewed. Of these 89% would thrombolyse such a patient with normal fundi, 55% with background diabetic retinopathy, 54 % if this also involved the macula, and 26% if they saw proliferative retinopathy. The more senior grades were more aggressive in their approach. As we believe that all patients with an acute anterior myocardial infarction and diabetes should be considered for thrombolysis irrespective of their retinal appearance these results suggest thrombolytic therapy is being withheld inappropriately.     

Seven-pinhole emission tomography with thallium-201 in patients with prior myocardial infarction

Thirty-six patients with prior myocardial infarction, and 14 patients without, had myocardial imaging at rest using both seven-pinhole emission tomography and planar imaging with thallium-201. The sensitivity and specificity of the two approaches for the detection of prior myocardial infarction were compared. Qualitatively, planar imaging yielded sensitivities of 69% (25 of 36) and 80% (29 of 36) with Polaroid and video display formats, respectively. A semiquantitative analysis gave a sensitivity of 75% (27 of 36). Specificities for these three planar approaches were, respectively, 100% (14 of 14), 93% (13 of 14), and 71% (10 of 14) for the Polaroid, video, and semiquantitative analyses. Seven-pinhole tomography had a sensitivity of 83% (30 of 36) by qualitative or visual inspection and 86% (31 of 36) by semiquantitative analysis. Specificities by these two techniques were 71% (10 of 14) and 57% (8 of 14). There were no statistically significant differences in either sensitivity or specificity between the planar and tomographic approaches. Repeat seven-pinhole images were identical in 95% (46 of 48) of patients, showing that reproducibility was satisfactory. We conclude that the seven-pinhole tomographic approach has no advantage over standard planar imaging in the detection of prior myocardial infarction.     

Correlation of mean pulmonary artery wedge pressure, left atrial dimention, and PTF-V1 in patients with acute myocardial infarction

The mean pulmonary artery wedge pressure (PAWP), left atrial dimension (LAD) by echocardiography, and PTF-V1 in the electrocardiogram were correlated with each other in 16 patients with acute myocardial infarction in the control period and after therapeutic intervention with either Dextran or furosemide and/or nitroprusside. No significant correlation was found between a normal control PAWP and the LAD. An increased control PAWP correlated well with an increased LAD (r = 0.98). No significant correlation was found between the LAD and the PAWP whether normal or elevated after therapeutic intervention. No significant correlation was found between the PAWP whether normal or elevated and the PTF-V1. No significant correlation was found between the LAD and the PTF-V1. We conclude in acute myocardial infarction 1) the PTF-V1 is not useful in assessing PAWP before or after therapeutic intervention, 2) the LAD correlates poorly with a normal control PAWP but correlates well with an elevated control PAWP, and 3) the LAD cannot be used to assess PAWP after therapeutic intervention.     

Antibodies to prothrombin crossreact with plasminogen in patients developing myocardial infarction

This study aimed to determine the differences in haemodynamic responses to a standard incremental exercise test between outpatients with chronic obstructive pulmonary disease (COPD) and age-matched controls and to discover the relationship between severity of airflow obstruction and exercise haemodynamics in COPD. Twenty-two male patients with COPD (forced expiratory volume in one second (FEV1)/vital capacity (VC))<80% predicted) and 20 age-matched male controls performed an incremental exercise test (10 W x min(-1)) with ventilatory function and changes in stroke volume (deltaSV) and cardiac output (deltaCO) measured by means of electrical impedance cardiography (EIC). Submaximal deltaSV and deltaCO were lower in COPD patients. Peak exercise deltaSV were equal in patients and controls (128+/-33 versus 129+/-29%, p=0.98), whereas peak deltaCO was lower in patients (COPD versus controls: 232+/-71 versus 289+/-54%, p<0.005). In COPD patients, FEV1 (% pred) was significantly correlated to deltaSV at all submaximal exercise intensities, to peak exercise deltaSV and to peak exercise deltaCO. FEV1/VC (% pred) was significantly correlated to deltaSV at 30 and 60 W. In conclusion, in chronic obstructive pulmonary disease an aberrant haemodynamic response to exercise was found, especially in patients with severe airflow obstruction. This aberrant response is related to the degree of airflow obstruction and may limit exercise performance in patients with severe chronic obstructive pulmonary disease.     

Varying thrombolytic administration rates in elderly patients with acute myocardial infarction

Receipt of thrombolytic therapy in patients aged 75 or over with proven acute myocardial infarction admitted initially to either the coronary care unit (CCU) or a geriatric medical ward (GMW) was studied retrospectively in a hospital administering thrombolysis only in the CCU. Mean age and age distribution of patients admitted to each unit initially showed no significant difference. Of 50 patients admitted directly to the CCU, 28 (56%) received thrombolysis, compared with 13 of 50 (26%) GMW admissions (P < 0.02). Of 37 GMW admissions, 14 (38%) failed to receive thrombolysis without documented contraindication compared with 2 of 22 (9%) CCU admissions (P < 0.05). Aspirin was administered in 39 (78%) CCU and 31 (62%) GMW admissions (P < 0.05). Non-administration of aspirin without apparent contraindication occurred in 3 of 11 (27%) compared with 8 of 19 (42%) GMW admissions (NS). Elderly patients thus failed to receive thrombolytic therapy as a result of initial admission to a unit unable to administer this treatment.     

Dobutamine-induced ST-segment elevation in patients without myocardial infarction

During dobutamine stress echocardiography, ST-segment elevation developed in 20 of 372 patients (5%) without previous myocardial infarction and was associated with a transient severe asynergy of the myocardial region corresponding to the site of ST elevation. In 17 of 19 patients, ST-segment elevation was associated with a critical stenosis of the ischemia-related coronary artery, whereas in 2 of 19 patients with no critical lesions of the ischemia-related artery, coronary vasospasm was the most likely mechanism of myocardial ischemia.     

The heart rate performance curve and left ventricular function during exercise in patients after myocardial infarction

PURPOSE: The aim of the study was to investigate the heart rate turn point (HRTP) in the time course of the heart rate performance curve (HRPC) in patients after myocardial infarction, and the relationship between the HRTP, the left ventricular function, and the second lactate turn point (LTP2). METHODS: We studied the degree and the direction of the HRPC and the left ventricular ejection fraction (LVEF) in 49 male patients 57 +/- 8 d after their first posterior wall infarction (MI). An incremental cycle ergometer test was performed and three phases of energy supply were defined (I: aerobic; II: aerobic-anaerobic transition; III: anaerobic) via blood lactate LA concentration. HRTP and LVEF-turn points (LVEFTP) were assessed by linear turn point analysis. The degree and direction of the deflection of HRPC were described as factor k (k > 0.1: downward deflection; -0.1 < k < 0.1: linear time curse; k < -0.1: upward deflection). The LVEF was determined by RNA. The difference between Pmax and LTP2 was calculated for LVEF (delta LVEF). RESULTS: An HRTP could be found in 44 and a LVEFTP in 47 cases. The HRTP occurred at 85 +/- 17 Watt (W), which correlated (r = 0.95; P < 0.001) with the LTP2 (84 +/- 17 W) and the LVEFTP (84 +/- 17 W, r = 0.93; P < 0.001). From LTP2 to Pmax a significant decrease in LVEF was found. There was a correlation between the percentage of HRmax at the HRTP and k (r = 0.70), as well as delta LVEF (r = 0.56). CONCLUSIONS: To prevent myocardial overloading, it seems to be useful to determine the HRTP, which indicate the workload where LVEF decreases.     

In-hospital and follow-up mortality of patients with acute myocardial infarction

Patients with definite acute MI who were admitted to Songkla University Hospital between 1982 and 1990 were studied. The 195 patients and 202 admissions were nearly equally distributed between these 65 and older versus those younger than 65. Three quarters were males. The in-hospital mortality was 19.5 per cent and 76.3 per cent of the deaths were from heart failure. Neither age nor gender determined the mortality once corrected for the Killip's staging. There was no difference in mortality when comparing Q versus non-Q MI, anterior versus inferior wall MI or males versus females. One hundred and thirty-eight patients could be followed for and average of 27.1 months. First year mortality was 11 per cent and the first 2 years was 14 per cent. The in-hospital mortality, representing the prethrombolytic era, appeared to be similar to values reported from the Thai and Western literature. The predominance of death from heart failure rather than from arrhythmia may be a consequence of delayed admission whence arrhythmic death had already occurred or patients will seek hospital advice only if highly symptomatic.     

Fatigue in women with myocardial infarction

This study measured fatigue in women 6 weeks after myocardial infarction. Fatigue was experienced by the women as chronic, generalized, intermittent, and longstanding. More than one third of the women attributed their fatigue directly to the heart attack or hospitalization. Significant relations were found between fatigue and the physiological dimension of the Sickness Impact Sale (SIP), the Perceived Health Assessment and Risk Protection Survey (PHARPS), and the site of infarction, as well as with the psychological dimension of the SIP. There was an inverse significant relation between fatigue scores and the Psychological General Well-Being (PGWB) Index. Although not reaching statistical significance, fatigue scores for women 65 and older were higher than for younger women.     

Inadequate control of lipid levels in patients with a previous myocardial infarction

AIM: To access the current lipid management of late survivors of acute myocardial infarction. METHODS: A systematic follow-up of all survivors who had previously been screened for enrolment into one of three randomised clinical trials in Auckland was undertaken from December 1995 to January 1997. All contacted survivors were asked to answer a questionnaire regarding their current therapy and were invited to undergo venepuncture for a lipid assay. RESULTS: Of the 1036 patients with acute myocardial infarction screened for enrolment in the three trials there were 984 (95%) who survived 30 days. At a median of 5.5 years (interquartile range 3.2-8.5) follow-up, 641 (86%) survivors agreed to have a fasting lipid test. The mean total cholesterol level was 5.7 +/- 1.1 mmol/L high density lipoprotein cholesterol 1.1 +/- 0.3 mmol/L, low density lipoprotein cholesterol 3.8 +/- 0.9 mmol/L and triglyceride level 1.9 +/- 1.1 mmol/L. Two hundred and seven (32%) patients were treated with a lipid-modifying agent. Four hundred and forty-five (69%) patients had a cholesterol level > or = 5.2 mmol/L 381 (59%) patients had a level > or = 5.5 mmol/L and 72 (11%) patients had a level > or = 7.0 mmol/L of whom 62 patients were not being treated with a lipid-modifying agent. For the 107 patients with coronary artery bypass grafts, the mean cholesterol level was 5.4 mmol/L and the mean low density lipoprotein cholesterol level was 3.7 +/- 0.9 mmol/L, with 57 (53%) patients not being treated with a "statin" or "fibrate". CONCLUSION: Lipid management is suboptimal in this high risk population of patients post-infarction and greater efforts need to be made to achieve better control. Diet is frequently inadequate in these patients at high risk and statin therapy is indicated.